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RobH

The Bubble Nebula, NGC 7635 (SH162/Caldwell 11)

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The Bubble Nebula, NGC 7635 (SH162/Caldwell 11)

Hello all.

It's been a while since my last image as I've been getting to know my new scope, and am very slow when it comes to processing anyway!

This is one of my favourite targets, and I imaged it back in 2008 with a 14 inch Meade so it was interesting to see how the new scope fared against that .....

Here's some information to put the image into context.

This 10 year diameter bubble is being blown out of the surrounding molecular cloud by the massive star SAO 20575 (BD+60 2522).

This is what's known as a Wolf-Rayet star, a young, massive and extremely hot star that’s burning its fuel rapidly and is approaching the supernova stage. It’s thought to be between 10 and 40 times as massive as the sun. It’s the bright star in the bubble, but isn’t at the centre of the bubble due to the different densities of the surrounding material.

The bubble is being produced by the solar wind from the star, estimated to be at a speed of 4 million kph. The UV radiation from the star is ionizing the gas causing it to glow at a temperature of about 10,000K, which, when you consider the size of the region, gives some idea of the tremendous energies involved.

A second, larger bubble can be seen in this image, the edge of which is next to the bright blue star in the lower right.

The nebula is 11,300 light years away near the constellation of Cassiopeia and was discovered in 1787 by Sir William Herschel.

I had a right battle processing this due to the fact that throughout the few weeks I was imaging it, I was adjusting collimation on the new scope, with varying degrees of success. Consequently, the stars were different shapes to some extent in the different colour channels, so there was a fair few hours of fixing involved :rolleyes::grin:

Telescope. 12 inch custom Ritchey Chretien @ F5.3

Camera. Atik 460EX using Baader filters

H-Alpha. 32 x 10 minutes

OIII. 18 X 10 minutes

RGB, all 3 minutes each, 12 red, 12 green & 25 blue.

All subs binned 2x2.

Imaged in January and February 2013 from Dorset, England.

The full sized image can be found on my website.

Cheers

Rob

gallery_1757_60_178915.jpg
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Holy Moses, that is astounding, Rob. It knocked be backwards. Exquisite and sort of - indecently huge! I take it you're pleased with the RC...

Yes, a winner.

Olly

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I don't think I've seen as much detail in the bubble before, it's a great image.

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Thanks guys :smiley:

I take it you're pleased with the RC...

Olly

As you know Olly, I've had a lot of work to do to get the RC working properly, but yes, I'm very pleased with it.

The next job is to deal with the dewing up issues, but I have a cunning plan!

BTW....all subs are binned 2x2

Cheers

Rob

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Fantastic! Absolutely fantastic.. Well worth the perseverance & time spent

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A stunning image. Well done.

James

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Thanks again all.

As I mentioned, I binned all subs 2x2 on this, which made for a very fast system that just seemed to suck down the photons, but was still giving 1.14 arc seconds per pixel of resolution, and from my location I doubt I could get better than that.

The Atik 460EX really is a joy to use :smiley:

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That's a bit of a corker, that is! I hadn't realised before that the bubble is actually a bit pear shaped! :)

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There is no need to be alarmed. The loud thud you may have heard was just my jaw striking the floor. What an absolutely stunning, stunning image.

(This new scope - you haven't by any chance got your hands on that large second-hand reflector that's been on FLO's site have you...?)

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Stunning detail & love the colour

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That is an absolute stunner Rob - as others have said the depth and detail is simply amazing. One of my absolute favourite objects too and that's the best image I've ever seen of it.

Congratulations and thanks for sharing.

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Thanks again folks.

A few notes on processing.

Stacking, calibration etc was done in Maxim

CCD Sharp was used for deconvolution

95% of the rest was Photoshop, but Pixinsight was used for backround gradient removal, a little noise reduction, and some sharpening (I'd use it for more but until someone comes up with a practical manual that's not full of stuff I can't understand, that's as far as I've got!)

In order to get the RGB stars in the NB image, I added broadband stars to the respective colour channels using the 'Lighten' blend mode (photoshop), so, Red stars were added to the Ha channel, Green to OIII, and Blue to the 30% HA/ 70% OIII mix that was used as the blue channel.

I used my Ha data as a luminance channel, but the problem with this in terms of star colour is that stars in Ha are small, so this leaves big, coloured, unpleasant looking artifacts around the stars. To deal with this, I made an RGB image from my original RGB data, the converted it to greyscale and added this to the Ha in lighten mode to give full sized stars in the luminance layer.

This method gives decent RGB stars in an otherwise narrowband image.

Everything else was layers, small adjustments here and there etc.....I had 5 different attempts at processing, and this is the final one, as once I think I've finished an image, I then try to find faults, and as I always find them (or Amanda does!), I then usually have to learn new approaches to fix them...sometimes a long process but always worthwhile :smiley:

Cheers

Rob

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Excellent work Rob, looking at it I woulnt have thought it was all binned as the stars have not suffered. Top drawer stuff this is.

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looking at it I woulnt have thought it was all binned as the stars have not suffered. Top drawer stuff this is.

I'm getting a resolution of 1.14 arc seconds per pixel with it binned 2x2 Rob, so am pretty well at the limit of my seeing. hence no issues with the stars etc.

Star only suffer when binned if the binning means your system resolution is not as great as required to image the stars properly, and in this case, my resolution is fine. Binning something like an 80mm scope when your camera has a chip with 7 micron or larger pixels will lose resolution however, as you're nowhere near the seeing limit (except on very bad nights!).

The 460 EX has 4.54 micron pixels, so binned 2x2, they're only 9.04 microns, and at a focal length of over 1.6 metres, this worls out fine, and makes for a long FL rig that's still very fast.

Cheers

Rob

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I'm getting a resolution of 1.14 arc seconds per pixel with it binned 2x2 Rob, so am pretty well at the limit of my seeing. hence no issues with the stars etc.

Star only suffer when binned if the binning means your system resolution is not as great as required to image the stars properly, and in this case, my resolution is fine. Binning something like an 80mm scope when your camera has a chip with 7 micron or larger pixels will lose resolution however, as you're nowhere near the seeing limit (except on very bad nights!).

The 460 EX has 4.54 micron pixels, so binned 2x2, they're only 9.04 microns, and at a focal length of over 1.6 metres, this worls out fine, and makes for a long FL rig that's still very fast.

Cheers

Rob

That really interesting, Rob, and the result speaks for itself.

I've been keeping my luminance subs at 1x1 with a similar focal length and now I'm wondering why!

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I've been waiting for this one and you didn't disappoint Rob, outstanding work with exquisite detail.....nice to see you binning 2x2 matching up the scope camera with your location, very often overlooked.....top job!

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Goodness me - that's gorgeous! :) Absolutely wonderful, fantastic colour and detail :) I think you were lucky to get down to nearly an arc second of seeing. I rarely get better than 2 or 3 though I did get around 1app a week or so ago but only had a short imaging time.

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I've been waiting for this one and you didn't disappoint Rob, outstanding work with exquisite detail.....nice to see you binning 2x2 matching up the scope camera with your location, very often overlooked.....top job!

Absolutely! :) I have it on my list too for when it comes into my field of view.

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That really interesting, Rob, and the result speaks for itself.

I've been keeping my luminance subs at 1x1 with a similar focal length and now I'm wondering why!

With your edge scope at F6.3, binning everything will work out great for you, and you'll be amazed at the speed of your system.

I've been shooting 30 minute narrowband subs on a recent target and the amount of data is quite frightening!

Gina, My seeing conditions will be similar to yours, 2 to 3 arc secs per pixel on a good night, but you need to oversample in order to get good star shapes, so should be looking for a system resolution of 1/4 to 1/2 of the seeing conditions, so I'm at around 1/3 with my rig, which is just right.

Cheers

Rob

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