Liz, which UHC did you use? Lumicon? Not all are the same for H-Alpha.
Lumicon cuts out all H-Alpha I think (see
http://astrosurf.com/buil/filters/cu...#Lumicon%20UHC)
Baader UHC-S and Astronomik UHC filters will let that fairly important line through nicely. Our eyes are not very sensitive there but 50% of a strong signal is better than none at all. Our eyes love OIII and H-Beta but the H-Beta in these things is generally way way down from H-Alpha. H-Beta is of course our good old horsehead or California nebula specialized filter.
Something I notice is that use of an Omega NPB filter helps nebula that have a fairly strong H-Alpha component (like Veil, North American Nebula, and Dumbell Nebula). Our eyes falloff on red but since the nebula is strong in H-Alpha you get just a bit more. The Lumicon UTC allows only a little H-Alpha but not a lot like the NPB filter or Baader and Astronomik UHC filters. NPB is the one I switch back to from time to time against the OIII because sometimes it really helps bring things out a bit more. Not all UHC are created equal.
The Astronomik UHC and Baader UHC-S filters will allow H-Alpha as well as Nitrogen II come through so that one may be nice as well (cannot comment, have only seen it's specs). M27 is strong in Nitrogen 2. Astronomik UHC is not a narrow band around the H-Alpha like the NPB or Baader so the deeper red components of background glow may cut contrast a little more than NPB. Again, only pure chart reading and really deep reds our own eyes cut out anyway.
Would be nice to have the bucks to buy them all ... but that is another thread on IceInSpace
so many filters ... so little cash.