In this year of 2018, the best dates and times for observing the zodiacal light are listed below. The sky must be very clear. The specific times listed are for Dodgeville, Wisconsin.
|Fri. Feb. 2||6:52 p.m.||7:52 p.m.||West|
|Sat. Feb. 3||6:53 p.m.||7:53 p.m.||West|
|Sun. Feb. 4||6:54 p.m.||7:54 p.m.||West|
|Mon. Feb. 5||6:55 p.m.||7:55 p.m.||West|
|Tue. Feb. 6||6:57 p.m.||7:57 p.m.||West|
|Wed. Feb. 7||6:58 p.m.||7:58 p.m.||West|
|Thu. Feb. 8||6:59 p.m.||7:59 p.m.||West|
|Fri. Feb. 9||7:00 p.m.||8:00 p.m.||West|
|Sat. Feb. 10||7:01 p.m.||8:01 p.m.||West|
|Sun. Feb. 11||7:02 p.m.||8:02 p.m.||West|
|Mon. Feb. 12||7:04 p.m.||8:04 p.m.||West|
|Tue. Feb. 13||7:05 p.m.||8:05 p.m.||West|
|Wed. Feb. 14||7:06 p.m.||8:06 p.m.||West|
|Thu. Feb. 15||7:07 p.m.||8:07 p.m.||West|
|Fri. Feb. 16||7:08 p.m.||8:08 p.m.||West|
|Sat. Mar. 3||7:27 p.m.||7:59 p.m.||West|
|Sun. Mar. 4||7:28 p.m.||8:28 p.m.||West|
|Mon. Mar. 5||7:29 p.m.||8:29 p.m.||West|
|Tue. Mar. 6||7:30 p.m.||8:30 p.m.||West|
|Wed. Mar. 7||7:32 p.m.||8:32 p.m.||West|
|Thu. Mar. 8||7:33 p.m.||8:33 p.m.||West|
|Fri. Mar. 9||7:34 p.m.||8:34 p.m.||West|
|Sat. Mar. 10||7:35 p.m.||8:35 p.m.||West|
|Sun. Mar. 11||8:37 p.m.||9:37 p.m.||West|
|Mon. Mar. 12||8:38 p.m.||9:38 p.m.||West|
|Tue. Mar. 13||8:39 p.m.||9:39 p.m.||West|
|Wed. Mar. 14||8:41 p.m.||9:41 p.m.||West|
|Thu. Mar. 15||8:42 p.m.||9:42 p.m.||West|
|Fri. Mar. 16||8:43 p.m.||9:43 p.m.||West|
|Sat. Mar. 17||8:44 p.m.||9:44 p.m.||West|
|Sun. Mar. 18||8:46 p.m.||9:46 p.m.||West|
|Mon. Mar. 19||9:38 p.m.||9:47 p.m.||West|
|Mon. Apr. 2||9:06 p.m.||9:56 p.m.||West|
|Tue. Apr. 3||9:08 p.m.||10:08 p.m.||West|
|Wed. Apr. 4||9:09 p.m.||10:09 p.m.||West|
|Thu. Apr. 5||9:11 p.m.||10:11 p.m.||West|
|Fri. Apr. 6||9:12 p.m.||10:12 p.m.||West|
|Sat. Apr. 7||9:14 p.m.||10:14 p.m.||West|
|Sun. Apr. 8||9:15 p.m.||10:15 p.m.||West|
|Mon. Apr. 9||9:17 p.m.||10:17 p.m.||West|
|Tue. Apr. 10||9:18 p.m.||10:18 p.m.||West|
|Wed. Apr. 11||9:20 p.m.||10:20 p.m.||West|
|Thu. Apr. 12||9:21 p.m.||10:21 p.m.||West|
|Fri. Apr. 13||9:23 p.m.||10:23 p.m.||West|
|Sat. Apr. 14||9:25 p.m.||10:25 p.m.||West|
|Sun. Apr. 15||9:26 p.m.||10:26 p.m.||West|
|Mon. Apr. 16||9:28 p.m.||10:28 p.m.||West|
|Tue. Apr. 17||9:43 p.m.||10:29 p.m.||West|
|Thu. Aug. 9||3:08 a.m.||3:44 a.m.||East|
|Fri. Aug. 10||3:09 a.m.||4:09 a.m.||East|
|Sat. Aug. 11||3:11 a.m.||4:11 a.m.||East|
|Sun. Aug. 12||3:13 a.m.||4:13 a.m.||East|
|Mon. Aug. 13||3:14 a.m.||4:14 a.m.||East|
|Tue. Aug. 14||3:16 a.m.||4:16 a.m.||East|
|Wed. Aug. 15||3:18 a.m.||4:18 a.m.||East|
|Thu. Aug. 16||3:19 a.m.||4:19 a.m.||East|
|Fri. Aug. 17||3:21 a.m.||4:21 a.m.||East|
|Sat. Aug. 18||3:22 a.m.||4:22 a.m.||East|
|Sun. Aug. 19||3:24 a.m.||4:24 a.m.||East|
|Mon. Aug. 20||3:26 a.m.||4:26 a.m.||East|
|Tue. Aug. 21||3:27 a.m.||4:27 a.m.||East|
|Wed. Aug. 22||3:29 a.m.||4:29 a.m.||East|
|Thu. Aug. 23||3:30 a.m.||4:30 a.m.||East|
|Fri. Aug. 24||4:20 a.m.||4:32 a.m.||East|
|Sat. Sep. 8||3:54 a.m.||4:54 a.m.||East|
|Sun. Sep. 9||3:55 a.m.||4:55 a.m.||East|
|Mon. Sep. 10||3:57 a.m.||4:57 a.m.||East|
|Tue. Sep. 11||3:58 a.m.||4:58 a.m.||East|
|Wed. Sep. 12||3:59 a.m.||4:59 a.m.||East|
|Thu. Sep. 13||4:01 a.m.||5:01 a.m.||East|
|Fri. Sep. 14||4:02 a.m.||5:02 a.m.||East|
|Sat. Sep. 15||4:03 a.m.||5:03 a.m.||East|
|Sun. Sep. 16||4:05 a.m.||5:05 a.m.||East|
|Mon. Sep. 17||4:06 a.m.||5:06 a.m.||East|
|Tue. Sep. 18||4:07 a.m.||5:07 a.m.||East|
|Wed. Sep. 19||4:09 a.m.||5:09 a.m.||East|
|Thu. Sep. 20||4:10 a.m.||5:10 a.m.||East|
|Fri. Sep. 21||4:11 a.m.||5:11 a.m.||East|
|Sat. Sep. 22||4:12 a.m.||5:12 a.m.||East|
|Sun. Sep. 23||5:07 a.m.||5:14 a.m.||East|
|Sun. Oct. 7||4:30 a.m.||5:04 a.m.||East|
|Mon. Oct. 8||4:32 a.m.||5:32 a.m.||East|
|Tue. Oct. 9||4:33 a.m.||5:33 a.m.||East|
|Wed. Oct. 10||4:34 a.m.||5:34 a.m.||East|
|Thu. Oct. 11||4:35 a.m.||5:35 a.m.||East|
|Fri. Oct. 12||4:36 a.m.||5:36 a.m.||East|
|Sat. Oct. 13||4:37 a.m.||5:37 a.m.||East|
|Sun. Oct. 14||4:39 a.m.||5:39 a.m.||East|
|Mon. Oct. 15||4:40 a.m.||5:40 a.m.||East|
|Tue. Oct. 16||4:41 a.m.||5:41 a.m.||East|
|Wed. Oct. 17||4:42 a.m.||5:42 a.m.||East|
|Thu. Oct. 18||4:43 a.m.||5:43 a.m.||East|
|Fri. Oct. 19||4:44 a.m.||5:44 a.m.||East|
|Sat. Oct. 20||4:45 a.m.||5:45 a.m.||East|
|Sun. Oct. 21||4:47 a.m.||5:47 a.m.||East|
|Mon. Oct. 22||4:57 a.m.||5:48 a.m.||East|
On the February, March, and April evenings listed above, you will see a broad, faint band of light extending upwards from the western horizon, sloping a little to the left, and reaching nearly halfway to the top of the sky.
On the August, September, and October mornings listed above, you will see a broad, faint band of light extending upwards from the eastern horizon, sloping a little to the right, and reaching nearly halfway to the top of the sky.
It is essential that your view is not spoiled by nearby streetlights, parking lot lights, or dusk-to-damn insecurity lights, nor any city to the west (Feb-Apr) or east (Aug-Oct). Give your eyes a few minutes to adjust to the darkness. Slowly sweeping your eyes back and forth from southwest to northwest (Feb-Apr) or northeast to southeast (Aug-Oct) will help you spot the zodiacal light band. Once spotted, you should be able to see it without moving your head.
On the February, March, and April evenings listed above, the zodiacal light is best seen right at the end of evening twilight, and remains visible for an hour or so after that.
On the August, September, and October mornings listed above, the zodiacal light is best seen about an hour or so before the beginning of morning twilight, right up to the beginning of morning twilight.
22 thoughts on “Zodiacal Light 2018”
It is nice to see such a prediction about Zodiacal lights.
Can you please calculate the local times when such lights will be visible from places at the Tropic of Cancer and at Equator?
Can you share the formula for such calculations?
Dear Dr. Ahmed,
The best times to see the zodiacal light is when the ecliptic is most nearly perpendicular to the horizon, right after the end of astronomical twilight (Sun altitude -18°) in the evening, and right before the beginning of astronomical twilight in the morning. The following diagrams will show you the angle the ecliptic makes with the horizon on the 15th of each month of the year for latitudes 43°N (Dodgeville, WI), 23°26’12.8″N (Tropic of Cancer), and 0° (The Equator).
Zodiacal Light – A.M.
Zodiacal Light – P.M.
I was surprised to find that the best mid-months for morning zodiacal light is actually September, October, and November (and not so much August) at both latitudes 43°N and 23°N, though you can see the ecliptic makes a much more perpendicular angle with the horizon at 23°N. So, along the Tropic of Cancer, the zodiacal light will be easier to see in other months, too. When I lived in Alpine, Texas (latitude 30°N), I indeed noticed that the zodiacal light was more impressive than my experiences seeing it further north.
Similarly, the best mid-months for evening zodiacal light is actually January, February, and March (and not so much April) at both latitudes 43°N and 23°N. Again, the ecliptic makes a steeper angle with the horizon at the Tropic of Cancer.
The situation at the Equator is a bit different. January and July are the best months for morning zodiacal light there, and May-June and November-December for the evening zodiacal light.
The other factor to consider (besides minimal to no light pollution) for picking zodiacal light viewing times is no lunar interference. Any good planetarium software will allow you to find astronomical twilight for any date when the Moon isn’t above the horizon. I used Voyager 4.5. If you want to calculate the times when the Sun is 18° below the horizon and the Moon is below the horizon, there are several good books by Jean Meeus (and others) that show you how. I myself wrote such a program in Applesoft BASIC on an Apple ][+ computer back in 1981, and I have a version of it today written in SAS that I use to generate my Dark Skies page each month.
In conclusion, I now realize that the best months for observing the zodiacal light this year perhaps should have excluded April and included January, and excluded August and included November. Of course, this will vary slightly from year to year depending on what time of the month presents moonless skies. When I publish Zodiacal Light 2019 next January, I will do a more careful analysis to make sure I get it right!
I am grateful to you for your prompt reply. I found your reply very informative. Allow me to ask you as to what does the abbreviation ST stand for in you diagrams? Does LDT stand for Local Daylight Time? You have shown three lines for each date for three different times. What is the significance of the times chosen? Do these times correspond to the beginning, middle and end of the appearance of Zodiacal light? How many degrees below the horizon is sun at these times? Does the Zodiacal light disappear and sky becomes dark again before the appearance of astronomical twilight at 18 degrees, or because of the relatively brighter astronomical twilight, zodiacal light ceases to be visible?
I do have Stellarium software on my computer but it does not show zodiacal lights. I will try to download Voyager software you suggested but at 86 years of age I take time doing things.
Again let me express my gratitude to you for reply.
With best regards,
Dr. Amin Uddin Ahmed
Greetings Dr. Ahmed,
ST is a label in Voyager that should actually be LST which is local sidereal time. It is the right ascension of objects on the celestial meridian at that moment in time for that location.
LDT does indeed stand for Local Daylight Time, and LMT stands for Local Mean Time for the times of the year when daylight saving time is not in effect.
The times chosen are the moment when astronomical twilight begins in the a.m. diagrams, and when astronomical twilight ends in the p.m. diagrams. In both cases, the Sun is 18 degrees below the horizon at this moment.
The zodiacal light is best seen right when the Sun is 18 degrees below the horizon. In my original article, I have arbitrarily chosen a period of one hour before astronomical twilight begins to the beginning of astronomical twilight as the best time to observe the morning zodiacal light. Likewise, from the end of astronomical twilight until one hour later for the evening zodiacal light. Incidentally, astronomical twilight is defined to be when the Sun is between 18 and 12 degrees below the (geometric) horizon. When the Sun is less than 18 degrees below the horizon twilight washes out the zodiacal light. So you are correct in stating that the zodiacal light ceases to be visible because of the relatively brighter astronomical twilight.
Thank you for your questions!
In continuation of my reply to you about an hour ago I would like to add that using MoonCalc6 softwares, the altitude values for Dodgeville for September 15th for 4:03 and 5:03 am, came to be -35.701 and 27.542 respectively. Any comment on correctness of these values?
With the Voyager 4.5 software, on September 15, 2018 I find a Sun altitude of -35.843° at 3:03 a.m. CDT, -27.705° at 4:03 a.m. CDT and –18.069° at 5:03 a.m. CDT at Dodgeville.
Thank you once again for your informative reply.
I forgot to mention that the altitudes that I calculated using MoonCalc6 software were those of sun and not of moon. I wonder if I arrived at the right values. I wanted to send you screenshots of MoonCalc6 results but didn’t know how to incorporate those in the reply box. (My usual help, my grand son, is away these days). If I knew your email I could have sent the attachment.
Incidentally, I do have Starwalk software on my mobile as well as iPad and this program also displays ecliptic. Your reply about the ecliptic angle gave me the idea of using Starwalk. Thanks once again. With regards.
I wonder as to how long ( minutes or hours) the Zodiacal light was visible to you before the astronomical twilight began?
The visibility of the zodiacal light is always best right before the beginning of astronomical twilight (in the a.m.) or right after the end of astronomical twilight (in the p.m.). The zodiacal dust band is most dense and brightest closest to the Sun, and at these moments you are seeing the closest part of the zodiacal band to the Sun without twilight interference. When the Sun is more than 18° below the horizon, you can still see the zodiacal light, but you are seeing the part of it that is further away from the Sun, so it will be fainter. The interval of visibility of the zodiacal light depends on the transparency of the atmosphere, the darkness of the sky (i.e. freedom from light pollution), and the angle the ecliptic makes with the horizon—the more perpendicular the better—and that depends on both your latitude and the time of year. I have rather arbitrarily chosen (but based on my own experience) one hour before twilight begins as the best time to begin looking for the zodiacal light in the morning, and you should normally be able to see the zodiacal light in the evening until at least one hour after the end of astronomical twilight. However, in very dark locations and under ideal atmospheric conditions it is possible to detect the zodiacal light crossing the entire sky (along the ecliptic) and even the faint glowing region 180° from the Sun called the gegenschein, which I have only seen a couple of times.
Thank you for the detailed reply.
I hope you are in good health. I am grateful for the valuable information you gave me about the zodiacal lights last year in May.
I am here to bother you again and learn from your experience.
Does the zodiacal light remain visible to the naked eye in the morning after the beginning of astronomical twilight and if so for how many minutes ?Likewise in case of evening zodiacal light, is it visible to naked eye even before sun has
reached 18 degrees below horizon and if so at what angle?
Dear Dr. Ahmed,
Thank you for your kind comments. As twilight brightens in the morning, it will be very difficult to see the faint glow of the zodiacal light against it. You might be able to detect it until the Sun is about 15 degrees below the horizon. Assuming the ideal situation where the ecliptic is perpendicular to your eastern horizon, you might be able to see the zodiacal light up to 12 minutes after the beginning of astronomical twilight with averted vision. The closer you are to the equator and the steeper the angle of the ecliptic relative to your (preferably flat) horizon, the drier and clearer the atmosphere, and the higher your elevation, the better the chances that you will be able to detect the zodiacal light during the earliest stages of morning twilight. The zodiacal light will be a cone of light stretching along the ecliptic, whereas morning twilight will be round and centered on the location of the Sun below the horizon.
It is certainly possible to see the zodiacal light when the Sun is more than 18 degrees below the horizon. In fact, under ideal conditions, you can even trace the zodiacal band clear across the sky along the ecliptic, with the very faint glow of the Gegenschein around the anti-solar point.
Here is a quite descriptive comment by John Bortle, originator of what is now called the Bortle scale, on April 10, 2008:
“Most unfortunately, the great majority of today’s amateur astronomers live in areas whose skies are sufficiently compromised by light pollution as to render the Zodiacal Light all but undetectable. But this was not always so. In the post-war years up through the 1960s, it was possible to see the ZL quite well even from the outer suburbs of many of the larger cities. From the rural areas only a bit more distant, it was a truly wonderful sight.
“During the 1970s, from my residence about 75 miles north of NYC, the Zodiacal Light was a striking feature on most any moonless spring evening, or autumn morning. This huge, tapering, cone of light would stretch upwards into the heavens 60-degrees, or more, with its core glowing brightly enough as to extinguish many of the fainter stars within it. One feature I always found particularly striking was the ZL’s color – a decidedly “warm” hue that contrasted dramatically with the cold, blue-white light of the milky way whenever the two were situated more-or-less in the same part of the sky.
“On many evenings the ZL was not the only strange glowing feature I would note in the heavens. When appropriately situated, I could generally spot an elongated, softly glowing patch of mist well south of zenith around local midnight, which was the Gegenschein. And on the very best nights, more often than not during the pre-dawn hours when even the minimal local lighting had been extinguished, the light-bridge of the Zodiacal Band could be detected with averted vision joining the ZL cone in the eastern sky with the Gegenschein well down in the west.
“Sadly, the explosive growth of urban sprawl in recent decades has robbed most of us in the northeastern U.S. (and elsewhere) of any majestic views of the Zodiacal Light, Gegenschein, or the even more elusive Zodiacal Band. Even at my distance from the major metropolitan centers, the skies have become so bright that these celestial features live on for me only in memories.”
Thank you Mr. Oesper, for your detailed reply. Do I understand correctly from your reply (copy below) that steeper the angle of ecliptic with horizon, the better are chances for observation of Zodiacal light?
“The closer you are to the equator and the steeper the angle of the ecliptic relative to your (preferably flat) horizon, the drier and clearer the atmosphere, and the higher your elevation, the better the chances that you will be able to detect the zodiacal light during the earliest stages of morning twilight”
But in your reply of 29th May last year you said that chances are better for viewing if ecliptic is less steep and more perpendicular.
“The interval of visibility of the zodiacal light depends on the transparency of the atmosphere, the darkness of the sky (i.e. freedom from light pollution), and the angle the ecliptic makes with the horizon—the more perpendicular the better”
The time lapse video from midnight to dawn, entitled “Emerging False Dawn”showing degrees and time stops when the sun is 18 degrees below horizon.
I wonder if there is a video of Eastern horizon beginning with the beginning of astronomical twilight to the end of astronomical twilight showing morning Zodiacal light, with date and time. This would show the disappearance of Zodiacal light and the earliest appearance of faint horizontal light along the horizon with time.
I thank you once again. You have been a great help.
Dr. Ahmed, by steeper I meant “more perpendicular”. Sorry for the confusion. I should have chosen my words more carefully: the more perpendicular the ecliptic is to the horizon, the easier it will be to see the zodiacal light.
I think I found the “Emerging False Dawn” video you were referring to:
You might find this video about the zodiacal light to be interesting as well:
There is certainly an opportunity here for someone to record a time-lapse video of the zodiacal light in the east, starting say an hour before the beginning of astronomical twilight (sun altitude -18˚) and ending, say, at the beginning of nautical twilight (sun altitude -12˚). By then, morning twilight will be so bright that it would render the zodiacal light completely invisible, I think. Our next opportunity to record such a video under favorable conditions here in the north will be August 29th of this year.
Thank you, Mr. Oesper for your very prompt reply and for clarifying my misunderstanding. I did see the video
“Emerging False Dawn” but it stops at -18 degrees. You have mentioned, the next opportunity to record Zodiacal light and the period of Astronomical twilight, is on 29th August this year in your latitudes,
( though according to ESO Cast82, it is visible in Atacama desert on every moonless morning and evening because of the darkness of sky there).
If possible, the video recording may be done both on time lapse as well as normal procedures having an imprint of date and time as well. Many iPhone Apps provide this feature. The coordinates of the place will provide the angular position of sun. The recording may be continued from -21 to -12 degrees so as not to miss the Zodiacal light near -18 degrees.
It may interesting to note if the observer of the Zodiacal light, observes a slight darkness for few moments just after the disappearance of the Zodiacal light as some people have experienced. If so it will be in line with the views expressed by Prof. David Heeger in Perception 30 Lecture Notes: Brightness, cns,nyu.edu., where he says that two gray squares of same darkness will appear different in bright and dark background.
https://www.cns.nyu.edu/~david/courses/perception/lecturenotes/brightness-contrast/brightness-slides/Slide4.jpg. The Zodiacal light will appear bright in the background of dark night but will appear dark in the background of astronomical twilight.
I will once again request you to see for yourself the difference in darkness of the two squares of same darkness placed in bright and dark background referred to above.
With best regards.
In continuation of my reply posted about 40 minutes ago, I would like to add that in spite of long search, I have not been able to find one video on the disappearance of the Zodiacal light as astronomical twilight increases, showing the time of disappearance or the position is sun relative to horizon. Hence such a video may be a valuable addition to the scientific literature. Likewise the video of the earliest appearance of Zodiacal light in evening with respect to sun’s angle below horizon may be interesting.
Dear Dr. Ahmed,
Thank you for sharing the link to the brightness contrast slide and information about how the zodiacal light changes from bright to dark as twilight grows before the zodiacal light completely disappears. Before your comments, I had never considered the possibility. I shall make a point to look for that in the future! This brightness contrast phenomenon also explains why sunspots appear to be dark.
I agree that obtaining video of the zodiacal light going from bright to dark and then disappearing in the growing twilight (or vice versa in the evening) would be quite interesting and of scientific value. Perhaps one of our readers here can give this a try and report back the results. I myself may be able to obtain such a video at some point in the future (especially after retirement), though I will probably have to travel to a less light-polluted region, and further south than my present latitude of 43˚N. I will definitely keep this top of mind!
When I lived in Alpine, TX (just north of latitude 30˚ N), I was very fortunate to see the Gegenschein and the zodiacal band circumscribing the sky once, on a very clear and dark night just a few miles south of town. I would love to see that again!
Dear Mr. Oesper,
Thank you for endorsing the idea that if a feeling of darkness arises after brightness, it is worth exploring and may be it is due to the Optical illusion explained beautifully in the link.
You mentioned about retirement. When is it? I am enjoying it since 1995.
With best regards,
Dr. A. U. Ahmed
Hello Dr. Ahmed, I hope to retire in 2022 and then I will have much more time for astronomy and writing! Haven’t decided yet whether to fully retire then, or cut back to half-time until 2026.
Dear Mr. Oesper,
It has been about a year since I heard from you. I hope you are in good health. We are in a lockdown due to Covid-19. How about you?
I wonder if anyone has made any video of the Zodiacal light during the period when it is brightest (at the beginning of Astronomical Twilight) to the time when it is no more visible.
If so any details regarding the time interval (or angle of sun below horizon) from brightest to invisible Zodiacal light.
With best regards.
Dr. Amin Uddin Ahmed
Good day Mr. Oesper,
I read through the comments and wanted to know if it is possible to see a glimpse of the zodiacal light in majority of the countries irrespective of latitude.
Greetings, Ali Ahmed,
Yes, it is possible to see the zodiacal light from the majority of countries, though the closer the observer is to the equator, the brighter the zodiacal light will be and the more nights during the year one will be able to see it. The key determinant for visibility (besides observing from a location with little to no light pollution) is the angle the ecliptic (plane of the Earth’s orbit around the Sun) makes with the horizon. This varies throughout the year and by latitude for any given night. The steeper the angle the ecliptic makes with the horizon (perpendicular is ideal), the more visible the zodiacal light will be.
If you are interested in calculating the angle the ecliptic makes with your horizon for any date, time, and location, you can use the formula given at the bottom of the following article.
From personal experience, I was often able to see the zodiacal light from Iowa (latitude ~ 42˚ N), though when I lived in the Big Bend region of West Texas (latitude ~ 30˚ N) it was definitely brighter and could be seen on more nights during the year.
Hope this helps!