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PostPosted: Wed Jan 08, 2014 12:33 pm 
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I'm ashamed to say I've not captured a single night sky photon this winter, as I've found other distractions.

I did note the forecast for tomorrow night seems somewhat promising, and now I've got the ok from work to start later in the day that could give me more time. So I really want to have another go at the Rosette nebula. I haven't tried it for 2 years, and I do have a nicer lens since then to throw at it.

I have no idea where all my bits are so will have to dig that out again. Might take it easy. Just try unguided imaging, assuming my mount hasn't shifted with all the rain. Would limit to shorter exposures anyway.

In other news, I notice that Astronomik have now made a version of their clip filters for full frame Canon cameras. I'm wondering if the 5D2 would provide a tangible benefit over 450D/600D I'm using, but that will be more focal length dependant. They now seem to offer Hb filters, so I'm debating once again if that would provide an interesting alternative to using Ha filters (3x more effective detectors in a more sensitive region, vs lower original signal). Wonder if there is enough selectivity between OIII and Hb, will need to look that up again.

Bob, in the distant past I vaguely recall you were thinking of looking for deviations in the ratio of Ha to Hb, did you ever do that?

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Wed Jan 08, 2014 3:02 pm 
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Hi popo,

No, I never got around to it. It's probably worth a try but my, admittedly limited, experience with nitrogen, sulphur and oxygen narrowband imagery makes me suspect that to get a meaningful signal out of any variations in the ratios of Hα to Hβ would require a lot of exposure time.

I haven't done any astro-imaging since that NGC7822 shot. I keep meaning to but my conservatory, where I keep the astro kit, has been acting as storage space for stuff usually kept in my garage during building of an extension to said garage which has rather limited use of the conservatory since the autumn! And then there's been the weather... :roll:

I think my next project will be to return to the subs I took way back of the Andromeda galaxy. I've never published a version of that image using my "full-fat" colour workflow for the simple reason that I don't like the result. The actual colour of the core Population II region is really very orange, if I remember my preliminary looks from almost a year ago correctly, and quite frankly the aesthetics suffer as a result. But I think I should bite the bullet and recognise that the universe is the way it is and not necessarily the way I'd like it to be. A useful metaphor for life. :wink:

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Wed Jan 08, 2014 7:56 pm 
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You still have an advantage over me, in that I don't even know where most of my astro kit is at the moment!

Shifting my working later hasn't been the slam dunk I hoped it would be. Of course, where I gain in the morning I lose in the evening, so I'll have to remember to pre-cool the kit so I can run as soon as I get home.

During a look earlier today, the Ha:Hb ratio is even mentioned by Astronomik as a suggested use for their Hb filter:
"When using the Astronomik H-beta filter together with the H-alpha-CCD you can create charts of the ionization energy in nebulas by creating an image from the ratio of H-alpha vs. H-beta."

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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