I used Photoshop.
Open the 120mc file, you will have an RGB file with three R, G and B channels and an RGB channel in the channel window.
Open the 120mm file, copy it on clipboard, close it. Now you are back in the 120mc file channel window. Add a new channel, name it L or something.
Paste the 120mm file in the L channel. Manually align the stars with the RGB channels.
Now you have a 5 channel file, channels RGB, R, G, B and L.
There might be other ways to do it.