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    Level of observation accuracy in medium seas
    From: Bill B
    Date: 2004 Jul 22, 16:13 -0500

    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
    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
    * 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
    What degree of accuracy (range?) would an experienced sextant operator
    expect under these conditions:
    1. With 0 magnification sighting tube
    2. With 4X telescope

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