# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Computation anomaly in standard tables.**

**From:**Gary LaPook

**Date:**2014 Jul 7, 00:49 -0700

Several years ago, when I was working out sample problems on my Bygrave, I used a combination of latitude, declination and LHA (all whole degrees) that produced a computed altitude that was also a whole number of degrees, no minutes. I found this combination entirely by chance and I don't remember what those values were. Today I decided to find a similar combination so I pulled out a volume of H.O. 216 and started scanning the pages for latitude 34° (looking at only the columns for whole degrees of declination since H.O. 216 has columns for half degrees of declination.) for all declinations from zero through 24°. This search examined 25 columns, each with LHAs from zero through ninety, a total of 2,250 (90 X 25 since I excluded the line for
zero degrees of LHA since those always produce whole number of degrees of Hc.) Since there a possible 600 combinations of minutes of Hc, 00.0' through 59.9', I expected to find about 4 such combinations, I found only one. Latitude 34°, declination 19° same name and LHA 9° produced an Hc of 73° 00'.

I then decided to expand my search so I pulled out H.O. 229 and looked at the pages for LHAs of 9°, 30° and 44° and latitudes 30° through 37° (same name), a total of 2,160 (again excluding the line for declination 90° which always produces whole number of degree Hcs.) Each page has 720 values so should have had at least one example per page so I had expected 3 or 4
examples and found exactly none. Even the Hc for the latitude 34°, declination 19°LHA 9° that produced a whole number Hc in H.O. 216 now produced 72° 59.7'.

I find it curious that I did not find the values I was expecting to find. Perhaps you math and/or computer programing wizards can explain this anomaly.

gl