NavList:

   

Reply

With the Altrincham position provided by DaveP (53 23 N 002 21 W), I
agree with others who calculated Sun altitude -16° at 1898 April 3 2040
UT. The cyclist did well to talk his way out trouble for riding without
a light near the end of astronomical twilight. (A gibbous Moon was 40°
high in the SSE.)

Almost 20 years later, the 1917 July issue notes the introduction of
rise and set tables in the 1917 American Ephemeris supplement, and
expresses surprise that these data have "hitherto been left to
unofficial publications such as Whitaker's Almanac and our Companion
[the magazine's annual supplement]."


https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1917Obs....40..276.&db_key=AST&page_ind=3&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES

In addition to two letters in reply to that article, there are a two
articles on the proposed change in the commencement of the astronomical
day. When the change occurred at the beginning of 1925, the Julian date
(integer part) continued to increment at Greenwich noon as before. Thus,
the objection that the new GMT would cause a JD discontinuity was avoided.

Observatory 1917 index

https://ui.adsabs.harvard.edu/search/q=bibstem%3AObs%20year%3A1917&sort=date%20desc%2C%20bibcode%20desc&p_=0


In the field of aviation, this Avweb article says the US Federal
Aviation Regulations have different "night" definitions for turning on
position lights, logging flight time, and carrying passengers:

https://www.avweb.com/flight-safety/faa-regs/wheres-it-say-that/

--
Paul Hirose
sofajpl.com

   

Reply