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On 2019-06-21 19:31, I wrote:
> "There can be little doubt as to the usefulness of the tables of rising
> and setting of the Sun and Moon, lately published as a supplement to the
> American Ephemeris... From the figures in these tables it appears that
> sunset is defined as the instant when the upper limb is on the visible
> horizon. This, therefore, implies that sunset does not happen until the
> whole of the disc has disappeared, and it might be expected by parity of
> reason, that sunrise should not happen until the whole of the disc has
> reappeared, but in these tables, on the contrary, the times given are
> again those when the upper limb is on the visible horizon. By defining
> sunset or sunrise as the instant when the centre of the disc is on the
> visible horizon, as is done in your 'Companion,' any inconsistency of
> this kind is avoided."
>
> 
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1917Obs....40..345H&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES

I located a 1916 edition of the "Companion" to which the writer refers.
The sunrise and sunset table is on page 2:


http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1916Obs....39....1.&db_key=AST&page_ind=1&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES

Evidently the table is valid for one latitude, which isn't stated. Nor
are we informed of its definition of rise and set. I guessed latitude
51.5 (London, in round numbers). That seems consistent with the table,
if rise and set are the instants when the zenith distance of the Sun
center is about 90°35′.

   

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