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NGC 6992, The Network Nebula.

RobH

By RobH
in Imaging - Deep Sky

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RobH

RobH

Posted
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Hello all.

Finally back from 2 months away...feels great to be home :D:D:D

Here's one I've spent the last few weeks playing with.

I shot it last year with my 80mm, and decided then that I'd come back this year and do a hi-res version.

NGC 6992, also known as the ‘Network Nebula’, or ‘Eastern Veil’, is part of the Veil nebula complex in Cygnus.

It’s a supernova remnant, from a star that exploded about 5000 years ago, and is roughly 1400 light years away (distance measurements vary and are being refined all the time.)

This is the most technically challenging image I’ve done to date, and is composed of 4 main frames, each comprising of Ha, OIII, Red, Green & Blue, a total of 19 frames (Ha was 3 frames).

This meant that 5 separate mosaics using 2 different scopes were made, then registered using Registar, and aligned with Maxim. The mosaic sections were built using Maxim also.

The Ha was captured using the TMB152 @ F8 with an SXV H16, and the OIII & RGB used a William Optics 80FD and Atik 16HR @ F6.9.

The main nebula image is built up using an Ha luminance layer, Ha for red, Ha/OIII at 50% each for green, and OIII for blue.

A star layer was created separately using the RGB data and added to the narrowband data then the whole of this was then dropped into the RGB star background and the narrowband data erased except for the nebula itself.

There were a couple of small bits at the very edges where the frames left gaps, and, rather than spoil the composition by cropping too closely, I’ve copied some random starfield sections and pasted them in….so don’t treat this as a scientifically accurate image of the whole region…I do pretty pictures…not science!

Dual scope imaging isn’t quite as straightforward as it at first seems, and with this image I had issues with my green subs being slightly out of focus, causing green halos, and some flexure with the WO scope.

Also, as I’m using the 4 megapixel H16 image as the reference, and increasing the size of the 1.4 megapixel 16HR image to match, the 16HR RGB stars end up quite a bit larger than the H16 stars, especially as stars in Ha tend to be small at the best of times.

Also, my flats were useless, so I initially had gradient issues between the different frames which have taken much head scratching to deal with.

All a good learning process though.

I think that after this I’m going to work on a few simpler images for a while, as this has taken me about a month to finally process and I’m glad to finally put it to rest!!

Follow this link and click on the first image for the hi-res version....

pic and description page

Click on the image for the full sized version.

Imaged on several night during September 2009.

Imaging time was 22 hours 36 minutes.

Ha. 10 hours

OIII 7 hours 50 minutes

Red. 88 minutes

Green. 94 minutes

Blue. 90 minutes.

Cheers and merry Christmas to you all *wave*

Rob

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MartinB

MartinB

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Well worth the effort Rob, good to have you back. I like the Ha hue you have achieved and the star colour is great. Lots of fine detail in the nebula. I know what you mean about the processing. When imaged this earlier this year and found it hard work, getting the stars right is tough and you have done a much better job with them than me. I'm glad I'm not the only one who plays fast and loose with the stars. Don't look for super novae in my images!

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RobH

RobH

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Thanks all. I'm pretty chuffed with it, and looking forward to hopefully getting some clear skies and getting stuck in again, maybe with a high res M42 :D;):)

And you do all this without Registar? ;)

No Tim...I bought Registar a while back and it's opened up a whole new way of imaging for me. Doing the dual scope thing without it would be really tricky I think!

AK, The tour went well but was very long and I'm pretty pooped but enjoying relaxing and looking forward to Christmmas dinner :D

Cheers

Rob

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RobH

RobH

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Thanks John.

This is one of those images that I intend to add more to next year, as there is wonderful detail in the OIII which would benefit from some long hi-res subs, and, of course, I must also shoot the western veil in hi-res to add to it :D

Incidentally, sub length was 10 minutes for the Ha and OIII, and 240s for red, 280s green, and 300s blue.

Cheers

Rob

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ollypenrice

ollypenrice

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Thought you'd been quiet, Rob! You are right to be chuffed with that one, it's quite exceptional. I love the colours which are both rich and pleasantly soft. Also, despite the impeccable resolution, the nebula has retained its fluffiness - it looks nebulous, gaseous. In short, pure class.

As for green haloes, well, I hate green! It is the root of all evil in tricolour imaging. It has a disproportionate stranglehold on the colour balance. Grrrr....

Olly

PS I trust you'll be entering the Atik imaging competition? I can't play cos I'm putting up a prize but you have enough good stuff to sink a ship.

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RobH

RobH

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Thanks Olly :D

I originally mapped this as Ha®OIII(G)Ha/OIII(:), as the colour of the OIII regions is then closer to a standard RGB image, but the green halos were much worse, and although I struggled with them and had a certain amount of success in minimizing them, when I mapped the colours the way I eventually used them, the stars immediately looked much more natural, and, to mee, the red/blue of the nebula is more pleasing.

Re. the Atik competition.

I wasn't planning on entering.

It seemed a bit of a shambles last year to be honest,especially the way that the voting was done on the website by clicking on image names.

This would have worked well if they were all the same file size and loaded at the same speed, but the larger files took so long that they didn't stand much chance of a viewing. A thumbnails page with reasonably large thumbs would have worked well, rather than a list.

Also I don't exlusively use my 16HR, although I do have some images that I could submit.

The again....I might think again.....depends on how it's being run.

Cheers

Rob

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glowjet

glowjet

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Rob, that is another wonderful example of your patience, the result is so rich in colour, I see you have also had another publication in last months S&N of M106, you must be happy with the results from the 152 TMB.

Clear Skies for 2010 then we can all enjoy some more of your work.

John.

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RobH

RobH

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Thanks John, yes, the TMB is a really lovely scope :)

I do miss aperture a little though, and like the look of the Astrotech 10 inch Ritchey Chretien

My mount could handle the pair of them easily :hello2:

Cheers

Rob

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glowjet

glowjet

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I like the look of Astro-tech gear and have one of their diagonals with which I am well pleased. The carbon fibered 1/12wave 250 mm Astrograph should give outstanding results, but won`t you be losing that other arm and leg?.

All the best for the New Year,

John.

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