|
Agreed,
With big fat stars I assume PHD does a statistically wieghted centroid calculation - so turbulence could affect the shape of the star if its say 4 * 4 pixels wide and PHD has to guess which pixel - down to a tenth of a pixel it should judge the centroid from.
So I try and aim for the smallest stars that I can fine that don't dim out.
When I see stars jumping that much in a frame by frame shot I wonder what chance PHD (or any guide software has and think either my MAK needs collimination - and urgently) or the DSI / MAK combination just isn't really good!
I still wonder why PHD is issuing such a large move that it takes the guide star out of the search frame?
Possibly the star jumps say 1 pixel left by seeing then PHD issues a 1 pixel left correction - sees no change so does it again - then the seeing reverts and the star is 1 pixel to the right - but if this is the worse case then the star should only be 3 pixel out of position - not 12 or 14.
Amazing how frustrating this is!
|