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With the exception of the red numbers on the outside rings, your MB-2A
computer looks remarkably similar to the Jeppesen CR series (CR-3,
CR-6, etc.) - is it maybe a military version (or an earlier version)of
the Jepp one?

And I assume this isn't the other calculator that you alluded to
earlier (Barger, or something similar?) - it's late and I can't find
that particular post right now.

--
GregR




--- "Gary J. LaPook"  wrote:

> Gary J. LaPook wrote:
> 
> > Being the conscientious navigator that I am, I followed my usual 
> > practice of memorizing some data from the 2008 Nautical Almanac so 
> > that I would have it available for emergency use.
> >
> > The first thing I memorized was the GHA of Aires at 0000 Z January
> 1, 
> > 2008 which is 100� 01.9' and also remembering that Aires advances 
> > 59.139' each day. With this information you can calculate GHA Aires
> 
> > for 0000 Z on June 9, 2008 which is the 161st day of the year but
> is 
> > only 160 days from January 1st. So multiplying 59.139' times 160
> days 
> > gives  157� 42.2'  to which you add the starting value of 100�
> 01.9' 
> > to come up with the GHA Aires on June 9th at 0000 Z of  257� 44.1'.
> To 
> > this you add the change of GHA for the time since 0000 Z (3 hours
> 42 
> > minutes 10 seconds for the Vega shot) by multiplying the time
> interval 
> > by the rate of change of 15.041� per hour making 55� 41.6' making
> the 
> > GHA Aires at the time of the Vega shot of 313 � 25.7'.
> >
> > I also memorized the SHAs and the Declinations of ten of the 
> > navigation stars ( nobody could memorize all 57) which should be 
> > enough for emergency use as tabulated for July 1st so that the
> values 
> > will be reasonable for the whole year. Fortunately this included
> the 
> > three stars used in this exercise. So now adding the SHA of Vega,
> 80�  
> > 41' we end up with the GHA of Vega of 34� 06.7' and using the D.R.
> as 
> > the A.P. we get an LHA of 274� 48' and the declination of 38� 47'
> N. 
> > (rounded to the whole minute)
> >
> > Using these values on my Bygrave slide rule (see attached work
> sheet) 
> > since I have no tables with me, I computed Hc of 23� 59'.
> >
> > The Hs given was 24� 05.5' Computing the dip correction in my head
> of 
> > 4.5' (the square root of 20 must be between 4 and 5 ) and applying
> the 
> > refraction correction of minus 2 gives an Ho of 23� 59' giving and 
> > intercept of zero and an azimuth of  58.1 �.  I long ago memorized
> the 
> > refraction table for altitudes above 10� in The Air Almanac and in
> H.O 
> > 249, the cutoff values are 63-33-21-16-12-10� , zero above 63, 1
> above 
> > 33, 2 above 21, 3 above 16, 4 above 12 and 5 above 10.
> >
> > I used the same procedure for Spica and Pollux getting another zero
> 
> > intercept for Pollux, Zn of 290.2� and a  4 NM away for Spica with
> a 
> > Zn of 171.7�.
> >
> > Since I am on the road I do not have any of my plotting tools with
> me 
> > so I had to make do with what I found in my briefcase. I used my
> MB-2A 
> > flight computer since it had an azimuth scale and I used a pad of 
> > paper  with a right angle at the corner as my straight edge for 
> > plotting the LOPs. I used a tape measure from IKEA to measure the 
> > length of the intercept (see photo.)  I plotted the LOPs and found
> the 
> > fix by bisecting the three angles giving a fix .4 NM west of the
> A.P. 
> > (D.R.) and 2.8 NM north of it. (Plotting a fix as a distance from
> the 
> > A.P. like this is common in aerial practice and it is often done on
> an 
> > E-6B.) Adding the 2.8 NM north to the D.R. latitude gives a fix 
> > latitude of 34� 16' North. To convert the .4 NM west  to a
> longitude 
> > you divide the .4 NM by the cosine of the latitude, .82, to find
> the 
> > difference in longitude of  .5' so the fix longitude is 119� 19.5' 
> > West (rounded to either 119� 19' or 20'.)  ( I got the cosine of
> 34� 
> > by finding the sine of 56� on the MB-2A sine scale, used for wind 
> > correction calculations.)
> >
> > My fix might not be in agreement with others but I used a
> refraction 
> > table tabulated in whole minutes, I only memorized the stars' 
> > positions to the nearest minute and I did not have any plotting
> tools 
> > to use but my position is certainly good enough for emergency 
> > navigation and done without an almanac, tables or electrons.
> >
> > gl
> > 1
> >
> > m_burkes@msn.com wrote:
> >
> >>Captain Lecky would be proud of those dividers ha! Speaking of
> >>interpolation I have found a neat way to get around that pesky DSD
> and
> >>interpolation tables by using the aviation E6B computer or the
> >>equivalent nautical slide rule. Essentially the set
> up:d-value/60=d-
> >>correction/declination minutes. Yes the calculator offers the
> proof.
> >>Mike Burkes
> >>On Jun 12, 11:44 pm, Anabasi...@aol.com wrote:
> >>  
> >>
> >>>Thanks for the nice exercise Greg.  I literally had to dust off
> the  ship's
> >>>Vol III of HO 229 and deflower a Plotting sheet 925 to work this
> one  out.
> >>>
> >>>Since I was bereft of electronic gadgets, I did this with a
> plotting sheet,  
> >>>2 triangles, a pair of dividers, 2 books, a pencil, and small
> piece of scratch
> >>> paper (wouldn't have reams of paper in the Lifeboat).  I have
> attached a  
> >>>picture in to this message with the plot and the tools.
> >>>
> >>>My Lat is a bit lower (plotting or math error?).  I used an
> assumed  position
> >>>method and HO 229.  I had to assume we were drifting and no 
> current (didn't
> >>>advance or retard the lines).  I had not done a full HO 229  paper
> reduction
> >>>of a star in many years, and I had to think a second to remember 
> how to use
> >>>the interpolation pages on the inside covers for the declination 
> interpolation.
> >>> I usually whip those off with the calculator.  Still,  I got
> pretty close to
> >>>the computer solutions with Lat 34deg 11.9' N and  Longitude
> 119deg 16.0'W.
> >>>
> >>>As to how you would get an Eastern sight on the west coast, you
> would have  2
> >>>options in general.  The first would be a back sight.  This would
> be  
> >>>particularly difficult with a regular sextant at such a low
> altitude.  The  other
> >>>option would be to use a bubble sight tube or other artificial 
> horizon.  If you
> >>>were across a bay, you could also use a dip short of  the horizon
> table.  
> >>>That's all I can think of at the moment.
> >>>
> >>>Jeremy
> >>>
> >>>**************Vote for your city's best dining and nightlife.
> City's Best
> >>>2008.      (http://citysbest.aol.com?ncid=aolacg00050000000102)
> >>>
> >>> gregExerPlot.jpg.JPG
> >>>182KViewDownload
> >>>
> >>> GregExerTools.jpg.JPG
> >>>129KViewDownload
> >>>    
> >>>
> >>
> >>
> >>  
> >>
> >
> >
> > >
> 
> 
> > 
> 


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