Quote:
Originally Posted by JA
The main determinant for me is the obvious star trailing (RA streaks) on UNGUIDED images 3,5,7 and 8, but NOT, despite some minor star ovality, on the other UNGUIDED images 1,2,4,6 &9. It clearly demonstrates a loss of drive to the RA axis, probably for just under one second*.
I suspect, when the guiding is TURNED ON, the guiding system tries to compensate for the apparent star movement (caused by this intermittent loss of drive) and the guiding system injects that large 12.5 arc second correction pulse.
*. It would be good to know the length of the star trail in UNGUIDED images 3,5,7 and 8 in original image pixels. Can you zoom in on the RAW 3008x3008 ZWO533 image in Photoshop and measure the length of the star trail in pixels, either diagonally or as so many horizontal pixels x vertical pixels. I suspect it to be around 14 pixels based on your image scale and the possible tracking intermittent failure time associated with the 12.5 arcsecond correction pulse, whilst tracking at the sidereal rate, but who knows? All info helps solve problems.
Electrical issue more likely, given the apparent randomness/Irregularity(?) you reported of the fault, who knows.... more info
BTW - have you ever tested with everything PLUGGED OUT except for the mount, a camera (preferrably DSLR) and power to see if there's still star trailing?
Best
JA
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Am at work at the moment but I did zoom in on the really bad star trail (image 3) and it did look a similar length to the 12.5 arc second errors.
The short bursts of no tracking is what I assumed the original spikes to be. sidereal being 15''/s so I guessed at just under a second of no tracking to get the spike.
And I have had cases of just tracking the moon (during a lunar eclipse) over hours the mount falling behind where it should be
I guess in asiair after I changed the guiderate I should have recalibrated, but that doesnt really explain the doubling in spike, the spike should happen first (2 second exposure on guidecam) then the correction should happen, and if it needed a recal the correction should just be over or under.
Re power supplies am at work at the moment so will have to get exact details later. But I know the one on the mount is 14V and at least 3Amp (and was bought from possibly RS components) the power isnt shared its dedicated to the mount. The asiair has its own power supply shared with the asi 533 , some ebay 12v 6a power brick. the 3rd unused is also an ebay job.