Gamma

Many terms used in planetary imaging are already in frequent use by nonas-tronomers. The digital camera era has plunged many otherwise sane and normal people into the world of image-processing jargon. However, the term gamma is rarely understood and it is so crucial to planetary imaging that an explanation is required. At first glance it would appear that increasing the gamma of an image makes it brighter and reducing the gamma of an image makes it dimmer. However, it is a lot more subtle than...

The Lunar Limb

On a final note, before we leave lunar orbit, I would like to say a few words about observing the lunar limb regions. It is often said that there is little point observing the Moon when it is full, simply because there are no long shadows and the finest details are always glimpsed when the Sun is very low over the formation being studied. Thus, at sunrise and sunset, maximum contrast is seen. At full Moon, the regions on virtually all the visible lunar disc are experiencing the Sun well above...

Saturns Weather and the Great White Spots

To the beginner, Saturn's globe appears fairly featureless when viewed through the eyepiece. Although Saturn does have equatorial, tropical, and temperate belts and zones (Figure 14.1), there is nothing on the disc that stands comparison with the Jovian Great Red Spot or even the giant planet's North and South Equatorial Belts. Undoubtedly, the huge amount of internal heat produced by Jupiter, combined with its closer proximity to the Sun, is responsible. Heat is the driving force behind...

Alpha Imagin

When you first look through an H-Alpha filter you will be struck by the deep red color of the image. It is immediately obvious that this is a redder red than you see in everyday life, and the color may be a bit off-putting at first. However, this is no problem for the CCD detector in a webcam, which is very sensitive at 656 nanometers. A monochrome webcam like the ATiK 1HS is the best choice as it is pointless using a color webcam for such narrow-band work. However, digital SLRs, and even small...

Space Probes And Hubble

As well as observing the planets out of sheer fascination and actually seeing them with your own eyes, the images returned by planetary space probes throughout the last few decades have been truly staggering and are well worth tracking down on the web. While manned spacecraft have only traveled as far as the Moon, unmanned robotic spacecraft have traveled to every planet except Pluto. Traveling at speeds as fast as 60,000 kilometers per hour (17 kilometers per second), these probes still take...

Advanced Stacking of Rippling AVI Frames

We have already examined the remarkable Registax software developed by Cor Berrevoets, a software package that has made the stacking of thousands of AVI frames a routine and reliable operation. However, few amateurs who use Registax seem to have the spare time or the inclination to examine exactly how it works and to assess which options are the best in different situations. However, a full understanding of Registax' strong and weak points can be of great use. As a Registax user myself, I hope...

Collimation

I never fail to be astounded at the number of amateurs who do not keep their telescopes collimated. I wonder whether they are simply scared of doing more harm than good, or even damaging the instrument. Admittedly, the traditional methods of star collimation are best done with two people, but, for the webcam user, this is just not necessary. It must be said that not all telescopes, even expensive ones, have friendly mirror adjustment systems. I know of one world-class planetary imager who...

Ultimate Planetary Telescopes

What is the ultimate planetary instrument Is there such a thing at all and what, exactly, do we mean by ultimate I have touched on this subject already when discussing the relative merits of my own Newtonians and the long-focus Newtonian. One way of answering this question is simply to look at what telescopes the world's leading planetary imagers use. However, when we do this we just see a reflection of the market share of different telescopes. Damian Peach,...

The Deep Red Advantage

At first it might not be clear how the LRGB technique can be applied to curing atmospheric dispersion. Surely, in the luminance image, the full dispersive smearing is still captured, but is it simply a monochrome smearing Well, this is true, but Figure 8.3. Once LRGB processing is checked, the LRGB sliders in Registax allow the luminance signal to be constructed from any mixture of the color channel signals. Figure 8.3. Once LRGB processing is checked, the LRGB sliders in Registax allow the...

Holiday Destinations

Of course, a lot depends on where you actually live an amateur astronomer in the U.S. is unlikely to prefer a Mediterranean destination to a Caribbean one unless he or she wants to combine a European north African sightseeing trip with a bit of astronomy. The requirement is, of course, to head closer to the equator so that the planet is higher up. Also, a site that enjoys clear skies much of the time is essential, as is a site renowned for its good seeing. As we are planning on heading nearer...

The Martian Moons

A real challenge for the amateur observer, even at a favorable opposition, is spotting the Martian moons Phobos and Deimos. In a large amateur telescope these 11th and 12th magnitude moons would not normally be a challenge, but they never stray far from the brilliant Martian disc and their rapid orbits mean they move considerably even in one night. Phobos is the larger Moon at over 20 kilometers across but never strays more than a Martian diameter from the planet, making it the hardest to see....

Quick Start Guide

This Quick Start Guide is designed for those people who have limited knowledge of webcams or image processing but are comfortable with PCs and gadgets, have a telescope, and just want to get up to speed quick. In other words, they want to get some good lunar or planetary images in the next few days, without studying every chapter of this book. If you fall into this category, this section is for you. Assuming you have a USB-equipped PC newer than 1998, you need to have the following, all of...

Equipment For The

On a planetary imaging trip you will need to cart several thousand dollars worth of fragile equipment to your destination so, the first point to note is that you will need adequate travel insurance. Your basic insurance will almost certainly be inadequate. Also, when observing far from home, you cannot suddenly dash indoors to get some vital piece of equipment if a problem arises. Therefore, some forward thinking is highly advisable. Note well the bits and pieces you use at home before you fly...

Final Processin

The Wavelet page is, undoubtedly, the Registax page where really excellent images are created. This is where you can endlessly tweak, tweak, tweak, tweak, tweak the image until you are diagnosed as having an obsessive compulsive disorder and the men in white come to take you away. What in God's name is a wavelet anyway Well, the term wavelet originates from the world of DSP, or digital signal processing. In electronics, as well as in planetary imaging, the challenge is often to extract signal...

Dispersion

So far we have mentioned little about the color aspects of planetary image processing, but a vital understanding of color and the eye brain perception of what appears on your monitor screen is essential. From latitudes well away from the equator, the planets are never going to be directly overhead. This instantly causes a problem with respect to atmospheric dispersion, i.e., the splitting up of colors into a spectrum. We have all seen the way in which a prism splits light up into its...

Image Scale Considerations

Let us have a look at this image scale business in more detail because it is important to understand the issues involved. Most of the popular webcams have CCD chips with an array of 640 x 480 pixels. These pixels are, typically, 5.6 microns in size. So the imaging chips themselves are roughly 3.6 x 2.7 mm across. The standard formula for calculating the resolution of a telescope, in arc-seconds, is given either by 138 D (the Rayleigh limit) or 116 D (the Dawes limit), where D is the Figure 7.2....

Ptolemaeus [92 S 18 W Alphonsus [134 S 28 W and Arzachel [182 S 19 W

Lying exactly on the lunar meridian, but trailing south from just below the center of the disc, one will find three impressive craters named Ptolemaeus, Alphonsus, and Arzachel (Figure 10.27). The trio is so distinctive that it is almost impossible, even for a beginner, not to recognize these three huge craters. Ptolemaeus is the Figure 10.27. Ptolemaeus, Alphonsus, and Arzachel. Imaged on April 9th 2002, with a 37-cm Newtonian at f 14 a ToUcam Pro Webcam. Only six frames were stacked for this...

Saturn through the Webcam

Saturn is the most challenging and, arguably, the most rewarding target for the webcam imager. The biggest problem posed by the ringed planet is simply its low surface brightness. Saturn's globe is 16 times fainter than the globe of Mars and a third as bright as Jupiter. With the maximum available AVI video exposure being 1 5th of a second (5 frames per second at, confusingly, the 1 25th setting on the Philips driver settings) and 1 10th being more desirable (to freeze the seeing) the raw...

Video Options

Webcams are not unique in their ability to freeze the atmospheric turbulence. For many years before the webcam, low-light video and security cameras where used to freeze the seeing, with the added advantage that data can be stored on videotape. In 2005, this data can be stored on a variety of tape formats and on DVD as well. Indeed, the two technologies are now merging, as domestic video recorders featuring terabyte hard disks are now on the market. This book is about lunar and planetary webcam...

Predicting The Atmo Calms

The popular concept of an astronomer's perfect night is one where a cold front has swept through the observer's location and a crystal-clear sky full of twinkling stars can be seen. In fact, this is a nightmare scenario for the planetary observer. A cold front passing through a region may well reduce the moisture content of the air and is great for looking at deep sky objects and comets, but it leaves the air in a very unstable state and, invariably, the hotter ground radiates its daytime heat...

Optical Quali

Intes Micro

A word or two here about optical quality may be appropriate. Manufacturers quite often use the term diffraction limited. This means that the optics are good enough that they are only limited by the laws of physics, and the property known as diffraction limits the resolution of all instruments, whether optical or radio telescopes. The larger the mirror is in relation to the wavelength, the better the resolution you will get. To be diffraction limited, an optical telescope needs to have optics...

Planetary Imagers Worldwide

Despite the ease with which excellent planetary images can now be obtained, planetary imagers are rather thin on the ground among the population. Across the world there are only a few dozen regular planetary imagers whose results are good enough to be used by professional astronomers. Undoubtedly the main reason for this is simply the rarity of good, stable, atmospheric seeing coupled with clear skies, along with the dedication and knowledge required to get world-class results. However, a few...

Saturns Rings

As well as Saturn's rings and the Cassini division providing an excellent sharp edge on which to focus, they also act as a great seeing indicator and can be used to check the color balance of an image. Let us look at the ring structure in more detail. The Pioneer 11, Voyager 1 and 2, and Cassini spacecraft all showed that the Saturnian ring system is highly complex. Fortunately, the view through the amateur's telescope is a lot simpler and basically boils down to a system of three rings,...

Astro Webcam Manufacturers

In the last few years a number of custom companies have sprung up in response to the need for affordable CCD imaging for those amateur astronomers with a tight budget. In many cases the products offered have simply been modified webcams, altered by a few wiring changes such that long, if noisy, exposures are possible, making webcams suitable for deep sky imaging. By stacking hundreds of frames, the noise has been reduced to acceptable levels for exposures of 30 seconds or so often the unguided...

Mercury Map By Mario Frassati

As was the case with my previous two Springer books, I am indebted to the outstanding amateur astronomers who have donated images to this new work. I feel humbled that such great names as Isao Miyazaki, Damian Peach, and Eric Ng to name just three have been so willing to share their images with others via my Webcam User's Guide. I am especially grateful to Damian as he has donated more images than anyone else to this work and it is only by his example, from the cloudy UK, that I was coaxed back...