well i think i just gave both filters a worst case scenario test, considering where the moon is right at the moment, i slewed to the lagoon neb and all i could see was the cluster, add the UHC-S and suprise, a bit of nebulosity pops into view with the cluster still there as before, put the O-III in and sure most of the cluster disappeared but who cares, your obviously looking to bring out nebulosity with one of these
i could make out some structure in the nebulosity that just wasnt there without filters. also using my hand as a mask with both filters didnt really change the view dramatically (half of my hand across the front of the OTA)
next victim was the tarantula neb, uhc-s same comments as everything else ive tried it on so far, enhances it nicely without being overkill on the fainter stars.
O-III was pretty dramatic, again brings out more structure in the nebula but dims everything else dramatically. from what ive seen so far the O-III would just be excellent in a large scope whereas the uhc-s is just a great all rounder, keeping the view natural while enhancing nebulosity.
final words on both:
UHC-S, doesnt matter how big or small your scope is id definately look at getting one of these if you havent got one already (i left the filter in while observing 47tuc and didnt notice till i went to change ep's)
O-III, from the structure this is allowing me to see in nebulosity that you just cant make out without a filter id say this would be an incredible filter on a large aperture, id probably recommend that you look through one before buying it (if you have a smaller scope) because it does dim stars down quite a bit, but i dont see that as a problem since it makes you concentrate on the nebula.
having said all that, id miss them both if something happened to them
hopefully this thread helps some others
Tj