Hello:
I used what is being called a shadow sharpner in a noon mark made by
drilling a hole in an aluminum plate located at the bottom of a south facing
sky light. To determine the hole size I first tried various holes
in cardboard. A starting point is that a pin hole camera would have
an "f"
A couple of you asked about where I read of the shadow sharpener.
I have the article, but it is packed away in storage. It would probably
take several hours to find it.
The best I can remember, it was in Sky Telescope magazine (or possibly
Astronomy magazine) in one of the issues between 1995
Roger, thank you for your post. The Shadow Sharpener being a pinhole camera,
why not replace the gnomon with a pinhole? One then could center a circle on
the image and determine the time from its position.
My rule of thumb is that the angular resolution of a pinhole is one radian (57
At 22:48 3/05/1999 EDT, [EMAIL PROTECTED] wrote:
It would seem to make more sense to drive on the right side, since the
handedness of a supermajority of people is right handed, allowing the
stronger hand in close proximity to the shifter. That and being an American
that's what I'm used to ha
At 08:53 PM 5/4/99 -0400, Patrick Powers wrote:
It was Sweden some time ago. They changed over at midnight. However, it
was sensible for them to change; not only was it easier - relatively small
and sparse population - but previously they drove mostly lefthand drive
cars on the left !!
Gordon Uber [EMAIL PROTECTED] wrote:
Roger, thank you for your post. The Shadow Sharpener being a
pinhole camera, why not replace the gnomon with a pinhole? One then
could center a circle on the image and determine the time from its
position.
To form a good solar image the plane of the
Hello all:
I was just thinking that on a horizontal sundial that the true shadow point
would ONLY be at the center of the penumbra at high (apparent) noon. In the
late afternoon or early morning, the sun would be to the side of the style,
causing the shadow to strike the dial face at an angle.
As far as the tounge-in-cheek comment that the more powerful hand should be
availible to hold the wheel--in the days before power steering this may have
been relevant, but the shifter requires more manual dexterity, of course
automatic transmission now makes shifting easier, so whatever you
Hi John,
You believe that you are right. The attached sketch (Shadow.jpg) shows this
fairly clearly. At 21 kb it is too big to post on the mailing list unless
there is a strong demand.
Roger Bailey
At 06:45 AM 5/4/99 -0700, you wrote:
Hello all:
I was just thinking that on a horizontal
Gordon,
Roger, thank you for your post. The Shadow Sharpener being a pinhole
camera,
why not replace the gnomon with a pinhole? One then could center a circle
on
the image and determine the time from its position.
Some years ago, when thinking about heliochronometers, I realized that the
To all:
As soon as I launched my previous note, re: Shadow Sharpener,
I realized I had failed to attach the GIF image file pin-htel.gif ...
1627 bytes.
Here it is: (pinhole compound solar telescope)
Bill
Attachment converted: MAC Hard Disk:PIN-HTEL.GIF (GIFf/JVWR) (00015069)
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