Guiding Issues with MyT, QHY5II-L-M, PHD2

[Yizhou Zhang]

Hi all,

First of all, I am glad to be here and join the group. Have been a long time user for PHD and PHD2 and I really like it!

I am struggled with guiding with my Paramount MyT using PHD2 and QHY5II-L-M. Specifically I noticed that my mount guides fairly OK in some parts of the sky, while really bad in other parts. Mostly huge spike in RA. 

 

I am using MyT with SGP and PHD2, guiding with QHY5II-L-M with Atik OAG. The scope is at 915mm FL. Balancing was decent (loosing both clutches and scope will stay at any position).

 

I set everything up, PAed with TSX's TPoint model and Accurate Polar Alignment Wizard. Once done PA I switched to SGP and called out PHD2. I start calibrating at around home position, DEC ~ 0. I attached the calibration data here in case you guys find something weird:

Once done calibrating I let it guide for about 30 secs and guiding seems fine. Then I have SGP slewed to M81 to take data. I noticed huge spike (>1") in RA during guiding. See plot below. This is a guiding graph for about 10~15 minutes.

Since the guiding right after calibration was OK, I switched back to IC 434 which is closer to my calibration position and start guiding. The guiding looks much acceptable. Guided for about 30 minutes. The same scale as the previous graph.

I would like to go back to M81, re-calibrate PHD2 then guiding, but that's when clouds rolled in. However, I've encountered this issue two or three times in the past two weeks. I attached another guiding log on M81 I took eariler, which is guiding right after calibration. Same (even worse) spikes on RA.

I am not sure if this is a mechanical problem or the guiding problem, but I would appreciate if you guys can take a look and hopefully see some obvious problem and help me fix it. I appreciate any input.

Thanks!

Yizhou

[Andy Galasso]

Yizhou,

Could you please post a link to your guide log?

Andy

[Yizhou Zhang]

Hi Andy,

Sure. Here is the guiding log last night.

https://www.dropbox.com/s/u7chuoez629q85z/PHD2_GuideLog_2016-02-10_170349.txt?dl=0

From 19:13 there is a guiding for 15mins corresponding to the guiding with issues on M81 (high DEC).

From 19:35 there is a guiding for about half an hour with decent results, corresponding to guiding on IC434 (close to 0 DEC).

Thanks,

Yizhou

在 2016年2月11日星期四 UTC-6下午3:06:53，Andy Galasso写道：

[Andy Galasso]

Yizhou,

Thanks for posting the log.   Clearly the spikes are there at dec 69, but absent around dec 0.

It does not seem like PHD2 is either over correcting or under correcting.  We see cases where PHD2 is sending corrections in one direction, then the mount jumps in the other direction. I can't think of any obvious explanation for this.

I think there are a couple experiments you could try to see if we can get some more information:

 - try disabling guiding and see how the RA tracking looks unguided at dec 69.  You can disable ra guiding either by using the Guiding Assistant, or by disabling guide output in the brain, or by setting RA aggressiveness to zero.

 - try running a calibration at dec 69.   The calibration itself will show us how the mount is responding to guide pulses at dec 69.

Because the excursions seem to be coming from an external source (the guide star moves first, then PHD2 reacts), you may want to check for excessive RA backlash, or scope balance issues that may only come into play with the scope pointed at high declination.  I know that seems unlikely with such a high quality mount, but I figured is was worth mentioning.

Andy

[Bruce Waddington]

Hi Yizhou.  Any chance you're using something like ProTrack or any other software that would move the mount independently of PHD2?  Not that it has anything to do with your problem, but it would be a good idea to use either a dark library or a bad-pixel map.  

 

Bruce

 

---

--
You received this message because you are subscribed to the Google Groups "Open PHD Guiding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to open-phd-guidi...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Yizhou Zhang]

Hi Bruce,

PEC and Protrack are all off.

Thanks,

Yizhou

在 2016年2月11日星期四 UTC-6下午6:39:52，Bruce Waddington写道：