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Old 29-04-2012, 09:42 AM
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Tandum (Robin)
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Off Axis Guiders

I've been looking for Large Format OAG's with a minimum 54mm clear aperture. I've excluded the monster OAG due to cost and as far as I can see, that leaves the Atik and the SX.

The Atik chews 24mm of back focus and the SX uses 17mm, so the SX looks like the preferred device. I want to bolt this to a qhy wheel at this stage and was wondering if anyone has done this already?

Also, are there any I've overlooked?
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Old 29-04-2012, 01:11 PM
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bmitchell82 (Brendan)
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Hey Robin,

Im currently prototyping a OAG that directly attaches to the QHY9 FW and Camera to virtually turn it into a QSI type of set up. hence you don't need a massive aperture. It will also be set perfectly for 55mm back focus.

At the end of the day I would look for the strongest body the rotatable ones unless they have a good locking system in my mind are pretty bad as they introduce more flexing points within the system
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Old 29-04-2012, 01:30 PM
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Brendan, I'm putting a qhy11 on the wheel. It needs to be 54mm clear or close to it.
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Old 29-04-2012, 02:28 PM
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An issue is what kind of scope you are putting it on. If it needs a flattener/corrector or if you plan using a reducer, then back focus issues PLUS the diameter of the light circle coming of the back of that will decide what other gear to use. For example the WO-P4 flattener I use on my FLT110 has a T-thread male back end to it, but WO also make another flattener with a 11002-sized exit path but with a fixed back focus of 68mm or something like that and it has a 54mm male back end. The SX OAG supposedly will accommodate an 11002sensor. And you could probably get away with 50mm filters in an SX filter wheel.
Peter
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Old 29-04-2012, 03:36 PM
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Im using one of these, I have found it to be very good.

http://www.teleskop-express.de/shop/...-only-31m.html
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Old 29-04-2012, 03:38 PM
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yep that is fine because the actual FW has a M54 Female thread. so ill be making it the same. Its just picking the right piece of billet ally.
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Old 29-04-2012, 03:45 PM
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Your prototype would attach inbetween the filter wheel and the MPCC brendan? I assume you would take out the optical window so you have a little more room to move.

Sounds interesting.
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Old 29-04-2012, 04:18 PM
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That's right Peter, but the system is virtually sealed so the addition of dessicant plugs will rip the last little bit of moisture out. This will also give me the ability to get a 44mm back focus spacing for a Canon bayonet .
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Old 29-04-2012, 04:50 PM
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Quote:
Originally Posted by pmrid View Post
An issue is what kind of scope you are putting it on.
Cheers pete, this combo will be 35mm from the sensor to the front of the wheel instead of 55mm for the qhy9 so an OAG under 20mm would be the shot. I want to keep the qhy wheel for a bit, there is a link cable coming to power and control it via the camera.

Quote:
Originally Posted by Peter.M View Post
Im using one of these, I have found it to be very good.

http://www.teleskop-express.de/shop/...-only-31m.html
That's a big one pete but out of my price range and too thick for what I want.
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Old 29-04-2012, 05:30 PM
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Robin the only one I know of that is super slim is the TSOAG9 which is 9mm thick. I have the small one (48mm) but I "think" there was a larger version of it. Wouldn't be cheap I expect.


Mark
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Old 29-04-2012, 05:57 PM
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Thanks mark. I think the large one is the one Peter listed. Pricing on them isn't as bad as I thought. The $au looks to be doing pretty good against the euro as well.

Peter will be in Bris tomorrow and is dropping in with a new sx oag he just received so I can measure the thing. I'm hoping I can tap the qhy wheel to take an sx oag
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Old 30-04-2012, 10:42 PM
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The sx won't fit, it's outer diameter is 75mm. What ever I bolt on the motor side of the qhy wheel must have a diameter no greater than 60mm.
That motor box continually gets in the way of everything you try to do with these qhy wheels.
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