Preparing for the Grand Conjunction: Jupiter and Saturn Observation Tips

Observation of Jupiter and Saturn with binoculars and telescope.

Withtheuseofbinocularswecanperfectlyobservethebrightestsatellitesofbothplanetsandcertainplanetaryaspects. First,whenobservingJupiterandSaturnwithbinoculars,thefirstthingwewillhighlightisthatacircle isappreciated, insteadofapoint imageaswhenweseeastar.Althoughtheyareallsphericalobjects,theplanetsoftheSolarSystem,beingclosertotheEarth,wesolvethemintheirrealcircularshapesonthecelestialvaultwhenobservingthemwithbinoculars,whichisnotthecasewithstars,duetotheimmensityofthedistancethatseparatesusfromthem.Second, the magnification provided by binoculars allows us to distinguish the brightestsatellitesorbiting thegiantplanets. Jupiterhas79cataloged satellites. Fourof themare thelargest,inorderfromlargesttosmallest,Ganymede,Callisto,IoandEuropa,withdiametersof5,262 km the largest and 3122 km the smallest, followed by 5 satellites with diametersbetween50and200km,7satelliteswithdiametersbetween10and50kmand63satelliteswithdiametersoflessthan10km.Ofallofthemwewillbeabletoseewiththebinocularsthe4 largest,which inorderofdistance fromtheplanetare Io,Europa,GanymedeandCallisto.These satellites have been known since 1610, when the Italian astronomer, physicist andengineerGalelioGalileipointedhisrudimentarytelescopeatJupiterandnoticedtheexistenceofseveralpointsoflightthatseemedtoaccompanyit.AdetailedobservationsuggestedthattheywereobjectsorbitingtheplanetJupiter.

This,whichtodayseemstrivialtous,intheseventeenthcenturywasthebeginningofagreatrevolutioninhumanthought.Untilthatdate,itwasadogmaoffaithtobelievethattheEarthwas at the center of theUniverse and all other objects revolved around it. Galileowith his

methodicalobservationsdiscovered that anotherobject in theuniverse, Jupiter, behavedasthecenterofitsenvironment.ThefactthattherearetwocentersintheuniversecastsdoubtonthedogmaofbelievingtheEarthasauniversalcenter.We challenge you to follow with binoculars (or better, a telescope if you have one) themovement of the four satellites discovered by Galileo and to record their position anddepending onwhat youobtain, determine if they are objects that rotate around the planetalreadysortthemaccordingtotheirdistancefromtheplanet.Forthisweprovideyouwiththefollowingtable,towhichyoucanaddrowsasyoumakeyourobservations,(youcanusetheregistrationformthatisattachedattheend):

Date(mm/dd/yyyy) TimeTU(hh/mm) Galileansatelliteposition

Somefactstoknowaboutbinocularsbeforeyoustartobserving: Binoculars aremeasuredwith twonumbersexpressedas axb. The firstnumber, a, indicatesthemagnificationandthesecondnumber,b,referstothediameterofthefrontlensesoftheinstrument.Forexample,10x50binocularsindicatethatitgives10xmagnificationandthatthefrontlensesare50mmindiameter. Itshouldbetakenintoaccountthattheamountof lightthatentersthelensisdirectlyproportionaltothesquareoftheaperture,thereforethelargerthediameter,thebrightertheobjectswillbeobserved,which isveryusefulforobservationswithlowlight,suchasmadeatnight.

Asplanetsandtheirsatellitesareverysmallpointobjects,tobetterappreciatethemwemustmountthebinocularsonastabletripodwithaspecialadapterandplaceourselvesinaplacesheltered from the wind to avoid possible vibrations, thus we will have a more staticobservation. This sameappreciation is also valid forobserving any celestial object, be it theMoonorthestars.Ifweobservebyholdingthebinocularswithourhands,ourownvibrationwillcausetheimagetomovetoomuch,preventingdetailedappreciation.

Ifweusea5”(inch)diametertelescope,wewillseethemoonsbetter,fartherapartandtheplanet'sdisksomewhatlarger,sosomethingcanbeseeninitsatmosphere.

OnDecember1,with7x50binoculars(7xmagnificationand50mmaperture),whenobservingJupiterandSaturn,bothwillenterthefieldofviewofthebinocularsatthesametime.Wewillseethemlikethis:

With15x50binocularswewillobservetheapproachofthetwogiantsoftheSolarSystemlikethis:

December1st.

OnDecember8theywillbecloserapparently.

OnDecember15theywillbequiteclose.

On December 20, one day before the closest approach, it will also offer us a magnificentimage.

December21isthekeydayoftheGreatConjunctionbetweenJupiterandSaturn.

Witha60x700telescopeusinga14mmeyepiecewewillseethemupclose.

Withan8-inchdiameter telescopeat f /10anda14mmeyepiecewewill see thiswonder:Jupiter in all its splendor surroundedby its fourGalician satellites, threeon the left, twoofthemveryclosetogether,IoandGanymedeandsomethingelseCallistoawayandonetotheright, Europe. In the same field of vision will be Saturn, to which the ring and some of itssatelliteswillbeobserved.

Witha largeraperturetelescope,an11-inchone,wewillbeabletoobservemanydetails inthe planetary atmospheres, in addition to the rings of Saturn andmore satellites of Saturn,suchasTitan,thebrightestofthemall,Rhea,Tethys,Dione,IapetusandevenEnceladus.WithmoremagnificationonSaturn,moresatelliteswillbeobserved:

TherearesomemobileappsthattelluswherethesatellitesofJupiterorSaturnarelocated,someofwhichalsoallowustorotatethefieldofviewtoobservethemfromthesideorfromaboveandthushaveaclearereffectofperspective.TheringsofSaturncanbeguessedwithbinoculars,aslongastheyaremountedonatripod,althoughatthistimewhatwewillseewillbeanelongateddisk,theringsoftheplanetarydisknotbeingseparated,this isbecauseatthistimethering isquite inclinedwithrespecttothelineofsightofobservedfromtheEarth.Galileoalsofailedtoresolvetheseparatedringoftheplanetanddrewitashavinghuge"ears."Tobeabletoobservetheringswell,atelescopeisrequired.

Rhea

Encélado

Tetis

Dione

Titán

MimasRhea

Ío Ganímedes

Calisto

Europa

Japeto

RheaTitán

Júpiter

Saturno

SaturndrawingbyGalileo

SaturndrawingbyMaríaClaraEimmart

JupiterandSaturnindetailasseenwithan8-inchorlargertelescope. Jupiter andSaturnare fundamentally gaseousplanets,whenweobserve themwitha largerdiametertelescopewewillbeabletoappreciatesomedetailsintheiratmospheres.ToappreciatemoredetailsintheatmosphereofJupiter,itisnecessarynottohaveturbulenceintheEarth'satmosphere,asthesedistorttheimageanditlooksagitated.Toachievethebestquality in thesky forastronomicalobservation,a stablesky is requiredand theobject tobeobserved ishighabove thehorizon,as faraspossible from thehorizon.Thiswillnotbe thecaseinthisobservation,sinceonthesedatesanduntiltheendofDecemberbothplanetswillbequitelowinthesky,about20degreesfromthehorizon,sowewillhavetocountonsometurbulence that will prevent seeing them completely clear. However, you will be able toappreciateseveralofitsmoonsandsomedetailsoftheatmosphere.In Jupiter, thereare two lightbrownbelts in the centerof theplanet surroundedbywhiterstripes called zones. They are lighter because they contain ice crystals. Sometimes otherthinnerbeltsarealsoseenbetweentheequatorandthepoles.

Thebeltshaveshadesrangingfromgrayishtobrownishwithreddishtones.Whitenodulesaresometimesseenattheborderbetweenthebeltsandthezones.

Withatelescopeofmorethan5inches,itispossibletosee a huge anticyclonic storm over the southernequatorial belt thathasbeenactive formore than360years.Galileodidnotgettoseeitwithhisrudimentarytelescope.Itisabout30%largerthanEarth.

Jupiter rotates on itself very fast, it completes arevolutioninjust10hours,asitissolarge,thatmakesitwiderat theequator thanat thepolesand that iswhyweseeitflattened.Thepolesarealittledarker. DuetotherotationperiodofJupiter,ifwewanttoobservethespot,onceitappearswehaveabout5hours tosee it, thenwewillhavetowaitanother5hours for it toappearagain. Itscolor isvariableandcango from intenseredto light redorpinkandsometimeswithaverypalecolor.ThereisanappthatindicateswhenJupiter'sredspotisvisible. With the use of colored filters some details are accentuated more than others and byexchanging them the details in the atmosphere can be better observed. The four mainsatellitesofJupitersometimespass infrontoftheplanetfromourpointofview.Whenthathappensyoucanseeitsoutlineoritsshadowonthesurface,ordisappearbehindtheshadowoftheplanetorbehindtheplanetitself.

With a telescope we can observe one or two paleequatorial belts on its surface on Saturn and theplanet'spolesomewhatobscured.Inthering,whenit is tiltedwithrespecttoourviewfromEarth,as ithappens now, the so-called "Cassini Division" isseen, a strip almost devoid of material, which incontrasttotherestofthematerialscatteredbythering lookblack.With largeraperturetelescopes it ispossibletoseeothersmallerdivisions intheringaswell.

To learn more about these planets and how toobserve them with a telescope and cameras, werecommendattendingtheworkshopsandtalksthathavebeenorganizedtocelebratetheevent"GiantsMeeting:TheGreatJupiter-SaturnConjunction".

DivisióndeCassini

PositionoftheGalileansatellitesofJupiter

Date(mm/dd/yyyy) TimeTU(hh/mm) Galileansatelliteposition