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Go Back   IceInSpace > Equipment > ATM and DIY Projects

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Old 27-11-2011, 01:17 PM
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mldee (Mike)
Gadget freak

mldee is offline
Join Date: Aug 2008
Location: Near Warwick, Qld, Australia
Posts: 510
Making a dedicated C8 Hyperstar unit with electronic focus

I have two older C8s (1990's) that I have gotten a lot of use out of, but now I have my CF RC8 for longer FL work.

I purchased a C8 Hyperstar kit a couple of years ago and use it occasionally for the big stuff.

Used C8's are starting to drop in value, but I will probably put one on the market soon anyway. (If you're in the Brisbane area and want one, PM me), So I was thinking of keeping one and modifying it to be a dedicated Hyperstar unit. These require very accurate focussing, mine already has the FT focuser, but I can't remotely focus from in the house, which I can do with my other scopes. I don't like mozzies.

I was thinking of removing the complete rear assembly and baffle tube, which the mirror presently "slides" on for focus, and replacing it all with a similar-diameter tube glued to the primary mirror rear/hole, which was in turn then fixed to the 2"diam inside draw tube of a $99 GSO-style SCT Crayford of the type that threads directly to the rear visual back assembly of the OTA, which I could then easily motorise and would also hopefully get non-slop mirror focussing. And yes, clearances would be very important, but they couldn't be any worse than the present floppy single-rod arrangement used for the "sliding mirror" at present.

I realise that I may/would lose a lot of the great back focus capability that the C8's have, but as a dedicated Hyperstar unit with a dedicated QHY8 Pro camera permanently at the front, all I really need is ongoing fine focus once I have set the mirror/new tube assy at the optimal distance.

It would make a great low cost versatile remotely-controllable 425mm f2.1 wide field unit. And if it didn't, well not that much down the drain.

Has anybody ever done this sort of focus mod for a C8 Hyperstar?

Last edited by mldee; 27-11-2011 at 06:29 PM. Reason: Clarity
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