Last night (Sat) the seeing conditions were amongst the best I have experienced for a while and after slewing to a bright star to focus the rig, I slewed to the nearby Moon and began a series of 2000 frame captures.
It wasn’t until I worked my way up to the edge of the Moon and saw the blurry limb that the penny dropped; I still had the Bahtinov Mask on the ‘scope - doh. By then, it was too late as the seeing dropped off to just good from excellent.
If you look carefully at the specular highlights, such as mountain peaks or crater rims that catch the light, you can see the unmistakeable Bahtinov mask diffraction patterns…
Once I realised what I had done, I saw the funny side to it but by then, the seeing had dropped off with a change in wind direction and warmer air blowing in.
I decided to process the 2000 frame AVI’s none the less and was astonished at the seeming lack of degradation. I then remembered the topic of “Apodizing Masks” as used by double star observers and a Google search turned up the following useful sites.
http://www.telescope-optics.net/apodizing_mask.htm
http://www.astronomyhints.com/apodize.html
http://www.lcas-astronomy.org/articl...tegory=general
So, it seems I got lucky and the Bahtinov Mask somehow supressed the detrimental effects of the low frequency seeing by diffusing the incoming signal?
When I look at thumbnails of the 1024 pixel JPGs in Lightroom, they seem hazy but when viewed at full size, the detail still comes through. All these images have been re-sampled from the full res originals of 1920x1200.
Cheers
Dennis