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Why does no one sell occulting bars?

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#26 David Knisely

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Posted 24 September 2012 - 12:12 AM


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.

But then again, how many different objects is a hydrogen beta filter useful for viewing? Not many, but these still seem to sell.


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.

#27 csrlice12

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Posted 24 September 2012 - 07:22 AM

On the other hand, these are expensive eyepieces, just put the toothpicks/matches where it holds your eyelids open. Solves two problems, the occulting problem, and now you'll stay awake to see it!

#28 Svezda

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Posted 24 September 2012 - 07:44 PM

For a few years I've had a project which is a few pages down (= low priority) on the 'Astronomy To-Do List' to find low-quality, cheap 2" and a 1.25" filters, take out the glass, attach a blackened thin metal strip that can be bent and positioned repeatedly as needed to be in focus for the rare times I'd want to use an occulting bar.

#29 Scott in NC

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Posted 24 September 2012 - 08:36 PM

Thx for the info, Don!

#30 Pollux556

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Posted 24 September 2012 - 08:43 PM

Yes,
Kellner, RKE, Plossl, Abbe Orthoscopic, monocentric, etc.


Don,

I guess that it would be better to paint the stick in flat black. :question:

#31 Starman1

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Posted 25 September 2012 - 11:07 AM

At least the sides shouldn't reflect light. The top and bottom can be any color, as the bar will block light.


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