PHD2 Guiding issues

[Enigma_RL]

Hey everyone!

So yesterday during the day I finally managed to control my SkyWatcher EQ5 GoTo mount through EQMOD and other software. I'm still waiting for my EQDIR cable to arrive, but for now it worked by simply connecting a USB2.0 A to USB B cable to the EQ5 SynScan control unit and set the Baud rate to 115200 in both EQMOD and the Bitrate on the COM port. Since in the evening it finally stopped raining and we actually got a couple of hours of decently clear skies I was insanely eager to start and try autoguiding for the first time (yes, I am extremely new to this hobby and never took a picture before. I'm kind of learning all the steps and equipment as I go). I set up my telescope, balanced it and polar aligned it.

I'm using a William Optics Uniguide 50mm (200mm focal length) as guidescope and ZWO ASI 290MM mini as guidecam. After some failed attempts I decided to do a clean install on PHD2 and run through the set-up assistant again and making a new Dark Library. I set my mount to Sidereal tracking and after connecting all the gear I hit the loop button to take 2s exposures (played around a little between 1-3s during the night). When looping started I asked PHD to auto select a star and pressed the guiding button. At first it gave me a warning "Calibration this far from the celestial equator will be error prone. For best results calibrate at a declination of -20 to +20". Not being sure exactly what it meant, I did some googling and decided to recalibrate at a point much lower over the horizon (assuming this is what it meant), and didn't get that error again. Before my clean install this is what my guiding looked like:

You can see in the graph that I reset it once, but no matter how many times I tried on different stars or even multiple stars, the graph kept steadily declining and the total error rate kept steadily increasing. After the clean install and calibrating this is what my graph and calibration details looked like (I know the calibration isn't looking good as they are supposed to be straight lines if I'm not mistaken).

Does anyone know why this is the case? My Dec graph seemed to want to stay within view at least, while my RA dropped straight to the bottom again, total error was still steadily increasing. On top of this I had 2 more warnings from PHD: "Advisory: Calibration completed but RA and Dec rates vary by an unexpected amount (often caused by large Dec backlash)" and "PHD2 is not able to make sufficient corrections in RA. Check for cable snags, try re-doing your calibration, and check for problems with the mount mechanics". Being so new to this hobby it's hard for me to make sense out of most of these messages so I'm hoping someone is able to help me troubleshoot. Could it be a result of bad polar alignment, bad focus or a bad cable? Am I doing something wrong with my calibration? Can it be that my guidecam was rotated giving wrong angles? Is there a specific point in the sky best for calibration? Am I using wrong values somewhere?

Please let me know if you have any tips or advice. Thanks!

Edited November 1, 2021 by Enigma_RL

[scotty38]

You definitely need to make sure the mechanics are correct in the first instance. Make sure you're polar aligned and that the scope/mount is reasonably well balanced in RA and DEC. It can be advisable to be slightly east heavy but that takes some getting your head round (well it does for me) so I'd just go for being as balanced as you can and that there are no physical cables snags or tight cables.

 

[Enigma_RL]

1 minute ago, scotty38 said:

You definitely need to make sure the mechanics are correct in the first instance.

And how would I go about making sure? From what I can tell the motors are functioning well if that's what you mean? I think my polar alignment was spot on and my balance was also pretty good (maybe a very tiny bit back heavy). The cables seemed fine and after rebooting the mount and reconnecting all cables I had no improvement.

[Skipper Billy]

You need to calibrate PHD2  on a star that is near the celestial equator and the Meridian - which for us is due south.

It sounds like you might have a lot of backlash in your mount which will need to be adjusted out. You can minimise this by running the mount 'east heavy' but its best to adjust it.

There is a useful document on my website that will help you.

PHD2 https://drive.google.com/file/d/1zY8jNZkrNezQxG2h3LP6_Xp6a5YKYtFF/view

There are loads of YouTube videos on how to adjust out the backlash.

Good Luck!

 

 

[scotty38]

5 minutes ago, Enigma_RL said:

And how would I go about making sure? From what I can tell the motors are functioning well if that's what you mean? I think my polar alignment was spot on and my balance was also pretty good (maybe a very tiny bit back heavy). The cables seemed fine and after rebooting the mount and reconnecting all cables I had no improvement.

Pretty much as you have done to be fair so if that's all good it's on to the next things as mentioned above.

Edited November 1, 2021 by scotty38

[Enigma_RL]

5 minutes ago, Skipper Billy said:

You need to calibrate PHD2  on a star that is near the celestial equator and the Meridian - which for us is due south.

It sounds like you might have a lot of backlash in your mount which will need to be adjusted out. You can minimise this by running the mount 'east heavy' but its best to adjust it.

There is a useful document on my website that will help you.

PHD2 https://drive.google.com/file/d/1zY8jNZkrNezQxG2h3LP6_Xp6a5YKYtFF/view

There are loads of YouTube videos on how to adjust out the backlash.

Good Luck!

 

 

Thanks! Will definitely look into this

[michael8554]

From your first image:  Declination = 90.0 degrees.

Guiding pointing at the north pole in Dec ain't going to work very well.

From your second image:  RA Guide Speed = 0.10x,  Dec Guide Speed = 0.10x

These are far too low, they need to be between 0.50x and 0.90x.

You probably have the EQMOD ASCOM PulseGuide Settings too low.

I suggest you spend some rainy evenings reading how to use PHD2 and EQMOD.

Guides are available via the PHD2 Help menu, here's some to start with:

https://github.com/OpenPHDGuiding/phd2/wiki/EQASCOM-Settings

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

Michael