Need help interpreting my PHD logs

[Datalord]

Hey,

I've been having some issues getting the guiding I want to have. I simply can't get round stars at 10 minutes, which is infuriating, because I achieved 15 minute subs with my old setup. I'm hoping someone can help me determine why this is.

I drift aligned, and the guiding assistant placed my PA error at 0.4'.  Help?

I've attached the log here: PHD2_GuideLog_2018-02-24_022821.txt

[kens]

Your biggest problem is dec backlash. Guiding assistant has an option to measure that.

You should guide declination in one direction only - the direcction depends on which way it drifts.

You should also dither in RA only

[SteveA]

Certainly can see some dec backlash as Ken mentioned.

However...just wanted to ask you how your set up has changed? Clearly this is an issue potentially introduced by new kit and that may well hold the key to the cause of your degraded guiding performance.

Next outing, try longer exposures which might smooth out some of the effects of less than optimal seeing.

Steve

[Datalord]

3 hours ago, kens said:

Your biggest problem is dec backlash. Guiding assistant has an option to measure that.

You should guide declination in one direction only - the direcction depends on which way it drifts.

You should also dither in RA only

The guiding assistant did say that I should do North only, which I tested out. What confused me to no end about that was that my 10 min exposure of that worked better than doing both directions, but on the graph the curve just went out of the screen over those 10 minutes. How can I get fairly round stars if the dec graph runs into 8" over that time?

1 hour ago, SteveA said:

Certainly can see some dec backlash as Ken mentioned.

However...just wanted to ask you how your set up has changed? Clearly this is an issue potentially introduced by new kit and that may well hold the key to the cause of your degraded guiding performance.

Next outing, try longer exposures which might smooth out some of the effects of less than optimal seeing.

Steve

In fairness, the old setup was a different mount and scope, but that setup was a Nextstar, which should definitely not be as good as the CGX. So, apples to oranges, but the result was I had very long good guided shots.

[Datalord]

18 hours ago, kens said:

Your biggest problem is dec backlash. Guiding assistant has an option to measure that.

You should guide declination in one direction only - the direcction depends on which way it drifts.

You should also dither in RA only

Btw, how do you determine that it is dec backlash I have from the graph? And is this to be expected from a mount like this?

[kens]

Dec backlash is pretty standard It manifests as a lot of corrections that do not cause the mount to move at first then to move to the opposite side of the graph where the cycle starts again. If your graph drifts off screen you should try reversing your guiding direction. However, it could also be that you have a very large aount of backlash and the gears are drifting between the engagement points. But if the drift is from PA error then guide in the opposite direction to the drift. By the way, in this situation it can be beneficial to not have too good a polar alignment so you get a clear drift in one direction.

You can use PHDLogiewer to look at your guide logs

 

[Datalord]

I did use the log viewer, I just didn't know what I was looking for. :-) 

I'll calibration assistant said that I might have a problem correcting South, so I should only correct North. Should I then do the drift alignment and make sure the Dec trend line is slightly below center? 

[kens]

The direction doesn't atter as you'll get backllash in both directions. Just set the dec guiding direction to correct for the drift whatever direction it is.