Subtle glow surrounding stars/planets.

Seeing this effect through my 8 inch Dob, but the primary mirror does appear in need of a cleaning - pretty badly actually. Could this be due to a dirty mirror? I've tried various different eyepieces and even rotated the eyepiece while viewing and the glow remains stationary (no movement of glow rotating with eyepiece) - so I'm assuming the glow is caused by the mirrors. I do plan on cleaning them, and I'm aware that a dirty mirror will cause a dimming of the image, but has anyone else seen a glow when viewing with dirty mirrors? The glow is subtle and I'm seeing it regardless of the magnifying power used. This scope was purchased new by me in 1998 and I've only cleaned the mirrors once before as far as I remember. Coatings still look good to me - just a very noticeable coating of dust, pollen, or whatever when doing the dreaded flashlight test. Thanks for any input. Dave Sewell

Dave,
IF the mirror is pretty dirty, then the scatter from the dust and dirt could cause a glow.
There would have to be a bit of dust, enough to show just looking at it without a flashlight.
A good cleaning, would probably be in order after this amount of time. Just do it carefully.