NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Level of observation accuracy in medium seas
From: Robert Gainer
Date: 2004 Jul 22, 22:25 +0000
From: Robert Gainer
Date: 2004 Jul 22, 22:25 +0000
David, Do you think that a large breakfast would affect the precision of the observation or the accuracy of the results on this noon sight? Robert Gainer >From: David Weilacher>Reply-To: Navigation Mailing List >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM >Subject: Re: Level of observation accuracy in medium seas >Date: Thu, 22 Jul 2004 16:28:22 -0500 > >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: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM >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 _________________________________________________________________ Don�t just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/