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Sky Report

This is the monthly Griffith Observatory Sky Report.

A telescope at the Griffith Observatory.



This is the Griffith Observatory Sky Report for the period between September 1 and September 30, 2021. Here are the events happening in the sky of southern California.

Mercury is in the evening sky. On September 1, the sun sets at 7:18 p.m., PDT, and Mercury sets at 8:15 p.m., PDT. By the 30th, the sun sets at 6:38 p.m., PDT, and Mercury sets at 7:04 p.m., PDT. Mercury reaches greatest eastern elongation on the 13th. On that date, the sun sets at 7:02 p.m., PDT, and Mercury sets at 7:58 p.m., PDT. Although Mercury then appears farthest from the sun, it sets soon after because it is in the southern part of the constellation of Virgo the Virgin and so is close to the southwest horizon. Never observe Mercury when the sun is in the sky, for the risk of damage to the eyes is great.

Venus is in the evening sky. On the 1st, the planet sets at 9:00 p.m., PDT, and on the 30th, Venus sets at 8:35 p.m., PDT. Venus offers a small disk in gibbous phase when viewed through a telescope. The planet slowly increases in size from 15 arcseconds to 19 arcseconds, while at the same time the gibbous phase slowly gets thinner, from 73 percent to 62 percent.

Mars is close to the sun and unobservable until mid-November, when it appears in the morning sky.

Jupiter rises in the east at 6:39 p.m., PDT, on the 1st and at 4:37 p.m., PDT, on the 30th, and so it will be visible all evening. A telescope will reveal features on the disk and the four Galilean moons, which travel in a rough line east to west across and behind Jupiter.

Saturn rises in the east at 5:44 p.m., PDT, on the 1st, and at 3:46 p.m., PDT on the 30th. The planet is well placed for observations in the evening sky. A telescope will reveal Saturn’s disk, its rings, and perhaps its brightest and largest moon, Titan.

Uranus rises at 10:12 p.m., PDT, on the 1st and at 8:16 p.m., PDT, on the 30th. On the 15th, Uranus is at Right Ascension 2h 47m 30s, Declination +15° 41ʹ 54ʺ. The disk of Uranus is only 3.7 arcseconds wide, and so a telescope of magnification 150x is needed to show it.

Neptune rises at 7:47 p.m., PDT, on the 1st and at 5:51 p.m., PDT, on the 30th. On the 15th, Neptune is at Right Ascension 23h 30m 28s, Declination -4° 27ʹ 48ʺ. The disk of Neptune is only 2.4 arcseconds wide, and so a telescope with a magnification of 150x is needed to show it.

New moon occurs on the 6th, first quarter on the 13th, full moon on the 20th, and last quarter on the 28th.


Autumn begins, and summer ends, when the sun reaches the autumnal equinox on September 22 at 12:21 p.m., PDT. At this moment, the sun crosses the celestial equator from north to south on its journey along the ecliptic.  The sun rises at 6:42 a.m., PDT, and sets at 6:49 p.m., PDT. The day is 12 hours seven minutes long. The days will continue to shorten, and the nights get longer, until the sun reaches the winter solstice on December 21.

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