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Atlas Mount C'Shaft Upgrade..worth it?

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#1 John Miele

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Posted 27 June 2009 - 11:40 PM

I'd like some opinions. I'm thinking about upgrading my Atlas EQG counterweight shaft to a 1.0 inch OD SS version. I am imaging with a C11 and a ST-80 using all ADM saddles and dovetail plates. I need 46.5 lbs to balance it all out. My question is do you really think it will make any difference in guiding accuracy? I know the thicker shaft will be stiffer and flex less. But when guiding, the scope is moving so slowly I can't see how this would matter much. And when I balance out the scope, I know that the shaft will flex as the scope moves to a new position, but the deflection of both the stock shaft and the 1" shaft must be tiny, and balancing is approximate anyway, so again, I can't imagine it making a lot of difference. That being said, if anyone has done this upgrade and noticed a difference I would like to hear about it. I don't mind spending the money as long as there is a real payback in performance. Thanks. -- John

#2 rmollise

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Posted 28 June 2009 - 08:12 AM

I'd like some opinions. I'm thinking about upgrading my Atlas EQG counterweight shaft to a 1.0 inch OD SS version. I am imaging with a C11 and a ST-80 using all ADM saddles and dovetail plates. I need 46.5 lbs to balance it all out. My question is do you really think it will make any difference in guiding accuracy?


Will it make any difference in guiding accuracy? No. Not if you are properly balanced as you are now (i.e., slightly east-heavy).

#3 coper4

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Posted 28 June 2009 - 03:33 PM

I have a friend that made his own 1" OD SS CW shaft for his Atlas EQG mount. I believe his is about 18" long. He has noticed a big drop in the weights he has to use as well as virtually no vibration when focusing. He has a Meade LX200R 10" on the mount. I don't know about imaging but the lack of vibration must help. Hope this helps.

#4 gnowellsct

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Posted 29 June 2009 - 01:48 AM

Well, Losmandy uses just over an inch diameter, if memory serves; and AP uses something like two inches on the CW shaft. These are two of the pre-eminent design shops. It should be telling you something.

I think it does make a difference--not in imaging, but in image stability. I can't speak to imaging because I don't do it. All you have to do is think of a slight gust of wind pushing at the top of your OTA and now you have 45 lbs of counterweights hanging by a skinny shaft. That's going to lead to flexures and resonances that won't be there with a thicker CW shaft. You may not *see* it, but it's going to be there at the pixel level.

You know, it isn't a bad mount, but it was also designed with cost minimization in mind. So part of what you're doing is trying to figure out ways to un-cheap-out where the OEM cheaped out.** That's a reasonable project.

The question is whether "that's all there is." That is to say if you were going to modify some one thing is this the most efficient thing to modify, or would a better tripod or some other thing do more for the buck. I can't answer that, but the existence of a counterweight upgrade aftermarket that seems to be "settling in" to servicing a regular clientele indicates that some smart people have gone over this mount and concluded the CW shaft is a significant vulnerability.

regards
Greg N

**ps. Losmandy owners who upgrade to the Ovision worm design are in essence doing the same thing, figuring out where the design "cheaped out" and fixing it. This is by no means limited to your own product. (But it's fair to say that the Losmandy crowd is throwing dollars at a higher level of expectations.) You can even say that AP "cheaps out" by not having mount modeling in the hand paddle, which forces users to buy the Software Bisque add-on. So I don't wish to say that only Atlas Mounts have these issues. But even judiciously taking all that into consideration, a minimalist cw shaft strikes me as not a good sign about the OEM's commitment to quality design. The CW shaft is therefore very likely an issue.

regards
Greg N

#5 John Miele

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Posted 29 June 2009 - 03:39 PM

Well thought out reply with some very good points. Thanks Greg.






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