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This summer's project. 23 hours of the Crescent Nebula with emphasis on the OIII

RobH

By RobH
in Imaging - Deep Sky

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RobH

RobH

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NGC 6888, the Crescent nebula, very near to Sadr in Cygnus is thought to have started formation about 250,000 years ago.
The central star is very massive, and has a solar wind so strong it has blown off roughly the same mass as the sun every 10,000 years.
This wind has collided with gas that had been shed by the star in a series of shells in the past, and the wind has heated it and caused to glow.

At a distance of about 4700 light years, the light that those of us who’ve imaged or viewed this have just received left at a time that saw the start of the bronze age, the beginning of writing and the spread of agriculture.
World population was between 7 and 14 million.
Not long ago in the big scheme of things :grin:

In this image I’ve set out to get as much depth in the OIII as I could, rather than concentrating on the Ha as the dominant filter. The OIII in this target is often treated as a kind of second cousin, but it’s really interesting, and very different in structure from the Ha.

Imaged in June and July 2014 from Weymouth, Dorset.

Telescope.   12 inch Ritchey Chretien @ F5.3

Camera. Atik 460 EXM, Baader filters

Ha.   16 x 30 minutes

OIII.  16 X 45 minutes

RGB. 11 x 5 minutes for each filter

All subs binned 2x2

Ha-red, OIII-green and blue

RGB stars added as individual 'lighten' layers to each mono sub master

Captured, calibrated and stacked in Maxim and processed in PS CS6.

gallery_1757_60_182998.jpg

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RobH

RobH

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Thanks Olly :-). I've been meaning to go deep on the OIII with this for a few years, but decided to finally get on with it this year. These days I'm aiming at only a few images a year, but done in depth. Interestingly, with such strong data, processing was dead easy. There's just a basic stretch in fits liberator, and a very gentle stretch in Photoshop using curves, and that's it.

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RobH

RobH

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Thanks for the kind words folks :-). I'm rather busy for the next few days but will take your advice and have a crack at APOD.....it's got diffraction spikes so might be in with a chance ;-).

Lee, I already have a lot of data ready to process for M76 ( the little dumbbell) so that will be next, plus a shed load of data taken over the last two years of NGC 3718 and friends to put together.

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RobH

RobH

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Paul, I use an astrophysics APCCD67 reducer, which reduces but has no flattening effect. The scope is a native F8, and the 0.67x reducer takes it down to F5.3. Together with binning 2x2, which gives a resolution of 1.14 arc secs per pixel with the Atik camera, it gives me a very fast system.

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RobH

RobH

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Cheers all.

Mick....putting these images into a human context is quite important I think, otherwise, to folk who aren't into astronomy as such, they are just pretty pictures. When you explain just what they are, how big that are , and how far away, it gives a real sense of perspective, which is something the human race as a whole is sorely in need of I think :-)

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