# 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.

## 4 thoughts on “Zodiacal Light 2020”

1. Dr. Amin Uddin Ahmed says:

Dr. Mr. Oesper,
It has been about a year since I heard from you. How are you? In lockdown?
Any news regarding any video of Zodiacal light take for the period when it is brightest to its disappearance? If so any details?
With best regards?

1. Dear Dr. Ahmed,

We are doing OK here but are locked down as well. There is unwise eagerness to open everything back up too soon, but until there is an effective treatment or a vaccine for COVID-19—or until deaths and positive cases in the U.S. drop to zero—we will continue to stay home as much as possible no matter what others are doing.

https://cosmicreflections.skythisweek.info/2020/04/30/another-covid-19-map/

I don’t have a good answer to your question except to say that the amount of time the evening zodiacal light is visible from when it is brightest (the end of astronomical twilight, when the Sun is 18° below the horizon) to its disappearance will depend on the angle the ecliptic makes with the horizon (the more perpendicular the better, and that depends on the date and your latitude) as well as atmospheric conditions and the amount of light pollution. I have found some time lapse videos of the zodiacal light setting, but they do not show the time on the video frames which would make it easier to determine the time interval.

https://www.eso.org/public/videos/zodiacallighttimelapse/

In a very dark sky and under ideal atmospheric conditions, it is possible to see the zodiacal band going from horizon to horizon across the sky (along the ecliptic) all night long, and the gegenschein at the antisolar point in the sky. I have seen this (the zodiacal band and the gegenschein) only a couple of times. It is truly a beautiful sight to behold.

Take care and be safe!

1. Dr. Amin Uddin Ahmed says:

Dear Mr Oesper,
Thank you so much for your prompt reply. We pray that the Covid-19
ends soon in the world and normalcy returns.
Perhaps I didn’t express myself properly when I referred to the duration after which the Zodiacal light disappears from the time it is brightest. I meant the disappearance in the morning due to light of the sun.
With best regards and best wishes,
Dr. Amin Uddin Ahmed

1. Ah, please forgive me for misinterpreting your question, Dr. Ahmed. So the observational approach would be to take a time-lapse movie of the zodiacal light cone from the beginning of astronomical twilight in the morning (when the Sun is 18° below the horizon) until morning twilight overwhelms the zodiacal light. To model this phenomenon would certainly warrant a paper in an astronomical journal! The surface brightness of the zodiacal light varies rapidly with both solar elongation (distance in degrees from the Sun), ecliptic latitude, and the terrestrial latitude of the observer (the zodiacal light is brighter nearer the equator). The morning twilight sky brightness also varies rapidly with solar elongation and solar depression angle (angular distance of the Sun below the horizon). I would imagine that for each point on the sky, the zodiacal light would become invisible when the twilight surface brightness exceeds the zodiacal light surface brightness.

Thank you for your question which encouraged me to think more deeply about this issue. Besides just making a time-lapse movie, quantitative measurements of the video frames would require a similar approach to what is done with light pollution measurements.