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.
|If 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 12⁄3 minutes late for every 1° of longitude greater than that used in this tool or 12⁄3 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.