PHD 2 RA correction issue

[5haan_A]

Hi,

 

Has anyone encountered this problem with PHD2?

 

It says that it cant make the necessary corrections in RA. 

 

Initially I had thought that it might be an issue of polar alignment, however this problem has cropped up on multiple nights. It's quite quick to come up, taking less than a minute for the error warning message to pop up, and then not long after it loses the star I was tracking.

 

It means that I cant take any exposures longer than 10 seconds, as star trails begin to show.

 

I am using a skywatcher eq6-r pro mount. The error message that comes up says that the problem may be caused by cable snags or a mechanical issue with the mount. I am sure there are no issues with the cables, the mount is only 3 months old, so I cant imagine that the issue would be with that.

Thanks,

[Star101]

Not sure why you are getting this.

I would reset the configuration of PHD2, reboot the mount ( take power out and re apply ) Then recalibrate PHD2. 

I would also calibrate closer to the horizon than the high points of the sky.

That's what I did when I used my NEQ6 and it usually worked. 

Good luck.

[5haan_A]

 

7 hours ago, Star101 said:

Not sure why you are getting this.

I would reset the configuration of PHD2, reboot the mount ( take power out and re apply ) Then recalibrate PHD2. 

I would also calibrate closer to the horizon than the high points of the sky.

That's what I did when I used my NEQ6 and it usually worked. 

Good luck.

Hi I'm not sure why I'm getting this problem either.

 

I haven't tried recalibrating phd2 yet so I will give it a go later tonight if I get a chance. 

 

Is there a way to confirm my mount doesn't have a mechanical issue as well?

 

 

[Star101]

Apart from moving the mount via the left/right up/down arrows?

If they work, I'm sure it's basically OK.

[5haan_A]

Yeah I can move the mount about using the eqmod just fine.

 

I'll give it another go tonight.

 

Best, 

[Danjc]

I can’t help but have also had exactly the same issue with my HEQ5 both pre and post belt mod ! 

On the few occasions I got the message I carried on as normal without any problems even doing 600s subs no problem. 

I just put it down to one of those things but I’m sure there’s an answer somewhere.

 

Dan.      

[5haan_A]

Hi Dan,

Glad to hear I'm not alone. I wish I could get to 600s at the moment I cant do more than 15 without it causing some sort of star trail.

 

Really not a good situation, and very strange how phd2 seems to not be able to move enough in RA. Especially because slewing with cartes du ciel does usually work. 

[michael8554]

Your screenshot shows that PHD2 is guiding, and it has issued a RA pulse of 2500 ms, 7.7 pixels, and a Dec pulse of 2500mS, 8.2 pixels. 

These are huge corrections, normal guide moves are ideally less than 1 pixel.

Read and apply these guidelines:

https://openphdguiding.org/phd2-best-practices/

Michael 

[david_taurus83]

What guide scope are you using?

[Thalestris24]

Hi Shaan_A

FWIW belt driven mounts require perfect balance in all three axes. It could be that yours is sufficiently out of balance that PHD2 can't correct it. However, that is likely to have shown up as a problem during calibration. I'd repeat calibration just in case. Another possibility is the belt tension allowing slippage. I would expect a new mount to be good to go but you never know. Power/connections maybe another source - are you using mains power? You don't say what scope you have? I assume you aren't over the 20kg payload limit...

Louise

[bottletopburly]

If your using Eqmod what speed have you set dec and Ra  not sure what it’s called default is 0.10 for both try increasing these parameters if set to default, I’m sure someone will tell me what the correct name is .

[5haan_A]

On 28/08/2019 at 09:22, david_taurus83 said:

What guide scope are you using?

I'm using a zwo 120 mini. I must add that this set up has worked perfect fine in the past with no issues. 

 

On 28/08/2019 at 14:57, Thalestris24 said:

I'd repeat calibration just in case. Another possibility is the belt tension allowing slippage. I would expect a new mount to be good to go but you never know. Power/connections maybe another source - are you using mains power? You don't say what scope you have? I assume you aren't over the 20kg payload limit...

Louise

I'm going recalibrate again this weekend when I have the time to move the set up to a suitable location to see some stars at the right DEC to calibrate. 

Power wise there are no issues. The battery I use has been great in the past and it supplies the right voltage for a good amount of time, I have never managed to run out of juice. 

I'm using an esprit 100, it's reasonably heavy, but well within the capacity for what the mount should handle.

 

I had a very good chat with a chap from dark frame optics today. They service skywatcher mounts and can tune your mount up. His suggestion was that my mount may either be too tight, as it is quite new, or a number of other issues that arent too bad. 

I'm hoping that the problem is software related and not hardware. I'm going to try and get as much data as I can out of PHD2 and share it on here and with the helpful chap from Dark Frame Optics with the hope that I may be able to get some sort of solution. 

[Freddie]

Are you sure your PA is good? If it was, you would only expect to need big guide commands to RA if it was a mechanical or software issue. From the screen shot, the DEC error is greater than RA so that would indicate that your PA is somewhat off.

There are some interesting comments about Dark Frame on the forum that would be worth reading.

[Photosbykev]

I used the built in 'guiding assistant' wizard to fine tune my guiding. It suggested a few minor parameter tweaks that certainly improved the guiding for me

[Anthonyexmouth]

Are you calibrating every time you set up?

[5haan_A]

14 hours ago, Freddie said:

Are you sure your PA is good?

There are some interesting comments about Dark Frame on the forum that would be worth reading.

Yeah my PA was good. Did it in sharpcap until it said excellent, which for those that have used sharpcap to to PA takes some patience to get to.

 

I had a read just now about what some people have experienced with Darkframe optics. I must say my experience over the phone doesn't match up with what was said. Dave and I spoke for a good 20 minutes and he was more than helpful. Admittedly I haven't sent a scope to him so I cant comment on the full service.

 

8 hours ago, Photosbykev said:

I used the built in 'guiding assistant' wizard to fine tune my guiding. It suggested a few minor parameter tweaks that certainly improved the guiding for me

What kind of tweaks were these? 

 

5 hours ago, Anthonyexmouth said:

Are you calibrating every time you set up?

Unfortunately yes, until I build a pier. 

 

 

[discardedastro]

I've had similar issues and it all came down to balance and PA accuracy.

Balance your mount and scope as perfectly as you can. If you're using a Newtonian and don't need to look down the scope (imaging use only), rotate the 'scope in its tube rings round so that the focuser points to the counterweights to improve dynamic/radial balance. Take your time on this and get it right, especially for the RA axis.

Start with PHD2's static polar alignment to get a rough PA, and then use the drift alignment to get it spot on. Just resign yourself to spending 20 minutes before you do any imaging doing that, just as you'd spend 5 minutes collimating if you're using a Newt. Drift alignment was a bit confusing initially but has gotten me to very good PA very quickly in recent nights.

There are other good checks to do - use PHD2's manual mount controls to ensure you can actually see movement in all 4 axes. PHD2 can also do a star-cross test, though that's not quite worked for me sometimes even when my mount's set up right. These will confirm good motion via your guide input.

PHD2's guiding assistant is also well worth doing. I'd do a low Dec calibration (and do the meridian flip calibration, too, so you get that done at low Dec), then use the guiding assistant (measure for 3-5 minutes) to work out what sensible min-move parameters will be and measure the relevant backlash.

[Photosbykev]

13 hours ago, 5haan_A said:

What kind of tweaks were these? 

 

 

FRom memory it gave me a new Minimum Move (pixels) of 0.36 rather than the default and also calculated the backlash of the drive. I didn't apply the backlash correction, not sure why not, but it made sense not to when I was playing with the numbers

[david_taurus83]

Check your PA with Sharpcap  carefully. If you carry out an adjustment without pressing next at the right time it can mess the result up. I done it myself a few weeks ago. If you follow the guide carefully, get an excellent result, swing back to home before closing Sharpcap to confirm your still getting a good result. As above, your Dec error is worse than your RA. If you were well aligned Dec wouldnt move much at all. The belt driven EQ6 is a good mount. It will easily guide within 1 arc second.

 

Personally, I'd uninstall PHD and reinstall again and set up a fresh new profile. At least this can be done during the day.

[5haan_A]

So last night I had some success finally. I basically took on board everything that has been said in here and managed to guide with PHD2!

 

I made sure that my PA was as good as could be. 

I reinstalled PHD2 and recalibrated. I have attached the calibration data. I still wasnt happy that I got an orthogonal error of 14. PHD2 was saying that it should be below 10, but it was close enough.

I then managed to guide without major hiccups. I have attached some log data also. The only issue I had throughout the session was the images PHD2 were taking were variable. There was some sharp images were the stars were all visible through the findersope and it was happy, and there was some dim images were all but the brightest stars through the finder would disappear. This meant that there was significant star mass change from frame to frame. Not ideal but it meant that PHD2 would lose sight of the star for let's say 1 frame in three. It would pick it back up again the frame later so it was actually fine and didn't affect the session too much. 

Anyway thanks for the help, and if any of the info I provided can be used to give some more feedback it would be appreciated. 

[Thalestris24]

Hi

You should show your star profile and bullseye target from the view menu. The calibration doesn't look too good for a belt drive. Maybe guide scope flex or a balance issue.

Louise

[5haan_A]

5 hours ago, Thalestris24 said:

Hi

You should show your star profile and bullseye target from the view menu. The calibration doesn't look too good for a belt drive. Maybe guide scope flex or a balance issue.

Louise

Hi Louise,

Plenty of room for improvement for sure.

 

I was running the guiding with a slightly unbalanced scope so to engage the RA gears more, I'll try a more balanced set up next time and see if the numbers improve.

 

Best,

 

Shaan

[Thalestris24]

4 minutes ago, 5haan_A said:

Hi Louise,

Plenty of room for improvement for sure.

 

I was running the guiding with a slightly unbalanced scope so to engage the RA gears more, I'll try a more balanced set up next time and see if the numbers improve.

 

Best,

 

Shaan

I thought you had a belt drive?

 

[5haan_A]

Just now, Thalestris24 said:

I thought you had a belt drive?

 

I do indeed.

[Thalestris24]

So you need to be in perfect balance. No concern about engaging motor gears. The bullseye target will show you if you have a balance-related drift.