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There are several techniques for this type of photography, and the one chosen will determine the standard
accessories needed. The best method for long exposure deep sky astro photography is with an off-axis
guider. This device allows you to photograph and guide through the telescope simultaneously. Celestron
offers a very special and advanced off-axis guider, called the Radial Guider (#94176). In addition, you will
need a T-Ring to attach your camera to the Radial Guider.
Other equipment needs include a guiding eyepiece. Unlike other forms of astro photography which allows
for fairly loose guiding, prime focus requires meticulous guiding for long periods. To accomplish this you
need a guiding ocular with an illuminated reticle to monitor your guide star. For this purpose, Celestron
offers the Micro Guide Eyepiece (#94171) Here is a brief summary of the technique.
1. Polar align the telescope using an optional equatorial wedge.
2. Remove all visual accessories.
3. Thread the Radial Guider onto your telescope.
4. Thread the T-Ring onto the Radial Guider.
5. Mount your camera body onto the T-Ring the same as you would any other lens.
6. Set the shutter speed to the "B" setting.
7. Focus the telescope on a star.
8. Center your subject in the field of your camera.
9. Find a suitable guide star in the telescope field. This can be the most time consuming process.
10. Open the shutter using a cable release.
11. Monitor your guide star for the duration of the exposure using the buttons on the hand controller to
make the needed corrections.
12. Close the camera's shutter.
When getting started, use fast films to record as much detail in the shortest possible time. Here are proven
recommendations:
• Ektar 1000 (color print)
• Konica 3200 (color print)
• Fujichrome 1600D (color slide)
• 3M 1000 (color slide)
• Scotchchrome 400
• T-Max 3200 (black and white print)
• T-Max 400 (black and white print)
As you perfect your technique, try specialized films, that is films that are designed or specially treated for
celestial photography. Here are some popular choices:
• Ektar 125 (color print)
• Fujichrome 100D (color slide)
• Tech Pan, gas hypered (black and white print)
• T-Max 400 (black and white print)
There is no exposure determination table to help you get started. The best way to determine exposure
length is look at previously published photos to see what film/exposure combinations were used. Or take
unguided sample photos of various parts of the sky while the drive is running. Always take exposures of
various lengths to determine the best exposure time.