Next message: Frank Reed: "Re: Level of observation accuracy"
I have always wondered if I could make a fairly accurate sextant-like device
out of just a heavy weight (plum bob) on the end of a line hanging from
something, perhaps another line or a tree. Anyway, then I could measure
with an accurate tape measure the height of the line, measure the length of
the shadow, and take some arctangents and get an angle. If the line and
length of shadow are long enough, serious accuracy could be achieved, no?
Anyone done this or see any obvious deficiencies in this inexpensive method?
Dan
-----Original Message-----
From: Navigation Mailing List [mailto:]On
Behalf Of Frank Reed
Sent: Saturday, July 24, 2004 12:29 PM
To:
Subject: Re: ReRe: Level of observation accuracy
Bill wrote:
"While I hate to admit it, started this quest a couple of months ago with
Celestaire's Wurzburg cardboard sextant. Manufacturer claims it can be
accurate to within 8 minutes of an arc. With a little mirror tweaking and
putting a horizontal slit across the eye side of the viewing tube, am
getting within 2-3 minutes consistently from seated position on a stable
platform or tripod mounted. So I figure plus/minus 3 minutes is my range of
instrument slop. Humidity does affect index error. <G>"
Very interesting. Cheap sextants are nothing to sneeze at. Most people
eventually prefer to get a fancy one simply because they look so
professional, but by practical standards plastic and cardboard sextants are
very good.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
