[AZ-Observing] Re: Summer Twilight
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 18 Jun 2014 14:00:34 -0400
---- 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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