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Guide performance

Started by RolandC, 07/25/2017 02:04PM
Posted 07/25/2017 02:04PM | Edited 07/25/2017 02:06PM Opening Post
The question has come up as to what RMS guide error is allowed to get round stars in a typical Astro image. I ran a series of tests with a 17" F8 astrograph on a 1600 mount on a reasonably steady night that produced 1.5 to 1.9 arc sec FWHM stars in a 5 - 10 minute exposure. Image positions are dithered after each exposure by 1 - 5 pixels.

Here is a screen shot showing Guider graph, Guider settings and resultant star size, roundness, etc. during period of steady seeing.

Guide star pixel scale is 1.32 arc sec/pixel, RMS error is .18 arc sec for X axis, .275 arc sec for Y axis. Stars measure flatness of .008 which is quite round even though X and Y axes RMS is quite different.

Rolando

Attached Image:

RolandC's attachment for post 60972
Posted 07/25/2017 02:11PM #1
Slightly worse seeing on this next series. X is 0.88 arc sec RMS, Y is 0.3 arc sec RMS. Stars are round to a flatness of .023

Rolando

Attached Image:

RolandC's attachment for post 151756