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most stable mount for my Shorttube guidescope

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#1 Tslisher

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Posted 12 January 2013 - 10:36 AM

I'm putting together an astro-imaging rig and would like to use an existing Orion Shorttube 80mm scope for a guide scope and will be mounting it to an existing Losmandy 'D' style dovetail bar on the top of my Celestron 9.25 OTA.

I've heard that the standard 'ring style' mounts that Orion sells may not be stable enough and am thinking instead of using a Teleview 4" clamshell mount with an adaptor plate for the Dovetail mount.

Any insights from the community on if this will be more stable, or any other ways to mount a Shortube to my OTA?

Thanks,

Todd

#2 dickbill

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Posted 12 January 2013 - 12:17 PM

I'm putting together an astro-imaging rig and would like to use an existing Orion Shorttube 80mm scope for a guide scope and will be mounting it to an existing Losmandy 'D' style dovetail bar on the top of my Celestron 9.25 OTA.
Todd


I had this exact configuration: a C9.25 with the Losmandy D style dovetail, plus rings on top of my celestron OTA.
It was way too heavy for a cg5.
It worked, but it was painfull to hear the noise of the motors crinking and clanking. Plus, the two standard weights that came with the cg5/c9.25 were not enough to balance the thing. I had to purchase a third counterweight only to realize soon it would kill the mount.
So i gave up on this, but don't throw away your losmandy plate. My C9.25 had the vixen style plate and when i upgraded my cg5 mount to the cgem, it turned out the losmandy plate could replace the vixen dovetail of the OTA and adapt to the cgem saddle.

So, A CG5 won't do the job if you think to put the c9.25 OTA plus the losmandy plate with rings plus an aditional ota. You will kill the mount.
Think ATLAS or cgem at least.

#3 oo_void

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Posted 12 January 2013 - 03:55 PM

I have ADM Guidescope Rings on mine. Nice and solid.

#4 CJK

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Posted 12 January 2013 - 06:13 PM

+1 on the ADM guidescope rings. I just got a set for my AT72ED -- they really hold the OTA very solidly, no movement at all once the delrin-tipped screws are tightened.

This is the set I have: ADM D Series Adjustable Rings

-- Chris

#5 Tslisher

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Posted 12 January 2013 - 08:42 PM

Thanks,

Actually I have the beefier CGEM mount, so I don't think weight is going to be a problem. Thanks for the advice on the ADM rings. Perhaps I'll go that way.

#6 Tslisher

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Posted 12 January 2013 - 08:50 PM

Just checked out the ADM rings. For the 80MM Shortube, which fit better. The 75mm ADM rings or the 90mm ADM rings. I would assume the 90mm, but can't find any documentation on exactly which ring set would accomodate the 4" diamater of the 80mm Orion Shorttube.

#7 CJK

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Posted 12 January 2013 - 08:58 PM

You may actually have to go much bigger than you think -- I ended up with the 125mm rings for my AT72ED, because (1) you need to get the rings over the various bits that stick out of the OTA (in my case, the dew shield and tripod plate) and (2) you need at least 10 mm on all sides so the threads of the adjustment screws are well engaged in the rings (there is about 3 or 4 mm of delrin on the end of each screw as well).

Measure the outer diameter of your OTA, add 20 mm, and that should be about right. I thought mine were going to be hugely oversized, but they fit just great.

-- Chris

#8 Tslisher

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Posted 12 January 2013 - 09:29 PM

Thanks Chris, I do notice that the dew shield on the front is larger than the main OTA, so I'll measure as you suggest.

Todd

#9 oo_void

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Posted 13 January 2013 - 01:37 AM

Mine are 125mm. And they're Losmandy actually ... Similar in quality to ADM.

#10 Tslisher

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Posted 19 January 2013 - 05:37 PM

I ended up getting the ADM 125mm rings to fit the Losmandy 'D' dovetail, they fit like a charm. They seem farily stable, but just need to get the scope out and check while its slewing. However, clouds are not cooperating. My penalty for living in Michigan in winter.






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