NGC1365 Southern Spiral Galaxy CDK17 F4.5 12 hours

[astronobob (Bob)]

Mighty fine Image result Greg, awesome view & details definately, tho was a little surprised to see a smidge residual noise remaining, or some kind of fine color blotchiness or something with 12hrs of 5min subs = 140 odd subs ?
Im guessing the reason is because of the filters, less light, inturn, more processing, streaching ? tho, 5min subs arent long, sorry if awkward question, but just trying to understand further basic principles etc, as 10 x 10min subs with stock dslr can be as smooth in many respects. Id understand if some residual noise left in the darker zones, tho I'm seeing things in the med bright zones as well ?
Dont get me wrong, It is and awesome and inspiring Image mate and I am sure there are reasons unkown to me, re question.
Rgrds !

[cazza132 (Troy Casswell)]

I am very interested to see results from a DSLR in this scenario. Greg has extracted some good Ha data too - I am sure a full spectrum or Ha modded DSLR could do. Dark frame subtraction still does wonders without cooling and using results from different nights would also help (dithering?) I so should have had my mod 6d fitted with cooling Yes, long exposures extending more than 10 min would become an issue when cranking beyond ISO1600. But, still performs pretty good - QE as good as any DSLR with deep wells that rival the best CCDs. SQRT(2) or less for lineal res with bayer, but you shoot all colours at once It would be very interesting to see how a DSLR would perform vs CCD on that photon gathering monster My answer would be the advantage with Ha with the CCD. And my cat just caught a cicada - lol. Greg - good work mate - you have some awesome work and look up to you as an astrophotographer. I had a crack at M33 (Triangulum), that made me realize that you just can't do that galaxy stuff without proper gear!

Im guessing the reason is because of the filters, less light, inturn, more processing, streaching ? tho, 5min subs arent long, sorry if awkward question, but just trying to understand further basic principles etc, as 10 x 10min subs with stock dslr can be as smooth in many respects. Id understand if some residual noise left in the darker zones, tho I'm seeing things in the med bright zones as well ?
Dont get me wrong, It is and awesome and inspiring Image mate and I am sure there are reasons unkown to me, re question.
Rgrds ![/QUOTE]

[astronobob (Bob)]

I agree cazza123, Its an awesome image, no doubt about it !
There is obviousely somethin I dont understand about CCD Mono cameras, filters etc ?
I see this type thing Im noticing in a few other images from various other IIS'sers also, so, im not picking fault anywhere here, just noticing something a few times and thought Id ask Greg as I understand he is very knowledgable in this/his field

[gregbradley]

Originally Posted by astronobob

Mighty fine Image result Greg, awesome view & details definately, tho was a little surprised to see a smidge residual noise remaining, or some kind of fine color blotchiness or something with 12hrs of 5min subs = 140 odd subs ?
Im guessing the reason is because of the filters, less light, inturn, more processing, streaching ? tho, 5min subs arent long, sorry if awkward question, but just trying to understand further basic principles etc, as 10 x 10min subs with stock dslr can be as smooth in many respects. Id understand if some residual noise left in the darker zones, tho I'm seeing things in the med bright zones as well ?
Dont get me wrong, It is and awesome and inspiring Image mate and I am sure there are reasons unkown to me, re question.
Rgrds !

Yes there is some residual noise there. Funnily enough part of it is processing as an earlier version I had showed less of that so part is a processing thing. But its simply the time required to build up enough signal to get above the noise ( of the camera and the randomness of the light signal reaching the telescope called shot noise).

Bottom line is even with a sensitive camera and a large fast optic you will still need a relatively large amount of data to get something like a galaxy (and this is a bright galaxy) to be noise free with the kind of pushed/stretched modern processing we do with Photoshop and other programs.

As far as 5 minute subs. They could easily be made to be 10 minutes, possibly 15 although I think 15 will start to burn out the core. 5 minutes was an optimum of tracking considerations (no off axis guider on this setup), the fact of large fast optics so I didn't want to blow out the core.

Originally Posted by cazza132

I am very interested to see results from a DSLR in this scenario. Greg has extracted some good Ha data too - I am sure a full spectrum or Ha modded DSLR could do. Dark frame subtraction still does wonders without cooling and using results from different nights would also help (dithering?) I so should have had my mod 6d fitted with cooling Yes, long exposures extending more than 10 min would become an issue when cranking beyond ISO1600. But, still performs pretty good - QE as good as any DSLR with deep wells that rival the best CCDs. SQRT(2) or less for lineal res with bayer, but you shoot all colours at once It would be very interesting to see how a DSLR would perform vs CCD on that photon gathering monster My answer would be the advantage with Ha with the CCD. And my cat just caught a cicada - lol. Greg - good work mate - you have some awesome work and look up to you as an astrophotographer. I had a crack at M33 (Triangulum), that made me realize that you just can't do that galaxy stuff without proper gear!

Im guessing the reason is because of the filters, less light, inturn, more processing, streaching ? tho, 5min subs arent long, sorry if awkward question, but just trying to understand further basic principles etc, as 10 x 10min subs with stock dslr can be as smooth in many respects. Id understand if some residual noise left in the darker zones, tho I'm seeing things in the med bright zones as well ?
Dont get me wrong, It is and awesome and inspiring Image mate and I am sure there are reasons unkown to me, re question.
Rgrds !

[/QUOTE]

Thanks Cazza.
A modded 6D could be a hot camera. The main obstacle would be the Bayer filter array which makes the camera more like a one shot colour CCD especially if cooled. I think the modded cooled 6D would do very well.

Greg.