This is just a conjecture: I do not think this focused image of the
eclipsed sun is a pin-hole artifact. My guess is that it is a focused
image by the lens, but is a 2nd or 3rd internal lens relfection. In
this manner, the image might be reversed, and its brightness greatly
attenuated, so
I tested my cheapo magnets with double pane glass (1/4 thick) and the
bonding force was a lot weaker- not strong enough to hold a small rod
gnomon.
Art Krenzel's super strong Neodymium magnets would surely work.
He told me about this company that sells supper strong magnets at
p.s.
Since these neodymium magnets are so strong, if they are too big, they may
break the glass before falling off! I'm guessing that the magnetic bonding
force is directly proportional to the area of the flat face of a disk
magnet. The bigger the magnet, the more its bonding force. You might
p.p.s.
Please excuse all these emails, but I'm telling you my ideas as soon as they
come into my head.
The smallest mounting magnet they make is just 5/8 diameter. This little
guy packs a powerful force. It has a Pull Force of: 15.63 lbs
See:
Dear Friends
With all this talk of pinhole photography, I thought you might like the
attached - taken over a continuous 6 month period by Justin Quinell of Bristol
over the famous Brunel suspension bridge. He uses a beer can with a nail hole
as his camera The photos are made on photo paper
Hi John,
I notice that they also have a magnetic calculator:
http://www.kjmagnetics.com/calculator.asp
Roderick Wall.
-Original Message-
From: John Carmichael
Sent: Thursday, January 06, 2011 3:47 AM
To: 'Mike Shaw'
Cc: 'Sundial List'
Subject: RE: Glass on Glass Mosaic Indoor
I offered the info below to John Carmichael, a long-time friend. John
suggested I also copy the sundial reflector so here is what I sent to
John earlier.
John, I've followed the sundial list thread on using a magnet to secure
a gnomon. Let me provide you some information about rare earth
