Re: Tracking Accuracy

Khalid Baheyeldin

On Sat, Sep 22, 2018 at 11:24 PM, Khalid Baheyeldin wrote:
I took an exposure that is 960 seconds (two rotations), of Albireo (with a known distance between A and B of 34 arc seconds). The result is attached.

There is no PEC yet on this mount (neither with a sensor, nor with parking only).

Look at the two orange stars on the left below center.

There is a large wave which is due to periodic error.

The question is: what are the smaller fluctuations?
An update on the above.

On Oct 4th, I took two images of Albireo (2018-10-04-a, and 2018-10-04-b), unguided.
Each is 480 seconds, which is one full worm rotation.
Same night, same OnStep alignment model, same balancing.
The difference between them is that -b has better polar alignment.
Nothing else changed.

The high frequency zigzag pattern (in the two orange stars) are visible.

Last night (Oct 18th), I did the same test, 480 seconds, and Albireo.

The low frequency (worm period) is more pronounced (higher amplitude), but the high frequency pattern is completely gone. No explanation as to why.

Last night, I spent some time balancing the scope better in RA and DEC.
The new version of the Android App reported an alignment error of 17 and 19 arc minutes, if that matters.

The conclusion is that the tests are inconclusive ...

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