Learn Digital Photography Now
Which is the best digital camera to buy A frequent question but one to which there is not one answer. It is equivalent to asking which telescope is best. Some telescopes are good for the planets, some are best for deep-sky. Others are optimized for portability, while some require an observatory. It is the same for digital cameras and the CCD chip at their heart. There is a further limitation in that the CCD should be optimized not only to the type of objects to be imaged but to the telescope as well. For many starting out in digital imaging who are asked what their target objects are, the answer is everything That makes choosing a single camera a little difficult, and some compromises will have to be made.
Full aperture filters make digital photography of the Sun possible. Place the eyepiece with camera attached back in the telescope. A focused image of the Sun should now appear on the viewing screen. Because of flexure in the system the telescope may have to be moved slightly to center the image. By using the zoom control on the camera, the image size can be adjusted until it nearly fills the screen. Take at least 10 photographs to be sure to get some good ones.
Be sure to cancel the flash mode on the camera. Set the camera to focus for infinity, shutter priority, ISO 100 and remote or self-timing. Although the Moon appears to be solely shades of gray, do not set the camera for black-and-white photography. You may lose some detail but you can change the image to black-and-white when you process it in your computer. For photographs of the Moon at low magnification, depending on the phase, use shutter speeds from 1 80 to 1 50 of a second. Then take several photographs at each of several increasing magnifications. For the highest, the shutter speed may be as long as V2 second with an 80-mm refractor. Take high magnification photographs of overlapping sections along the terminator. To be sure, it takes some experimenting and not a little patience to become familiar with the procedure for getting excellent photographs, but is well worth the effort.
Making measurements of the physical dimensions of a planet with small telescopes can be done more easily with digital photography than with a micrometer eyepiece. The micrometer requires experience, skill and a solidly stable telescope mount. Photographic prints can be measured in a warm room at your leisure. Measurable digital photographs of Jupiter, Saturn, Mars and Venus can be taken with an 80-mm refractor or 90-mm Maksutov using a camera with 3-megapixel or higher resolution. Although they won't reveal the rich detail of photos taken with larger instruments, they will provide enough information for some interesting activities. Figures 8.1 and 8.2 are representative photographs of Jupiter and Saturn taken with a 90-mm Maksutov telescope.
When Jupiter is near opposition digital photographs of it can be useful for some interesting activities. One of the visual characteristics of Jupiter is the apparent difference between its polar and equatorial diameters. This seeming flattening of the poles could be an optical illusion due to the vivid horizontal banding of clouds or it could be a true physical difference between the polar and equatorial dimensions. We can determine which by photographing the planet and measuring its equatorial and polar diameters.
This section summarizes techniques that lead to outstanding deep-sky images with a digital camera. Because these techniques are based on the fundamental properties of photon counting, sensor noise, and image statistics, they are valid with any and every digital camera. Shoot under Dark Skies. The darker your sky, the better your pictures will be. In the sensor of your digital camera, sky background photons increase the photon event count without adding useful image information, while adding to the statistical uncertainty of the photons from your deep-sky target object. Shoot with a Fast Optical System. Since noise sources like dark current increase with longer exposure times, using a fast optical system means delivering more photons to each pixel, and therefore less time required to get a fully exposed image. In the context of digital cameras, fast is a relative term. With a camera lens, f 2.8 is not particularly fast, but with a telescope, such a low focal ratio is virtually unheard...
The following pages (119-149) display all nebulae featured in The Observer's Sky Atlas . The photographs are taken from the Palomar Observatory Sky Survey II for the northern nebulae and from the United Kingdom Schmidt Telescope for the southern nebulae. All photographs were taken in red light, except for the following nebulae which were taken in red and near infrared light in order to avoid overexposure NGC 1931, M 57, NGC 1535, M 42, M 43, NGC 2024, NGC 2392, NGC 6369, M 11, M 20, M 8, M 16, M 17, NGC 2070, NGC 3132, and NGC 3372. The photographs featured here are sections from plates taken with long exposure times and with the largest Schmidt telescopes. Therefore, they display far more stars than visible in any amateur telescope. They do not at all represent the view in an eyepiece. Detail clearly displayed in the outer parts of many nebulae may never become visible in an eyepiece. On the other hand, the photographs do not show every detail an experienced observer will notice in a...
Because nebulae and galaxies are extended diffuse objects, with the exception of the bright nebula M42, the great nebula in Orion, digital photography with small telescopes will not reveal more than the eye can see. Common fixed lens digital cameras do not have sufficient noise reduction for the long exposures needed. Although digital single lens reflex cameras are available with ISO speeds of 800 or more, resolution of 6 to 8 megapixels and much longer low noise exposure times, we consider them too expensive to be used within the context of this book's intentions. Star clusters, however, consist of numerous point sources and a 30-second exposure with a fixed lens digital camera will reveal much more than the eye can see in the telescope. Figure 14.2, for example, is a 30-second exposure of the globular cluster M13 in Hercules obtained with an 80-mm f 6 refractor. Visually, in the telescope this cluster appears as a luminous, circular patch of light with no distinguishing features....
If your digital camera is not a DSLR, it has a smaller sensor with a higher noise level, making it unsuitable for deep-sky work. More importantly, it doesn't have interchangeable lenses. Those facts don't make it useless. Non-SLR digital cameras have one great advantage - their shutters are almost totally vibration-free. This enables them to get sharp images of the sun, moon, and planets (Figures A.1-A.3). In fact, a Nikon Coolpix 990 is my usual camera for photographing lunar eclipses. If you'd like to photograph the stars, try the same fixed-tripod or piggybacking techniques as with a DSLR (p. 40), but expect a lot of hot pixels, so take dark frames too. See p. 163 for how to process the images. You have one advantage over DSLR users - you don't have to hunt for infinity focus just turn off autofocus and lock your camera to the mountain symbol.
Palomar, SRC, and ESO sky surveys The true comprehensive charts of the faint stars in the sky at optical wavelengths are actually deep (i.e., sensitive) photographs of the sky. The first and most famous of these is the Palomar Observatory Sky Survey (POSS-I) carried out in the early 1950s. It consists of 936 pairs of large glass plates (350 mm x 350 mm) taken with the large Schmidt telescope at Palomar Mountain in California. The plates cover declinations +90 to -30. At each position, a red-sensitive and a blue-sensitive plate were exposed. The glass plate provides stability against bending and thermal expansion. Each plate covers a large portion of the sky, about 6.5 x 6.5 , and shows stars as faint as 21st magnitude. (The brightest stars have magnitude m 0, and the faintest stars visible to the naked eye on a dark night have magnitude m 6. See Section 8.3 for more.) The red and blue plates were taken with specific types of emulsion and filters. The developed plate is a black and...
In order to easily observe the changing position of Barnard's star, a large print scale and therefore a long focal length is necessary. An 80-mm f 11 refractor or 90-mm Maksutov is recommended for these photographs. Accurate polar alignment of the telescope is imperative. An 80-mm f 5 refractor can be used but it will take twice as long between photographs to detect appreciable motion in the star.
After you have downloaded them, select the best low power and high magnification photographs. Sharpen them and adjust the brightness and contrast to represent the moon as you see it visually in the telescope. Make a full-page print of each of the best. Figures 7.1 and 7.2 are examples of low and high magnification photographs taken with an 80-mm f 11 refractor using a 5-megapixel camera. Figure 7.1 was a 1 50 second exposure with a 20-mm eyepiece that has a 60 apparent field. For Figure 7.2, the camera was used at maximum zoom with a 9-mm, 66 apparent field eyepiece. The exposure time was 1 5 second. Use the high magnification photographs to measure vertical dimensions on the lunar surface. After bringing up the image, sharpen it and improve its brightness and contrast as needed. Use one of the craters already measured on low power to determine an image scale for the print. This will be equal to the crater diameter in kilometers divided by its diameter in millimeters. Measure the...
As in my Deep-Sky Companions The Messier Objects, all the photographs in this book are reproduced in black and white. The decision was not made merely to save money. While it's possible to see hints of color in some of the brighter star clusters, nebulae, and galaxies, such objects typically manifest themselves in shades of gray at the eyepiece. Color photographs of deep-sky objects may mislead beginners into thinking that they can expect to see vivid reds, greens, and blues, when they will not. most striking specimen. Its beak is yellow, its head a rose-tinted aquamarine, its body olive, its wings vibrant indigo, and its tail feathers squid-ink black. You must see it Now imagine the disappointment when you go birding with a friend, who points out the black raven. Shocked, you show your friend the photograph in your guidebook. Your friend laughs and tells you that that's a heavily enhanced image that exaggerates the iridescence of the bird's feathers. The point is, why risk...
The advent of two-dimensional solid state detectors has revolutionized 'photography'. The use of digital cameras for everyday use is now fairly common. Such equipment used for landscapes and portraits automatically provides colour pictures. Some of the latest models (SLR) have detachable lenses and could, in principle, be attached at the focus of a telescope without the camera lens being attached. However, there is no facility to make long exposures and, without cooling, the recorded pictures would be very subject to thermal noise. The formatting of the files is also generally not amenable to obtaining numerical information on brightness values. A 'landscape' digital camera could be used in a situation where the light level is sufficient as perhaps in the recording of solar spectra using the fibre optic spectrometer described earlier. Digital cameras can, however, be applied to photography of the Moon and bright planets. In order to obtain images of planetary disks with a reasonable...
Modern digital cameras are capable of producing amazing results, compared with 35-mm film cameras. I still have a beautifully built and once-valuable Nikon F2 camera and some of the best lenses and accessories made for it, but I haven't used it for years. I also own three digital cameras, including a Fujicolor Finepix S7000, which has entirely supplanted my old F2. Darkroom work on my F2 pictures was incredibly time-consuming, expensive, messy, and (in my case at least) prone to rather variable results. Processing digital photos on a PC is a joy in comparison, and all sorts of things are possible. The main problems with digital UFO photos today is that they are easy to fake, and even easier to mistake.
How to Use a Computerized Telescope is the first handbook that describes how to get your computerized telescope up and running, and how to embark on a program of observation. It explains in detail how the sky moves, how your telescope tracks it, and how to get the most out of any computerized telescope. Packed full of practical advice and tips for troubleshooting, it translates the manufacturers' technical jargon into easy-to-follow, step-by-step instructions, as well as including many of the author's tried and tested observing techniques. Early chapters explain how to test your telescope's optics, choose eyepieces and accessories, take pictures through your telescope, and diagnose operational problems. The second half of the book then gives detailed instructions for three classic telescopes the Meade LX200, Celestron NexStar 5 and 8, and Meade Autostar (ETX and LX90). Besides helping owners and would-be purchasers of these models, the instructions also provide a basis of comparison...
The key to enjoyment is to have realistic expectations and continue building your knowledge and skill. Looking through a telescope is a very different experience from looking at photographs in books, and it may take some getting used to. If you don't already have a telescope, get some experience looking through other people's telescopes before buying one of your own. Contact a local astronomy club if possible.
A common remote sensing device is some sort of camera, an early example of which was an instrument on Lunik 3 that photographed the far side of the Moon for the first time in 1959. Close-up photographs of the Moon were obtained with the Ranger spacecraft in the last minutes before they crashed onto the surface, and the whole Moon was surveyed from the Lunar Orbiter spacecraft in 1966 and 1967. Several Surveyor spacecraft landed on the Moon between 1966 and 1968 and obtained photographs from its surface, as well as probing the terrain with mechanical scoops (Figure 1.1). The exploration of the Moon in the 1960's culminated in the landing of astronauts, who conducted a range of investigations including the deployment of seismic detectors and laser ranging targets, and collecting rock and dust samples that were returned to the Earth for analysis. The results of this exploration, the Apollo programme, have, over the years, contributed greatly to our understanding of the Moon's origin, and...
Charge-coupled devices, or CCDs as we know them, are involved in many aspects of everyday life. Examples include video cameras for home use and those set up to automatically trap speeders on British highways, hospital X-ray imagers and high-speed oscilloscopes, and digital cameras used as quality control monitors. This book discusses these remarkable semiconductor devices and their many applications in modern day astronomy.
Recall that the main-sequence lifetime of a typical O star is of order 106 yr, only about 1 percent of the rotation period of a spiral arm. Thus spiral arms must produce, at each location in the disk, a temporary increase in gas density leading to a rise in the local star formation rate. Although stars of all mass are formed, it is the exceptionally bright O and B stars that are most conspicuous in optical photographs. Once the spiral wave has passed, the rate of forming new stars drops back down to its former low level.
The ability to observe the wonders of the universe is surely one of the greatest gifts from science to the layman. Much sophisticated equipment, once available only to the professional astronomer, has slowly entered the amateur's realm, and today the inclusion of advanced CCD technology has further revolutionized the possibilities. In seasoned and skilled hands, CCD equipment, along with an array of high quality telescopes, has made exquisite photographic images possible which equal or even surpass many great observatory photographs, even of the recent past. However, this leaves me thirsting all the more to see for myself, in real time, as many of those same sights as possible there is still no substitute for the moment itself. With the exception of the Solar System, what we witness is not likely to equal, or even approach, the incredible wealth of detail, brightness and resolution that modern imaging technology has brought about. However, the eye's and mind's unique response to faint...
Caroline Herschel shown in her 80s back in Hanover, where she returned after Sir William's death. In a letter to her nephew, Sir John Herschel, she said You will see what a solitary and useless life I have led these 17 years all owing to not finding Hanover, nor anyone in it, like what I left, when the best of brothers took me with him to England in August, 1772. Courtesy of the Royal Astronomical Society Science Photo Library, London. Fig. 1.4. Sir John Herschel seen in his prime. He not only extended his father's work in the northern skies over England, but also explored those of the southern heavens as well from Cape Town, South Africa, using Sir William's favorite telescope -the large 20-foot reflector (see Fig. 2.2). Courtesy of the Royal Astronomical Society Science Photo Library, London. Fig. 1.4. Sir John Herschel seen in his prime. He not only extended his father's work in the northern skies over England, but also explored those of the southern heavens as well from...
Most of the historical solar observations were made through telescopes, and the first observations were intermittent because the Sun could not be seen during night-time or overcast conditions. The first telescopes were situated at various locations, often chosen to be in the proximity of the enthusiast astronomer and not necessarily where visibility ( atmospheric seeing'') was best. Some observatories were also moved, or the telescopes improved. In 1858, some of the first operational photoheliographs (photographs of the Sun) were made at the Kew observatory near London, but the telescope was moved to Spain in 1860. The telescope was re-erected at Cranford8 in 1861 and moved to Greenwich in 1873, where the observations commenced in 1874 and have continued to the present day. photographs of the sunspot spectra at Mount Wilson (1906), and established that sunspots were cooler than the surrounding photosphere as opposed to being regions with higher absorptivity. They found certain line...
Even before the Clementine mission, examination of the Lunar Orbiter photography identified a number of large basins on the far side including the giant South Pole-Aitken Basin. Many of these basins are outlined in Figure 1.4, and are shown in great detail in photographs and images of this book. Now we knew more about both similarities and differences between the near side and the far side. Mysteries were resolved, but the new mystery was how the striking differences in the two sides of the Moon came about. g
You don't have to be online to view great images of Earth. A number of software packages include collections of Earth images with descriptive information. One example is the application Endeavour Views the Earth, published by the Excellence in Education project at the Space Telescope Science Institute. This package includes dozens of images taken in 1992 by the space shuttle Endeavour on its maiden mission, complete with information about what's visible, even pointing out specific features in the photographs, as shown in Figure 2.6. More information about this free software package (Macintosh and Windows) is at http marvel. stsci.edu exined-html endeavour.html.
In 1924, Hertzsprung noticed that one of the faint stars in Carina was brighter by 2m on one of the photographs taken on the night of January 29. The rate of brightness increase suggested that this star did not belong to novae or oscillating RR Lyrae-type stars. Thus, Hertzsprung decided that the effect could be produced by the fall of an asteroid on star. Apparently, it was the first recorded flare on stars of this type.
The accuracy with which the first radio sources were located in the sky was insufficient to allow optical astronomers to decide which of the hundreds or thousands of images of stars, galaxies, and nebulae in their photographs of the region in question was responsible for the radio emission. In order to make an optical identification the astronomers required an accuracy of 1 arcminute or less (Appendix A.6), although by the late 1940s and early 1950s half a dozen of the strongest radio sources had been identified with obviously unusual, and hence interesting, optical objects. Those included a couple of nebulae associated with the remains of exploded stars, and several distant galaxies.
The waves on the pond can be used to illustrate several other wave concepts. The stone hitting the water surface excites a group of waves, within which the surface profile is approximately sinusoidal. The line following a particular maximum of the wave (a growing circle in this case) is called a wavefront. The wavefront has a velocity called the wave or phase velocity this can be deduced by comparing figure 2.4(a) and (b) and measuring the distance that the wavefront has traveled in the time between the photographs. It also has a group velocity which is the distance traveled in unit time by the envelope of the group of waves excited by the stone. The group and wave velocities may not be equal in the case of water surface waves they are not, but for electromagnetic waves in free space the two velocities are equal.
The onboard cameras were equipped with 1500-mm focal length lenses to enable high-resolution pictures to be taken during both the approach and post encounter phases. During the first flyby (Figure 2-3), the closest approach of Mariner 10 to Mercury occurred when the cameras could not photograph its sunlit surface. The imaging sequence was initiated 7 days before the encounter with Mercury when about half of the illuminated disk was visible and the resolution was better than that achievable with Earth-based telescopes. Photography of the planet continued until some 30 min before closest approach, thereby providing a smoothly varying sequence of pictures of increasing resolution. Pictures with resolutions on the order of 2 to 4 km were obtained for both quadratures during M1. Resolution varied greatly, ranging from several hundred kilometers to approximately 100 m. Large-scale features observed at high resolution were used to extrapolate coverage over broad areas photographed at lower...
Two things were changing the amateur's world as the 1960s arrived light pollution and an interest in picture taking. The unchecked growth of the suburbs and the brightening of most astronomers' home skies meant more and more observers had to travel to get good views of the night sky. Also, quite a few of the more serious amateurs were trying to take pictures of what they saw. The average amateur's traditional instrument, the long-tubed Newtonian reflector, did not fit in well with either of these new realities. Long Newts were not easy to haul around to dark sites and often had to be rebuilt if not redesigned before they could be used for astrophotography.
As the first spacecraft to orbit Mars, Mariner 9 (above) put an end to ideas that it was just a cratered, Moon-like world. Its photographs revealed canyons, volcanoes, and dried-up riverbeds (right). As the first spacecraft to orbit Mars, Mariner 9 (above) put an end to ideas that it was just a cratered, Moon-like world. Its photographs revealed canyons, volcanoes, and dried-up riverbeds (right).
The week aloft enabled the two men to indulge in taking photographs of Earth. This mission had, according to oceanographer Bob Stevenson, given them an opportunity to photograph a virtually cloud-free China and one of their shots almost got them into diplomatic hot water after landing. ''Jack and Gordon were invited to China to speak to a huge audience in some auditorium,'' Stevenson said later, ''and they showed this picture of a lake. It was such a beautiful picture that they had it enlarged and matted and framed and they signed it off to the Premier of China as a gift . When they got to this picture, there was silence. When the talk was over, there was subdued clapping and they didn't know what to think about this. So they turned to the US ambassador and said 'We want to give the picture to the Premier', and he grabs the picture, looks at it and says 'I think let's hold this for a while'. When they were leaving the stage, they said 'What's the problem ' The ambassador replied...
Colour photographs from the Nazi era grimly capture the reality of life and work beneath the mountain at Nordhausen. Up to 10,000 forced labourers worked underground in the factory at its peak, helping to produce not only the V-2, but also the V-1. Many of the workers died of pneumonia in the cold, damp conditions. Colour photographs from the Nazi era grimly capture the reality of life and work beneath the mountain at Nordhausen. Up to 10,000 forced labourers worked underground in the factory at its peak, helping to produce not only the V-2, but also the V-1. Many of the workers died of pneumonia in the cold, damp conditions.
Digital SLRs have the same vibration problem since the shutter works the same way. For that reason, DSLRs are not ideal for lunar and planetary work. Non-SLR digital cameras, with their tiny, vibration-free leaf shutters, work much better, though they aren't suitable for any kind of deep-sky work because of their tiny, noisy sensors.
The large-scale distribution of the various components of the interstellar medium is best studied in external galaxies, which can readily be seen as a whole. Photographs of M31, the closest spiral galaxy, show that bright young O stars, the emitting H II regions that surround them, and the dust clouds which obscure starlight generally are all concentrated within the spiral arms. Figure 1.4, photographed with an Ha filter 12 , shows conspicuous H II regions along a spiral arm in M31. Between the arms in spiral galaxies there appears to be no conspicuous obscuration nor emission nebulosity. Probably the neutral hydrogen and helium are also concentrated to the spiral arms, although the resolution of most 21-cm H-line surveys is too low to verify this. Since the O stars responsible for the brighter H II regions cannot shine for more than about 106 years, photographs such as Fig. 1.4 are generally taken as evidence that formation of these massive stars occurs in the relatively dense...
To get the most out of your camera equipment, it is necessary to have the proper supporting equipment. The devices used for 35-mm photography and for CCD imaging are very different from each other so we'll discuss them separately. In photography, 35-mm cameras cannot be directly connected to a telescope so adapter equipment will be necessary in order to make the mechanical connection. The minimum that you will need is a T-ring and a T-adapter. The T-ring is a metal ring with two threads. One screws into your camera and provides the interface for the T-adapter which screws into the other end. At the far end of the T-adapter is a universal thread ring that will mate to the rear cell of a Schmidt-Cassegrain telescope in place of its visual back. These two devices allow the camera to be mounted at the prime focus of the telescope and allow for photography at the telescopes normal f-ratio (for me, f 10). Photography using this type of setup is therefore called prime focus imaging. This...
Using telescopes of greater aperture and higher optical quality to get higher resolution and clearer views is always going to achieve better results. So, for the final word on white light viewing, I will let Larry's photos speak for themselves (see Figures 1.4-1.9). Note that these photographs have been taken using advanced equipments and techniques and cannot be matched with entry-level telescopes and domestic digital cameras.
Figure 1.12 The solar corona after solar activity minimum (left panel) and near solar activity maximum (right panel). The images are composites of eclipse photographs taken respectively in Guadeloupe on 26 February 1998 (left, obs. C. Viladrich) and in Angola on 21 June 2001 (right, obs. J. Mouette), and nearly simultaneously from the LASCO-C2 coronagraph on the spacecraft SoHO (ESA and NASA). (Composites by Institut d'Astrophysique de Paris - CNRS by courtesy of S. Koutchmy.) Figure 1.12 The solar corona after solar activity minimum (left panel) and near solar activity maximum (right panel). The images are composites of eclipse photographs taken respectively in Guadeloupe on 26 February 1998 (left, obs. C. Viladrich) and in Angola on 21 June 2001 (right, obs. J. Mouette), and nearly simultaneously from the LASCO-C2 coronagraph on the spacecraft SoHO (ESA and NASA). (Composites by Institut d'Astrophysique de Paris - CNRS by courtesy of S. Koutchmy.)
Of course, there are good reasons not to ignore the software CD that comes with your camera. It contains drivers that you must install if you want to connect the camera to the computer, either for remote control or to download pictures. Also, there will be utilities to convert raw files to other formats and perform some basic manipulations. Even if you don't plan to use them, some astronomical software packages will require you to install these utilities so that DLLs (dynamic link libraries) supplied by the camera manufacturer will be present for their own software to use.
By late March, she had been flown 'piggyback' on top of the modified 747 aircraft to KSC and ensconced in one of two bays in the OPF. The latter is positively dwarfed by the immense VAB and is still used to prepare the Shuttle fleet for their missions, to repair and refurbish them and to install and remove their payloads. It is, however, far more than just a spacecraft hangar due to the extreme volatility of the propellants carried on board the Shuttle, the OPF is fitted with detectors that are so sensitive to explosions that visitors are forbidden from using camera flashes when taking photographs.
Photographs, in particular, give the impression of very high star densities in globular clusters. In reality, however, there are between 10 and 1000 stars per cubic light-year at their centers - which means that the average distance between stars is still 0.1 to 0.5 light-years. Only
In the same way a large telescope can collect and focus light more effectively and therefore help us to see things that the human eye cannot see. Thus, by exposing a photographic plate to the light coming through a telescope for several hours, the astronomer is able to get photographs of faint nebulae which are otherwise invisible to the human eye.
As far as I am aware, I was the first to determine accurately the thickness of auroral curtains. The corona-type aurora is observed when an auroral curtain is located near the magnetic zenith. In some of the aurora photographs I took, the bottom edge of the curtain was clearly captured.
Within a very short time you will have accumulated thousands of photographs and it is vital to have some way of finding on your computer particular events or individual pictures and details associated with them. As each picture is taken, many cameras automatically record the properties such as shutter and film equivalent speed but you must set the clock time yourself initially to be able to retrieve the exact time each photograph was taken - very important for discussions and interpretation possibly many weeks, months or years later. Perhaps store each session's viewing under a separate computer folder labelled with the date and maybe some notes typed into individual picture files. Hours of time could be wasted without at least some order to your system.
Remember that at the very beginning of this book I mentioned that one of the greatest misconceptions about astronomy is that it is a source of instant gratification. You cannot simply expect to look through the eyepiece of an amateur telescope, even a big one, or even an observatory class telescope and expect to see what shows up on those awesome photographs. All those beautiful galaxies that show up as swirling gorgeous pinwheels on photographs only show faint gray-green blobs in the eyepiece. So how can I see what is in those pictures
Field meters, spectrometers and radiometers, radio-astronomy detectors and optical cameras. Excluding power and propulsion, the estimated mass of the TAU probe was 1,200 kg. Estimated data transmission rates were in the region of 10 kilobits per second. Astrometric photographs of distant galactic objects could be transferred to Earth at the rate of several images per day.
The most obvious way to record observations is by photography. Even a simple domestic digital camera is capable of recording many of the sunspots. However, a lot of my white light solar viewing is undertaken under poor conditions, where any photograph could show more cloud than solar surface. As I have also found out with lunar and planetary photography, trying to take shots in gaps between fast moving clouds is tricky to say the least. Whilst drawing is good for making good records of what I can see through binoculars or small telescopes, it starts to get difficult when using larger instruments, with more precision, such as my 127-mm Maksutov. More umbral penumbral shadings are visible, as are faculae. Here, using digital photography is recommended, but there have been many good drawings made of the Moon and close-ups of lunar features by amateurs. Drawing certainly is not one of my skills, but I certainly would not discourage anyone from having a go. One technique where there is a...
Astronomers must be able to refer to a given star or other celestial object after studying it. This can be done with the star coordinates or with a name. Our knowledge of the existence of the fainter stars in the optical sky derives from surveys of the sky, such as a series of large-area photographs or the counting rate data from an x-ray detector that scans the entire sky. Such surveys typically yield the celestial coordinate of each located object. Interesting objects of a given type that are found in such surveys can be plotted on maps of the sky (charts) or listed with positions and other information in printed catalogs.
The telescope itself is not all you have to check on. You will also have a box full of cameras, eyepieces and filters. The most important thing you can do is make sure that it is all organized You are going to have to be able to find absolutely everything in the dark, without the use of anything brighter than your red map light. All your eyepieces should be stored in order from longest focal length to shortest. Barlows should be stored together near the eyepieces. Filters should also be all together and stored in spectral order with blue or violet at one end and red and orange at the other end. The other side of your box should be dedicated to your cameras. Lenses are stored in order of focal length and other accessories should be close by such as cable releases. If you find yourself fumbling for equipment in the dark, you may as well not have it if you can't find it. Even worse, not being able to find equipment is an invitation to lose it. Cameras can also give you a surprise...
In fact no Earth-based optical telescope will show surface details all that can be made out are vague, impermanent, cloudy features. Neither is conventional photography more helpful, but in 1923 F. E. Ross, at Mount Wilson, took good photographs at infra-red and ultra-violet wavelengths. The infra-red pictures showed no detail, but vague features were shown in ultra-violet, indicating high-altitude cloud phenomena.
Vastness and beauty of space, as seen from photographs of the Hubble space telescope. Pictured are the stars which have fascinated humankind since the dawn of time. And to think that humanity has begun the long journey among these celestial points of light that beautify our nights, inspiring us to dream beyond our home planet. Ad Astra Source NASA JPL, Pasadena, CA. Exhibit 20. Vastness and beauty of space, as seen from photographs of the Hubble space telescope. Pictured are the stars which have fascinated humankind since the dawn of time. And to think that humanity has begun the long journey among these celestial points of light that beautify our nights, inspiring us to dream beyond our home planet. Ad Astra Source NASA JPL, Pasadena, CA.
When a repair is completed, it is useful to take pictures of the finished work. These are typically referred to as close-out images. They allow the crew to evaluate their work after they are back inside. If they determine that additional work needs to be done based on this analysis, plans can be made for an additional EVA or resupply of parts as appropriate. Figure 4.4. AERcam-Sprint. The ball in the left panel is a robotic camera designed to float about a space shuttle and the International Space Station and take pictures. The right panel shows a model of AERcam-Sprint in use in the Shuttle payload bay. AERcam-Sprint is NASA's first Autonomous Extra-vehicular activity Robotic Camera (AERCam). Figure 4.4. AERcam-Sprint. The ball in the left panel is a robotic camera designed to float about a space shuttle and the International Space Station and take pictures. The right panel shows a model of AERcam-Sprint in use in the Shuttle payload bay. AERcam-Sprint is NASA's first Autonomous...
Somewhat-lighter Strategic Reconnaissance Satellite, known as 'SRS'. Still more civilian sources speculated that the satellite, whatever it might have been, was capable of manoeuvring itself to an orbital altitude of about 480 km, from which vantage point it could take photographs with a resolution as fine as a metre. Certainly, it was not - unlike the huge Lacrosse radar-imaging satellite placed into orbit by Hoot Gibson's STS-27 crew in December 1988 - deployed with assistance from the RMS, which apparently was not carried on STS-28. The first photographs of what an SDS-B looked like were not actually made public until the spring of 1998, almost a full decade later, when the National Reconnaissance Office released pictures and videotapes of two military satellites. One was identified as an SDS-B, built by Hughes, and looked physically similar to the drum-shaped Intelsat-VI series of communications satellites.
''So when we came down and I flared the orbiter, I didn't know how high we were. Looking at the photographs, we weren't very high, but I basically levelled the vehicle off and then it floated. So instead of landing at 195 knots, the way we were supposed to, we landed at 155. This was Columbia again and so here we are on the main gear, decelerating fast and I've got to get the nose on the ground. The same thing that happened to John Young on STS-9 happened to me and the nose went 'bam' on the ground. I felt terrible because I let the thing float for 40 knots' worth of deceleration. We got a lot of great data about low-speed flying qualities on the orbiter, but it wasn't supposed to work out that way.''
Naturally, if there is no lens attached, or if the camera is attached to something whose aperture it cannot control (such as a telescope), the camera will not let you set the aperture. You can still take pictures the computer inside the camera just doesn't know what the aperture is.
Cameras are usually pretty easy to deal with. The best advice to give with photographic equipment is to keep all lens covers in place and the camera itself inside its protective case when it is not in use. Camera lenses do occasionally need to be cleaned and when you do so, you should give them the same level of detail as you do your telescope lenses. For loose dust, use compressed air to get the surfaces clean unless more forceful techniques are required. Pay attention to the camera's viewfinder mirror too. Since you will be frequently be removing the lens of the camera, you will be exposing the interior of the camera to dust and dirt far more frequently than the average user will. If the mirror becomes dirty or smeared, it will inhibit the ability of your telescope and eyes to sight faint objects through it. Faint nebulae may even disappear behind that smear. Take care to ensure that the interior workings of the camera also remain dust free. Similar advice must also apply to users...
Digital cameras offer an attractive alternative to the astronomical CCD camera. Not only are they far less expensive (on a cost-per-megapixel basis), but they produce color images without the hassle of shooting separate filtered images. Digital SLRs offer the added advantage of being easy to use with a wide range of standard camera lenses, as well with telescopes. The greatest drawback from the standpoint of astronomical imaging with standard off-the-shelf digital SLRs is the integral color-balancing filter. This filter blocks the infrared and severely attenuates red light however, special astronomical versions of digital SLRs are available without the filter. Because of the color-balancing and the integral Bayer array filters, pixels on the sensor receive only 10 to 20 of incident light, so to achieve the same signal-to-noise ratio as a cooled and unfiltered astronomical CCD camera, an off-the-shelf digital camera requires 25 times the exposure as the astronomical CCD. This means...
For visual observations and digital photography of variable stars, comets, asteroids and star clusters, a short focal length refractor is more useful than an f 11. With a 25-mm Plossl eyepiece an 80-mm f 5 refractor will provide a field of view in excess of 3 . All of the pictures of variable stars, asteroids and star clusters in this book were taken with that type of telescope.
During STS-32, this 'L-cubed' instrument was used by crew members to take repeat photographs of a geographical feature every 15 seconds the data was then fed into an onboard computer, which calculated two possible sets of latitudinal and longitudinal coordinates. The crew, by knowing whether the target was 'north' or 'south' of their flight path, could then determine which set was correct. The instrument, which utilised a modified Hasselblad large-format camera with a wide-angle lens, proved extremely successful.
The only way to study the Sun from the Earth is by examining the solar quantities that reach us, which includes particles, magnetic fields, and electromagnetic radiation. In addition, the action of the Sun's gravity on other bodies in our solar systems may be used to infer the solar mass. There is a great deal to learn from the electromagnetic radiation. The visible light and its directional variation is the foremost source of information on what happens on the Sun. It is through the visible light that we can see the Sun directly with our own eyes1 or by photographs.
The last critical task to be performed is the precision polar alignment. As soon as Polaris begins to come into view, I will rotate the telescope to 90 degrees declination and sight through the finder scope. In addition to a crosshair sight, the scope also has a dual ring to allow for precision positioning of Polaris. A template provided with the telescope shows exactly where Polaris should appear on the ring. With the telescope already aligned within a degree of the correct position, only some minor repositioning of the mount is required to gain a precise alignment. With this accomplished, it is not necessary to guide the scope during longexposure photography on the declination axis. The only corrections that will be required will be in right ascension to account for the occasional variations in the accuracy of the telescope's gears. My scope uses a Byers designed worm gear that for the time was the most accurate clock drive ever produced for a telescope. Even by the standards of...
There was still a most important duty to perform before closing out EVA-1, which was to plant the American flag and take the requisite photographs. The Hadley-Apennine region proved most photogenic. The color photo taken by Irwin of Scott saluting the flag, with the Lunar Module Falcon, the Lunar Rover and Hadley Delta looming in the background, has become an icon of Apollo photography. This photo
With its vast dimensions alone (being so close to us in space at a mere 2.3 million light years ), this object is one of the most imposing available to us (Figure 7.2). Surprisingly, in the telescope, it may at first prove to be a major disappointment how could something so huge and bright still reveal so little of its true nature to us While it is unfortunate that much of our first reaction is well founded, once we realize that it is not going to reveal itself fully to us in real time (particularly from our city locations), there are nevertheless numerous features to explore. With experience, you may be able to discern something of the large dust lane between its core and spiral arms, and possibly the bright southern star cloud so evident on photographs. If you arm yourself with a detailed chart, you also may be able to detect some of the globular clusters that encircle the galaxy, Figure 7.2. NGC 224 (M31) a the nucleus of the galaxy video frame intensifier. b This image...
Like all electronic devices, the sensor in your camera emits some heat while it's being used. As the sensor warms up, its noise level increases, leading to more speckles in your pictures. This effect is usually slight and, in my experience, often unnoticeable it is counteracted by the fact that the temperature of the air is usually falling as the night wears on.
The brightest members of this crowded field are captured in Fig. 2.7, an infrared photograph of unprecedented clarity produced recently with the 8.2-meter VLT YEPUN telescope at the European Southern Observatory in Paranal, Chile.5 The image we see here is sharp because of a technique known as adaptive optics, in which a mirror in the telescope moves constantly to correct for the effects of turbulence in the Earth's atmosphere. This motion of the air produces a twinkle in far-away objects and distorts and blurs their appearance on photographs such as this. Adaptive optics can in principle create images with a clarity that is even greater than that of the Hubble Space Telescope, whose primary mirror has an aperture three times smaller than that of the VLT YEPUN.
Another geologically unique feature on Mars is its sand dunes, which are found in many different areas of the planet. The most common types are crescent-shaped barchan dunes and steep ridges of sand known as transverse dunes. Photographs have also shown Martian dunes in unusual shapes that people have likened to sharks' teeth, fish scales, chocolate candy kisses, or horseshoe crabs. A particularly interesting photo taken by a spacecraft during the summer of 2003 showed what looked like entire fields of fortune cookies made of sand. These odd shapes are created by the direction and strength of the Martian winds, which also influence the size of the dunes. Some are small sand hills, while others stretch more than three hundred feet into the Martian sky. Their color can vary, but most dunes on Mars are dark because of the color of the minerals that make up Martian sand.
A CCD (charge-coupled device) is a small, flat chip - about the diameter of a match head in most digital cameras - made up of an array of tiny light-sensitive pixels. CCD chips in low-end digicams, including those featured in a number of PDAs, may have an array of 640 x 480 pixels a more expensive digicam may have a 2240 x 1680 pixel CCD chip (around 4 megapixels), while a high-end digicam may boast a chip of more than 8 megapixels. When light hits a CCD pixel it is converted into an electrical signal whose intensity corresponds with the brightness of the light that struck it. This information is then processed into an image and stored in the camera's own flash memory or on a removable flash card. Most low-end digital cameras have a fixed optical system, with non-removable lenses, and some may not even have an LCD display. Astronomical photography through these cameras must be done afocally, by aligning the digicam lens with the telescope's eyepiece (Figure 2.34). the same amount of...
Hubble classification System for classifying galaxies according to their shape on photographs it was introduced by Edwin hubble in 1925, with extensions and revisions by several later workers, including Allan sandage, Gerard de vaucouleurs, and Sidney Van den Bergh (1929-). While the Hubble classification was originally designed to be descriptive, and based on blue-light photographs of a particular exposure range, it has retained enormous utility because these designations correlate well with physically interesting galaxy properties. Stellar and gas content and star formation rate, for example, change systematically between Hubble types.
Our extraterrestrial human experience to date proves that steps can be taken to improve crew efficiency, ranging from automation and environment control systems, to exercising and scheduling alterations. In 1987, some of this accumulated information benefited two Soviet cosmonauts on their Soyuz TM-2 TM-3 missions. Alek-sander Aleksandrov stayed in orbit for 160 days, and his companion, Yuri Romanenko, spent 326 days aloft. During this time, Romanenko grew one centimeter taller and lost 1.6 kg of body weight, and experienced fatigue, listlessness, and homesickness during his long flight. In December 1988, cosmonauts Vladimir Titov and Musa Manarov spent over a year in space on the Mir station, returning in the Soyuz TM-6 capsule with their three-week visitor, Frenchman Jean-Loup Chretien. Radio Moscow reported that immediate medical check-ups on landing showed them feeling well, and subsequent physical evaluation of the two spacefarers at Star City revealed no serious difficulties...
The first, and still most widely used, astronomical telescope detector system is the human eye. With a relatively small aperture, and able to detect light only in the visible part of the spectrum (400-700 nm), the human eye has serious limitations. In this chapter so far we have described the techniques and telescopes that have enhanced our ability to see the universe. We now turn to the latest revolutionary detectors and other technologies that have improved that view. These include imaging devices such as charge-coupled devices, or CCDs, now commonly found in digital cameras, new radio-frequency detectors such as bolometers, bolometer arrays, and hot electron bolometer mixers, and techniques now enabled by such technological advances as mul-tiobject spectroscopy.
Photographs showing examples of CCD wafer layouts for (left) 100 mm wafer and (right) SNAP version-0 CCD on 150 mm wafer. Figure 2. Photographs showing examples of CCD wafer layouts for (left) 100 mm wafer and (right) SNAP version-0 CCD on 150 mm wafer. Figure 4. Wafer photographs showing (a) SNAP version-1 and (b) version-2 CCDs. Figure 4. Wafer photographs showing (a) SNAP version-1 and (b) version-2 CCDs.
On-orbit performance research. The onboard scenes shown in these photographs are of physiology experiments investigating microgravity conditions aboard the Shuttle Orbiter. For example, in one, astronaut-physician Dr. Rhea Seddon, on the bicycle or ergometer, breathes into the cardiovascular unit during an STS-40 spaceflight In 1993, during the 10-day STS-55 10-day Spacelab D-2 mission on Columbia, Dr. Bernard Harris, an African American physician, draws blood from Hans Schlegel, a payload specialist from the German Aerospace Research Establishment (DLR). Source NASA Johnson Space Center.
In the late 1970s advances in semiconductor technology allowed the manufacture of light-sensitive imaging detectors known as chargecoupled devices. They came into widespread use in astronomy during the 1980s, and recent advances have expanded their employment in commercial applications. The same detecting devices now found in consumer digital cameras and video cameras are located at the focal point of most of the world's research telescopes. The CCD is a grid of light-sensitive elements (called pixels), each of which records the detection of a photon by emitting an electron as a result of the photoelectric effect. The electrons that pile up in a given pixel are eventually read out of the CCD and recorded on a computer. Each pixel then has an electron count that is directly proportional to the number of photons that struck it.
Years ago, I was seldom able even to locate it, but patience and persistence will be found to be a virtue with this object, and on unusually clear nights it may astound you. In such conditions, and using a narrowband filter, the resemblance to well-known photographs is unmistakable, and I have been able to discern surprising amounts of the fine outer tendrils that the Crab is famous for. It can be seen somewhat more vaguely with intensification, but interestingly, much more successfully via video monitor than with direct viewing the video frame here seems quite remarkable to me, especially since the famous neutron star at its center is quite evident. However, because of its low inherent brightness, it remains a challenge to be easily certain of its exact outline, all the more so when trying to draw it. Pick your night carefully, and be patient.
The crew also tended a variety of other experiments. A Canadian-provided Spectrophotometer measured the light-absorption characteristics of Earth's atmosphere, while MacLean took photographs of the Shuttle's tail and flight surfaces during thruster firings in an effort to better understand the mysterious atomic oxygen-induced 'glow' around spacecraft. Heat pipes were tested as part of efforts to develop lighter, more efficient thermal-control systems for future spin-stabilised
Rather than the afocal method through the telescope, a wider field can be realized with a digital camera by using a telephoto conversion lens. These lenses screw into the filter adapters of many digital camera models. The camera is then mounted piggyback on the telescope as shown in Figure 5.3. Most of these lenses increase the focal length of the fixed camera lens by a factor of two. A typical digital camera lens has a focal length of around 24 mm when zoomed to 3x. A telephoto conversion lens will produce an effective focal length of 48 mm. With a 7.2 x 5.3 mm detector the resulting field width is 8.6 . This is equivalent to a 232-mm telephoto lens on a 35-mm film camera. The limiting photographic magnitude for a 30-second exposure with these conversion lenses Figure 5.3. A digital camera with a telephoto adapter mounted on an 80-mm f 5 refractor. Figure 5.3. A digital camera with a telephoto adapter mounted on an 80-mm f 5 refractor. is about eight. They are good for taking wide...
An American astronaut selected by NASA to fly on the first Apollo manned mission. Unfortunately, Chaffee never got the chance. He died on January 27, 1967, along with crewmates Gus Grissom and Edward White, during a launch pad test at the Kennedy Space Center. Chaffee received a B.S. in aeronautical engineering from Purdue University in 1957 and immediately joined the Navy. Photographs taken while he piloted a U-2 spy plane in 1963 proved conclusively that the Soviet Union had installed offensive missiles in Cuba and were displayed by President Kennedy during a televised address. That same month, Chaffee was selected by NASA as a member of its third group of astronauts. He was assigned with Grissom and White to fly the first Apollo capsule on an 11-day mission in Earth orbit. However, a month before their scheduled launch, all three were killed aboard their capsule during a countdown rehearsal, when a flash fire raced through their cabin.
Francisco State University, the University of Florida and Wesleyan University. It is the latest incarnation of the first research telescope on Kitt Peak, which began operation in 1962. It is used most often with the Mosaic camera, which gives it a one-degree field of view. Using this camera it is possible to study very extended objects, like clusters of galaxies, as well as regions of our Galaxy where stars are actively forming. It can also take pictures of nearby galaxies which otherwise would be too large to fit in a single image.
In the modern era Venus has also been observed at wavelengths outside the visible spectrum. The cloud features were discovered with certainty in 1927-28 in ultraviolet photographs. The first studies of the infrared spectrum of Venus, in 1932, showed that its atmosphere is composed primarily of carbon dioxide. Subsequent infrared observations revealed further details about the composition of both the atmosphere and the clouds. Observations in the microwave portion of the spectrum, beginning in earnest in the late 1950s and early '60s, provided the first evidence of the extremely high surface temperatures on the planet and prompted the study of the greenhouse effect as a means of producing these temperatures. Since the Copernican revolution of the 16th century, at which time the Polish astronomer Nicolaus Copernicus proposed a Sun-centred model of the universe, enlightened thinkers have regarded Earth as a planet like the others of the solar system. Concurrent sea voyages provided...
In April 1990, NASA launched the Hubble Space Telescope from the Shuttle's payload bay into an orbit about 600 kilometers above the Earth. Weighing as much as two adult elephants, the spacecraft has already completed about 93,000 trips around our planet, producing an unprecedented three-quarters of a million photographs of 24,000 celestial objects and phenomena. John Grunsfeld of the Space Telescope Science Institute, command center for the orbiting observatory, said that
Modern space cameras work just like digital cameras that, on Earth, are now becoming more popular than film cameras. The captured light of an image falls directly on a sensor and is immediately digitally encoded. There is no longer a need for film or line-by-line scanning.
Although Colima had not erupted since 1913, the imagery suggested that it had experienced a number of smaller, 'quieter' upheavals since that time. Columbia's crew also supplemented the MOMS-2 data with their own photographs, taken from hand-held Hasselblad and Linhof large-format cameras, which featured the redistribution of ash from Lascar Volcano in the Altiplano of Chile. This volcano had erupted on 20 April 1993, only six days before the Shuttle lifted off, and the photographs clearly picked up several plumes of wind-blown material.
These came supplied with my Skywatcher 127-mm Maksutov. It was at a star party that I decided that they did not get the best out of a very good telescope. After buying some Skywatcher Plossls (see below), they were consigned to the accessory case, never to see the light of the day again. That was until a chance observation. Before I bought the Plossls, I was able to photograph sunspots but was not afterwards. I soon realized that these eyepieces did have a use, for simple photography using a digital camera. The 50 field of view is not exactly excellent, especially compared to the Moonfish Group eyepieces, but it is good for whole solar disc shots. The table below shows how the eyepieces perform with the PST.
Galileo's first astronomical observations demonstrated how even a small telescope can exceed the capabilities of the human eye in many respects. The telescope collects much more light than the eye. This makes it possible to see much fainter objects than by the naked eye. For example, Galileo saw in the direction of the Pleiades 36 stars instead of the usual 6. Photographs by modern telescopes show hundreds of stars in this stellar group. The big lens also makes resolution much better. This means that while two close-by stars are seen as one dot of light by the naked eye, the telescope shows them as separate. The ability to collect more light than the eye and the improved resolution allow one to see much more structure and fainter objects in the starry sky. The improved resolution also makes the measurements of stellar positions (their coordinates) more accurate. This proved crucial for the determination of stellar distances as we will discuss in Chap. 8.2
Lunar Orbiter missions 4 and 5 covered the region of this chapter with a series of oblique photographs. They show a different view of the features than that shown in the .o Clementine images. The Lunar Orbiter photos cover the eg latitude range from 30 south to 60 south. As with the * Clementine images, the latitude parallels and longitude ola meridians are marked on one copy of each photo, along h P with the named craters. An unmarked photo is provided uth to show the topography clearly. The photos shown are i L02-033M, L02-075M, LO4-008M, LO5-021M, LO5-065M, JS and LO5-043M.
Such a massive telescope embedded in the earth's crust has one major flaw It cannot be aimed by rotating or tipping the dish. To resolve this problem, astrophysicists realized they would need to aim the telescope by moving the feed rather than the dish. The feed at Arecibo, which is suspended 450 feet above the dish, hangs in midair on eighteen cables. It is a bow-shaped structure 328 feet long that can be moved side to side and positioned anywhere up to twenty degrees from the vertical to focus on objects in deep space. Aiming the feed at a certain point above the dish enables radio emissions originating from a very small area of the sky in line with the feed to be accurately focused, thereby producing superb photographs.
When we look at photographs of the Milky Way (see Fig. 16.1), we note large regions where no light is seen. We think that these are due to dust blocking the light between us and the stars. We can see the same effect on a smaller scale (Fig. 14.1). Note that there is a high density of stars near the edges of the image. As one moves close to the center, the density of stars declines sharply. Near the center, no stars can be seen. This apparent hole in the distribution of stars is really caused by a small dust cloud, called a globule. The more dust there is in the globule, the fewer background stars we can see through the globule. We can use images like this to trace out the interstellar dust. We find that it is not uniformly distributed. Rather, it is mostly confined to concentrations or interstellar clouds.
Let us go a bit deeper into the key steps of the astronomical imaging process by first considering how best to remove the thermal component from the raw image. The thermal signal, also called the dark signal or current, is an artifact due to the spontaneous generation of electrical charges within the sensor itself, triggered by temperature. Despite considerable progress over the last decade in sensor technology (MPP technology, for instance) the thermal signal is still significant in deep-sky imaging, where the exposure duration is generally quite long. In some circumstances images can be taken with a noncooled device, which is the case with a digital camera. The issue of the elimination of the dark signal is tricky because it is not usually a constant, as temperature could have varied from one exposure to the next. Under these circumstances, if a unique dark image, acquired in darkness with the same exposure length, is subtracted from all the images, the result will not be reliable....
For a long time, some people thought there might be life on Mars. When two U.S. spacecraft landed on the planet in 1976, they sent back photographs of Mars and did experiments to find out If life exists there. Scientists now believe thot Mars does not have plant or animal life like that on Earth. 3. Two U.S. spacecraft landed on Mars In_, sent back photographs.
Since the Sun's X-ray radiation is totally absorbed in the Earth's atmosphere, it must be observed with telescopes lofted into space by rockets or in satellites. Herbert Friedman (1916-2000) and his colleagues at the Naval Research Laboratory obtained the first X-ray pictures of the Sun in 1960, during a brief 5-minute rocket flight, ttese crude, early images were replaced with high-resolution X-ray photographs taken and returned to Earth by astronauts from NASA's Skylab thirteen years later, during
Blue light is scattered in all directions, a phenomenon similar to that seen in the Earth's sky, hence its colour blue, This is one reason why reflection nebulae appear so blue on photographs, it is just the blue wavelengths of the light from (usually) hot blue stars nearby- To be scientifically correct, the nebulae should be called scattering nebulae instead of reflection nebulae but the name has stuck. This property is often called interstellar reddening. An interesting property of the scattered light is that the scattering process itself polarises the light, useful in the studies of grain composition and structure-
Now what would a solar observer do with a moon filter The PST (or any other solar hydrogen alpha telescope) is totally unsuitable for viewing anything bar the Sun. One of the biggest problems I have with imaging the Sun using simple digital photography is that the image is often overexposed. The use of a moon filter (this one lets through 18 of the light) overcomes that difficulty, although there is often an accompanying loss of definition, unfortunately (Figure 2.50).
As they circled the Moon prior to undocking from the Lunar Module, the crew had a little sightseeing time to themselves. Each time they flew around to the far side of the Moon they lost radio contact with Earth, which meant that, apart from a few small procedures, they were able to look down on the lunar surface below and take photographs for later examination. On the Moon's near side, Schmitt recalls being impressed by how much light the Earth cast on the Moon. Features were very clearly discerned in the spectral blue light, ''and really quite spectacular.'' Then he saw something that really took his breath away.
Whilst Coronado markets the PST as being for visual use, it does not stop enterprising amateurs from taking photographs with it. Personally, I use a domestic Sony Cybershot P72 camera, which has 3.2 megapixels. This was purchased in 2003 at a not inconsiderable expense, but you can now get better ones for less money. I just simply hold the camera to a telescope eyepiece and snap. There are, however, various mounting brackets that you can use that enable a camera to be held steadily against the eyepiece.
The image seen through these devices is also right side up, as in terrestrial telescopes. Seen as an image on a phosphor screen, it is monochrome green (Figure 2.1). At first this might seem to be a distraction, but it is amazing how quickly the eye gets used to it, and effectively interprets what it sees as black and white even a partially dark adapted eye reduces awareness of color still further. Green pictures would be a distraction (although striking ), because in the context of the page, and in normal lighting conditions, they will only be seen as green For this reason, all intensified real time images are reproduced here black-and-white. (Those by W.J. Collins, digital camera short time exposures, are in color, to convey the initial live impression through the telescope.) The color of the intensifier image is not just a quirk that we have to live with it is selected as the best frequency for the eye in dark conditions. The image, of course, includes all frequencies, even those...
Digital SLR cameras are simple to employ at the focal plane of our telescope. CCD cameras, optimized for astronomy, are still the best for studies requiring maximum performance, such as deep-sky surveys, but digital cameras have other advantages. These advantages include a single unit, compact size, optical viewfinder and a high-performance, film-sized, color CCD CMOS sensor. In addition, their cost is falling almost monthly, already becoming much much cheaper than a dedicated CCD camera. The large size of the sensor used can be quite decisive for some scientific studies like nova detection. Overall, digital cameras are not in competition with CCD cameras but rather are complementary. The RAW format is virtually mandatory to get the best out of a digital camera. In this format, the camera records the image as it comes straight off the sensor (unfortunately some exceptions exist, like the Nikon D70 where a median filter is systematically applied to the RAW image...
If ever there was something in outer space that stares back at you it is this amazing planetary (Figure 7.22). It is hard to get a really good idea of this without an image intensifier, the use of which will resolve it as a circle enclosing the eye-shape itself, with its central star resembling the pupil My first intensified view startled me, with its clear and bright resolution, not to mention the strong suggestion of a human eye. The image certainly does appear like the well-known photographs showing its more human form. Using a light filter instead of the image intensifier, it is easy to see why it is also known as the Ghost of Jupiter, since aside from the similar shape and size, the more transparent presence of the nebula does suggest something of a spiritual apparition of the giant planet. There are other planetaries with something of this elliptical shape as a hallmark, but none impose so strongly a living personality as does this one.
Having settled that, what type of film should we select for our lunar photography It is always nice to have colour photographs but that is hardly essential in the case of the Moon. Even better if we can give slide shows of our photographs, though colour prints are sometimes more convenient. Certainly they are more portable than a slide projector and screen. However, it is now easy and fairly inexpensive to get prints run off from colour positive ( 'transparency', also known as 'slide') films. Another factor we should consider is the levels of contrast we can expect in our final photographs but I defer a discussion of this until Section 4.6. If we are using a colour film, the accuracy of the colour reproduction is also of some concern. Not all colour films will give natural looking reproductions of the Moon's subtle tones. In fact, do we need a colour film at all, since most people see the Moon as stark blacks, greys and whites, anyway After the foregoing generalities it is now time to...
They also took stereo photographs of themselves in different postures to provide further evidence of changes in spinal contour, height and the range of motion of their vertebral columns. This was followed by MRI scans after landing. To stimulate their sensory nerves, they applied tiny electrical impulses to their ankles and measured the time it took for signals to reach their brains using a nerve stimulation and recording device. They also monitored their autonomic nerves by squeezing hand grips, as electrodes gathered blood pressure and heart rate data, and synchronised their breathing on audio tape for another heart rate study.
Several of the Surveyor spacecraft returned photographs showing an unmistakable twilight glow low over the lunar horizon that persisted for about an hour after the Sun had set (Figure B.13a). An Apollo surface experiment, the Lunar Ejecta And Meteoroids experiment (LEAM) detected an order-of-magnitude increase in particles striking the detectors during local sunrise and sunset (Figure B.13b). Most of the events registered by this experiment were found to have been caused by electrostatically-charged and transported lunar dust. A pronounced increase in the dust impact rate occurred around the sunset and sunrise terminator crossings. The increase began about 150 hours before sunrise, while the Sun was still 70 degrees below the horizon.
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Digital Camera and Digital Photography
Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.