SH2-132, the Lion Nebula

[RickS]

Another image from SRO in California. I have a backlog of data from last summer and autumn before the weather turned to crap like spring/summer in Brisbane :D

Sharpless 2-132 is an emission nebula on the border of Cepheus and Lacerta. It's not that bright and exciting but I did what I could with it. This is a roughly Hubble palette image. I didn't have any RGB data so I mangled the Hubble data to provide some vaguely pleasing star colours - better than white anyway.

Details are..

Scope: FSQ-106ED
Mount: Paramount ME
Camera: QSI683
Filters: Astrodon 5nm Ha, OII, SII
Guiding: QSI OAG + Lodestar
Image scale: 2.094 arcsec/pixel
Exposures: 27x1800s Ha, 12x1800s OIII, 19x1800s SII (17 hrs)
Processing: PixInsight 1.8

Hope you enjoy the image and I'm always interested in suggestions for improvement.

High res version on Astrobin (now with sparkly white stars): http://www.astrobin.com/full/170152/B/

Cheers,
Rick.

[Ross G]

Great looking photo Rick.

Amazing detail.

Ross.

[RobF]

Love the palette.
Love the pic! :) :thumbsup:

[dvj]

Hi Rick,

The color channels are great. But the stars look a little weird, compressed. Great object with lots of detail. Rarely do you see this in narrowband.

j

[multiweb]

Pretty cool, Rick. Never seen this one before. Looks like a messed up M17 on its side. Nice nebula. :thumbsup:

[RickS]

Thanks Ross & Rob.



Thanks, John. I did use an experimental technique to give the stars a little colour and they didn't turn out as well as I hoped. Might have to play around with that some more.



Thanks, Marc.

[gregbradley]

An interesting object. Nice colour work. The stars though have been badly damaged along the way and they grab your attention. It'd be better to have magenta stars.

I know of 2 ways of handling the magenta stars. The first does not always work and that is simply reducing magenta using the selective colour tool.
The other is selecting the stars and using the swap channels tool in Photoshop. Another would be to select the stars and then manipulate the colour (if you select accurately enough it does not affect the surrounding nebula too much but it does a bit).

No free lunches with stars in narrowband and as you point out its best to get colour data for the stars and blend in.

Greg.

[RickS]

Greg,

I used JPM's tone map process which I have adapted to PixInsight, so the stars were originally white. Maybe they would have been better left that way. I'll see if I can get the false colour thing to work better. If not I'll consider it a failed experiment and go back to white stars :)

Cheers,
Rick.

[gregbradley]

Perhaps a mask for the stars whilst the mapping process is done to protect them from changes. Or extract the stars as a layer and save that only then do the mapping then add the stars back in later when all the colour work is complete.

Greg.

[RickS]

That's pretty much what I did, Greg. The tone map process is based on star removal. The stars are added back as part of the luminance after all the colour work is done. I then did some further processing on the stars to attempt to add some colour which is probably what was responsible for mangling them.

Cheers,
Rick.

[strongmanmike]

Sorry Ricki, you know I love your work :love: but not a big fan of this one :sad:

The stars don't look natural and are all uniform and pale, the neb looks slightly posterised and the colours are a bit washed out and weird....hmmm? is that enough negative critique..? :face:

Having said all that encouraging prose, it has some great details and does look like an amazing area, with huuuge potential in a repro though :thumbsup:

Mike

[marc4darkskies]

Going to have to agree with Mike on this one Rick - sorry. The stars are insipid and they look like they've taken on the colour of the nebulosity. I would let the NB stars shine through in all their glory ... let them be magenta!!

[Leonardo70]

Really nice Rick, this is a difficult target, so faint !!!
If you need RGB for stars i have one rendition about in my web site, i found terrific to keep calm the stars.

All the best,
Leo

[RickS]

Thanks for the critique, Mike. Watch out for the repro...



No magenta, Marcus, but maybe I'll return them to the original white, or...



Thanks Leo for the kind comment. I might take you up on that offer of RGB stars!

Cheers,
Rick.

[RickS]

Here's a (mostly) starless version just for fun...

[RobF]

WOOooooh. Where is Fred when you need him? :lol:

[RickS]

Busy flying drones, I think :)

[RickS]

I have posted a new revision with the white stars that the tone mapping process produces instead of my previous attempt at fake star colour. Next time I'll make sure to get some RGB.

Leo: thanks for the kind offer of RGB stars but unfortunately your image doesn't cover one corner of my FOV, so I'd have to do an odd crop.

New version here: http://www.astrobin.com/full/170152/B/

Cheers,
Rick.

[strongmanmike]

Yes, the stars do look better now Rick :thumbsup:

Mike

[RickS]

Thanks, Mike. I'm guessing you're still not a huge fan. That's cool... I don't think I am either :) I haven't seen an image of this object that I think is really great. There are some areas that I think would look good at longer focal length.

Cheers,
Rick.

[Amaranthus]

Out of interest, did you get much contribution from the SII channel in this one, Rick? I was surprised by the amount of blue!

[RickS]

Barry,

Estimated SNR weightings for the integrated masters were 97.4 (Ha), 17.9 (Oiii) and 44.4 (Sii.) So, there was a fair amount of Sii and not so much Oiii.

Just for giggles I worked out that per pixel I was detecting 0.63 photons/sec in Ha, 0.13 p/s in Oiii and 0.35 p/s in Sii in one of the brighter blue areas. It is definitely a dim nebula.

Cheers,
Rick.