Short exposure prime focus – Celestron CR-150 HD User Manual

Page 44

44 • Celestial Photography

Short exposure prime focus photography is the best way to begin recording
celestial objects. It is done with the camera attached to the telescope without an
eyepiece or camera lens in place. To attach your camera, you need the T-adapter
and a T-Ring for your specific camera (i.e., Minolta, Nikon, Pentax, etc.). The
CR-150 HD focuser has a built-in T-adapter and is ready to accept a 35mm camera
body. The T-Ring replaces the 35mm SLR camera’s normal lens. Prime focus
photography allows you to capture the entire solar disk (if using the proper filter)
as well as the entire lunar disk. To attach your camera to your telescope:

Remove the eyepiece from the 1

" eyepiece holder.

Unthread the 1

" accessory adapter from the focuser assembly. This will

expose the male thread of the built-in T-adapter.

Thread the T-ring onto the exposed T-adapter threads.

Mount your camera body onto the T-Ring the same as you would any other
lens.

With your camera attached to the telescope, you are ready for prime focus
photography. Start with an easy object like the Moon. Here’s how to do it:

1. Load your camera with film that has a moderate-to-fast speed (i.e., ISO

rating). Faster films are more desirable when the Moon is a crescent.
When the Moon is near full, and at its brightest, slower films are more
desirable. Here are some film recommendations:

• T-Max 100
• T-Max 400
• Any 100 to 400 ISO color slide film
• Fuji Super HG 400

2. Center the Moon in the field of your telescope.

3. Focus the telescope by turning the focus knob until the image is sharp.

4. Set the shutter speed to the appropriate setting (see table 6-1).

5. Trip the shutter using a cable release.

6. Advance the film and repeat the process.

Short Exposure Prime

Short Exposure Prime
Focus

Focus

Table 7-1

Above is a listing of recommended exposure times when photographing the Moon at the
prime focus of your Celestron telescope.

Lunar Phase

ISO 50

ISO 100

ISO 200

ISO 400

Crescent

1/2

1/4

1/8

1/15

Quarter

1/15

1/30

1/60

1/125

Full

1/30

1/60

1/125

1/250