Bob Moler's Ephemeris Blog

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.