[AZ-Observing] Re: Weather in AZ
- From: gene lucas <geneluca@xxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Tue, 29 Jan 2008 12:03:55 -0700
William (and his son John) Herschel did >most< of their "deep sky"
observing with the so-called "20-foot" telescope, which was a
front-view, 18-inch aperture, f: 13 monster-sized alt-az "Dobsonian",
with a rapidly-tarnishing metal speculum mirror -- equivalent in light
gathering power to a modern aluminized glass 13 inch mirror. The
optical tube assembly (OTA) from the 20-foot is presently on display in
Washington, DC in the Smithsonian. It may be fairly claimed to be the
only telescope with which a >single< observer -- JOHN Herschel -- ever
observed ALL of the major cataloged objects in the ENTIRE sky. The
remodelled "new" 20-foot, construced ca. 1820 with mirrors fabricated by
John and William together, and improved mounting features by John -- the
present OTA on display in Washington -- was taken to South Africa during
1833-38 to complete John's surveys.
Apparently back in those days, for urban observers, the major concern
was "air pollution" from factories, due to dust (few paved streets) and
the widespread use of coal for heating, cooking, and later, steam engine
power. That reached an unhealthy peak (a nadir) during the mid-19th
century, with "black fog" events causing numerous deaths in London. A
similar situation existed in Paris during that era....
"Street lighting" was originally provided by oil lamps, later by
gaslight. Sometimes the fog was so bad in London that they lit the
street lamps all day.....
Gene
(17250)
Richard Harshaw wrote:
>Likewise, Gene, it is amazing to me that Charles Messier did so well from
>Paris with instruments of 4.5" to 6" apertures, and speculum at that! With
>modern lighting comes the modern curse of Urbanis Auroris.
>
>Dick
>
>
>-----Original Message-----
>From: az-observing-bounce@xxxxxxxxxxxxx =
>[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of gene lucas
>Sent: Tuesday, January 29, 2008 10:51 AM
>To: az-observing@xxxxxxxxxxxxx
>Subject: [AZ-Observing] Re: Weather in AZ
>
>Speaking of poor observing conditions.... Ol' Will Herschel moved from one
>awful observing spot to another during his observing career, but did pretty
>good... (He bagged the "original" Herschel 2500.....) Maybe the 40 ft mirror
>just sucked up all the photons ??? :>))
>
>
>[snipped -- GL]
>
>
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