Can anyone tell me how to combine a OSC broadband image and Extracted Ha and OIII from a dualband filter?

Maybe this can help

https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

Mario

Most of the information you need should be in the link that @snowman provided above. I thought I might help with getting the star colours right.

You need to start with two files, both created by the RGB combine tool. I will call these:

1. RGB-for-stars
2. RGBHOO (or whatever mix you prefer - maybe even just HOO)

The first will contain only broadband RGB data. You will probably want to run this through the calibrate star colours tool - that's up to you.

The second will contain the nebulosity and features that you want in your final image. Don't worry if the stars look bad in this one - it wont matter.

These files must be registered together. If they come of of the same integration they will already be registered. If you have produced them from separate integrations then just load them as lights (no calibration files), run the registration tool and select 'save registered frames'. From this point you will work with the registered files.

Now you will save the stretched versions of these files. Typically you would use a mild stretch for the RGB-for-stars file (to get the stars looking good) and a stronger stretch for the RGBHOO file (to get the nebulosity and features looking good).

Now you need a starless version of each of these files. I normally go out of APP at this point and use Starnet++ on each file. This works very well, but you might prefer to use the star removal tool in APP - but I've struggled with getting that to work well - probably my fault as @mabula-admin does excellent work.

Next, go to an image processor like Photoshop or Gimp. I use Gimp as its free and works well. Load the stretched RGB-for-stars and the RGB-for-stars-starless as layers in the same image and the set to layer blend mode to subtract or difference (whichever looks best to you). This will give you an image which contains only the stars, with the correct star colours. Merge down the layers and save the result as RGB-stars-only.

Now - still in Gimp (or whatever) load the stretched RGBHOO-starless and the RGB-stars-only as layers in a new image. Set the layer blend mode to addition, merge down the layers and save your final image. Of course you can still play around with blackpoint, saturation, etc at this point if you wish.

This is a process I use with most of my narrowband images. It might sound complicated, but once you have done it a couple of times its pretty straightforward.

regards

JC

Thanks so much John! ill give that a shot. I really appreciate your help!

Regards,

Jim-