Aurora tonite?

Discussion in 'Digital Photography' started by Tim Conway, May 9, 2012.

  1. Tim Conway

    Tim Conway Guest

    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...
    Tim Conway, May 9, 2012
    #1
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  2. "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
    David Dyer-Bennet, May 9, 2012
    #2
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  3. Tim Conway

    Me Guest

    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 here:
    http://spaceweather.com/
    Me, May 9, 2012
    #3
  4. Tim Conway

    charles Guest

    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.
    charles, May 10, 2012
    #4
  5. Tim Conway

    PeterN Guest

    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 here:
    > http://spaceweather.com/



    Fascinating site. thanks for posting.

    --
    Peter
    PeterN, May 10, 2012
    #5
  6. Tim Conway

    Me Guest

    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 here:
    >> 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/index.html#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/2012/05/08/climate_is_affected_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.
    Me, May 11, 2012
    #6
  7. 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.
    Gordon Freeman, May 11, 2012
    #7
  8. 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
    Chris Malcolm, May 13, 2012
    #8
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