#1  
Old 26-04-2014, 09:27 AM
peter_4059's Avatar
peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
 
Join Date: Jun 2007
Location: SE Tasmania
Posts: 4,532
Breakthrough #2

In my quest for round stars I've spent a lot of time playing with the autoguiding. While I've tweaked the settings to get pretty consistent low RMS errors I was still seeing a peak in the RA error that was troubling me. This looked like a random peak and I've been trying to understand if there was some period to it that would allow me to track it down. This morning I tried a different approach - look line by line through the guide log and see if the error coincides with the dither command. Sure enough that's what it is - the PHD dither is a random amount of movement in the lock position up to a number of pixels set by a command, in my case issued by SGP that I've got set as 2 pixels. Because the magnitude of the dither is random this meant I could not spot the repeated pattern when looking at the guide errors - sometimes the dither is buried in the normal corrections.

The excel plots below show 500 dx values from the guide log - the upper plot includes the dither error while the lower one has the dither error removed. The second image shows the full session (2500 points)
Attached Thumbnails
Click for full-size image (GuideError.JPG)
114.1 KB27 views
Click for full-size image (GuideErrorFull.JPG)
128.5 KB26 views
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 04:16 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement