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I was doing 11 sec exp through an lx90 {alt-az} and after some time i got some pretty bad field rotation.
Do you use drizze to get rid of that?
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Hi josh, yes I use drizzle to de-rotate and stack each image. Just select Drizzle from the "Image Process" drop down box. Select two stars in the middle third of the field of view and click on the "Settings..." button - I set all the Drizzle settings to 1.00 as I use Drizzle to de-rotate only at this stage. Press Start and as each image is taken it is stacked to make a final image.
I have used other astro software to stack images after capturing but I find Envisage seems to preserve colours better and it's all done at the scope! I use the FITS3P format and "Save all uncombined.." so that I can always reprocess later.
Here is a link to some excellent articles by Steve Hamilton on Drizzle on AutostarSuite.Net:
http://autostarsuite.net/files/11/articles/default.aspx
There is a really good article at AutostarSuite.Net on field rotation in Alt-Az mounts. Here is the link:
http://autostarsuite.net/forums/stor...ation%20V3.pdf
In a nutshell, the exposure time you can use without trailing depends on where in the sky you are imaging.
Dam!
