Telescope Maintenance 53
1. Polar align the telescope (using one of the methods described earlier) and start the clock drive.
2. Load your camera with slide or print film, ISO 400 or faster!
3. Set the f/ratio of your camera lens so that it is a half stop to one full stop down from completely
open.
4. Set the shutter speed to the "B" setting and focus the lens to the infinity setting.
5. Locate the area of the sky that you want to photograph and move the telescope so that it points in
that direction.
6. Find a suitable guide star in the telescope field. This is relatively easy since you can search a wide
area without affecting the area covered by your camera lens. If you do not have an illuminated
cross hair eyepiece for guiding, simply defocus your guide star until it fills most of the field of
view. This makes it easy to detect any drift.
7. Release the shutter using a cable release.
8. Monitor your guide star for the duration of the exposure making all corrections using the hand
controller. If not using the optional DEC motor, then corrections to the declination axis must be
made carefully turning the DEC slow motion by hand as needed.
9. Close camera's shutter.
As for lenses, use only those that produce sharp images near the edge of the field. The lenses should have a
resolving power of at least 40 lines per millimeter. A good focal length range is 35 to 200mm for lenses
designed for 35mm cameras.
The exposure time depends on the film being used. However, five minutes is usually a good starting point.
With slower films, like 100 ISO, you can expose as long as 45 minutes. With faster films, like 1600 ISO,
you really shouldn't expose more than 5 to 10 minutes. When getting started, use fast films to record as
much detail in the shortest possible time. Here are proven recommendations:
• Ektar 1000 (color print) • Scotchchrome 400
• Konica 3200 (color print) • T-Max 3200 (black and white print)
• Fujichrome 1600D (color slide) • T-Max 400 (black and white print)\
• 3M 1000 (color slide)
As you perfect your technique, try using specialized films that are designed or specially treated for celestial
photography. Here are some popular choices:
• Ektar 125 (color print) • Tech Pan, gas hypered (black and white print)
• Fujichrome 100D (color slide) • T-Max 400 (black and white print)
As with all forms of photography, keep accurate records of your work. This information can be used later if
you want to reproduce certain results or if you want to submit photos for possible publication.
Once you have mastered piggyback photography with wide angle and normal lenses, try longer focal length
lenses. The longer the focal length, the more accurate your guiding must be. You can continue to increase
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