Astrophotography Processing Challenge May 2024

[TSS TEAM]

Welcome to the TSS Astrophotography Processing Challenge for May 2024.

This months data is SH2-132 The Lion Nebula in Cepheus and has been submitted by Carole @carastro.

Carole says:

The Lion Nebula in Cepheus Sh2-132

I live in a heavy light polluted location Bortle 8 and can only really do Narrowband from Home.

I also use a dual rig in order to get double the data per night. The fields of view do not match, but putting them through Registar I can match the data, and combine them in photoshop and simply trim the edges. In addition I tend to bin x 2 Oiii and Sii, so again these need to be upsized to match the Ha.

I have done all this for you, but you might find you need to trim the edge/s.
I can only use Tiffs as I use Photoshop, I hope you will all be able to cope with Tiffs.

I also did an SHO combi for those of you who just want to do OSC processing, though I think you would get more out of it if the individual Channels were processed separately.

I attach a link to my own process of this target.
https://www.astrobin.com/full/r5ipag/F/

I have only acquired StarExterimator in the last week or so, so I had no such tool when I did this processing.
This is my second attempt at this target.
This was taken in my back garden in SE London UK.
Total imaging time is 8 hours 20 mins

I hope you enjoy this interesting target and I look forward to seeing the various results.

Carole

Here's the link to Carole's excellent data:

https://drive.google.com/drive/folders/ ... sp=sharing

Feel free to download and process in any style you like. Then post up your final image with a description of your processing method for discussion.

And if you have some data you would like to contribute to a future Processing Challenge please contact any of the Moderators or send in an email to:

tssapchallenge@theskysearchers.com

[carastro]

I will be away at Astro camp in Bortle 4 from Monday 6th - 11th, (though the forecast is not promising). So depending on 4G (there is no Wifi at camp), I will try to login to this thread in case there are any questions.

Carole

[BigKahuna]

Carole, Thank you for the excellent data! I tried the SHO version because I have only been processing in OSC to this point. I "may" try it again during the month in separate HA,Oiii, and Sii channels but I'm pretty happy with this version. (not as good as yours)

Processed in Pixinsight.
STF
Gradient Correction (I tried Graxpert 1st but it took away part of the Nebula)
Image Solver
SPCC
BlurXterminator
NoiseXterminator
SCNR
Histogram Transformation
StarXterminator
CurvesTransformation of the Starless Image
CurvesTransformation of the Stars image
PixelMath to bring both back together
ACDNR for final image

[carastro]

Glad you enjoyed processing it. That's a pretty good result for precombined SHO. IMO I think you will find you can get a lot more out of the separate channels by processing them separately.

Also if you are not experienced in Narrowband data you probably found that you needed to change the colours as the Ha is almost always overpowering in NB images, so combining as SHO the result is likely to be green. You did a good job with the colour.
I did this in Photoshop in selective colour. Ramping down the green as a first thing to do.

I look forward to seeing you next version as a non pre-combined image.

Thanks
Carole

[Jockinireland]

Thanks for sharing the data Carol.

I had some problems early in the process. The Ha would not open in Pixinsight. I could open it in photoshop and some other programs but could not save it in a way that it would the open in PI. So I just went with the precombined image. My first step is always to do GraXpert to remove gradients, but this was totally destroying the image, turning it blotched and horrible. After extracting the channels I found that it was the blue/Oii channel causing the problem and I did Graxpert on the Ha and Sii and did Automatic background Extraction (ABE) on the Oiii which worked fine. I then recombined as SHO

From there this was my work flow;

For anyone not sure of PI the following explanation:
3. Script is a platesoleve needed before SPCC colour calibration set up for carlol camera and filters.
6. Pixelmath is a unlinked HT stretch by Bill Blanshan
7-9 is removing magenta stars
16 MLT sharpens
17&18 LHE increases contrast.

I then took it to Photoshop where I balanced and set the background and did a light selective high-pass routine to pick out some structure.

Back to pixinsight to reduce the green a little more (I do like some green in my SHO and am not afan of "Hubble Pallete" images with all green removed - the original hubble images had lots of green!) Replaced the stars and did a light star reduction. All leading to this;

This was nice data and fun to process.

[Graeme1858]

I had some problems early in the process. The Ha would not open in Pixinsight.

Hello David

I have now uploaded some save as .xisf files.

Can you do me a favour and see if you can open them without any problems please.

https://drive.google.com/drive/folders/ ... sp=sharing

Graeme

[BigKahuna]

Yes, GraXpert (in Pixinsight) did NOT like this image for some reason. I used Gradient Correction for the 1st time and it did good.

[AstroBee]

@Graeme1858 The OIII.xisf file will not download for me.

EDIT: Nevermind - Did not see the popup asking for permission. It has downloaded fine.

[Jockinireland]

I had some problems early in the process. The Ha would not open in Pixinsight.

Hello David

I have now uploaded some save as .xisf files.

Can you do me a favour and see if you can open them without any problems please.

https://drive.google.com/drive/folders/ ... sp=sharing

Graeme

Hi Graeme,

I downloaded the 3 .xisf files and indeed they opened fine in pixinsight.

Graxpert still chews up the Oiii though.

Rgds

David

[Graeme1858]

Here's mine. I opened the Ha Sii and Oiii in Pixinsight and did the following:

EZ Noise reduction on each one
EZ Soft Stretch on each one
RGB Combination - mapped as SHO (yeah, I don't mind the green either!) I tried HOS and OSH too but preferred the SHO
Starnet2
On Starmask
Invert - SCNR - Invert
Curves - S Curve for contrast - pulled down to reduce stars - increase red - increase saturation
On background
Curves - S Curve for contrast - pulled up to increase brightness - decrease green - increase blue - increase saturation
Pixel Math to re-combine
Unsharp mask
Save as a .png
Opened in IrfanView reduced to 1920x1080 - saved as a 3Mb .jpg (click for full res.)

It's a lovely image Carole, thanks for submitting.

See you tomorrow in darkest East Sussex!

Graeme

[carastro]

@Jockinireland
Sorry it appears that I did not respond to your image. I did try from camp on my smartphone and wrote a long reply, but every time I tried to post, the system kept asking me to login in even though I was already logged in and I lost the post that I had typed. So decided to wait until I got home.

I really like your process, and now can;t remember all the things I was trying to say - sorry.

Seems people have had problems with the files.

Carole

[carastro]

Nice rsult Graham, but not so keen on the green. Each to his own though.

Carole

[Graeme1858]

..... but not so keen on the green.

Yeah, I don't mind some green but now I look again, I might have over done it a bit!

Think I'll have another go and tweak the blue up and the green down.

Graeme

[Rasalgethi]

This is my process of the Lion Nebula.

I used Pixinsight. I did ABE on each file then used LRGB Combine with no L and HSO to RGB. Then Starnet to do curves on the background and the stars separately and then pixelmath to put them together again.

How do you people get the colours so bright?

[Graeme1858]

How do you people get the colours so bright?

Nothing wrong with dark and moody! The image you posted looks a lot better if you click on it to display a larger version.

I usually do a last stage tweak with curves to get the final image looking as I like it.

Your HSO palette choice has produced a nice magenta prominent image. Those that don't like green will approve!

Graeme

[AstroBee]

My attempt.

Dynamic Crop, Linear Fit to Ha, BlurX on each channel, SHO combine,
Narrowband Normalization - SCNR 0.144, O3 Boost 1.8, S2 Boost 1.8
Histogram Stretch, NoiseX,
StarX to remove stars, generated stars only version
Color Saturation to the Nebula only image
Screen Stars back to Nebula

[AstroBee]

Curious what focal length this was shot with? I don't recognize the Lion Nebula at all but maybe this is just a tight region of it?

[carastro]

@Rasalgethi
than you for processing my data. I presume you processed it as a OSC image. I think it has come out very well, well done. I wonder how you re-combined them after treating each file separately as this looks more like a Hydrogen in the red channel version to me. Nevertheless a very fine process.

[carastro]

@AstroBee
Another fine rocess, looks like traditional SHO.

I am a little at a disadvantage commenting on these proecsses as I don't use Pixinsight, I only process in Photoshop, so I have no idea about any of the processes you guys are doing but I hope you enjoyed the process and thank you for doing it

Carole

[Jockinireland]

Curious what focal length this was shot with? I don't recognize the Lion Nebula at all but maybe this is just a tight region of it?

Hi @AstroBee

If i remember right, carole is using a dual rig with two different FL's but hr final image comes out about 425mm. Heres a copy of my lion at 275mm with a crop area showing very roughly whats in Caroles image.