CCD - Focal Reducer Distance

[jcm]

A few weeks ago I picked up a SXV-M7 camera for about half price. I thought it would be a good camera to practice with. I also picked up a 0.7X focal reducer. On the edge it says Antares 0.7X - Canada.

I was wondering if there was any specific CCD to reducer distance for optimum results. Perhaps with the small M7 chip its not so vital.

John

[Kaptain Klevtsov]

Check out K3's page http://www.pk3.org/Astro/ the home of K3CCD Tools.

On the equipment page there's a link near the bottom to all sorts of hard sums to do with focal reducers. That might help out.

Captain Chaos

[jcm]

Check out K3's page http://www.pk3.org/Astro/ the home of K3CCD Tools.

On the equipment page there's a link near the bottom to all sorts of hard sums to do with focal reducers. That might help out.

Captain Chaos

Thanks I will have a look

John

[jcm]

er - I have had a look. I think trial and error might be a good idea

The camera will slide into a 2" holder so I should be able to vary the distance easily.

John

[MartinB]

It isn't critical John. The distance between reducer and chip affects where the focuser has to place the reducer in relationtionship to the objective. This in turn affects the amount of effective focal reduction. In reality the difference is is only small and is only really critical if you are close to running out of focus travel or are struggling to frame your image

[jcm]

OK Martin thanks for the info. I had read somewhere about people using the 0.33 reducer on SCT's and this seemed to have to be a set distance to avoid edge distortion.

John

[MartinB]

The Meade 0.33 reducer comes with some spacers which can be used to reduce the focal reduction. Edge of field distortion may be an issue with larger chips at 0.33 and the spacers reduce the reduction. A much bigger problem is vignetting. The 0.33 reducer doesn't work well with an SXVh9 and is a no no with an SLR. I think it will probably be ok with the M7 but you might need flats because of the possiblity of a little vignetting.