ecd@cs.umn.edu@ncs-med.UUCP (Elwood C. Downey) (03/11/90)
Posting-number: Volume 11, Issue 7
Submitted-by: ecd@cs.umn.edu@ncs-med.UUCP (Elwood C. Downey)
Archive-name: ephem4.12/part06
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X Ephem V4.12 - February 20, 1990
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X Copyright (c) 1990 by Elwood Charles Downey
X Chaska, Minnesota, USA
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X Table of Contents
X 1. Introduction ................................................... 3
X 2. Running Ephem .................................................. 3
X 2.1. Command Line Format .......................................... 3
X 2.2. Program Operation ............................................ 4
X 3. Screen Fields .................................................. 5
X 3.1. Top Screen Fields ............................................ 5
X 3.2. Data format columns .......................................... 6
X 3.3. RiseSet format columns ....................................... 7
X 3.4. Separation format fields ..................................... 7
X 4. Date and Time Formats .......................................... 7
X 5. Configuration File ............................................. 8
X 5.1. Configuration File fields .................................... 8
X 5.2. Example ephem.cfg ............................................ 10
X 6. Menu options ................................................... 10
X 6.1. Adaptive vs. Standard hzn .................................... 11
X 6.2. Geocentric vs. Topocentric ................................... 11
X 7. Object X ....................................................... 11
X 7.1. Controlling Object-X Operation ............................... 12
X 7.1.1. Fixed coordinates .......................................... 12
X 7.1.2. Elliptical elements ........................................ 12
X 7.1.3. Parabolic elements ......................................... 12
X 7.1.4. On or Off .................................................. 13
X 8. Plotting ....................................................... 13
X 8.1. Defining plot fields ......................................... 13
X 8.2. Displaying a plot file ....................................... 14
X 8.3. Cartesian or Polar coords .................................... 14
X 8.4. Begin Plotting ............................................... 14
X 8.5. Stopping Plotting ............................................ 14
X 9. Watching ....................................................... 14
X 9.1. Trails ....................................................... 15
X 9.2. Night sky .................................................... 15
X 9.3. Solar System ................................................. 15
X 10. Searching ..................................................... 15
X 10.1. Find extreme ................................................ 16
X 10.2. Find 0 ...................................................... 16
X 10.3. Binary ...................................................... 16
X 10.4. Define a New function ....................................... 16
X 10.4.1. Intrinsic functions ....................................... 17
X 10.4.2. Field Specifiers .......................................... 17
X 10.4.3. Constants ................................................. 17
X 10.4.4. Operators ................................................. 18
X 10.5. Specifying Search Accuracy .................................. 18
X 10.6. Stop ........................................................ 18
X 10.7. Example Searches ............................................ 18
X 10.8. Another Example ............................................. 19
X 10.9. Caution ..................................................... 19
X 11. Implementation Notes .......................................... 20
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X 11.1. Program limits .............................................. 20
X 12. DOS Installation Procedure .................................... 21
X 12.1. Setting TZ .................................................. 21
X 13. Wish List ..................................................... 21
X 14. Sample Screens ................................................ 23
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X 1. Introduction
X
X Ephem is a program that displays observing circumstances for all the
X planets plus any one additional object. The additional object may be fixed
X or specified via heliocentric elliptical or parabolic orbital elements to
X accommodate solar system objects such as comets or asteroids.
X
X Information displayed about each object includes RA and Dec precessed to
X any epoch, heliocentric coordinates, local azimuth and altitude, distance
X from sun and earth, solar elongation, angular size, visual magnitude,
X illumination phase, local rise, transit and set times, length of time up,
X and topocentric or geocentric angular separations between all combinations
X of objects.
X
X Observing circumstance information includes UTC and local date and time,
X local sidereal time, times of astronomical twilight, length of day and
X night, local temperature, pressure and height above sea level for the
X refraction model and a monthly calendar.
X
X RA/Dec calculations are geocentric and include the effects of light travel
X time, nutation, aberration and precession. Alt/az and rise/set/transit
X and, optionally, angular separation calculations are topocentric and
X include the additional effects of parallax and refraction.
X
X A running plot file of selected field values may be generated as the
X program runs. Ephem includes a very crude quick-look facility to view
X these plot files or they may be plotted by other programs.
X
X One may watch the night sky or the solar system with a simple screen-
X oriented display.
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X Ephem may be asked to search for interesting conditions automatically,
X using several algorithms. Most fields displayed on the screen may be used
X as terms in an arbitrary arithmetic expression that can be solved for zero
X or minimized or maximized, or the time of state change of any boolean
X expression can be found.
X
X The program is written in C for unix or DOS. It uses only a very simple
X set of io routines and should be easily ported to any ASCII display.
X
X The planetary data and correction algorithms are taken, with permission,
X from "Astronomy With Your Personal Computer", by Peter Duffett-Smith,
X Cambridge University Press, 1985.
X
X 2. Running Ephem
X
X
X 2.1. Command Line Format
X
X To run ephem, just type "ephem". You may also optionally specify an
X alternate configuration file, and optionally specify values for several
X screen fields. The command line syntax can be summarized as follows:
X
X ephem [-c <configfile>] [field=value ...]
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X 2.2. Program Operation
X
X When ephem starts, it first displays a disclaimer banner. Then, after any
X key is pressed, it reads a configuration file to set the initial values of
X several fields. The default file name is ephem.cfg or .ephemrc in the
X HOME environment variable directory if available. The exact format of the
X file is described below. Then it processes any additional command line
X arguments exactly as it would if they too came from the configuration
X file. (See the later section on this manual for a description of the
X possible entries.) It then draws all fields on the screen with their
X initial values. The program then loops advancing time each step, by some
X amount you may control, and updating all fields each loop.
X
X There are two fields that control this looping behavior: NStep and StpSz.
X These control the number of steps and the amount of time to add each step,
X respectively. When the number of steps, NStep, goes to 0 or any key is
X pressed, the looping stops and you enter a command mode.
X
X Command mode allows you to modify most of the fields. The idea is that
X you move to each field on the screen you wish to change and change it.
X When you have changed everything you want to, type "q" to resume screen
X updates.
X
X To change a field:
X
X 1) move the cursor to the field (see below);
X 2) type RETURN;
X 3) type in the new value along the command line at the top according
X to the format indicated in the prompt. To accept the new value
X type RETURN, or to leave it unchanged after all type "q".
X
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X A few fields don't require you to type anything; just typing RETURN does
X all the work. If you can't move to it, you can't change it.
X
X The arrow keys on most systems move the cursor around. If these do not
X function or function incorrectly, the h/j/k/l keys also move the cursor
X left/down/up/right, respectively. Motions off any edge of the screen will
X wrap around. You may also move the cursor immediately to a planet row by
X typing one of the characters SMevmjsunpx. (To avoid conflict with j,
X jupiter's row must actually be typed as control-j.) "x" is for the user-
X defined object X on the bottom row. Also, the characters d, o and z move
X you to the UT Date, Epoch and StpSz fields immediately, if appropriate.
X
X When you have changed a field that would invalidate any of the other
X fields the message NEW CIRCUMSTANCES appears in the top center of the
X screen. This will remain until you type "q" to allow at least one screen
X update loop to occur. If you change any field that causes new
X circumstances, the StpSz value is not added to the first loop. Note also
X that after a series of loops, NStep is automatically reset to 1 so "q"
X will do exactly one loop and return you to command mode.
X
X To quit the program, type control-d from command mode. For a little more
X help, type ?. The entire screen may be erased and redrawn with control-l.
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X 3. Screen Fields
X
X The screen is divided into two halves, top and bottom. The top fields are
X always present. They define the general observing circumstances and
X control features.
X
X The planets and one additional object are displayed in a table in the
X bottom portion of the screen. There is one object per row, and several
X columns. There are three forms of this portion selected by picking the
X Menu selection.
X
X Some things may be turned off to reduce compute times. Calculations for
X each planet may be turned on and off by selecting the planet name field.
X Calculations for Dawn/Dusk/NiteLn may be turned off by selecting any of
X these fields. Planet positions are only updated as often as necessary to
X match the display precision of the screen unless plotting or searching is
X on. In these cases full precision is desired at all times and so
X positions are always fully recalculated at each iteration.
X
X Follows is a list and description of each of the fields in each section.
X Following each name a parenthetical "p" indicates the field may be
X selected for plotting (see later). All fields may be selected for
X changing.
X
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X 3.1. Top Screen Fields
X
X LTZ the local timezone name. The name field may be changed to
X any three-character mnemonic.
X LT(p)
X LD(p) The local time and date are not labeled as such but are to
X the right of the local timezone name. They are individually
X selectable. Time and date fields may be changed as
X described in a later section. Set to "n" to set to "now"
X from computer clock.
X UT(p)
X UD(p) The universally coordinated time and date are not labeled as
X such but are to the right of the UTC label. They are
X individually selectable. Time and date fields may be
X changed as described in a later section. Set to "n" to set
X to "now" from computer clock.
X JulianDat(p) the current Julian date, to about 1-second accuracy.
X Watch selects the sky or solar system displays; see complete
X discussion below.
X Search controls the automatic search feature of ephem. See the
X complete discussion below.
X Plot controls plotting; see complete discussion below.
X Menu controls which menu is in the bottom half of the screen.
X See their complete discussion below.
X LST(p) the current local sidereal time. set to "n" to set from
X computer clock.
X Dawn(p) local time when the sun is approximately 18 degrees below
X the horizon before sunrise.
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X Dusk(p) local time when the sun is approximately 18 degrees below
X the horizon after sunset.
X NiteLn(p) length of astronomical night, ie, Dawn - Dusk. If this line
X is shown as "-----", it means the sun is either always below
X or always above approximately -18 degrees altitude on this
X particular day. This and the Dawn and Dusk lines are blank
X when their computation has been turned off.
X NStep The number of times the display with be updated (time
X advanced by StpSz each step) before entering command mode.
X StpSz the amount of time UTC (and its derivatives) is incremented
X each loop. set this to "r" to use real-time based on the
X computer clock. you may also set it in terms of days by
X appending a "d" after the number when you set it.
X Lat(p) location latitude, positive degrees north of equator.
X Long(p) location longitude, positive degrees west of Greenwich
X meridian. set to "N" to set from computer clock.
X Elev(p) local elevation of the ground above sea level, in feet. (see
X implementation notes).
X Temp(p) local surface air temperature, in degrees F.
X AtmPr(p) local surface air pressure, in inches of mercury.
X TZ(p) hours local time is behind utc, ie, positive west or
X negative east of Greenwich.
X Epoch the epoch, to the nearest 0.1 years, to which the ra/dec
X fields are precessed. This says (OfDate) when coordinates
X are not precessed, ie, are in the epoch of date. Set to "e"
X to set to epoch of date. The coordinates for the extra
X object are assumed to be in the epoch given by this field
X when they are entered.
X Also in the upper right of the screen is a calendar for the current local
X month. Dates of new and full moons are marked NM and FM, respectively.
X
X 3.2. Data format columns
X Ob name of object. Select this to toggle the display and
X calculations on and off.
X R.A.(p) apparent geocentric right ascension of object, precessed to
X given epoch, in hours, minutes and decimal minutes.
X Dec(p) apparent geocentric declination of object, precessed to
X given epoch, in degrees and minutes.
X Az(p) degrees eastward of true north for object.
X Alt(p) degrees up from a horizontal plane Elev feet above sea
X level.
X Helio Long(p) true heliocentric longitude, in degrees. Earth's is
X displayed on the sun's line.
X Helio Lat(p) true heliocentric latitude, in degrees.
X Ea Dst(p) true distance from earth center to object center, in AU,
X except distance to the moon is in miles.
X Sn Dst(p) true distance from sun center to object center, in AU.
X Elong(p) spherical angular separation between sun and given object,
X calculated from the their geocentric ecliptic coordinates.
X Note this is not just difference in ecliptic longitude. The
X sign, however, is simply sign(obj's longitude - sun's
X longitude), ie, degrees east. thus, a positive elongation
X means the object rises after the sun.
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X Size(p) angular size of object, in arc seconds.
X VMag(p) visual magnitude of object.
X Phs(p) percent of visible surface in sunlight. Note the moon phase
X is calculated simplistically as just abs(elongation)/180*100
X which can be a few degrees off... this means that because of
X how elongation is defined it doesn't say 0 during new moon
X (or 100 during full) except during close eclipses (maybe
X that's a "feature"?).
X Also, some terminals scroll when a character is written to the lower right
X character position. To avoid this, Object X's phase is left shifted by one
X column. This can look particularly ugly when the phase is 100% because the
X "100" is right next to visual magnitude number.
X
X 3.3. RiseSet format columns
X Rise The local time and azimuth when the upper limb of the object
X rises.
X Transit The local time and altitude when the object crosses the
X meridian, ie, when its azimuth is true south or, if no
X precession, when the local sidereal time equals the object's
X right ascension.
X Set The local time and azimuth when the upper limb of the object
X sets.
X Hrs Up The number of hours the object is up on the local date.
X
X Horizon displacement may be calculated in either of two ways; see the
X horizon discussion in the Menu selection section.
X
X Various oddball conditions are accounted for, including an object that is
X up sometime during the day but that doesn't rise, transit or set as such
X on that day, an object that is circumpolar or that is never up or one that
X rises twice on the same day. These are marked as "Never rises", "Never
X transits", "Never sets", "Circumpolar", "Never up" or appended with a plus
X "+" sign, respectively.
X
X 3.4. Separation format fields
X This format is a table of angular separations between each pair of
X objects. These angles are based on the local altitude/azimuth, and so in
X general differ somewhat from the elongations reported for the sun in the
X Data menu.
X
X 4. Date and Time Formats
X Times are displayed and entered in h:m:s format. If you pick a time field
X to change it any of the h, m, and s components that are not specified are
X left unchanged from their current value. For example, 0:5:0 set hours to
X 0, minutes to 5, seconds to 0, whereas :5 sets minutes to 5 but leaves
X hours and seconds unchanged. A negative time is indicated by a minus sign
X (-) anywhere before the first digit.
X
X Dates are displayed and entered in American month:day:year format. As
X with time, components omitted when entering a new value retain the current
X value. For example, if the current date is 10/20/1988 and you type 20/20
X the new date will become 20/20/1988. Note you must type the full year
X since the program is accurate over several centuries either side of 1900.
X If you change the date, the time (ie, partial day) will not change.
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X Two other ways to set the date are supported for compatibility with some
X published comet ephemerides. You may enter the day portion as a real
X number. When you set the day this way, the time will also change to
X correspond to the fractional portion of the day.
X
X You may also enter a date as a decimal year, as in 1990.12345. This is
X also useful in interpreting plot files that include a date field, since
X date fields are stored in plot files as decimal years. If no decimal
X point is included, the number is assumed to be a year unless it is in the
X range 1-12, in which case it will be taken to mean that you are just
X changing the month of the current date. To actually specify the years 1 -
X 12, you must append a decimal point to distinguish them from months.
X
X As a matter of typing convenience, the program accepts most any character
X as the separator; you don't have to type a perfect ":" or "/".
X
X 5. Configuration File
X The ephem.cfg configuration file allows you to set the initial values of
X many of the screen fields. You can still change any field while the
X program is running too; this file just sets the initial conditions. Note
X that the order of entries in this file is important because they each take
X effect immediately. You should put them in the same order you wish them
X to be processed, just as though you were changing the fields interactively
X within ephem.
X
X You can have several different configuration files if you wish. By
X default, ephem looks for one named ephem.cfg. You can tell it to use an
X alternate file by using the -c switch as follows:
X
X ephem -c <filespec>
X
X
X If your system supports the HOME environment variable then ephem also
X looks for a configuration file there with the name
X
X The format of the file uses the form KEYWORD=VALUE, where the possible
X KEYWORDS and the types of VALUES for each are described below. Any
X KEYWORDS not in the file will take on some sort of default. The separator
X need not be an actual equals sign; any char will do because the VALUE is
X assumed to start one character after the KEYWORD, regardless.
X
X Blank lines and lines that begin with an asterisk (*), pound (#), or
X whitespace (space or tab) are ignored and may be used for comments.
X
X Note: because of the way unspecified time and date components are left
X unchanged (see section on Date and Time Formats) always specify the
X complete time and date for all entries in the configuration file. For
X example, to initialize the longitude to zero degrees, say 0:0:0, not just
X 0.
X
X 5.1. Configuration File fields
X UD initial UTC date, such as 10/20/1988, or "NOW" to use the
X computer clock.
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X UT initial UTC time, such as 12:0:0, or "NOW" to use the computer
X clock.
X TZONE hours the local time is behind utc, such as 5:0:0. you need not
X set this if you use "NOW" for UT or UD.
X TZNAME name of the local time zone, such as CDT. 3 chars max. you need
X not set this if you use "NOW" for UT or UD.
X LONG longitude, in degrees west of Greenwich, in the form d:m:s.
X LAT latitude, in degrees north of the equator, in the form d:m:s.
X HEIGHT height above sea level, in feet, such as 800
X TEMP air temperature, in degrees F, such as 50
X PRES air pressure, in inches of Mercury, such as 29
X STPSZ the time increment between screen updates, such as "1" to give
X one hour updates. this can be a specific amount or RTC to use
X the system clock as a real-time source. You may also specify a
X time in days, by appending a D (or d) after the number.
X PROPTS this selects what you want included initially in the display.
X since IBM-PC math is not very fast, you can reduce the time to
X update the screen by only printing those fields of interest. the
X VALUE is a collection of letters to turn on each item from the
X following set:
X
X T twilight (dawn-dusk)
X S circumstances for the sun
X M circumstances for the moon
X e circumstances for mercury
X v circumstances for venus
X m circumstances for mars
X j circumstances for jupiter
X s circumstances for saturn
X u circumstances for uranus
X n circumstances for neptune
X p circumstances for pluto
X x circumstances for object X
X
X For example, to just track the sun and saturn, say PROPTS=Ss
X
X If the delimiter between PROPTS and the selection is a plus (+)
X sign then the given planets are included IN ADDITION TO ones
X already specified. Any other delimiter sets the selection to
X exactly the set specified. This feature was added so that the
X command line version of using PROPTS could add to the set of
X planets giving in the configuration file.
X NSTEP number of times program will loop before entering command mode.
X see the discussion under Program Operation.
X EPOCH this sets the desired ra/dec precession epoch. you can put any
X date here or EOD to use the current instant ("Epoch of Date").
X OBJX This field specifies the optional object "x". The field
X contains several items, each separated by a comma. The first
X field is the type of the object, that is, one of the strings
X "fixed", "elliptical", or "parabolic"; only enough of the string
X to be unique is required so you may use just the first character
X if desired. The remaining fields depend on the type of object.
X They are exactly the same parameters, and in the same order, as
X ephem asks for when defining the object from the menu. These
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X are described in more detail in the section on "Object X". You
X may define one object of each type in the configuration file;
X the last one defined will be the "current" one when ephem gets
X going.
X
X 5.2. Example ephem.cfg
X
X This is the ephem.cfg file that was in effect when the sample screens (in
X another section) were generated. You might run ephem with this
X configuration file and compare with the samples as a check.
X
X * time is the evening of comet austin's maximum solar separation angle.
X UT=1:45:0
X UD=4/5/1990
X TZNAME=CST
X TZONE=6:0;0
X LONG=93:42:8
X LAT=44:50:37
X HEIGHT=800
X TEMP=40
X PRES=29.5
X STPSZ=RTC
X PROPTS=TSMevmjsunpx
X EPOCH=Eod
X NSTEP=1
X
X * comet halley. elements from Duffett-Smith book; mag from 12/86 S&T pg 666
X OBJX=e,1986.109,76.0081,170.011,0.9673,162.2384,58.1540,17.9435,3.66,7.05
X
X * orion, roughly
X OBJX=fixed,6:0:0,0:0:0,1950
X
X * comet austin, 1989c1, as per IAU Circular 4941, and magnitude rumors.
X OBJX=parabolic,4/9.847/1990,58.911,61.504,.34963,75.409,1950,3.8,13.7
X
X As another common example, this ephem.cfg creates an essentially free-
X running real-time screen based on the computer clock:
X
X UT=Now
X LONG=90:10:8
X LAT=40:50:20
X HEIGHT=800
X TEMP=50
X PRES=29
X STPSZ=RTC
X PROPTS=TSMevmjsunp
X NSTEP=9999999
X EPOCH=Eod
X
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X 6. Menu options
X
X When you select "Menu" you can change among the three styles of bottom
X screens. There are also two options that can be set from the Menu quick-
X
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X choice menu. These options toggle when picked and retain their values so
X they need only be changed when desired.
X
X 6.1. Adaptive vs. Standard hzn
X
X This selects the horizon refraction displacement algorithm used by the
X Rise/Set menu. "Adaptive" uses the local atmospheric conditions known to
X ephem and matches the Planet Info times nicely. "Standard" uses the
X "accepted nominal" horizon refraction value of 32 arc minutes and usually
X agrees, to a minute or so, with published tables.
X
X 6.2. Geocentric vs. Topocentric
X
X This selects the vantage point for the Separation menu. "Geocentric"
X ignores local conditions and gives the separation as seen from Earth
X center. "Topocentric" uses the local conditions known to ephem. They are
X particularly critical for lunar occultations, but the effect can be
X significant for the planets.
X
X Note that searching over a period that will include the rise or set times
X of either object is generally better performed from the geocentric
X viewpoint. The refraction effect of the topocentric viewpoint causes many
X arcminutes of rapid whiplash displacement as the objects rise and set that
X overlays the smooth celestial motion of the objects. This rapid position
X variation can confuse the solver algorithms that expect fairly smooth
X functions.
X
X 7. Object X
X
X You may specify an extra object for ephem to use. This object may be
X defined in three ways: fixed celestial sphere coordinates, or
X heliocentric elliptical or parabolic orbital elements. Elliptical
X elements are typically useful for periodic comets or asteroids, and
X parabolic elements are for nonrecurring solar system interlopers such as
X aperiodic comets.
X
X A simple magnitude model is used to estimate the brightness of comets.
X This model requires two parameters to be specified. One, the absolute
X magnitude, is the visual magnitude of the comet if it were one AU from
X both the sun and the earth. The other, the luminosity index,
X characterizes the brightness change of the comet as a function of its
X distance from the sun. The model may be expressed as:
X
X m = A + 5*log10(Re) + S*log10(Rs)
X where:
X m is the resulting visual magnitude;
X A is the absolute visual magnitude;
X Re is the comet-earth distance, in AU;
X S is the luminosity index; and
X Rs is the comet-sun distance.
X
X Note that this model does not take into account the phase angle of
X sunlight on the comet.
X
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X
X The parameters for each type of object are stored separately, so you may
X switch between types of objects without losing parameters.
X
X 7.1. Controlling Object-X Operation
X
X To control the type and the corresponding details for object X, select the
X left column of the bottom row, that is, the X. (Remember that typing the
X character "x" is a shorthand way to move to the bottom row.) It will bring
X up a quick-choice menu as follows:
X
X Select: Fixed coordinates, Elliptical elements, Parabolic elements, On
X
X
X When you first enter the quick-choice menu the cursor will start out
X positioned at the field for the current type of object. The first three
X selections allow you to enter or review the various parameters required to
X define an object's position of such type, one parameter at a time. You
X set the current object type and begin to view its parameters by
X positioning the cursor over the type and pressing RETURN. The prompt for
X each item includes a short description, the units to use, and its current
X setting is shown in parentheses. To leave the item unchanged and go to the
X next item, type RETURN. If you do not wish to change or see any more
X items about the object then type "q" and you will return immediately to
X the object-X quick-choice menu.
X
X You exit the quick-choice menu by typing "q" while over any field or
X RETURN while over On or Off, as described in a later section.
X
X As with all dates throughout ephem, the dates for the epochs of perihelion
X and reference epochs may be entered in month/day/year or decimal year
X formats, and the day may be entered as a real number (see the section on
X Date and Time Formats). All dates given for comet parameters are always
X in UT.
X
X 7.1.1. Fixed coordinates
X
X This selection will present a series of three prompts, one each for the
X RA, Dec, and the reference epoch for the coordinates of a fixed object.
X
X 7.1.2. Elliptical elements
X
X This will begin a series of nine prompts asking for the parameters that
X define a heliocentric elliptic orbit and the magnitude model coefficients.
X These orbital parameters are, in order, the epoch of perihelion, orbital
X period, longitude of perihelion, eccentricity, inclination, longitude of
X the ascending node, and the semi-major axis of the ellipse. Then follows
X the absolute magnitude and luminosity index coefficients.
X
X 7.1.3. Parabolic elements
X
X This will begin a series of eight prompts asking for the parameters that
X define a heliocentric elliptic orbit and the magnitude model coefficients.
X These orbital parameters are, in order, the epoch of perihelion,
X inclination, argument of perihelion (same as the longitude of perihelion
X
X
X
X
X
X
X
X
X
X - 13 -
X
X
X minus the longitude of the ascending node), perihelion distance, longitude
X of the ascending node, and the reference epoch of the parameters. Then
EOFxEOF
len=`wc -c < Man.txt.1`
if expr $len != 33834 > /dev/null
then echo Length of Man.txt.1 is $len but it should be 33834.
fi
# if Man.txt.2 exists, then the second half of the manual has already been
# created from its shar file so we stick it after this one to make Man.txt.
if test -w Man.txt.2
then
echo catting Man.txt.2 to Man.txt.1 to form Man.txt
cat Man.txt.2 >> Man.txt.1
rm Man.txt.2
mv Man.txt.1 Man.txt
fi