[AZ-Observing] Re: Summer Twilight
- From: Paul Lind <pulind@xxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 18 Jun 2014 14:30:03 -0400 (EDT)
Lynn and Ken and I were noticing it, but we don't have any photographic proof.
Maybe we were seeing zodiacal light, but it seemed too low and not pyramidal
like zodiacal light.
It sure hung around for a long time after the sun was 18 degrees down.
----- Original Message -----
From: Tom Polakis <tpolakis@xxxxxxx>
To: az-observing@xxxxxxxxxxxxx
Sent: Wed, 18 Jun 2014 14:00:34 -0400 (EDT)
Subject: [AZ-Observing] Re: Summer Twilight
---- Paul Lind <pulind@xxxxx> wrote:
> While observing at Ash Fork during the last DOTM we noticed that the evening
> twilight crept slowly northward, reaching a point almost below Polaris. This
> was long after the end of astronomical twilight, which was listed as about
> 9:20 pm. The phenomenon is logical since the sun was only about 30 degrees
> below the horizon in the north at its very lowest...
Unless you were seeing some airglow that happened to be following the sun's
azimuth, I doubt that you were seeing twilight in the north. In my experience,
a sun altitude of more than 18 degrees below the horizon really does mean that
it's as dark as it's gonna get in that direction.
Did anybody take a wide-field image of the northern horizon at around midnight?
Tom
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