Next message: Frank Reed: "Re: Level of observation accuracy in medium seas"
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:
>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:
>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
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