Can't Figure Out Why I a Having Problems

[Lee]

I'm beside myself. I've been trying to figure out what is causing my guiding to give me saw tooth RA corrections throughout my imaging session (see attached log between 20:42 and 20:43). This results in egg shaped stars.  I've adjusted gain, put vibration suppression pads under the legs, changed image length. I'm using a Wave100i, imaging with a Askar 71F at 490mm and guiding with ASI224MC at 120mm. Attached is a short guiding session from tonight to capture the issue. I don't know what else to try. 

https://openphdguiding.org/logs/dl/PHD2_logs_wTWa.zip

[Brian Valente]

Hi Lee

I recommend you do a baseline guiding to make sure you (and we) understand the basic performance of your mount. The guide to do this is attached

first you are calibrating very far from dec 0, so that is almost certainly causing issues

please download the latest DEV release and use the calibration wizard

https://openphdguiding.org/development-snapshots/

your calibration also had a number of lost star events, so make sure you get a clean calibration before proceeding. 

strainwave mounts generally are guided differently than GEMs, here are a few suggestions to start:

- fast exposure/guiding cadence of 0.5-1 second

- do not use PPEC for RA, instead use Hysteresis (at least for now)

- you may need to experiment with the aggressiveness of the RA algorithm. 

I would avoid using 'vibration suppression pads', and make sure you are on solid concrete or other firm surface (i.e., not grass or soil). make sure you are not walking around near the mount. 

that's a good start

On Mon, Sep 8, 2025 at 6:06 PM Lee <lee.po...@gmail.com> wrote:

I'm beside myself. I've been trying to figure out what is causing my guiding to give me saw tooth RA corrections throughout my imaging session (see attached log between 20:42 and 20:43). This results in egg shaped stars.  I've adjusted gain, put vibration suppression pads under the legs, changed image length. I'm using a Wave100i, imaging with a Askar 71F at 490mm and guiding with ASI224MC at 120mm. Attached is a short guiding session from tonight to capture the issue. I don't know what else to try. 

https://openphdguiding.org/logs/dl/PHD2_logs_wTWa.zip

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Brian Valente

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[Lee]

Thank you for the suggestions. I'll see what I can do tonight.

[Lee]

Just wanted to say thanks. I ran the latest dev build and followed the documentation for creating a baseline. I ran the guiding assistant, multiple times, but always received the same results. I let it run for 15 min when it ran. It kept telling me to try and focus better, but I had already done that with a bhatinov mask before I started. It made recommendations for min moves, which I applied. It said the backlash was high in RA and I might consider only doing it in dec, but the apply button was not available to select. I switched to hysterisis for RA guiding as recommended. I ran an imaging session, and didn't see the guiding errors I had before. I think the biggest change was not doing a calibration near Polaris, where my target was. I slewed to as far south as I can get from my location, which is about 43 degrees. Next time I get a clear southern horizon, I'll do another calibration. I may also invest in a better guide camera. I think switching to a 220mm would be an improvement over the 224MC in guiding accuracy.

[Brian Valente]

Thanks for the update Lee

>>> I think the biggest change was not doing a calibration near Polaris, where my target was.

yes, i agree. the errors around the pole can be greatly distorted, it's best to avoid calibrating anywhere near there 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/83d83bc1-870e-4b7f-aa42-ae4d30327b3an%40googlegroups.com.