PHD2 Guiding issues

[matt_baker]

Anyone got any idea what's up with my guiding? Calibration took about 5-10 minutes to complete too. Moved about 1.5 pixels per step, everything was on defaults but probably should have run guiding assistant looking back

PHD2_GuideLog_2020-06-25_225201.txt

 

Edit: Looking at it, it seems like there's some DEC backlash and possible RA PE? How should I combat the backlash since my balance was pretty good in DEC?

Edited June 26, 2020 by matt_baker

[Ken82]

First make sure pixel size is correct for camera and focal length is right for guide scope. Then run “guide assistant” for a few minutes. 
 

The guide assistant will tell you how much backlash is in DEC. If it’s too large you may need to guide in one direction only or a mechanical adjustment may be required. 

[michael8554]

Hi Matt

I see you're using EQMOD, so straight away I looked at your Guide Rate.

For some reason EQMOD defaults to a ridiculously low Guide Rate, 1.5arcsecs/sec in your case, which is why you have a huge Calibration Step size and 19 Calibration Steps.

Set it to 10arcsec/sec and see how it goes.

Remember to Calibrate close to south and Dec 0, and nudge north until you see the guidestar move, which takes up the Dec backlash, BEFORE you Calibrate.

Once you have a good Calibration you can use that for the rest of the night, PHD2 will compensate for targets at different Decs.

Michael

Edited June 26, 2020 by michael8554

[matt_baker]

Still not so sure what's up with the mount.

It's belt modded so I wouldn't expect this much dec backlash whatsoever. I can see quite clearly that there's PE with the RA but that's okay, it's just the spikes in DEC that bothers me.

I calibrated SW near dec 0 since south is obscured for me, nudged it north to clear it and changed sidereal rate to .5x. I did enable backlash comp and try various values but to no avail.

I know my RMS values are quite okay and under 1" but it's just annoying to see the spikes in the DEC axis appear.

PA does say 17.7' but I checked in guiding assistant and it was around 1'

Anyone able to help?

 

Matt

PHD2_GuideLog_2020-07-10_232926.txt

[michael8554]

8 hours ago, matt_baker said:

changed sidereal rate to .5x.

Guess you mean Tracking Rate.

I see the Log is for the 10th, is that your latest one?

8 hours ago, matt_baker said:

I did enable backlash comp and try various values but to no avail.

I don't see any sign of a Guide Assistant run, PHD2 uses that to determine the Backlash Comp setting in PHD2, you don't try different settings..

Or are you referring to the Skywatcher Backlash Comp settings ?

Don't use them, they seriously interfere with PHD2.

8 hours ago, matt_baker said:

PA does say 17.7' but I checked in guiding assistant and it was around 1'

No Guide Assistant run in the log ?

Guide Assistant would have recommended Minimum Move settings too.

Dec looks to be lurching across the axis on its own, which could be because you have the Skywatcher Dec Backlash enabled ?

If not, then establish a PHD2 Backlash Comp setting by running the Guide Assistant.

If that doesn't help, consider balancing Dec heavy in one direction to keep the Backlash at one end of its travel.

Michael

Edited July 18, 2020 by michael8554

[matt_baker]

14 hours ago, michael8554 said:

Guess you mean Tracking Rate.

I see the Log is for the 10th, is that your latest one?

I don't see any sign of a Guide Assistant run, PHD2 uses that to determine the Backlash Comp setting in PHD2, you don't try different settings..

Or are you referring to the Skywatcher Backlash Comp settings ?

Don't use them, they seriously interfere with PHD2.

No Guide Assistant run in the log ?

Guide Assistant would have recommended Minimum Move settings too.

Dec looks to be lurching across the axis on its own, which could be because you have the Skywatcher Dec Backlash enabled ?

If not, then establish a PHD2 Backlash Comp setting by running the Guide Assistant.

If that doesn't help, consider balancing Dec heavy in one direction to keep the Backlash at one end of its travel.

Michael

Sorry, here's the other file with the guiding assistant

PHD2_GuideLog_2020-07-11_225501.txt

[michael8554]

PA is 2arcmins or less according to the Logs -  too good maybe, a bit of drift would keep PHD2 Dec guiding in one direction, which will avoid Dec reversals which will take a long time due to the backlash.

Here's some of your Dec guiding:

Running happily at well below 1arcsec, then goes well past the Min Move limit (arrowed) and kicks off with those large pos and neg spikes.

My previous suggestions about balancing to keep Dec corrections in one direction apply.

Michael

 

[matt_baker]

8 minutes ago, michael8554 said:

PA is 2arcmins or less according to the Logs -  too good maybe, a bit of drift would keep PHD2 Dec guiding in one direction, which will avoid Dec reversals which will take a long time due to the backlash.

Here's some of your Dec guiding:

Running happily at well below 1arcsec, then goes well past the Min Move limit (arrowed) and kicks off with those large pos and neg spikes.

My previous suggestions about balancing to keep Dec corrections in one direction apply.

Michael

 

Just checked my backlash settings on the mount and it's all set to 0.

I'll have to go out when I next can and try to properly get the guiding sorted out, probably do some PEC for the RA too.