Afocal Photography

The aiming and aligning of a camera lens into the telescope eyepiece is called afocal photography and can be used with any camera that has a lens (Figure 2.3). The Moon is excellent for learning how to take afocal photographs. Start by using a long focal length eyepiece with a long eye relief and focus it on the Moon. Figure 2.1. Sun image taken with a Nikon Coolpix 990 digital camera afocal coupled to a Tele Vue 55mm Plossl eyepiece, Tele Vue Paracorr coma corrector, Orion Telescope &...

Conclusions

Webcam astrophotography is only a few years old, and the progress that has been made so far is astounding. We invite you to join the online group QCUIAG. You can learn how to get involved in this hobby yourself for a fraction of the price of professional astrophotography equipment. Jim Hommes - http jthommes.com Astro Carsten A. Arnholm - http arnholm.org Etienne Bonduelle - http www.astrosurf.com astrobond Ashley Roeckelein - http astro.ai-software.com

Hints and Tips

Using fast telescopes or lenses with large and flat illuminated fields makes imaging much easier. Try tripod shots for star trail images. Start with piggyback images and short focal lengths. Constellation images are very forgiving of imperfect tracking. M31 with a 50mm lens is an impressive target. With more experience, longer focal lengths can be used. High-quality fast refractors with flat field like the Televue NP101 and imaging dedicated telescopes like the Takahashi Epsilon are best suited...

Things That Can Go Wrong

Coolpix 990 Afocal Telescope

Camera movement and poor camera alignment over the eyepiece cause blurred images. As your exposure time increases, hand holding the camera steadily and accurately over the eyepiece becomes more difficult. To solve these problems the camera can be mounted on a tripod next to the telescope eyepiece, mounted on the telescope or mounted on the eyepiece. There are several options for mounting the camera (1) use an adapter that mounts the camera on the telescope to position it over the eyepiece, (2)...

The Demands on Image Acquisition

Now that we have optimized our setup we enter the most enjoyable part taking the images Over the last 5 years one trend has emerged. Good images require much longer exposures than anyone at first thought necessary for CCD imaging. In the early days, which are only within the last 10 years, most image exposures were measured in tens of seconds and taken in groups (sequences) of maybe 10. Today, to obtain enough data to produce publishable-quality images, total exposure times can exceed 6 hours A...

The Demands on Equipment

Rcos 20inch Astrophotography

As imagers advance their techniques, they become more critical of star shapes in their images. With sub-arcsecond pixel image scales they find that keeping them tight and round into the extreme corners places a significant demand on their entire equipment setup. With film-format-sized CCD arrays, many scopes need to be modified or even replaced to obtain the quality of images one strives for. Most telescopes deliver fields adequate for the midsized series of CCD cameras, such as the SBIG ST-8...

Image Processing

Using a laptop computer in my observatory means that for processing I have to get all the files, i.e., images and calibration frames, downloaded into my desktop computer. For this I use an ethernet network, which transfers the files in just a few minutes. When they have been backed up to CDROM, they are deleted from the laptop. For many years I used QMIPS32 for calibrating and processing images but I have switched to a combination of the freeware IRIS and MAXIM. The latter software is not cheap...

The Hybrid Image How to Create It

Why bother with mosaics if wide-field vistas can be imaged using short-focal-length instruments The answer is that when using a shorter focal length to achieve greater field size there is an inevitable loss of resolution. Even if we use one of the newer-generation large-format CCD chips, there are few optical designs that have a sufficiently corrected field to take advantage of these large chips. Therefore there remains a very real role for the art of mosaics in producing large-format...

Conclusion

Modern D-SLRs are now available from 1000, which represents a much lower cost than most of the cooled astro cameras. They are multipurpose cameras usable for both daytime and nighttime imaging. They are well suited for gaining experience in the fascinating world of deep-sky imaging because they can provide stunning results on many of the brighter deep-sky objects and all in a simple one-shot color technique. However, the higher noise (compared to most dedicated astro cameras) must be...

Results and Discussion

The low-resolution mode is useful for stellar classification and obtaining spectra of planetary nebula. In the high-resolution mode, many absorption lines are visible of atoms, ions and simple molecules. Figure 11.3 shows the higher-resolu- Figure 11.3. Classification of stars based on their spectra. Spectra were obtained in the high-resolution mode from Hp to HS for stars from early B to M class. Note the increase followed by decrease in the hydrogen absorption lines as one proceeds from B- to...

The Arrival of Affordable Digital SLRs

In June 2002 Canon released its D60 D-SLR model, one of the first 6.3-megapixel cameras. Initial tests published for this camera showed much lower noise in long exposures than all previous models. I acquired one of the first available models. Figure 5.1. Johannes Schedler in his observatory with his 4-inch TMB Apo and Celestron C11 Schmidt-Cassegrain. Figure 5.1. Johannes Schedler in his observatory with his 4-inch TMB Apo and Celestron C11 Schmidt-Cassegrain. Early trials soon showed a...

Image Processing with Photoshop

With Adobe Photoshop you can sharpen the image's lightness channel after wavelet sharpening in RegiStax. Lightness channel sharpening does a good job of sharpening the image without causing color artifacts. There are three steps to this process. First, convert the image to Lab colors. Next, in Channels, select only the lightness channel and do an unsharp mask on it. Finally, convert the image back to RGB colors. The Moon's limb and image noise will determine the strength of lightness channel...

Modified Cameras

Sch Modify Web Came

The specific details of the modifications are best gained from the Web sites given in Table 4.1. Here, we will only cover the subject in broad terms. Also bear in Table 4.1. Web sites with background information on long-exposure modified webcams. mind that astronomical cameras based on these designs are available commercially if soldering to surface mount components is not one of your skills. The first stage is acquiring a suitable webcam. While this sounds trivial, time spent researching the...

Digital Cameras

The Nikon Coolpix 990 995 4500 are great cameras for afocal photography. Their small lens provides a good optical match to eyepieces. They have automatic operation and full manual control of focus, aperture and shutter speed. Also, they Figure 2.10. Adjusting the Nikon 990 camera field stop distance at minimum zoom to match the ScopeTronix 40mm eyepiece eye relief. From left to right camera too close to the eyepiece lens, camera at best position and camera too far from the eyepiece lens. Images...

The Technology

Finger Lake Camera

I have not yet explained what a CCD is. The device invented by Boyle and Smith was named a charged coupled device, hence CCD. It is, of course, a silicon chip -but one with a difference. Whereas most chips are covered in a black plastic casing to keep light out, a CCD chip has a window opening on its top especially to Figure 1.1. CCD chip - note the window on the top surface to admit the light. Figure 1.1. CCD chip - note the window on the top surface to admit the light. let the light in see...

Which Digital Camera to

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...