Re: Which major star parties have Bortle Class 1 skies?

On Sep 24, 6:13 am, Per Erik Jorde <pe...@xxxxxxxxxxxxx> wrote:

Pardon changing subject, but I am interested in how to determine
naked-eye limiting magnitude. Should I choose stars near zenit?
Should I use direct vision or averted?

By convention, naked-eye limiting magnitude is measured at the zenith
(unless stated otherwise), and uses averted vision. But NELM has very
little value as a way of comparing your skies to someone else's,
because there's a variation of at least one full magnitude, and maybe
more, in NELM estimates from different individuals under the same
skies.

However, I don't think I have ever
seen the velvet black sky that some observers describe.

That's because no such thing exists. "Velvet black sky" is a term
usually employed by people who are used to severe light pollution. In
fact, skies devoid of artificial light pollution are quite bright.

I live on the countryside in a sparsely populated area in
southern Norway (local community of 1864), with two smaller towns
(population ~6000 each) some 30 - 40 km away.

You might try to locate yourself on the Light Pollution Atlas at
http://www.lightpollution.it/worldatlas/pages/fig4.htm

I have never actually seen M33 naked eye

It's worth a another try! I can see it at sites with obvious light
pollution. But it's mighty subtle.

or the zodiacal light.

Well, there we run into one of the fundamental problems with the
Bortle Scale. The visibility of the zodiacal light depends heavily on
your latitude. It must be very hard indeed from Norway. Though it's
also worth pointing out that the zodiacal light is one of those things
that seems very difficult and exotic until the first time you've seen
and identified it. After that, it doesn't seem so hard after all.

Many of the Milky Way features cited by Bortle are also heavily
latitude-dependent. For instance, the bulge into Ophiuchus is a real
test of dark skies here at 42N, and must be extremely hard at 60N. But
the first time I saw it clearly, in southern Arizona, it seemed quite
bold and bright. And from the Southern Hemisphere, where it's nearly
overhead, it probably shines through fairly heavy light pollution.

.

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