A few galaxies.

tilbrook@rbe.ne (Justin Tilbrook) · #1 25-09-2012, 05:26 PM

Hi,

Galaxies, I find damn difficult to process!!

Especially when the overwhelming feature is back ground. Anyway Iv'e had enough of playing around with them, so here the are good or bad.

NGC 1365 and friends, 5 minute subs at ISO 800 a total of 90 minutes.

Grus quartett, 5 minute subs, at ISO 800 a total of 60 minutes.

Cheers,

Justin.

Paul Haese · #2 25-09-2012, 06:27 PM

Lots to see in both images Justin. Colour balance needs just a little attention in my opinion. All the rest looks good.

marco (Marco Lorenzi) · #3 25-09-2012, 06:55 PM

Nice shots Justin, the Fornax group is on my to-do list too

Clear skies
Marco

David Fitz-Henr · #4 25-09-2012, 09:39 PM

Nice shots Justin, especially for only 90 / 60 minutes total exposures - you should add some more subs and you will bring out even more detail.

Jbunky86 (Jason) · #5 25-09-2012, 09:59 PM

Fantastic mate

tilbrook@rbe.ne (Justin Tilbrook) · #6 26-09-2012, 05:55 PM

Quote:

Originally Posted by Jbunky86

Fantastic mate

Thanks for that!

Quote:

Originally Posted by David Fitz-Henr

Nice shots Justin, especially for only 90 / 60 minutes total exposures - you should add some more subs and you will bring out even more detail.

Thanks David!

You raise a question though.
While my 8" f/4 is doing a good job, it hasn't the resolution of a larger scope or something with 20th wave optics. So how far do you go before hours of imaging become redundent because of resolution?

Or is that a how long is a piece of string question?

Quote:

Originally Posted by marco

Nice shots Justin, the Fornax group is on my to-do list too

Clear skies
Marco

Thanks Marco!

Can't wait to see yours, will give me something to study.

Quote:

Originally Posted by Paul Haese

Lots to see in both images Justin. Colour balance needs just a little attention in my opinion. All the rest looks good.

Thanks Paul,

Great to have your experienced eye on this site, all I need to do now is work out the best way to balance the colours.

Cheers,

Justin.

David Fitz-Henr · #7 26-09-2012, 07:16 PM

Quote:

Originally Posted by tilbrook@rbe.ne

Thanks David!

You raise a question though.
While my 8" f/4 is doing a good job, it hasn't the resolution of a larger scope or something with 20th wave optics. So how far do you go before hours of imaging become redundent because of resolution?

Or is that a how long is a piece of string question?

Well, I think that the seeing conditions would limit the resolution more than the accuracy of the optics - I used to get quite good resolution from my home made 200mm which had a cheap chinese mirror. I believe that the rule is that the SNR (signal-to-noise) increases as the square root of the number of exposures; so 25 stacked sub frames would have 25% better SNR than 16 sub frames (5:4 ratio). The optimal length of the sub-exposure is another issue (I think that CCDWare have a calculator on their website for this). With DSLR cameras, I believe that using a higher ISO rating increases the noise as well; also DSLR cameras are OSC (one shot colour) which means that each pixel is dedicated to a single colour (RGB - layed out in a Bayer Matrix), and so the "missing colours" for each pixel need to be interpolated from neighbouring pixels which thus affects the colour resolution (as well as the sensitivity per pixel). Others would have more experience with DSLRs than I so can probably offer better advice.