This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, January 23. All times are given as local St. Louis time (Central Standard Time). 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, February 2, 2018 held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page.

The Sun and the Moon
Sunrise is at 6:42 a.m. on Tuesday, November 14 and sunset is at 4:48 p.m. providing us with a little over 10 hours of daylight. Even after sunset, the light from the sun will still dimly illuminate our sky for a bit less than 1.5 hours. This period of time is called twilight, which ends around 6:20 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 11:46 a.m. this week.




23 Jan

7:13 a.m.

5:13 p.m.

24 Jan

7:13 a.m.

5:14 p.m.

25 Jan

7:12 a.m.

5:15 p.m.

26 Jan

7:11 a.m.

5:16 p.m.

27 Jan

7:11 a.m.

5:17 p.m.

28 Jan

7:10 a.m.

5:18 p.m.

29 Jan

7:09 a.m.

5:19 p.m.

30 Jan

7:08 a.m.

5:20 p.m.

31 Jan

7:07 a.m.

5:21 p.m.

Moonrise for Tuesday, January 23 occurs at 10:56 a.m. and moonset will occur at 11:45 p.m. On Tuesday, January 23 the moon will be exhibiting a waxing crescent phase with about 38% of lunar disk illuminated. First quarter moon occurs on January 24.

January 31 blue moon and total lunar eclipse
In the early morning hours on January 31 the Moon will exhibit its full phase for the second time this month giving us a blue moon. The original definition of the term blue moon stated that a blue moon occurs when there are four full moons in one season. In this scenario the third full moon was the blue moon. A newer second definition for blue moon was created due to someone interpreted the first definition incorrectly. The newer definition states that if there are two full moons in one month the second one is the blue moon. This is the kind of blue moon that will occur on January 31.

Also of note since January 31 is the next full moon there will not be a full moon in the month of February. This last happened in 1999 and occurs roughly every 18.6 years.

In addition to this month having a blue moon, it will also have the first total lunar eclipse visible from St. Louis in two years. Unfortunately the eclipse begins shortly before the Moon sets for us in St. Louis. If you would like to observe this lunar eclipse you will need to find an observing location with a clear western horizon. The lunar eclipse will start at 4:41 a.m. as the Moon begins to pass through the outer part of Earth’s shadow. At 5:48 a.m. the Moon will start to pass through Earth’s umbral shadow and totality will start at 6:51 a.m. At this point the Moon will only be 2.2° above the horizon. For times and more information visit:

International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of January 23 occur in the evening hours. The best of these occur on the evenings of January 25, 26 and 28. Use the table below for information about these and other visible passes of ISS this week.

Catch ISS flying over St. Louis starting Tuesday, January 23.



Max. altitude


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

23 Jan

-2.3 19:00:54 10 SSW 19:02:47 28 S 19:02:47 28 S

24 Jan

-2.3 18:09:05 10 S 18:11:38 21 SE 18:12:53 17 E

24 Jan

-0.6 19:44:53 10 WSW 19:45:33 15 W 19:45:33 15 W

25 Jan

-3.7 18:53:43 10 WSW 18:56:57 68 NW 18:57:05 66 NNW

26 Jan

-3.7 18:01:27 10 SW 18:04:39 58 SE 18:07:12 15 ENE

26 Jan

-0.8 19:38:53 10 WNW 19:39:52 15 WNW 19:39:52 15 WNW

27 Jan

-2.3 18:45:56 10 W 18:48:51 30 NNW 18:49:54 24 N

28 Jan

-3.2 17:53:13 10 WSW 17:56:25 53 NW 17:59:38 10 NE

29 Jan

-1.5 18:38:36 10 WNW 18:40:51 17 NNW 18:42:24 13 N

30 Jan

-2.1 17:45:30 10 W 17:48:17 25 NNW 17:51:05 10 NNE

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


The red planet has started another apparition and can be found rising in the east by 2:37 a.m. Mars will be visible low in the east around 3:30 a.m. Each week Mars will rise a little earlier than the week before as we approach the 2018 Mars opposition which occurs on July 27.

If you want to start preparing for the upcoming 2018 Mars opposition follow the link.


The second planet from the sun can be found in the morning just before sunrise. Venus rises around 5:35 which is about an hour before sunrise. As bright as Venus is you should still be able to see it about 30 minutes before sunrise but be careful as you don’t want to accidentally look at the Sun. Start looking for Venus low in the east around 6:00 a.m.


The king of the planets can be found rising by 1:57 a.m. but can be easily seen by 3:00 a.m. low in the east. Jupiter will slowly elongate away from the Sun reaching opposition on May 8, 2018.


Saturn has been slowly climbing out of the Sun’s glare for some time now however the angle of the ecliptic in the early morning has kept the ringed planet low in the twilight soup. Saturn is now rising by 5:23 a.m. and will be an easy target by 6:00 a.m.

Our next Star Party will be held on Friday, February 2, 2018, 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 February 2, 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.