Storms, colour vari­a­tions and ring spokes are all worth track­ing

Sky at Night Magazine - - IMAGING FOR SCIENCE -

Saturn is a ma­jor gas planet but the amount of de­tail it shows through am­a­teur scopes is sig­nif­i­cantly less than its in­ner neigh­bour, Jupiter.

This is be­cause of the high layer of haze in its at­mos­phere and its greater dis­tance from the Sun. Con­se­quently Saturn’s at­mo­spheric fea­tures are far more sub­tle in ap­pear­ance. Bright spots on its disc rep­re­sent the pres­ence of Satur­nian storms. Ob­serv­ing and record­ing such events is ex­tremely im­por­tant and pro­grams such as WinJUPOS can be used to mea­sure their po­si­tion and track drift. Oc­ca­sion­ally, larger long-lived events, such as the ‘Dragon Storm’ of 2010/11 (a large, bright and com­plex con­vec­tive storm in Saturn’s south­ern hemi­sphere), break out and ap­pear to spread through many de­grees of lon­gi­tude. Fre­quent imag­ing is en­cour­aged to help pro­vide a global record of these in­fre­quent events.

In ad­di­tion to the ap­pear­ance of storms in Saturn’s at­mos­phere, the planet also shows a se­ries of belts just like those seen in Jupiter’s at­mos­phere. How­ever, un­like the Jo­vian belts, Saturn’s ap­pear far less prom­i­nent and de­tailed. De­spite this, im­ages taken through dif­fer­ent fil­ters can pro­vide im­por­tant in­for­ma­tion as to how the in­ten­sity of the belts changes. When Saturn is pre­sented with a high tilt an­gle, an in­ter­est­ing ex­er­cise is to try to record phe­nom­ena found at the po­lar re­gions, such as the north­ern hemi­sphere’s po­lar hexagon. Be­tween 2012 and 2016, the hexagon changed from mostly blue to more of a golden colour, so those this is def­i­nitely an in­ter­est­ing, dy­namic fea­ture for am­a­teur astronomer­s to chron­i­cle.

Of course, a ma­jor fea­ture of this beau­ti­ful world are its mag­nif­i­cent rings and mon­i­tor­ing them for sub­tle vari­a­tions in in­ten­sity is an­other im­por­tant project for am­a­teur im­agers. The pres­ence and ap­pear­ance of ra­dial ‘ring spokes’ is of par­tic­u­lar in­ter­est. Im­aged and an­i­mated by or­bit­ing space­craft, this phe­nom­ena has been re­ported by vis­ual ob­servers many times too. Cap­tur­ing an an­i­mated se­quence show­ing ring spoke move­ment from Earth would be a very valu­able record in­deed.

As with most plan­ets, the use of fil­ters can en­hance the con­trast of cer­tain fea­tures. As ever, it’s im­por­tant to ac­cu­rately record the date, time and which fil­ters have been used to pro­duce each im­age.

Saturn’s rings ap­pear brighter near to op­po­si­tion than at other times, as this com­pare and con­trast shows

The use of imag­ing fil­ters (a red one is be­ing used here) can help im­prove the vis­i­bil­ity of Satur­nian phe­nom­ena such as the North­ern Hemip­shere’s po­lar hexagon

Like Jupiter, Saturn’s at­mos­phere shows nu­mer­ous belts and zones. Record­ing vari­a­tions in their in­ten­sity and colour will make valu­able con­tri­bu­tions to sci­ence

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