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act as a shutter. The card prevents light from entering the telescope while the shutter is released. Once the shutter has
been released and the vibration has diminished (a few seconds), move the black card out of the way to expose the film.
After the exposure is complete, place the card over the front of the telescope and close the shutter. Advance the film
and you're ready for your next shot. Keep in mind that the card should be held a few inches in front of the telescope,
and not touching it. It is easier if you use two people for this process; one to release the camera shutter and one to hold
the card. Here's the process for making the exposure.
1. Find and center the desired target in the viewfinder of your camera.
2. Turn the focus knob until the image is as sharp as possible.
3. Place the black card over the front of the telescope.
4. Release the shutter using a cable release.
5. Wait for the vibration caused by releasing the shutter to diminish. Also, wait for a moment of good seeing.
6. Remove the black card from in front of the telescope for the duration of the exposure (see accompanying table).
7. Replace the black card over the front of the telescope.
8. Close the camera's shutter.
Advance the film and you are ready for your next exposure. Don't forget to take photos of varying duration and keep
accurate records of what you have done. Record the date, telescope, exposure duration, eyepiece, f/ratio, film, and
some comments on the seeing conditions.
The following table lists exposures for eyepiece projection with a 10mm eyepiece. All exposure times are listed in
seconds or fractions of a second.
Planet ISO 50 ISO 100 ISO 200 ISO 400
Moon
4 2 1 1/2
Mercury
16 8 4 2
Venus
1/2 1/4 1/8 1/15
Mars
16 8 4 2
Jupiter
8 4 2 1
Saturn
16 8 4 2
The exposure times listed here should be used as a starting point. Always make exposures that are longer and shorter
than the recommended time. Also, take a few photos at each shutter speed. This will ensure that you get a good photo.
It is not uncommon to go through an entire roll of 36 exposures and have only one good shot.
NOTE: Don't expect to record more detail than you can see visually in the eyepiece at the time you are photographing.
Once you have mastered the technique, experiment with different films, different focal length eyepieces, and even
different filters.
Long Exposure Prime Focus Photography
This is the last form of celestial photography to be attempted after others have been mastered. It is intended primarily
for deep sky objects, that is objects outside our solar system which includes star clusters, nebulae, and galaxies. While
it may seem that high magnification is required for these objects, just the opposite is true. Most of these objects cover
large angular areas and fit nicely into the prime focus field of your telescope. The brightness of these objects, however,
requires long exposure times and, as a result, are rather difficult.
Table 7-2
Recommended ex
p
osure time for
p
hoto
g
ra
p
hin
g
p
lanets.