M17 Swan Nebula in LRGBHa

[DavidNg]

Hi, my first time in this "experienced" area; however I am still quite new to this hobby, particularly image processing. Comment/suggestion/advice are welcome and grateful.

Here is the Swan taken over several nights of late July in Sydney. Altogether about 6 hours of LRGB and Ha. I found LRGB alone is really lack of detail; adding Ha in is a real challenge and headache for processing, background and star colours are odd.

6" refractor at F/5.3, guided with a small guidescope, acquisition was mostly done by CCDAutopilot through Maxlm, processed with PixIninsight and Photoshop.

Thanks for looking.
David
Link to 22Mb high-resolution: http://www.astrobin.com/full/50390/?mod=none

below is 8% image size

[jase]

Just beginning and you're already using CCDAP...ay caramba!

A great start indeed.

Pixel math is your friend. Once you've got your masters created. Use Pixel Math in MaximDL (or tool of your choice) to add Ha data to your red filtered data. I usually work with 80% to 100% Ha to R blend. With your Ha+R master complete. Do a Ha+R,G,B combine. This will get you a base [HA+R]GB to work with. You can then perform luminance layering in photoshop of both Ha and Luminance data bring in the detail. Make use of the vibrance mode in photoshop, its usually more effect than saturate but you'll need to experiment to see what works with the data set. You may only be able to add 50% of the Ha data to the base RGB. Flatten and saturate, then layer the luminance data again but at a higher percentage. Keep your stars looking flat during the stretch process. Flat in that they don't saturate or reach the white (255,255,255) values. If this happens you'll have a hard time bring in the colour in the next step.

To get your stars back, do a G2V balanced base RGB combine. Stretch slightly (with DDP is perfect as it manages stellar profiles exceptionally well). Bring the layer into photoshop, place at the top of the layer stack as lighten or screen mode. Screen mode can be rather abrupt so you may need to mask the effect to ensure it doesn't alter other parts of the image. A mask is easily achieved with the colour range selection tool and tuning the fuzziness. If you want to make the stars pop, duplicate the mode doubles the effect. This can be effective if you layer a softlight mode over screen mode. softlight is a darkening function thus gets colours back if not already heavily saturated. Again, you may need to use masks to target areas of interest.

The above is just a starting point. Many ways to handle Ha data in RGB.

[Ross G]

Hi David,

Nice photo, it has great detail and sharpness.

You have the equipment and software to produce some amazing photos.
Where do you image from in Sydney?

Looking forward to more photos from you.

Good luck.

Ross.

[alocky]

Some great potential in that data.
Pixinsight has a script for combining ha and lrgb that works very well and is very easy to implement, and since you're already using the software, give it a go.
Cheers
Andrew.

[DavidNg]

Thanks Jase and Andrew.

When added into RGB with LRGB Process, Ha data made the final image appeared salmon color. I am learning PixMath as Jase suggested, see how I go.

Regards

[alocky]

If you have a look in the scripts menu, not the process list, there is a dedicated script for combining ha and lrgb. First you'll need to have done the lrgb process with those channels - have a look through the tutorials on the pixinsight website - the process is quite lengthy!
Here's a lagoon I did using the default parameters with the script.
www.astrobin.com/44973/B/
Cheers
Andrew.

[DavidNg]

Great image Andrew, love the bright red Lagoon color. I still cannot find the Ha lrgb script in Script menu, unless it is called differently. I have been looking through the PixInsight website, took me hours to follow through each example :sadeyes:,

Regards
David

[alocky]

I'm at work, but as soon as I get home ill take a screen grab of pixinsight with the script highlighted - if you PM your email address ill send it there.
Cheers
Andrew

[jase]

PI comes with a script titled HaRVB which services the purpose. There are other scripts in the forums as noted below;
http://pixinsight.com/forum/index.php?topic=3446.0
http://pixinsight.com/forum/index.php?topic=3446.msg35332#msg35 332
You must be logged in to obtain the file. Place it in your PixInsight/src/scripts/ directory.

These scripts aren't doing anything magical. When you look under the bonnet, they are still doing pixel math routines to add the Ha data to the Red filtered data. The script simply streamlines the process. The downside to the scripts is you don't have infinite control on the blend i.e. if you only want to blend 80% Ha into the red channel and 10% into the blue channel, you still need to do this manually. Also if you need to change the RGB weights to bring back colour balance this needs to be tweaked manually. There are no free lunches but I wish there were. :)

[alocky]

The AIP version of the script in the current PI release is 580 odd lines of code! It does let you vary the amount of mix, and has some denoising control as well.
cheers,
Andrew

[gregbradley]

You are off to a flying start. A fantastic first posted image.

What scope was used?

Greg.

[DavidNg]

Thanks Jase and Andrew, I will go through the script and update you my progress. Never knew interested in astronomy will lead me one day learning PixelMath.:sadeyes:



Thanks Greg, scope is AP 155 f7, as per your advice I have ordered and installed an AP 155TCC with a custom adapter from Preciseparts, it is now f5.3. Images look reasonable sharp to me, however I wouldn't be able to tell if my focal length is within the 80.8 +/- 1 mm range. Very pleases with the set up and results.
Regards