Disturbance in DEC

Steve Elliott

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Sep 24, 2021, 7:24:11 AM9/24/21

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Can anyone explain the disturbance in DEC in the last session of guiding in the attached logs. The disturbance occurs at 21:23:01. Everything is looking pretty good then it goes to hell for about 20 seconds. I was watching it. Nothing knocked the mount, no gust of wind.

cheers

Steve

https://openphdguiding.org/logs/dl/PHD2_logs_uTw7.zip

bw_msgboard

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Sep 25, 2021, 10:59:08 PM9/25/21

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Hi Steve. This happened because you enabled Dec backlash compensation at 22:11 and the initial compensation pulse caused an over-shoot. It took about 40 seconds for the algorithm to adjust the size of the compensation and regain stability. When you are enabling and disabling this feature in the middle of imaging, you have to expect there may be a period of stabilization that's needed and you may have to discard an image. It would be better to make your changes while you're not imaging. Based on the very different results you got from the backlash measurements, I would say your mount responds very inconsistently to Dec direction reversals so it will be difficult for the PHD2 Dec backlash compensation to avoid these instabilities. Have you investigated how you might improve the mount mechanics?

Regards,

Bruce

From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Steve Elliott
Sent: Friday, September 24, 2021 4:24 AM
To: Open PHD Guiding
Subject: [open-phd-guiding] Disturbance in DEC

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Steve Elliott

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Sep 26, 2021, 1:50:20 AM9/26/21

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Thanks Bruce,

I know I have a problem with DEC which I'm working on. I'm waiting for some new parts. I couldn't understand why it should suddenly go haywire after running well for some time. I should have realised.