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Old 02-07-2014, 08:57 PM
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codemonkey (Lee)
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Thanks mate, appreciate it :-)

I don't think this is drift. The stars have an unusual shape rather than simple streaking, and while the center of the image is fine, it gets progressively worse the closer to the edge (the supplied image being the the top right hand corner of a recent image).

I'd not noticed it before last night, but I'm not sure what it is. I'll have a look through individual frames and see how they look because I've only looked at the stacked result so far.

Thanks again!
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  #22  
Old 02-07-2014, 10:11 PM
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Eden (Brett)
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Lee --

Quote:
... and while the center of the image is fine, it gets progressively worse the closer to the edge (the supplied image being the the top right hand corner of a recent image).
This makes sense :-) I didn't realize that the image you supplied was a snippet from a full frame. I've had this problem in some of my images.

Field curvature and coma are to be expected in many telescope designs and refractors are not exempt from this, especially in products from the low end of the market (yours and mine). Refractors with a triplet lens design suffer from this problem to a lesser degree. A field flattener would help, but also double-check your focus because even a slight deviation from focus will amplify these off-axis aberrations.
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  #23  
Old 03-07-2014, 08:16 AM
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Asterix2020 (Paul)
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Hi Lee,

I think you have field curvature which is present in ED80's. The only way to fix it is a field flattener/reducer.

Check out this pics for comparison.

My ED80 before field flattener:
http://www.astrobin.com/full/88107/0/

With flattener:
http://www.astrobin.com/full/93400/C/

I bought this flattener since it it designed for the ED80. I couldn't find it locally.
https://www.teleskop-express.de/shop...ED-80-600.html
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  #24  
Old 03-07-2014, 07:50 PM
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codemonkey (Lee)
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Quote:
Originally Posted by Eden View Post
Lee --



This makes sense :-) I didn't realize that the image you supplied was a snippet from a full frame. I've had this problem in some of my images.

Field curvature and coma are to be expected in many telescope designs and refractors are not exempt from this, especially in products from the low end of the market (yours and mine). Refractors with a triplet lens design suffer from this problem to a lesser degree. A field flattener would help, but also double-check your focus because even a slight deviation from focus will amplify these off-axis aberrations.
Quote:
Originally Posted by Asterix2020 View Post
Hi Lee,

I think you have field curvature which is present in ED80's. The only way to fix it is a field flattener/reducer.

Check out this pics for comparison.

My ED80 before field flattener:
http://www.astrobin.com/full/88107/0/

With flattener:
http://www.astrobin.com/full/93400/C/

I bought this flattener since it it designed for the ED80. I couldn't find it locally.
https://www.teleskop-express.de/shop...ED-80-600.html
You guys are legends, thanks muchly for your help :-)

I'll chuck that on the list of things to convince the wife to let me buy...
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