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Another FSQ-106 adapter & working distance puzzle...

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#1 leviathan

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Posted 02 December 2019 - 12:58 PM

I know for many, myself included, FSQ-106 charts are a bit complicated to say the least. Now if we add 645 reducer here things get even worse.

So I've got aforementioned scope with large 0.72x reducer, apparently CCA-250 and KP86003 (?) adapters, as well as wide Canon t-mount. Am I using correct adapters ? (photos attached)

 

Now if I want to use it with SBIG STF-8300M CCD camera (16.5mm working distance to sensor) and ZWO 7x36mm filter wheel (20mm width) what else do I need ? According to this chart KP86003 adapter has M54x0.75 female thread on it ? And reducer's working distance from the end of it is 56.2mm ?

 

Also, 645 reducer threads directly into the rear lens group cell, not the focuser. While CCA-250 and all other adapters after it screws ON focuser. Now, how to maintain correct working distance in this case ? Especially when focus shifts over the night.

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#2 chadrian84

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Posted 03 December 2019 - 12:54 PM

First decide how you want to connect the EFW to the m54 female thread on part KP86003 (also called part 8A).  You could either get an m54 to m42 adapter and skip the Canon part, or it may be easier to use the Canon part and find a Canon to M42 adapter.  Then decide how you want to connect the EFW to the camera (m42 adapter to whatever the SBIG camera uses).  If necessary purchase appropriate extensions to get your sensor around 56.2mm from the tip of the KP86003; anywhere from about 45-65mm should allow enough room to find and stay in focus all night.

A benefit of the fsq design is that all you need to do is get in focus. Backfocus (aka metal back distance or what you’re calling working distance) can be ignored as long as you’re in focus.  The focuser will allow plenty of room for focus shift during the night.


Edited by chadrian84, 03 December 2019 - 05:15 PM.

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#3 leviathan

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Posted 03 December 2019 - 09:55 PM

Hi Chad. I saw your messages in other topics on similar questions when you bought your FSQ-106 and 645 reducer. Glad that you responded here !

How are things going since then ? Are you happy with your setup ?



#4 chadrian84

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Posted 04 December 2019 - 12:17 AM

Nadir,

The 645 reducer has worked ok.  I think I'd benefit from a tilt adjuster but I don't have enough backfocus to fit one.  Even with custom adapters to fully maximize backfocus I'm barely able to fit a camera, EFW, and OAG onto my Nitecrawler focuser.  With your setup you could probably fit a tilt adjuster if necessary (Gerd Neumann, Sidewinder, etc).

 

Good luck getting things set up.  If I can help let me know.


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