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Joeistotalycool

Out of collimation refractor?

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Hello, I was recently capturing images through my Skywatcher ED 80 and I realised I had purple and green fringing around the stars. I looked at previous images and it turns out I've had the problem for a few months. I'm not quite sure if the problem is the focuser or the glass. Im using a canon 1200D with a astronomik CLS clip in filter and a 1.25 Baader UV IR cut

I supplied the stacked raw Tiff.

Any suggestions would be nice :)

Autosave.tif

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That’s probably just chromatic aberration, the ED80 has a relatively short focal length. Is it on brighter stars or everything? I guess collimation would more likely manifest itself as coma or poor focus. I should your focus still ok? Is it across the whole FOV or just the edges or one side?

B28FCAFC-B058-4E52-8800-60BB30CAC70F.jpeg

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6 minutes ago, Anton Astro said:

That’s probably just chromatic aberration, the ED80 has a relatively short focal length. Is it on brighter stars or everything? I guess collimation would more likely manifest itself as coma or poor focus. I should your focus still ok? Is it across the whole FOV or just the edges or one side?

B28FCAFC-B058-4E52-8800-60BB30CAC70F.jpeg

It appears on almost all stars, bright or dim, across the whole fov

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11 minutes ago, Mark at Beaufort said:

The easy way to check if your refracting needs collimating is to use a cheshire eyepiece. Here is a link to the procedure produced by Phil - http://philjay2000.tripod.com/usefulstuff/adventures.pdf

Thanks, I was going to get one eventually, as I was planning on getting a newtonian. They are a lot more versatile than I thought!

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Joe I am not an astro photographer but I always thought that the Skywatcher 80ED was highly rated for imaging. Its has  Ohara FPL-53 extra-low dispersion glass for the ED element, which virtually eliminates chromatic aberration, and top quality German Schott glass for the matching Crown element.

I would start with checking the collimation.

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35 minutes ago, Mark at Beaufort said:

Joe I am not an astro photographer but I always thought that the Skywatcher 80ED was highly rated for imaging. Its has  Ohara FPL-53 extra-low dispersion glass for the ED element, which virtually eliminates chromatic aberration, and top quality German Schott glass for the matching Crown element.

I would start with checking the collimation.

I would agree Mark, the 80ED has an excellent reputation for being well corrected despite on being a doublet.

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I downloaded your autosave tif file and can't really say that I'm seeing what you are describing.

I'm seeing what I would interpret as issues with field flattener (if you are using one). A bit of tilt and spacing correction might sort it out - I'm not 100% certain that it indeed is the case.

If you are not using field flattener, then yes it might be collimation issue.

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4 hours ago, Mark at Beaufort said:

The easy way to check if your refracting needs collimating is to use a cheshire eyepiece. Here is a link to the procedure produced by Phil - http://philjay2000.tripod.com/usefulstuff/adventures.pdf

Glad my guides are still helpful.

CA is not necessarily a collimation problem, by all means check it as per my guide but collimation issues will be coma on the stars and yours look reasonable in your image. However, like vlaiv above, I cannot see what you describe in your image.

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