NavList:

David P, you wrote:
"So why does the NA write 0°.2724?  If you read from the start of the section, the Direct Method appears to be aimed at the non-expert computer user working with an early spreadsheet or programmable calculator"

Yes. And just to reiterate something I said a couple of weeks ago, this entire section on direct computation was written over thirty years ago and hasn't changed one dot since then. The typographic choice itself, placing the degree symbol directly over the decimal, was a common though already somewhat quaint choice back then, but today? I'm not sure there's even a means to achieve in it ordinary unicode text [I know... there's always a way... but let's call it extra-ordinary]. It just doesn't fit. The degree symbol should not be present.

"I’m speculating, but I think 0°.2724 is meant to be read.  If you intend to use SD=0.2724HP in your computer calculation, make sure that at some stage you convert the value of SD to decimal degrees if that’s the unit your using for all your other variables. "

I agree. That was probably the line of thought, and it's what they spell out: convert HP to degrees first by dividing 60. This could have been done better in several ways. For example, since the almanac pages only list the HP in minutes of arc (and yes, this is absolutely standard), then load the 60 directly into the formula. In fact, it comes out rather cleanly:
  SD = 0.00454HP,
or, even better (?):
  SD = HP / 220.
which yields the SD in degrees (consistent with the rest of the explanation) for an input of HP in minutes of arc, direct from the pages.

Like I say, this is a really minor concern, and I'm spelling things out primarily for folks who may want to teach direct calculation of Moon sights and who may have students puzzled by that little degree symbol floating in that 0.2724. It's not an angle. It's the ratio of the Moon's diameter to the Earth's equatorial diameter (previously I said "mean" but no it's "equatorial" since that's how the HP is define). You can try it out. The Moon's diameter is 3475km. The Earth's equatorial diameter is 12756km. Divide the first by the latter, and you get 0.2724. And that's that.

Here's a thought: The article in the N.A. is kind enough to mention the small oblateness correction, identified as "OB", which can amount to a few tenths of a minute of arc. The article does not, however, mention the augmentation of the Moon's SD which is comparable in magnitude. Is that an oversight? Or is it picked up elsewhere in the calculations?? :) Again, for the purposes of a "minute of arc" level of precision, neither matter. But is omitting one correction justified and not ther other??

Frank Reed