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Setting spacer distance for CCD


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Hi all, once I get my stuff set up again, I need to sort out getting the distance between the focal reducer and the CCD.

The scope is Skywatcher Evostar 100ED with matching reducer, I have an Atik EFW2 filter wheel with Baader filters and the CCD is an Atik 314L+

I have followed the guidelines for distance and set it with spacers to that distance (the exact number escapes me as it's been 9 months since I last did anything with it, but it is set to the same distance to the DLSR I took off it) but in the limited testing I did I was not completely happy with the sharpness - it may have just been a focus problem, but what I'm looking for is a methodology to follow to get this sorted out as quickly as possible.

So, can someone advise on the best way to approach this please?

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I think you're looking at approx 55/56mm in total. From googling the various bits, then I've come up with:

314L+ is approx 13mm

EFW2 is approx 22mm

FLO M48 to T2 adapter is 10mm

Leaving you with approx 10-11mm left to find - maybe a T2 extension tube and/or some Delrin spacers.

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Hi all, once I get my stuff set up again, I need to sort out getting the distance between the focal reducer and the CCD.

The scope is Skywatcher Evostar 100ED with matching reducer, I have an Atik EFW2 filter wheel with Baader filters and the CCD is an Atik 314L+

I have followed the guidelines for distance and set it with spacers to that distance (the exact number escapes me as it's been 9 months since I last did anything with it, but it is set to the same distance to the DLSR I took off it) but in the limited testing I did I was not completely happy with the sharpness - it may have just been a focus problem, but what I'm looking for is a methodology to follow to get this sorted out as quickly as possible.

So, can someone advise on the best way to approach this please?

Total back focus distance from the rear flange ( where the T thread ends ) of the reducer to the plane of the ccd sensor should be 56~ 56 mm as stated. You also increase the distance by approximately 1/3 of the thickness of the glass filter that is in use so for a Badder this is approx 0.7~0.9mm and for an Astronomic slightly less. Calculate all the optical path of all the stuff in the middle not forgetting to allow 13mm of back focus for the Atik and whatever is left must be made up for with extension rings or small spacers.

A.G

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