Is image problem due to mirror?

Subject: Is image problem due to mirror?
From: (Doc)
Date: 22/08/03 14:05 Romance Daylight Time
Message-id:

I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

Whilst it may be a mirror problem or eyepiece quality problem or a collimation
problem, I don't think anybody mentioned the possibility that your scope was
warm. It takes quite a while for the optics and mount to cool down after a warm
day even when it is kept in the shade, and this can cause prominent air
currents to distort the image. If the tube is almost horizontal the "flare"
often appears to one side of the image as the warm air rises inside the tube
and flows out of the open end. If you defocuss the image or remove the eyepiece
and look into the focusser, you may even see the moving currents.

Phil