Tracking drop

[asgr]

Hi All,

 

I'm getting a fairly repeatable problem where after a few hours of faultless tracking performance with my DDM60 pro, I start getting persistence position errors after about one minute of tracking. Checking the motor tuning I can see the RA axis (usually) is building up a tracking error over time until it stops tracking entirely. Again, at the start of the night I don't see this behaviour.

 

Has anybody else had this trouble? Any advice would be appreicated (I'm currently assuming it is an issue with balance or tuning).

 

Cheers,

 

A

[GeorgeCarey]

The first thing to do is to turn on current logging. Inspecting the log files can often pin down the problem.

[asgr]

Thanks for the suggestion George. Today I decided to do some longer controlled tests with the logs all turned on. Re-doing the balance and changing the tuning to small OTA (I had my own tuning before) I can see axis 1 (RA) rise to about 1.3A and then drop back to a steady 0.7A. Axis 2 (Dec) is a steady 0.2A. This seems to be maintained over a couple of hours now with no tracking drop.

 

I guess the problem before was one of (or a mixture of) balance and tuning. I think I had achieved my previous balance in a fairly pathological alt/az (close to zenith orientation), so I have made sure my new balance is well within 0.5A for all orientations. This means it is "perfect" nowhere, but pretty good everywhere.

Cheers,

Aaron

[MartinN]

Hi Aaron, hi George,

 

I encountered the very same situation last night, and a few nights before, and some weeks ago, too.

Balance was good, but with 1,5A values, supposedly due to the weight of ASA12N+CCD-Camera+Filterwheel and balancing counterweights.

Last night I noticed, that the red led of the laser switch at the RA mount baseplate blinked, when the problem occured.

Though I stopped Autoslew, disconnected and unpowered the mount, the blinking red led showed up again after powering the mount. When connecting USB, the blinking change to usual contant light, but the tracking problem occured again after a few minutes.

When the problem started, the mount began to make some strange noise like jarring, buzzing, rattling. When tracking stops eventually, it seems like the motors are not powered any longer, and the button in Autoslew, for turning motors on an off, has no effect at all.

 

Maybe I have to inrease the "Measure Time", and decrease "Step Size" and "Test Current" to get a more sinus like pattern (which is not so up to now) when setting motors on in Autoslew after powering the mount ?

Which values do you have with a rather heavy tube (and thus counterweights, or counterweights near shafts end) ?

 

Kind regards

Martin