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#1
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Aurora tonite?
Here's one to toss around awhile.
There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... |
#2
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Aurora tonite?
"Tim Conway" writes:
Here's one to toss around awhile. There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... Now that's a fascinating question. Also, my how times have changed (the light loss of a polarizer could not conceivably have been tolerated a decade or two ago for a subject as faint as the aurora). I can't think of any of the usual polarizaiton mechanisms that would polarize parts of the aurora, and I can't think how the generating meachanism could make it polarized to begin with, but my physics-fu is very very amateur, so don't consider this at all conclusive. -- David Dyer-Bennet, ; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info |
#3
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Aurora tonite?
On 2012-05-09 13:43 , Tim Conway wrote:
Here's one to toss around awhile. There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... The loss of about a stop won't help. And if you shoot the aurora with a reflection off water I would expect you'd really want them in the image. -- "A person with a new idea is a crank until the idea succeeds." -Samuel Clemens. |
#4
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Aurora tonite?
On 10/05/2012 5:43 a.m., Tim Conway wrote:
Here's one to toss around awhile. There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... Ideally, you should not use any filter at all, as the main green spectral emission colour has very narrow bandwidth, and the result can be interference patterns of converging ring patterns from internal reflectance within the flat filter glass. There's a large active sunspot (AR1476) coming to face our way over the next few days, as they say "crackling with activity". If that one really lets rip, then the results could be interesting. You can get information and auroral oval forecasts he http://spaceweather.com/ |
#5
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Aurora tonite?
On Wed, 09 May 2012 20:01:51 +0200, Mxsmanic
wrote: Tim Conway writes: Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... I can't think of any reason to use a polarizer. Remember you lose a stop with a polarizer. And if the light that you want to record is already polarized, you could lose a lot more. Not for auroras, I don't know about them, but for rainbows I've thought a polarizer should help. The rainbow light is polarized, the polarizer will blank it out, so 90 degrees from there it should reduce the background light and seemingly enhance the rainbow. I haven't had the camera, polarizer and rainbow together all at the same time to try it. |
#6
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Aurora tonite?
On 5/9/2012 5:11 PM, Me wrote:
On 10/05/2012 5:43 a.m., Tim Conway wrote: Here's one to toss around awhile. There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... Ideally, you should not use any filter at all, as the main green spectral emission colour has very narrow bandwidth, and the result can be interference patterns of converging ring patterns from internal reflectance within the flat filter glass. There's a large active sunspot (AR1476) coming to face our way over the next few days, as they say "crackling with activity". If that one really lets rip, then the results could be interesting. You can get information and auroral oval forecasts he http://spaceweather.com/ Fascinating site. thanks for posting. -- Peter |
#7
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Aurora tonite?
On 11/05/2012 10:54 a.m., PeterN wrote:
On 5/9/2012 5:11 PM, Me wrote: On 10/05/2012 5:43 a.m., Tim Conway wrote: Here's one to toss around awhile. There's a solar flare today which means tonight there might be good "northern lights" occurrences in the Northern areas. Question: Does a polarizer on the lens help in any way; hinder; no difference? ie. other than the usual darkening of skies, and or reflections on water... Ideally, you should not use any filter at all, as the main green spectral emission colour has very narrow bandwidth, and the result can be interference patterns of converging ring patterns from internal reflectance within the flat filter glass. There's a large active sunspot (AR1476) coming to face our way over the next few days, as they say "crackling with activity". If that one really lets rip, then the results could be interesting. You can get information and auroral oval forecasts he http://spaceweather.com/ Fascinating site. thanks for posting. Yes. There's been a bit of media coverage of solar events as we're approaching "solar maximum", probably due to better observation and fantastic images/video from SDO in particular, but probably also genuine concern about communication satellites etc, and popular doomsday theory of all kinds. But this solar maximum looks like being a bit of a fizzer: http://www.swpc.noaa.gov/SolarCycle/index.html Tracking very close to (2008) "consensus" prediction. (I did read some prediction a few years ago claiming that as we'd come out of a very low solar minimum, we were in for a massive solar maximum - but so far the consensus view seems to be right) This solar maximum probably isn't going to be a great period for auroras, but OTOH digital photography means we'll probably see some great photos. The M5 flare yesterday got some media attention, but there was no CME headed our way, and the impact seems to have been only an "R2" radio blackout: http://www.swpc.noaa.gov/NOAAscales/...RadioBlackouts which from the table, happens 350 times / 300 days over a typical solar cycle. Hardly an unusual event (beautiful SDO video of the flare though). This news: http://www.theregister.co.uk/2012/05...ed_by_the_sun/ appeared in only a few newspapers worldwide. The implications might have been seen to be a bit hot to handle - or perhaps science reporters don't bother to report news unless hollywood covers the topic first. |
#8
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Aurora tonite?
charles wrote:
Not for auroras, I don't know about them, but for rainbows I've thought a polarizer should help. The rainbow light is polarized, the polarizer will blank it out, so 90 degrees from there it should reduce the background light and seemingly enhance the rainbow. I haven't had the camera, polarizer and rainbow together all at the same time to try it. I've successfully used that approach to enhance reflections but not tried it for rainbows as it hadn't occurred to me that they might be polarised. |
#9
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Aurora tonite?
Gordon Freeman wrote:
charles wrote: Not for auroras, I don't know about them, but for rainbows I've thought a polarizer should help. The rainbow light is polarized, the polarizer will blank it out, so 90 degrees from there it should reduce the background light and seemingly enhance the rainbow. I haven't had the camera, polarizer and rainbow together all at the same time to try it. I've successfully used that approach to enhance reflections but not tried it for rainbows as it hadn't occurred to me that they might be polarised. If the angle of the polarisation depends on the effective angle of reflection then a polarising filter will emphasize one part and de-emphasize others. The same problem which makes blue sky intensification with a polariser work well with long focal length lenses and be worse than useless with wide angle lenses. -- Chris Malcolm |
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