Alexei
>
>Some time ago I read on some website about a Laser Trigon - which was a
>laser fitted onto an equatorial axis which I believe simulated the sun and
>could be used for the projection of the sun rays on any surface.
>
>However I have no idea where I saw this and would be grateful if someone
>knowledgeable about this Laser trigon would give further information about
>this instrument.
>
I designed and made a precision laser trigon to overcome thw problems
associated with settimg out hourlines on the conical surface of the 6 metre
Silverlink Sundial.
See my website address below for a picture of the dial.
The instrument is based on a length of heavy-duty aluminium angle which can be
placed on the edge of any large square-edged gnomon. Mounted on one end of the
angle and truly perpendicular to it is a 3/16" thick brass 'protractor' with
precision-reamed holes every 3.75° around its circumference. An aluminium
alloy arm, pivotting on a central pin can be set to hours and quarters. The
pivot pin is partly milled away so that the arm swings about the interior
corner of the angle and hence the true edge of the gnomon style.
At the outer end of the arm is a pivotted diode laser arranged so that it can
sweep out each hour line from the root of the style to the tip. All bearings
are pins held in precision 'vee' grooves by light leaf springs to avoid any
possibility of wobble.
A tip for the unwary. Do NOT assume that the laser beam is truly coaxial with
the exterior of its mounting.
Place the housing in a precision vee block and rotate it while watching the
spot on a distant wall.
If it is truly coaxial (very unlikely) the spot will not move, if not a circle
will be described,
There are many adjustments to be made to ensure alignment and accuracy which I
will not attempt to describe here in words.
JPEG of the instrument in use on request.
Footnote. After all my care and precision, the gnomon, cast iron and weighing
several tons, was delivered rough 'as cast' without the true machined edge
which had been promised.
A chain is only a strong as its weakest link! :-(
Tony Moss
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\ ** ******
\\ ** **
\\ ** *******
*\\ ** **
*\\ ******* *******
**\\
***\\ Tony Moss, Lindisfarne Sundials
*****\\ 43, Windsor Gardens, Bedlington,
*******\\ Northumberland, England, NE22 5SY,
**********\\ 55° 07' 45" N 1° 35' 38" W
Tel/FAX +1670 823232
Mobile: 07970 208 540
Website: http://www.lindisun.demon.co.uk
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The first choice for a Millennium Sundial.
(every one Y2K compliant)
Horizontal, Vertical, Declining, Analemmatic, Equatorial,
Polar and Capuchin Sundials individually made in solid
engraving brass. Professional-quality Dialling Scales,
'engine-divided' meridian layout instruments with software.
Analemmatic dial plots - any size for any latitude.
Graduation, re-cutting and restoration of scales.
'Lintique' patination of brass.
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