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Astro-Tech 72 ED mounting ring options?

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#1 bjgiii

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Posted 11 May 2014 - 06:38 PM

I have recently acquired an AT72ED. It doesn't come with mounting rings. I will be using this scope for AP. Does anyone have any suggestions on a good set of mounting rings. Is there a set that would allow a small guide scope to be mounted on top? I have two mounts that this could be used on. A cgem and AVX. Also what focal reducer/flattener would you recommend. This will also be used with a canon dslr. Any other accessory suggestions would be great. Thanks for the help.

#2 terry59

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Posted 11 May 2014 - 08:49 PM

I use these with some strapping material I picked up at Walmart and have no problems. I use the Orion field flattener and Orion 0.8x reducer. With a small chip like the Atik 314L+ it is flat. With an APS-C chip expect some corner issues. A self centering adapter will help a lot also.

#3 bjgiii

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Posted 11 May 2014 - 09:10 PM

Terry,
Are those rings from orion? and is that an adm mini dovetail? how do you secure your setup to the mount. Thanks.

#4 rhcrooks

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Posted 12 May 2014 - 02:03 AM

The Orion rings almost fit the AT72ED tube. What I did was put one ring on the tube itself, and another ring on the focuser part (which is a slightly larger diameter than the OTA). The stock rings fit perfectly on the focuser part, but in order to get a tight fit on the OTA I bought some cork sheeting and replaced the felt with a couple layers of cork.

After this modification I had pretty bad cone error on gotos, which I fixed by shimming the focuser tube ring by about 1mm between the dovetail and the base of the ring.

These rings have screw threads at the top too where you can affix attachments as terry59 has done above.

#5 bjgiii

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Posted 12 May 2014 - 05:12 AM

For such a popular ota, you would think they would make some specifically for it.

#6 terry59

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Posted 12 May 2014 - 07:52 AM

Terry,
Are those rings from orion? and is that an adm mini dovetail? how do you secure your setup to the mount. Thanks.


Yes to the first two questions. Not sure I understand the last one...it fits in the saddle :question:

#7 bjgiii

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Posted 12 May 2014 - 08:04 AM

Terry,
Sorry about the confusion. Does the mini dovetail fit in the vixen style saddle. It looks a little narrow. Thanks.

#8 terry59

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Posted 12 May 2014 - 08:37 AM

Yes it fits fine

#9 bjgiii

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Posted 12 May 2014 - 10:56 AM

Larry,
I checked out the images you took with the Ota. They look great. Any flexure problems with your setup?

#10 rhcrooks

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Posted 18 May 2014 - 03:22 AM

Here's a frame from my at72ed with a trf-2008 0.80x flattener/reducer. It's an unguided 90s exposure on a Orion Sirius mount.

With such a short effective focal length it's probably unnecessary to use tube rings, and the flexure in the focal tube might actually be below what the scope can image (not sure on that one). I know I'm at around 3"/pixel when imaging with the AT72*0.08. It's very forgiving.

#11 bjgiii

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Posted 18 May 2014 - 11:51 AM

rhcrooks,
Are you imaging with a dslr or a ccd?

#12 rhcrooks

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Posted 24 May 2014 - 12:14 AM

That was taken with a Canon DSLR (60D)


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