EQ6R-Pro runaway dec guiding

[Radu Marinescu]

Hello. I have a pressing issue that for some reason my guiding will not work properly. It seems like the declination graph is going absolutely nuts, sometimes fades away in total 300" error RMS while the right ascention graph stays settled into values like 0.5". What is very weird is the fact that after many attemts at restarting the mount or PHD2, the guiding started acting perfectly for some time, total rms of about 0.5" on both axis. And then I started imaging in NINA and well, the first dither went well, but after the second didther the DEC went nuts again. I again reconnected everything and the issue still occurs. 

I have attached screenshots of my guiding working as expected then DEC suddenly running away. I know this mount has backlash issues, but I don't thing they would ever cause this infinite going drop. It's simply like the mounts stops tracking DEC altogether, the stars drift visibly inside PHD2 image looping. Can it be some power issue or lack of proper comunication between PHD2 and the mount?

What can cause this issue?
Thank you in advance.
 

PHD2_GuideLog_2019-01-05_222245.txt

[wongataa]

I have seen something similar on my mount (a completely different one to yours).  When it happened I stopped guiding and recalibrated it.  After that the guiding had no issues and worked as it should.  I have no idea why it went funny and why it was happy after a recalibrate.  The initial and second calibrations seemed to be successful.

[Tomatobro]

What hemisphere are you located in Radu?  It looks like the mount has good polar alignment so the DEC motor is turned off. When it does a dither in both axis the mount tries to correct the DEC but its turning the DEC motor the wrong way.

Try using the setup wizard and see what that suggests as a basic setup

[Tomatobro]

Its been a while since I did this but I recall that if you do a calibration with the mount on one side of the meridian and  calibrate but your target is on the other side of the meridian (so a meridian flip was done) and the reverse dec on flip is not ticked PHD will drive the mount in dec the wrong way.

[newbie alert]

51 minutes ago, Tomatobro said:

Its been a while since I did this but I recall that if you do a calibration with the mount on one side of the meridian and  calibrate but your target is on the other side of the meridian (so a meridian flip was done) and the reverse dec on flip is not ticked PHD will drive the mount in dec the wrong way.

If you're pulse guiding the mount knows which side of pier the scope is on so no need to tick the box... However you can calibrate both sides of the pier if want, under the tools tab

[michael8554]

Hi Radu

I don't see any information on your equipment, or how it is connected to PHD2 ?

The mount is reporting RA and Dec position, but no mount driver - are you ST-4 guiding with an Aux input to PHD2 ?

From the GuideLog, there are some procedures you are ignoring or skipping.

1. You were pointing at Az = 256.8 deg when you Calibrated. Near south is recommended Az = 180 deg.

Unless you're in the southern hemisphere ?

2. You don't appear to have cleared Dec backlash before Calibrating, by pulsing north until you saw the guidestar actually start to move.

3. Your Cal had a noticeable Orthogonality Error that wasn't reported, because you had "Assume orthogonal axes = yes".

4. Your Guide Rates are very low, RA Guide Speed = 4.5 a-s/s, Dec Guide Speed = 4.5 a-s/s,

At least 7.5 arcsec/sec is recommended

If you're ST-4 guiding, try a larger Calibration Step Size.

5. Your exposure was 5 seconds, which is very slow. What did the Guide Assistant recommend ?

6. You started guiding at 22:27 and Dec immediately started to head north, with PHD2 corrections south having no affect.

You Calibrated at Az = 256.8 deg, but now the mount is at Az = 176.7 deg, so as already mentioned, the "Pier side = West" might be wrong.

RA has about 25arcsecs of Periodic Error that PHD2 struggled to correct, due to the slow guide rate and slow exposure.

You could try the PHD2 PPEC Algorithm from the RA guide algorithm choices.

Have you read the PHD2 Instructions ?

Michael

 

Edited March 6 by michael8554

[Radu Marinescu]

46 minutes ago, michael8554 said:

Hi Radu

I don't see any information on your equipment, or how it is connected to PHD2 ?

The mount is reporting RA and Dec position, but no mount driver - are you ST-4 guiding with an Aux input to PHD2 ?

From the GuideLog, there are some procedures you are ignoring or skipping.

1. You were pointing at Az = 256.8 deg when you Calibrated. Near south is recommended Az = 180 deg.

Unless you're in the southern hemisphere ?

2. You don't appear to have cleared Dec backlash before Calibrating, by pulsing north until you saw the guidestar actually start to move.

3. Your Cal had a noticeable Orthogonality Error that wasn't reported, because you had "Assume orthogonal axes = yes".

4. Your Guide Rates are very low, RA Guide Speed = 4.5 a-s/s, Dec Guide Speed = 4.5 a-s/s,

At least 7.5 arcsec/sec is recommended

If you're ST-4 guiding, try a larger Calibration Step Size.

5. Your exposure was 5 seconds, which is very slow. What did the Guide Assistant recommend ?

6. You started guiding at 22:27 and Dec immediately started to head north, with PHD2 corrections south having no affect.

You Calibrated at Az = 256.8 deg, but now the mount is at Az = 176.7 deg, so as already mentioned, the "Pier side = West" might be wrong.

RA has about 25arcsecs of Periodic Error that PHD2 struggled to correct, due to the slow guide rate and slow exposure.

You could try the PHD2 PPEC Algorithm from the RA guide algorithm choices.

Have you read the PHD2 Instructions ?

Michael

 

Hi and thank you for the reply. Very interesting things you said here, however something seems wrong.

Let's start with specs:
- EQ6R-Pro Mount (I haven't performed mechanical adjustments for backlash yet because the nature or my issue is definitely different, backlash doesn't seem to make your DEC drop to infinity basically)
- ASI120MM-Mini guide camera
- SkyWatcher 250PDS (I know it's a heavy telescope but again, other people still managed to achieve <0.5" total RMS constant guiding even with this setup, the problem is somewhere else)
- The mount is connected directly to my laptop (Asus) using a USB-B to USB-3 cable from the port of my mount, the power supply was recommended by the store and fits the specs of the mount. I am using NINA for slewing and plate-solving, PHD2 for guiding and Green Swamp Server as alternative for EQMOD.

Now, to your points:
"The mount is reporting RA and Dec position, but no mount driver" - seems to be an error because I have a mount driver. I have installed latest Ascom Platform Driver and the mount was instantly detected by both GSS and PHD2 using the new profile wizard. The guiding speed in PHD2 was automatically set to 0.9 after the mount was detected.

"1. You were pointing at Az = 256.8 deg when you Calibrated. Near south is recommended Az = 180 deg. Unless you're in the southern hemisphere ?" - I am in the northern hemisphere and slewed to Betelgeuse (which was very close to the intersection of Meridian with Equator. I have absolutely no idea ehy that az value of 256.8 was logged. Unless somehow PHD2 calibrated after I slewed to Bode's Galaxy (with apparent meridian flip) :-? I am really not sure about this.

"2. You don't appear to have cleared Dec backlash before Calibrating, by pulsing north until you saw the guidestar actually start to move." - This actually I have no idea how to do. The mount's backlash was never adjusted and I am reluctant to do that unless absolute necessary because stores in my country are very picky about warranty. If you are speaking of a software backlash compenstation or something similar, I am new to this and really don't know how.

"3. Your Cal had a noticeable Orthogonality Error that wasn't reported, because you had "Assume orthogonal axes = yes"." - Here again I don't understand again.

"4. Your Guide Rates are very low, RA Guide Speed = 4.5 a-s/s, Dec Guide Speed = 4.5 a-s/s," - Seems to be another error, PHD2 automatically selected guide speed of 0.9 and GSS has both RA Guiding Rate and Dec Guiding Rate to 90%, although I also see here some "Minimum Dec Pulse" and "Minimum Ra Pulse" both set to 20. I don't know what these are. The location settings in GSS are accurate.

"5. Your exposure was 5 seconds, which is very slow. What did the Guide Assistant recommend ?" - Another possible error, PHD2 is set on 2s exposures, I have opened my guiding assistant results after calibration and confirm 2s exposures was selected. The assistant does indicate a large declination backlash and recommended me to set "RA min-move" to 0.13 and "Dec min-move" to 0.20 and recommended that I might need to guide in one dec direction.

So in conclusin there are some things that I don't really understand, why the calibration position from the log is not near meridian where I phisically calibrated (using a slew and center from NINA on Betlegeuse), why the driver doens't seem to be recognised and logged guiding speeds are different than what I set up. I don't really know what to do next.

Edited March 6 by Radu Marinescu

[malc-c]

Just an experiment... Install EQMOD, ensure the ASCOM pulse guiding sliders are both set to x0.90 and both rate boxes are checked.  Then repeat the above using the same stars etc to see if you get the same result.  If you do then it would suggest that the issue is not with the "driver" used to control the mount, be that GSS or EQMod.

[michael8554]

It would appear that info being supplied to PHD2 is missing or erroneous.

So try malc-c's suggestion of just PHD2 and EQMOD.

I can confirm that when continuous guide pulses were being sent, they were over 5 secs apart.

Minimum Move settings will have little impact on Dec Backlash, it's a worm adjustment you need to make.

" I also see here some "Minimum Dec Pulse" and "Minimum Ra Pulse" both set to 20. I don't know what these are."

 "If you are speaking of a software backlash compenstation or something similar, I am new to this and really don't know how."       I suggested PHD2 Dec Backlash Compensation.
 

Most of the answers you don't understand are explained in the PHD2 Instructions - have you read them ?

Michael

[Asher 61 Cygni]

Could you check In GS Server settings :

 

1. If guiding with PHD2 you will want to check mark the option “Reverse Dec output after meridian flip”