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6.
Advance the film and repeat the process.
Lunar Phase
Crescent
Quarter
Full
Above is a listing of recommended exposure times when photographing the Moon at the
The exposure times listed in table 8-1 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 will get a good photo.
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If using black and white film, try a yellow filter to reduce the light intensity and to increase contrast.
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Keep accurate records of your exposures. This information is useful if you want to repeat your results or if you want to
submit some of your photos to various astronomy magazines for possible publication!
•
This technique is also used for photographing the Sun with the proper solar filter.
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This form of celestial photography is designed for objects with small angular sizes, primarily the Moon and planets. Planets, although
physically quite large, appear small in angular size because of their great distances. Moderate to high magnification is, therefore, required
to make the image large enough to see any detail. Unfortunately, the camera/telescope combination alone does not provide enough
magnification to produce a usable image size on film. In order to get the image large enough, you must attach your camera to the telescope
with the eyepiece in place. To do so, you need two additional accessories; a deluxe tele-extender (#93643), which attaches to the visual
back, and a T-ring for your particular camera make (i.e., Minolta, Nikon, Pentax, etc.).
Because of the high magnifications during eyepiece projection, the field of view is quite small which makes it difficult to find and center
objects. To make the job a little easier, align the finder as accurately as possible. This allows you to get the object in the telescope's field
based on the finder's view alone.
Another problem introduced by the high magnification is vibration. Simply tripping the shutter ⎯ even with a cable release ⎯ produces
enough vibration to smear the image. To get around this, use the camera's self-timer if the exposure
time is less than one second ⎯ a common occurrence when photographing the Moon. For exposures
over one second, use the "hat trick." This technique incorporates a hand-held black card placed over
the aperture of the telescope to 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.
ISO 50
ISO 100
1/2
1/4
1/15
1/30
1/30
1/60
Table 8-1
prime focus of your CPC telescope.
39
ISO 200
ISO 400
1/8
1/15
1/60
1/125
1/125
1/250
Figure 8-1 - Accessories for
Projection Photography
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