The Horse Head in HaRGB

[Jkulin]

On 07/02/2019 at 15:23, Rodd said:

Would that it were possible for a G2V calibration to solve my "I need more data" problems

I would guess that gathering the right ratio of light has got to be a goo thing

[Rodd]

35 minutes ago, Jkulin said:

I would guess that gathering the right ratio of light has got to be a goo think

Yes but I do not think the number of subs represents this once you get past a sufficient quantity.  If you processed an image with 30 hours of data split 10-10-10, there would be no difference between that and one split 8-9-13--especially if you have dark, non-turbulent skies.  By this time you would have gotten all the signal available and kept the noise down as much as possible.

Rodd

[VNA]

Beautiful capture of the Horse Head--thank you for sharing.
Enlarged, it is really impressive with details and colors.

[Jkulin]

8 hours ago, Rodd said:

Yes but I do not think the number of subs represents this once you get past a sufficient quantity.  If you processed an image with 30 hours of data split 10-10-10, there would be no difference between that and one split 8-9-13--especially if you have dark, non-turbulent skies.  By this time you would have gotten all the signal available and kept the noise down as much as possible.

Rodd

Hmm, I'm not sure about that Rodd, I'm sure Peter would correct me if I am wrong but the number of exposures generally affects the noise and detail, using the G2V principle reduces the amount of time to get the same balanced image or that is how I understand it, and giving the correct time for each colour may allow you to gain greater detail and reduced noise, potentially with less time to achieve similar results.

Peter has exceptionally dark skies where he lives and his images really contain small numbers of subs in comparison with what I and many others have to do, his optics are superb and fast and he collects a balanced number of subs to achieve what many people spend far longer obtaining similar detail, there has to be an underlying reason for such great images in relatively short periods of time in this images case just over 3.5 hours.

Talking with Peter, I firmly believe in what he advises with regards to G2V, the only problem is that since deciding to go down that route, I can't prove it as since October we have only had 6 clear nights and for one reason or another I could only take advantage of half a night!!!

ATB

[Rodd]

4 hours ago, Jkulin said:

Hmm, I'm not sure about that Rodd, I'm sure Peter would correct me if I am wrong but the number of exposures generally affects the noise and detail, using the G2V principle reduces the amount of time to get the same balanced image or that is how I understand it, and giving the correct time for each colour may allow you to gain greater detail and reduced noise, potentially with less time to achieve similar results.

Peter has exceptionally dark skies where he lives and his images really contain small numbers of subs in comparison with what I and many others have to do, his optics are superb and fast and he collects a balanced number of subs to achieve what many people spend far longer obtaining similar detail, there has to be an underlying reason for such great images in relatively short periods of time in this images case just over 3.5 hours.

Talking with Peter, I firmly believe in what he advises with regards to G2V, the only problem is that since deciding to go down that route, I can't prove it as since October we have only had 6 clear nights and for one reason or another I could only take advantage of half a night!!!

ATB

 

My points are:

1) The number of subs he needs is so small that it has to be more on account of his sky (and skill) than GV2.  I believe that the benefits of using GV2 in poor skies where you need hours per channel would diminish to almost 0

2) Astrodons are reported to be very close to 1:1:1.  Maybe its true, maybe not.  But Astrodon seems to think it is.

I could prove this very easily by reprocessing one of my images after dropping what ever number of subs would be necessary to drop from each channel to achieve GV2 balance.  I would bet  that reducing the number of subs in my image would not lead to improvement.  (fewer subs, or less exposure on subs amounts to the same thing.....in this case.  Now, if peter processed my image without GV2 balance, there would be an improvement.  If the data was collected from a dark sky, the data would be better and there would be improvement.  If guiding was better, if focus was better (hard to get better optics), My point is there are many reasons why Peters images are so good.  I think GV2 is not nearly as significant as these other reasons

Rodd

[Jkulin]

I use Chroma filters Rod which are virtually identical to Astrodons and you can see my G2V ratios.

Peter is away in Spain so may not be able to reply, but rather than spoil his thread, I’ll Leave you to your own thoughts.

ATB

[Rodd]

7 minutes ago, Jkulin said:

I use Chroma filters Rod which are virtually identical to Astrodons and you can see my G2V ratios.

Peter is away in Spain so may not be able to reply, but rather than spoil his thread, I’ll Leave you to your own thoughts.

ATB

Never heard of discussion ruining a thread. Most good threads trigger some form of discourse and the best trigger debate. 

[toxic]

superb image and superb processing Peter  

[RayD]

@Rodd and @Jkulin I think maybe you could be misunderstanding each other?  

My understanding is that G2V calibration is about colour balance, and reducing the number of unnecessary subs taken in any one channel, but not reducing the number or length of them in the first place to get above the noise floor.

G2V will, theoretically, give you balanced colour data in the first instance meaning, if you have it spot on, you should be able to apply an identical stretch to each channel without any one being stronger than the others. 

Ultimately it will mean you are not taking 50 red subs and effectively ditching the data during processing, when you only actually need 42 to balance the data with the other channels. 

This is my understanding, but it is an interesting concept which I've looked at on more than one occasion, although not adopted.

Edit: Great image, Peter.  I know what you mean about the trails, I had a short session on this target with my one clear night in Spain recently and was amazed at just how bad it is.

[Guest]

Amazing image!

[Jkulin]

I think you said Ray what I was trying to get across, i.e. less subs to achieve the same colour balance

[RayD]

11 minutes ago, Jkulin said:

I think you said Ray what I was trying to get across, i.e. less subs to achieve the same colour balance

That's exactly it, John.  What I think Rodd is saying is that if your 'weakest' channel doesn't have enough subs to get above the noise floor, then you still need more subs, which is also correct as the other 'balanced' data will also be below the noise floor.

G2V is definitely interesting and should make processing easier as the channels are starting from a more balanced point, and, of course, who wants to take 50 subs in a certain channel when you only need 42?  It's probably also more applicable to long exposure CCD imaging that CMOS.

 

[Rodd]

A main point is that one will shoot until the noise level is where you want it--color balance is only part of the equation.  If noise is high, one shoots until signal over powers it.  That may take allot of subs (integration time for CCD).  That's why I said I wish it were so that G2V calibration could reduce the need to collect subs.  The number of subs for me is predicated upon noise level--not color saturation.  In a laboratory (perhaps like Peters sky) aka "on paper" the theory sounds great.  But the messy world of compromised sky--G2V must take a back seat to noise supression and signal growth. 

Rodd

[AstroAndy]

Hi Peter

I can imagine this being on the cover of a book about astrophotography.

- Andy -