Clunky Dob rotation

[jasmax]

Need some help! Just got my Skywatcher 10 inch GOTO Dob couple days ago and when I try to manually move it close to view before activating GOTO it is quite stiff/rigid and makes terrible clunking noises like its stuck on something. It seems to move ok when only using the GOTO.

Being my first real scope I have no idea what is wrong with it and how to fix it! Any advice would be really appreciated.

[kustard]

My first question would be to ask if the mount is designed to be both a GOTO and a manual system. If it's not then you might find you are pushing the mount over the worm teeth. If it is designed for both then there are some options.

My Orion XT14g is suffering a similar problem (it's a synscan system so a skywatcher in essence) to the point where the GOTO is now not working and pushing it manually is very noisy. It's currently at the service shop getting checked out.

I suggest you contact the place you bought the scope from and the manufacturer to see if there are some adjustments you can make to the clutching system before you do any thing else. I was able to get a clutch adjustment procedure but in my case it didn't help, thus the mount being in service.

HTH,
Simon

[knightrider]

*Thread revival.

I have the same scope, skywatcher 10" GOTO dob, and as described it does the same thing only on the azimuth. Altitude movement is fine.

It feels like it is hopping over the gear teeth and quite difficult to move, so much that it would even drag the feet around on the ground given the surface is loose or not grippy enough.

I was under the impression you could move it manually if needed.
Quoted from the SkyWatcher site "The patented dual encoder design allows the telescope to be moved manually whenever the user wishes - but with no need for re-alignment!"

Unless they only mean slewing manually with the hand controller??

Does anyone else have the same experience or is this a minority issue?

[knightrider]

Well I fixed it. Spent all night pulling it down and reassembling repeatedly.

The juttering was actually the worm gear jumping over the cogs.

I had to pull down the base and azimuth motor to get to the clutch plates. The plates were sandwiching the gear plate too much not allowing it the movement it needing to be moved by hand.

It shouldn't of been like that from factory but oh well, it's given me the chance to get to know the scope better.

I'm not entirely sure if it should be tighter or looser when moved manually but it seems to be firm enough to allow the goto to do it's job. I don't think these would ever be as smooth moving as a full manual dob (I haven't felt one before). But it seems fine to get away with without power but it would be better used with power given the manual movement is a little firm to be smooth.

I found some play afterward in the rotation of it from the spindle hole of the top clutch plate, which I tried all night to get rid of but it persists to stay there. It hasn't seemed to have affected the accuracy of the goto though so I guess I'll just live with it. May have been my fault, I loosened the spindle hole in the plate a little since it was biting on the spindle so tight, I did my best to centre punch the top clutch plate back firm which I was mostly successful but the degree movement stayed after reassembling.

Maybe it's just the nature of the manual movement of a goto dob. It wasn't there previously because it was insanely tight and unmoving.

[Steffen]

Considering a GOTO Dob myself (at some indeterminate point in the future) I find this very interesting. Is the clutch adjustment easily reachable, without stripping down the mechanism? I reckon the clutch should be *just* tight enough to prevent slip during motor driven operation.

Cheers
Steffen.

[knightrider]

Well there is a clutch adjustment screw just underneath the encoder box, but this didn't help me when i took it through it's full range of adjustment.

I'll attach the pdf for the clutch adjustment nut.
131544

Here is the thread that helped me to pull the base and motor and clutch plates down.
http://stargazerslounge.com/topic/156784-stripping-a-skywatcher-dob-auto-mount/

He has pictured it all in steps which was really helpful.

I read your comment lastnight and I decided to pull it down again this morning(another 3 times) to get the clutch plates gripping just enough for drive and smooth enough for easy movement.

The culprit for my situation was the nut and spring washers just above the clutch plate, which required me to remove everything to get to.

Getting the right amount of pressure was a trial and error exercise. Now I also have some minor adjustment in the clutch adjustment nut if I want more pressure. The degree of slop has also gone now I was able to loosen it up some more too.

Azimuth movement is now easier to shift than the altitude! and still able to grip enough for the azimuth motor :)

Once you get to know what your doing pulling it down, it may only take 10mins or less to pull apart.

[Steffen]

Great, thanks!

Cheers
Steffen.

[knightrider]

Glad to help :)