Was really lucky with this one. Had roughly set up the mount to test (between clouds) that the focal plane tilt in the camera was fixed (it was) when a clear patch came through. No time for a proper polar alignment, so just did a quick and dirty 2 star alignment as it was – moon was up, so went to a bright Ha target, calibrated PHD and started imaging as quickly as possible.
It was a bit too windy for the mount, so kept the subs short at 200secs and got 9 usable ones for ½ hour total. First time I had tried Ha and it was interesting processing the data - lots less signal to play with. This is only part of the image and it has been scaled down by 0.5 to fit in the posting limit.
Got to be happy with that, Ray! The bok globs punctuate the field very well. Its amazing for such short exposures too. For a first Ha image, you're well on your way to producing some cracker images. Good work.
That is one superb shot Ray, really well done. Exceptional actually. Nice work.
Thanks for the comments Marc. Good to have something to post when I did not expect it - usually things work out the other way.
Quote:
Originally Posted by Larryp
Looks great!-lots of detail
Thanks very much Laurie
Quote:
Originally Posted by RickS
Looks great for 30 minutes, Ray!
Thanks very much Rick. I was a bit surprised to get a reasonable image in such a short window. Really looking forward to seeing what the system will do with longer exposure time.
Quote:
Originally Posted by jase
Got to be happy with that, Ray! The bok globs punctuate the field very well. Its amazing for such short exposures too. For a first Ha image, you're well on your way to producing some cracker images. Good work.
Thanks for the encouragement Jase. Quite a way to go yet, but it was exciting to see this "first step" image take shape as it was assembled by the processing software.
Excellent Ray that bit of the chicken just looks so cool
Mike
Thanks Mike - it is interesting. Also, looks like your new obs is coming along well.
Quote:
Originally Posted by clive milne
Ray,
I hope you are still going to go back to M83 for colour data.
I certainly intend to Clive - just waiting for the clouds and moon to get out of the way. By the way, the Rowe coma corrector works exceptionally well - thanks for the advice.
By the way, the Rowe coma corrector works exceptionally well
It's a curious thing, others have tried and failed with that corrector even though it leaves little to be desired optically (when used with a small format sensor). I would put that down to BFD spacing errors giving the Rowe corrector a bad rep' when it isn't applied properly. You seem to have it nailed though.
I'd be interested to see one of your full frame raw images at native resolution. Without seeing that, I couldn't say for certain, but I suspect your system limit is charge diffusion. For a given focal length, that's as good as it gets from the perspective of the application of opto-mechanical principles pertaining to ccd imaging.
It's a curious thing, others have tried and failed with that corrector even though it leaves little to be desired optically (when used with a small format sensor). I would put that down to BFD spacing errors giving the Rowe corrector a bad rep' when it isn't applied properly. You seem to have it nailed though.
I'd be interested to see one of your full frame raw images at native resolution. Without seeing that, I couldn't say for certain, but I suspect your system limit is charge diffusion. For a given focal length, that's as good as it gets from the perspective of the application of opto-mechanical principles pertaining to ccd imaging.
regards,
~c
Hi Clive. Will post a raw frame when I have one without field rotation.
For interest, I modelled the system as an obstructed aperture PSF convolved with Gaussian atmospheric blur. Also included a simple charge diffusion term and found that diffusion is not a major issue for this system until it is above about 20% - it would be much more of a problem in undersampled systems. I could not find any crosstalk data for the icx694 (or anything else for that matter), so used 10% for the graph attached. I do not have any independent measure of seeing, so the starting point of 1.5 arc sec was a guess, but the data fit well enough that it seems reasonable to say that the system is practically seeing limited. The real data includes tracking, scattering and stray diffraction (particularly the spider), but the model does not, so the divergence of the curves seems reasonable.
