One other caveat... if from your location, the aurora were to appear twice
as intense as compared to my location, then likely your exposure time would
be half of mine, or your aperture stopped down.
Tom C.
From: "Tom C" <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Subject: RE: Northern Lights
Date: Tue, 09 Nov 2004 19:05:51 -0700
Hi Mike,
I've found auroras, at least at my latitude, to be even more variable and
inconsistent as to timing of appearances. Electricity, it's kin magnetism,
and the solar wind appear to be very fickle lovers.
However, I've found, in general, the following exposures to work:
f2, ISO 400, between 20 & 30 seconds.
f2, ISO 800, around 15 seconds.
The variable we cannot control is the intensity of the aurora or the pulse
like surges in brightness that occur during the exposure. I count off the
seconds at a fairly inconsistent rate, so I'm sure my exposures, usually at
ISO 400 last for variable lengths between 20 and 30 seconds. Many of the
pictures I just posted were taken at an attempted exposure time of 27
seconds.
I also tend to expose at ISO 400 when shooting towards the north, and at
ISO 800 when I get further away from the pole. This means I can have
shorter exposures, lessening the star trailing effect when shooting away
from the pole.
Tom C.
From: michal mesko <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
To: <[EMAIL PROTECTED]>
Subject: Northern Lights
Date: 09 Nov 2004 23:55:13 +0100 (CET)
Hello List,
just saw the first aurora in my life. It was very pretty, but at least as
much educative. Here are the lessons learned:
I have been looking for a geomagnetic storm since I came to Finland,
checking the monitoring site (http://www.sec.noaa.gov/rt_plots/kp_3d.html)
almost daily. As the gray-steel skies started to break up at the sunset
today, I rushed to the city to buy rolls of Provia 400F, one of the films
generally recommended for aurora photography.
Being young and naive, I set out to photograph the lights right after
twilight at 5pm. My idea was that aurora would dance over the sky for the
whole night, only to disappear with the first rays of the dawn. :) After
more than two hours of stumbling through the scary dark forest and
catching cold by the lake, I packed up and went home. Of course an hour
later, the lights did appear. Rushing to the lake again, I lent my tripod
to a friend to play with and went looking for The Perfect Composition. By
the time I found it, the sky turned dark again.
Puzzled, I approached a seasoned (or so it seemed) aurora photographer on
the scene. He explained that aurora usually passes our latitude from 10pm
to 11pm going down from north to south. It returns after midnight at 1am,
going back north again. Apparently, it is one of those things everyone but
me knows. ;-) It has something to do with the position of sun, he even
carried a PDA to check the angle at which the solar winds hit the
atmosphere.
I then inquired about the exposure times. What he used is very
inconsistent with the resources on the internet
(http://www.ptialaska.net/~hutch/aurora.html,
http://w1.877.telia.com/~u87717747/english/bildarkiv_4.htm and more),
where they talk about 400 speed, fast lens and about 30 second exposures.
He was using f2.0 lens, ISO 50 and about four seconds! My friends digital
camera had the right exposures at ISO 100, f2.8 and 8-15 seconds. Anything
longer and the photo was blown out. And the aurora was supposedly on the
faint side.
Sorry for the long post. :] I would like to hear comments of experienced
aurora photographers, anyone?
Mike
(http://skwid.wz.cz)
________
Svetova kniznica SME - literarne klenoty 20. storocia -
http://knihy.sme.sk
