Issue with Pixinsight RGB combination

[brisen (Brian)]

Hi All

I have started learning to use Pixinsight by working through some of the tutorials online and have followed the workflow process to Star Align the images - each filter done separately. This is my first serious attempt at astrophotography and processing the data.

I have then used the Image Integration process with Drizzle as per the instructions in the tutorial I was using, I then did a Drizzle Integration to integrate the lights for each of the filters, ending up with one integrated file for each of LRGB.

Following the instructions in the tutorial I have attempted to combine the RGB using Channel Combination to combine the RGB. This is where I run into a problem. Whilst the stars are all aligned in the individually integrated lights, when I combine the RGB I end up with them out of alignment. From looking at the combined file it is obvious to me that the Red is an issue and possibly the Green but it might be the Blue. I have attached an example and the individual integrated RGB as an example.

It is supposed to be the Orion Nebula and obviously needs some more work but I cant seem to get the stars aligned when I combine the RGB. I haven't added the Luminence yet as I haven't quite got that far in the processing.

Any suggestions on what I may have done wrong or missed doing would be appreciated.

Brian

[Atmos (Colin)]

When doing the alignment process you can do all of them at once. If you load all of your M42 images into the Image Registration and then do them at all at once it should fix your problem.

What it looks like you have done is registered all of the red with a red frame, all of the green with a green ect... Instead you just do them all at once from a single frame.

[brisen (Brian)]

Thanks Colin. Yes, I did do them as red to red, green to green etc. I will do them all in one go and see what I get.

Brian

[Slawomir (Suavi)]

Hi Brian,

As Colin suggested, you can register all at once, or register the channels separately as you did, but the you definitely need to star align the masters for red, green, blue and Lum, using Lum as a reference for example. Let us know if that fixes your problem.

[RickS (Rick)]

Adding to what Colin and Suavi said, you should pick a single sub as the reference and align all your other subs to it. It doesn't matter whether you do the alignment all at once or in smaller batches so long as you only align to that single reference frame.

You will get best results if you pick the reference carefully and use a good quality sub. Look for a sub with tight, round stars and no obvious guiding problems. The SubframeSelector script in PI can show you a plot of metrics such as FWHM and Eccentricity to help make this choice. It's also worth using the Blink process to check your subs visually.

Cheers,
Rick.

[brisen (Brian)]

Hi All

Thanks. I haven't got back to this for the last few days, but will work through the processing again to get the practice.

I found some tutorials by Kayron Mercieca at www.lightvortexastronomy.com and these are really easy to follow as he steps through the workflow in simple, easy to follow terms.

Brian