M13 - 18 Sept 05

Thanks Guys,

Michael: Like Dave, I'm excitedly looking forward to seeing your results when you get up and running with your observatory

I think Dave's right, its mostly because those two really bright stars just happen to be in the corners. Note how the 'coma' (or whatever it is) points from the edge to the center, if it were a misalignment of the sensor with the optical axis, wouldnt they either be going the same way (in extreme misalignment) or only be on one side of the image?

I dont really know?

BTW I would normally crop off the extremities of an image anyway.

Dave - not sure what you have going in that image but its pretty funky.

If you crank up the levels (white) you can see what looks like vignetting. It could be a strange gradient but I'd bet vignetting is the cause.

The funky part is the two bright stars, top right and top left, are outside the vignetting... And at least one star to the very far left (top corner) shows no coma... No other stars show any seriously visible coma though...

Answer? Just crop it as yopu say.

The image is nice - there seems to be a just-perceptible elongation of the stars, especially the brighter ones. The colour seems a little blue also. But its always hard to perceive colour on our collectively poxy uncalibrated monitors

Keep 'em coming Dave

Cheers

Dave McD

if it were a misalignment of the sensor with the optical axis, wouldnt they either be going the same way (in extreme misalignment) or only be on one side of the image?

I wouldnt worry about it been so near the edge, its just that when i saw one was read and the other was blue, I thought maybe one was inside focus while he other was outside the focus ????
of course, they could actually be red and blue stars :lol: :lol:

I noticed the vignetting, hence the dark frame Q or would that be flat frame ?? again its very minor