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    Re: Dennert & Pape MHR-1 Dennert & Pape MHR-1 HR-2 Cylindrical Slide LineRuler
    From: Wolfgang Hasper
    Date: 2013 Jan 30, 20:54 +0100

    Gary,
    thaks for poining me once more to your paper.
    I did not realise how completely you have described 
    ways around all conceivable special cases.
    Great!
    I will prepare an additional label for the outer tube 
    in the MHR1 style to have your rules always at hand.
    
    Best
    Wolfgang
    
    Am Montag, 28. Januar 2013 00:38 schrieb Gary LaPook:
    > Do you have any actual instructions for using your
    > MHR-1 for dealing with the special case when the
    > declination is less than the lowest� declination
    > marked on the tangent (or co-tangent) scale, 20' for
    > the Bygrave and 30' for the MHR-1 and 50' on my flat
    > Bygrave? I have never been able to find instructions
    > for this situation. I am attaching a description for
    > the use of this instrument (in French) which says it
    > is "inutilisable" for this situation and the
    > original Bygrave instruction manual is silent as to
    > this situation, also attached.
    >
    > I came up with a method of dealing with this
    > situation and it is posted on my website at:
    > https://sites.google.com/site/fredienoonan/other-fli
    >ght-navigation-information/modern-bygrave-slide-rule
    >
    > (In my notation "W" is the same as "y" in Bygrave's
    > notation and "x" on the MHR-1.)
    >
    > "When declination is less than one degree you can't
    > begin the computation the normal way to find "W"
    > because you have to start the process with
    > declination on the cotangent scale and this scale
    > doesn't extend below 1�. So in this case you just
    > skip the computation of "W" and simply set "W" equal
    > to declination. Using this method you arrive at an
    > azimuth that is not exact but is a close
    > approximation and in the worst case I have found the
    > azimuth is still within 0.9� of the true azimuth but
    > most are much closer. If the declination is less
    > than one degree and the latitude is also less than
    > one degree, follow this procedure and also assume a
    > latitude equal to one degree. After you have
    > computed the Az you then follow the same procedure
    > discussed above for azimuths exceeding 85� by
    > interchanging the latitude and declination and then
    > computing Hc which will produce an exact value of
    > Hc."
    >
    > Also see my prior post at:
    >
    >
    > http://fer3.com/arc/m2.aspx/Computing-azimuth-with-B
    >ygrave-special-cases-LaPook-feb-2010-g11826
    >
    > gl
    >
    >
    >
    > --- On Sun, 1/20/13, Marc Giordan
    >  wrote:
    >
    > From: Marc Giordan 
    > Subject: [NavList 22013] Re: Dennert & Pape MHR-1
    > Dennert & Pape MHR-1 HR-2 Cylindrical Slide
    > LineRuler To: garylapook---net
    > Date: Sunday, January 20, 2013, 11:08 AM
    >
    > Sir,
    > I am French and also quite familiar with the use of
    > the MHR 1 at sea (I used it for 2 atlantic crossings
    > by sail) Would any one wish to be trained in using
    > it, I am ready to help ! The MHR 1 was bought by my
    > father some 30 years ago at the flee market in Paris
    > Yours
    > Marc Giordan
    > 26 rue de Paris
    > 78560 le Port Marly
    > (0033)675210703
    > ----------------------------------------------------
    >------------ NavList message boards and member
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    >
    > View and reply to this message:
    > http://fer3.com/arc/m2.aspx?i=122013
    >
    >
    > Attached File: http://fer3.com/arc/img/122138.calcul
    > de navigation, v2 (courante).pdf
    >
    > Attached File:
    > http://fer3.com/arc/img/122138.bygrave manual.pdf
    >
    >
    > View and reply to this message:
    > http://fer3.com/arc/m2.aspx?i=122138
    
    
    
    

       
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