The Atari Compendium

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0660103030566 9[....................................................] CadenzaAstroCal(Version1.8,October6,1988) ProgramFeatures Thisprogramgenerates(foranygivenyear)acalendarcontaining thefollowinginformation: 1. Timesofsunrise,sunset,moonrise,andmoonsetforeachday 2. TimesanddatesofMoonphases 3. Timesanddatesofsolarandlunareclipses 4. Timesanddatesofsolsticesandequinoxes Inadditiontothiscalendar,theprogramcangenerate: 1. Areportofalllunarorsolareclipsesforarangeofyears 2. Areportofplanetviewinginformationforaspecifiedyear 3. Areportofperihelionsandaphelionsofplanetsfora rangeofyears 4. AreportofperigeesandapogeesoftheMoonforaspecified year 5. AreportofthedatesofEasterforarangeofyears 6. AdiagramofthepositionsofJupiter'sbright(Galilean) moons. Thecalendarandreportsareallcustomizedfortheuser's location.Alltimesanddatesareinlocaltime. Thecalendarandreportscanbeprintedonaprinterorlistedon thecomputerscreen. HardwareRequirements ThisprogramshouldrunonanyAtariSTcomputerwithamonochrome orcolormonitor.Thisprogramrunsoncolormonitorsinmedium resolutiononly(pleaseseetheBugssectionbelow).Ofcourse, userswantingtoprintoutcalendarsandreportswillneeda printer. Menus AstroCalhasthefollowingmenus:"Desk","DescribeLocation", "GenerateReport","File","Display",and"Help". The"Desk"menucanbeusedtorundeskaccessoryprograms,andto seethe"introductionbox"ofthisprogram. The"DescribeLocation"menuisusedtospecifyone'slocation(in latitudeandlongitude),andthedifferencebetweenlocaltimeand UT(universaltime(sometimescalledGMT(GreenwichMeanTime)). The"GenerateReport"menuhaseightsubmenus:"Calendar","Lunar Eclipses","SolarEclipses","PlanetViewInfo","Planet Distance","MoonDistance","DatesofEaster",and"Jupiter Moons". The"File"menuhasonlyonesubmenu,labeled"Quit".This submenuisselectedtoquittheentireprogram. The"Display"menuhastwosubmenus,"Scroll"and"Stop".Ifyou selectthe"Stop"submenu,theprogramwillwaitforyoutotype theRETURNkeyaftereachpageoftextislistedonthedisplay screen.Ifyouwouldpreferthattheprogramcontinuouslywrite textonthedisplayscreenwithoutstopping,selectthe"Scroll" submenu.The"Display"menudoesnotaffecttheprintingof calendarsandreportsonaprinter. The"Help"menuisusedtogetbasicinformationaboutthe program. GettingStarted Firstofallyouwillneedtoprovidetheprogramwithsome informationaboutyourlocationandlocaltime.Thisinformation isrequiredtoallowtheprogramtocustomizeitsoutputforyour locationandtimezone. Selectthe"DescribeLocation"menuwiththemouse.Thenselect the"DescribeLocation"submenu.Atthispointyoushouldseea "dialogbox"allowingyoutospecifyyourcity'sname,your latitudeandlongitude,andthedifferencebetweenyourlocaltime andUT. Typethenameofyourcityinthespacelabeled"LocationName". Typeinyourlatitudeandlongitudeintheappropriatespaces. Notethatlatitudeandlongitudemustbeenteredasdecimal degrees.Toconvertanangleexpressedindegrees,minutes,and secondsformtodecimaldegrees,usethefollowingformula: decimaldegrees=degrees+minutes/60+seconds/360 Forexample,ifyouknowthatyourlatitudeis32degrees,12 minutes,and44seconds,youwillneedtotypeinalatitudeof 32.21since: 32+12/60+44/3600=32.21(rounded) Ifyoulivenorthoftheequator,selectthebuttonlabeled "North".Otherwiseselect"South". Inthesameway,enteryourlongitudeindecimaldegrees,and selectthe"West"buttonifyoulivewestofGreenwich,England, or"East"otherwise. Finally,enterthenumberofhoursthatyoumustaddtoUTto converttoyourlocaltime.IfyoumustsubtractfromUTtoget yourlocaltime,enteranegativenumber.Youmayentera fractionalnumber(e.g.4.5). UsersintheUSAcanusethefollowingtable: AtlanticTimeZone LocalTime=UT+-4hours EasternTimeZone LocalTime=UT+-5hours CentralTimeZone LocalTime=UT+-6hours MountainTimeZone LocalTime=UT+-7hours PacificTimeZone LocalTime=UT+-8hours MostofAlaska LocalTime=UT+-9hours HawaiiTimeZone LocalTime=UT+-10hours Oncethisinformationisentered,selectthebuttonlabeled "Done".Thisinformationwillbesavedinadiskfile(named astrocal.dat)andneednotbeenteredagain. NotethatAstroCalgivesalltimesanddatesinlocalstandard time,neverinDaylightSavingsTimeorSummerTime. Nowthatyou'vespecifiedyourlocation,youcangeneratean astronomicalcalendarorareport. Noteaboutenteringyears:ifyouwantacalendarorreportfor theyear1988,enter1988,not88.Negativeyears(i.e.B.C.)can beentered. GeneratinganAstronomicalCalendar Selectthe"GenerateReport"menu,andthenthe"Calendar" submenu.Atthispointyoushouldseeadialogboxallowingyou tospecifytheyearofthecalendar,thestartingmonthofthe calendar,andwhetherthecalendarshouldbeprintedonyour printeroronthecomputerscreen.Onceyou'vegiventhis information,pressthe"Done"button,andthecalendarwillbe generated.Ifyouchangeyourmind,pressthebuttonlabeled "Cancel",andthecalendarwillnotbegenerated.Preparingan astronomicalcalendarwilltakeaboutonehour. Thecalendarwillcontainseveralabbreviationswhichare explainedintheAbbreviationssectionlaterinthisdocument. EquinoxesandSolsticesintheNorthernHemisphere ThecelestialequatoristheplanedescribedbytheEarth's equator.TheeclipticistheapparentpathoftheSunacrossthe skyduringoneyear. Equinoxesoccurwhentheeclipticcrossesthroughthecelestial equator.AttheMarchEquinoxtheSunappearstocrossthe celestialequatoronitsjourneynorth.TheSeptemberEquinox happenswhentheSuncrossesthecelestialequatorgoingsouth. Solsticesoccurwhentheeclipticismaximallynorthorsouthof thecelestialequator.AttheJuneSolsticetheSunisasfar northofthecelestialequatoraspossible.AttheDecember SolsticetheSunisasfarsouthaspossible. SpringbeginsattheMarchEquinox,SummerattheJuneSolstice, FallattheSeptemberEquinox,andWinterattheDecember Solstice. Forthesouthernhemisphere,switchnorthandsouth,summerand winter,andfallandspringinthepreviousthreeparagraphs. GeneratinganEclipseReport Selectthe"GenerateReport"menuwiththemouse,andthenselect the"LunarEclipses"or"SolarEclipses"submenu.Atthispoint youshouldseeadialogboxpromptingyoufortherangeofyears ofthereport,andwhetherthereportshouldbeprintedonyour printerorlistedonyourdisplayscreen.Press"Done"when you'veenteredalloftheinformation,orpress"Cancel"toquit. InterpretingaLunarEclipseReport Duringalunareclipse,allobserversthatcanseethemoonwill seethesamepart(i.e.moonentersshadow,maximumeclipse,moon leavesshadow)oftheeclipseatthesameinstant.Thusforeach eclipseintheeclipsereport,youwillbeabletoviewagiven partofthateclipseifitoccursbetweenthetimeofmoonriseand moonsetonthedayoftheeclipse. InterpretingaSolarEclipseReport Thisprogramdoesnotcomputethelocalcircumstancesofsolar eclipses.Consequently,youwillnotbeabletodeterminewhether asolareclipsepredictedbyAstroCalwillbevisibleinyour area. GeneratingaPlanetViewingInformationReport Selectthe"GenerateReport"menuwiththemouse,thenselectthe "PlanetViewInfo"submenu.Atthispointyouwillbeprompted forthemonthandyearatwhichthereportwillbegin,andwhether youwantthereportprintedonyourprinteroronyourdisplay screen.Press"Done"whenyou'veenteredalloftheinformation, orpress"Cancel"toquit.  InterpretingaPlanetViewingInformationReport Thisreportwillhelponedeterminewhetherornotagivenplanet willbevisibleonagivenday,anditslocation.Planet locationsaregiveninrightascension(expressedindecimal hours)anddeclination(decimaldegrees). Theelongationofplanetsisgivenindecimaldegrees.Consider tworaysoriginatingatthecenteroftheEarth,withonegoingto thecenteroftheSun,andtheothergoingtothecenterofa planet.Thatplanet'selongationistheanglebetweentheserays. Ifaplanet'selongationisnear0(or360)degrees,itwilltend nottobevisiblefromtheEarth. Toanearthboundobserverplanets,liketheMoon,havephases. Thisreportspecifiestheilluminatedfractionofaplanet'sdisk. Thisisanumberbetween0(foraplanetthatisnotvisible(like thenewMoon))and1(foraplanetwhosediskisentirelyvisible (likethefullMoon)). Thisreportalsogivesthedistancebetweenthecenterofthe Earthandaplanet,expressedinastronomicalunits.One astronomicalunitisequaltotheaveragedistancebetweenthe Earth'sandSun'scenters(149,598,770km). GeneratingaPlanetDistanceReport AplanetachievesperihelionwhenitcomesclosesttotheSun. Aphelionoccurswhenaplanetisatitsgreatestdistancefromthe Sun.Togenerateareportspecifyingthedatesofperihelionand aphelionforplanets,selectthe"GenerateReport"menu,andthen selectthe"PlanetDistance"submenu.Youwillbepromptedfor therangeofyearsofthereport,andwhetherthereportshouldbe printedonyourprinterorlistedonyourdisplayscreen.When you'veenteredthisdata,press"Done"togeneratethereport,or "Cancel"toquit. GeneratingaMoonDistanceReport PerigeeoccurswhentheMoonisclosesttotheEarthinitsorbit, andapogeewhenitismostdistant.AtperigeetheMoon's influenceontidesisgreatest.Toproduceareportofthedates ofperigeeandapogee,selectthe"GenerateReport"menuandthe "MoonDistance"submenu.Thenentertheyearofinterest,andthe startingmonth.Decideifthereportshouldbelistedonyour displayscreenorprintedonyourprinter,orselectthe"CANCEL" buttontoquit.Itwilltakeabouthalfanhourtocompletethis report. Inthereport,thedistancesgivenarebetweenthecentersofthe EarthandMoon.ThediameteroftheMoonisdefinedasfollows: imaginetwolines:onelineextendsfromtheEarth'scenterto therightmostpartoftheMoon'ssurface.Theotherlinegoes fromthecenteroftheEarthtotheleftmostpartoftheMoon's surface.Theanglebetweenthesetwolinesisthediameterofthe Moon.Thediameterofabodyisalsocalledthebody'sangular sizeorangulardiameter. GeneratingaDatesofEasterReport Easterisdefinedas(usually)thefirstSundayafterthe fourteenthdayafterthefirstnewMoonafterMarch21.To produceareportofthedatesofEasterforagivenrangeof years,selectthe"GenerateReport"menuandthe"DatesofEaster" submenu.Thenenterarangeofyears,anddecideifthereport shouldbeprintedonyourprinterorlistedonyourcomputer screen.Finally,press"Done"togeneratethereport,or"Cancel" toquit. GeneratingaJupiterMoonsReport Jupiterhas17ormoremoons.Fourofthese(theGalileanor brightmoons)canbeseenwithbinoculars. ThisfeatureallowsuserstogeneratediagramsofJupiterandits Galileanmoons. Selectthe"GenerateReport"menuandthe"JupiterMoons"submenu. Entertheyear,month,day,andtime(inlocaltime,24-hour format).Thenpress"Done"togeneratethereport,or"Cancel"to quit. InterpretingaJupiterMoonsReport Thelargestcircleinthecenterofthediagramrepresents Jupiter,andthesmallernumberedcirclesrepresentthemoons: 1:Io 2:Europa 3:Ganymede 4:Callisto ThediagramrepresentstheviewofJupiteranditsmoonsonthe specifiedinstant,withthefollowingcaveats: 1. ThediagramrepresentstheviewofJupiteranditsmoonsas seenthroughaninvertingtelescopeinthenorthern hemisphere.IfyouareviewingJupiterthroughbinoculars, yourviewwillappeartobereversedleft-to-right. 2. Inthediagram,Jupiter'sequatoriseven withthex axis-whenviewedfromatelescopeorbinoculars, Jupiter'sequator(andthemoons)willtendnottobe even withthe observer'shorizon. 3. Thediagramdoesnotspecifyifamoonisinfrontofor behindtheplanet,soifamoonappearsinfrontofJupiter inthediagram,itmayinrealitybebehindtheplanet. QuittingEarly Ifyouwanttoquitinthemiddleofpreparingacalendaror report,presstheUndokey.Inamoment(butnotimmediately) you'llbegiventheopportunitytoquitwhateveryou'redoingand goontosomethingelse(orquittheprogramentirely). QuittingtheProgram Whenyouwanttoquittheentireprogram,selectthe"File"menu andthe"Quit"submenuwiththemousebutton.Ifyou'vechanged yourlocationinformation,youwillbeaskedifyouwanttosave thechanges.Ifyouanswerno,yourchangeswillbediscarded. Ifyouansweryes,thechangeswillbesavedinadiskfile(named astrocal.dat)andwillbeavailablethenexttimeyourunthe program. Abbreviations SR: Sun Rise SS: Sun Set MR: Moon Rise MS: Moon Set FM: Full Moon NM: New Moon FQ: First Quarter LQ: Last Quarter MEQ: March Equinox JSO: June Solstice SEQ: September Equinox DSO: December Solstice UT: Universal Time AU: Astronomical Unit RA: Right Ascension DEC: Declination DEGS: Decimal Degrees HRS: Decimal Hours ELO: Elongation ILL: Illuminated Fraction of Planet's Disk DIST: Distance from Earth NoteAboutAccuracy Theresultsofthisprogramarenotexactforthreereasons: 1. Allcomputerfloatingpointarithmeticisapproximate. 2. Simplifyingassumptionsintheastronomicalcalculations resultinalossofaccuracy. 3. Someoftheastronomicalcalculationsareoptimizedforthe presentday,andarenotasaccuratefordatesfarintothe pastorfuture. Atanyrate,valuescomputedbyAstroCalforyearsinthelast quarterofthetwentiethcenturyareusuallyaccuratetowithina fewminutes,withthefollowingexceptions: 1. Calculationofplanetperihelionandaphelion:datesforthe Earthmaybeoffby morethanoneday,datesforJupiter maybeuptohalfa monthinerror,anddatesforSaturnmay beoffbymorethan onemonth. 2. CalculationofMoonperigeeandapogee:thetimeofperigee orapogeemaymissthemarkbyanhour. BugsandLimitations Thisprogramdoesnotpredictpenumbrallunareclipses,only umbrallunareclipses(mostofthepenumbraisnotdarkenoughto haveanoticeableeffectontheMoon'sbrightness). Umbrallunareclipseshavingaverysmallmagnitudemaybemissed. Forexample,AstroCaldoesnotpredictthelunareclipseofMarch 3,1988,whichhadamagnitudeofonly0.003. SincethisprogramwasdevelopedonamonochromeAtariST,there maybesomeproblemsrunningtheprogramonacolorsystem. Ifyoufindanybugs,pleasereportthemtotheauthor(the addressisbelow).Thisprogramisundercontinuousrefinement, andyourbugreportsandsuggestionswillcontributetoits improvement. FurtherReading Mathematicalastronomyisgreatfun,andprobablyeasierthanyou think.Thetwobooksthathelpedmethemostinwritingthe programare: 1. AstronomicalFormulaeforCalculatorsbyJeanMeeus(third edition),publishedbyWillmann-Bell. Meeus'bookisoutstanding.Althoughthemethodscouldbe performedonacalculator,theyarecertainlyviableforuseina computerprogram.MostofthemethodsusedinAstroCalaredrawn fromthisbook. 2. "PracticalAstronomywithyourCalculator"(secondedition) byPeterDuffett-Smith,publishedbyCambridgeUniversity Press. ThemethodsinDuffett-Smith'sbooktendtobelessprecisethan thecorrespondingonesinMeeus'book.However,thisbookisvery usefulasareference.SomeofthemethodsusedinAstroCalare drawnfromthisbook(chieflycoordinatetransformations). Duffett-Smithhasalsowritten"AstronomywithyourPersonal Computer".Thisbookisforsomeonewhosimplywantstotypeina pre-writtenprogramtodoastronomicalcalculations.Thereare manyBASICprogramsinthisbook,butlessbackgroundinformation thanin"PracticalAstronomywithyourCalculator". Thefollowingbookcontainsawealthofinformationaboutmany differentastronomicalphenomenaoveralongspanofyears.Itis extremelyusefulforverifyingtheaccuracyofaprogram: "AstronomicalTablesoftheSun,Moon,andPlanets",byJean Meeus,publishedbyWillmann-Bell. DonaldMenzelandJayM.Pasachoff's"StarsandPlanets"isa colorfulandfunbook.Itisveryusefulforthosewhowantto findandobservevariousstarsandplanets. KimLong's"TheMoonBook"(publishedbyJohnsonBooks)isan interestingandfunbookpackedwithinformation,diagrams,and folkloreabouttheMoon. Mostalmanacscontainmuchastronomicaldata. DistributionofthisProgram SinceCadenzaAstroCalispublicdomain,usersmayfreely distributecopiesoftheprogramtootherusers,usergroups, electronicbulletinboards,etc. Payment Ifyoulikethisprogram,pleasesend$5.00UStothefollowing address: EricBergman-Terrell CadenzaSoftware,Ltd. 1450West116thAvenue,#21 Westminster,CO80234 U.S.A. For$10.00+$2.00postageyoumayorderadiskcontainingthe completesourcecodeforthisprogram,writteninOSSPersonal Pascalversion2.0. Youmaywritetothesameaddresstoreportbugs,request additionalinformation,suggestimprovementsintheprogram,etc. Ifyouwantareply,pleaseincludereturnpostage(2IRCsfor thoseoutsidetheU.S.A.). Enjoytheprogram!