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    Re: Precomputing sextant observations at sea
    From: Francis Upchurch
    Date: 2014 Jan 30, 07:34 -0000

    Thanks for this Gary. It does not sound hokey to me! I’m no pilot, but can only imagine what it felt like to do that. After you had put me on course re Az etc, I went to my Bygrave and did the same thing,( using Franks almanac site for GHA and DEC for 0500 GMT April 1 1931, what did you do?) and the feeling of awe,  to essentially repeat Chichester’s original calculation on an identical instrument ( I also did it on my original Bygrave as a treat!) ! Wonderful! And I also got the exact same result!

    I can’t thank you enough for this.

    If you’re ever in England again to fly moths, please take me up! I’ll let you use my original Bygrave for that trip!

    Didn’t Chichester also have additional problems with vibration from a damaged prop?

    Bye the way, I still have some problems fully understanding the Az/Zn rules. According to my (yours I think) work sheet, for s latitudes where X<90deg, Zn=360-az, which is not what we have here? Apologies for my continued ignorance!

    Thanks again

    Francis

     

    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Gary LaPook
    Sent: Thursday, January 30, 2014 4:24 AM
    To: francisupchurch@gmail.com
    Subject: [NavList] Re: Precomputing sextant observations at sea

     


    This is going to sound hokey. I read Chichester's book many years ago and that was where I first heard of the Bygrave slide rule, and everybody knows of my interest it now. I had felt a kinship to Chichester because I know what it is like to cross the ocean at ten thousand feet and 90 knots with only one propeller on the nose of my plane and a sextant in my hand. I was always impressed that he had managed to do this in an open cockpit biplane. In 2009 I was in England and had the chance to fly the same type of plane, a Gypsy Moth bi-plane, and I found out how difficult that type of plane is to keep under control so my admiration for Chichester went up a couple of notches. I had looked at Chichester's navigation before but I had never gone into the detail like I just did in response to Francis' question. Yesterday I used my Bygrave to repeat Chichester's computation and, there it was, the exact same values coming off my Bygrave that Chichester saw coming off of  his Bygrave on April 1, 1931 in the middle of the Tasman Sea. It really struck me, I was looking at the same reading he was looking at. It was a thrill. I told you this would sound hokey.

    gl

     

     


    From: Francis Upchurch <francisupchurch---.com>
    To: garylapook---.net
    Sent: Wednesday, January 29, 2014 7:04 AM
    Subject: [NavList] Re: Precomputing sextant observations at sea

     


    Thanks Gary,
    I knew you would get the answer! How stupid of me not to see that!( I would have missed the island and drowned!) Despite my interest in the Bygrave, I'de not thought of doing that. Just done it and got same result! Thanks!
    I'm now excited about my planned trip using the simpified pre-computed LOP/ Hp graph method you have described.
    I'll send draft plan later.
    Many thanks again for all you help and a fascinating thread on this.
    Francis
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    : http://fer3.com/arc/m2.aspx?i=126754

       
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