NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Level of observation accuracy
From: Dan Allen
Date: 2004 Jul 24, 12:58 -0700
"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
From: Dan Allen
Date: 2004 Jul 24, 12:58 -0700
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:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Frank Reed
Sent: Saturday, July 24, 2004 12:29 PM
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Re: ReRe: Level of observation accuracy
Bill wrote:From: Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Frank Reed
Sent: Saturday, July 24, 2004 12:29 PM
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Re: ReRe: Level of observation accuracy
"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