A pushed NGC3199 in Ha before I add colour and probably curve it down a touch.
It’s a bit brighter than recent efforts, so allowed more stretching and sharpening. Its pretty deep I think, cant find many stretched examples.
Taken on an RCOS 10" RC Scope at f9, SBIG STXL6303E Camera and PME mount at itelescopes Siding Spring Observatory.
Processed with CCDstack, Star Tools and Photoshop. 28 hrs Total.
42 off 3nm Ha subs 40min each bin1.
Yep, looks very deep, Fred. I have about 12 hours of Ha from last year (and 9 hours each of OIII and SII.) You've definitely got some faint stuff in the Ha that I didn't catch. Well done!
I struggled to get colours I liked with this object when I tried to process it last year. Since then I've learned a bunch of new tricks and built a handy PI colour masking script so I reckon I might be able to do it justice now. Must put it back in my processing queue
Gee! in normal images of this object it is more of a Semi circle or cresent, you have essentially an entire circle or bubble here, almost unrecognisable, very cool Fred
Huge scale Fred and that has meant lots of detail. I spent a few minutes looking at the detail. A very deep image. I remember doing this object myself, I think it is worth getting the data for the colour. I reckon this will be a cracker once you have it done.
Not just deep but amazingly sharp. Good processing. I think Hershel's Ring is surprisingly very difficult, perhaps because the finest detail is also very faint. You've got it.
Yep, looks very deep, Fred. I have about 12 hours of Ha from last year (and 9 hours each of OIII and SII.) You've definitely got some faint stuff in the Ha that I didn't catch. Well done!
I struggled to get colours I liked with this object when I tried to process it last year. Since then I've learned a bunch of new tricks and built a handy PI colour masking script so I reckon I might be able to do it justice now. Must put it back in my processing queue
Cheers,
Rick.
Thanks Rick. Yes, the colour data I have doesnt look flash. I havent tried it yet, suspected it might be a problem hence this post 1st. I will try it though.
Quote:
Originally Posted by Stevec35
Pretty deep all right Fred - nice one.
Cheers
Steve
Thanks Steve, if you recon its deep, it is :-).
Quote:
Originally Posted by h0ughy
need a snorkel and tank - very deep Fred - impressive
Thanks Dave.
Quote:
Originally Posted by strongmanmike
Gee! in normal images of this object it is more of a Semi circle or cresent, you have essentially an entire circle or bubble here, almost unrecognisable, very cool Fred
Mike
Thanks for the detailed reply Mike. I dont know why others werent the full bubble, I didnt find it that faint even stretched the noise wasnt that bad.
Quote:
Originally Posted by multiweb
Very cool details. Deep as. This one is very faint.
Thanks Marc. Faint, mmm, do you know what the mag is perchance?.
Quote:
Originally Posted by Paul Haese
Huge scale Fred and that has meant lots of detail. I spent a few minutes looking at the detail. A very deep image. I remember doing this object myself, I think it is worth getting the data for the colour. I reckon this will be a cracker once you have it done.
Thanks Paul. I had a look at yours before actually, one of the few I could find. I think your colour was pretty good, hope to do as well.
Quote:
Originally Posted by Placidus
Not just deep but amazingly sharp. Good processing. I think Hershel's Ring is surprisingly very difficult, perhaps because the finest detail is also very faint. You've got it.
Thanks Mike. I did spend a fair bit of time processing, got to multiple masked layers in PS which I dont do so much these days, but cant say it was all difficult. Id be interested later to see how you went with it and what you found difficult.
Yes, I did find Kens before, he got an APOD for that. I think its pretty ordinary generally actually for depth and detail (colour isnt bad), but it was taken in 2008 !, I think he would cream that these days. His new web site is a bit corny IMO
Yes, I did find Kens before, he got an APOD for that. I think its pretty ordinary generally actually for depth and detail (colour isnt bad), but it was taken in 2008 !, I think he would cream that these days. His new web site is a bit corny IMO
Fair enough. Yes not real keen on those zoomable sites myself.
Fred, I would be interested to know the relative contribution to the noise floor from the background signal, dark current and read out.
regards,
c
OK, well, I dont know how to seperate those factors out really, perhaps you can tell me?.
The cam is a 6303 NABG fairly high QE at -35deg. When I apply darks, the noise doesnt change much. The subs were taken in pretty dark 1.5-2.5 arc sec skies, but the moon was up most of the time in varying degrees.
A typical 40min sub had 1000ADU in the darkest background, and 1600ADU in the brightest nebula.
OK, well, I dont know how to seperate those factors out really, perhaps you can tell me?.
The cam is a 6303 NABG fairly high QE at -35deg. When I apply darks, the noise doesnt change much. The subs were taken in pretty dark 1.5-2.5 arc sec skies, but the moon was up most of the time in varying degrees.
A typical 40min sub had 1000ADU in the darkest background, and 1600ADU in the brightest nebula.
What's your average ADU value in a master bias, Fred? Individual cameras and sensors vary but it should be possible to get a rough idea of read noise and dark noise from camera specs.
OK, well, I dont know how to seperate those factors out really, perhaps you can tell me?.
The cam is a 6303 NABG fairly high QE at -35deg. When I apply darks, the noise doesnt change much. The subs were taken in pretty dark 1.5-2.5 arc sec skies, but the moon was up most of the time in varying degrees.
A typical 40min sub had 1000ADU in the darkest background, and 1600ADU in the brightest nebula.
You should find some of that info in your Fit header if you use Maxim for capture. Not sure about other programmes.
Fred, the noise calculation is actually fairly simple.
In the frames when there was no interference from the moon, I take it that the background was on average 1000 adu?
What was the dark current?
(Assuming the same exposure time and temperature)
Hi Fred, my guestimate (from the manufacturers specs) is as follows. :
Read noise= 11e
Dark current @ 0C = 0.3e/s
Dark current doubling temperature = 6C
Therefore, @ -35C dark current= 0.00526 e/s
And for a 40m exposure, dark current= 12.6e
Dark noise is therefore 12.6^(0.5) = 3.55e (this is very good)
If the 40 min subs have a background level of 1000adu, and the camera gain is 1.47, the charge depth per pixel is 680e,
Therefore the shot noise is (680)^0.5= 26.1e
Total noise for the background per sub is therefore: (26.1^2 + 3.55^2 + 11^2)^0.5 = 28.5e
If you are using maxim, you will need to subtract 100adu from your baseline, in which case the shot noise value 24.1e and the total background noise will be 26.7e RMS per pixel.
Ergo, the sky background brightness is by far the dominant noise source in your system. That is mildly surprising considering you are using a 3nm bandpass filter @ f9.
Thanks Clive, I was actually collecting all what you said above when I noticed your reply. Thanks for those calculations.
I calibrated a sub with 1000ADU back ground and now the background ADUs are 20-40. A bias sub has 800ADUs.
Did you assume dark subtracted background of 1000adu?. Sorry for the confusion.
