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Equipment Discussions >> Mounts

cclark
member


Reged: 07/29/08

Re: CGEM DX dec balance issue
      09/04/12 08:44 PM Attachment (36 downloads)

Excellent info!

Dave - That is a great video! It seems that the rotating of the tube would put the center of mass back over the centerline of the mount, which makes sense. That appears to be what my problem is (off center mass).

Ed - Excellent advice as always. I have hypertuned my mount via your kit and It really helped - it moves as sooth a butter now (many thanks for making this available)! I completely agree about the need to keep some weight on the gears, so I am not trying to get it perfect - just less than it is now. It is really heavy to one side. Like you mentioned, I kept the CW bar axis horizontal and after balancing the dec axis horizontally I moved the scope vertical - and it pulls pretty hard back into the horizontal position. I think I have the front/back balance pretty good (as it stays horizontal and doesn't tip toward the camera end or the business end). It is like a weight is hanging off the side of the tube. I was expecting this to improve when I moved from the SCT to the RC for exactly the reasons you mentioned. I was at a loss when it did not.

Jim - also very good points. I had thought about using some type of weight on the other side of the tube to counter the weight, but I want to explore some other options first. I actually tried something like that when I had the same problem with the SCT, but I couldn't get it right (was just trying to get a ballpark with some 1/4 lb weights taped to the side)


I thought about this quite a bit today and did some measurements and experiments today. What I found seemed to confirm my initial thoughts.

Here is what I did:

First
1. measured and marked the dovetail center with a pencil
2. found the center of the saddle as lined up with a yardstick along the CW bar, through the middle of the polar scope hole and past the worm adjustment hole (the best I could get - I think it was very close)
3. Mounted the scope and marked the dovetail where the saddle center passed.

What I observed (in the attached pic) is that the scope is indeed setting about 0.25" off of center. I think with the weight of the RC, guide scope, etc. all setting off center, it is causing the issue I am seeing.

Second
1. After reconfirming my front/back balance horizontally, I rotated the RA back to center and when releasing the dec clutch, the scope falls to the left (viewed from behind - the side to which it is offset).
2. I then loosened the dovetail, moved the saddle 180 degrees (now the knobs are on the right side) and re-attached the scope.
3. As I thought it would, it now falls to the right (because the scope is now off-set to the other side)

If it was the scope that was heavy to one side I would have expected it to continue to fall to the left, but the direction changes with the saddle - so that 0.25" off-set is what I think is causing the problem. If I could get it centered, I could then use the position of the guidescope (or the CW on the underside of the scope) to unbalance in either direction as much as needed to keep the gears meshed, but as it stands it always pulls to one side (and a lot harder than what seems reasonable - but I am not and expert in this - just what it feels like to me)

I think I will investigate a different saddle and see if Anthony (ADM) can confirm the centering of the dovetail in the saddle. If not I may have to try tube weights or just live with it.

Does my little experiment and conclusion seem reasonable? I rather enjoy trying to work some of these things out - just kind of the way I am.

Thanks,

Chris

Post Extras Print Post   Remind Me!     Notify Moderator

Entire thread
Subject Posted by Posted on
* CGEM DX dec balance issue cclark 09/03/12 10:44 PM
. * Re: CGEM DX dec balance issue EFT   09/04/12 10:33 AM
. * Re: CGEM DX dec balance issue DaveJ   09/04/12 08:22 AM
. * Re: CGEM DX dec balance issue Jim Romanski   09/04/12 06:03 PM
. * Re: CGEM DX dec balance issue cclark   09/04/12 08:44 PM
. * Re: CGEM DX dec balance issue dksolar3294   09/07/12 04:02 AM
. * Re: CGEM DX dec balance issue cclark   09/07/12 04:51 PM
. * Re: CGEM DX dec balance issue dksolar3294   09/08/12 03:15 AM
. * Re: CGEM DX dec balance issue cclark   09/10/12 05:15 PM
. * Re: CGEM DX dec balance issue dksolar3294   09/13/12 02:56 PM

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