Problem Tracking with Celstron Nexstar Evolution 925

[Enderw2030]

Hello , 

i am traying since now one week to make PHD2 guide my mount. For that I use CPWI, which is then linked to PHD and as Guide Camera an ASI 120MMC-s. 

The problem that i have look like this : 

1. after about 2 minutes i have a frame where the stars are swinging wild . The PHD losses the star and then is stuck. 

2. From time to time it is functioning really well until in the moment i pause it and slew to a star for re-focus, then when i come back to Target and starts again with losing the stars because of this wild swinging every 2-3 minutes. 

3. I also have some weird situations when during the calibration there is a stuttering move of the telescope and then losses the star again...

4. Seems like my PHD2 doesn't  log everything...the last file that i have attached is from 28.02 when all functioned good...until reslew. 

I have already tried :

1. With and without binnig.

2. With and without Backlash Compensation in CWPI.

3. Directly through CPWI or trough ASCOM Hub and then CPWI.

4. I have tried directly with ASCOM Telescop Driver, so no CWPI

5. I have changed the guidng scope from 400mm to 240mm ( with the different profiles ofcourse).

6. I have tried to calibrate in different positions.

7. With Nina or without Nina attached. 

8.Different gain and exposure times

...all with the same result. 

What i have observed is that from time to time i can get a guide for 5 minutes, when no calibration is in the telescope ( no model or no sync from Plate Solver) . When i plate solve it or introduce a saved model...usually it goes haywire again.but it is not something that i can reproduce.

Any help is really appreciated.

Thank you . 

Link to the newest log: 

https://openphdguiding.org/logs/dl/PHD2_logs_wgwB.zip

[Enderw2030]

I forgot to mention that i am using a Wedge, so is basically an EQ mount without a need for a meridian flip. :). 

[Enderw2030]

https://openphdguiding.org/logs/dl/PHD2_logs_jgny.zip

here is a link when all funktioned well until reslew...the first one ist just the problems that i had the next day..

[Bruce Waddington]

I don’t think we can say much about what’s going on here, there are way too many variables.  I suggest you go back to using your 400mm refractor where you have a reasonable guider image scale.  Decide on what mount connection you want to use – presumably CPWI – and stay with it. Then carefully run a series of tests according to this plan:

 

https://www.dropbox.com/s/os1thorvswmzaul/How%20to%20create%20a%20baseline%20for%20guiding%20results%20using%20OpenPHD2.pdf?dl=0  

 

Don’t run NINA, don’t try to do any imaging, just work with PHD2 to figure out what’s going wrong with your setup.  One thing you should definitely check is the tightness and rigidity of the guiding assembly – all the mechanical attachments between the guide camera and the main telescope.  Also be sure you don’t have hanging or dragging cables.  From what little I could see from your logs, it looks like you’re getting unwanted movement in this area, events not attributable to either guiding or basic mount tracking.

 

Good luck,

Bruce

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[Enderw2030]

Thank you Bruce. 

I will check agaian or maybe use a smaller main Scope ( the NexstarEvolution with the C9 is at it limits) .

Another fact that i would like to try is to shut of the Dec Tracking from the Mount. As Evolution is an ALT AZ Mount at the core, the tracking is enabled in both axis. Is it something that may influence PHD2?

Thank you , 

Bogdan.

[Bruce Waddington]

You can’t keep changing variables if you want to get to a stable configuration.  If the scope is on a wedge, it should be capable of guiding in both RA and Dec.  Follow the procedures I sent you and we should be able to determine what the mount is capable of doing and where it’s shortcomings are.  For example, the Guiding Assistant will show what the mount is doing with no guiding being done at all, including Dec.  You can’t try to just jump to a solution, you have to understand the problem first.

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/555010cc-5cb0-4983-942f-a9b90e03e6d9n%40googlegroups.com.

[Enderw2030]

Hello Bruce, 

yesterday I did all the steps that were written in the PDF. As you can see from the log :

https://openphdguiding.org/logs/dl/PHD2_logs_mqnB.zip

1. the assistent told me that my polar allignement was wayyy off.

2. I re-did it with PHD2 Drift Allignement

3. I run the calibration , no issues.

4. I run the assisten and applied the sugested changes ( outside the one with backlash) 

5. Then i guided for 37 minutes : no issues ( log entry 46) in the same position

6. Then i slew to a target on the west side of the meridian , was ok: see entry 47

7. Then i slew on the east side of the meridian( from entry 48) and it strated all over again. I inspected to see for loss cables, scope , ..nothing. 

8. Then i tryed to reclaibrate on the east side of the meridan , but even in the calibration i could hear a  loud clang in the DEC clutch as PHD2 was moving North or SOuth ( not west or east). 

9. I tried some more with no result. 

10. Then i've got into CPWI and  selected : DEC Only Tracking. And all of the sudden it worked ( entry 59).

11. Moved arround to different Target est and west of the Meridian and it was ok.

12. I ran the assisten again : 

and i accepted the changes. 

13. I still have to guide for a few minutes once i slew to a new traget because is not so smooth at the beginning, but with these setting i could take a 300s Photo without elongated start ( at least to my eyes) .

14. The assistent said second time that the backlash was too big and has aborted the operation..

 

Should I enable the DEC Tracking again and try to only guide in north direction in dec as sugetsed? 

Thank you , 

Bogdan. 

[Enderw2030]

For the point 10 on the List , i wanted to say only RA tracking, Dec was disable from the internal Mount menu. Sorry for the error. 

10. Then i've got into CPWI and  selected : DEC Only Tracking. And all of the sudden it worked ( entry 59).