Re: [open-phd-guiding] New to guiding and Unable to guide accurately ... please help

[Brian Valente]

Hi Pratul

Can you send a couple pictures of your setup from different angles, make sure to include details on the guide camera/scope setup.

Your main issue is lack of a good calibration. You haven't gotten an acceptable calibration (they are pretty bad, actually), so all guiding is going to be poor until you resolve this. 

For now i would focus on calibration and not look at the guidelogs as any indication other than the calibration is bad. Once you get a good calibration, chances are your guiding will improve in many ways.

Make sure you use the calibration assistant, and follow it with the guiding assistant run. Resolve any issues that the assistants bring up (such as the orthogonality error you already received).

You can also use our baseline guidelog steps (see attached PDF) as a step-by-step to use PHD as a diagnostic tool.

Brian

On Fri, Mar 20, 2026 at 8:10 AM prsharma <pratu...@gmail.com> wrote:

Hello: I am a new to astrophotography and guiding and trying to setup my go to mount with PHD2 but can't get it to work for more than a few minutes. I have watched a lot of youtube videos including all the ones suggested on the PHD2 website and tried to follow all the recommendations. I think my issue is with my mount and have opened a ticket with Sky Watcher as well. They asked me to log an unguided session and submit the PHD2 guide log. I have linked the log file below. I am hoping someone here can take a look at the log file and confirm if it is indeed a mount issue or of I have PHD2 configured incorrectly. 

I have also included a link to log files for my last guided session (Guiding Begins at 2026-03-13 21:38:09) that shows the issue I am having. Please ignore entries after this one. There was another person there that tried, unsuccessfully to make config changes to stabilize guiding. 

Thank you for your help in advance. 

Pratul

My setup:

Mount: Sky Watcher AS-EL55i Pro

Guide camera: ASI676MC

Guide Scope: William Optics Uni-Guide Scope Ultra (200mm)

My process:

1. Rough polar align using "PS Align Pro" app on an iPhone
2. Run PHD2 Calibration Assistant
3. Run PHD2 Drift Alignment
4. Run PHD2 Guiding Assistant and apply recommend changes
5. Start guiding

Link to log files:

Guide log file: https://openphdguiding.org/logs/dl/PHD2_logs_iGvN.zip

Un-guided log file:  https://openphdguiding.org/logs/dl/PHD2_logs_3A6P.zip

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Brian 

Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[prsharma]

Hello Bruce: Thanks for your reply. 

• I will take a few pictures of the setup tonight and upload them. 
• The first calibration is after doing a rough polar alignment using    "PS Align Pro" app on an iPhone. This one is always bad. (I can't see Polaris from my location and haven't found a better way to do polar alignment.  (I do this first as PHD2 will not let me do a drift alignment without a valid calibration. )
• I then do a drift alignment using PHD2. The one recorded in the submitted logs showed a polar alignment error of 3.1'. Is that not good enough? 
• I follow this with another calibration assistant run. The one in the submitted logs looks like the image below. It shows an orthogonality error of 0.3. 
• I follow this with Guiding assistant and apply recommended changes. 

When using the Calibration assistant, drift alignment and guiding assistant I let PHD2 slew to the location on it's own. 

I believe I am following the steps recommended in the baseline document (Except for the first calibration to be able to do drift alignment).

Please do let me know if I should be doing anything differently. 

Thanks for your help and patience dealing with a clueless newbie 

Thanks!

[Brian Valente]

Pratul

Brian here (not Bruce, but that's okay :) )

Thanks for pointing that out. your guidelogs and calibrations are kind of all over. 

Your guided output showed no good calibrations so the entire guiding in this log is not useful for analysis.

The unguided output showed one bad calibration, followed by a lot of short runs (again, no good for analysis) and then one less-worse calibration at the end

That one calibration you referenced had numerous lost star events (which makes the calibraiton questionable), alerted you to a calibration error (rates), and was not followed by a guiding assistant run. So I think we are still looking for  a valid end-to-end baseline guidelog, that should be your next step in addition to the pictures.

If you had run the guiding assistant after that good calibration, it would have told you 

1. there is substantial dec backlash in your system. fiddling with dec's min move like you did won't help, but enabling dec auto backlash compensation will. The amount of backlash would have been indicated by the GA run, but you can start with 800ms and see how that goes

2. your periodic error for the mount is quite high around +/-24" or about 48" peak to peak. SW should have a spec for their mount but I would guess it's <10"

 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/7c47ba3f-0f1a-49b9-b48a-d8b2ebd3e77en%40googlegroups.com.

[prsharma]

Brian: My sincere apologies! I hate it when people do that to me and even more when I do it myself. Sorry!

The periodic error is what I was concerned about. Thanks for confirming. 

I am going to do another test tonight. Hopefully it will be a lot cleaner. The short runs are mostly from the drift alignment. Still trying to get a hang of it 🥴

I will do the following:

1. Rough polar align using "PS Align Pro" app on an iPhone
2. Run PHD2 Calibration Assistant 
3. Run PHD2 Drift Alignment
4. Run PHD2 Guiding Assistant and apply recommend changes
5. Run PHD2 Calibration Assistant

1. Run unguided for 20 - 30 minutes (To capture mount behaviour)
2. Run guided for 20 - 30 minutes

Thanks for your help and apologies again for messing the name. 

Pratul

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/CAJa45i5wAVP54W7kHzQajt%3DN10ZyzDcWnd0SwcYdDPVeDXuOaQ%40mail.gmail.com.

[Brian Valente]

perfect

I can't really comment on polar alignment but based on your description, it sounds like you are taking the right approach there. 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/CAMMLnGMyDRF-p-M2V6k%3DgfmF44iQOFo0_02jPVdR5BM17FUnng%40mail.gmail.com.