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1、HarbertImagingTechnologyDesignedbyGuirongLiuCollectedbyHaihuaZhaoCorrectedbyYanjunZhangPrefaceSincelaunchingin1990,theHarbertSpaceTelescopehasbeendedicatedtotheworldinnumerablespectacularpicturesoftheuniverse.Thesepicturesarenotonlypublishedinnewspapers,magaz
2、ines,almostalltextbookinastronomy,butalsointhealbumcovers,advertisements,T-Shirts,coffeecups,andmoviescenes.Thesepictureshavealsoarousedpublicinterestinastronomy,theresultingimpactonthesecularcultureisnotcomparabletoanyotherastronomicalinstrumentinmoderntimes
3、.LetusuncoverthesecretofhowHubblecreateimages.AfterrepairBeforerepairTheeaglenebulaThefirstphotofromtheHubbletelescopeOnApril1,1995,theHubblespacetelescope'swidefieldandplanetarycamera2(WFPC2)takepicturesoftheeaglenebula.Justlikeordinarydigitalcamera,WFPC2als
4、ousecharge-coupleddevice(CCD)ratherthanthefilmtorecordtheimage.CCDisacomposedofphotodetectorarray,oneofthesmallestunitiscalled"pixel".Itsroleisreceivelightsignalsandturnintoelectricalsignals.WFPC2'sfieldofviewcontainsabout1600x(multipliedby)1600pixels,whichma
5、kesitroughlyequivalenttoa2500000megapixeldigitalcamera.AlthoughthecolorofWFPC2'simageisnottrue,butthesceneitcanseeisclosertothenakedeyethancolorfilm.Whyarethetopright-handcornerofthepicturelessapiece?WFPC2isactuallymadeupof4camera-threewidefieldplanetarycamer
6、a(WF)and1framecamera(PC1）Let'sglanceattheprocessoftheHubblecreateimages.Differentatomsemitspecificradiationwhichhavespecificwavelengths,thushavingaspecialcolor.Thisallowsastronomerstotakepicturesofthelightemittedbysomekindofatom.ForthepictureofEagleNebula,the
7、filterusedinWFPC2makesitcantakethephotosofthoseemittedlightfromhydrogenatoms,sulfurionsandionizedoxygen,andthefourthfiltercanonlypassthelightwhichemittedfromthefixedstars.Firstofall,cosmicraysandothernoisewillappearinthepictures.we'llthinkofsomewaytoremovethe
8、mbelow.Secondly,thepicturewhichweseenowisonlyfromtheimageofPC1,thenwewillprocessingtheimageofthe3WFcamera.Afterthat,wejuestsawoneofthe4kindsofcolorsthateachcameracanshot.Justasthecoloroft
