Star testing oddity

I have a high end 80mm triplet, tested at 120X. On infocus it produces a very nice star image with ten concentric rings all of same width, density, and brilliance with a small tinge of yellow, the outter ring is not quite even all of the way around it's circumference. On infocus I can focus down to a single ring. On outfocus the image is a total disaster, the rings are barely visible, more yellow tinge and these odd bubbles. I rotated the eyepiece and the bubbles did not move. The bubble are approximately 20% the size of the star image. I have searched H.R. Sutter's book on star testing and I can find not explanation for this oddity. Any ideas would be greatly appreciated.

Are you using a diagonal?

Bubbles might be dust spots on the lens, or perhaps on the diagonal mirror.

Rolando

Take a picture with a digital camera thru the eyepiece and post it.

Rolando

I wonder if these could be floaters within the eye? Do they change appearance if you use the other eye? Outside focus, the star will come to focus somewhere in the vitreous humor inside the eye. Any microscopic imperfections there would be greatly enhanced and might be perceived as "bubbles." Inside focus there is no focal point within the eye, so these floaters would be greatly reduced in appearance.

I was thinking floaters in the eye, too.

Take a look at some of the images shown on Abberator at the following link:

http://aberrator.astronomy.net/scopetest/html/refractor100_8.html

The pics for Refractor_100_3, 5, and 6 are very similar to what you have described. I don't recall ever seeing an explanation that made sense to me.

I have a bit of trouble with floaters and I don't believe this is the cause. Floaters don't stay put, they float.

dan