This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, February 20, 2018. 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, March 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 6:45 a.m. on Tuesday, February 20 and sunset is at 5:44 p.m. providing us with roughly 11 hours of daylight. Even after sunset, the light from the sun will still dimly illuminate our sky for about 1.5 hours. This period of time is called twilight, which ends around 7:13 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 12:15 a.m. this week.




20 Feb

6:45 a.m.

5:44 p.m.

21 Feb

6:44 a.m.

5:46 p.m.

22 Feb

6:43 a.m.

5:47 p.m.

23 Feb

6:42 a.m.

5:48 p.m.

24 Feb

6:40 a.m.

5:49 p.m.

25 Feb

6:39 a.m.

5:50 p.m.

26 Feb

6:37 a.m.

5:51 p.m.

27 Feb

6:36 a.m.

5:52 p.m.

28 Feb

6:35 a.m.

5:53 p.m.

Moonrise for Tuesday, February 20 occurs at 9:31 a.m. and moonset will occur at 10:42 p.m. On Tuesday, February 20 the moon will be exhibiting a waxing crescent phase with about 23% of lunar disk illuminated. First quarter moon occurs on February 23.

International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of February 20 occur in the morning hours. The best of these occurs on the morning of February 28. Use the table below for information about this and other visible passes of ISS this week.

Catch ISS flying over St. Louis starting Tuesday, February 20



Max. altitude


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

24 Feb

-0.7 05:41:13 10 SSE 05:42:51 13 SE 05:44:28 10 E

26 Feb

-2.1 05:31:33 10 W 18:24:51 15 SW 18:26:49 10 SSW

27 Feb

-1.3 04:41:19 15 SSE 04:42:24 17 SE 04:44:35 10 E

28 Feb

-3.9 05:24:27 24 SW 05:26:18 90 S 05:29:35 10 NE

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 second planet form the sun will be climbing out of the sun’s glare by the end of the month. Typically the 30 minute mark after sunset is what we use to determine if a planet is visible yet. Using this approach Venus will still be too low to be seen for most of this week. By the 28th Venus will be about 6° above the horizon at the 30 minute mark. So for those with clear western horizons you should be able to see Venus soon after sunset low in the west.
The evening apparition of Venus that is starting will last all the way through October 2018. So for most of the year Venus will be an early evening target. Another observing note is that Venus will start in a gibbous phase and end this apparition in a crescent phase. Planets that are closer to the sun than we are exhibit phases like the moon does. As the apparition progresses Venus will grow brighter because it will be getting closer to Earth. On October 26 Venus will reach inferior conjunction which is when Venus passes between the Earth and Sun.


The red planet has started another apparition and can be found rising in the east by 2:10 a.m. Mars will be visible low in the east around 3:00 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 this link:


The king of the planets can be found rising by 12:20 a.m. but can be easily seen by 2:00 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 3:44 a.m. and will be an easy target by 5:00 a.m.

Our next Star Party will be held on Friday, March 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 March 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.