When you first purchased that telescope, didn’t you think that it would be pretty cool to stick a camera on the end of it?

For taking pictures of the moon and planets, a digital camera or webcam can do wonders since the exposures are so short, but trying to take pictures of the faint, far off stuff is much more difficult. These types of deep space objects require extra long exposures. This causes problems:

• Since the stars move, you have to track them to give the camera enough of an opportunity to capture enough of the object through long exposures.

• The longer the focal length of the scope...the more the magnification... and the harder it is to keep the stars “still.” Therefore, tracking the stars with most telescopes require very sturdy EQ mounts. This gets into some rather expensive equipment, especially as the exposure length increases greatly.

• Longer focal lengths require precise tracking...less so with shorter focal lengths….and longer exposures give more opportunities for mistakes. 

So when starting out with DSO photography, I always recommend the “piggyback” method first. This will lessen the premium on the quality of the mount and the precision of your technique.

Piggyback photography is the method of using your camera atop another telescope in order to use the camera’s own lenses. Thus, the camera lens is the “scope” and the mount merely becomes a “tracking platform.” In fact, many people will circumvent telescopes all together by placing the camera (with lens) directly on the mount itself, or even using a manual device called a “barndoor tracker.” Regardless of the mount, it must be equatorially (EQ) aligned (to avoid field rotation) with the ability to move with the stars at the “sidereal” rate.

Why do such a thing? Because it’s easier to shoot astrophotos with a 28mm, f/2.8 lens than with a telescope at 2000mm and f/10 (like an 8” SCT).

The idea is to shorten both the exposure time required and the focal length that is used. In this way, you can lessen the impact of errors introduced into your system, errors that arise from not only your equipment and your technique, but also from the elements.. Wind and light pollution are two examples of such factors that can create havoc with longer exposures.

For example, the picture at right features the Lagoon and Trifid region using a Nikon F2 with 135mm lens piggybacked on a Meade LX-200 with polar wedge. It is a 15 minute long shot at f/4, taken with a regular 35mm camera riding atop a telescope. Because I used a 135mm lens, I decided to “guide” the exposure using a autoguider through the main scope, though I could have easily looked through a illuminated reticle and guided the picture manually, moving the scope by its handpad as corrections were needed, thus keeping a “guide” star centered in the eyepiece. However, 135mm is a focal length that I could have taken “unguided” if my polar alignment was good enough. I just didn’t want to take a chance.

But at focal lengths in the normal 28mm to 50mm range, taking such pictures are almost easy. Doing so would produce a wider swathe of the sky, such as for the entire Milky Way. As long as you get a decent polar alignment, a decent EQ mount (or SCT with a wedge) should keep the stars quite centered with exposures up to 10 or 15 minutes, which is plenty of time when you shoot fast film (like Kodak E200 slide film) or are using a digital camera (with long exposure, or “bulb” capabilities).

Brackets can be purchased for any Schmidt-Cassegrain scope that allow the camera to mount directly to the scope using the 1/4-20 threaded screwhole on the bottom of most SLRs. For heavier lenses, a “dovetail” system is recommended to lessen flexure. German equatorially mounted scopes will require a variety of attachments depending on the type of rings or brackets being used, though some of the less expensive consumer scopes might not be able to carry the weight of such a load.

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