Strange visual effects - is it seeing, collimation or tube currents?

[IanH]

Hi,

It was a lovely clear sky here last night so I had the C11 out for a session with Jupiter.

It was a very nice view with a lot of excellent detail and colour, but there was a strange effect - the moons had flares coming off the top and sides like a viking helmet!, while the bottom of the moons were in perfect focus. Also, I would say that the top half of Jupiter was probably a bit less in focus than the bottom half. This was seen in all eyepieces.

The OTA was well cooled - it lives in an unheated shed and was brought outside about 4 hours before observing, the temperature drop over the observing period was only about 5C. Also I have a lymax cat cooler, which was on it for a good hour before observing.

So, do you think this is this local seeing? I am looking at air across South West London and Slough. Or the jet stream or maybe collimation - I have tried the star test and not seen problems, but the seeing was typically poor then, so it was hard to tell.

My biggest worry, having read around a bit, is that it's mirror turbulence - the effect of a warmer layer of air just above the surface of the mirror. If that is the case, is there an easy way to solve it? Some people have gone of the length of drilling holes in the back and installing fans etc.? With my diy skills I'd probably knacker it completely.

All advice appreciated,

Cheers, Ian

[IanH]

apologies I should have put this in general observing ... any idea how to move it?

[IanH]

I'll copy this into the equipment section - apologies for it being in the wrong category in the first place.