Celestron CGEM Mount (9.25 EdgeHD)

[Benik]

Hi Astronomers,

Does anyone have any experience with the Celestron CGEM Mount?

More specifically when it spins on the Declination Axis it seems to hit a stop, where the motor just stops but makes an unhealthy noise (Grrrrr).

The stop is not consistent in its location and sometimes its one side other times there is a stop on both sides!

All input welcome :D

Cheers
Ben

[SA_Dolphin_22]

Evening, had a similar issue with a CGEM 5 where it sounded like the motor was binding and would then stop, worked out that it was off balance (just) whilst close to the weight limit and only when near or approaching horizontal. Have a look at what your kit weight is adding up to and then recheck the balance. seemed to work out for me :D W/O 132mm and 68mm MIZAR refractors with a NIKON 5100.

[Camelopardalis]

My AVX is the same - it doesn't spin freely and (seemingly) endlessly around. There is a physical stop at either extreme.

What I'd suggest trying is (obviously without any scope on board) disengaging the clutch and spin it around til you hit the stop. Note where it is. Then spin it around until it hits the other stop. Note the position. Then Spin it to the mid point. Engage the clutch. Then use the motors to centre. Power off. You should then not hit the stops so long as the clutch remains engaged.

I'm just speculating, but I don't think there's much extension past the meridian in either axis, hence the stops. I've never noticed this behaviour with my EQ6 though, so they must be engineered differently.

Edit: my bad, I was speculating as to whether they were the same, clearly not :)

[Benik]

Thanks Chaps!

I will give your tips a whirl and see if that helps :thanx:

[Tony_]

The CGEM does not have physical "stops" in either axis - it will spin all the way around.
Also unless filters are applied in the hand controller it will continue to track in RA until the telescope hits the mount.
My CGEM also occasionally makes a strange noise in the RA axis - it continues to track but it doesn't sound good and it has a bit of a vibration. It does (rarely fortunately) do it even when the mount is well balanced and even with only an 80ED on it - which isn't heavy. It doesn't happen often.
I suspect there is something in the worm gears or bearing causing an obstruction, but the only way to confirm that is to pull the mount apart. I intend doing this soon to lubricate it and clean it.

Tony.

[DannyV]

Hi,
Over a year ago, I Hyper-tuned my mount, and used the 'Supergrease' that was recommended in the video. In February this year I heard noises similar to those you're describing and decided to pull it apart and have a look.

It turned out that there was no grease in the sealed ceramic bearings that had been supplied as additions to the kit, and no grease in the bearings that I had packed myself (and coming from a farming background, I know how to pack bearings).

The hot days had simply melted the grease away, even though my telescope is in a protected dome with a ducted air conditioner feed from my room.

I repeated the Hyper-tuning with high quality local bearings, and high temperature grease. The mount works beautifully now.
:)