This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, September 26.  All times are given as local St. Louis time (Central Daylight 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, October 6, 2017 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 6:53 a.m. on Tuesday, September 26 and sunset is at 6:51 p.m. providing us with about 12 hours of daylight.  Even after sunset, the light from the sun will still dimly illuminate our sky for a bit less than 2 hours.  This period of time is called twilight, which ends around 8:19 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:52 p.m. this week.

Day Sunrise Sunset
 26 Sep 6:53 a.m. 6:51 p.m.
 27 Sep 6:53 a.m. 6:50 p.m.
 28 Sep 6:54 a.m. 6:48 p.m.
 29 Sep 6:55 a.m. 6:46 p.m.
 30 Sep 6:56 a.m. 6:45 p.m.
 01 Oct 6:57 a.m. 6:43 p.m.
 02 Oct 6:58 a.m. 6:42 p.m.
 03 Oct 6:59 a.m. 6:40 p.m.
 04 Oct 7:00 a.m. 6:39 p.m.

Moonrise for Tuesday, September 26 occurs at 12:53 p.m. and moonset will occur at 11:07 p.m.  On Tuesday, September 26 the moon will be exhibiting a waxing crescent phase with about 37% of the lunar disk illuminated.  First quarter moon occurs on September 27.

International Space Station (ISS) Observing

Visible passes of ISS from St. Louis for the week of September 26 occur in the evening hours.  The best of these occur on the evenings of September 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, September 26

Mag Starts Max. altitude Ends
Time Alt. Az. Time Alt. Az. Time Alt. Az.
26 Sep -3.7 19:34:18 10 SW 19:37:30 57 SE 19:40:35 11 ENE
26 Sep -1.0 21:11:42 10 WNW 21:13:16 18 NW 21:13:16 18 NW
27 Sep -2.1 20:18:43 10 W 20:21:40 30 NNW 20:23:22 19 NNE
28 Sep -3.1 19:26:00 10 WSW 19:29:12 54 NW 19:32:25 10 NE
28 Sep -0.8 21:04:39 10 NW 21:05:59 13 NNW 21:05:59 13 NNW
29 Sep -1.3 20:11:18 10 WNW 20:13:36 17 NNW 20:15:48 10 NNE
30 Sep -1.8 19:18:12 10 W 19:20:59 26 NNW 19:23:49 10 NNE
02 Oct -1.2 19:10:49 10 WNW 19:12:54 16 NNW 19:14:58 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 second planet from the sun can be found in the morning hours just before sunrise. Your best shot to see Venus is to find a clear eastern horizon view around 5:30 a.m.  Be careful though as you will be fighting the rising sun’s twilight glow.


The red planet has started another apparition.  It can now be found climbing out of the Sun’s glare a little after 6:00 a.m.  Mars will reach about 10° above the eastern horizon just before civil twilight begins.  This means Mars will be a tough pull for the next week or two but you should be able to find the red planet about 45 minutes before sunrise.  For the time being you need to find a very clear eastern horizon free of any trees or buildings to see Mars.  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 below.


The king of the rings is visible once again.  You can find it at 7:40 p.m. by looking to the south.  Saturn will set by 10:49 p.m.

Our next Star Party will be held on Friday, October 6, 2017, 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 October 6, 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.