Re: AW: [APML] Tenerife skies (was: Exposure times with IDAS filter)

[Glenn Shaw <gshaw@alaska.net>]

Dear Philipp:

My apologies for putting politically incorrect statements inadvertantly into the APML. I was only stating that its a natural tendency
for Europeans to taut things in their backyard, which they identify with and vice versa of course for Americans and probably for every
other nationality out there!

Here is, I think, an objective statement about sky transparency:

Locations in and around North Africa are quite turbid. I've travelled the area and the skys are yellow. The optical depth is generally
0.1 to 0.3 or higher in the mid visible region of the optical spectrum. This means, for typical zenith angles of exposures, a factor of
two additional time spent to record an image.

During times after large scale volcanic eruptions, such as Pinatubo, or Katmai a veritable worldwide effect occurs that can mean to
increase astronomical exposures by maybe 10 to 30% and in extreme cases by a factor of two.

Euroope and virtually everything east of central USA is quite polluted and, provided one can find a dark site (increasingly difficult)
and a dry site where the aerosols aren't activated by high humidity (also difficult), and all this leads to an increase of around
probably 30% that one must use to record an acceptable image.

The western USA is really quite splendid for astrophotography. It is a large and easily accessible area. Areas around western Texas,
Arizona, Nevada, California, Arizona, Utah, Idaho, Oregon abound with excellent sites. Nothing like them can be found anywhere I know of
in Europe due to Europe's high population density and crowded conditions.

South america is excellent, but the logistics are tough. Central to south Africa can be good, but the logistics are tough and you may or
may not survive. Forget Asia: the recent INDOEX experiment showed that the whole of India and Indonesia are massively polluted from
everything from biomass burning from 3 cycle engines. Forget it. You could do really excellent work in places like the Antarctic in
winter, but nobody could survive the terrible conditions.

Frankly, I think our European friends should come to the United States, revel in John Wayne land, some of the most beautiful land in the
universe and teach us Americans some culture....

opps.....there I go again......

glenn

Philipp Salzgeber wrote:

> If Europeans are so nationalistic about their skies - why is the biggest (by far) European Observatory, and at another location the
> VLT and soon the Submillimeter Array located in the Atacama desert in Chile in Southern America? Please don´t judge the peoples of a
> continent because of some personal experiences with a limited number of individuals.
>
> If dust in the atmosphere is such a problem, astronomical research should have been put to a halt for some time after the Pinatubo
> eruption. As far I know photometry has the biggest problem with transparency. Imaging and Spectroscopy are not that strongly
> affected.
>
> with best regards
>
> Philipp Salzgeber
> [p***ed off European ;-)]
>
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