They work pretty well, Ed. I have both an Orion SkyGlow and UltraBlock
filter for my SCT (probably bought 'em both 10+ years ago), and also use a
Lumicon UHC (my favorite!) and O-III. They all have their uses.
If it were a choice of either a broad-passband or narrow-passband filter,
I'd skip the broad- and go with the narrow-passband filter. From my
*severely* light-polluted backyard in San Jose, the SkyGlow really doesn't
do much, although I still use it pretty regularly at Coe for general
non-galaxy stuff. The added contrast can certainly be helpful at times.
I've also found the SkyGlow was nice for enhancing views of Jupiter and
Saturn. Sort of a side benefit, I guess. :)
Although my 1.25" Lumicon UHC filter remains my favorite filter by far, I
generally use the UltraBlock when I'm working with a 2" eyepiece, or if I'm
regularly switching 1.25" eyepieces when studying planetaries or searching
for detail in selected emission stuff. When you need PN/emission contrast,
especially at low magnifications, these narrow-passband filters are great.
Selected items require I use an O-III to pick up, but these are relatively
few and far between.
Bottom line: I'd skip the broad-passband type and go with a narrow passband
filter. I think you'll get much more use from either an UltraBlock or a UHC
than you will from the SkyGlow. Just don't plan to use any of 'em when
hunting faint fuzzies. ;) Haven't done much in comparing the UltraBlock and
UHC filters in quite a while, but plan on doing so this coming weekend.
...Bob...