I have a Meade Super Plossl 32mm eyepiece that exhibits an odd (and seems fatal) flaw - in the image there are two or possibly more concentric rainbows. Is it the coating that is flawed or what?
Peter
Anything actually. It shows up even holding the eyepiece on its own and looking through it. If you hold it and look down the tube, there seems to me to be a pattern of multiple rainbows at the front and the back ends of the eyepiece - as if there was a defect on more than one optical element. The artifact does not occur only when the eyepiece is in the scope but it is there as well.
I am begining to wonder of someone (previous owner) hasn't perhaps used a cleaning agent of somer description on this and damaged the coatings.
Most likely you are seeing interference rings (Newton's rings)... glued glass elements are not glued any more.
Did you dropped it on the hard surface or hit it somehow?
I can't vouch for it's life before me I'm afraid. Although I confess that one of the less amusing adjuncts to increasing age is a paralell tendency to drop everything at least twice. But not eyepieces, wine or .. well that's about it really.
Peter
