a quick pacman and cocoon neb

[iwols]

hi just a couple of quick processed images.How do you know where to stop with imaging time?

 

 

 

Edited December 3, 2020 by iwols

[iwols]

[MartinB]

Nice images from what I suspect is quite a low amount of data.  What I like is that your process has been sympthetic to the data you have and you have worked very well within those contraints.  The Ha colour is spot on, same for the stars.

How much imaging time do you need is a very good question and a long involved one to answer properly!  Here is a good article by Craig Stark https://www.cloudynights.com/articles/cat/column/fishing-for-photons/signal-to-noise-understanding-it-measuring-it-and-improving-it-part-1-r1895

[cfpendock]

I agree with Martin regarding imaging time and star colour.  It may be my screen, but it seems to me that both images have a slight green tint???? I also agree that Craig Stark's paper illustrates very well the effect of signal to noise ratio.  In very simple terms, I always assume that this S/N ratio increases roughly according the square of of the image time, i.e. 4x image time gives 2x signal to noise.  I know it is not 100% correct, but it works for me.  So it is a law of diminishing returns.  16 x 300 seconds exposures will be twice as good as 8 x 300 seconds.  But to get twice as good as 16 exposures, I need 32 exposures, and frankly this can sometimes take too much time for me.  I choose the individual exposure time based on the longest time I can get a reasonable image with my sky conditions, and this is around 300 seconds for my colour Baader filters.  Longer exposure times tend to saturate some stars and picks up too much sky background "noise", and shorter exposure times sometimes doesn't appear to do justice to some of the fainter things.  Having said that, there is a good argument that twice as many exposures at half the time give good results. However, I think that other sources of noise from the camera etc become too great.

Confused?  Me too....

Chris

[iwols]

21 hours ago, MartinB said:

Nice images from what I suspect is quite a low amount of data.  What I like is that your process has been sympthetic to the data you have and you have worked very well within those contraints.  The Ha colour is spot on, same for the stars.

How much imaging time do you need is a very good question and a long involved one to answer properly!  Here is a good article by Craig Stark https://www.cloudynights.com/articles/cat/column/fishing-for-photons/signal-to-noise-understanding-it-measuring-it-and-improving-it-part-1-r1895

Thanks each image has 30 mins of each channel