This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, December 11. Times are given as local St. Louis time in Central Standard Time due to the time change coming this Sunday. For definitions of terminology used in the night sky update, click the highlighted text.

Information updated weekly or as needed.

Join us for our next star party, Friday, January 4, 2019 held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page.

The Sun and Moon

Sunrise is at 7:09 a.m. on Tuesday, December 11 and sunset is at 4:40 p.m. providing us with about 9.5 hours of daylight. Even after sunset, the light from the sun will still dimly illuminate our sky for about 1.5 hours. This period is called twilight, which ends around 6:15 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 11:54 a.m. this week.




11 Dec

7:09 a.m.

4:40 p.m.

12 Dec

7:09 a.m.

4:40 p.m.

13 Dec

7:10 a.m.

4:40 p.m.

14 Dec

7:11 a.m.

4:40 p.m.

15 Dec

7:12 a.m.

4:41 p.m.

16 Dec

7:12 a.m.

4:41 p.m.

17 Dec

7:13 a.m.

4:41 p.m.

18 Dec

7:13 a.m.

4:42 p.m.

19 Dec

7:14 a.m.

4:42 p.m.

for Tuesday, December 11 occurs at 9:47 a.m. and moonset will occur at 7:46 p.m. On Tuesday, December 11 the moon will be exhibiting a waxing crescent phase with roughly 12% of the lunar disk illuminated. First quarter moon occurs on December 15.

International Space Station (ISS) Observing

Visible passes of ISS from St. Louis for the week of December 11 occur during evening hours. The best of these occur on the evenings of December 12 and 13. Use the table below for information about these and other visible passes of ISS.

Catch ISS from St. Louis starting Tuesday, December 11



Max. altitude


Time Alt. Az. Time Alt. Az. Time Alt. Az.

11 Dec

-3.1 17:24:53 10 NW 17:27:54 33 NNE 17:30:39 11 E

11 Dec

-1.2 19:01:35 10 WNW 19:03:23 21 WSW 19:03:23 21 WSW

12 Dec

-2.9 18:09:02 10 WNW 18:12:12 49 SW 18:14:37 16 SSE
13 Dec -3.9 17:16:47 10 NW 17:20:02 79 NE 17:23:18 10 SE
14 Dec -0.9 18:01:41 10 W 18:04:04 19 SW 18:06:26 10 S
15 Dec -2.1 17:08:56 10 WNW 17:12:00 37 SW 17:15:01 10 SSE

Magnitude (Mag): The Measure of brightness for a celestial object. The lower the value is, the brighter the object will be.

Altitude (Alt): The angle of a celestial object measured upwards from the observer’s horizon.

Azimuth (Az): The direction of a celestial object, measured clockwise from an observer’s location with north being 0°, east being 90°, south being 180° and west being 270°.

For information about ISS flyovers and other visible satellites, visit

Detailed information regarding all unmanned exploration of our universe, missions past, present, and planned, can be found at Jet Propulsion Laboratories:

The Planets Visible Without a Telescope

This week three of the naked eye planets are visible, Venus has started a morning apparition rising before the sun, Saturn is in the southwest after sunset and Mars will be seen shortly after sunset in the south.


Venus has started another morning apparition. You can find the brightest planet rising in the east by 3:30 a.m. By 4:00 a.m. should be high enough to clear trees and buildings. Venus will spend the first half of 2019 as an early morning target


The red planet can be found in the south as the sun sets. With opposition having come and gone the bright appearance of Mars will begin to fade. Mars will set by 11:29 p.m.


Saturn has been visible in the southern sky for some time, but the angle of the summertime ecliptic has kept the ringed planet low in the southern sky. Saturn has now shifted to the southwestern sky and will only be visible for about an hour after sunset. Saturn sets at 5:58 p.m.

Our next Star Party will be held on Friday, January 4, 2019, from dusk until 10 p.m.

As part of the Saint Louis Science Center’s First Fridays, weather permitting, the St. Louis Astronomical Society and the Science Center will set up a number of telescopes outdoors and be on-hand to answer your questions. Telescope viewing begins once it is dark. Regardless of the weather on January 4, join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m.

This free, indoor star program will introduce you to the current night sky, the planets, and the seasonal constellations. Doors open 15 minutes before show time. Shows begins at 7 p.m. Sorry, no late admissions due to safety issues in the darkened theater.

The St. Louis Astronomical Society helps host the monthly Star Parties at the Saint Louis Science Center which are held on the first Friday of each month. Our Monthly Star Parties are open to the public and free of charge. Telescope viewing is scheduled to start around 7:00 p.m.