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Curious abut blue colour from Eyepieces


djpaul
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Hi All

 

Not been on here in ages but i finally got a chance to go out tonight with my scope

I have noticed when viewing the moon this evening with both of my Delos 10mm and 17.3mm and Sky watcher 32mm wide view eyepieces i get a thin blue line on the edge of the field of view from the moon.

Infact the sky watcher starts to get the line before it reaches the edge of the field of view

I then tried my Takahashi and Teleview 3-6mm zoom and i dont get the same thin blue line.

 

Im just curious as to what causes this and wondered if its just because they are wide view eyepieces

 

Any ideas what causes this

 

Paul

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Is it just on the moon or do you notice it also on a bright planet like Venus?

 

It cant be CA as I would have thought that would be on the object you are viewing, not round the edge (may be wrong on that), or, upon re-reading your post, was the whole of the moon in the FOV, in which case, it may be CA?

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Hi

I found the answer to this on SGL 

See below

 

Quoted to SGL

Many wide angle eyepieces show a thin bright rim around the field stop. It's know as the "ring of fire" effect although it's never that prominent I've found. Naglers show it, Ethos do to a much lesser extent. I've also seen in in other brands UWA and hyper wide eyepieces as well. It only seems to be there when viewing in daylight or when viewing a bright, extended object. I believe it's caused by diffraction of some type from the edge of the field stop 

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