Collimating C8 OTA

Couple of weeks ago I finished collimating my C8. I used previously built artificial fibre star and SPC900NC camera. I did collimation in the "basement premises", along the 25m long hallway. I also judged collimation with short focal length eyepiece. From my earlier planet images, I saw that the collimation was "way out" a lot... This causes loss of image details, and blurry edges to planets (like Mars).

I got a better collimation by ajusting one screw, approximately 1/5 turns. Images are taken without any barlow lens. Focus patterns - before collimation:
Focus patterns - after collimation:
In / out focus pattern is now much more symmetric and focused star appears without "comets tail" effect. When there is any need to tweak collimation, that is better to do "in the field"....

I also decided to make a test, is it possible to capture airy disk & diffraction rings. I got some... TeleVue 3x barlow was used. Image is stacked and resized to 400% of original size. Airy disk became visible, and first diffraction ring (although not uniformly). On some parts, there are traces of second diffraction ring (?) visible. The large faint disk around star, that I do not where it came from. If anyone knows, leave comments...
Two videos I also took of artificial star. Fist one with precise focusing (1) and second about disturbances in the video (2), caused by air movements.