Celestial Photography • 55
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 onto 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 field based on the finder 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.
Advance the film and your 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.
Eyepiece Projection
