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48 • Celestial Photography
Short exposure prime focus photography is the best way to begin recording celestial
objects. It is done with the camera attached to the telescope without an eyepiece or
camera lens in place. To attach your camera, you need the T-adapter and a T-Ring
for your specific camera (i.e., Minolta, Nikon, Pentax, etc.). The C150-HD and G-8N
focuser have built-in T-adapter and are ready to accept a 35mm camera body. The T-
Ring replaces the 35mm SLR camera’s normal lens. Prime focus photography
allows you to capture the entire solar disk (if using the proper filter) as well as the
entire lunar disk. To attach your camera to your telescope:
1 Remove the eyepiece from the 1
1
/
4
" eyepiece holder.
2 Unthread the 1
1
/
4
" eyepiece holder from the focuser assembly. This will
expose the male thread of the built-in T-adapter.
3 Thread the T-ring onto the exposed T-adapter threads.
4 Mount your camera body onto the T-Ring the same as you would any other
lens.
With your camera attached to the telescope, you are ready for prime focus
photography. Start with an easy object like the Moon. Here’s how to do it:
1. Load your camera with film that has a moderate-to-fast speed (i.e., ISO
rating). Faster films are more desirable when the Moon is a crescent.
When the Moon is near full, and at its brightest, slower films are more
desirable. Here are some film recommendations:
• T-Max 100
• T-Max 400
• Any 100 to 400 ISO color slide film
• Fuji Super HG 400
2. Center the Moon in the field of your telescope.
3. Focus the telescope by turning the focus knob until the image is sharp.
4. Set the shutter speed to the appropriate setting (see table 6-1).
5. Trip the shutter using a cable release.
6. Advance the film and repeat the process.
Short Exposure Prime
Focus
Table 6-1
Above is a listing of recommended exposure times when photographing the Moon at the
prime focus of your Celestron Newtonian.
Lunar Phase ISO 50 ISO 100 ISO 200 ISO 400
Crescent 1/2 1/4 1/8 1/15
Quarter 1/15 1/30 1/60 1/125
Full 1/30 1/60 1/125 1/250