On Fri, Jul 9, 2021 at 12:27 AM, Brian Valente wrote:
Hi Nick
?
>>>Is there a way to analyze what kind of impact this actually has on images ??
yes - look at your images. You can also do quantitative analysis such as FWHM and Eccentricity.??
?
?Right now, you are guiding?sub-arcsecond, which is a fraction of a pixel difference in your final images, so I suspect any additional mechanical tweaking will result in literally no difference in your images.?
?
Guiding sub-arcsecond is not nearly sub-pixel in many cases.? For instance for my APS-C sized ASI2600MC and a 1380 mm FL Newt? I have norm([6249;4180])=7518 pixels on the diagonal for a FOV of?(28/1380)*(180/%pi)*3600=4185 arc seconds.? Pixels per arcsecond is therefore 3.6.? However this is an MC so the resolution is cut in half leading to 7.2 arc seconds per pixel.? For 1 arc second total RMS (keep in mind this is plus or minus which is a factor 2), a point source gets smeared out over 14.4 pixels.? For quality AP the goal should be 0.25 arc seconds total RMS.? For an MM cam that would be about 1.75 pixel.? When you say sub-pixel I presume you mean 0.5 pixel or so.? Unless I have an error in the math, I think you are overly optimistic by a factor 15 to 30 for many cases.
