Re: ATM re: exchange rate -Reply

[andydtg@alpha1.phoenix.net]

More on:
>>> Regarding the spun mirrors...  They are indeed Hg, with a
>> coating of oil to keep it from oxidizing.  They can only be
>> used to observe at and around the zenith, though.  
>> 
>>
>
>Regarding Hg mirrors: A quest speaker at our local astronomy
>club gave a talk on mercury mirrors that he was involved in.
>The observatory was in Alaska and used for aurorae observation.
>The mirror consisted of a large parabolic fiber-glass pan supported
>on an air bearing. They put some mercury in the bottom of the pan
>and spin the pan up. No oil is used for an overcoat. After a few weeks
>when the mercury gets oxidized they just shut down the pan and skim
> the oxide off. Yeah they do wear masks when in the observatory
>for maintenance.

NASA has a 3-meter mercury telescope near Cloudcroft NM, located in the
dome that used to house the USAF 48" satellite tracking telescope.
The 3m is used to monitor orbital debris with a large CCD array,
which is read out in sync with sidereal time (I think). The Hg is
only a few mm thick & is supported by a spin-cast fiberglass dish
that is close to parabolic shape. They also don't use oil to cover
the Hg & it's operated in a sealed off room.

There's a web page for the facility that can be found by searching 
for 'Cloudcroft'.





Andy Saulietis / DTG Alt-Az-Fp Drive Systems
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