Suitable Great Red Spot transit times as seen from the Isle of Man: Date/Time Altitude 2 Jun 2018 1:17 11.9° 4 Jun 2018 22:46 20.3° 7 Jun 2018 0:24 14.8° 9 Jun 2018 21:54 20.7° Sky Bright 11 Jun 2018 23:32 17.2° 16 Jun 2018 22:40 19.0° 19 Jun 2018 0:18 10.8° 21 Jun 2018 21:48 20.3° Sky Bright 23 Jun 2018 23:26 13.8° 28 Jun 2018 22:35 16.4° Calculated by Guide 9 The above transits are calculated from the GRS having a longitude (System II) of 292° on 1st June 2018. Logitude of GRS derived from data at:- http://jupos.privat.t-online.de/