A tilted card *above* the mark probably won't work, as I'm sure you've
decided by now. You could use a tilted card, whose edge is in contact with
the ground. Move it until the image of the Sun and shadow edge are split
over the grounded edge, 50% on the card, 50% (elongated) on the pavement.
At
PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: Monday, June 17, 2002 2:36 PM
Subject: Re: Image Problem Solved?
In a message dated
06/13/2002 11:58:46 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
A tilted card *above* the mark probably won't work, as I'm sure
you've decided
Patrick Powers wrote:
I haven't tried this myself but it is said you can use this technique for
even smaller holes... Hmmm Tony, do you think it would work for 1.5 -2mm
holes?
Chemical milling (etching) is ideal for any size/shape of hole and would
achieve it in shim brass very quickly using
Dave Bell wrote
Tony, I'd rather say elegant! And any over-etch would only serve to thin
the edge, better approaching the ideal zero thickness hole... Thin brass
stock is available at the nearest craft store (for embossing paper), and
wouldn't ferric chloride from the electronics shop do for
On Thu, 13 Jun 2002, John Carmichael wrote:
This is embarrassing, but I've just repeated the pinhole experiment with the
setting sun which is about 15 degrees high and I must conclude that the
results of my earlier test that I did at noon were flawed. At noon I had
tried to hold the pinhole
Message text written by INTERNET:sundial@rrz.uni-koeln.de
Perhaps the only way to get a truly 'burr-free' and 'surrounding
depression free' hole is to chemically etch it.
Not sure this message of mine is really relevant to those making shadow
sharpeners where the hole size might need to be
Dave Bell wrote:
One important consideration here is to make the pinhole in as thin as
possible a sheet of material. Foil stretched over a hoop would work well,
and be easy to punch. Pinhole camera buffs make a point (heh!) of drilling
a hole, using a sharp needle, with a backup block of plastic
On Fri, 14 Jun 2002, Tony Moss wrote:
Dave Bell wrote:
One important consideration here is to make the pinhole in as thin as
possible a sheet of material. Foil stretched over a hoop would work well,
and be easy to punch. Pinhole camera buffs make a point (heh!) of drilling
a hole, using a
Problem solved!
Mac Oglesby just solved the image ellipse problem that I had with the
pinhole sharpener when the sun is low. I had been holding my sharpener
perpendicular to the sun's rays which produces an elongated image of an
ellipse around sunrise and sunset. He said that if I hold the
On Thu, 13 Jun 2002, John Carmichael wrote:
Problem solved!
Mac Oglesby just solved the image ellipse problem that I had with the
pinhole sharpener when the sun is low. I had been holding my sharpener
perpendicular to the sun's rays which produces an elongated image of an
ellipse around
: John Carmichael [EMAIL PROTECTED]
To: Sundial List sundial@rrz.uni-koeln.de
Cc: Rob WM. Vugteveen [EMAIL PROTECTED]
Sent: Thursday, June 13, 2002 12:44 PM
Subject: Image Problem Solved!
Problem solved!
Mac Oglesby just solved the image ellipse problem that I had with the
pinhole sharpener when
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