Open and process all 4 groups of subs in Maxim do any stretching or tweaks that you would normally do in Maxim.

Save them as mono Fits files

Open all four processed images in Maxim

Once all four are open choose PROCESS > ALIGN

You are then presented with the choose file pop-up. Add all four files

Using auto-star matching > overlay all images this will generate a combined image (this just helps to check things are ok) then click OK.

You should now be back to 4 images, then SAVE ALL

Now you can close Maxim and open Photoshop.

Open ONLY the R G B images into Photoshop using FITS Liberator

You can tweak each image until you are satisfied but do not change the image type.

Once you are happy with your images go to the CHANNELS panel, click on the little arrow top right and you are presented with the following menu.

If MERGE CHANNELS is grayed out then go to each image and LAYERS > FLATTEN IMAGE.

Once all three images are flattened the MERGE CHANNELS should be selectable.

Choose 3 channels, and then select in order your images R then G then B

Each channel is then ALPHA and if you turn them all on this is what you get.

DONT PANIC, this is normal.

Now convert the image to RGB

PHEW, that is better!

Now, once tweaked to your taste open the Luminance image, then SELECT > ALL

Then COPY

Select your RGB image and PASTE

Where has all my colour gone??  again.... DONT PANIC!

Now in the Layer properties choose LUMINOSITY

And your colour SHOULD come back

You can turn the LUMI. layer on and off to see the difference before and after.

Any further processing is now down to you.

GOOD LUCK!!