Jump to content
  • Join the online East Midlands astronomy club today!

    With active forums, two dark sites and a knowledgeable membership, East Midlands Stargazers has something for everyone.

Curious abut blue colour from Eyepieces


Recommended Posts

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



Link to comment
Share on other sites

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?

Link to comment
Share on other sites


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 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.