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Trouble with PHD2 Autoguiding | Beginner

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#1 astroricco

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Posted 15 July 2020 - 03:29 AM

Hello Astro Community,

 

i am new to this forum and i have made this account because i hope to get an answert or a solution-hint to my "strange" autoguiding problem with phd2 / telescope setup. At first i want to mention that i am a beginner regarding to autoguiding but i have read and watched many tutorials online about it so i would claim that i am familiar with the basics.

 

Before i start to explain the Problem i want to inform you about my setup:

  • Mount: Skywatcher AZEQ6
  • Telescope: Skywatcher ESPRIT 80 ED
  • GuideScope: GuideScope50 180mm
  • GuidingCam: ZWO ASI 120 Mini
  • Laptop for PHD: DELL Latitude 7490 Windows 10
  • PHD Version:  2.6.9
  • The guide-cam is connected from the ST4-Port to the guide port of my azeq6 (currently i use "on-camera" and not the ascom eqmod cable)

My approach for Autoguiding:

  1. Balance the Esprit 80 ED with the counterweights on the AZEQ6 mount (For now i always tried to balance it as best as i can but because of the GuideScope50 there is an asymmetry, so the telescope is slightly unbalanced at any time)
  2. Polar-Align the mount (as precise as possible - I was told that an polar error of under 5' seconds should be okay for autoguiding but i try to bring it always to nearly zero)
  3. 3-Star Alignment with the GoTo-SynScanHand-Control 
  4. If Polar-Alignment-Error is to big, i use the Polar-Alignment Function of the SynScanHand-Control to reduced it to the minimum (Look at the Picture from my hand Control - polaralignment-error.jpeg)
  5. Slew Telescope to a bright star (last time i used the star vega)
  6. Go Through the profile wizard, for the camera i get the pixel size automatically cause the camera is also connected with a cable to the computer. As my Cam i choose ASI ZWO and as mount setting: "on-camera" - 180mm focal lenght of the guide scope - off-axis: no - and i also create a dark-frame library, so auto star selection should work without hot-pixels!
  7. I start looping 3seconds exposures and try to focus my guide scope cam with the star-profile window -> last time i remebered a value of somwhere in between 3 and 5 HFD. (Is this to big ? - It wasn't possible for me to make the HFD smaller) - I have read that it is better to focus the guide cam in sharpCap but i always tried it in phd with the HFD value.
  8. Than i let phd auto select a star and start the calibration.
  9. Up to this point of time i dont get any warning or error message from PHD!
  10. The Guiding starts and works for some few seconds but than i see how the DEC Axis in the phd2 graph climbs up. After that i get the error Message: "PHD2 is not able to make sufficient corrections in DEC Check fo cable snags try re doing your calibration and make sure the st4 cable is working properly (Look at the picture i have added to this post - phd2-graph-1.png & phd2-graph-2.jpeg). When i start the guiding again (no matter wich star and also with new calibration) the same thing happens over and over again. Sometimes fater 2 seconds sometimes after 6 seconds..

What i also want to say is that i have tried to redo the whole setup from scratch once again again on an completly other night, but i run into the exact same behavior as descibed above!

 

I have added the PHD2 Log files of the night 12.07.2020 (german date format), i really don't know what i am doing wrong, does someone of you guys has an idea what i am doing wrong?

I would be extremly grateful for tips or hints what i can try on my next observing night session!

 

Clear Skies,

Astro-Ricco

 

 

Attached Thumbnails

  • phd2-graph-1.png
  • phd2-graph-2.jpeg
  • polaralignment-error.jpeg


#2 astroricco

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Posted 15 July 2020 - 03:44 AM

I forgot to attach the phd-logs mentioned above here are the links to my two log files (txt files) shared with google drive:

 

https://drive.google...iew?usp=sharing

 

https://drive.google...iew?usp=sharing



#3 astroricco

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Posted 15 July 2020 - 03:49 AM

Another text-mistake i made in the post:

 

"I was told that an polar error of under 5' seconds should be okay for autoguiding but i try to bring it always to nearly zero"

Of course i meant 5 minutes not seconds!



#4 happylimpet

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Posted 15 July 2020 - 03:54 AM

Gosh, you dont need to be anywhere near that close for Polar Aligment (even now youve changed it to 5 mins - well, thats probably a sensible target!). I've been a degree off and still got sharp images, just a bit of field rotation. People talk a lot of rot about this. Its BEST to be close of course for several reasons, but the point of autoguiding is that it compensates for errors.

 

Sorry, cant help with you main problem! Can you try moving the scope using the st4 outside of PHD2 to check its working?


Edited by happylimpet, 15 July 2020 - 03:54 AM.

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#5 astroricco

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Posted 15 July 2020 - 04:18 AM

Gosh, you dont need to be anywhere near that close for Polar Aligment (even now youve changed it to 5 mins - well, thats probably a sensible target!). I've been a degree off and still got sharp images, just a bit of field rotation. People talk a lot of rot about this. Its BEST to be close of course for several reasons, but the point of autoguiding is that it compensates for errors.

 

Sorry, cant help with you main problem! Can you try moving the scope using the st4 outside of PHD2 to check its working?

Thank you for your information about the polar alignment error, thats good to know that the polar alignment doesn't has to be extremly exact. PHD2 did a successful calibration (without error or warning alerts - isn't that proof enough to say the mount is successfully moving via st4? Also the guiding is working for quite some seconds so commands must be send and recived successfully at least for this 3-6 seconds before the guiding fails.



#6 SonnyE

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Posted 15 July 2020 - 04:21 AM

You could try a walk-through with these:

PHD Basics 1

PHD Basics 2

 

Both pretty short, but very helpful.

After that, a bit of trial and error with your settings and you should see some better guiding.


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#7 Phil Sherman

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Posted 15 July 2020 - 10:50 AM

Have you tried getting rid of the ST4 cable and using pulse guide? If you're using PHD2 then you have a computer at the mount and it's not a big deal to run the mount from the computer. The ASCOM platform, EQASCOM (aka  EQMOD) and CdC (aka Sky Chart), all free downloads will get you started. Pointing can be greatly improved by adding a plate solver that will create sync points for EQMOD. You can use the hand controller's update cable and the hand controller set to "PC Direct" mode to run the mount. If you like this arrangement, you can replace the hand controller with one of Shoestring's adapters or use one of the other different options to connect the computer to the mount.



#8 astroricco

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Posted 15 July 2020 - 12:39 PM

Thank you for your good advices! Defenetly worth to try! This week I have bought me a eqmode direct cable from pegasusastro but haven‘t tried it yet. Because for me its hard to believe that just a cable change with a another communication protocol could solve my guiding issue. Yes i have also thought about a plate solver and this is defenetly somethibg i would like to try, dont really think that a better alignment will fix this issue cause the shown
polar alignment error is anyway small, i always optimize the azimut and altitude with the drift align of phd and the polar alignment function of the synscan handcontrol

#9 StephenW

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Posted 16 July 2020 - 09:36 AM

>I forgot to attach the phd-logs mentioned above here are the links to my two log files (txt files) shared with google drive:

 

fyi: Your logs are private and cannot be downloaded


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#10 billdan

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Posted 16 July 2020 - 02:58 PM

Something is causing your DEC to take off, it could be not balanced in DEC, or the DEC clutch not tight enough, or polar alignment.

Try using PHD2 guiding assistant which disables guiding and watch the graph, especially DEC, if you have a good polar alignment it should be close to a flat line.

 

Best to do this test when DEC = 0° along the N-S meridian, you get the best accuracy.

 

This guide assistant graph is from my old EQ6 and covers a 25 minute time frame, whilst RA looks terrible,  DEC is reasonably flat until near the end.

Attached Thumbnails

  • guide-assist EQ6-crop.JPG

Edited by billdan, 16 July 2020 - 09:50 PM.

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#11 astroricco

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Posted 17 July 2020 - 05:50 AM

>I forgot to attach the phd-logs mentioned above here are the links to my two log files (txt files) shared with google drive:

 

fyi: Your logs are private and cannot be downloaded

dumb of me, i have changed the authorizations, now its public!



#12 StephenW

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Posted 17 July 2020 - 12:08 PM

The calibration runs in the first of your two logs are all over the place, but they improve greatly in the later log - what did you change?

 

Even so, the calibration runs in your later log still have significant issues in DEC - the mount is moving too far when moving South.

 

In most of your (very short) guide tests, it doesn't look like the mount is responding to DEC corrections at all.   The only exception I can see is the 42s segment where it does appear to be responding to DEC.

 

If I had to guess I'd say you have a bad ST4 cable and the DEC corrections are just not making it through and/or are flaky.   If you already have the EQMOD cable I'd strongly suggest trying that - it will also allow PHD2 (and us) to know where the mount is pointing during the tests.

 

So I'd suggest setting up the EQMOD direct cable via ASCOM, re-doing calibration and then doing some guiding tests (at 5-10 minutes each, not 30s) and uploading the new logs.


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#13 astroricco

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Posted 17 July 2020 - 05:21 PM

The calibration runs in the first of your two logs are all over the place, but they improve greatly in the later log - what did you change?

Even so, the calibration runs in your later log still have significant issues in DEC - the mount is moving too far when moving South.

In most of your (very short) guide tests, it doesn't look like the mount is responding to DEC corrections at all. The only exception I can see is the 42s segment where it does appear to be responding to DEC.

If I had to guess I'd say you have a bad ST4 cable and the DEC corrections are just not making it through and/or are flaky. If you already have the EQMOD cable I'd strongly suggest trying that - it will also allow PHD2 (and us) to know where the mount is pointing during the tests.

So I'd suggest setting up the EQMOD direct cable via ASCOM, re-doing calibration and then doing some guiding tests (at 5-10 minutes each, not 30s) and uploading the new logs.



#14 astroricco

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Posted 17 July 2020 - 05:26 PM

Thank you stephenW for your detailed answer! As soon as the weather will be better here in austria (vienna) i will try to guide with my eqmod cable and will create better log files if the issue stays present! Regarding to your question, in the beginning i think i was doing a polar drift alignment with phd.

#15 astroricco

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Posted 17 July 2020 - 05:28 PM

Something is causing your DEC to take off, it could be not balanced in DEC, or the DEC clutch not tight enough, or polar alignment.
Try using PHD2 guiding assistant which disables guiding and watch the graph, especially DEC, if you have a good polar alignment it should be close to a flat line.

Best to do this test when DEC = 0° along the N-S meridian, you get the best accuracy.

This guide assistant graph is from my old EQ6 and covers a 25 minute time frame, whilst RA looks terrible, DEC is reasonably flat until near the end.



#16 astroricco

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Posted 17 July 2020 - 05:29 PM

Hi billdan, thank you for your answer, youre right! On my next session i will defenetly try to run the guiding assistant.

#17 astroricco

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Posted 27 July 2020 - 02:53 AM

SOLVED - Yesterday i was able to do correct autoguiding, because of the astro pegasus eqdirect cable (ASCOM). It was a problem with some phd settings and because ascom does know informations about my mount, it read out the correct settings automatically.
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