When Does the Great Red Spot crosses Jupiter¹s Central Meridian
(Universal Dates & Times)
                 The imaginary line down the center of the  planet's disk from pole to pole. The spot has
been pale orange-tan in recent years. It appears slightly more distinct when Jupiter is viewed through
a light green or blue filter as do the dark cloud belts.
              These predictions assume the Red Spot is at Jovian  System II longitude 74°, the most
recent value provided by John W. McAnally of the Association of Lunar and Planetary Observers.
If it has moved elsewhere, it will transit 1 2/3 minutes late for every 1° of longitude greater than
74°, or 1 2/3 minutes early for every 1° less than 74°.
             Markings on Jupiter appear closer to the central meridian than to the limb-- and thus well
placed for viewing-for 50 minutes before and after their transit times.
             Here is a Java applet to calculate the Transits times of the Red Spot from Sky & Telescope.
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              About Universal Time (UT). To convert a UT time and date to a standard time and date in
North America, subtract the following hours: to get
Eastern Standard Time, 5;
CST, 6;
MST, 7;
PST, 8;
Alaska, 9; or
Hawaii, 10.
              To obtain daylight saving time, subtract one hour less than these values. If you get
a negative number of hours, add 24; in  this case the result is on the date before the UT date given.
For example, 6:45 UT on the 9th of the month is 2:45 a.m. on the 9th EDT, and 11:45 p.m.
on the 8th PDT.

              You may find it easier just to remember when  0:00 UT happens in your time zone.
              This is on the previous date at
                    7 p.m. EST,
                    6 p.m. CST,
               5 p.m. MST, or  4 p.m. PST.
              When daylight saving time ("summer time") is in effect:
                    8 p.m. EDT,
                    7 p.m. CDT,
               6 p.m. MDT, or  5 p.m. PDT.

            ALPO Jupiter Section

            GREAT JUPITER page from  Dept. of Physics & Astronomy  Stephen F. Austin State U.

                                                                                                       tjt