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Message 5457.

gl

On Aug 18, 3:31�pm, "Greg R."  wrote:
> --- "Gary J. LaPook"  wrote:
>
> > BTW, did you ever check my work?
>
> I posted the solution to that one in [NavList 5428]: "GPS position for
> that series of sights is 34�14.4�N / 119�15.9�W, and my Navigator
> computer program calculates 34�12.6'N / 119�16.5'W (using APs of 34�N
> and W longitudes to give a whole number of LHA)".
>
> Or, if you'd like to me take a look at the (creative) method you used
> to solve it post a message # and I'll take a look at it.
>
> --
> GregR
>
> --- "Gary J. LaPook"  wrote:
>
> > BTW, did you ever check my work?
>
> > gl
>
> > Greg R. wrote:
>
> > Assuming you're not being tongue-in-cheek with your solution (and
> > being
> > at work I can't verify it right now), regardless of accuracy you
> > definitely get the Most Unique Solution award (plus an honorary
> > Navigator Who I'd Most Want To be Shipwrecked With plaque, with gold
> > clusters). �:-)
>
> > >Heh... I almost wrote the exercise with all of the navigation books
> > >being lost overboard too, and luckily the intrepid navigator had
> > >memorized their entire contents - but figured that was a bit too
> > much
> > >of a stretch. Now I may have to re-consider that option... �;-)
>
> > >Assuming you're not being tongue-in-cheek with your solution (and
> > being
> > >at work I can't verify it right now), regardless of accuracy you
> > >definitely get the Most Unique Solution award (plus an honorary
> > >Navigator Who I'd Most Want To be Shipwrecked With plaque, with gold
> > >clusters). �:-)
>
> > >--
> > >GregR
>
> > >--- "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.
>
> > >>(I will have to send the images when Ii figure out how to make them
>
> > >>smaller.)
>
> > >>gl
> > >>1
>
> > >>m_bur...@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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