Quote:
Originally Posted by dizzy2003
So initial tests (with asiair plus) doing 60 second subs guided and unguided have some interesting results.
Unguided appears to NOT have the double stars, but does have RA streaks with a similar frequency to guided (approx every other image).
Also trying different guide rates the spikes are proportional to the guide rate
0.5 guide rate produced 12.5'' spikes 0.9 guide rate produced 25 '' spikes and 0.25 guide rate produced 6'' spikes (Not sure what to make of that)
attached graphs and small subsection of the image of M20 as well as a full image.
Note scope is f9 100mm apo, so 900 FL no field flattener. using l extreme filter, cam is asi 533mc pro
The intermittent streaks in unguided imply to me its mechanical. But the guide rate being proportional to the spikes makes me thing electrical/comms So 
Maybe theres 2 issues.. |
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