From decwrl!uunet!allbery Sun Mar 25 18:40:14 PST 1990 Article 1427 of comp.sources.misc: Path: decwrl!uunet!allbery From: ccount@ATHENA.MIT.EDU Newsgroups: comp.sources.misc Subject: v11i052: starchart 3.2 Part 24/32 Message-ID: <82344@uunet.UU.NET> Date: 26 Mar 90 00:00:14 GMT Sender: allbery@uunet.UU.NET Lines: 941 Approved: allbery@uunet.UU.NET (Brandon S. Allbery - comp.sources.misc) Posting-number: Volume 11, Issue 52 Submitted-by: ccount@ATHENA.MIT.EDU Archive-name: starchart/part24 #! /bin/sh # This is a shell archive. Remove anything before this line, then unpack # it by saving it into a file and typing "sh file". To overwrite existing # files, type "sh file -c". You can also feed this as standard input via # unshar, or by typing "sh 'doc/as.ms.aa' <<'END_OF_FILE' X.ND X X.ds St Astronomy\ Tools X.OH '\\*(St''%' X.EH '%''\\*(St' X.PP X.PP X.PP X.PP X.PP X.PP X.PP X.PP X.sp 10 X.ce X.ps +10 X.ce XAstronomy\ Tools X.ps -10 X.sp 2 X.ce XCraig\ Counterman X.PP X.bp XCopyright \(co 1990 Craig Counterman. All rights reserved. X.bp X.PP X.PP X.PP X.PP X.PP X.PP X.bp X.NH XIntroduction X.br X.PP XThese programs are intended to assist observational astronomers. X.PP XStarchart produces astronomical charts from a variety of databases, Xproducing output for, in rough order of quality, PostScript, X11, Xsunview, Atari St, IBM PC, X10, tektronix, unix plot, HP laserjet, and Xtty displays, on Unix, vms and other systems. It is straightforward to Xwrite drivers for other output devices. Observe is a multifunction Xprogram for use in planning an observing session. It calculates the Xpositions of planets and their satellites, asteroids and comets, Xcalculates rising and setting times, and much more. X.PP X.PP XThis software may be redistributed freely, not sold. X.PP XNo representation is made about the suitability of this Xsoftware for any purpose. It is provided "as is" without express or Ximplied warranty, to the extent permitted by applicable law. X.PP X.sp 2 X.SH XDISCLAIMER\ OF\ WARRANTY X.br X.PP XThe author disclaims all warranties with regard to this software to Xthe extent permitted by applicable law, including all implied Xwarranties of merchantability and fitness. In no event shall the Xauthor be liable for any special, indirect or consequential damages or Xany damages whatsoever resulting from loss of use, data or profits, Xwhether in an action of contract, negligence or other tortious action, Xarising out of or in connection with the use or performance of this Xsoftware. X.PP X.PP X.PP X.NH 2 XWhat\ the\ Programs\ Do X.br X.PP XSeveral programs are included in this package, all intended to aid Xobservational astronomers. The \fBobserve\fR program calculates positions Xof moving objects and helps in planning an observing session. There are Xseveral starchart programs for preparing astronomical charts; there is a Xseparate program for each output device. There are also several support Xprograms which operate on data files for these programs. X.PP XStarchart programs are quite general star map drawing programs and Xhave many potential uses, but their unique utility is in preparing Xcustom charts for particular observing projects, finding charts, and a Xpages that can be put in observing notebook and annotated at will. X.PP XThe \fBobserve\fR program provides many facilities of use in planning Xan observing session. It can generate ephemerides of planets, minor Xplanets, and comets, and puts the coordinates in files to be used with Xstarchart programs. It calculates the approximate altitude and azimuth Xof obects at sun rise and set and morning and evening twilights. It can Xcalculate positions of the major satellites of Jupiter and Saturn. Of Ximportance to observers is the generation of the timetable of events for Xa night. X.PP XOther programs are provided to facilitate the use of these programs. X.PP X.NH 2 XThe\ Sky X.br X.PP XThere is a sky. There are things in the sky. The starchart programs Xdraw maps of things in the sky. The \fBobserve\fR program helps you plan Xto look at things in the sky. X.PP XThe things in the sky include stars, planets, nebulae, clusters of Xstars, and galaxies. For thousands of years, people have grouped the Xstars in the sky into patterns, and constellations. More recently, the Xsky has been divided into areas based on these constellations. For Xhundreds of years, astronomers have used a latitude-longitude grid for Xdefining the locations of celestial objects. The longitude is usually Xreferred to as right ascension or RA, the latitude is the declination or XDEC. Through the year, the sun follows a path in the sky, called the XEcliptic, which is the plane of the earth's orbit. Other planets in the Xsolar system are roughly in this plane. X.PP XThe locations of stars, nebulae, clusters, and galaxies have been Xtabulated for hundreds of years. These programs use computerized forms Xof such databases. X.PP X.NH 2 XCoordinates X.br X.PP XYou should be familiar with the method of specifying a location on the Xsurface of the earth: two coordinates are used: latitude north of the Xequator and meridian of longitude east of Greenwich. A similar system Xis used to specify the locations of points in the sky. the meridians Xare called right ascension, and the latitude is called declination. XRA is measured from the point at which the sun crosses the equator in XMarch. It is measured in hours, with 15 degrees = 1 hour. X.PP XThere are two other coordinate systems commonly used in addition to XRA--dec. These apply only to a particular observation location and Xtime. The first of these is Hour angle -- declination. It is similar Xto R.A.--declination, but instead of R.A., the angle is measured west Xfrom the line from north to south passing directly overhead. The second Xis altitude -- azimuth (alt--az): altitude in degrees above the horizon Xand azimuth in degrees east from north. X.PP X.NH 2 XEpoch\ and\ Equinox X.br X.PP XThe coordinates of a ``fixed'' object are actually only approximately Xconstant. Two factors change the coordinates in R.A. and declination. X.PP X.NH 3 XProper\ Motion\ and\ Epoch X.br X.PP XFirst, stars (and other galactic objects) are not fixed in space. The Xsun and stars all move. Only the closer stars move significantly, but Xcloser stars are also brighter, so this is an important effect. The X\&\fIepoch\fR is the time for which the coordinates are valid including Xthe effects of this \fIproper motion\fR. X.PP X.NH 3 XPrecession\ and\ Equinox X.br X.PP XThe second and more important factor is that the R.A. and dec. Xcoordinate system changes: the north pole and thus the equator change Xdue to \fIprecession\fR. R.A. changes as the equator moves and changes Xthe point at which the sun crosses the equator. The \fIequinox\fR date, Xor \fIequator and equinox\fR is the time at which the coordinate system Xis valid. Equinox 2000.0 and 1950.0 are commonly used coordinate Xsystems. The equator and equinox of the date is also occasionally Ximportant. X.PP XThe starchart programs use data in equinox 2000.0 coordinates. X.PP X.NH 2 XAdditional\ Corrections\ to\ Positions X.br X.PP XPrecession and epoch were discussed above. In addition there are Xsmaller effects which must be considered for precise astrometry. These Xinclude effects of motion about the earth-moon barycenter, light travel Xtime, nutation, and aberration of starlight. X.PP X.NH 2 XMagnitudes X.br X.PP XMagnitudes are defined with respect to standards. X.PP XObjects emit photons. The number of photons per second observed from an Xobject under given conditions and equipment is the intensity of light. XA brighter object emits more photons. The difference in magnitudes Xbetween two objects is -2.5 times the log (base 10) of the ratio of Xintensities, i.e. Xm = m_std - 2.5 log(s/s_std) X.PP XMagnitudes are measured in different ways. The most important are Xvisual, photographic, and photometric. Visual and photographic Xmagnitudes are measured using those methods to estimate relative Xmagnitudes. Photometry is the counting of photons received from Xobjects. Standard filters are generally used. The most common set is XUBVRI, Ultraviolet to Infrared. The V filter approximates the response Xof the eye, while the B filter is approximately the response of Xphotographic film. X.PP XFor a magnitude number to be truely meaningful, the system used must be Xspecified. Generally V or visual may be assumed. X.PP XFor many objects (V-B), that is the magnitude measured photometrically Xwith the V filter minus the B magnitude, indicates the color of the object. X.PP X.NH 2 XTime\ and\ Date X.br X.PP XTime is a very complex subject. X.PP X.NH 3 XTime X.br X.PP XTime systems include UT (= UT1), UT0, TA1, and UTC. These times may Xdiffer by a second or so. They are based on the rotation of the earth. XAs the earth slows, and since the day is not \fIexactly\fR 86400 seconds Xlong, leap seconds are occasionally inserted. They are all Xapproximately the time at 0 degrees longitude. Most astronomical times Xare quoted in UT (universal time). The differences are rarely critical Xfor amateurs. X.PP XAnother significant time system TDT (formerly ET), and TBT. TDT or XTerrestrial Dynamical Time is based on the orbits of the planets, as is XTBT or Terrestrial Barycentric Time (based on the center of motion of Xthe earth-moon system). These times currently differ from UT by about a Xminute. TDT is the time which should be used for planetary calculations. X.PP XTime zones relate local time to the time at 0 longitude. Be aware that Xthere are some fractional time zones in the world. Daylight savings Xtime (or ``summer'' time) is an additional complication. You should Xlearn how your time zone is related to the time at 0 longitude (UT or XGMT). EST is 5 hours behind, EDT is 4 hours behind. X.PP XThese times are all related to the position of the sun: the sun should Xbe overhead at about noon local standard time. A different time is X\&\fIsidereal\fR time, based on the positions of the stars overhead. Two Ximportant sidereal times are GST or Greenwich Sidereal time, and LST or Xlocal sidereal time. X.PP X.NH 3 XDate X.br X.PP XCalendars are confused and confusing. To avoid confusion between the Xmany calendars in use historically, JD \fIJulian date\fR is used. The XJD 0 is a day more than 4000 years BC (BCE). X.PP X.NH 2 XAtmospheric\ Effects X.br X.PP XRefraction affects alt-az coordinates: light from objects are bent Xby the atmosphere, making them appear higher in the sky than they would Xif there were no atmosphere. The error can reach 34 minutes of arc at the Xhorizon. Extinction, absorption and scattering make objects fainter the Xmore atmosphere the light from them must pass through (that is, the Xcloser to the horizon they are). Other effects of the atmosphere are Xseeing (the effect which produces twinkling of stars), scintillation, Xairglow, and of course light pollution. X.PP X.NH 2 XElements\ of\ an\ Observing\ Session X.br X.PP XTo avoid frustration and ensure meeting goals you should plan your Xobserving session in advance. More serious the goal the more carefully Xyou should plan. At least, having a plan may help you avoid wondering Xwhat to do next on a clear night. X.PP XA timeline of events ensures that an object will be observable, and Xhelps schedule a night to observe all objects when they are well placed. XThe events are sun and moon rise and set, astronomical twilight, and the Xrising, setting and transit times of objects. In addition, objects Xshould be observed when possible when they are above 30 degrees above Xthe horizon, or at least above 20 degrees. These times should also be Xnoted in the time line. X.PP XCharts are used in identifying planets, asteroids, and comets, and Xfinding objects. For very faint objects, a photographic atlas of the Xarea should be xeroxed. X.PP XA notebook is an important part of observing. It can be of scientific Xnotebook quality, or a simple note of what objects you observed and how Xthey looked. Starchart programs may be used to produce finder charts Xwhich you can annotate and keep in a notebook. X.PP X.NH 2 XHints X.br X.PP XUse grep, awk and shell scripts. Unix tools can be very helpful in many Xsituations. X.PP X.PP X.PP X.bp X.NH XObserving X.br X.NH 2 XThe\ \fBobserve\fR\ Program X.br X.PP XThis program is used to prepare for astronomical observations and for Xephemeris calculation. It can calculate the position of the major Xplanets, the satellites of Jupiter and Saturn, and minor planets and Xcomets given either orbital elements or a tabulated ephemeris. XCoordinates of stationary objects may also be input. It calculates X(approximate) rise and set times, and transit times, of all objects to Xbe observed. It calculates the (approximate) altitude and azimuth of Xobjects at sun rise and set, and morning and evening twilight. X.PP XThe information (coordinates, rise and set times) may be prepared for Xeither a single time or a sequence of times. X.PP XOutput includes a file containing the timetable of events for the Xevening or evenings. The coordinates of the sun and moon, plus any Xplanets, minor planets, and comets are placed in a readable text file, Xwith other calculated values for solar system objects (e.g. distance to Xearth). The coordinates of all objects to be observed are placed in Xfiles in formats to be read by the other programs in this family, namely X\&\fBdataconv\fR and the starchart charting programs. A file listing the X(approximate) altitude and azimuth of objects at sun rise and set, and Xmorning and evening twilight is output. If satellite positions are to Xbe computed, these coordinates are placed in one file, and a separate XPostScript file graphically showing their positions relative to the Xprimary is also produced. X.PP XThese output files are optional: any subset of the possible output files Xmay be produced. X.PP XParameters set the location of the observer, control what objects are to Xbe observed, and designate the time or times of interest. X.PP XCurrently, there are some limitations to the program: X.IP X.IP \(bu\ XMinor corrections such as parallax and nutation are not made. X.IP X.IP \(bu\ XPositions are accurate enough for most applications other than Xoccultations. X.IP X.IP \(bu\ XRise and set times may be off by several minutes. X.IP X.IP \(bu\ XPositions of Saturn's satellites are approximate, good enough for Xidentification of satellites. X.PP X.PP X.PP X.NH 2 XControls\ and\ Input\ for\ the\ \fBobserve\fR\ program X.br X.PP XCommand line options set the location of the observer, control what Xobjects are to be observed, control the output files produced, and Xdesignate the time or times of interest. The default location of the Xobserver is set when the program is compiled. X.PP X.IP \f(CW\`-m\'\fR\ XMeridian of longitude, measured East of Greenwich. The USA is West of XGreenwich, and the longitude is negative for all USA locations. One to Xthree numbers can be used: degrees, degrees and minutes, or degrees Xminutes and seconds. X.IP X.IP \f(CW\`-l\'\fR\ XLatitude. One to three numbers can be used: degrees, degrees and Xminutes, or degrees minutes and seconds. X.IP X.IP \f(CW\`-a\'\fR\ XAltitude in meters. X.IP X.IP \f(CW\`-z\'\fR\ XTime zone in hours East of Greenwich, again, this number is negative Xfor USA locations. This does not include any effects of daylight Xsavings. X.IP X.IP \f(CW\`-d\'\fR\ XThe date or dates of observation in UT are specified with this flag. XThe dates for the \f(CW\`-d\'\fR option are each specified as a string Xconsisting of month, day, and optional year (use if different from the Xcurrent year). The month may be encoded as above, e.g. \f(CW\`Aug\'\fR for Xaugust. Using the first three letters of the English name for the month Xalways works, as does the Roman numeral form. Some other common Xabbreviations also work. The year may also be specified, the default is Xthe current year. The day may be fractional, e.g. 1.25 is 6 am UT on Xthe first. An optional third parameter is the increment of time to be Xused in stepping between the two dates. X.IP X.IP \f(CW\`-o\'\fR\ XThis sets names used for the output files and controls which output Xfiles are produced. The output file names all have the form X\&\f(CW\`\fIoutfile_root\fR.XXX\'\fR, where \fIoutfile_root\fR is set at Xcompile time (usually to \f(CW\`planet\'\fR), or is set to the argument for Xthis option. The \f(CW\`-o\'\fR may be followed with a letter or letters from Xthe set "aeios" to select the altaz, eph, sif, obs, and star files, Xrespectively. e.g. \f(CW\`-oae austin\'\fR would produce only the output files X"austin.altaz" and "austin.eph". X.IP X.IP \f(CW\`-p\'\fR\ XThe positions of any or all of the major planets at the time(s) may be Xcalculated. This is specified either as \f(CW\`-p\'\fR which causes the Xpositions of all planets to be calculated, or individual planets may be Xspecified by following the \f(CW\`-p\'\fR with a letter or letters from the Xsequence "MVmJsUN". The positions of the sun and moon are always Xcalculated, since they always have some effect on observing conditions. X.IP X.IP \f(CW\`-s\'\fR\ XThe -s option causes the \f(CW\`.sat\'\fR and \f(CW\`.sat_PS\'\fR files to be Xproduced for the satellites of Jupiter and Saturn. \f(CW\`-s\'\fR implies X\&\f(CW\`-p\'\fR. With the \f(CW\`-si\'\fR option the drawings in the PS file are Xflipped north to south (if for one time) or east to west (if for Xmultiple times) to produce an inverted view. X.IP X.IP \f(CW\`-f\'\fR\ XInput object data is contained in files in several formats. The X\&\f(CW\`-f \fIfilename\fR \fIformat\fR\'\fR option sets this input file. X.IP X.IP \f(CW\`-n\'\fR\ XFor some input file formats, the name of the object must be specified Xusing the \f(CW\`-n\'\fR option. X.IP X.PP XSample data files should be used for the file formats used for input Xfiles. The format names are \f(CW\`obj\'\fR for fixed objects, \f(CW\`ell_e\'\fR Xand \f(CW\`par_e\'\fR for parabolic orbital elements, and \f(CW\`emp\'\fR, X\&\f(CW\`empb\'\fR, \f(CW\`aa\'\fR, \f(CW\`st\'\fR, and \f(CW\`iau\'\fR for tabulated Xephemerides. The fixed object format contains the coordinates, name, Xmagnitude, type and size of objects to be observed. The other file Xformats are used for comets and minor planets, and are discussed below. X.PP X.PP XThe output files are named \f(CW\`\fIoutfile_root\fR.XXX\'\fR where XXX is: X.IP \f(CW\`altaz\'\fR\ Xaltitude and azimuth of objects at sun rise and set, and morning and Xevening twilight. X.IP X.IP \f(CW\`eph\'\fR\ Xephemeris of sun, moon and objects specified. X.IP X.IP \f(CW\`obs\'\fR\ Xobservability of objects: rise and set times of objects, twilight times, Xetc. X.IP X.IP \f(CW\`star\'\fR\ X\&\f(CW\`lineread\'\fR format file containing coordinates (equinox 2000) of the Xobject(s), sun, moon. X.IP X.IP \f(CW\`sif\'\fR\ X\&\f(CW\`sif\'\fR format file containing the same information as the .star file. XThe separation character is \f(CW\`;\'\fR. X.IP X.IP \f(CW\`sat\'\fR\ XLocations of the major satellites of Jupiter and Saturn with respect to Xthe primary. X.IP X.IP \f(CW\`sat_PS\'\fR\ XPostScript file drawing either: one page showing appearance of Jupiter Xand Saturn with satellites, and relative sizes and orientations of XMercury, Venus, Mars, Jupiter, and Saturn, and the Moon; or several Xpages showing Jupiter and Saturn with moons on a sequence of times if a Xrange of dates was specified. X.IP X.PP X.NH 2 XPlanetary\ Positions X.br X.PP XPlanetary positions are calculated with moderate precision. Formulae Xare largely from \fIAstronomical Formulae for Calculators\fR by Jean XMeesus. Minor corrections are currently ignored. X.PP X.NH 2 XComets\ and\ Minor\ Planets X.br X.PP XComets and minor planet positions may be calculated either directly from Xthe orbital elements or by interpolating a tabulated ephemeris. The Xcalculation from orbital elements is most convenient, but the tabulated Xephemeris is likely to be slightly more accurate. X.PP X.PP X.NH 3 XOrbits X.br X.PP XThe coordinates of objects in elliptical or parabolic orbits may be Xcalculated from orbital elements given in files of format \f(CW\`ell_e\'\fR Xand \f(CW\`par_e\'\fR respectively. X.PP XOrbital elements are: X.IP \f(CW\`a\'\fR\ Xsemimajor axis, A.U. X.IP X.IP \f(CW\`q\'\fR\ Xperihelion distance, A.U. X.IP X.IP \f(CW\`e\'\fR\ Xeccentricity X.IP X.IP \f(CW\`i\'\fR\ Xinclination (degrees) X.IP X.IP \f(CW\`omega\'\fR\ Xargument of perihelion X.IP X.IP \f(CW\`Omega\'\fR\ Xlongitude of ascending node X.IP X.IP \f(CW\`n\'\fR\ Xmean motion (degrees/day) X.IP X.IP \f(CW\`M\'\fR\ XMean anomaly at epoch X.IP X.IP \f(CW\`T\'\fR\ XTime of perihelion. X.IP X.PP XFor elliptical orbits, \f(CW\`q\'\fR and \f(CW\`T\'\fR are not needed; for Xparabolic orbits, only \f(CW\`q\'\fR, \f(CW\`i\'\fR, \f(CW\`omega\'\fR and \f(CW\`Omega\'\fR Xare needed. X.PP X.PP XOrbital elements are referred to a certain equinox, and apply on a Xcertain epoch date. X.PP XIf \f(CW\`a\'\fR is not given, it may be calculated from \f(CW\`a\'\fR = X\&\f(CW\`q\'\fR/(1-\f(CW\`e\'\fR). X.PP XIf \f(CW\`n\'\fR is not given, it may be calculated from \f(CW\`n\'\fR = X0.985609/(\f(CW\`a\'\fR*sqrt(\f(CW\`a\'\fR)). X.PP XIf \f(CW\`M\'\fR is not given, use \f(CW\`M\'\fR = (\f(CW\`Epoch_date\'\fR - \f(CW\`T\'\fR) X* \f(CW\`n\'\fR. X.PP XThe magnitude of an asteroid may be calculated from two parameters: X\&\f(CW\`G\'\fR and \f(CW\`H\'\fR. The magnitude of a comet may be calculated from Xthe parameters \f(CW\`g\'\fR and \f(CW\`kappa\'\fR. X.PP X.NH 3 XInterpolation\ of\ Ephemerides X.br X.PP XAll ephemeris formats have date, RA, DEC, then other info. Date is the Xmonth in characters, then the day of the month. How the month is Xencoded is format dependent, examples include \f(CW\`IX\'\fR \f(CW\`Sept.\'\fR X\&\f(CW\`Sep\'\fR \f(CW\`Sep.\'\fR \f(CW\`September\'\fR. Year is current year unless Xspecified in command line, and is the year of the first date. Dates Xmust be in increasing order: 3 followed by 4, December followed by XJanuary. X.PP XThe formats are: X.IP \f(CW\`emp\'\fR\ XFormat used in the Russian \fIEphemerides of minor planets\fR. X.IP X.IP \f(CW\`empb\'\fR\ XFormat used in the Russian \fIEphemerides of minor planets\fR for Xbright and unusual asteroids. X.IP X.IP \f(CW\`aa\'\fR\ XFormat used by the \fIAstronomical Almanac\fR. X.IP X.IP \f(CW\`st\'\fR\ XFormat commonly used by \fISky and Telescope\fR magazine. X.IP X.IP \f(CW\`iau\'\fR\ XFormat commonly used by IAU Circulars. X.PP X.NH 2 XTime\ Line\ of\ Events X.br X.PP XThe \f(CW\`.obs\'\fR file contains a timeline of events for the night or nights Xof observation. Events include sun and moon rise and set, morning and Xevening twilight, and for each object to be observed: the rise and set Xtimes, the times when they are 20 degrees and 30 degrees above the Xhorizon, and the time of their transit (when they cross the line from Xnorth to south passing directly overhead, and are at their maximum Xaltitude above the horizon). X.PP XThe times, especially sun and moon rise and set are approximate. X.PP XThe timeline should help you plan your evening, so you know when to Xbegin and end (twilight), and when the moon will interfere. It helps Xyou plan to observe the objects when they are well placed, and ensure Xthat you can observe an object before it has fallen too low in the sky. X.PP X.NH 2 XSatellites\ of\ Jupiter\ and\ Saturn X.br X.PP XThe positions of the major satellites of Jupiter and Saturn are Xcalculated for the time or times of interest. The Saturn satellite Xpositions in particular are approximate, but are certainly good enough Xfor identification purposes. X.PP XThe positions are output in the \f(CW\`.sat\'\fR file, and also illustrated in XPostScript in the \f(CW\`.sat_PS\'\fR file. X.PP XIf more than one time is specified, the PostScript program draws many XJupiters and Saturns with their moons on a page (with separate pages for XJupiter and Saturn). If one time is specified, a single page is Xproduced containing large drawings of Jupiter and Saturn with their Xmoons. As a bonus, this single page also illustrates the phases and Xorientations of Mercury, Venus, Mars, Jupiter and Saturn (with rings), Xand the moon. X.PP X.bp X.NH XCharts X.br X.NH 2 XThe\ Starchart\ Programs\ X.br X.PP XThe starchart programs are variations of a single program, producing Xoutput for different output devices. All the programs produce Xastronomical star charts from available databases. X.PP X.PP X.PP X.NH 2 XPurpose\ of\ Starchart X.br X.PP XThe starchart programs have many potential uses: in education, preparing Xillustrations, becoming familiar with the constellations and the sky; Xbut it is primarily useful for preparing for observing. It can prepare Xlarge scale maps, finder charts, variable star charts, and illustrations Xfor inclusion in an observing notebook. X.PP XA variety of map projections are available for various needs. X.PP X.NH 2 XFeatures X.br X.PP XThere are many many features of potential use. The programs can: X.IP X.IP \(bu\ XAllow for the creation of star charts of medium quality, comparable to Xpublished works in data content. X.IP X.IP \(bu\ XAllow for the creation of custom star charts for use as finder maps for Xspecific objects, including the labeling of stars with their magnitudes. XInverted maps may also be produced. X.IP X.IP \(bu\ XAllow for the creation of figures of the sky overhead at any location Xand time, as in the Sky and Telescope centerfold, or planispheres. X.IP X.IP \(bu\ XOptionally include in the above: planets (including the sun, moon, Xasteroids, comets), fixed stars, nebulae, clusters, etc., lines for Xconstellation shapes, constellation boundaries, paths of planets, the Xecliptic, galactic equator, milky way isophots, etc. X.IP X.IP \(bu\ XUse color for objects, and stars by spectral type, when available for Xthe given device. X.IP X.IP \(bu\ XLabel stars with their name, number or letter, and/or magnitude. X.IP X.IP \(bu\ XLabel other objects by name. X.IP X.IP \(bu\ XAllow custom star databases to be used to produce maps of the sky in, Xfor example, 10,000 B.C. X.IP X.IP \(bu\ XInteract on the display to allow for interactive sky exploration, if the Xdevice supports such interaction. X.PP XStarchart is intended to produce useful displays on any available Xdevice, and to produce best results on high quality graphics printers, Xespecially those using PostScript. Output may be captured in files to Xbe edited for especially customized maps. Comments are included in the Xoutput whenever possible to facilitate this editing. Given a good Xobject-oriented editor, professional quality maps may be easily Xproduced. X.PP XThe program has a set of core routines for user interface and data Xinput, while a set of specialized driver routines is provided for each Xoutput device. X.PP X.NH 2 XNon-\ and\ Mis-\ Features X.br X.PP XThere are some limitations remaining. X.PP XThe output is limited by the capabilities of the device. However, even Xthe best of the drivers has the following problems: it cannot detect and Xavoid overlapping labels and stars, and it cannot allow the user to Xinteract with the display and move the labels. These limitations are Xwhat distinguish the output from these programs from a professionally Xprepared map. X.PP XThe current programs do not have user configurable Legend areas. X.PP X.NH 2 XObjects\ Drawn X.br X.PP XThe objects drawn currently include: X.PP X.IP \f(CW\`Stars\'\fR\ XSize represents the magnitude. For most devices, this is done by Xrounding to the nearest integer magnitude, and drawing the star based on Xthis; however, some versions, e.g. \fBstarpost\fR for PostScript, allow Xfor continuous scaling of the size. Color is determined from the star's Xspectral class. X.IP X.IP \f(CW\`Planets\'\fR\ XOn some devices, separate symbols are drawn for each planet, on others Xthey are all represented by the same symbol. Major planets should be Xdistinguished from comets and asteroids. Color may be assigned in the Xdatabase file. X.IP X.IP \f(CW\`Nebulae\'\fR\ XDiffuse, planetary and unspecified nebulae may be Xdistinguished. If the device can support it, size may represent the Xdiameter of the nebulae (if provided in the database). Color may be Xassigned in the database file. X.IP X.IP \f(CW\`Galaxies\'\fR\ XSpiral, elliptical and unspecified galaxies may be Xdistinguished. If the device can support it, size may represent the Xdiameter of the galaxy (if provided in the database). Color may be Xassigned in the database file. X.IP X.IP \f(CW\`Clusters\'\fR\ XOpen, globular and unspecified clusters may be Xdistinguished. If the device can support it, size may represent the Xdiameter of the cluster (if provided in the database). Color may be Xassigned in the database file. X.IP X.IP \f(CW\`Other\'\fR\ XOther identified objects. If the device can support it, Xsize may represent the diameter of the object (if provided in the Xdatabase). Color may be assigned in the database file. X.IP X.IP \f(CW\`Unknown\'\fR\ XFor objects which haven't been identified. If the Xdevice can support it, size may represent the diameter of the object X(if provided in the database). Color may be assigned in the database Xfile. X.IP X.IP \f(CW\`Vectors\'\fR\ XSolid, dashed, or dotted lines may be drawn using commands in a Xdatabase. Lines are drawn as projected segments of great circles, or by Xlinear interpolation in latitude and longitude between endpoints. Not Xall line styles may be supported on some devices. Color may be assigned Xin the database file. X.IP X.IP \f(CW\`Text\'\fR\ XInvisible objects in a database are used to place text Xlabels in the chart. X.IP X.IP \f(CW\`Comments\'\fR\ XLines for comments are allowed in database files. They have no effect Xon displayed output. X.IP X.IP \f(CW\`Filled\ areas\'\fR\ XImplemented as filled areas when possible for the device, otherwise as Xoutlines. Area boundaries may be segments of great circles or defined Xby linear interpolation in latitude and longitude between endpoints. X.PP X.NH 2 XProjection\ Modes X.br X.PP XThere are currently five projection modes available for a map. The Xdefault is Sanson's sinusoidal projection, which is area-preserving, but Xfails near the poles. This projection preserves both area and linearity Xin Declination (y axis). It gives good conformality (angle correctness) Xnear the equator, so it is useful along the Ecliptic. Lines of RA Xconverge at the poles (unlike cylindrical projections), though XCassiopeia and the Dipper reproduce well. X.PP XStereographic projection keeps circles circles, and can be used near the Xpoles. X.PP XOrthographic projection is simple but very distorting; it is as if the Xsphere of the sky were finite in size and viewed from infinity. X.PP XGnomonic projection projects great circles as straight lines, and is Xtherefore very useful for charts to be used to plot meteor paths. See Xfor example the October 1988 \fISky and Telescope\fR. X.PP XRectangular projection is the simplest: latitude and longitude are Xtranslated directly to x and y of the map. Note that this is neither Xcylindrical nor Mercator projection. X.PP XOnly the main map projection mode may be changed through the command Xline and \f(CW\`.starrc\'\fR format control files; \f(CW\`mapwin\'\fR control may change Xthe projection mode of the thumbnail map. X.PP X.NH 2 XThe\ Chart X.br X.PP XA \fIchart\fR is a single page or display region. Within that region are Xone or more \fImap windows\fR, each of which may have an associated X\&\fIlegend\fR region. Each map window is independent of others. Its Xattributes are defined in a structure which contains its location and Xsize, and parameters and flags used in determining what is placed in the Xwindow. The detailed appearance of each graphic element to be displayed Xin the window is up to the driver. The starchart main routines only Xdefine the location of the element, and report which routine is calling Xthe display function. For each line in every star, planet, vector, or Xother file, the main routines determine only \fIwhat\fR is to be Xdrawn, and \fIwhere\fR on the entire device page it appears. The Xdevice specific drivers determine exactly how it appears on the Xdevice. X.PP XThe page may have a title region, which is drawn once per page. This Xregion is entirely left to the driver. X.PP XThe initial values of map window structures are set in the device Xdriver. User input from the \f(CW\`.starrc\'\fR file and the command line may Xchange these values, and then the driver has an opportunity to override Xall settings, possibly through additional user input. The structure may Xbe read and written to \f(CW\`mapwin\'\fR files, which may be used for input to Xdifferent drivers and (carefully) editted by the user. X.PP X.NH 3 XLayers X.br X.PP XA map window consists of several \fIlayers\fR. All layers are optional. XThe order of layers is determined independently for each map window. X.PP XA map window has an \f(CW\`outline\'\fR, which is determined by the projection Xmode. For the Sanson's projection, RA and DEC tick axes are drawn. X.PP XA grid of arbitrary origin and spacing in RA and DEC may be drawn. XThe RA and DEC lines are in two separate layers, called \f(CW\`ra_grid\'\fR Xand \f(CW\`dec_grid\'\fR. X.PP XThe \f(CW\`ecliptic\'\fR is a separate layer. X.PP XA file defining constellation \f(CW\`boundaries\'\fR is provided, in X\&\f(CW\`lineread\'\fR format. The file contains vectors which are drawn in a Xseparate layer. Similarly, a \f(CW\`patterns\'\fR file contains figures Xfor the constellations. A third file and layer provides names for the Xconstellations (\f(CW\`constlnames\'\fR). X.PP XFinally the set of files defined by the user is plotted. These Xcurrently include by default and in order a star file \f(CW\`yale.star\'\fR, Xa file which is an index to files separated by region of sky called X\&\f(CW\`index.indx\'\fR, a nebula database \f(CW\`neb.star\'\fR, and a planet Xlocation file \f(CW\`planet.star\'\fR. Additional files may be furnished by Xthe user. X.PP XThe default is to treat these as one layer, \f(CW\`allfiles\'\fR, and draw Xthe objects in each file in order. Alternatively, for each map window, Xthe order may be changed to draw all the symbols in all the files Xfollowed by all the names in all the files, etc. The supported elements Xwhich are controlled by the data files are: glyph (symbol of object), Xname (text to the right of object), magnitude label (text below and to Xthe right of object), vectors, and filled areas. These are layers X\&\f(CW\`allfiles\'\fR, \f(CW\`allglyphs\'\fR, \f(CW\`allnames\'\fR, \f(CW\`allmaglbls\'\fR, X\&\f(CW\`allvectors\'\fR, and \f(CW\`allareas\'\fR. X.PP XEach file has its own cutoff magnitudes for visibility of objects symbol X(\fImaglim\fR) name label (\fIlbllim\fR) and Bayer/Flamsteed label X(\fIgklim\fR). X.PP XFinally, a \f(CW\`legends\'\fR layer displays the legends area, if any, for a Xwindow. X.PP XTo stress: any layer in any window may be skipped, and they may be drawn Xin any order, independently. X.PP X.NH 2 XUser\ Controls X.br X.PP XAs many chart controls as feasible may be set by various methods of Xuser interaction. X.PP X.PP X.NH 3 XCommand\ Line\ Controls X.br X.PP END_OF_FILE if test 33987 -ne `wc -c <'doc/as.ms.aa'`; then echo shar: \"'doc/as.ms.aa'\" unpacked with wrong size! fi # end of 'doc/as.ms.aa' fi echo shar: End of archive 24 \(of 32\). cp /dev/null ark24isdone MISSING="" for I in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 ; do if test ! -f ark${I}isdone ; then MISSING="${MISSING} ${I}" fi done if test "${MISSING}" = "" ; then echo You have unpacked all 32 archives. rm -f ark[1-9]isdone ark[1-9][0-9]isdone else echo You still need to unpack the following archives: echo " " ${MISSING} fi ## End of shell archive. exit 0