The Sun and How to Observe It

213 Pages·2009·4.882 MB·English

by  Jamey L. Jenkins (auth.)

The Sun and How to Observe It
Forfurthervolumes:
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Jamey L. Jenkins
The Sun and How to
Observe It
1 3
JameyL.Jenkins
Homer,IL,USA
[email protected]
ISBN:978-0-387-09497-7 e-ISBN:978-0-387-09498-4
DOI10.1007/978-0-387-09498-4
LibraryofCongressControlNumber:2008939373
#SpringerScienceþBusinessMedia,LLC2009
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software,orbysimilarordissimilarmethodologynowknownorhereafterdevelopedisforbidden.
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Printedonacid-freepaper
springer.com
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Acknowledgements
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IextendmysincereappreciationtoDr.DavidHathaway,DavidWilliams,andFred
EspenakofNASAforpermissiontousedataappearingontheirwebpagesandalso
toMatsLo¨fdahloftheRoyalSwedishAcademyofSciences.Specialthanksisgiven
toRichardHilloftheLunarandPlanetaryLaboratory,UniversityofArizona,for
his support and to Gordon Garcia, Art Whipple, Eric Roel, Howard Eskildsen,
SteveRismiller,GregPiepol,VincentChan,ChristianViladrich,GemaAraujo,and
LexLaneforuseoftheirspectacularimagery.BradTimersonoftheAssociationof
Lunar and Planetary Observers Solar Section computed and supplied the solar
Ephemeredesfoundinthebackofthebook.
My gratitude goes out to Amber Eldridge for information regarding skin pro-
tectionandtheSun,andalsotoRayCashandRobertHess,whoprovidedoutlines
oftheirdedicatedsolartelescopes.AndtoallmycorrespondentsontheInternet
whosharethiswonderfulhobbywiththeworldandme.
Mostly, though, I offer my deepest appreciation to my wife, Mary, and my
immediate family for permitting methe time out of ourbusy lives toattempt to
putonpaperanencouragingwordortwothatinspireswhatshouldbeathrilling
experiencefor anyone possessingthe desire toobserve the Sun. Observingmost
astronomical objects and particularly the Sun requires unending patience, con-
tinual development of your astronomical eye, and the quenching of a relentless
thirstforknowledge. TheSun withitsmulti-facetedfacetests andsatisfies these
essentials.
ClearSkies
JameyJenkinsIL,USA
v
Contents
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
AbouttheAuthor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
s
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii e
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1. TheSun,YesterdayandToday. . . . . . . . . . . . . . . . . . . . . . . . . . . 1
OneofMillions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
WhatExactlyistheSun? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
TheOriginoftheSun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
HowtheSunWorks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
EnergyfromtheInsideOut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
RadiativeZone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
ConvectionZone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Photosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
MagneticFields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
ChromosphereandCorona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
TheEarth-SunRelationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2. SomeBasicsofSolarObserving . . . . . . . . . . . . . . . . . . . . . . . . . . 17
WhyObservetheSun?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
SafetyandtheSun. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SeeingConditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3. ObservingtheWhiteLightSun . . . . . . . . . . . . . . . . . . . . . . . . . . 29
TelescopesforWhiteLightSolarObserving . . . . . . . . . . . . . . . . . . 29
ReflectingTelescopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
CatadioptricTelescopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
RefractingTelescopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
ObservingbySolarProjection . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
DirectObservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
ObjectiveFilters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
HerschelWedge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
UsingSupplementaryFilters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
DedicatedTelescopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
DobsonianSolarTelescope. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
PhotographicNewtonian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
AFinalWord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
vii
4. WhiteLightSolarFeatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
BubblingWitch’sBrew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
DirectionsontheSun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
ActiveRegions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
RotationoftheSun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TheSolarCycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
LimbDarkening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Granulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Faculae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Pores. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
s Sunspots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
t
n SunspotUmbrae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
e
t SunspotPenumbrae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
n
o SunspotGroups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
C
ClassificationofSunspotGroups. . . . . . . . . . . . . . . . . . . . . . . . . . 64
WhiteLightFlares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
HeliographicCoordinates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
RecordingPositionsonaPhotograph . . . . . . . . . . . . . . . . . . . . . . 69
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5. RecordingWhiteLightObservations . . . . . . . . . . . . . . . . . . . . . . 73
ObservingPrograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
StatisticalPrograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
SunspotCounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
PolarFaculae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
MorphologyPrograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
DrawingsorPhotographs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
WholeDiscPhotos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
ActiveRegionPhotography. . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
6. ObservingtheMonochromaticSun. . . . . . . . . . . . . . . . . . . . . . . . 89
AbovethePhotosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
EmissionandAbsorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
HistoryofChromosphericObserving . . . . . . . . . . . . . . . . . . . . . . 91
FilterTerminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
SelectionofaTelescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
FilteringSystemsfortheTelescope . . . . . . . . . . . . . . . . . . . . . . . . 100
End-LoadingH-alphaFilters. . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Front-LoadingH-alphaFilters. . . . . . . . . . . . . . . . . . . . . . . . . . 103
FiltersforCa-KObserving . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
ObservingTipsandAccessories . . . . . . . . . . . . . . . . . . . . . . . . . . 106
EnhancingDiscContrast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
SunShades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Polar-MountedHeliostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
TilterMechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7. MonochromaticSolarFeatures. . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Prominences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
viii
SolarFlares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
ChromosphericNetwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
ObservingProjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
SolarMorphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
ProminenceMeasurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8. SolarPhotography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
AHobbyWithinaHobby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
ABriefHistoricalPerspective. . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
SolarPhotographyBasics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
s
FilmastheRecordingMedium. . . . . . . . . . . . . . . . . . . . . . . . . . . 136 nt
DigitalCameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 e
t
DSLRCameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 n
o
WebcamsandDigitalImagers . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 C
DedicatedAstronomicalCameras . . . . . . . . . . . . . . . . . . . . . . . . . 147
ProcessinganImage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
FileFormat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
PhotoEditingPrograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
CalibratingtheMonitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
RotatingandCroppingtheImage . . . . . . . . . . . . . . . . . . . . . . . 154
HistogramAdjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
ImageSharpening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
SavingtheFile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
WorkingwithChannels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Colorizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
CreatingIsophoteImages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Time-LapseVideos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
9. WheredoYouGofromHere? . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
AppendixAResources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
AmateurObservingOrganizations . . . . . . . . . . . . . . . . . . . . . . . . 165
ManufacturersandSuppliersofSolarEquipment . . . . . . . . . . . . . . 165
PhotographicSuppliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
AppendixBGlossaryofSolar-RelatedTerms . . . . . . . . . . . . . . . . . . . 167
AppendixCDailySolarEphemeris,July2008–January2012 . . . . . . . . . 175
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
ix
About the Author
Jamey Jenkins has been a regular contributor to the Sunspot Program of the
American Association of Variable Star Observers (AAVSO) since 1990 and an
activeobserverfortheAssociationofLunarandPlanetaryObservers(ALPO)Solar
Sectionsince1998.HehasbeenAssistantSectionCoordinatorofthatgroupforthe
last3years.Anastronomyenthusiastsinceyouth,healsohaspublishednumerous
articlesinTheStrollingAstronomerandimagesinSky&Telescope.
Living among the corn and soybean fields of mid-America affords wide-open
viewsofthenightanddaytimesky.WhennotexploringtheMoon,planets,orhis
favorite celestial body, the Sun, he earns a living as a digital pre-press specialist
with R. R. Donnelley, the largest commercial printer in North America at its
Crawfordsville,Indiana,facility.
Jamey and wife Mary are the parents of four adult daughters and four grand-
children.‘‘Weareafamilyofvariedinterestsandtalents.Weareprinters,health
r
care professionals, musicians, teachers, historians, social service providers, and o
h
computertechnologyspecialists.Astronomy,though,hastouchedonlytwoofus. t
u
Myson-in-lawChrisandIarefollowersofGalileoandCopernicus,spendingour A
sparetimeenjoyingthebeautyoftheheavensandsharingitwithanyonethatis e
h
curiousenoughtopeekthroughthetelescope,’’saysJamey.
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xi
Introduction
Over four decades ago an amateur astronomer browsing the stacks at his or her
locallibrarymighthavecomeacrossacopyofWilliamBaxter’sbook,TheSunand
theAmateurAstronomer.ThisEnglishauthor’stextgaveaspiringsolarastronomy
buffsalookintothehowandwhyoftechniquesusedforobservingtheSun.Baxter
carefully painted a picture of how an amateur astronomer, using only a modest
telescope,sketchpad,andsheetfilmcamera,couldleisurelyrecordsolaractivity.
Over the years a number of devotees, including myself, found Baxter’s work
invaluableinthepursuitoftheirsolarastronomyhobby,hisbeingthefirstbook
ofitskindwrittenforamateurstudiesoftheSun.
Anamateurobserverfromthaterawouldhardlybeabletoimaginethecurrent
astronomy scene. Observational astronomy has experienced a complete revolu-
tion!Forthemostpartpencilandpaper,vitalinBaxter’stime,arenowrelegatedto
notetaking.Theelectronicsensorhasreplacedfilm,andadvancedvideotechni-
quesofferthemostpromiseforthoseattemptingtorecordthefinestsolardetailin
theirphotographs.
Anothersurprisefortheearlierobservermightbetheavailabilityofcommercial
telescopesdedicatedspecificallytosolarobservations.Inthepastmonochromatic
observing, done by utilizing a thin slice of light from the solar spectrum, was
available only to the craftsman capable of building the complex, delicate instru-
mentsneededtoperformsuchobservations.Theseinstruments,thespectrohelio-
scope and monochromator, were expensive and often beyond the skill of the
typical telescope maker to construct. Since that time, the availability of solar
telescopes and filters for Hydrogen-alpha and Calcium-K observing have awa- n
kenedaninterestindaytimeastronomytoawholenewgenerationofobservers. o
i
t
Usinganoff-the-shelfsolartelescope,today’samateurastronomerscoupledwith c
u
an inexpensive computer webcam are producing time-lapse movies of chromo- d
sphericactivitythatwaspreviouslyonlythedomainofaprofessionalastronomer o
r
locatedatahigh-altitudesolarobservatory.Neverbeforehavesuchopportunities nt
existedforamateurobservers.Thisistrulyanexcitingtimetobeasolarastron- I
omyhobbyist.
With this book we hope to project the sense of excitement that so many
observers experience when we point our telescopes sunward. If you are new to
solarastronomy,youshouldbecomeeducatedonhowtosafelyexploretheSun.
Veteranobserverscouldfindinthesepagesanewtwisttoanoldtechniquethat
allowsseeingtheSuninadifferentway.
As a variation on the hobby of star gazing, solar observing provides an alter-
native to late nights, cold fingers, and fumbling in the dark trying to locate that
expensive eyepiece you’ve just dropped in the dew-soaked grass. All events
happening on the Sun are unique and never will be repeated exactly. This is
muchofwhatattractsindividualstosolarastronomyandisthereasonthereisa
scientificvaluetoeachofyourobservations.Whetheryoufollowthegrowthand
decayofasunspotgroup,therapidemergenceofasolarflare,orthesprayofan
xiii