|
|
|
|
|||||
|
||||||
From: David Weilacher (no email)
Date: Thu Jul 22 2004 - 17:28:22 EDT
An experienced navigator should be able to determine he was in or near lake michigan during daylight hours (and if he was hungry, that would indicate somewhere around noon or American)
-----Original Message-----
From: Bill <>
Sent: Jul 22, 2004 4:13 PM
To:
Subject: Level of observation accuracy in medium seas
Had a chance to make my first "on water" observations last weekend.
First sun shot was from the pier using short dip and was right on the money
(according to GPS fix). Better lucky than good ;-)
Second was a bit more challenging.
Location: Lake Michigan near Michigan City (southern end of the lake).
Boat: 34' Catalina fin keel with tall rig (36' Catalina mast and sails)
Day before on the water:
* Wind out of the north (started 005d and backed to 340d)
* Started at 12-18 kn, end of day 18-23 with puffs to 28+ (true, not
apparent). Headsail at 110, 1 reef in main.
* 4-6 foot confused seas. By day's end waves in the 8 foot range were
forming.
Day of shoot:
* Wind still out of the north (started 005d and backed to 340d again)
* 10-15 kn true, puffs to 19+. 150-130 headsail, full main.
* 3-5 foot confused seas. By day's end waves in the 6 foot range were
forming.
* Course 274 true (just above beam reach). Heel 12-22 degrees.
* Slight haze, visibility approx. 15 nm.
* Approx. 8 nm off southern shore so had the horizon backed by sand dunes.
Did a noon sun shoot within seconds of local noon with 0 magnification sight
tube.
Question:
What degree of accuracy (range?) would an experienced sextant operator
expect under these conditions:
1. With 0 magnification sighting tube
2. With 4X telescope
Dave Weilacher
.US Coast Guard licensed captain
. #889968
.ASA instructor evaluator and celestial
. navigation instructor #990800
.IBM AS400 RPG contract programmer
|