(meteorobs) re Astro versus Nautical Twilight

[wisetdf at Safe-mail.net]

On double checking things it looks like I got my Astronomical and Nautical twilights mixed up.  Sorry about that.

I've no idea about Nautical Twilight, but again in the Summer months at just above mid Northern latitudes the sky is notably less dark during the duration when it is only _Astronomical_ Twilight all night long.  I'm seeming to remember Airglow is a bigger problem in Summer months than Winter ones too.  Looking into that on the web that might be because Airglow seems to have a bit of remnant Dayglow, a lot of Twilightglow and as well some of the usual Nightglow all going on :- http://www.albany.edu/faculty/rgk/atm101/airglow.htm .  In Northern Summer when facing South you've extra starglow because you're facing the Galactic Centre.  All these little bits probably add up, though at Nautical Twilight those are probably fainter than the seeing limit.

The buzzing mosquitoes don't help much either.

You sometimes have to wonder how Scandinavian astronomers manage to do all the work they've done over the years, what with all night twilights and noctilucent clouds all Summer, and bright Aurorae for long parts of Winter, they must have very narrow observing seasons available to them!

Cheers

John