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Equipment Discussions >> Cats & Casses

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Heitman
sage
*****

Reged: 01/26/07

Loc: Reeds, NC
Re: Compression ring visual back? new [Re: Pete-LH]
      #5686627 - 02/18/13 09:05 AM

Ralph,
Could you tell me the length of the Virtual View? I've been looking at this unit as a possible visual back for my C8. Right now I use a standard 2" visual back, but it's a real pain to have to loosen and tighten it to move the diagonal to different positions.
Thanks, Tim


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zippeee
sage


Reged: 12/27/10

Loc: Alberta, Canada
Re: Compression ring visual back? new [Re: Pete-LH]
      #5686660 - 02/18/13 09:33 AM

Quote:

The Click lock is the most secure and well centered mechanism that I have encountered so far.




Without a doubt. Remember this picture?



If anything was to fail, my bet would be on the T2 threads pulling out of the diagonal.


--


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Kon Dealer
professor emeritus


Reged: 01/05/11

Loc: Cambridge UK
Re: Compression ring visual back? new [Re: Pete-LH]
      #5687392 - 02/18/13 05:30 PM

I'm really puzzledthat Celestron etc. have not seen a market for visual backs with compression rings for fitting diagonals/EPs- like there are on any half-decent refractor.

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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: Compression ring visual back? new [Re: Kon Dealer]
      #5687743 - 02/18/13 08:31 PM

I still can't grasp why they move the primary mirror to focus instead of putting a real focuser on them.

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mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Compression ring visual back? new [Re: watcher]
      #5688591 - 02/19/13 10:02 AM

Quote:

I still can't grasp why they move the primary mirror to focus instead of putting a real focuser on them.



Joe,

So the scopes can offer huge amounts of focus travel. Depending on the SCT model it can range from 6 to more than 11". This makes them very versatile scopes without requiring additional cost items to bring various optical configurations to focus.

The design has been commercially popular since the 60s ... they must be doing something right.


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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: Compression ring visual back? new [Re: mclewis1]
      #5688924 - 02/19/13 01:33 PM

I understand the reasoning, but I think the trade off of a changing focal length is just not worth it in most cases. The versatility leaves a bit to be desired also. When I bought my IM715 it came with a 2" Berlbach visual back. Coupled with a 2" diagonal, I couldn't get an eyepiece to focus!

If I could figure out where to set the mirror to leave it alone, and what focuser might work with it, I would gladly go that route.


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