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    Re: Backup Celestial Navigation Kit
    From: Francis Upchurch
    Date: 2015 Apr 30, 22:16 -0700

    Robert,

    Great game!

    My basic, minimalist kit is :

    Davis 111 with Dec and EQ of T tables stuck on. Cheap casio waterproof watch attached to handle, whole enclosed in aluminium "Faraday cage" to hopefully protect against lightning EMP? Also my relatively cheap, Chinese made Rotary automatic mechanical watch, if worn constantly , keeps regular rate of about -25 secs per day. Plastic protractor doubles as "nocturnal" for direct measurement of Polaris correction.

    With this minimal kit can do meridian alts for lat and long (using double alts say 1hr pre and post LAN to get time of LAN) , Polaris for lat using nocturnal for direct correction.(don't need dec or EqofT or time)

    I have done this experiment  a few years ago and generally got within 15nm lat (no time needed)and 20-30 nm long. (accurate time needed).

    The main issue for me is "so you know your lat and long, but without charts,  not very helpful?" I have small area charts, but to cover the whole globe in a small kit might be a challenge? Any ideas? So my real world survival kit includes my smart phone plus hand operated charger in waterproof Faraday cage. The smart phone has GPS and charts! so a big cheat!

    A few years ago, I also tried the lunar altitude game, but using the graphic Chichester method described in Hewitt Schlereths great little book "Commonsense Cel Nav." this also has permanent almanac and log/trig tables,so everthing you need. (except you need almanac data for lunar alts etc.) ( I use my trusty Astra B for lunars, never tried the Davis 111 for that).

    I found the lunar alt method pretty inaccurate (30nm ish) and prefer proper lunars (but need almanac for both methods) (20nm ish).

    Two years ago ,I tried a few experiments with a "no clock" method. (need rough guess of GMT (+/- an hour or 2 for moon HP and SD from almanac)

    Several "simultaneous" moon and sun alts and Lunar distances over approximately five minutes .Graph them and choose "simutaneous" Alts and LDs. Do lunar clearance to get GMT of the "simultaneous" readings.(need "pre-1912 alamanac" giving 3 hourly LDs,I cheated and made one up for a few weeks from Franks website) Do classic moon and sun reduction using the GMT from the lunars, should give reasonable 2 body "fix " if big enough difference in moon/sun az. (best I got was about 20nm out, but only did a few. Will try more this year hopefully).

    All good fun.

    From one lunatic to another!

    Best wishes

    Francis

     

       
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