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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2659
Loc: Phoenix, AZ
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if the Lumicon UHC only lets through the OIII & H-beta lines, then is there any gain in owning an OIII, which cuts out the H-beta?
i am thinking if the object being viewed is say a planetary, and only emmiting OIII and no H-beta, would there be anything to gain with the OIII over the UHC?
thanks,
david
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MitchAlsup
super member
Reged: 08/31/09
Posts: 186
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Stars emit broad band light.
The OIII filter, all by itself, will dim the stars more than a UHC, so it might be easier to see the nebulae. The brightness of the nebulae, itself, will not be changed, just its contrast relative to the rest of the illumination in the FoV.
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2659
Loc: Phoenix, AZ
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but even with the stars in the fov of the nebula, the differance is only one line of spectral light.
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Tiny
super member
Reged: 05/02/08
Posts: 197
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OIII = darker background, higher contrast and more detail [provided the proper target]. Because it blocks out pretty much everything else [its not just the difference of 1nm in the light spectrum its 13nm] it also makes finding targets easier. This is what you're paying the money for.
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tatarjj
Pooh-Bah
Reged: 04/20/04
Posts: 1134
Loc: Austin, TX
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Well, planetary nebulae emit both H-beta and OIII, but so much more OIII than H-beta that you want to use an OIII on them in most cases. Sure it lets through less of the nebula's light, but the important part is that it vastly improves contrast.
Same with the H-beta. Some nebulae emit so much H-beta that you'll see them easier when you cut out their OIII light and vastly increase the contrast by only looking in H-beta.
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John T.
Austin, TX
25" f/4.2 Dob
18" Obsession #701
4" Stellar Vue Achromat
8X56 Binos
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srwolf
member
Reged: 12/22/04
Posts: 22
Loc: Edmonton, Alberta
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I like having both available. Viewing a nebula with first one then the other reveals different details. It's interesting to notice the differences.
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12.5" f/5 Portaball
8" f/6 Skywatcher Dob
Feathertouch Focuser 
Telrad x 2
Crappy Binoculars
3-6 zoom,5,9,16 naglers
24,35 panoptics
13mm Ethos
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Rob S
professor emeritus
Reged: 03/16/07
Posts: 502
Loc: NZ
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Yeah, I have both too (Astronomic brand).
Frequently use the darker OIII on the 24Pan and swap that EP out for my 20XW with the UHC fitted (as the exit pupil is smaller in that EP).
Eta Carinae looks amazing in both in the 13E of course. Well, it looks good anytime.
Rob.
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8" f5 Dob with Feathertouch
Brandon: 16
Pentax: 7, 10 & 20XW
TMB: 30 Paragon
TV: 8 & 13 Ethos;
5 & 13 NaglerT6;
24 Panoptic
Leica Trinovid 8x50 BN
Edited by Rob S (11/05/09 12:18 AM)
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cuzimthedad
Just Be Cuz
Reged: 04/09/06
Posts: 3725
Loc: Sonoma, Northern California
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I have both although my OIII filters are cheaper Celestron models but they perform admirably. My Lumicon UHC is a beast on Nebula and I love it.
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Dan
20" f/5 Obsession
Antares 1529
TV102
Various Naglers, Ethos, UO Orthos and TV Plossls
The Off Fisher Lane Irregulars
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Shawn H
Post Laureate
Reged: 05/16/07
Posts: 3012
Loc: Southern France 43°56'N-4°50'E
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David
IMHO these are THEE 2 filters worth having, though the UHC is the all nebulae specialist & the OIII the planetary nebulae specialist! I found that each works better on different objects! And only after trying the 2 on each object can you decide! 
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18" David Lukehurst truss Dobson with Sky Commander flash 4 DSC's & Moonlite CR2 focuser & Astrocrumb filter slide
Orion xt10i fully flocked with Telrad on 4" risers & Feather Touch focuser & huge Boston Red Sox decal
The original Orion StarBlast & 15x70 Celestron Skymaster binos & Ethos & Naglers & Dobs oh my!
Orion Ultrablock narrowband filter & Astronomik OIII line filter
Tele Vue 2x Barlow & Antares 1.6x (2") Barlow
CATSEYE collimation tools, TeleGizmos Dob covers
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 8290
Loc: Beatrice, Nebraska
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If you want a rough idea of what filter to use on which object, you might want to look at the following article:
FILTER PERFORMANCE COMPARISONS FOR SOME COMMON NEBULAE
Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org
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