[time-nuts] finding time astronomically.

Chris Albertson albertson.chris at gmail.com
Mon Jan 23 18:58:24 EST 2012


I think you'd want a slit, not a pin hole.  The pin hole would be
better but it would only work one day a year.  And it could be plugged
up.

I'm thinking the best way to build this might be to paint a sheet of
glass after masking out a very thin strip with vinyl tape.  Face the
uncoated side to the sun. .  The glass would keep dirt and water out.
Aim it at the ecliptic and surround the glass with bird spikes.  Maybe
use a filter to reduce skylight but let IR in.  To make the blue sky
look more black.

I think the optimum width of the slit, or pinhole diameter to make it
match the width of the photo detector.   Making it wider does not put
more light on the detector.   The geometry when give you a nice raise
and fall.  You could place a full column of photo diodes in back of
the slit


On Mon, Jan 23, 2012 at 3:10 PM, Brooke Clarke <brooke at pacific.net> wrote:
> Hi Chris:
>
> I would say you want an optimum hole diameter for imaging the Sun.
> Sort of like the f/100 school of photography.
>
> For a few years I drove brass tacks into a hardwood floor at exactly noon
> where the tack was placed at the center of the Sun's image using 3x5 cards
> with nested ellipsis of different sizes with a small hole in the centers.  I
> choose the "pin hole" diameter that was slightly larger than the hole size
> needed for good overall focus.  If the hole is smaller than needed for good
> focus you are getting a much dimmer image and much larger and the image gets
> fuzzy.  For this application maybe a hole somewhat larger that still has the
> same peak intensity as the in focus hole.
>
> Another idea would be to use a photo sensor to read the spots from a
> Dipleidscope.
> http://www.prc68.com/I/Dent.shtml
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/Brooke4Congress.html
>
>
> Chris Albertson wrote:
> . . .
>>
>>
>> You don't want a pin hole or you'd be adjusting the aim every day
>
>
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-- 

Chris Albertson
Redondo Beach, California




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