A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter B
Date: 2017 Mar 2, 19:33 -0800
I have been rummaging through my nav books and discoverd that there are a number of versions of Dreisonstock's H.O. 208 tables even within the same editions.
I have two edition 5's. One printed in 1935, the other in 1940. In the 1935 version the Table 2 (d+b) values are not labeled for angles greater than 90 degrees, while in the 1940 version (same edition, mind you) the angles extend from 89 degrees up to 180 degrees by listing across the bottom of the columns. Table 1 in both editions stops at 65 degrees latitude and 90 degrees meridian angle.
Neither 5th edition lists angles greater than 90 degrees for Table 1, so you must learn a few rules to convert LHA's from 90 to 360 into a meridian angle reckoned either from your meridian or a meridian 180 degrees away from you.
Meanwhile in Letcher's "Self Contained Celestail Navigation" he includes a version of H.O. 208 6th edition that lists all LHA's up to 360 by simply adding more headers above the columns. The trig values repeat after all. (BTW this change significantly changes the instructions.) Also he includes a supplemantal Table 1a that extends usefulness to all latitudes. This Table 1a appears at casual inspection to be mathematically exactly the same as the Table 1, just extended for degrees of lat from 66 up to 90.
Then I discovered a used book lisitng for a used Edition 2 that claims to be "...for all latitudes"
But wait.... my two ed 5's do not handle all latitudes, only latitudes to 65 degrees. Is the seller mistaken or am I? Was there/ is there another "enhanced" version of each edition that includes Table 1a? Perhaps if you paid 50 cents more you got Table 1a?
My question is just how many versions of each edition existed? I am not sure this is an easy question to answer as my research at The United States Library of Congress doesn't even differentiate between the two clearly different edition 5's that I own.
As far as I can tell the significant differences would be:
If a version had a "Table 1a" for latitudes from 66 to 90 degrees
and/or if a version had listings at the bottom of the columns of Table 2 for angles greater than 90 degrees
and/or if an version had headers and footers on Table 1 for degrees greater than 90 degrees.
Now I use "version" instead of "edition" because the editions cannot be relied upon to be all alike. My two edition 5's are different, so there are at least two versions of edition 5. And possibly there are up to two more versions of edition 5 that may have included Table 1a.
My first encounter with these tables was a happy one: I found them easy to use. Later, having acquired a couple of more versions, I can see how their use could be far more confounding... depending on the version you got a hold of.
Sorting out Table 1 which does not extend past 90 degrees is not that difficult. Perhaps a bit confusing at first, but not overly taxing in the end.
The edition 5 (and presumably earlier editions) with no angles past 90 in Table 2 is particularly challenging if you are not mathematically inclined, and not helped in the least by the incorrect instruction as to how to handle a (d+b) value greater than 90. The instructions say to take 180 - (d+b) and use that to find the correct column... but that instruction is wrong. You take 179 - (d+b) because each column has increments to 60 arc-minutes that make up the rest of the remaining degree. You also must reverse the arc-minutes to read form 60 at the top to 0 at the bottom for this to work which is not metioned at all in the instructions. If you were not holding the other versions in your hands you would likely be misled by those incorrect instructions.
So my thread has a point: What versions do you have? What dates and editions? Do you have Table 1a for latitude from 66 to 90 degrees? Do you have angles from 90 to 180 across the bottom of Table 2 ? Do you have additional angles across the top and bottom of Table 1 or does it stop at 90?
I was amazed that these tables were not a lot more popular, but it seems like I got lucky the first time and had a pretty good version. (ed 5 1940 printing with Table 2 up to 180; Table 1 up to 90; and Lat to 65.) If you had one of the less good versions they would be frustrating...and yet the numbers are all in there in each of them. You just need to label the columns correctly.