Quote:
Originally Posted by JohnA
Hello all,
i can't plate solve at all, fails every time, so I though to add a guide camera, which I can use to plate solve and to of course guide with.
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1. Platesolving with ASIAir requires a field of half a degree or so. Using your C9.25 you will need an APS-C-sized sensor such as a DSLR or the ASI2600.
2. For guiding there are two issues:
- the image scale of the guide camera (in arcsec/pixel) should be no more than 3X that of the main scope+camera.
- for piggyback setups, flexure between the guide camera and main camera will be your main enemy. This results in egg-shaped stars.
For example using the C9.25 at its native f/10 with a sensor with 3.7 micron pixels, the image scale is 0.32 arcsec/pixel. The guidescope+camera should be no more than 1 arcsec/pixel, which suggests something with a focal length around 750-800mm, which will need to be pretty robustly bolted on the C9.25 for example rings + a Vixen or ADM MDS dovetail bar + radius blocks.
A little ZWO 30mm guidescope sitting in a finderscope bracket is ok for the little refractor crowd, but inadequate to guide a C9.25.
The snag with an OAG is finding guide stars; the field of the guider is tiny.