There are two versions. This one was done using the Hubble pallette,
which assigns (or "maps" in current parlance) SII to red, HA to green,
and OIII to blue. This mapping is necessary because the light emitted
by SII and OIII is not visible to the human eye, so assigning these
invisible wavelengths to visible wavelengths lets one "see" where SII
and OIII are present in the image.

The second version is at http://www.pbase.com/image/81778281

In both versions HA consists of 180 minutes of exposure with 10 minute
sub-exposures. SII and OIII each consist of 120 minutes in 10 minute subs.
Total exposure time for the image was 7 hours
All imaging done on bright, near full moon evenings.

I reprocessed this image in a more methodical manner.
You can view the result, which I much prefer, at http://www.pbase.com/image/82060459