If March equinox is on 20th March (see the table in the link), according to it, when is the time that the sun enters Taurus? Is it on April 19 or April 20?
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2$\begingroup$ And from Guide9, about 18.00 UT on 13 May is when its leading edge hits the boundary between Aries and Taurus - at least for the astronomical constellations. $\endgroup$– Dr ChuckCommented Apr 9, 2020 at 19:16
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6$\begingroup$ I'm voting to close this question as off-topic because astrology $\endgroup$– James KCommented Apr 9, 2020 at 21:08
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2$\begingroup$ @James K What astrology in that? It is pure astronomy! It is the second time you call my question astrology while I'm interested in astrology at all, but I'm interested in the history of the astronomy. $\endgroup$– Reckless GlacierCommented Apr 9, 2020 at 21:36
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2$\begingroup$ James K has a point, the Sun's λ=30° date is of little interest outside astrology. If there's an astronomical purpose, you need to show what it is, not just claim that there is one. $\endgroup$– Mike GCommented Apr 9, 2020 at 22:21
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2$\begingroup$ My purpose is to understand the differences between the 'previous' astronomy to the current one. Data of astronomy out of date is still astronomy and still studied in astronomy departments at any respected university. $\endgroup$– Reckless GlacierCommented Apr 9, 2020 at 22:31
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1 Answer
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Guy Ottewell makes a comprehensive Astronomical Calendar each year. From the 2020 edition:
8959.117 Apr 19 SUN 15 Sun enters the astrological sign Taurus, i.e. its
longitude is 30°
That's 2020-04-19 ~15h UT, which falls on April 20 in far eastern terrestrial longitudes and April 19 everywhere else. The next such event is 1 tropical year (365d 5h 49m) later.
8983.315 May 13 Wed 20 Sun enters Taurus, at longitude 53.48° on the eclip-
tic
The Sun enters the constellation at 2020-05-13 ~20h UT, which falls on May 14 in Asia, Australia, etc., and May 13 everywhere else. This event recurs 1 sidereal year (365d 6h 9m) later. In that time, the ecliptic longitude of the constellation boundary increases by 0.014°.
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+1There's that word again! So, what, exactly, is a tropical period? $\endgroup$– uhohCommented Apr 9, 2020 at 22:41 -
$\begingroup$ Well, I see that not only I confused... According to this table is on "April 20, 2019: Sun enters sign Taurus (30°)" - earthsky.org/human-world/suns-entry-into-each-sign $\endgroup$ Commented Apr 9, 2020 at 23:34
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1$\begingroup$ That was 2019. Ottewell's calendar for that year lists the event at 2019-04-20 9h UT. Feb 2020 had a leap day, so the Apr 2020 event occurs 18 hours earlier instead of 6 hours later. $\endgroup$– Mike GCommented Apr 9, 2020 at 23:48
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$\begingroup$ Thank you very much. You answered my question. $\endgroup$ Commented Apr 10, 2020 at 0:03
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2$\begingroup$ Another reference: abc2home.ru/znaki_zodiaka/constellations/… $\endgroup$ Commented Apr 10, 2020 at 3:11