Astrophotography; Piggyback Photography - Celestron OMNI XLT 102 Instruction Manual

After looking at the night sky for a while you may want to try photographing it. Several forms of photography are
possible with your telescope, including terrestrial and celestial photography. Both of these are discussed in
moderate detail with enough information to get you started. Topics include the accessories required and some
simple techniques. More information is available in various books on the subject matter.
Below is described the traditional photographic methods with traditional equipment. During the last several years,
digital cameras have become very popular and you can use this latest technology to take images through telescopes
and it is relatively simple. In addition, CCD cameras (specifically made for astrophotography as well as Lunar and
Planetary photography have become more economical for hobbyists to procure and have opened new avenues for
taking fantastic images.
In addition to the specific accessories required for each type of celestial photography, there is the need for a camera -
but not just any camera. The camera does not have to have many of the features offered on today's state-of-the-art
equipment. For example, you don't need auto focus capability or mirror lock up. Here are the mandatory features a
camera needs for celestial photography. First, a "B" setting which allows for time exposures and this excludes point
and shoot cameras and limits the selection to SLR cameras, the most common type of 35mm camera on the market
today.
Second, the "B" or manual setting should NOT run off the battery. Many new electronic cameras use the battery to
keep the shutter open during time exposures. Once the batteries are drained, usually after a few minutes, the shutter
closes, whether you were finished with the exposure or not. Look for a camera that has a manual shutter when
operating in the time exposure mode. Canon, Olympus, Nikon, Pentax, etc. have made such camera bodies.
The camera must have interchangeable lenses so you can attach it to the telescope and use a variety of lenses for
piggyback photography. If you can't find a new camera, you can purchase a used camera body that is not 100-
percent functional. The light meter, for example, does not have to be operational since you will be determining the
exposure length manually.
You also need a cable release with a locking function to hold the shutter open while you do other things.
Mechanical and air release models are available.
P i g g y b a c k P h o
P i g g y b a c k P h o
The easiest way to enter the realm of deep-sky, long exposure astrophotography is via the piggyback method.
Piggyback photography is done with a camera and its normal lens riding on top of the telescope. Through
piggyback photography you can capture entire constellations and record large scale nebulae that are too big for
prime focus photography. Because you are photographing with a low power lens and guiding with a high power
telescope, the margin for error is very large. Small mistakes made while guiding the telescope will not show up on
film. To attach the camera to the refractor or Newtonian telescope, use the piggyback adapter screw located on the
top of the tube mounting ring. For the Schmidt-Cassegrain telescope there is an optional Piggyback Camera Mount
available. The cameras have a threaded hole at the bottom of the camera where the piggyback screw threads into.
As with any form of deep-sky photography, it should be done from a dark sky observing site. Light pollution
around major urban areas washes out the faint light of deep-sky objects. You can still practice from less ideal skies.
1. Polar align the telescope (using one of the methods described earlier) and start the optional motor drive.
2. Load your camera with slide film, ISO 100 or faster, or print film, ISO 400 or faster! 2a. When using
digital cameras, experiment with various settings and read the camera instructions as each is somewhat
different than film SLR cameras.
3. Set the f/ratio of your camera lens so that it is a half stop to one full stop down from completely open.
t o g r a p h y
t o g r a p h y
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