Land of the Long Twilights

The first (and only!) sunset1 this year at Amundsen–Scott South Pole Station in Antarctica occurs on March 22 at 0615 UTC (using “astronomer’s time” as time zone has no meaning so close to the South Pole).

The year’s first and only end of civil twilight (when the geometric center of the Sun lies 6° below the horizon) occurs on April 4 at 1153 UTC. That’s 13d05h38m after sunset.

The year’s first and only end of nautical twilight (when the geometric center of the Sun lies 12° below the horizon) occurs on April 21 at 0409 UTC. That’s 16d16h16m after the end of civil twilight.

The year’s first and only end of astronomical twilight (when the geometric center of the Sun lies 18° below the horizon) occurs on May 11 at 0521 UTC. That’s 20d01h12m after the end of nautical twilight, and 49d23h06m after sunset. That’s one heck of a long twilight!

Night lasts from May 11 at 0521 UTC until astronomical twilight begins on July 31 at 1916 UTC. A duration of 81d13h55m.

Nautical twilight begins on August 21 at 0024 UTC. That’s 20d05h08m after the beginning of astronomical twilight.

Civil twilight begins on September 6 at 2121 UTC. That’s 16d20h57m after the beginning of nautical twilight.

The first and only sunrise of the year occurs on September 20 at 0945 UTC. “Morning” twilight lasts a total of 50d14h29m.

The Sun remains above the horizon continuously until sunset on March 22, 2025 at 1100 UTC. Daylight “hours” last 183d01h15m.

Strange place!

1Sunrise and sunset. For computational purposes, sunrise or sunset is defined to occur when the geometric zenith distance of the center of the Sun is 90.8333 degrees. That is, the center of the Sun is geometrically 50 arcminutes below a horizontal plane. For an observer at sea level with a level, unobstructed horizon, under average atmospheric conditions, the upper limb of the Sun will then appear to be tangent to the horizon. The 50-arcminute geometric depression of the Sun’s center used for the computations is obtained by adding the average apparent radius of the Sun (16 arcminutes) to the average amount of atmospheric refraction at the horizon (34 arcminutes).
[Reference: https://aa.usno.navy.mil/faq/RST_defs, but see here:
https://digitalcommons.mtu.edu/etdr/697/]

Note: SkySafari 6 Pro, Version 6.8.2 (6820) for MacOS was used to determine these dates and times. The location coordinates used for Amundsen–Scott South Pole Station were 89° 58′ 59.9″ S, 139° 16′ 01.2″ E, 2835 m.

Fun Fact: Did you know that there is a seismic station near the south pole, and that it has been operating since 1957?

Zodiacal Light 2023

In 2023, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Tucson, Arizona (32° 16′ N, 111° 03′ W).

Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:

January 2023
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8
Zodiacal Light 7:02 – 7:14 p.m. West
9
Zodiacal Light 7:03 – 8:03 p.m. West
10
Zodiacal Light 7:04 – 8:04 p.m. West
11
Zodiacal Light 7:04 – 8:04 p.m. West
12
Zodiacal Light 7:05 – 8:05 p.m. West
13
Zodiacal Light 7:06 – 8:06 p.m. West
14
Zodiacal Light 7:07 – 8:07 p.m. West
15
Zodiacal Light 7:07 – 8:07 p.m. West
16
Zodiacal Light 7:08 – 8:08 p.m. West
17
Zodiacal Light 7:09 – 8:09 p.m. West
18
Zodiacal Light 7:10 – 8:10 p.m. West
19
Zodiacal Light 7:11 – 8:11 p.m. West
20
Zodiacal Light 7:11 – 8:11 p.m. West
21
Zodiacal Light 7:12 – 8:12 p.m. West
22
Zodiacal Light 7:13 – 8:13 p.m. West
23 24 25 26 27 28
29 30 31        

February 2023
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7
Zodiacal Light 7:26 – 7:58 p.m. West
8
Zodiacal Light 7:27 – 8:27 p.m. West
9
Zodiacal Light 7:27 – 8:27 p.m. West
10
Zodiacal Light 7:28 – 8:28 p.m. West
11
Zodiacal Light 7:29 – 8:29 p.m. West
12
Zodiacal Light 7:30 – 8:30 p.m. West
13
Zodiacal Light 7:31 – 8:31 p.m. West
14
Zodiacal Light 7:31 – 8:31 p.m. West
15
Zodiacal Light 7:32 – 8:32 p.m. West
16
Zodiacal Light 7:33 – 8:33 p.m. West
17
Zodiacal Light 7:34 – 8:34 p.m. West
18
Zodiacal Light 7:34 – 8:34 p.m. West
19
Zodiacal Light 7:35 – 8:35 p.m. West
20
Zodiacal Light 7:36 – 8:36 p.m. West
21 22 23 24 25
26 27 28        

March 2023
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9
Zodiacal Light 7:49 – 8:43 p.m. West
10
Zodiacal Light 7:49 – 8:49 p.m. West
11
Zodiacal Light 7:50 – 8:50 p.m. West
12
Zodiacal Light 7:51 – 8:51 p.m. West
13
Zodiacal Light 7:52 – 8:52 p.m. West
14
Zodiacal Light 7:52 – 8:52 p.m. West
15
Zodiacal Light 7:53 – 8:53 p.m. West
16
Zodiacal Light 7:54 – 8:54 p.m. West
17
Zodiacal Light 7:55 – 8:55 p.m. West
18
Zodiacal Light 7:55 – 8:55 p.m. West
19
Zodiacal Light 7:56 – 8:56 p.m. West
20
Zodiacal Light 7:57 – 8:57 p.m. West
21
Zodiacal Light 7:58 – 8:58 p.m. West
22 23 24 25
26 27 28 29 30 31  

April 2023
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7
Zodiacal Light 8:12 – 8:37 p.m. West
8
Zodiacal Light 8:13 – 9:13 p.m. West
9
Zodiacal Light 8:14 – 9:14 p.m. West
10
Zodiacal Light 8:14 – 9:14 p.m. West
11
Zodiacal Light 8:15 – 9:15 p.m. West
12
Zodiacal Light 8:16 – 9:16 p.m. West
13
Zodiacal Light 8:17 – 9:17 p.m. West
14
Zodiacal Light 8:18 – 9:18 p.m. West
15
Zodiacal Light 8:19 – 9:19 p.m. West
16
Zodiacal Light 8:20 – 9:20 p.m. West
17
Zodiacal Light 8:21 – 9:21 p.m. West
18
Zodiacal Light 8:22 – 9:22 p.m. West
19
Zodiacal Light 8:23 – 9:23 p.m. West
20
Zodiacal Light 8:24 – 9:24 p.m. West
21 22
23 24 25 26 27 28 29
30            

May 2023
SUN MON TUE WED THU FRI SAT
  1 2 3 4 5 6
7
Zodiacal Light 8:41 – 9:41 p.m. West
8
Zodiacal Light 8:42 – 9:42 p.m. West
9
Zodiacal Light 8:43 – 9:43 p.m. West
10
Zodiacal Light 8:44 – 9:44 p.m. West
11
Zodiacal Light 8:45 – 9:45 p.m. West
12
Zodiacal Light 8:46 – 9:46 p.m. West
13
Zodiacal Light 8:47 – 9:47 p.m. West
14
Zodiacal Light 8:48 – 9:48 p.m. West
15
Zodiacal Light 8:49 – 9:49 p.m. West
16
Zodiacal Light 8:50 – 9:50 p.m. West
17
Zodiacal Light 8:51 – 9:51 p.m. West
18
Zodiacal Light 8:52 – 9:52 p.m. West
19
Zodiacal Light 8:53 – 9:53 p.m. West
20
Zodiacal Light 8:54 – 9:54 p.m. West
21 22 23 24 25 26 27
28 29 30 31      

June 2023
SUN MON TUE WED THU FRI SAT
        1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30  

July 2023
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31          

August 2023
SUN MON TUE WED THU FRI SAT
    1 2 3 4 5
6 7 8 9 10 11 12
13 14
Zodiacal Light 3:59 – 4:18 a.m. East
15
Zodiacal Light 3:19 – 4:19 a.m. East
16
Zodiacal Light 3:20 – 4:20 a.m. East
17
Zodiacal Light 3:21 – 4:21 a.m. East
18
Zodiacal Light 3:22 – 4:22 a.m. East
19
Zodiacal Light 3:23 – 4:23 a.m. East
20
Zodiacal Light 3:24 – 4:24 a.m. East
21
Zodiacal Light 3:24 – 4:24 a.m. East
22
Zodiacal Light 3:25 – 4:25 a.m. East
23
Zodiacal Light 3:26 – 4:26 a.m. East
24
Zodiacal Light 3:27 – 4:27 a.m. East
25
Zodiacal Light 3:28 – 4:28 a.m. East
26
Zodiacal Light 3:29 – 4:29 a.m. East
27
Zodiacal Light 3:30 – 4:30 a.m. East
28
Zodiacal Light 3:31 – 4:31 a.m. East
29
Zodiacal Light 4:03 – 4:31 a.m. East
30 31    

September 2023
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5 6 7 8 9
10 11 12 13
Zodiacal Light 3:43 – 4:43 a.m. East
14
Zodiacal Light 3:44 – 4:44 a.m. East
15
Zodiacal Light 3:45 – 4:45 a.m. East
16
Zodiacal Light 3:46 – 4:46 a.m. East
17
Zodiacal Light 3:46 – 4:46 a.m. East
18
Zodiacal Light 3:47 – 4:47 a.m. East
19
Zodiacal Light 3:48 – 4:48 a.m. East
20
Zodiacal Light 3:49 – 4:49 a.m. East
21
Zodiacal Light 3:49 – 4:49 a.m. East
22
Zodiacal Light 3:50 – 4:50 a.m. East
23
Zodiacal Light 3:51 – 4:51 a.m. East
24
Zodiacal Light 3:51 – 4:51 a.m. East
25
Zodiacal Light 3:52 – 4:52 a.m. East
26
Zodiacal Light 3:53 – 4:53 a.m. East
27
Zodiacal Light 4:06 – 4:53 a.m. East
28 29 30

October 2023
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13
Zodiacal Light 4:04 – 5:04 a.m. East
14
Zodiacal Light 4:05 – 5:05 a.m. East
15
Zodiacal Light 4:06 – 5:06 a.m. East
16
Zodiacal Light 4:06 – 5:06 a.m. East
17
Zodiacal Light 4:07 – 5:07 a.m. East
18
Zodiacal Light 4:08 – 5:08 a.m. East
19
Zodiacal Light 4:08 – 5:08 a.m. East
20
Zodiacal Light 4:09 – 5:09 a.m. East
21
Zodiacal Light 4:10 – 5:10 a.m. East
22
Zodiacal Light 4:11 – 5:11 a.m. East
23
Zodiacal Light 4:11 – 5:11 a.m. East
24
Zodiacal Light 4:12 – 5:12 a.m. East
25
Zodiacal Light 4:13 – 5:13 a.m. East
26
Zodiacal Light 4:13 – 5:13 a.m. East
27 28
29 30 31        

November 2023
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12
Zodiacal Light 4:26 – 5:26 a.m. East
13
Zodiacal Light 4:27 – 5:27 a.m. East
14
Zodiacal Light 4:27 – 5:27 a.m. East
15
Zodiacal Light 4:28 – 5:28 a.m. East
16
Zodiacal Light 4:29 – 5:29 a.m. East
17
Zodiacal Light 4:30 – 5:30 a.m. East
18
Zodiacal Light 4:30 – 5:30 a.m. East
19
Zodiacal Light 4:31 – 5:31 a.m. East
20
Zodiacal Light 4:32 – 5:32 a.m. East
21
Zodiacal Light 4:33 – 5:33 a.m. East
22
Zodiacal Light 4:33 – 5:33 a.m. East
23
Zodiacal Light 4:34 – 5:34 a.m. East
24
Zodiacal Light 4:35 – 5:35 a.m. East
25
Zodiacal Light 5:13 – 5:36 a.m. East
26 27 28 29 30    

December 2023
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5 6 7 8 9
10 11
Zodiacal Light 4:47 – 5:47 a.m. East
12
Zodiacal Light 4:48 – 5:48 a.m. East
13
Zodiacal Light 4:48 – 5:48 a.m. East
14
Zodiacal Light 4:49 – 5:49 a.m. East
15
Zodiacal Light 4:50 – 5:50 a.m. East
16
Zodiacal Light 4:50 – 5:50 a.m. East
17
Zodiacal Light 4:51 – 5:51 a.m. East
18
Zodiacal Light 4:51 – 5:51 a.m. East
19
Zodiacal Light 4:52 – 5:52 a.m. East
20
Zodiacal Light 4:53 – 5:53 a.m. East
21
Zodiacal Light 4:53 – 5:53 a.m. East
22
Zodiacal Light 4:54 – 5:54 a.m. East
23
Zodiacal Light 4:54 – 5:54 a.m. East
24
Zodiacal Light 5:14 – 5:54 a.m. East
25 26 27 28 29 30
31            

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Zodiacal Light 2022

In 2022, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin (42° 58′ N, 90° 08′ W).

Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:

January 2022
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19
Zodiacal Light 6:36 – 6:38 p.m. West
20
Zodiacal Light 6:37 – 7:37 p.m. West
21
Zodiacal Light 6:38 – 7:38 p.m. West
22
Zodiacal Light 6:39 – 7:39 p.m. West
23
Zodiacal Light 6:40 – 7:40 p.m. West
24
Zodiacal Light 6:41 – 7:41 p.m. West
25
Zodiacal Light 6:42 – 7:42 p.m. West
26
Zodiacal Light 6:43 – 7:43 p.m. West
27
Zodiacal Light 6:44 – 7:44 p.m. West
28
Zodiacal Light 6:46 – 7:46 p.m. West
29
Zodiacal Light 6:47 – 7:47 p.m. West
30
Zodiacal Light 6:48 – 7:48 p.m. West
31
Zodiacal Light 6:49 – 7:49 p.m. West
         

February 2022
SUN MON TUE WED THU FRI SAT
    1
Zodiacal Light 6:50 – 7:50 p.m. West
2
Zodiacal Light 7:04 – 7:51 p.m. West
3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18
Zodiacal Light 7:10 – 7:51 p.m. West
19
Zodiacal Light 7:12 – 8:12 p.m. West
20
Zodiacal Light 7:13 – 8:13 p.m. West
21
Zodiacal Light 7:14 – 8:14 p.m. West
22
Zodiacal Light 7:15 – 8:15 p.m. West
23
Zodiacal Light 7:16 – 8:16 p.m. West
24
Zodiacal Light 7:18 – 8:18 p.m. West
25
Zodiacal Light 7:19 – 8:19 p.m. West
26
Zodiacal Light 7:20 – 8:20 p.m. West
27
Zodiacal Light 7:21 – 8:21 p.m. West
28
Zodiacal Light 7:22 – 8:22 p.m. West
         

March 2022
SUN MON TUE WED THU FRI SAT
    1
Zodiacal Light 7:24 – 8:24 p.m. West
2
Zodiacal Light 7:25 – 8:25 p.m. West
3
Zodiacal Light 7:26 – 8:26 p.m. West
4
Zodiacal Light 8:14 – 8:27 p.m. West
5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
Zodiacal Light 8:47 – 8:59 p.m. West
20
Zodiacal Light 8:48 – 9:48 p.m. West
21
Zodiacal Light 8:49 – 9:49 p.m. West
22
Zodiacal Light 8:51 – 9:51 p.m. West
23
Zodiacal Light 8:52 – 9:52 p.m. West
24
Zodiacal Light 8:53 – 9:53 p.m. West
25
Zodiacal Light 8:55 – 9:55 p.m. West
26
Zodiacal Light 8:56 – 9:56 p.m. West
27
Zodiacal Light 8:57 – 9:57 p.m. West
28
Zodiacal Light 8:59 – 9:59 p.m. West
29
Zodiacal Light 9:00 – 10:00 p.m. West
30
Zodiacal Light 9:02 – 10:02 p.m. West
31
Zodiacal Light 9:03 – 10:03 p.m. West
   

April 2022
SUN MON TUE WED THU FRI SAT
          1
Zodiacal Light 9:05 – 10:05 p.m. West
2
Zodiacal Light 9:11 – 10:06 p.m. West
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

May 2022
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31        

June 2022
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30    

July 2022
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31            

August 2022
SUN MON TUE WED THU FRI SAT
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25
Zodiacal Light 3:33 – 4:11 a.m. East
26
Zodiacal Light 3:35 – 4:35 a.m. East
27
Zodiacal Light 3:36 – 4:36 a.m. East
28
Zodiacal Light 3:38 – 4:38 a.m. East
29
Zodiacal Light 3:39 – 4:39 a.m. East
30
Zodiacal Light 3:41 – 4:41 a.m. East
31
Zodiacal Light 3:42 – 4:42 a.m. East
     

September 2022
SUN MON TUE WED THU FRI SAT
        1
Zodiacal Light 3:44 – 4:44 a.m. East
2
Zodiacal Light 3:45 – 4:45 a.m. East
3
Zodiacal Light 3:47 – 4:47 a.m. East
4
Zodiacal Light 3:48 – 4:48 a.m. East
5
Zodiacal Light 3:49 – 4:49 a.m. East
6
Zodiacal Light 3:51 – 4:51 a.m. East
7
Zodiacal Light 3:52 – 4:52 a.m. East
8
Zodiacal Light 3:57 – 4:54 a.m. East
9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
Zodiacal Light 4:14 – 5:14 a.m. East
25
Zodiacal Light 4:16 – 5:16 a.m. East
26
Zodiacal Light 4:17 – 5:17 a.m. East
27
Zodiacal Light 4:18 – 5:18 a.m. East
28
Zodiacal Light 4:19 – 5:19 a.m. East
29
Zodiacal Light 4:21 – 5:21 a.m. East
30
Zodiacal Light 4:22 – 5:22 a.m. East
 

October 2022
SUN MON TUE WED THU FRI SAT
            1
Zodiacal Light 4:23 – 5:23 a.m. East
2
Zodiacal Light 4:24 – 5:24 a.m. East
3
Zodiacal Light 4:25 – 5:25 a.m. East
4
Zodiacal Light 4:27 – 5:27 a.m. East
5
Zodiacal Light 4:28 – 5:28 a.m. East
6
Zodiacal Light 4:29 – 5:29 a.m. East
7
Zodiacal Light 4:30 – 5:30 a.m. East
8
Zodiacal Light 5:28 – 5:31 a.m. East
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23
Zodiacal Light 4:48 – 5:12 a.m. East
24
Zodiacal Light 4:50 – 5:50 a.m. East
25
Zodiacal Light 4:51 – 5:51 a.m. East
26
Zodiacal Light 4:52 – 5:52 a.m. East
27
Zodiacal Light 4:53 – 5:53 a.m. East
28
Zodiacal Light 4:54 – 5:54 a.m. East
29
Zodiacal Light 4:55 – 5:55 a.m. East
30
Zodiacal Light 4:56 – 5:56 a.m. East
31
Zodiacal Light 4:57 – 5:57 a.m. East
         

November 2022
SUN MON TUE WED THU FRI SAT
    1
Zodiacal Light 4:59 – 5:59 a.m. East
2
Zodiacal Light 5:00 – 6:00 a.m. East
3
Zodiacal Light 5:01 – 6:01 a.m. East
4
Zodiacal Light 5:02 – 6:02 a.m. East
5
Zodiacal Light 5:03 – 6:03 a.m. East
6
Zodiacal Light 4:35 – 5:04 a.m. East
7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22
Zodiacal Light 4:21 – 5:21 a.m. East
23
Zodiacal Light 4:22 – 5:22 a.m. East
24
Zodiacal Light 4:23 – 5:23 a.m. East
25
Zodiacal Light 4:24 – 5:24 a.m. East
26
Zodiacal Light 4:25 – 5:25 a.m. East
27
Zodiacal Light 4:26 – 5:26 a.m. East
28
Zodiacal Light 4:27 – 5:27 a.m. East
29
Zodiacal Light 4:28 – 5:28 a.m. East
30
Zodiacal Light 4:29 – 5:29 a.m. East
     

December 2022
SUN MON TUE WED THU FRI SAT
        1
Zodiacal Light 4:30 – 5:30 a.m. East
2
Zodiacal Light 4:31 – 5:31 a.m. East
3
Zodiacal Light 4:32 – 5:32 a.m. East
4
Zodiacal Light 4:33 – 5:33 a.m. East
5
Zodiacal Light 4:41 – 5:34 a.m. East
6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Zodiacal Light 2021

In 2021, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin (42° 58′ N, 90° 08′ W).

Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:

January 2021
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
Zodiacal Light 6:49 – 7:26 p.m. West
31
Zodiacal Light 6:50 – 7:50 p.m. West
           

February 2021
SUN MON TUE WED THU FRI SAT
  1
Zodiacal Light 6:51 – 7:51 p.m. West
2
Zodiacal Light 6:52 – 7:52 p.m. West
3
Zodiacal Light 6:53 – 7:53 p.m. West
4
Zodiacal Light 6:54 – 7:54 p.m. West
5
Zodiacal Light 6:56 – 7:56 p.m. West
6
Zodiacal Light 6:57 – 7:57 p.m. West
7
Zodiacal Light 6:58 – 7:58 p.m. West
8
Zodiacal Light 6:59 – 7:59 p.m. West
9
Zodiacal Light 7:00 – 8:00 p.m. West
10
Zodiacal Light 7:02 – 8:02 p.m. West
11
Zodiacal Light 7:03 – 8:03 p.m. West
12
Zodiacal Light 7:04 – 8:04 p.m. West
13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28
Zodiacal Light 7:23 – 7:36 p.m. West
           

March 2021
SUN MON TUE WED THU FRI SAT
  1
Zodiacal Light 7:25 – 8:25 p.m. West
2
Zodiacal Light 7:26 – 8:26 p.m. West
3
Zodiacal Light 7:27 – 8:27 p.m. West
4
Zodiacal Light 7:28 – 8:28 p.m. West
5
Zodiacal Light 7:29 – 8:29 p.m. West
6
Zodiacal Light 7:31 – 8:31 p.m. West
7
Zodiacal Light 7:32 – 8:32 p.m. West
8
Zodiacal Light 7:33 – 8:33 p.m. West
9
Zodiacal Light 7:34 – 8:34 p.m. West
10
Zodiacal Light 7:36 – 8:36 p.m. West
11
Zodiacal Light 7:37 – 8:37 p.m. West
12
Zodiacal Light 7:38 – 8:38 p.m. West
13
Zodiacal Light 7:40 – 8:40 p.m. West
14
Zodiacal Light 8:41 – 9:41 p.m. West
15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30
Zodiacal Light 9:03 – 10:03 p.m. West
31
Zodiacal Light 9:04 – 10:04 p.m. West
     

April 2021
SUN MON TUE WED THU FRI SAT
        1
Zodiacal Light 9:05 – 10:05 p.m. West
2
Zodiacal Light 9:07 – 10:07 p.m. West
3
Zodiacal Light 9:08 – 10:08 p.m. West
4
Zodiacal Light 9:10 – 10:10 p.m. West
5
Zodiacal Light 9:11 – 10:11 p.m. West
6
Zodiacal Light 9:13 – 10:13 p.m. West
7
Zodiacal Light 9:14 – 10:14 p.m. West
8
Zodiacal Light 9:16 – 10:16 p.m. West
9
Zodiacal Light 9:17 – 10:17 p.m. West
10
Zodiacal Light 9:19 – 10:19 p.m. West
11
Zodiacal Light 9:20 – 10:20 p.m. West
12
Zodiacal Light 9:22 – 10:22 p.m. West
13
Zodiacal Light 9:24 – 10:24 p.m. West
14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30  

May 2021
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31          

June 2021
SUN MON TUE WED THU FRI SAT
    1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30      

July 2021
SUN MON TUE WED THU FRI SAT
        1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

August 2021
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31        

September 2021
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6
Zodiacal Light 3:52 – 4:52 a.m. East
7
Zodiacal Light 3:53 – 4:53 a.m. East
8
Zodiacal Light 3:54 – 4:54 a.m. East
9
Zodiacal Light 3:56 – 4:56 a.m. East
10
Zodiacal Light 3:57 – 4:57 a.m. East
11
Zodiacal Light 3:58 – 4:58 a.m. East
12
Zodiacal Light 4:00 – 5:00 a.m. East
13
Zodiacal Light 4:01 – 5:01 a.m. East
14
Zodiacal Light 4:02 – 5:02 a.m. East
15
Zodiacal Light 4:04 – 5:04 a.m. East
16
Zodiacal Light 4:05 – 5:05 a.m. East
17
Zodiacal Light 4:06 – 5:06 a.m. East
18
Zodiacal Light 4:08 – 5:08 a.m. East
19
Zodiacal Light 4:59 – 5:09 a.m. East
20 21 22 23 24 25
26 27 28 29 30    

October 2021
SUN MON TUE WED THU FRI SAT
          1 2
3 4 5
Zodiacal Light 4:28 – 5:28 a.m. East
6
Zodiacal Light 4:30 – 5:30 a.m. East
7
Zodiacal Light 4:31 – 5:31 a.m. East
8
Zodiacal Light 4:32 – 5:32 a.m. East
9
Zodiacal Light 4:33 – 5:33 a.m. East
10
Zodiacal Light 4:34 – 5:34 a.m. East
11
Zodiacal Light 4:35 – 5:35 a.m. East
12
Zodiacal Light 4:37 – 5:37 a.m. East
13
Zodiacal Light 4:38 – 5:38 a.m. East
14
Zodiacal Light 4:39 – 5:39 a.m. East
15
Zodiacal Light 4:40 – 5:40 a.m. East
16
Zodiacal Light 4:41 – 5:41 a.m. East
17
Zodiacal Light 4:42 – 5:42 a.m. East
18
Zodiacal Light 5:03 – 5:43 a.m. East
19 20 21 22 23
24 25 26 27 28 29 30
31            

November 2021
SUN MON TUE WED THU FRI SAT
  1 2 3 4
Zodiacal Light 5:03 – 6:03 a.m. East
5
Zodiacal Light 5:04 – 6:04 a.m. East
6
Zodiacal Light 5:05 – 6:05 a.m. East
7
Zodiacal Light 4:06 – 5:06 a.m. East
8
Zodiacal Light 4:07 – 5:07 a.m. East
9
Zodiacal Light 4:08 – 5:08 a.m. East
10
Zodiacal Light 4:09 – 5:09 a.m. East
11
Zodiacal Light 4:10 – 5:10 a.m. East
12
Zodiacal Light 4:12 – 5:12 a.m. East
13
Zodiacal Light 4:13 – 5:13 a.m. East
14
Zodiacal Light 4:14 – 5:14 a.m. East
15
Zodiacal Light 4:15 – 5:15 a.m. East
16
Zodiacal Light 4:16 – 5:16 a.m. East
17
Zodiacal Light 5:06 – 5:17 a.m. East
18 19 20
21 22 23 24 25 26 27
28 29 30        

December 2021
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31  

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Zodiacal Light 2020

In 2020, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin (42° 58′ N, 90° 08′ W).

Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:

January 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9 10 11
12
Zodiacal Light 6:28 – 7:07 p.m. West
13
Zodiacal Light 6:29 – 7:29 p.m. West
14
Zodiacal Light 6:30 – 7:30 p.m. West
15
Zodiacal Light 6:31 – 7:31 p.m. West
16
Zodiacal Light 6:32 – 7:32 p.m. West
17
Zodiacal Light 6:33 – 7:33 p.m. West
18
Zodiacal Light 6:34 – 7:34 p.m. West
19
Zodiacal Light 6:35 – 7:35 p.m. West
20
Zodiacal Light 6:36 – 7:36 p.m. West
21
Zodiacal Light 6:37 – 7:37 p.m. West
22
Zodiacal Light 6:38 – 7:38 p.m. West
23
Zodiacal Light 6:39 – 7:39 p.m. West
24
Zodiacal Light 6:41 – 7:41 p.m. West
25
Zodiacal Light 6:42 – 7:42 p.m. West
26 27 28 29 30 31  
February 2020
SUN MON TUE WED THU FRI SAT
            1
2 3 4 5 6 7 8
9 10
Zodiacal Light 7:00 – 7:17 p.m. West
11
Zodiacal Light 7:01 – 8:01 p.m. West
12
Zodiacal Light 7:03 – 8:03 p.m. West
13
Zodiacal Light 7:04 – 8:04 p.m. West
14
Zodiacal Light 7:05 – 8:05 p.m. West
15
Zodiacal Light 7:06 – 8:06 p.m. West
16
Zodiacal Light 7:07 – 8:07 p.m. West
17
Zodiacal Light 7:09 – 8:09 p.m. West
18
Zodiacal Light 7:10 – 8:10 p.m. West
19
Zodiacal Light 7:11 – 8:11 p.m. West
20
Zodiacal Light 7:12 – 8:12 p.m. West
21
Zodiacal Light 7:13 – 8:13 p.m. West
22
Zodiacal Light 7:15 – 8:15 p.m. West
23
Zodiacal Light 7:16 – 8:16 p.m. West
24
Zodiacal Light 7:17 – 8:17 p.m. West
25 26 27 28 29

March 2020
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11
Zodiacal Light 8:37 – 9:37 p.m. West
12
Zodiacal Light 8:38 – 9:38 p.m. West
13
Zodiacal Light 8:39 – 9:39 p.m. West
14
Zodiacal Light 8:41 – 9:41 p.m. West
15
Zodiacal Light 8:42 – 9:42 p.m. West
16
Zodiacal Light 8:43 – 9:43 p.m. West
17
Zodiacal Light 8:45 – 9:45 p.m. West
18
Zodiacal Light 8:46 – 9:46 p.m. West
19
Zodiacal Light 8:47 – 9:47 p.m. West
20
Zodiacal Light 8:49 – 9:49 p.m. West
21
Zodiacal Light 8:50 – 9:50 p.m. West
22
Zodiacal Light 8:51 – 9:51 p.m. West
23
Zodiacal Light 8:53 – 9:53 p.m. West
24
Zodiacal Light 8:54 – 9:54 p.m. West
25
Zodiacal Light 8:55 – 9:55 p.m. West
26 27 28
29 30 31        

April 2020
SUN MON TUE WED THU FRI SAT
      1 2 3 4
5 6 7 8 9
Zodiacal Light 9:17 – 9:51 p.m. West
10
Zodiacal Light 9:19 – 10:19 p.m. West
11
Zodiacal Light 9:20 – 10:20 p.m. West
12
Zodiacal Light 9:22 – 10:22 p.m. West
13
Zodiacal Light 9:23 – 10:23 p.m. West
14
Zodiacal Light 9:25 – 10:25 p.m. West
15
Zodiacal Light 9:27 – 10:27 p.m. West
16
Zodiacal Light 9:28 – 10:28 p.m. West
17
Zodiacal Light 9:30 – 10:30 p.m. West
18
Zodiacal Light 9:31 – 10:31 p.m. West
19
Zodiacal Light 9:33 – 10:33 p.m. West
20
Zodiacal Light 9:35 – 10:35 p.m. West
21
Zodiacal Light 9:36 – 10:36 p.m. West
22
Zodiacal Light 9:38 – 10:38 p.m. West
23
Zodiacal Light 9:40 – 10:40 p.m. West
24
Zodiacal Light 9:41 – 10:41 p.m. West
25
26 27 28 29 30    
September 2020
SUN MON TUE WED THU FRI SAT
    1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16
Zodiacal Light 4:05 – 5:05 a.m. East
17
Zodiacal Light 4:06 – 5:06 a.m. East
18
Zodiacal Light 4:07 – 5:07 a.m. East
19
Zodiacal Light 4:09 – 5:09 a.m. East
20
Zodiacal Light 4:10 – 5:10 a.m. East
21
Zodiacal Light 4:11 – 5:11 a.m. East
22
Zodiacal Light 4:13 – 5:13 a.m. East
23
Zodiacal Light 4:14 – 5:14 a.m. East
24
Zodiacal Light 4:15 – 5:15 a.m. East
25
Zodiacal Light 4:16 – 5:16 a.m. East
26
Zodiacal Light 4:17 – 5:17 a.m. East
27
Zodiacal Light 4:19 – 5:19 a.m. East
28
Zodiacal Light 4:20 – 5:20 a.m. East
29
Zodiacal Light 4:27 – 5:21 a.m. East
30      

October 2020
SUN MON TUE WED THU FRI SAT
        1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16
Zodiacal Light 4:41 – 5:41 a.m. East
17
Zodiacal Light 4:42 – 5:42 a.m. East
18
Zodiacal Light 4:43 – 5:43 a.m. East
19
Zodiacal Light 4:44 – 5:44 a.m. East
20
Zodiacal Light 4:46 – 5:46 a.m. East
21
Zodiacal Light 4:47 – 5:47 a.m. East
22
Zodiacal Light 4:48 – 5:48 a.m. East
23
Zodiacal Light 4:49 – 5:49 a.m. East
24
Zodiacal Light 4:50 – 5:50 a.m. East
25
Zodiacal Light 4:51 – 5:51 a.m. East
26
Zodiacal Light 4:52 – 5:52 a.m. East
27
Zodiacal Light 4:53 – 5:53 a.m. East
28
Zodiacal Light 4:55 – 5:55 a.m. East
29
Zodiacal Light 5:24 – 5:56 a.m. East
30 31

November 2020
SUN MON TUE WED THU FRI SAT
1 2 3 4 5 6 7
8 9 10 11 12 13 14
Zodiacal Light 4:13 – 5:13 a.m. East
15
Zodiacal Light 4:15 – 5:15 a.m. East
16
Zodiacal Light 4:16 – 5:16 a.m. East
17
Zodiacal Light 4:17 – 5:17 a.m. East
18
Zodiacal Light 4:18 – 5:18 a.m. East
19
Zodiacal Light 4:19 – 5:19 a.m. East
20
Zodiacal Light 4:20 – 5:20 a.m. East
21
Zodiacal Light 4:21 – 5:21 a.m. East
22
Zodiacal Light 4:22 – 5:22 a.m. East
23
Zodiacal Light 4:23 – 5:23 a.m. East
24
Zodiacal Light 4:24 – 5:24 a.m. East
25
Zodiacal Light 4:25 – 5:25 a.m. East
26
Zodiacal Light 4:26 – 5:26 a.m. East
27
Zodiacal Light 4:27 – 5:27 a.m. East
28
Zodiacal Light 5:17 – 5:28 a.m. East
29 30          

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.

Zodiacal Light 2019

In this year of 2019, the best dates and times for observing the zodiacal light are listed below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin.

2019BeginEndDirection
Tue. Jan. 226:39 p.m.7:03 p.m.West
Wed. Jan. 236:40 p.m.7:40 p.m.West
Thu. Jan. 246:41 p.m.7:41 p.m.West
Fri. Jan. 256:42 p.m.7:42 p.m.West
Sat. Jan. 266:43 p.m.7:43 p.m.West
Sun. Jan. 276:44 p.m.7:44 p.m.West
Mon. Jan. 286:45 p.m.7:45 p.m.West
Tue. Jan. 296:46 p.m.7:46 p.m.West
Wed. Jan. 306:48 p.m.7:48 p.m.West
Thu. Jan. 316:49 p.m.7:49 p.m.West
Fri. Feb. 16:50 p.m.7:50 p.m.West
Sat. Feb. 26:51 p.m.7:51 p.m.West
Sun. Feb. 36:52 p.m.7:52 p.m.West
Mon. Feb. 46:53 p.m.7:53 p.m.West
Tue. Feb. 56:55 p.m.7:55 p.m.West
Wed. Feb. 67:09 p.m.7:56 p.m.West
Thu. Feb. 217:14 p.m.8:14 p.m.West
Fri. Feb. 227:15 p.m.8:15 p.m.West
Sat. Feb. 237:16 p.m.8:16 p.m.West
Sun. Feb. 247:17 p.m.8:17 p.m.West
Mon. Feb. 257:19 p.m.8:19 p.m.West
Tue. Feb. 267:20 p.m.8:20 p.m.West
Wed. Feb. 277:21 p.m.8:21 p.m.West
Thu. Feb. 287:22 p.m.8:22 p.m.West
Fri. Mar. 17:23 p.m.8:23 p.m.West
Sat. Mar. 27:25 p.m.8:25 p.m.West
Sun. Mar. 37:26 p.m.8:26 p.m.West
Mon. Mar. 47:27 p.m.8:27 p.m.West
Tue. Mar. 57:28 p.m.8:28 p.m.West
Wed. Mar. 67:30 p.m.8:30 p.m.West
Thu. Mar. 77:31 p.m.8:31 p.m.West
Fri. Mar. 88:01 p.m.8:32 p.m.West
Fri. Mar. 228:50 p.m.9:24 p.m.West
Sat. Mar. 238:52 p.m.9:52 p.m.West
Sun. Mar. 248:53 p.m.9:53 p.m.West
Mon. Mar. 258:54 p.m.9:54 p.m.West
Tue. Mar. 268:56 p.m.9:56 p.m.West
Wed. Mar. 278:57 p.m.9:57 p.m.West
Thu. Mar. 288:59 p.m.9:59 p.m.West
Fri. Mar. 299:00 p.m.10:00 p.m.West
Sat. Mar. 309:01 p.m.10:01 p.m.West
Sun. Mar. 319:03 p.m.10:03 p.m.West
Mon. Apr. 19:04 p.m.10:04 p.m.West
Tue. Apr. 29:06 p.m.10:06 p.m.West
Wed. Apr. 39:07 p.m.10:07 p.m.West
Thu. Apr. 49:09 p.m.10:09 p.m.West
Fri. Apr. 59:10 p.m.10:10 p.m.West
Sat. Apr. 69:12 p.m.10:12 p.m.West
Sun. Apr. 710:03 p.m.10:13 p.m.West
Thu. Aug. 293:39 a.m.4:39 a.m.East
Fri. Aug. 303:40 a.m.4:40 a.m.East
Sat. Aug. 313:42 a.m.4:42 a.m.East
Sun. Sep. 13:43 a.m.4:43 a.m.East
Mon. Sep. 23:45 a.m.4:45 a.m.East
Tue. Sep. 33:46 a.m.4:46 a.m.East
Wed. Sep. 43:48 a.m.4:48 a.m.East
Thu. Sep. 53:49 a.m.4:49 a.m.East
Fri. Sep. 63:50 a.m.4:50 a.m.East
Sat. Sep. 73:52 a.m.4:52 a.m.East
Sun. Sep. 83:53 a.m.4:53 a.m.East
Mon. Sep. 93:55 a.m.4:55 a.m.East
Tue. Sep. 103:56 a.m.4:56 a.m.East
Wed. Sep. 113:57 a.m.4:57 a.m.East
Thu. Sep. 124:52 a.m.4:59 a.m.East
Fri. Sep. 275:11 a.m.5:18 a.m.East
Sat. Sep. 284:19 a.m.5:19 a.m.East
Sun. Sep. 294:20 a.m.5:20 a.m.East
Mon. Sep. 304:21 a.m.5:21 a.m.East
Tue. Oct. 14:23 a.m.5:23 a.m.East
Wed. Oct. 24:24 a.m.5:24 a.m.East
Thu. Oct. 34:25 a.m.5:25 a.m.East
Fri. Oct. 44:26 a.m.5:26 a.m.East
Sat. Oct. 54:27 a.m.5:27 a.m.East
Sun. Oct. 64:29 a.m.5:29 a.m.East
Mon. Oct. 74:30 a.m.5:30 a.m.East
Tue. Oct. 84:31 a.m.5:31 a.m.East
Wed. Oct. 94:32 a.m.5:32 a.m.East
Thu. Oct. 104:33 a.m.5:33 a.m.East
Fri. Oct. 114:43 a.m.5:34 a.m.East
Sat. Oct. 264:51 a.m.5:19 a.m.East
Sun. Oct. 274:53 a.m.5:53 a.m.East
Mon. Oct. 284:54 a.m.5:54 a.m.East
Tue. Oct. 294:55 a.m.5:55 a.m.East
Wed. Oct. 304:56 a.m.5:56 a.m.East
Thu. Oct. 314:57 a.m.5:57 a.m.East
Fri. Nov. 14:58 a.m.5:58 a.m.East
Sat. Nov. 24:59 a.m.5:59 a.m.East
Sun. Nov. 34:01 a.m.5:01 a.m.East
Mon. Nov. 44:02 a.m.5:02 a.m.East
Tue. Nov. 54:03 a.m.5:03 a.m.East
Wed. Nov. 64:04 a.m.5:04 a.m.East
Thu. Nov. 74:05 a.m.5:05 a.m.East
Fri. Nov. 84:06 a.m.5:06 a.m.East
Sat. Nov. 94:07 a.m.5:07 a.m.East
Sun. Nov. 104:34 a.m.5:08 a.m.East
Sun. Nov. 244:23 a.m.4:27 a.m.East
Mon. Nov. 254:24 a.m.5:24 a.m.East
Tue. Nov. 264:25 a.m.5:25 a.m.East
Wed. Nov. 274:26 a.m.5:26 a.m.East
Thu. Nov. 284:27 a.m.5:27 a.m.East
Fri. Nov. 294:28 a.m.5:28 a.m.East
Sat. Nov. 304:29 a.m.5:29 a.m.East
Sun. Dec. 14:30 a.m.5:30 a.m.East
Mon. Dec. 24:31 a.m.5:31 a.m.East
Tue. Dec. 34:32 a.m.5:32 a.m.East
Wed. Dec. 44:33 a.m.5:33 a.m.East
Thu. Dec. 54:34 a.m.5:34 a.m.East
Fri. Dec. 64:35 a.m.5:35 a.m.East
Sat. Dec. 74:35 a.m.5:35 a.m.East
Sun. Dec. 84:36 a.m.5:36 a.m.East
Mon. Dec. 94:37 a.m.5:37 a.m.East
Tue. Dec. 105:29 a.m.5:38 a.m.East

The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.

If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:

\cos I = \cos \varepsilon \sin \phi-\sin \varepsilon \cos \phi \sin \theta

where I is the angle between the ecliptic and the horizon, ε is  the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).

Here’s a SAS program I wrote to do these calculations:

References
Meeus, J. Astronomical Algorithms. 2nd ed., Willmann-Bell, 1998, p. 99.