Celestron CPC 925 GPS XLT Computerized Telescope Instruction Manual - Page 43

Page 43 highlights

Lunar or small planetary nebulae-f/10 imaging is more challenging for long exposure, deep-sky imaging. Guiding needs to be very accurate and the exposure times need to be much longer, about 25 times longer than f/2. There are only a select few objects that work well at f/10. The moon images fine because it is so bright, but planets are still a bit small and should be shot at f/20. The Ring nebula is a good candidate because it is small and bright. The Ring Nebula (M57) can be imaged in about 30-50 seconds at f/10. The longer the exposure the better. Planetary or Lunar-f/20 is a great way to image the planets and features on the moon. When imaging the planets, very short exposures are needed. The exposure lengths range from .03 to .1 seconds on planetary images. Focus is critical as is good atmospheric conditions. Generally you will take one image after another until one looks good. This is due to the atmospheric "seeing" conditions. For every 10 exposures you might save 1. To image at f/20 you need to purchase a 2x Barlow and a T-adapter or Radial Guider. Auto Guiding The CPC has a designated auto guiding port for use with a CCD autoguider. The diagram below may be useful when connecting the CCD camera cable to the CPC and calibrating the autoguider. Note that the four outputs are active-low, with internal pull-ups and are capable of sinking 25 mA DC. No Connect Figure 8-7 - Pin out diagram for Autoguider port. 43

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43
Lunar or small planetary nebulae--
f/10 imaging is more challenging for long exposure, deep-sky imaging.
Guiding needs to be very accurate and the exposure times need to
be much longer, about 25 times longer than f/2.
There are only a select few objects that work well at f/10.
The moon
images fine
because it is so bright, but planets are still a bit small and should be shot at f/20.
The Ring nebula is a good candidate because it is small
and bright.
The Ring Nebula (M57) can be imaged in about 30-50 seconds at f/10.
The longer the exposure the better.
Planetary or Lunar--
f/20 is a great way to image the planets and features on the moon.
When imaging the planets, very short exposures are needed.
The
exposure lengths range from .03 to .1 seconds on planetary images.
Focus is critical as is good atmospheric conditions.
Generally you will
take one image after another until one looks good.
This is due to the atmospheric “seeing” conditions.
For every 10 exposures you might
save 1.
To image at f/20 you need to purchase a 2x Barlow and a T-adapter or Radial Guider.
Auto Guiding
The CPC
has a designated auto guiding port for use with a CCD autoguider.
The diagram below may be useful when connecting the CCD
camera cable to the CPC and calibrating the autoguider. Note that the four outputs are active-low, with internal pull-ups and are capable of
sinking 25 mA DC.
Figure 8-7 – Pin out diagram for Autoguider port.
No Connect