[time-nuts] Heliostat

Brooke Clarke brooke at pacific.net
Sat Jul 2 15:12:36 EDT 2016


I recently got an Eastern Science Supply Co. demonstration heliostat, that's to say it's small enough to easily hand 
hold. I've go it working but have some questions.
Based on some Waterbury Clock Co. patents I think is was made in the late 1920s or early 1930s.  ESSCo was into 
astronomy.  I got a book they published "A Manual of Laboratory Astronomy, for use in introductory courses by Harlan 
True Stetson Phd, 1928 - but no mention of the heliostat.

The base has level vials and an elevation scale for the clockwork driven lower mirror that's clearly calibrated in 
latitude.  The lower (clockwork driven) mirror has a pointer to a scale divided into 24 hours, one half black and the 
other half white.

I'm guessing that in order to properly setup this heliostat you need to know the local mean solar time, i.e. correct for 
Daylight savings, EOT and your offset from the time zone meridian.  That way you could preset the time then rotate the 
base and tilt the lower mirror until the sun's image was centered on the top mirror.  For now I sort of pointed it at 
north and adjusted both the lower mirror tilt and the time setting to get the sun along the axis of rotation.

Were heliostats also used for looking at stars?  i.e. could the Fast-Slow clock adjustment be used to make the clock 
work for either solar or sidereal time?

Have Fun,

Brooke Clarke
The lesser of evils is still evil.

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