NavList:

Bowditch table 29 from the 1982 edition is still a good way to get an ex-meridian correction if within 7* of LHA. The table covers 60* of latitude and 63* of declination. My preferred method is to figure the altitude factor (a) by table 29 (5 pages) then complete using a calculator or slide rule and formula .267(a)(LHA^2).

Greg Rudzinski

[NavList] Re: Ex-Meridian Tables....Hansen vs. Norie's
From: Greg Rudzinski
Date: 24 Dec 2012 13:29
Doug,

Hansen's Improved Ex-meridian Tables 1964 reprint of 1954 edition is a small 4" x 6" 117 page set of tables spanning 60* of latitude and 30* of declination which will cover the Sun, Moon, and the majority of navigational stars. Working the Key table and primary table is done with visual interpolation making it quite fast to get the XM correction. Less than 30 seconds of time once LHA, latitude , and declination are figured from the DR and Nautical Almanac. LHA coverage is 15* either side of MP. No complaints here.

Greg Rudzinski

[NavList] Ex-Meridian Tables....Hansen vs. Norie's
From: Doug MacPherson
Date: 24 Dec 2012 13:02
Having just obtained 1915 copy of Hansen's, I have been playing around with simulated Ex-Meridian's using stars at civil twilight......set my Weems & plant Star Finder to the correct settings, and read off any stars that are within 10 to 15 degrees of 180 or 0 degrees. Compute simulated Hc etc. with online tool.

I have noticed that I keep reaching the tables in Norie's because:

1. the stars declination is out of range for Hansen.
2. the star is at lower transit, Hansen does not appear to have a way of dealing with lower transits...(by the way make sure to subtact the "reduction"...learned that one the hard way).

Norie's appears to be superior in a number of area's....Declination from 0 t0 63 degrees. Latitude from 0 to 83 degrees. Hour angles to 16 degrees (a little over one hour on either side of the meridian) with more available with table 3. Only takes up 16 pages.

Hansen's: 0 to 30 declination, 0 to 60 lat, about one hour on either side of the meridian, 171 pages.

My copy of Norie's is from 1991.

Hansen's appears to have been primarily for the sun...yes? with declination centered from 0 to 23.

Was Norie's developed later and represent an improvement?

Thought?

Have a great Holiday.

Doug
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