Using HP-65 Sunrise/Sunset

[Geoff Quickfall]

Yes, unlike recessive and dominant genes there appears to be no acccepted standard. My 71b, prog use the input

1. Naabb.c
2. Saabb.c
3. Eaabb.c
4. Waabb.c
   

The programs then test for the alpha character N, S, E and W and assign the sign automatically with North and West +ve and South and East -ve. My other calculators, for ease of input require the signs.

Although this is not a convention, it is how the formula I have used, as published in the FAA documentation accept the differentiation. Of course this is using the equator as 0 latitude and the longitude increasing to 180 leaving Greenwich heading west until the dateline the decreasing heading west back to 0 at Greenwich.

Here is how a ships officer would assign the sign:

Great circle sailing

So I think it is how you are instructed to use the formula and that is based on the formula and its internal conventio/construction. The formula I first used was out of the HP 25 handbook. Subsequently I have used this formula and found the same in aviation handbooks.

Interestingly, the on board navigation computer (FMC) when heading west from Vancouver, over the dateline displays the dateline as W180 00.0. And when heading east from Asia displays the dateline as E180 00.0.

Geoff

P.s. Sliderule: should second yellow line be (W. positive: E. negative) and by the way, this is the formulae convention HP has used throughout its calculator manuals, not just the 67.