This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Sunday, July 13, 2025.
Information updated weekly or as needed.
Times given as local St. Louis time this week will be in Daylight Saving Time. 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. Times posted in the Night Sky Update are in the 24-hour format.
Join us for our next star party, Friday, August 1, 2025, held in association with the St. Louis Astronomical Society.
For details, see the information at the bottom of this page or visit: https://www.slsc.org/explore/mcdonnell-planetarium/public-telescope-viewings
Observing Highlight of the Week
This week is our next opportunity to see a Titan shadow transit on Saturn. These events are only visible when Saturn is near an equinox. Saturn last reached an equinox on May 5, 2025. For the rest of this year, we have a few remaining opportunities to see this. If you miss these transits, it will be 15 years until your next opportunity.
The transit this week occurs on Friday, July 18, 2025. It begins at 02:00 CDT and ends at 07:00 CDT. From St. Louis, we will see about 2/3 of the transit before the Sun rises. When the transit begins, Saturn will be roughly 28° above the eastern horizon around 118° azimuth.
Saturn rises at 23:30 on July 17, 2025. About an hour later, the planet will be visible low in the east depending on your view of the horizon. Viewing Saturn through a telescope around 00:30, you will see Titan just east of Saturn and Dione and Rhea west of the planet. Titan’s shadow begins to appear on the eastern limb of Saturn a little north of the ring system. By 02:00, the transit is underway.
After July 18, The next transits occur on August 3 and 19, 2025. All dates and times for these events were found in an article posted on the Sky and Telescope website. You can find that article here.
T CrB Nova Update 7/13/2025
If you are still interested in seeing the recurrent nova T Coronae Borealis, there is still hope. The nova has not yet occurred meaning we are in a waiting game. It could happen this year or it could happen next year. We will have to wait and see. If you are still interested in this event, the part of the sky the nova will appear is overhead once it is dark. By 03:00, the constellation Corona Borealis will be found low in the western sky. Spaceweather.com is still posting magnitude estimates from the AAVSO. This is the resource I recommend following to keep up with any changes in the star’s brightness. Current magnitude of the system is 10.0.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 05:47 on Sunday, July 13 and sunset is at 20:25 providing about 14.5 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for about 2 hours. This period is called twilight, which ends around 22:19 this week. For those with a sundial, local noon occurs around 13:07 on July 13, 2025.
Moon
Moonrise for Sunday, July 13, is at 22:31 and moonset occurs at 09:41 the following morning. On July 13, 2025, the Moon will exhibit a waning gibbous phase with 90% disk illumination. By July 21, 2025, the Moon will exhibit a waning crescent phase with 11% disk illumination. Last quarter moon occurs on July 17, 2025, at 19:38 CDT.
International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of July 13 occur during morning and evening hours. The table above lists the best of these passes. If you do not live in the area, you can use https://heavens-above.com/ to set your viewing location and get times for where you are.
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°.
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 21:20 on July 13, 2025. Credit: Stellarium, EG
Looking east at 04:00 on July 14, 2025. Credit: Stellarium, EG
Three naked eye planets will be visible this week. Mars is visible in the west after sunset once it is dark. Venus and Saturn are visible before sunrise in the east.
Venus
Venus is found in the east before sunrise for the rest of the year. It currently rises around 03:00. Look for Venus in the east around 04:00 as it clears tree lines.
Mars
Look for Mars in the western sky after sunset. The current apparition of Mars will continue throughout the rest of 2025. As the year continues, Mars will slowly appear closer to the western horizon each night. Mars sets around 23:00.
Saturn
Saturn can be found in the east before sunrise. Saturn rises around 23:46 this week. The planet should be high enough to see by 01:00. If you missed the last Titan shadow transit, the next one occurs on July 18, 2025.
Our next Star Party will be held on Friday, August 1, 2025, from 6:30 pm until 9:30 pm
On the first Friday of each month, the St. Louis Astronomical Society and the Saint Louis 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 August 1, join us indoors in our planetarium theater for our free monthly sky lecture.
The St. Louis Astronomical Society helps host the monthly Star Parties at the Saint Louis Science Center. In addition to our nighttime viewings, they also help facilitate our daytime event called Solar Sundays. These daytime viewing sessions occur every Sunday through Labor Day from 11:00-15:00 weather permitting. Visit SLAS’s website linked above to learn about other telescope events SLAS hosts around the St. Louis area.
James S. McDonnell Planetarium
Night Sky Update: July 13-21, 2025
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