Dither chaos

[Horwig]

This is the guidelog for last night's session. Mount is an AZ-EQ6 with an FSQ106 on top

The beginning of the trace, and the section just after 23:45 is what I'd expect with this rig, the rest of the trace is something I've not experienced before, looks like the dither is causing an oscillation which is not dying down.

This is a well sorted repeatable setup, which just works, the only change last night was the addition of an extension tube between the mount and tripod, (but why would that make any difference?)

Went on to try tweeking PHD settings, even stopping and restarting tracking on the mount, nothing worked. Didn't restart PHD though., suppose I should have.

Anybody seen anything similar, am I suffering mechanical or software gremlins?

 

Huw

[Tommohawk]

It looks like it goes wonky after the first dither, even more wonky after the second dither, but then settles after the third dither, and then goes off again after the fourth dither  - am I seeing that right? Not sure what to make of that TBH though.

Maybe something to do with balance? If the RA has slight play and is very evenly balanced ie not at all East or West heavy it might cause it? Cant see that the extension would make a difference, assuming all secure.

 

[Horwig]

33 minutes ago, Tommohawk said:

It looks like it goes wonky after the first dither, even more wonky after the second dither, but then settles after the third dither, and then goes off again after the fourth dither  - am I seeing that right?

 

 

Yes, you are reading it correctly, never seen anything like it, the only difference in the setup of the kit was the scope was mounted slightly front heavy, but that would not affect RA would it?

Will have another go tomorrow night, tonight forecast cloudy.

 

Huw

[Tommohawk]

Agree front heavy should only affect DEC. That said if the DEC swings around a lot I think it can affect RA a bit - but it doesnt look like that.  I found myself looking for the correction pulses - but although the box is ticked I cant see the corrections on the graph. Just checked one of my logs and its the same. How do you get the corrections to show I wonder?

Edit - just realised the corrections do show. Its just that the trace needs to be stretched a bit to see them well. I wondered if perhaps your correction pulses were dropping off after dither, but they look OK.

Edited April 12, 2020 by Tommohawk
Being dim