Problem with PHD2 Guiding Assistant

[A320Flyer]

Hi,

I'm trying to setup PHD2 for guiding. Everything is connected and I can calibrate and guide. However, when I run the Guiding Assistant to fine-tune the settings, I see a marked drift in the Ra axis (see attached screen grab and log file).

This is a brand-new EQ6R-Pro, straight out of the box.

I have pretty good focus on the guide star, good balance and reasonable PA.

Any suggestions as to cause and how to rectify would be very much appreciated.

 

Thanks

Bill

 

PHD2_GuideLog_2021-08-22_163523.txt

[Tomatobro]

 sidereal speed difference after 2 mins unguided with 13 arc secs drift . Should guide ok.

[A320Flyer]

55 minutes ago, Tomatobro said:

 sidereal speed difference after 2 mins unguided with 13 arc secs drift . Should guide ok.

Thanks for your response. Yes, it does seem to guide OK but I'm a little concerned that it should really track better than it does. All other screen grabs I've seen of a GA plot generally shows a random variance - not a dive like I've got. Should I be concerned?

[michael8554]

You should expect RA and Dec to drift during the Guide Assistant run, because guiding of both axis is turned off.

The Dec drift is due to PA error, 5arcmins is fine, 5.1 has just gone over the PHD2 threshold of acceptable.

RA drift is due to Periodic Error, every mount has some, even with PEC.

7 minutes ago, A320Flyer said:

screen grabs I've seen of a GA plot generally shows a random variance - not a dive like I've got.

A smooth line is good, variance would indicate the mount is wobbling on its own with the drives off.

Michael

Edited August 24, 2021 by michael8554

[Tomatobro]

If the RA speed is slightly slow or fast the star will drift East or West over time when the mount is unguided. Mounts with RA encoders track pretty well unguided but even they will drift a little over a long time.  The difference is they are another £3.5k over the EQ6.

Simple rule is zoom into one of your FITs images. Are the stars nice and round? If yes then all is ok.

[smashing]

As above the guiding is turned off when the guide assistant is running so yes it will look like that 

[A320Flyer]

Thanks for all the help on this.

I used PHD2's Polar Drift Align routine to get better PA. I then re-ran the GA. I let it run for longer than the minimum recommended 2mins and I noticed that the RA drift line started to come back on itself (see attachment). This indicated to me that the RA drift was primarily down to PE.

So I used EQMod's Auto PEC routine to record a PE curve and play it back as PEC. I then re-did PHD2's GA and this gave almost perfectly flat RA and DEC drifts (albeit with the general raggedness caused by seeing). 

I followed this up with an imaging session where guiging RMS was consistently less than 0.5arcsec. 🙂 

Again, thanks for all the help.

Bill