But then again, how many different objects is a hydrogen beta filter useful for viewing? Not many, but these still seem to sell.
The market is limited to people trying to see the moons of Mars, Saturn, Uranus and Neptune and to attempts at seeing Sirius B, Procyon B and other doubles of similar ilk.
Over 20 nebulae respond to the H-Beta filter:
. . . . . . . . . USEFUL TARGETS FOR THE H-BETA FILTER . . . . . . . . .
While the H-Beta is probably one of the less-used nebula filters, the commonly expressed idea that it works only on a handful of objects is not necessarily true. Here is a list of some of the more prominent objects that the H-Beta may be at least somewhat useful on. Some may require larger apertures (and some may be slightly better in other filters), but a few have been seen from a dark sky site by just holding the filter up to the unaided eye and looking at the sky. Some of these will also be helped by a narrow-band filter like the Lumicon UHC.
1. IC 434 (HORSEHEAD NEBULA)
2. NGC 1499 (CALIFORNIA NEBULA, naked eye and RFT)
3. M43 (part of the Great Orion Nebula)
4. IC 5146 (COCOON NEBULA in Cygnus)
5. M20 (TRIFID NEBULA, main section)
6. NGC 2327 (diffuse nebula in Monoceros)
7. IC 405 (the FLAMING STAR NEBULA in Auriga)
8. IC 417 (diffuse Nebula in Auriga)
9. IC 1283 (diffuse Nebula in Sagittarius)
10. IC 1318 GAMMA CYGNI NEBULA (diffuse nebula in Cygnus)
11. IC 2177: (Diffuse Nebula, Monoceros)
12. IC 5076 (diffuse nebula, Cygnus)
13. PK64+5.1 "CAMPBELL'S HYDROGEN STAR" Cygnus (PNG 64.7+5.0)
14. Sh2-157a (small round nebula inside larger Sh2-157, Cassiopeia)
15. Sh2-235 (diffuse nebula in Auriga).
16. Sh2-276 "BARNARD'S LOOP" (diffuse nebula in Orion, naked eye)
17. IC 2162 (diffuse nebula in northern Orion)
18 Sh2-254 (diffuse nebula in northern Orion near IC 2162)
19. Sh2-256-7 (diffuse nebula in northern Orion near IC 2162)
20. vdB93 (Gum-1) (diffuse nebula in Monoceros near IC 2177)
21. Lambda Orionis nebular complex (very large, naked-eye)
22. Sh2-273 "Cone" Nebula portion around cluster NGC 2264
In addition, a number of the brighter nebulae like NGC 7000 or M42 will respond to H-Beta use for revealing certain specific detail, although other filters may provide a somewhat better view overall.
Clear skies to you.