Combining Ha with RGB

[astroimager69]

Hello
I image with a DSLR and have recently started using a Ha filter. I am new to calibrating and stacking with PI having previously used DSS

I have seen several tutorials about how to combine Ha with RGB. I would like to know why I can't just calibrate and stack them all together (Ha and RGB) using for example the batch processing script? Why do I need to process the RGB and Ha seperately and then later combine them?

Thanks

[pfile]

well one thing is that with any OSC, the green and blue channels in the Ha image will have very little signal. you dont want to get that mixed up with the real G and B data.

so basically you want to isolate the red channel from the Ha images and then use that to enhance the red of your RGB image.

rob

[astroimager69]

Thanks very much
Before combining the Ha and RGB I expect I need to make sure that all the individual RAW Ha and RAW RGB are aligned first.
In other words shall I align the RGB together with the Ha images first, then run the RGB and Ha seperatly through the BPP script and THEN combine them?  Thanks again

[pfile]

yes that is correct - you can actually run BPP twice if you want, just making sure to specify the same image as the reference image both times. i havent used BPP in a while but i think it would not matter that the reference image is not actually in the list of Ha files.

in fact you probably have to do it this way, because you need different flats for the Ha-filtered images. i dont think the script necessarily knows how to handle OSC images which are filtered.

rob

[astroimager69]

Thanks again Rob
I have tried to run the BPP on the Ha stack (i have 14 good lights). The script always gives me an error message (cannot stack less than 3 frames)
.

[pfile]

probably the registration of those images failed for one reason or another... check the calibrated lights.

rob

[astroimager69]

Thanks, i will try and take some other frames