Transit Times of Jupiter’s Great Red Spot

Jupiter as seen by the Cassini spacecraft
NASA / JPL / University of Arizona

Jupiter's most famous feature is its Great Red Spot (GRS). The spot was named around 1878 when it turned a vivid brick red, but in recent decades it has generally been a much less conspicuous pale tan. The Red Spot is a vast, long-lived storm, spinning like a cyclone. However, unlike low-pressure cyclones and hurricanes on Earth, the GRS rotates in a counter-clockwise direction in Jupiter's southern hemisphere, showing that it is a high-pressure system.

Of course there's a lot more to look for in Jupiter's atmosphere than the GRS. That's a good thing, because for something so famous, it can be surprisingly difficult to see. It appears slightly more distinct when Jupiter is viewed through a light green or blue filter.

Below is a calculator you can use to predict the local and Universal Times and dates when the center of the Great Red Spot should cross Jupiter's central meridian, the imaginary line down the center of the planet's disk from pole to pole. Click "Initialize to today" to view the dates and times of the next three transits of the GRS. Or you can enter any date this year to find other transit times. The listed times should be accurate to within a few minutes.

Please enter a date:
Universal Times
of Red Spot transits
centered on date:

local dates & times
of Red Spot transits:

Note: local times are based on a time zone offset of
  hour(s) from UT as given by your Web browser.
JupiterMoons iconIf you enjoy using this utility and own an iPhone or iPad, you might be interested in our newest app. JupiterMoons is your essential guide to observing Jupiter whenever the king of planets reigns the night sky, showing you the locations of Io, Europa, Ganymede, Callisto, and the Great Red Spot at any date and time. Available on the iTunes App Store for only $2.99.

These predictions assume the Red Spot was at Jovian System II longitude 283° in January 2018 and continues to drift 2° per month, based on historical trends noted by JUPOS. If the GRS moves elsewhere, it will transit 123 minutes late for every 1° of longitude greater than that used in this tool or 123 minutes early for every 1° less than the longitude in this tool. Features on Jupiter appear closer to the central meridian than to the limb — and thus are well placed for viewing — for 50 minutes before and after their transit times.

If you see any problems with this tool, or any of our interactive tools, please send an email to

9 thoughts on “Transit Times of Jupiter’s Great Red Spot

  1. Monica YoungMonica Young

    Hi, Chuck, welcome to the site. The latest issue of Sky & Telescope will always have a list of the Great Red Spot transits (with the exception of the July issue, since Jupiter goes into conjunction on July 24th). You can also, of course, simply enter a date into the Javascript tool to find out transit times near that date :).

  2. vivian-flinspach

    Hi! I cannot find the August chart showing the positions of Jupiter’s moons (egresses, ingresses ,transitions, etc ) that is usually in my monthly Sky and Telescope magazine. Have you stopped putting it in the magazine or did I miss it? Can I get it off your website?
    Thank you! Love the magazine! Vivian

  3. JRJR

    Hi, Vivian–A much belated reply, but I hope you are enjoying the charts showing the positions of Jupiter’s moons in more recent issues. We generally don’t publish the chart in those months that Jupiter isn’t readily visible. Jupiter was in conjunction with Sun on July 24th, so its position made for difficult observing well into August.

  4. Stub Mandrelstub.mandrel

    Looking at the rate the spot is moving seems to be closer to 2 degrees a month at the moment and even higher last year, rather than the 1.25 degrees given above.
    Your predicted position is close to Calsky’s though.
    How often is the calculator reset and are you actually using 1.25 degrees or 2 degrees at the moment?

    1. Stub Mandrelstub.mandrel

      FWIW Calsky appears to be using 2 degrees and the difference between this calculator and Calsky goes from 2 minutes today to 61 minutes on 14 June.

      1. Monica YoungMonica Young

        Hmm…We looked into this, but the times we’re seeing on for June 14th match the prediction from our code almost exactly (within 6 minutes).

    2. Monica YoungMonica Young

      The description was outdated — I have now updated the description to reflect that the code is advancing at a rate of 2 degrees per month. We typically update the javascript code once a year, or more often if it becomes necessary.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.


This site uses Akismet to reduce spam. Learn how your comment data is processed.