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astronomerchris

Field Rotation Correction?

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Ok so I took this data about a month ago. I processed the data through PixInsight (I'm rather new to the software so maybe I missed a step). I think initially this field rotation was due to a polar alignment issue, although I don't know for a fact. In the picture you can see that after processing the bottom right is almost crystal clear but on the top left the image is fuzzy due to the field rotation. Is there something that can fix this? Even if I have to go into each individual file ( there are about 50 of them :( ) to correct something, I think that it would be worth it.

Thanks!

Christopher

post-27705-0-36362600-1357179262_thumb.j

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i have never used pixinsight but that looks very "noisy" to me DSS definitely would take care of rotation if that is what it is

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Sorry it's so noise, here's a better clip of it. The upload must have degraded it. I'm on a Mac by the way so DSS wouldn't help me sadly. I do have Photoshop CS6 but I am not sure if it would help or not.

Christopher

post-27705-0-57246700-1357201689_thumb.j

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You have to distinguish between two issues, visible field roation during individual subs and field rotation made visible only in the stack. Minor PA misalignment won't affect individual subs but might build up in a stack if you stacked using x-y alignment rather than x-y and rotation. PI easily deals with this in stacking.

I can't see the image clearly enough here, even in the second one, but what I can see doesn't jump out and shout 'field rotation.' Couldn't you put it on a free site like Astrobin and link to a large rendition?

Seeing an individual sub would help as well.

Distorted stars can come from chip tilt (focuser, camera issues), incorrect chip distance from any flattener or flattener/reducer or an inherently non-flat field from the scope. Are you using a flatenner with the Stellarview?

Feel free to send me a fullsize JPEG of a stack and a sub to look at. PM me for my direct mail address.

Olly

Edited by ollypenrice

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Looks to me like there is rotation between the subs which has not been taken out in the stacking. If you look carefully you can see that the objects towards the top left look like they have been badly sigma clipped in the stacking - this is a sure sign of mis-alignment.

NigelM

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You have to distinguish between two issues, visible field roation during individual subs and field rotation made visible only in the stack. Minor PA misalignment won't affect individual subs but might build up in a stack if you stacked using x-y alignment rather than x-y and rotation. PI easily deals with this in stacking.

I can't see the image clearly enough here, even in the second one, but what I can see doesn't jump out and shout 'field rotation.' Couldn't you put it on a free site like Astrobin and link to a large rendition?

Seeing an individual sub would help as well.

Distorted stars can come from chip tilt (focuser, camera issues), incorrect chip distance from any flattener or flattener/reducer or an inherently non-flat field from the scope. Are you using a flatenner with the Stellarview?

Feel free to send me a fullsize JPEG of a stack and a sub to look at. PM me for my direct mail address.

Olly

http://astrob.in/full/28883/ and http://astrob.in/full/28884/

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I don't know how to edit or delete my previous post so:

Sorry those links didn't work, I sent them to you through PM. By the way I am using a stellarvue large format CCD field flattener.

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