Quote:
Originally Posted by Slawomir
From my reply below  |
Oh, missed that!
What's interesting is that most of your points in that original guiding graph, particularly in RA, are on one side of the axis only. Any idea why?? Mount out of balance (maybe deliberately of course)? But kind of invalidates the assumptions in all these simple calculations about what level of guiding accuracy is needed as they all assume a nice symmetric Gaussian!
(but I wouldn't make too big a deal of it as it'll make your FWHM smaller than the calculation based on RMS would suggest).
BTW, you mention the fact that stars are elongated when it's not guiding well. Could it be argued that it's the FWHM that matters at the end of the day, e.g. you
could get round stars when RA is a bit loose in guiding by deliberately making your dec guiding equally as bad! Ideally we want small FWHM in
both axes, and that, I'd suggest, should be the goal rather than just trying to make them the same value and have round stars? OK, I'm being pedantic, and both approaches are trying to get to the same end, but I'd suggest we shouldn't be assessing "are the stars round" to see if our guiding is good, but "are the stars small"? In my case, it makes a difference, as I tend to have slightly rubbish guiding in BOTH dec and RA, so get round stars - though a tad wider than they should be! Just an idle thought on a late Friday arvo!