Chromatic abberation when observing the moon

[lookup38 (Robert)]

Hello all -

the other night, when I was looking at the nearly 1/2 full moon at 200x in my scope (8' f/6 dob with a custom .98 strehl mirror), I noticed something. When I looked at the lunar limb, there was a yellow band between the lunar limb and the dark sky background. I saw it in both a tv plossl and a off brand plossl. Seeing was pretty poor and that level of mag did not hold up well in the scope, so I did not stay there, but I would like to know what I was seeing. Is that chromatic aberration? and if so, was it caused by the ep, the scope, the atmosphere, or all 3?

thanks in advance for your help -

Robert

[Blue Skies (Jacquie)]

Its not the mirror or the atmosphere so its most likely the eyepieces, which have lenses so yes you were getting some chromatic aberration. Something as big and bright as the moon it's inevitable that going to see some. I find it's quite common but I usually don't worry about it. If it bothers you try using a neutral density filter to tone down the brightness without loosing the natural look of the moon (or planet).