Quote:
Originally Posted by ericwbenson
Hi Tony,
What you have there is diffraction of an off-axis star by the anodized barrel of a tube inside of your OTA/focuser/imaging train. Starlight impinging at grazing angle on the somewhat smooth wall of a tube (with microgrooves from machining) produces that effect. You can possibly see it with your naked eye by observing the daytime sky (or a bright screen in a dark room) without the camera/filter wheel in place. (don't look anywhere near the sun obviously).
I had to solve this problem with my telescope. See the bottom of this thread here:
http://www.iceinspace.com.au/forum/s...d.php?t=105990
Good luck,
EB |
Thank you Eric, that is rather conclusive. The artifacts in the two images are virtually identical. I'm using a set of the cheap Chinese spacers for back focus & the inside surfaces are really quite glossy,
I'll have a go at coating them with flat black & failing that replace them with some of good quality.
Many thanks Eric,
Tony