Meade 8" SCT autofocus

[yomamma]

I've got a Meade 8" ACF SCT and it is great for EAA and I want to see if I can get some good DSO shots with it. I have an Optec auto-focuser that replaced the factory focuser and I can get it to work well but my FWHM scores and focusing are a bit tougher than my refractors.

In testing the other night I can't seem to get a score much lower than 4.5 - 5. The moon was out and I had not mitigated the street light(I cover it with a box) so there was a lot of noise around. It was also 90 degrees at 11PM and seeing was not that great.

Maybe in the fall and winter when seeing is better it will improve. Does anyone have an SCT they autofocus and what type of scores do you normally get on a good night(and bad night)?

Thanks

[admin]

The score you get depends not only on the telescope but on the camera in use too, so be sure to take that into account. For instance if you are using an IMX174 based camera with big 5.8 micron pixels, the score will be less than half the score with an IMX183 based camera with 2.4 micron pixels.

Also, expect higher values on a long focal length camera - everything is magnified, including the effects of seeing and the limiting star size from the airy diffraction disk from the telescope aperture.

cheers,

Robin

[Chris_h]

With my C9 and asi585 binned 2x2 (well sampled), I get just below 4 on avarge. On good nights with perfect focus, I have hit 3.2 at best