M57 'Ring Nebula'

[mikeyscope 242]

Firstly Happy New Year everyone!

Afraid I'm far from a frequent poster here on the forums, my last deep sky image through a scope was a DSLR image back in March 2012 ... around the time I stopped using film ... better late than never.     

Since then I have just made the move from DSLR to CCD during Spring 2015 and thought I would share my first finished effort, image files have been in my computer since September  ...just a fun experiment to see what could be resolved along with image scale, the image scale is 100% but cropped very slightly due to stack overlap so about 95% of total sensor area.

Colour wise this is my first LRGB aiming for rustic/teal which I feel is more natural ...rather than red/blue, also trying to retain subtle detail as best I can at this FL. and limited number of subs, thanks for looking, details below.

APM 175mm Refractor (barlow to FL 3780mm)

Atik 414EX (mono) at -20'C / Bin 1x1

EFW-2 Astrodon E-Series LRGB filters

Multiple exposure between 15s & 300secs

Sequence Generator Pro

Deep Sky Stacker

Pixinsight

CS6 Extended

M57 Ring Nebula NGC6720 by Mike Dickson, on Flickr

[wookie1965 2,868]

Cracking picture one of my favorite objects.

[ollypenrice 28,401]

Gosh, that's quite something. 

We don't see many Rings because of its small size. Brave of you to Barlow it, though! (This would be a good image for discussing the F ratio myth because, though you slowed your scope down to what, F16, the number of object photons remains unaltered. We don't see many DS images at F16 for that matter, but there you go!)

I'm certainly impressed. What did you gain from the short subs and might you have been temped to try longer?

Olly

[laudropb 7,176]

Very nice image of one of my favourite DSOs

[mikeyscope 242]

Hi guys

Thanks for your positive comments... appreciated! :-)

Olly if the calculation FL3780 divided by aperture still holds true when a barlow is used in the imaging train then this should be f21.6 ...but if any optical experts know better please correct me.

I could quite happily have continued with longer exposures but the limiting factor was the seeing conditions at this FL, in some images stars were eggs and others smeared as you might expect but enough passed to produce this result.

The other factor was simply that longer exposures than 360s were bordering on burning out detail while very short subs were too noisy.... many more short subs would have been required.

Also

I knocked a cup of tea over my imaging laptop today... puff of smoke from the fan outlet, intermitent fan running but display dead... thankfully it was just a cheap Celeron from the supermarket.

Mike

[Demon Barber 900]

Hi Mike,Wonderful image,now if it had been a drop of  whiskey   it might of evaporated before it ruined your pc, look forward to seeing you at Galloway later in the year. 

Regards and a happy new year.

Mike

[nameunknown 221]

Lovely image - Happy New Year!

P

[ollypenrice 28,401]

Sorry about the computer!

I'm very surprized you should say that you were over exposing at this kind of F ratio in 5 minute subs. I never worry about exceeding 65000 counts on the capture screen because this will usually just be the stellar cores and I regard them as either expendable or replaceable either from short subs or, if the long subs are in luminance, by not applying them to the RGB-only stars.

However, this is a very delicate result.

I think I might buy one of those children's spill-proof beakers for my office tea...

lly

[mikeyscope 242]

"Hi Mike,Wonderful image,now if it had been a drop of whiskey it might of evaporated before it ruined your pc, look forward to seeing you at Galloway later in the year".

Thanks Mike

I think flames from the fan outlet instead of smoke! ;-)

Unlikely to make Kielder/Galloway this year but things should be back to normal for 2017 ....will be great to meet everyone again. :-)

"Lovely image - Happy New Year!"

P

Thank you, you too. ;-)

"Sorry about the computer!

I'm very surprized you should say that you were over exposing at this kind of F ratio in 5 minute subs. I never worry about exceeding 65000 counts on the capture screen because this will usually just be the stellar cores and I regard them as either expendable or replaceable either from short subs or, if the long subs are in luminance, by not applying them to the RGB-only stars.

However, this is a very delicate result.

I think I might buy one of those children's spill-proof beakers for my office tea..."

lly

Olly, thanks for your input, yes I was surprised too to see overexposure in such short subs, that lower edge of the ring is one of these M42 or M31 type targets that requires a mixed sub lengths. I also tested on the Fetus Neb and clearly would need above 300s subs so depends on subject.

Adding the RGB helped neutralize the overexposure.... perhaps not so much burning out in the true sense so much as detail was being lost and becoming very bland.

Well guess this is what happens when you play with your toys at the kitchen table. :-/

Best wishes everone!

Mike