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    Re: On checking accuracyNavList6074
    From: Byron Franklin
    Date: 2010 Aug 31, 10:38 -0700

    Navigation Notes.
    Analyzing Sextant Sights II.
    By Byron Franklin QMCM (SS) ret
    The article in the issue 94 of The Navigators Newsletter,(Analyzing Sextant Sights) reminded me of the few times that I used SCAR GEAR on the SSBN Abraham Lincoln and a bubble sextant on a Liberty Hull. The Scar Gear is an artificial horizon in the periscope, much like the bubble sextant. In rough sea with both, the observed body moves violently across the cross hairs, making the Observation open to large random errors. The suggested practice is to use an average of many shots of each body to get one acceptable observation for each body or star. After some unacceptable use of the gear, I decide to try another approach to find the best raw shot from a large number of individual shots
    To find the Best shot among the many you need a reliable reference to judge the ever- changing time and elevation of each shot. You must reduce work of each sight to a simple, but easy way of elimination (random) and many shots to one best shot. I concluded that a better solution to the average would be to plot the individual shots on graph paper with a time line (at the bottom) and a slope that a body is traveling upon. This slope would be a systematic reliable reference line for each shot judgment. The time of the first shot would be the start of a 4 minuet time line and also time to compute Local Hour angle LHA for table entree for tabular altitude (tab Hc) of the body. The far base of the horizontal time line of four minutes would start with the LHA and end with LHA1+l, four minutes of time to arc, [one degree] or LHA297 and LHA298.
    At right angle to the time line would be the raw Hc tab. out of the tables, the bottom is LilA 297�s Hc 46 38.1, the right angle at the top would be 298�s Hc 47 17.1. This SLOPE (STAR TRACK) would be drawn from the left beginning of the time line (LHA297 Hc tab. to the top LHA 298Hc tab four minutes later. See graph. Once the graph is completed and each raw shot!Hs is plotted in terms of time and Hs height the Hc slope can be moved parallel to its self among the plotted Hs�s on the time line for best agreement. Each Hs shots should be easy to identify as systematic or random. A selection of one time and Hs shot can then be completed to height observed and to line of position for the fix. (If your Hs don�t match the He on the vertical, add or subtract an amount to fit, move the slope to select you best shot, than use the original Hs. The slope could be corrected for speed and direction during the four minutes traveled. In order to accommodate other star�s slopes, any time and Hs could be used to Finnish the sight and fine the best shot.
    At the time I thought that I was the only user of the slope, Untill I was sent davids writing of the slope.
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