What is a mask?

[jimmyh1555]

I have been trying to learn all there is to know about AP, after my stunning (:lol:) image of Omega. I am doing the processing in Star Tools 1.4 and always suddenly come across this "mask". It tells me I either have not got enough pixels, or I have too many. Then the screen goes green and it tells me to "Invert" then "shrink" and then...wait for it..."Grow"! What is a mask supposed to do? Any simple explanations????:sadeyes:
Jimmy

[Lognic04]

Its kind of like painting, put tape over where you don't want paint, but the "tape" is the mask. The green is what is protected under the mask.

[ChrisV]

What Logan said. Have a look on the star tools forum. There's some really great tutorials that go through all of this stuff.