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    Avery Point, CT Dip Angle
    From: Bruce J. Pennino
    Date: 2013 Apr 6, 06:58 -0700

    Hello All:

    After doing Blue Hill dip and having a little more confidence, I went to long Island Sound, just west of Mystic. This location is the extreme eastern end of the Sound. UConn has a branch campus actually on the point by the lighthouse and there is a nice beach for CN sights at close by Eastern Point.

    Data Set 5 April 4, 2013. Meteorological data would be available from New London Coast Guard or sub base, or other sources, using Topcon total station/EDM
    with mini prism pole , with inverted basket to hold prism.

    5A Location at college sailboat "420" beach area at corner of protecting stone wall, on entrance road to campus. Surveyor's magnetic nail in pavement, 31.7 ft from "L" end of stone/concrete wall. Setup between storage garage and "L".

    Strong wind from 240* mag, sight to about 240* mag.Tripod vibrating. Many white cap waves in view in cove, 2 ft waves rolling onto beach. Gray haze on horizon, blue sky, CLEAR CRISP horizon line, but not particularly wavy in scope.

    Time 12:33 EDT just after low tide. Tide range only 2.6 ft here.

    average of 8 sights:measured dip = 4.42 minutes {at} height of eye = 13.5 ft

    5B On UConn campus, due east of light on dock/parking area behind academic building, adjacent to inlet going to boatyard, small islands to east. Set up out of wind by concrete wall. Measured down to water level with tape.

    Time about 5:30 EDT, about high tide. Sound is calm, no wind,no waves, solid tripod. Sight is to about 200* mag (later realized looking toward west of Race Point.....saw a light house, Valiant Rock?) Excellent horizon

    average of 8 sights: measured 2.99 minutes {at} height of eye = 13.1 ft

    Special note: Because I was on an inlet, tried to closely observe any local anomaly in water level between Sound and datum level for sight. All seems valid, calm.

    5C Moved EDM to vicinity uphill from base of lighthouse (focal plane of light is 55 ft above HW. Measured to middle of lighting device (as best could tell) and calculated that point sighted was about 52.6 ft above NORMAL HW. The actual "light" could easily be a ft or more higher, so height of light is about right.

    Dip sight to about 200* mag . Wind has increased, small isolated white caps, tripod vibrating.***Careless setup/procedure to establish BM on base of lighthouse (could be an elevation error of 0.5 ft plus or minus?)**** Must redo
    with setup at light, back sight down to inlet with direct simple measurement resulting.

    average of eight sights: measured dip = 4.41 minute height of eye about 22.5 ft

    Summary of Measured Dip (minutes of arc)
    H ft Dip

    AP 5A 13.5 4.42
    5B 13.1 2.99
    5C 22.5* 4.41
    BH 4B 627.0 23.10
    4C 676.5 24.50

    All dips are measured average of 8-10 points. AP= Avery Point; BH=Blue Hill.


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