First galaxy image M51

[old_eyes]

This is my first image of a galaxy, taken a couple of nights ago with a recently acquired second-hand Atik 16ic on a C6-SCT with a 0.63 focal reducer.

I didn't get the CG5-GT mount as accurately lined up as I would wish, and found that there was some very evident star trailing at 60sec exposures. Rather than waste the limited time I had available, I retricted myself to 15sec exposures.

The image came from 100 subs and 16 dark frames assembled in Dawn (which handled the rather noisy data beautifully - in constrast Deep Sky Stacker ran away screaming when shown the data claiming it could find "0 stars"). The image was then processed in Gimp with a histogram stretch, a bit of curve manipulation and then a little selective Gausssian blur (which might have been a mistake).

The pale bar to the right of centre is visible in frame with very little signal, and is not corrected by dark frame subtraction. I assume that I either need a stronger signal (a better aligned mount and longer exposures), or flat frames. Or would it be bias frames?

Compared to stunning images like Steppenwolf's http://stargazerslounge.com/imaging-deep-sky/101929-m51-two-scopes.html, it is pretty weak, but I was happy to get anything at all first time out with a proper astronomical ccd.

old_eyes

[steppenwolf]

This is a really great start to your CCD imaging. The light bar could be either light leakage or a BIAS issue. I would check what happens when you apply first a BIAS frame and then a FLAT frame.

[barkis]

It's not a competition, so don't ever feel you should not post your image on the grounds you don't feel it's good enough.

As Steve said, it's a very good first for you, and the more you do, the better you get. "Simples." Anyway, It's much better than the one I haven't done..

Ron.

[pvaz]

For a 1st image that's really impressive. Well done!

[old_eyes]

This is a really great start to your CCD imaging. The light bar could be either light leakage or a BIAS issue. I would check what happens when you apply first a BIAS frame and then a FLAT frame.

Thanks for the tip. Bias frames are no problem, but I am wondering where to get flats. You mention a number in your book, including using the twilight sky. I think that would be hard to do and still leave everything set the same way until full dark.

I don't have a lightbox or an electroluminescent panel, so I wonder if I can do something with diffuse light sources that are to hand. Our kitchen overlooks my astronomy space, and has fluorescent lighting behind heavy translucent roller blinds. Sort of a bit like a lightbox . Do you think if I just swung the telescope to look at the kitchen window and turned the lights on I could get a workable flat?

old_eyes

[steppenwolf]

Nik Szymanek, a very well respected astro-imager simply turns on the lights in his dome which is white inside and this seems to work for him - sadly, in a moment of genius, I painted the inside of the dome roof in my own observatory matt black so I haven't been able to try this method myself!

Your kitchen window/blind method seems quite feasible but you could add to the diffusion by stretching a white 'T' shirt over the front of your telescope. All you need is as evenly illuminated a light source as you can muster.

[old_eyes]

Nik Szymanek, a very well respected astro-imager simply turns on the lights in his dome which is white inside and this seems to work for him - sadly, in a moment of genius, I painted the inside of the dome roof in my own observatory matt black so I haven't been able to try this method myself!

Your kitchen window/blind method seems quite feasible but you could add to the diffusion by stretching a white 'T' shirt over the front of your telescope. All you need is as evenly illuminated a light source as you can muster.

OK - we'll give it a go .

Thanks for the help

old_eyes

[gary1968]

Nice one old_eyes. Better than my M51 efforts to date. A great start, thanks for sharing....

Gary

[ollypenrice]

Good start! I'm intrigued by the bar of light and would not put money on bias frames, but do try them. I think it looks like a light leak or some kind of reflection.

Flats are tricky. I use a light panel but you can make a box quite easily. As long as you have enough diffusers you don't need a particularly even light source. Beware, though, of daytime flats because light can get in all over the show, down the filter wheel most notably. I always do them in the dark, despite being cold, hungry and ready for bed!

Olly