The Crescent and the Soap Bubble
timc
Attached is an image of the Crescent Nebula in Cygnus. The name derives from its appearance in the first images taken of it which appeared like a crescent Moon. This nebula is an expanding shell of hydrogen gas measuring approximately 16 x 25 light years across and it is illuminated by a brilliant Wolf-Rayet star at its centre.
The data for this image comes from imaging sessions in 2021 and whilst I’d imaged this nebula a few times before, this time I wanted to capture the very faint Soap Bubble Nebula: a planetary nebula with a spherical shape near the Crescent. This was only discovered in 2007/2008 and is very challenging to image. It can be seen as a faint red sphere at 8 o’clock from the Crescent. I used a combination of broadband RGB and narrowband Ha and OIII filters to produce a bi-colour narrowband image, as the nebula is rich in these two wavelengths (but not in SII). I imaged this target from my back garden observatory in Oxted on 9 nights between 24 Sept and 3 Nov 2021. The image consists of the following sub-exposures: Ha and OIII 600s x 35 each; R 34x300s and G, B 31x300s giving a total exposure time of 19 hours 40mins. I used a Takahashi FSQ85 ED (3.5 inch) refractor with focal reducer operating at f/3.9 mounted on a Paramount MX using a QSI 690 CCD camera and SX Lodestar 2 guide camera. Image capture was done with Maxim DL, flats and dark subtraction, stacking with CCD Stack2 and further image processing using Photoshop CS5 and Topaz AI denoise. Thanks for looking.
Tim C
drja...@aol.com
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Tim Coskun
Sent: Friday, 24 July 2026 08:59:31
To: croydo...@googlegroups.com <croydo...@googlegroups.com>
Subject: Re: [croydonastro - 8275] The Crescent and the Soap Bubble
William Bottaci
We appreciate you preserving to obtain this excellent image of a challenging object. Nice colours and contrast, just what we can't see by naked eye alone. I'm particularly impressed by just how small the fainter stars are, even to the corners; did you process the stars differently? Also what focusing aid if any do you use?
Do you have an estimate for the size of the image field please?
Not only is this a recently discovered object, but it was by an amateur using only a 6¼-inch refractor. We've come a way in 20 years, which makes the discovery all the more impressive - we amateurs can still wave our flag.
Thank you for sharing.
William
On Fri, 24 Jul 2026 at 12:17, Tim Coskun <tcos...@gmail.com> wrote:
Thanks very much for your kind comments James - much appreciated. I think at 19+ hours this is the longest imaging time I have spent on a target! However the soap bubble is very faint so definitely needed it. Also processing it was a challenge and took 4 attempts until I was happy with it. Pleased with the results though.
Best
Tim C
Hi Tim
That is an amazing image overall with the Crescent itself, and in capturing what is an elusive object, to say the least if it was discovered only so recently. The sort of image that would normally be the preserve of huge professional research telescopes. And there you go with just 85mm!
Well done persevering over 9 nights and coming back to processing it so well.
James