Celestron G-9.25 - Short Exposure Prime Focus

42 • 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 Celestron T-
Adapter (#93633-A) and a T-Ring for your specific camera (i.e., Minolta, Nikon,
Pentax, etc.). The T-Ring replaces the 35mm SLR camera’s normal lens. Prime
focus photography allows you to capture the majority of the lunar disk or solar
disk. To attach your camera to your G-9
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1. Remove all visual accessories and visual back.
2. Thread the T-Ring onto the T-Adapter.
3. Mount your camera body onto the T-Ring the same as you would any
other lens.
4. Thread the T-Adapter onto the back of the Celestron G-9
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4
while
holding the camera in the desired orientation (either vertical or horizon
tal).
With your camera attached to the telescope, you are ready for prime focus photog-
raphy. 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 PrimeShort Exposure Prime
Short Exposure PrimeShort Exposure Prime
Short Exposure Prime
FocusFocus
FocusFocus
Focus
Table 6-1
Above is a listing of recommended exposure times when photographing the Moon at the
prime focus of your Celestron G-9
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Lunar PhaseLunar Phase
Lunar PhaseLunar Phase
Lunar Phase
ISO 50ISO 50
ISO 50ISO 50
ISO 50
ISO 100ISO 100
ISO 100ISO 100
ISO 100
ISO 200ISO 200
ISO 200ISO 200
ISO 200
ISO 400ISO 400
ISO 400ISO 400
ISO 400
CrescentCrescent
CrescentCrescent
Crescent 1/2 1/4 1/8 1/15
QuarterQuarter
QuarterQuarter
Quarter 1/15 1/30 1/60 1/125
FullFull
FullFull
Full 1/30 1/60 1/125 1/250