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Atari Mega Archive 1
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Atari Mega Archive - Volume 1.iso
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astrocal.arc
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ASTROCAL.TXT
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1985-11-20
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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