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Real Astronomy with Small Telescopes. Step-by-Step Activities for Discovery PDF

155 Pages·2006·5.334 MB·English
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Patrick Moore’s Practical Astronomy Series Other Titles in this Series TelescopesandTechniques(2ndEdn.) SolarObservingTechniques ChrisKitchin ChrisKitchin TheArtandScienceofCCD LightPollution Astronomy BobMizon DavidRatledge(Ed.) UsingtheMeadeETX TheObserver’sYear(2ndEdn.) MikeWeasner PatrickMoore PracticalAmateurSpectroscopy SeeingStars StephenF.Tonkin(Ed.) ChrisKitchinandRobertW.Forrest MoreSmallAstronomicalObservatories Photo-guidetotheConstellations PatrickMoore(Ed.) ChrisKitchin Observer’sGuidetoStellarEvolution TheSuninEclipse MikeInglis MichaelMaunderandPatrickMoore HowtoObservetheSunSafely SoftwareandDataforPractical LeeMacdonald Astronomers ThePracticalAstronomer’sDeep-Sky DavidRatledge Companion AmateurTelescopeMaking JessK.Gilmour StephenF.Tonkin(Ed.) ObservingComets ObservingMeteors,Comets,Supernovae NickJamesandGeraldNorth andotherTransientPhenomena ObservingVariableStars NeilBone GerryA.Good AstronomicalEquipmentforAmateurs VisualAstronomyintheSuburbs MartinMobberley AntonyCooke Transit:WhenPlanetsCrosstheSun AstronomyoftheMilkyWay:The MichaelMaunderandPatrickMoore Observer’sGuidetotheNorthernand PracticalAstrophotography SouthernMilkyWay(2volumes) JeffreyR.Charles MikeInglis ObservingtheMoon TheNexStarUser’sGuide PeterT.Wlasuk MichaelW.Swanson Deep-SkyObserving ObservingBinaryandDoubleStars StevenR.Coe BobArgyle(Ed.) AstroFAQs NavigatingtheNightSky StephenTonkin GuilhermedeAlmeida TheDeep-SkyObserver’sYear TheNewAmateurAstronomer GrantPrivettandPaulParsons MartinMobberley FieldGuidetotheDeepSkyObjects CareofAstronomicalTelescopeand MikeInglis Accessories ChoosingandUsingaSchmidt-Cassegrain M.BarlowPepin Telescope AstronomywithaHomeComputer RodMollise NealeMonks AstronomywithSmallTelescopes VisualAstronomyUnderDarkSkies StephenF.Tonkin(Ed.) AntonyCooke (continuedafterindex) Real Astronomy with Small Telescopes Step-by-Step Activities for Discovery Michael K. Gainer With 90 Figures MichaelK.Gainer P.O.Box244 NewDerry,PA15671 USA [email protected] BritishLibraryCataloguinginPublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary LibraryofCongressControlNumber:2006927794 PatrickMoore’sPracticalAstronomySeriesISSN1617-7185 ISBN-10:1-84628-478-3 ISBN-13:978-1-84628-478-6 e-ISBN-10:1-84628-508-9 e-ISBN-13:978-1-84628-508-0 Printedonacid-freepaper. ©Springer-VerlagLondonLimited2007 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced,storedortransmitted,inanyformorbyanymeans,withthepriorpermissioninwriting ofthepublishers,orinthecaseofreprographicreproductioninaccordancewiththetermsoflicences issuedbytheCopyrightLicensingAgency.Enquiriesconcerningreproductionoutsidethoseterms shouldbesenttothepublishers. Theuseofregisterednames,trademarks,etc.inthispublicationdoesnotimply,evenintheabsence of a specific statement, that such names are exempt from the relevant laws and regulations and thereforefreeforgeneraluse. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Observing the Sun, along with a few other aspects of astronomy,canbedangerous.Neitherthepublishernortheauthoracceptsanylegalresponsibility orliabilityforpersonallossorinjurycaused,orallegedtohavebeencaused,byanyinformationor recommendationcontainedinthisbook. 987654321 SpringerScience+BusinessMedia springer.com To my son Michael with love and gratitude No unregarded star Contracts its light Into so small a character, Removed far from humane sight, But if we steadfast looke We shall discerne In it, as in some holy booke How man may heavenly knowledge learne. William Habington, 1634 Preface Thesmallrefractingtelescopewithitssimpledirectdesignandconstructionand permanently aligned optics is the time tested standard for personal use. Easily portable, it can be taken out of the house and set up at a moment’s notice. Or, it can be packed conveniently into a small car for traveling to a dark observing site. With moderate care and minimal maintenance, the telescope and mount can last for generations. These instruments provide sharp, crisp high-contrast images of the Moon and planets. They are less susceptible to the effects of unstable air than larger ones, and because of their low maintenance and durability they are ideal for the parent educator or lifelong learner. Until recently, however, the high cost of small telescopes of sufficient quality for serious astronomical use has limited their accessibility. During the past decade, innovations in optical design and manufacture have loweredcostandimprovedquality.Currentdevelopmentsinlensdesignmakeit possibletoproduceaffordablerefractingtelescopeswithshortertubelengthsand greater versatility. The once very costly 90-mm Maksutov–Cassegrain, with its optimum combination of effective optics and portability, now sells for a modest price. I have often seen small instruments referred to as “grab and go” or “quick look,”notworthyofconsiderationforseriousobserving.Imaintaintheycanbe much more. Despite their limits in types of observation, 80-mm refractors and 90-mm Maksutovs have sufficient aperture and magnifying power to provide a lifetimeofobservingpleasure.Theyareidealforlunaroccultationmeasurements, tracking the solar activity cycle, observing variable stars and measuring binary ix x Preface stars. Although all the activities described here are equally applicable to larger instruments, none of them require an aperture larger than 80mm. Through the use of common digital cameras, the limiting stellar magnitude andimagescaleofsmalltelescopescanbeincreaseddramatically,thusproviding resultsonenormallyexpectsfromlargerinstruments.Muchofthisbookapplies thatprincipletomakinginterestingandusefulastronomicalobservations.Ihave takennovelapproachestoextendingtheuseofsmallinstrumentsforquantitative observations by applying unique methods for the analysis of digital camera photographs. My intent is to demonstrate that useful and significant observations can be madewithmodest,relativelylowcostequipment.Someoftheactivitiesdescribed provide the necessary tools for making valuable contributions to various inter- national astronomical data files. Others are of primarily educational value for eithertheself-learnerorthescienceeducator.Thismaterialshouldbeofinterest to both the beginning and the experienced observer. The emphasis is on what you can do with a small telescope rather than only on what you can see. Acknowledgement I am deeply indebted to Madalon Amenta for her time and skill in editing the manuscript. Michael K. Gainer June 2006 Contents Preface................................................................. ix Computer Hardware and Software........................................xv ChapterOne The Celestial Sphere ..................................... 1 ChapterTwo The Measurement of Time................................ 5 Solar Time.............................................. 5 Sidereal Time........................................... 7 Dating Observations..................................... 8 ChapterThree The Equatorial Telescope Mount.......................... 9 Mount Stability.......................................... 9 The Polar Axis Drive.....................................13 Setting Circles...........................................13 Aligning an Equatorial Mount............................15 Using Setting Circles.....................................17 A Tabletop GEM ........................................19 Go-to Mounts...........................................20 ChapterFour Telescope Considerations.................................21 Limitations Imposed by Aperture.........................21 Limitations Imposed by the Environment..................23 xi xii Contents Limitations Unique to Refractors .........................23 Short Focus Achromatic Refractors .......................24 Limitations Unique to Maksutov Telescopes...............25 Newtonian Reflectors....................................25 Eyepieces...............................................26 Focusing................................................26 The Finder..............................................27 Recommended Accessories...............................27 Which Small Telescope Should You Buy?..................27 ChapterFive Astronomical Photography...............................29 Digital Photography .....................................29 Choice of Camera .......................................31 Mounting the Camera....................................31 The Afocal Field of View.................................31 Telephoto Conversion Lenses.............................32 Processing the Print .....................................33 Film Photography.......................................34 Printing the Image.......................................35 ChapterSix The Sun.................................................37 Visual Observations of the Sun...........................39 Classification of Sunspots................................39 Sunspot Number........................................40 Visual Observations......................................41 Digital Photography of the Sun...........................42 Processing the Photographs ..............................42 The Stonyhurst Disk.....................................43 Measuring the Sun’s Rotation.............................48 Film Photography of the Sun.............................49 ChapterSeven The Moon...............................................51 Visual Observations......................................51 Digital Camera Photographs of the Moon..................52 Analyzing the Photographs...............................52 Selenography............................................53 Measurements on the Computer Monitor..................56 Measuring Lunar Libration...............................57 Film Photography of the Moon...........................59 Lunar Occultations......................................59 ChapterEight The Planets..............................................61 Sketching the Planets....................................61 Filters..................................................62 Digital Photography of the Planets........................62 Plotting the Orbital Position of a Planet...................64 Ecliptic Coordinates.....................................64 The Phases of Venus.....................................71

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