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The Night Sky in July

Nature volume 141, page 1135 (25 June 1938) | Download Citation

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THE moon is full on July 12d 15·1h and new on July 27d 03·9h U.T. The only bright star to be occulted jihis month is λ Piscium, the reappearance of which will be visible from Greenwich on July 18 at 2h 22·4m, at position angle 198° from the north point of the moon's image. Lunar conjunctions with the planets occur as follows: with Jupiter on July 16d 7h ; with Saturn on July 20d Oh ; with Mercury on July 29d 5h ; and with Venus on July 30d 9h. On July 26, Mercury is near Regulus, the minimum apparent separation (geocentric) being 0-9° ; and on July 31d 7h Mercury is in conjunction with Neptune, the separation being 0·4°. Venus is a bright evening star, setting about lh 40m after the sun in mid·July. Jupiter and Saturn are both visible during the night, Jupiter, a very bright object, southing about 2½h in the middle of the month and Saturn three hours later. The interesting phenomena (eclipses, transits, occul-tations) of the Jovian four inner satellites may be followed with the help of the table and diagram given on p. 613 of the Nautical Almanac for 1938 or of the table on p. 170 of Whitaker's Almanack. At 22h in mid-July, Vega is nearing the southern meridian and precedes the Milky Way. The bright star Deneb (α Cygni) on the galactic equator marks the apex of the bifurcation of the Milky Way, one branch passing southwards through Serpens and Scorpio ; the other through Aquila, Scutum and Sagittarius. Interesting objects for telescopic examination abound in this region, which is also the habitat of the novæ. The 6th magnitude double-star, 61 Cygni, was the first star to have its distance successfully measured one hundred years ago by Bessel, who made his measures with a heliometer. His results gave the star's distance as 640,000 times that of the earth-sun distance ; modern measures give 680,000 times this unit.

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https://doi.org/10.1038/1411135e0

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