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polar alignment moved????

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Last week or so, being at the observatory I was able to achieve a good polar alignment.
See first picture, then tonight I decided to check again from remote.... I don't understand how this can move??



4 years 11 months ago #38146
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What do you mean with move? In the first image the polar alignment error is 12", in the second 1'43" and yes that is a difference. Not sure what could have caused that. If you refer to the different star field in the images then the telescope simply is pointed at a different part of the sky.


Wouter
Last edit: 4 years 11 months ago by Wouter van Reeven.
4 years 11 months ago #38205

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yes, the image field is pointing to a different part, but it's not that far away from the first picture. Surely the polar error should be the same, no?
4 years 11 months ago #38207

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Well, if you are 100% and more sure that nothing has touched and moved the mount then I'd say yes, the polar alignment error should stay the same. When you got the 12" polar alignment error, did you park the mount, close the box, opened it again and redo the polar alignment to check and verify that it kept the same alignment error? 12" is much better than 1'43" in terms of polar alignment error but 1'43" is not that different from 12" in terms of physical displacement. I am not trying to imply that you haven't been careful to make sure that all is tightened and stable but there are loads of things that screw up polar alignment. It is hard to tell what could explain the polar alignment error change without having been there physically.
4 years 11 months ago #38209

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That's something I did not do.


Could be an imbalance in the imaging gear, too heavy on one side etc.. maybe?
I will be double check it when I'm over there next time.
4 years 11 months ago #38213

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Replied by nMAC on topic polar alignment moved????

I would check that next time, that could be exactly the source of all your problems.
4 years 11 months ago #38216

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Yes, that is exactly what I mean. See also nmac's comment.

EDIT Recently I was made aware of this presentation about the importance of balancing your astro gear .
Last edit: 4 years 11 months ago by Wouter van Reeven.
4 years 11 months ago #38217

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Replied by Greg on topic polar alignment moved????

We noticed that the PA was not consistent unless you always start from park and always move in the same direction during the process. Also, one problem was a pin that the az bolts pinch. It was not solid. The HEQ5 mount does not have a pin but a boss instead that is part of the structure so it can't move. But I'd say you have something not screwed down solidly - like the house! Haha - sorry just kidding.
4 years 11 months ago #38233

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Interesting presentation, I always tried to balance the RA first, I shall try this method next time.
4 years 11 months ago #38235

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Replied by Andrew on topic polar alignment moved????

If you were to use phd2 for an evening, you can use the logs to measure your polar error based off the corrected drift. It could serve as an independent test.
4 years 11 months ago #38249

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I have been asking for this for a long time.. I never really measured PAA against any other method.
4 years 11 months ago #38250

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Replied by Andrew on topic polar alignment moved????

Jasem. Based off of what I have seen, the polar error reported by PHD2 agrees almost exactly with the remaining error I have after the PAA routine. At least within ± 10 seconds
The following user(s) said Thank You: Jasem Mutlaq
4 years 11 months ago #38258

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