Ephemeris: 09/01/2025 – Previewing September skies
This is Ephemeris for Labor Day, Monday, September 1st. Today the Sun will be up for 13 hours and 13 minutes, setting at 8:18, and it will rise tomorrow at 7:06. The Moon, 1 day past first quarter, will set at 12:52 tomorrow morning.
Let’s look at the skies for the month of September. The sun will be moving at its greatest speed in its retreat to the south. Daylight hours in the Interlochen/Traverse City area and will drop from 13 hours and 13 minutes today to 11 hours and 44 minutes on the 30th. The altitude of the Sun above the southern horizon at local noon will be 54 degrees today, and will descend to 42 degrees on the 30th. Local noon at mid-month will be around 1:37 pm. The season of summer is getting short, so enjoy it while you can. Summer ends and autumn begins at 2:20 PM on September 22nd, the autumnal equinox. This year the Harvest Moon, the nearest full moon to the equinox, will fall next month, this month it’s the Corn Moon.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
September Evening Star Chart
The planets and stars are plotted for the 15th at 10 p.m. EDT in the evening and 6 a.m. for the morning chart. These are the chart times. Note that Traverse City is located approximately 45 minutes behind our time meridian, West 75° longitude. (An hour 45 minutes behind our daylight saving time meridian during EDT). To duplicate the star positions on a planisphere you may have to set it to 1 hour 45 minutes earlier than the current time.
September Morning Star Chart
For a list of constellation names to go with the abbreviations, click here.
- Pointer stars at the front of the bowl of the Big Dipper point to Polaris, the North Star.
- Leaky dipper drips on Leo.
- Follow the arc of the handle of the Big Dipper to the star Arcturus.
- The Summer Triangle is in red.
Twilight Limits, Nautical and Astronomical
| EDT | |||||||
| Morning | Twilight | Evening | Twilight | Dark | Night | Moon | |
| Date | Astro. | Nautical | Nautical | Astro. | Start | End | Illum. |
| 2025-09-01 | 5h23m | 6h01m | 21h28m | 22h06m | 0h01m | 5h23m | 0.68 |
| 2025-09-02 | 5h24m | 6h02m | 21h26m | 22h04m | 0h53m | 5h24m | 0.77 |
| 2025-09-03 | 5h26m | 6h04m | 21h24m | 22h02m | 1h54m | 5h26m | 0.85 |
| 2025-09-04 | 5h27m | 6h05m | 21h22m | 22h00m | 3h05m | 5h27m | 0.92 |
| 2025-09-05 | 5h29m | 6h06m | 21h20m | 21h58m | 4h20m | 5h29m | 0.97 |
| 2025-09-06 | 5h30m | 6h08m | 21h18m | 21h55m | – | – | 1.00 |
| 2025-09-07 | 5h32m | 6h09m | 21h16m | 21h53m | – | – | 1.00 |
| 2025-09-08 | 5h33m | 6h10m | 21h14m | 21h51m | – | – | 0.97 |
| 2025-09-09 | 5h35m | 6h12m | 21h12m | 21h49m | – | – | 0.92 |
| 2025-09-10 | 5h36m | 6h13m | 21h10m | 21h47m | – | – | 0.84 |
| 2025-09-11 | 5h38m | 6h14m | 21h08m | 21h44m | – | – | 0.75 |
| 2025-09-12 | 5h39m | 6h16m | 21h06m | 21h42m | 21h42m | 22h19m | 0.64 |
| 2025-09-13 | 5h41m | 6h17m | 21h04m | 21h40m | 21h40m | 23h06m | 0.53 |
| 2025-09-14 | 5h42m | 6h18m | 21h02m | 21h38m | 21h38m | – | 0.41 |
| 2025-09-15 | 5h44m | 6h19m | 21h00m | 21h36m | 21h36m | 0h05m | 0.31 |
| 2025-09-16 | 5h45m | 6h21m | 20h58m | 21h34m | 21h34m | 1h15m | 0.21 |
| 2025-09-17 | 5h46m | 6h22m | 20h56m | 21h32m | 21h32m | 2h29m | 0.13 |
| 2025-09-18 | 5h48m | 6h23m | 20h54m | 21h29m | 21h29m | 3h44m | 0.07 |
| 2025-09-19 | 5h49m | 6h25m | 20h52m | 21h27m | 21h27m | 4h57m | 0.03 |
| 2025-09-20 | 5h51m | 6h26m | 20h50m | 21h25m | 21h25m | 5h51m | 0.00 |
| 2025-09-21 | 5h52m | 6h27m | 20h48m | 21h23m | 21h23m | 5h52m | 0.00 |
| 2025-09-22 | 5h53m | 6h28m | 20h46m | 21h21m | 21h21m | 5h53m | 0.02 |
| 2025-09-23 | 5h55m | 6h30m | 20h44m | 21h19m | 21h19m | 5h55m | 0.05 |
| 2025-09-24 | 5h56m | 6h31m | 20h42m | 21h17m | 21h17m | 5h56m | 0.10 |
| 2025-09-25 | 5h57m | 6h32m | 20h40m | 21h15m | 21h15m | 5h57m | 0.17 |
| 2025-09-26 | 5h59m | 6h33m | 20h38m | 21h13m | 21h20m | 5h59m | 0.25 |
| 2025-09-27 | 6h00m | 6h35m | 20h36m | 21h11m | 21h56m | 6h00m | 0.33 |
| 2025-09-28 | 6h01m | 6h36m | 20h35m | 21h09m | 22h43m | 6h01m | 0.42 |
| 2025-09-29 | 6h03m | 6h37m | 20h33m | 21h07m | 23h39m | 6h03m | 0.52 |
| 2025-09-30 | 6h04m | 6h38m | 20h31m | 21h05m | – | 6h04m | 0.62 |
Twilight calendar was generated using Cartes du Ciel (Sky Charts).
See my blog post: Twilight Zone for the definitions of the different periods of twilight here: https://bobmoler.wordpress.com/2018/09/27/.
NASA Calendar of Planetary Events
Sep 1 Mo Venus: 31.2° W
1 Mo 6:04 PM Moon South Dec.: 28.6° S
7 Su 2:09 PM Full Moon
7 Su 2:13 PM Total Lunar Eclipse
7 Su 7:08 PM Moon Ascending Node
8 Mo 4:09 PM Moon-Saturn: 4° S
10 We 8:10 AM Moon Perigee: 364800 km
12 Fr 5:48 PM Moon-Pleiades: 1° S
12 Fr 11:28 PM Mars-Spica: 2.2° N
13 Sa 6:46 AM Mercury Superior Conjunction
14 Su 6:33 AM Last Quarter
14 Su 5:23 PM Moon North Dec.: 28.6° N
16 Tu 7:06 AM Moon-Jupiter: 4.7° S
16 Tu 1:58 PM Moon-Pollux: 2.5° N
17 We 1:24 PM Moon-Beehive: 2.1° S
19 Fr 4:59 AM Venus-Regulus: 0.5° N
19 Fr 7:11 AM Moon-Regulus: 1.4° S
19 Fr 7:46 AM Moon-Venus: 0.9° S
20 Sa 7:13 PM Moon Descending Node
21 Su 1:10 AM Saturn Opposition
21 Su 3:42 PM Partial Solar Eclipse (Not here.
In New Zealand and Antarctica)
21 Su 3:54 PM New Moon
22 Mo 2:20 PM Autumnal Equinox
23 Tu 7:29 AM Neptune Opposition
23 Tu 5:31 PM Moon-Spica: 1.2° N
24 We 10:50 AM Moon-Mars: 4.3° N
26 Fr 5:46 AM Moon Apogee: 405600 km
27 Sa 1:34 PM Moon-Antares: 0.7° N
29 Mo 2:09 AM Moon South Dec.: 28.6° S
29 Mo 7:54 PM First Quarter
Oct 1 We Venus: 23.9° W
Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC), with modifications by the author.
http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html.
If you go to the above site, you can print out a list like the above for the entire year or calendar pages for your time zone.
Sun and Moon Rising and Setting Events
LU Ephemeris of Sky Events for Interlochen/TC
September, 2025 Local time zone: EDT
+-----------------------------------------------------------------------+
| DATE | SUN SUN DAYLIGHT| TWILIGHT* |MOON RISE OR ILLUM |
| | RISE SET HOURS | END START |PHASE SET** TIME FRACTN|
+=======================================================================+
|Mon 1| 07:05a 08:18p 13:13 | 09:24p 05:59a | Set 12:52a 66%|
|Tue 2| 07:06a 08:17p 13:10 | 09:22p 06:00a | Set 01:54a 75%|
|Wed 3| 07:07a 08:15p 13:07 | 09:20p 06:01a | Set 03:04a 84%|
|Thu 4| 07:09a 08:13p 13:04 | 09:18p 06:03a | Set 04:19a 91%|
|Fri 5| 07:10a 08:11p 13:01 | 09:16p 06:04a | Set 05:36a 96%|
|Sat 6| 07:11a 08:09p 12:58 | 09:14p 06:06a | Set 06:53a 99%|
+------+-----------------------+----------------+-----------------------+
|Sun 7| 07:12a 08:07p 12:55 | 09:12p 06:07a |Full Rise 08:10p 100%|
|Mon 8| 07:13a 08:05p 12:52 | 09:10p 06:08a | Rise 08:30p 98%|
|Tue 9| 07:14a 08:04p 12:49 | 09:08p 06:10a | Rise 08:51p 93%|
|Wed 10| 07:16a 08:02p 12:46 | 09:06p 06:11a | Rise 09:14p 86%|
|Thu 11| 07:17a 08:00p 12:43 | 09:04p 06:12a | Rise 09:43p 77%|
|Fri 12| 07:18a 07:58p 12:39 | 09:02p 06:14a | Rise 10:19p 66%|
|Sat 13| 07:19a 07:56p 12:36 | 09:00p 06:15a | Rise 11:06p 55%|
+------+-----------------------+----------------+-----------------------+
|Sun 14| 07:20a 07:54p 12:33 | 08:58p 06:16a |L Qtr Rise 12:05a 44%|
|Mon 15| 07:22a 07:52p 12:30 | 08:56p 06:17a | Rise 01:14a 33%|
|Tue 16| 07:23a 07:50p 12:27 | 08:54p 06:19a | Rise 02:29a 23%|
|Wed 17| 07:24a 07:49p 12:24 | 08:52p 06:20a | Rise 03:44a 15%|
|Thu 18| 07:25a 07:47p 12:21 | 08:50p 06:21a | Rise 04:56a 8%|
|Fri 19| 07:26a 07:45p 12:18 | 08:48p 06:23a | Rise 06:06a 3%|
|Sat 20| 07:27a 07:43p 12:15 | 08:46p 06:24a | Rise 07:13a 1%|
+------+-----------------------+----------------+-----------------------+
|Sun 21| 07:29a 07:41p 12:12 | 08:44p 06:25a |New Set 07:33p 0%|
|Mon 22| 07:30a 07:39p 12:09 | 08:42p 06:26a | Set 07:50p 1%|
|Tue 23| 07:31a 07:37p 12:06 | 08:40p 06:28a | Set 08:07p 4%|
|Wed 24| 07:32a 07:35p 12:03 | 08:38p 06:29a | Set 08:27p 9%|
|Thu 25| 07:33a 07:33p 12:00 | 08:37p 06:30a | Set 08:50p 15%|
|Fri 26| 07:35a 07:32p 11:56 | 08:35p 06:31a | Set 09:19p 23%|
|Sat 27| 07:36a 07:30p 11:53 | 08:33p 06:33a | Set 09:56p 31%|
+------+-----------------------+----------------+-----------------------+
|Sun 28| 07:37a 07:28p 11:50 | 08:31p 06:34a | Set 10:42p 40%|
|Mon 29| 07:38a 07:26p 11:47 | 08:29p 06:35a |F Qtr Set 11:38p 50%|
|Tue 30| 07:39a 07:24p 11:44 | 08:27p 06:36a | Set 12:44a 60%|
+-----------------------------------------------------------------------+
* Nautical Twilight
** Moonrise or moonset, whichever occurs between sunset and sunrise
Generated using my LookingUp for DOS app.
Ephemeris: 08/29/2025 – Late August crescent Moon stays low in the western sky
This is Ephemeris for Friday, August 29th. Today the Sun will be up for 13 hours and 22 minutes, setting at 8:24, and it will rise tomorrow at 7:03. The Moon, 2 days before first quarter, will set at 10:48 this evening.
There’s an interesting feature that I’ve noticed about the Moon this time of year. When there’s a waxing crescent Moon in the evening, in late summer to early autumn, it’s seen pretty low in the southwestern sky after sunset. Tonight it’ll be two days before first quarter so it’ll be a fat crescent. However, when it’s seen after sunset, it will be very low in the southwestern sky. Contrast that for early risers, at this time of year the waning crescent Moon moves at a steep angle to the horizon, as do the planets now in the east. And of course the opposite is true for late winter and early spring moons. By the way, the Harvest Moon is in early October this year. The Harvest Moon is the nearest full moon to the autumnal equinox.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/28/2025 – The first stars
This is Ephemeris for Thursday, August 28th. Today the Sun will be up for 13 hours and 25 minutes, setting at 8:26, and it will rise tomorrow at 7:02. The Moon, 3 days before first quarter, will set at 10:23 this evening.
Astronomers think that the first stars that formed after the Big Bang were very different from the stars we see around us today. They are called Population 3* stars. In fact, none of them have survived to this time. Back then there were no heavy elements, just hydrogen and helium. This allowed much more massive stars to form than stars today. The reason is the lack of heavier elements that make the interior of the star to be more opaque. This allows the core’s radiant energy to counteract the gravity of the star’s mass better and limit the stars’ growth. Supermassive stars burn hotter and live much shorter lives, exploding to spew the core contents of heavier elements, enriching the nebulae from which later stars form.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
The above illustration comes from an article by Daegene Koh: Population III stars: The Universe’s ultimate reclusive pop stars.
* Stars are grouped into 3 populations based on their order of being recognized. The stars around us are population 1 stars. They have a lot of, what astronomers call, metals in their atmospheres. To an astronomer, when talking about stars, metals are any elements heavier than helium. Older stars we find in globular star clusters or in the centers of galaxies are classed as Population 2. They have lower amounts of metals in their atmosphere. The term for the amount of metals in a star’s atmosphere is called metallicity. Population 3 stars are the stars that are born just after The Big Bang when the universe was filled with just hydrogen and helium with possible tiny amounts of lithium and beryllium. These stars can grow very massive, and live very short lives, which is why we don’t see them anywhere near us. To spot the Population 3 stars we need a time machine. Fortunately we have one, the telescope. In looking back in space we are looking back in time, since the speed of light is finite. And the greatest time machine of all is the James Webb Space Telescope. Astronomers are hoping they can look back far enough to see Population 3 stars. Not individually, I don’t think, they’re too far away for that. But whole galaxies of them, at the dawn of time.
Like I’ve been saying in a whole bunch of contexts… They don’t make them like that anymore!
Ephemeris: 08/27/2025 – Taking our weekly look at the whereabouts of the naked-eye planets
This is Ephemeris for Wednesday, August 27th. Today the Sun will be up for 13 hours and 28 minutes, setting at 8:27, and it will rise tomorrow at 7:00. The Moon, halfway from new to first quarter, will set at 10:02 this evening.
Let’s take our weekly look at the whereabouts of the naked-eye planets. The Red Planet Mars is too close to the direction of the Sun to spot. This is the curse of trying to view evening planets, which are near the direction of the Sun in late summer and early fall, for us at higher latitudes. Saturn now rises at 9:27 PM in the east. In a telescope Saturn sports a very thin ring, a bit more than 3° from being edge on. This angle will decrease to about a third of a degree by November 23rd before increasing. By 6 AM Saturn will be in the southwest. Jupiter will appear above the brighter Venus in the Eastern sky And among the brighter winter stars. Mercury will be in line with Venus and Jupiter very near the horizon.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/26/2025 – Update on our expected nova T Coronae Borealis
This is Ephemeris for Tuesday, August 26th. Today the Sun will be up for 13 hours and 31 minutes, setting at 8:29, and it will rise tomorrow at 6:59. The Moon, 3 days past new, will set at 9:44 this evening.
There is a star in the constellation of Corona Borealis, the Northern Crown, which astronomers are expecting to become a nova which means become rapidly very bright. The initial predictions favored last year, 2024, but it has yet to explode. The star’s designation is T Coronae Borealis, or T CrB for short. It’s a variable star designation. And an explosion occurs on one member of this binary star system about every 80 years. The last time was in 1946. Jean Schneider* of the Paris Observatory thinks they found a pattern within the 80-year time frame. The 227.6-day period of the white dwarf star orbiting its much larger primary. This seems to match the last three explosions. So the next likely date will be November 10th this year. We’ll see.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
* I found a link to this on the spaceweather.com website in a section called T CrB Nova Watch.
Addendum
Ephemeris: 08/25/2025 – Two fascinating constellations in and near the Summer Triangle
This is Bob Moler with Ephemeris for Monday, August 25th. Today the Sun will be up for 13 hours and 33 minutes, setting at 8:31, and it will rise tomorrow at 6:58. The Moon, 2 days past new, will set at 9:27 this evening.
There are two small constellations in and near the Summer Triangle of bright stars. Both are near Altair the bottom star of the triangle in the southeast. The first is Delphinus the dolphin to the left of Altair. Delphinus is made-up of a small squished box of stars with another star below. It does look a dolphin leaping out of the water. The legendary Greek poet Arion, according to myth, was rescued by a dolphin. Also, the little squished box is an asterism called Job’s Coffin, though no one knows the origin of that name. The second constellation is above Altair, and within the Summer Triangle. It is called Sagitta the arrow. The stars do line up to look like a short arrow. It’s supposed to represent Cupid’s dart.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/22/2025 – Star Party tomorrow night the 23rd
This is Ephemeris for Friday, August 22nd. Today the Sun will be up for 13 hours and 42 minutes, setting at 8:36, and it will rise tomorrow at 6:55. The Moon, 1 day before new, will rise at 7:10 tomorrow morning.
Weather permitting, the Grand Traverse Astronomical Society and the Park Rangers will host a star party at Sleeping Bear Dunes National Lakeshore, at the Dune Climb tomorrow night, starting around 9 PM. The parking lane closest to the dune will be blocked off for telescopes. The start time is after sunset, and the brighter stars will be visible by 9:15. As it gets darker some of the brighter interstellar wonders of our Milky Way galaxy, will appear, with many star clusters and nebulae, including a peek at the Great Andromeda Galaxy next door. The Rangers will leave around 11 PM however if it stays clear and there’s enough interest, society members with their telescopes will stay longer. This is the last Sleeping Bear Dunes star party this year.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/21/2025 – The Milky Way’s Great Rift
This is Ephemeris for Thursday, August 21st. Today the Sun will be up for 13 hours and 45 minutes, setting at 8:38, and it will rise tomorrow at 6:53. The Moon, 2 days before new, will rise at 5:57 tomorrow morning.
Once one finds the Milky Way which is pretty hard to miss this month, it becomes obvious that the Milky Way is split lengthwise starting near Deneb, the northernmost star of the Summer Triangle, almost all the way to the Teapot of Sagittarius low in the south. That dark split is called the Great Rift. Galileo first discovered that the hazy clouds of the Milky Way were actually made of faint stars, so it was thought the dark areas were due to a lack of stars. The great 18th century astronomer William Herschel did star counts all over the sky with his telescope. A map his sister drew of the flattened shape of his universe shows the lack of distant stars in one direction. It’s not really fewer stars, but interstellar clouds of dust blocking the light of the stars behind them.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/20/2025 – Taking our weekly look at the whereabouts of the naked-eye planets
This is Ephemeris for Wednesday, August 20th. Today the Sun will be up for 13 hours and 48 minutes, setting at 8:39, and it will rise tomorrow at 6:52. The Moon, 3 days before new, will rise at 4:41 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. The Red Planet Mars is too close to the direction of the Sun to spot. This is the curse of trying to view evening planets, which are near the direction of the Sun in late summer and early fall, for us at higher latitudes. Saturn now rises at 9:55 PM in the east. In a telescope Saturn sports a very thin ring, a bit less than 3° from being edge on. By 6 AM Saturn will be in the southwest. Jupiter will appear above the brighter Venus in the Eastern sky And among the brighter winter stars. Venus is by far the brighter of the two planets. Mercury will be below the crescent Moon tomorrow morning.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 08/19/2025 – Mercury makes its morning appearance
This is Ephemeris for Tuesday, August 19th. Today the Sun will be up for 13 hours and 51 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, 3 days past last quarter, will rise at 3:25 tomorrow morning.
The tiny planet Mercury is making an appearance in the morning sky now. For the next week or so it will be visible around 6 AM. At least it’s time to start looking for it. Once found, it might be followed for another 20 minutes or so. This morning Mercury was at its greatest angular separation or elongation from the Sun of 18.6°. We have two periods where Mercury is easier to spot: on late winter and early spring evenings, and in the morning sky in late summer and early autumn. Of course Mercury must be at the proper elongation point at the time. Mercury is the smallest of the planets, being only 50% larger in diameter than our moon. In closeup, it looks much like our Moon, gray and cratered.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Bob Moler's Ephemeris Blog 