CGEM mount jumps when tracking

[brisen]

I have a new (4 months old) CGEM mount which has an issue with tracking. When using tracking, the mount appears to stick and then release, causing the object in the eyepiece to jump constantly as the mount tries to track. These jumps occur every couple of seconds and the scope is definitely not tracking at anywhere near sidereal rates as the object moves out of the field of view within about a minute.

In an attempt to isolate the problem I have done a factory reset and the problem continues even after this. I would like to start using the scope for astrophotography but this is out of the question with the way the mount is currently performing. I really don't want to have to send it back to Celestron unless I really have to. but am starting to wonder if I have received a dodgy mount that has issues.

Has anyone else experienced this issue with a CGEM?

Brian

[Logieberra]

Brian, member 'Gem' or Grant has one too. You might like to contact him.

[raymo]

I'm not familiar with the CGEM, but your problem sounds very much
like something is slipping, either the R.A. manual lock is not tight enough, or assuming that the CGEM uses gears in it's drive train, one
or more of them is slipping on its shaft. If they are easily accessible, I
suggest that you check tighten them first, before returning the mount for repair.
raymo

[SteveInNZ]

The first thing that I would check is balance in both RA and Dec axis. You can see those symptoms if the mount is too heavy in either axis. I noticed that my CGEM seems more susceptible to that than my previous CG5.
You can also get similar symptoms if the mount is perfectly balanced in RA. It needs to be slightly biased in one direction or the other to keep the worm constantly engaged.

Steve.

[toc]

I have the CGEM and have not noticed this. I would first check how well the axis move by hand, and see if there are any binding points. If that is ok, then I would suspect a problem with the gears - might be time to return it :(:(

[brisen]

Thanks everyone. I will take it out again when the cloud clears here again and have another look. I will also check the balance again.

Brian

[Poita]

The CGEM Yahoo group is a great resource also.

[edwardsdj]

Hi Brian,

I have been using the CGEM for around 4 years and have occasionally experienced this issue. It is always due to poor balance for me. I found I had to add an additional counterweight to properly balance my C11 with heavy accessories.

When I get a new accessory my procedure is:

1. Set up indoors with all accessories I intend to use attached and get the best balance I can when pointing in any direction. I find I can't get it perfect in all orientations so I find the best compromise.

2. Return the mount to the index marks and tighten the clutches.

3. Note the positions of the counterweights and tube in the saddle.

I rarely release the clutches when setting up outside. I just return the couterweights and OTA to the same position and go with awesome goto and tracking precision!

Hope this helps.

Take care,
Doug

[brisen]

Hi Doug

Thanks for your advice, I will have to wait until the cloud disappears again to take the scope out and see if it now works. I have spent some time inside with it today getting it balanced with a little bias and then marking where the counterweights are etc.

Brian

[brisen]

Hi All

I took the mount out and tried biasing the balance slightly as suggested and this made no difference to the jumping so effectively ruled out the balance aspect. Just as I was about to pack up in frustration, I told the mount to go home via the hand control - nothing, it was frozen in place. Repeated attempts at pushing direction buttons failed to move in RA, but only in the one direction.

This failure was not making me happy so I rang the warranty people as soon as they opened on the Monday to return it with instructions to fix the problem. It turns out the control board was faulty and this, along with the motor was replaced. The mount is back later today and just on cue so is the rain and cloud for the next week. I now wish I would have bitten the bullet earlier and sent it back to be fixed sooner.

Brian

[edwardsdj]

Hi Brian,

Great to hear you were able to get your control board and motor replaced.

Take care,
Doug

[Gem]

Good to hear you will be up and running again. I have found the CGEM a good mount once I got my balancing ok. :)