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Question Best results when calibrating on the target rather than near the equator?

  • danielh21
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15 Jul 2020 04:13 - 15 Jul 2020 19:21 #344 by danielh21
I seem to be getting much better performance with my M-Zero in PHD2 when I calibrate on my target for the night, rather than calibrating near the celestial equator as is often recommended for PHD guiding. In fact, tonight I could not center the star at all after dithering without calibrating on a star in the target FOV. My prior calibration was close to the equator. Now, not only can I dither very quickly, but the actual RMS in PHD2 is substantially better. Is this normal for Avalon mounts? I mean, it is not an inconvenience at all really, but I just wonder if something might be wrong on my end or if this is normal for Avalon mounts.

Edit: It looks like my sequence ended at 3:38 this morning when PHD came up with an error message saying "Recalibrate near the equator." Interesting. Never seen this before. All the subs looked perfect despite this error, so I'm not sure what the problem was.
Last edit: 15 Jul 2020 19:21 by danielh21.

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16 Jul 2020 01:52 #345 by danielh21
So tonight I recalibrated again, this time near the equator, and now I'm getting very good results. Still perplexed as to why I was having so much trouble last night, and only last night. I do not think it was cable snag as that wouldn't explain why my guiding was fine when calibrating on the target.

For further info, the target I'm imaging tonight and last night is in Cepheus. I calibrated at about DEC +7.

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  • Stefano82
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22 Jul 2020 13:44 #347 by Stefano82
Hi Daniel

Normally the best practice for a good calibration, performed within about +/- 20 degrees of the celestial equator and high enough in the sky to avoid major seeing (turbulence) problems, as suggested on the PHD2 website, it can be considered a good hint also for Avalon Instruments mounts.

On the other hand, performing a calibration directly on the guide star target, it is a good practice.

Just be aware that, the more close to the Celestial Pole it will be the target, the higher will be the calibration step time duration, due to the less movement of the star.

Furthermore, as the calibration step it is the same for both axis, the bigger target distance from the celestial equator, the bigger will be the calibration step amount required.

That’s why, in order to have a more balanced axis calibration quality, it is better to perform the
calibration as close to the Celestial Equator as possible.

However, as also stated on the PHD2 website, in the Calibration explanation section “Even with high-end mounts, calibrations can occasionally go awry because of environmental conditions, especially wind and bad seeing”.

Let us know if you still find in the future strange calibration behaviour.

Kind regards

Stefano
Avalon Instruments Team

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