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Jumping stars

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I have a 8* SCT on a avx mount. This never happened before but when i do my star allignments i notice that the  alignment star star ever so slightly keeps moving back and forth in the eyepiece. More so when i pint the scope in southerly direction. Do you smart people have any ideas what the idea could be? Is it a inbalance issue? or circuit issue in the mount? Would this be a major issue in AP?


Any ideas  



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The obvious is play in the gear train and an amount of inbalance. In effect the scope "flops" to take up the play in the gears and the motor catches up and the whole thing starts over again.

Could actually be that the scope is too well balanced, people often impart a degree of inbalance so that the gears remain in contact on one face at least.

You could try that - there is if I recall a preferred direction for this imbalance to be, but not sure of which direction.

There should also be an adjustment for you to manually tweek/tighten the gears, someone was asking about an AVX service a day or two back and I suspect they will know. I suppose it could be caused by the stuff that Synta put in the drive as grease, it tends to be somewhat heavy, more suited to steam locomotives then an astronomy mount. That might be sticking and causing the jumping.

I would expect it to be a "fault" as such but a problem with the setup of the drive train, and although imbalance might be the simpler to sort I would guess that it is the gear meshing that needs setting a little better

Concerning AP, just about any unwanted movement is a problem in AP.

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Thanks for reply. 

Will try initially to imbalance a tad more. Which directions should inbance be? For example if scope is facing south direction, should the counter weight be "more" towards scope or away for example?

If its another issue i am not tempted to open the mount up though. Jack of most trades, master of none! :) 



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After the few ideas I was looking at CN and there was a post over there which happened to mention similar on an AVX mount.

The relevant paragraph reads:

Looking at some video clips, I see how freely the RA and DEC move after tuning. Hmm?? My AVX isn't smooth like that. I thought it was normal to have a little grip. Now I see this is in-fact an issue. So, I believe the AVX may need a little cleaning and a good inspection.

The first sentence refers to the hyper tuning they did of a different mount they purchased. I presume that the "little grip" manifests as the jumping that you refer to.

Seems very little can be done as there is no tuning kit and not a lot can actually be replaced so not able to put better items on. One person did clean the heavy grease off and is presently using oil not grease to provide lubrication. The catch being it disappears relatively quick.

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Its still under warranty,(about 10 months to go) So may give them a call on tuesday?  Dont want to risk losing the warrenty by opening it up. 

Will try adjusting the balance as suggested  next clear evening. Is it worth considering another mount to the AVX? 


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Hi these images of m10 (10mins) and m80 (18 mins) where taken last night with 8"SCT 2minute subs unguided, 

DSS stacked 50- 80% of lights taken. Thanks to you people  mentioning my balance issues seems to have improved things. Although last night was a good night for imaging. 

M80  is the most southernly  imaged taken so fay moving along the roof! :) 



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