Polar Alignment Discrepancy Between PHD2 and Sharpcap?

[mshe...@gmail.com]

Just curious. I'm getting a significant difference between PHD2 GA polar alignment error and Sharpcap polar alignment error. PHD2 shows an error of 40 arc-min while Sharpcap is under 10.

    Can folks provide me any guidance about the discordant results and how to resolve the discrepancy? Thank you and best regards.

Mike

[Bruce Waddington]

The measurements are being made differently.  PHD2 estimates polar alignment error based on the rate of drift in Declination.  That's an objective measurement but the cause of the drift could be something other than simple polar alignment error.  So if you have recent to doubt that it's due to polar alignment, you will need to find another cause: flexure in the mount payload, substantial imbalance of the OTA in Dec, hanging cables, a loose clutch, etc.  If you look at the unguided Dec behavior for extended times on each side of the meridian, that may point you in the right direction.  Since you didn't upload any data, that's about all I can tell you.

Regards,

Bruce

[mshe...@gmail.com]

Thanks! I should be running PA again later next week and should have more data. Best regards.

Mike

[Tommy M]

I usually have a similar discrepancy.  However, when SharpCap shows an improvement, so does PHD2 GA.  I had a PA error of 6, I polar aligned again with SharpCap and it went down to 2.2 (and the improvement showed in my guiding graph).  That's all I care about.  Unlike Bruce, I have no idea how the magic works, only that it does!

Tommy

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