The X-Philes (2nd Revision)/The X-Philes Number 1 (1995).iso/xphiles/hp48hor2/tyko.doc

Text File | 1995-03-31 | 14KB | 305 lines

        V_E_R_S_I_O_N   Y      Y    K    K     OO
              T          Y    Y     K   K    O    O
              T           Y  Y      K  K    O      O
              T            YY       KK      O      O
              T            Y        K  K     O    O
              T           Y         K    K     OO   2.1
       =================================================
         EXPANDABLE STAR SUN-SYSTEM PROGRAM FOR HP48SX

                        K. M. Sinenmaa



                         INTRODUCTION

A  EXTERNAL:

The program gives information about some objects of our Solar System (the Sun,
Moon, and all known planets except the Earth), and some of the brightest stars
of some well-known constellations.

B  INTERNAL:

The program's data for the solar system's objects are based mostly on the
article of T. C. Van Flandern and K. F. Pulkkinen, "LOW-PRECICION FORMULAE FOR
PLANETARY POSITIONS", published in 1979 November, The Astrophysical Journal
Supplement Series 41: 391-411.  The other parts are more general astronomical
data and formulae, found in standard astronomical literature.


                       PROGRAM'S RUNNING

C  STARTING:

Transferring the program to a calculator, all the files are in one directory.
By pressing that VAR-menu key you should get 24 new files.  Only one of those
files is able to excecute the whole program.  This is the MAIN-file.

Pressing this menu key brings up to the LCD screen a three-by-three matrix. The
first row contains the view date (any date between A.D.  1000 and 9999 is
allowed, but dates far from the present tend to lose accuracy.  See section "G:
PRECISION", below).  The first column of the second row is the viewer's
longitude, the next is latitude and in the third is the location of time zone.
The third row contains the local time and two empty elements.

There is a temporary menu area where are six new menu keys.  The ESC key allows
to you to continue the excecution of MAIN-prog. The other five keys have been
reserved for the altering of the values of the matrix.

These five variables can be changed as many times as you want.  Just press the
desired menu key, then put a value to the stack and press the ENTER-key.

     REMARKS: It is necessary to put all the digits into the decimal parts,
              also the preceding zeros if the minutes or the month's numbers
              are smaller than 10 !

              Time should be entered in the 24-hour system.

              Time Zone (menu key ZONE) is negative at the West Longitudes. For
              examples; Los Angeles is -8 , New Zealand is 12 and Moscow is 2.

               * If you want to do the comparisons e.g. with The Astronomical
                 Almanac you must set up the TIME to be equal with the ZONE.
                 For intance, if the ZONE is -9 then the TIME must be -9 too,
                 because the time has to be at 0 UT.

              Because of the prog's internal structure the date must be between
              1.011000 and 31.129999.

D  TWO BRANCHES:

When the matrix's contents satisfy you, press ESC to go to the next step. Again
you'll get two new temporary menu keys.

1.  SUN.S means that if you press it the HP48 calculates the values for the Sun
System's objects.  The first part of this takes about 12 seconds.  After then
you can hear a weak sound - if you are sitting in some quiet place.

Whatever you hear this sound, that's the sign that there is the last temporary
menu to select in this alternative.  It is a two-page menu containing all
computable objects in our Sun System.  By selecting one of those objects you'll
put the program into its final phase, counting the elements of that object.
This takes about 22 seconds, leaving you with quite a handful.

2.  STARS-key is a little bit faster.  Only about six seconds after pressing
the STARS-key, you'll get the STARS-key with ESC-key.  At this point you can
browse the names of existing stars.  The method is the same kind as in the
beginning.  At this time you can put the numbers from one upwards.  Again, it
doesn't matter how many times this is done.  The default star is Aldebaran.

When the star's name looks good, press ESC to excecute the ending part of this
selection (÷14 sec.).

                           RESULTS

The first thing in this stage --- watch the LCD screen and turn on some bright
lights --- the results are as a GROB picture.  The GROB pict is constructed
because showing the results is much easier than any other way.  One PICT can
show a lot of information [about 1K words?  -jkh-].  Thirdly, it is possible to
transfer the GROB pict to a PC and convert it to a TIFF-pict.

E   APPEARANCE:

+---------------------------------------+
|                                       |    Remark:
|   48SX         scientific expandable  |
|  ===================================  |    some Greek letters
| |Jupiter         JDAY= 2448600.50   | |    are different from
| |\= 153.243212   GST 0UT= 5.125327  | |    in this diagram
| |á= 1.023031     LST= 6.524223      | |
| |R= 5.383017     AZ= 290.504037     | |    \ = lowercase lambda
| |/\= 5.232645    A = 19.475827      | |    á = lowercase beta
| |ë= 7.183812    D= 37.63   M= -2.14 | |   /\ = uppercase delta
| |à= 11.022729    LT = 23.103339     | |    ë = lowercase delta
| |ç= 19.051999    LT = 13.085673     | |    à = lowercase alfa
| |[[ 10 12 1991 ] [ 24.954 60.162 2  | |    ç = lowercase tau                                                               |
|  ===================================  |
+---------------------------------------+


F   SPECIFICATIONS:

1.  Lambda and beta ( \ , á ) are the object's ecliptic coordinates.  In the
case of planets, the Sun is the origin; in other words, they are the planet's
heliocentric longitude and latitude.

To the Sun and Moon, they are the geocentric coordinates.

To the stars, the helio- and geocentric coordinates are identical. The
fundamental point of the longitude is the same together with the right
ascension (3.).  The zero point to the latitude is the Earth's orbit plane,
called the ecliptic.  Both of these are in the arc degree-form; DD.MMSS.

 REMARK:  The Sun's ecliptic latitude is always zero according to this program.
 This is not *exactly* true.  The planets' gravities do warp the Sun... but
 this force is so weak compared with the Sun's mass that the Sun's latitude is
 smaller than plus/minus 1 arc second.

2.  Distances R and /\ (delta).  R is the object's heliocentric distance.  This
is given for all objects.  Delta is object's geocentric distance.  In the case
of the Sun and Moon; R = /\.  This is true also to the stars although you can
see /\= '/\' only.

 REMARK:  To the Moon the distance is x times the equatorial radius of the
 Earth; to the Sun and planets the distances are x times 1 AU ( 1 AU =
 149597870 km = 92955806.8 miles ); to the stars the distance is x times 1pc (
 1pc = 206265 AU = 3.26 ly ).

3.  ë (lowercase delta) and à (lowercase alpha) are the object's declination
and right ascencion which are the equatorial coordinate system's coordinates.
The declination is the object's angle distance from the equator; it varies -90
to 90 degrees.

The right ascencion is measured from the first point of Aries counterclockwise.
That point is the point where the Sun seems to move from the southern side of
equator to the northern side.  The common name is the vernal equinox.  Notice
that the right ascencion is given in hours, minutes and seconds, contrary to
the declination which is in the format of arc DD.MMSS.

4.  ç (lowercase tau) is the object's perihelion time.  This is a point on the
planet's orbit when it is the nearest the Sun.  The perihelion time is given
only to the planets and Moon.  This time-point is either in the past or in the
future.

5.  JDAY (Julian Day) is the number of the continuing days from the mean noon
of January 1st 4713 B.C. at the longitude of Greenwich.  JDAY is given in
Universal Time.

6.  GST 0UT is the Greenwich mean Sidereal Time at 0h UT (Universal Time).
"Mean" means that no time corrections have been added to this values.

7.  LST is the Local mean Sidereal Time.  You can get the GmST by subsracting
your defined longitude from the LST divided by 15.  Remember, west longitude =
negative!

8.  AZ and A are the horizon coordinates, azimuth and altitude.  This prog
measures the azimuth clockwise from the South when an observer is on the
northern hemisphere (and from the North otherwise).  AZ_180φ = North in both
hemispheres.  The azimuth gets values 0 to 360 degrees.

The altitude is the object's angle distance from the horizon upwards.  This
coordinate is between 0 and 90 degrees.

  REMARK: By these coordinates you can easily find the object.

  The azimuth and altitude show the "true" place of the object.  (The
  refraction, aberration, and other things that have an effect on the
  coordinates have not been taken into account).  However, in the high
  altitudes the error is negligible.  Near the horizon the difference is about
  35' compared with the apparent altitude.

9.  D = the object's equatorial angle diameter, given in arc seconds.  Not
given for stars.

10. M is the object's apparent visual magnitude.

11.  LTup and LTdown are the rising and setting times of the object.  LT is the
LOCAL TIME at the observer's longitude.

The expected error for sunrise and sunset is within 5 minutes (plus/minus
2.5min), sometimes exceeding this.  To the planets this error is larger.  To
the Moon this error is considerably larger.

12.  [[ 10 12 1991 ] [ 24.954 60.162 2 ]]; This matrix contains the date,
longitude, latitude, time zone and time.

       **** Press ON to exit **** Takes a few seconds ****


G  PRECISION:

The comparison values for Jupiter on 1991 December 10 have been taken from The
Astronomical Almanac 1991:

+------------------------------------------------------------------+
|   Lambda ( \ ) = 153.24428        Julian day = 2448600.5         |
|   Beta ( á ) = 1.02325            Greenwich mean sidereal time   |
|   R= 5.383684                     at 0 UT = 5.12532682           |
|   /\= 5.2333689                   Equatorial D = 37.62           |
|   Declination = 7.183108          Magnitude M = -2.1             |
|   R.A. = 11.0228382                                              |
|   ( Perihelion time = 21.051999 ?)                               |
+------------------------------------------------------------------+

The expected errors for the coordinates, of the Sun system's objects, are
plus/minus 1 arc minute, usually less, except for Pluto for which you can
expect several minutes error, but it should stay inside plus/minus 15 arc
minutes.  For the stars the expected errors can be a few seconds.

The accuracy of the distances to the planets, Moon and Sun are usually to three
decimal places.  The distances for the stars were taken from the star
catalogues.

The equatorial diameter, when it is given, seems to be almost the same as in
the astronomical data books.

The magnitude is within .5m to the outer planets. For the inner planets this
seems to vary a little more.

The perihelion times for the nearby planets seem to be relatively accurate, but
are unreliable for the giant planets and Pluto.

The date can be plus/minus 200 years from the present in order tp produce
reasonable results.  For the Sun and Moon this time interval is much smaller.
The closer to the present you are, the better results you will get!!

                       o  EXPANSIVITY  o

This is for the stars only.

By this time you have seen there are 24 files which this program uses.  Two of
them are for the stars, under the names of NM and DATA.  NM contains all the
stars' names, and DATA has the stars' data.  If you have plenty of free memory
in your HP48, then you can add data to these files.

To do this you have to have some astronomical book at hand.  For this program
were used two books:

    Catalogue of Bright Stars  ( Hoffleit )
    Sky catalogue 2000.0  ( Cambridge )

Pick up the equatorial coordinates R.A.  and declination for the desired star.
Make the reduction to epoch 2000 (this is not needed if you already have a data
book to the new standard epoch, J2000.0).  Do conversion equatorial(2000.0) to
ecliptic(2000.0).  Also pick up the visual magnitude and distance.

Recall DATA to the stack and add the list containing the ecliptic longitude,
-latitude, distance and magnitude, respectively.  Add the star's name to the
NM-file.  Change the 11 to 12 (etc.) in program line " IF n 11 > " found in
NEWS-var.

ESSENTIALS

The prog can halt for example if you press an incorrect button by mistake.  If
you do, there will be a huge number of variables in VAR-dir.  To clean them up,
find the MAIN-file and restart the program.  This is necessary because this
prog changes your flag-configurations and if you want to save them, do it.

You can also purge all those variables and check the amount of free memory
space before next running.

If you have problems due to insufficient memory, you can destroy a few stars or
one planet, depending on your mood.  [Shades of Darth Vader!  -jkh-]  This
should improve your situation.  Planets' files are all the CALx-variables.

This program doesn't take into consideration any artificial time changes like
Daylight Saving Time; you must handle that yourself.

REFERENCES

The Astrophysical Journal Supplement Series,
41:391-411, 1979 November

Fundamental Astronomy,
Karttunen, Kr ger, Oja, Poutanen, Donner

The Astronomical Almanac  19XX

Practical Astronomy with your Calculator,
Peter Duffet-Smith  3rd. edition

[Note: Transmogrified into (American) English by -jkh-]