This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, April 2, 2021.

Information updated weekly or as needed.

Times given as local St. Louis time which is Central Daylight Time (CDT). For definitions of terminology used in the night sky update, click the highlighted text. If relying on times posted in Universal Time (UT), St. louis is -5 hours when CDT.

Public Telescope Viewings

Star parties at the Saint Louis Science Center have temporarily been canceled due to recommendations from the CDC regarding COVID-19. All public telescope events are canceled until further notice. As conditions change, we will reevaluate and update this article once public observing events resume.

Observing Highlight of the Week

Light pollution Seen from Space
Credit: NASA Earth Observatory image by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA’s Goddard Space Flight Center

This week starting on April 5 is International Dark Sky Week. This event was started by Jennifer Barlow in 2003 and has since grow to be an international event. Its intent is to bring awareness to light pollution and its negative effects. Most of us are familiar with light pollution due to the night sky we see from places like St. Louis. Light pollution is more than just a visual concern as we now know it can impact plants and animals including humans.

You can join the Dark Sky Week efforts by doing a few things. First, we can turn off any lights that are not necessary. As part of this effort the planetarium building will be dark during Dark Sky Week. In addition to turning off lights, we can all spend a little time learning about light pollution, its negative effects and how we can help mitigate those effects. One of the best sources of information on light pollution is the International Dark-Sky Association. For readers that live in the St. Louis Metro area, there is a local chapter of IDA in Missouri. You can find their website at Through them, you can learn about reginal efforts being made such as Lights Out Heartland, which are helping bring awareness to the negative effects of light pollution.

The Sun and Moon

The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA

Sunrise is at 6:44 a.m. on Friday, April 2 and sunset is at 7:26 p.m. providing us with over 12.5 hours of daylight. Even after sunset, the light from the Sun will dimly illuminate our sky for about 1 hour and 30 minutes. This period is called twilight, which ends around 8:57 p.m. this week. For those with a sundial, local noon occurs around 13:05 p.m. this week.

2021-04-02 6:44 a.m.7:26 p.m.
2021-04-03 6:42 a.m.7:27 p.m.
2021-04-04 6:41 a.m.7:28 p.m.
2021-04-05 6:39 a.m.7:29 p.m.
2021-04-06 6:38 a.m.7:30 p.m.
2021-04-07 6:36 a.m.7:31 p.m.
2021-04-08 6:35 a.m.7:32 p.m.
2021-04-09 6:33 a.m.7:32 p.m.
2021-04-10 6:32 a.m.7:33 p.m.


Moonrise for Friday, April 2 occurs after midnight at 1:38 a.m. and moonset will occur tomorrow at 11:03 a.m. on the following day. On Friday, April 2 the Moon will exhibit a waning gibbous phase with 56% of the lunar disk visible. Last quarter moon occurs on April 4 at 5:03 a.m.

International Space Station (ISS) Observing

Credit: NASA

Visible passes of ISS from St. Louis for the week of April 2 occur during evening hours. The best passes this week occur on the evenings of April 4 and 5. Use the table below for information about these and other visible passes this week.

Catch ISS from St. Louis starting Friday, April 2

Date Starts  Max. altitude  Ends  
02 Apr-3.2 20:42:4010NW 20:45:5546NE 20:46:4736ENE
03 Apr-2.5 19:55:2410NNW 19:58:2529NNE 20:01:2610E
03 Apr-1.9 21:32:1210WNW 21:34:2827WSW 21:34:2827WSW
04 Apr-3.3 20:44:3510WNW 20:47:5355SW 20:49:1530SSE
05 Apr-3.8 19:57:0710NW 20:00:2981NE 20:03:5010SE
06 Apr-1.3 20:47:1010W 20:49:3517SW 20:51:5210S
07 Apr-2 19:59:1910WNW 20:02:1830SW 20:05:1610SSE

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 Visible Planets

Looking West, at 8:00 pm, April 2, 2021
Credit: Stellarium, EG, 

Looking East Southeast, at 5:50 am, April 3, 2021
Credit: Stellarium, EG 

This week, three naked eye planets are visible. Mars is found high in the west after sunset. Jupiter and Saturn can be found in the east southeast before sunrise.


Currently Mars appears as a 1.3-magnitude object that will be visible high in the west about 40 minutes after sunset. Mars sets by 12:45 a.m.


Jupiter is starting to climb out of the Sun’s glare just before sunrise. For your best chance to see Jupiter, look east southeast 1-hour before sunrise.


Saturn has returned to our morning sky. Look east southeast 1-hour before sunrise to find the ringed planet.

Mars Perseverance Rover Update

After a successful landing on Mars, NASA’s newest rover Perseverance is beginning the early stages of its mission. Each week this section will contain a few of the images sent back to Earth as Perseverance explores Jezero crater. If you have not seen it yet, the first thing I would recommend watching is a video NASA released of the rover’s landing.

The Ingenuity helicopter is preparing for placement on the surface of Mars. Ingenuity landed on Mars along with the Perseverance rover, tucked safely on the underside of the rover. The earliest Ingenuity will fly is April 11, 2021. Once detached from Perseverance, NASA mission specialists will have about 30 days to operate the Ingenuity mission. Learn more about Ingenuity here.

NASA’s Mars Exploration Program website will be a good resource to visit each day to find any updates on the rover and its mission. Aside from information about Perseverance, NASA’s website will keep you up to date on any new findings from other Mars missions and research.

Ingenuity Helicopter is Ready to Drop
Credit: NASA/JPL-Caltech/MSSS

James S. McDonnell Planetarium

Night Sky Update: April 2-April 10, 2021