M15 - 23-07-08 - C9.25 and Canon 350D

[jcm]

Not really planning to use the C9.25 for wide field stuff (the F6 130mm refractor much better) but I thought I would give it a go. Conditions not very good.

C9.25 at F6.3 , Canon 350D , 10 X 3mins.

John

[CELESCOPE]

Still come out nicely John. a very good Glob , but is there some Coma John, or is it my old eyes lol .

Dont answer that ehhehehe , yea had fog for my session, but still came up with a nice image ,will post later .

Rog

[jcm]

Yep , there is coma. The above is a full sized 350D frame. I could try to move the camera closer to the reducer. Using the Atik 16HR at F6.3 there is no coma at all.

John

[Beyond_Vision]

Thats a very crisp capture John it looks great. If it was coma wouldn't the stars be stretched pointing towards the corners?

[jcm]

Thats a very crisp capture John it looks great. If it was coma wouldn't the stars be stretched pointing towards the corners?

Not sure about this. In the bottom left corner there is obviously some "distortion".

It could be a slight misalignment of the 10 subs.

John

[steppenwolf]

The distortion bottom left is unusual as it appears to be a 'rotation' but there is no matching one shown at the top right corner! Leaving that aside, it is a nice colourful image.

[jcm]

The distortion bottom left is unusual as it appears to be a 'rotation' but there is no matching one shown at the top right corner! Leaving that aside, it is a nice colourful image.

Had a look at the individual subs. They all have the distortion in the lower left , so its not an alignment problem.

John

[RobH]

Very well resolved there John

Looks to me like somethings not quite at 90 degrees to the light path....coma would be visible equally at the corners.

Cheers

Rob

[jcm]

Very well resolved there John

Looks to me like somethings not quite at 90 degrees to the light path....coma would be visible equally at the corners.

Cheers

Rob

I have checked other images and it is not present in any of them. All I can think of is that the camera adaptor was not fully pushed into the 2" focuser and was at a slight angle.

John

[barkis]

That's a very attractive image John, and whatever the reason for the small anomaly in the left bottom corner, it doesn't detract from the overall picture. In fact if it hadn't been mentioned, I would never have noticed it. However the eyes of the experienced imagers are very discerning.

I'm sure you will discover the reason. It can't be much.

Ron.