This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, May 17.  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, June 3, 2016 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 5:47 a.m. on Tuesday, May 17 and sunset is at 8:08 p.m. providing us with roughly 14.5 hours of daylight.  Even after sunset, the light from the Sun will still dimly illuminate our sky for nearly two hours.  This period of time is called twilight, which ends around 9:57 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:57 p.m. this week.

Next Saturday, May 21 we will be safely observing the Sun outside the planetarium.  We will continue to schedule free safe solar observing every month on the third Saturday of the month.  Safe solar telescopes will be setup outside the planetarium entrance from 10:00 a.m. to 4:00 p.m. weather permitting.  Inside the planetarium various activities will be setup to help inform visitors about the upcoming 2017 total solar eclipse and ways in which the Sun affects our daily life.




17 May

5:47 a.m.

8:08 p.m.

18 May

5:46 a.m.

8:09 p.m.

 19 May

5:46 a.m.

8:10 p.m.

 20 May

5:45 a.m.

8:11 p.m.

 21 May

5:44 a.m.

8:12 p.m.

 22 May

5:43 a.m.

8:13 p.m.

 23 May

5:43 a.m.

8:13 p.m.

 24 May

5:42 a.m.

8:14 p.m.

 25 May

5:41 a.m.

8:15 p.m.


Moonrise for Tuesday, May 17 occurs at 4:22 p.m. and moonset will occur at 4:14 a.m. on the following day.  On May 17 the moon will be exhibiting a waxing gibbous phase with about 85% disk coverage.  Full moon occurs on Saturday, May 21.  Full moon in May is known as the Full Flower Moon.

International Space Station (ISS) Observing

This week visible passes of ISS from St. Louis will occur during morning hours.  The best pass this week occurs in the morning hours of May 25.  Use the table below for information regarding this pass and others this week.

Catch ISS flying over St. Louis in the morning hours starting Tuesday, May 17.

Date Mag


Max. altitude


Time Alt. Az. Time Alt. Az. Time Alt. Az.
19 May  0.0 01:58:25 13 NNE 01:58:25 13 NNE 01:58:52 NE ENE
20 May -0.4 02:39:55 14 NNW 02:39:57 14 NNW 02:41:50 10 NNE
21 May  0.0 01:48:46 14 NNE 01:48:46 14 NNE 01:49:30 10 NNE
23 May -0.3 04:51:11 10 NNW 04:53:26 17 NNE 04:55:41 10 ENE
24 May  0.0 03:58:51 10 N 04:00:23 13 NNE 04:01:54 10 NE
25 May -1.1 04:41:38 10 NNW 04:44:33 29 NNE 04:47:27 10 E  

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 is currently found in Ophiuchus rising at 8:34 p.m.  By 9:30 p.m.  Mars will be easily seen in the southeastern sky.  Mars will continue to climb higher in our sky as we approach May 22, 2016 which is the next opposition of Mars.  Mars is back and getting better once again.


Jupiter now rises before the Sun sets. To see Jupiter you will have to look south at about 8:40 p.m.  Jupiter sets at 2:44 a.m.  Each week Jupiter will set approximately 30 minutes earlier than it did the week before.


The ringed planet is rising before midnight and can be seen in the southeast shortly after twilight ends.  Saturn rises at 9:18 p.m. and can be seen low in the southeast around 10:30 p.m.

Deep Sky Object of the Week

A few years ago the night sky update included a section that highlighted one constellation a month and a few objects of interest inside of it.  Unfortunately of the 88 constellations there are only about 60 we can see in St. Louis and of these there are only so many that have enough objects to reference that would interest both beginners and advanced observers.  In 2015 we changed things a bit for this section and instead of highlighting one constellation for each month we highlighted one Messier object a week using the Astronomical League’s Binocular Messier program as our guide.  We will continue this into 2016 but instead of using the Astronomical League’s binocular Messier program we will use their Binocular Deep Sky Program.

The Astronomical League is an amateur astronomy society that is composed of over 240 local amateur astronomy societies across the United States and includes members at large and other supporting members.  Their goal is to promote the science of astronomy through education, incentive and communication.

One of the many ways the Astronomical League has assisted amateur astronomers around the world is by creating various observing programs that highlight different aspects of astronomy and how an amateur astronomer can observe the sky and learn more about astronomy in doing so.  Some of these programs are introductory and are targeted at those beginning to learn about observational astronomy and some are extremely advanced, require specialized equipment and require a large amount of time to complete.  These observing programs cover most any type of object or way to observe the sky so everyone should be able to find one that matches their interests and abilities.  It is important to note that these programs are not part of any class or lecture series but are rather lists of objects that highlight types of objects or observing methods relevant to astronomy.  Taking part in these programs is done under one’s own choice.  To officially complete each program you do have to be a member of the Astronomical League but you do not have to join to use them as observing guides or education tools.  I would urge anyone interested in astronomy to look at these programs as they will help organize observing sessions and will help refine observing skills you already have.  You can find out more information about the Astronomical League’s observing programs here

The observing program we will use to help guide us through the 2016 observing year is the Binocular Deep Sky Program.  This is a program that will appeal to both beginning and advance observers.  Too often it is thought that you need to have a telescope for astronomical observations.  Telescopes make great observing tools and yes they can show you more than binoculars but they do have their limitations.  Cost, size, weight and complexity will often be a surprise to people when they first learn about telescopes.  These factors can keep people from using telescopes they own or from buying one at all.  The best advice to follow is a good observing tool is one you will use.

The binocular deep sky program is an introduction to deep sky objects beyond the Messier catalog.  It will introduced viewers to the New General Catalog (NGC) and some of the lesser known deep sky catalogs such as the Stock, Collinder and Melotte.  Each week we will highlight a deep sky object that is part of the Astronomical League’s binocular deep sky program.  This program is tougher than Messier binocular program as the objects are not always as obvious and they will require larger binoculars than the Messier program.  50mm binoculars are recommended but many of the targets can be seen through smaller aperture instruments.  I would urge each observer to fulfill the requirements of the program even if you do not intend to join the League for completion.  The requirements involve logging observing data that can help refine observing skills that will be useful later down the road.  If you have an interest in astronomy and learning more about observational astronomy I would also recommend checking out one of the two excellent astronomy societies near St. Louis.  Both are members of the Astronomical League and both do numerous public observing nights around town.  These clubs are the

St. Louis Astronomical Society and

Astronomical Society of Eastern Missouri

If you do not live in the St. Louis, Missouri area chances are you have similar astronomical societies where you live.

The deep sky object for the week of May 3 is the open star cluster Melotte 111 (Mel 111).  This open cluster of roughly 40 stars is estimated to be 288 light years away making it one of the closest star clusters to our solar system.  At this distance these stars shine with an apparent magnitude of 1.8 making it visible to the unaided eye.  At 400 million years old this cluster is quite young.  When these stars first started to shine some of the earliest land plants were starting to appear on the Earth.

Since Mel 111 is so bright it is hard to imagine why it was not included on Messier’s or Herschel’s lists of deep sky objects.  The simple reason why is Mel 111 was not proven to be a star cluster until 1938 when R.J. Trumpler was able to prove the 37 stars were true cluster members.

Located in the constellation Coma Berenices, Mell 111 can be found by starting with the Big Dipper in Ursa Major.  You can find the Big Dipper in the due north around 10:00 p.m.  If you find the handle of the Big Dipper and begin to scan to the south you will find the bright star Cor Caroli in Canes Venatici.  From here Coma Berenice will be another ten degrees south of this star.  Mel 111 can be found just south of the bright star Gamma Comae Berenices.  To the unaided eye it will appear as a faint smudge of light in the sky and through binoculars you will find a bright scattering of stars that will fill most of your field of view.  Use the maps below to find Mel 111 in Coma Berenices.

The deep sky object for the week of May 10 is the open star cluster IC 4665.  IC 4665 is part of the Index Catalog which is an update to the New General Catalog (NGC).  The Index Catalog was published in two parts, the first in 1895 and the second in 1908.  Together the IC I and IC II catalogs document the discovery of galaxies, star clusters and nebulae between the years 1888 and 1907 which together contain 5,386 objects.

This week’s target IC 4665 is an open star cluster that is comprised of approximately 30 stars that are estimated to be 36 million years old.  These stars first started to shine around the same time a major extinction event occurred on the Earth known as the Eocene-Oligocene extinction.  This extinction event primarily affected marine life and was thought to be caused by large meteorite impacts.  One of these was the Popigai impact in Siberia and the other was the impact that created Chesapeake Bay impact crater off the east coast of Virginia.

At a distance of 1,400 light years IC 4665 shines with an apparent magnitude of 4.2 making it an easy target even in light polluted skies.  The Trumpler classification for IC 4665 is III, 2, p which means it is a detached star cluster with no central concentration, it has a moderate range of stellar magnitudes and it is a poor cluster with less than 50 members.

To find IC 4665 you will have to locate the constellation Ophiuchus the Serpent Bearer.  This constellation can be found by first looking for the asterism known as the Summer Triangle.  This can be found by looking east around 11:00 p.m.  The Summer Triangle is made up of the bright stars Vega, Deneb and Altair which are found in the constellations Lyra, Cygnus and Aquila respectively.  Your next step is to find the planet Mars.  Right now Mars can be found in the constellations Scorpius which will be seen in the south around 11:00 p.m.  Mars will be unmistakable as it is the brightest object you can currently see in the southern skies after 10:00 p.m.  Once you can find both the star Vega and the planet Mars your next step will be to identify the bright star that is seen halfway between them called Rasalhague.  This is the brightest star in Ophiuchus and is near the location of IC 4665.  Once you can find Rasalhague or what some maps may label Alpha Ophiuchi you will want to grab your binoculars and scan to the southeast to find the next bright star Cebalrai (Beta Ophiuchi).  About one degree to the north of this star you will find a large scattering of bright stars which is IC 4665.  For more assistance use the maps below.

The deep sky object for the week of May 17 is the open star cluster NGC 6520.  This young open star cluster contains about 60 members which formed roughly 54 million years ago.  At a distance of 5,400 light years this star cluster is possibly located in the next arm in of the Milky Way Galaxy.  At this distance NGC 6520 will shine with an apparent magnitude of 7.6 making it a doable target for city observers but it will be a challenge.  NGC 5260 has a Trumpler classification of I, 2, m which means it is well detached from background stars with a strong central concentration, its stars have a moderate range of stellar magnitudes and it has a moderate population as it contains between 50 and 100 stars.

NGC 6520 is located in the constellation Sagittarius which can be found in the south around 1:00 a.m.  To find Sagittarius it is best to start by locating the constellation Scorpius.  If you look south around 1:00 a.m. you will find a bright fishhook shape of stars which is Scorpius.  Looking to the east of the fishhook you will see what looks like a teapot shape of stars.  This is the famous Teapot asterism which is the pattern you look for to identify Sagittarius.  Once you find this shape you need to identify the stars Delta and Gamma Sagittarii.  NGC 6520 can be found about two degrees north of Gamma Sagittarii.  Through binoculars it will look like a small fuzzy patch of light.  Use the links below for help in locating NGC 6520.                                               

Our next Star Party will be held on Friday, June 3, 2016, 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 June 3, 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.