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 Post subject: Sanity check please...
PostPosted: Sat Oct 30, 2010 10:50 am 
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Joined: Sun May 25, 2008 12:48 pm
Posts: 8032
Location: UK
...I just want to make sure I don't have any signs of sanity!

While much of what I'm about to write has been said already, I'll recap so I hope everything is here.

My goal: take nice looking night sky photos, emphasis on deep sky/wider angle stuff using normal lenses.

Main kit: Astrotrac TT320X-AG to do the tracking. 450D and 7D with cable release. Astronomik CLS EOS clip filter. Assorted lenses.

To do: 450D converted for astro use (~2 stops benefit at H-alpha).

My biggest problem: light pollution

The CLS filter seems quite effective at removing sodium and mercury lighting pollution, but I suspect there are a lot of other broad band light sources which it wont really help with. I'm debating if their UHC filter will help, since that is narrower passband.

The issue here is what subjects am I going for? The CLS and UHC filters primarily pass emission nebula spectral lines, so will provide the greatest benefit there. Someone linked to an article claiming there wasn't any benefit for broad light source subjects, but I think they will although to a much lesser degree. While it will cut out significant parts of broad band sources, it will still cut out proportionately more of the narrowband interference.

Further thought, is there a benefit to stacking filters here? Logically I think the answer is yes... now I can only fit one in the body, but I can get a lens front one too in addition, although I am a bit concerned about filter reflection effects here.

Taking that to an extreme, should I even consider doing narrowband capture? On that note, is there a simple list somewhere saying what objects emit what stuff? Obviously if I go this route I think it would very much force me to focus on emission nebulae. That's ok, as they're the more easily pretty objects out there.

So on filters, the questions are:
1, would switching from existing CLS to UHC be much benefit?
2, would stacking a UHC with existing CLS provide even more benefit?
3, should I consider narrowband imaging?

There is one other option, but being realistic, I'm not sure it will be a practical one. Go somewhere darker! Trouble is, I have a day job. So I don't have much time on weekday evenings and weekends aren't much better for me to go out somewhere else. I doubt I can get anywhere much better within 30 minutes travel time.

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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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 Post subject:
PostPosted: Sat Oct 30, 2010 12:54 pm 
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Joined: Tue Jul 27, 2010 8:57 am
Posts: 1551
Location: Winterpeg, Manisnowba, Canada
Hey Popo.

I've never personally used filters for my DS (Or any astrophotography for that matter), although I've heard better things about the UHC filters over the CLS filters. Perhaps you could switch, although I don't think that the UHC provides enough benefits to switch.

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-Evan

Gear: 7 Nikon Nikkor AI-S and AF-S lenses, SB-700 flash, Nikon D7000, Nikon FM, variety of accessories

"There are no rules for good photographs, there are only good photographs."
- Ansel Adams


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 Post subject:
PostPosted: Sat Oct 30, 2010 2:57 pm 
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Joined: Sun May 25, 2008 12:48 pm
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Location: UK
I have to assume where you are light pollution isn't a major issue then. I'm towards the edge of a large town (pop 100's of thousands) so it's challenging to see much of anything unless the air is exceptionally clear. Based on the transmission charts the UHC has about 2 to 3 times less bandwidth (>one stop) around 500nm than the CLS. So I think that'll help in the blue/green channels where I'm currently limited. The response around red channel isn't significantly different between CLS and UHC and it isn't a problem for me in that region at the moment.

_________________
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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 Post subject:
PostPosted: Sat Oct 30, 2010 3:19 pm 
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Joined: Tue Jul 27, 2010 8:57 am
Posts: 1551
Location: Winterpeg, Manisnowba, Canada
Light pollution isn't bad for me, in fact, with a 30 second exposure and a W/A lens, I can get some nice reds in the North American Nebula. I live in a suburb, and there's a field behind my house, so the light isn't bad.

_________________
-Evan

Gear: 7 Nikon Nikkor AI-S and AF-S lenses, SB-700 flash, Nikon D7000, Nikon FM, variety of accessories

"There are no rules for good photographs, there are only good photographs."
- Ansel Adams


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