Omega Cen again

[peter_4059]

I know I've posted a number of these but tonight was the test of the new light box so here it is without any PS processing to even up the field (and no cropping either).

I'm quite pleased with the reduction in gradient in this image compared to recent attempts with this rig. I can still see a small amount of vignetting in the bottom right corner. I also think the dreaded bright bar at the bottom that I was seeing in recent images has been reduced quite a lot.

[Hagar]

Very very nice. I would love to see this image quite a bit bigger though.

Not sure of which camera was used but wonder if the bottom right is actually a remnant of amp glo from your DSLR. The rest seems prety good to me. Focus and all the other bits are great. The flats have made a real diference. Did you dark subtract also?

Keep at it Peter this is beautiful.

[peter_4059]

Thanks Doug. This was taken with the 400D and I used ICNR for the light frames. I didn't realise at the time but ICNR wasn't applied to the flats, I guess because the exposures were too short. There seems to be a bit of grain in the sky background and I'm wondering if this is noise associated with the lack of dark subtraction in the flats? I combined 10 flats and 18x2min lights for this image so there were plenty of subs to average out the random noise.

I had to shrink and compress this image a lot to get below the 200 kb limit. I did a number of sets of flats and some with the light box rotated 90 degrees so hope to be able to check how even the illumination is.

[troypiggo]

Yeah, very nice. Flat field. Also noticed the btm right corner, and immediately thought it looked like amp glow I've had on my images. Coming along nicely :)

[allan gould]

Really nice Peter - all the effort you have put into your astro gear and procedures is really paying off. Great focus and tracking as well.
I too would like to see the high resolution version

[peter_4059]

Cheers Troy and Allan. I'm wondering why the ICNR doesn't deal with amp glow if that's what it is? I've not seen this before.

How do you post a high res version?

[peter_4059]

I've done a repro tonight, this time with some dark-flats. I also realised that I didn't have the star selection set correctly in my original stacking. The background looks a lot less noisy in this one. I also did some analysis of how uniform the illumination is in my light box by comparing two sets of flats taken with the light box rotated 90 degrees and I'm happy to report the flats look identical in the two images when layered in PS with difference.

Bring on the new moon!

[allan gould]

To be honest it doesnt look like amp glow to me - it looks like its a miss-match between the ICNR and your light frames so that its subtracting too much. Try and experiment and put camera outside for 10 minutes and then take a series of dark frames then use DSS to subtract your flats and darks and see if you get it still in the RH bottom corner.
But the photo looks a lot better. I use the web function in PS to get a large frame at the 200kb level - thats all I can suggest.