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Information about “DEEP SPACE SUPPLEMENT 2 OF 2 (866)”
DEEP SPACE 3-D is a powerful star mapping program that uses a database
of over 19,000 stars (expandable to nearly 250,000 stars and 1100
comets), used by a number of serious astronomy publications to create
their star charts.
It can produce all-sky views or horizon views for any day and time
anywhere on earth. Selected portions of the sky can be chosen by
constellation or coordinates, then zoomed in for more detailed views.
Comet paths can be computed and added to the star maps to create finder
charts or to visualize the orbits of comets from any point in space. A
new "What's Up" feature tells at a glance the times of sunrise, sunset,
twilight, moon phases, and positions of the sun, moon, planets and
current comets for a given day and time. Once computed, the information
is stored and may be added to the star maps.
The most unique feature of DEEP SPACE 3-D is depth. It can produce
stereo 3-D printouts that show the stars or the orbits of comets in
their true three dimensional relationships when viewed with a stereo
viewer. A 3-D viewer is included in the registration price.
Although DEEP SPACE 3-D has many features that will be attractive to
experts, it is simple enough to be used easily by beginners. An
extensive help menu teaches the beginner as much about astronomy as it
tells about the program. An improved user interface provides
intelligent default values in case the feature is beyond the interest or
knowledge of the user. It supports CGA, EGA, VGA and Hercules monitors.
This program is an ideal starting point for anyone who is looking for a
reliable guide to observational astronomy. For centuries man has gazed
at the night-time sky and wondered what was out there. DEEP SPACE will
help answer some of those questions.
FILE0867.TXT
Disk No: 867
Disk Title: Deep Space Supplement 2 of 2 (866) (Disk 2 of 2)
PC-SIG Version: S2.1
Program Title: Deep Space 3-D
Author Version: 2.1
Author Registration: $59.00
Special Requirements: 512K RAM, graphics card, two floppy drives, & Epso
DEEP SPACE 3-D is a powerful star mapping program that uses a database
of over 19,000 stars (expandable to nearly 250,000 stars and 1100
comets), used by a number of serious astronomy publications to create
their star charts.
It can produce all-sky views or horizon views for any day and time
anywhere on earth. Selected portions of the sky can be chosen by
constellation or coordinates, then zoomed in for more detailed views.
Comet paths can be computed and added to the star maps to create finder
charts or to visualize the orbits of comets from any point in space. A
new "What's Up" feature tells at a glance the times of sunrise, sunset,
twilight, moon phases, and positions of the sun, moon, planets and
current comets for a given day and time. Once computed, the information
is stored and may be added to the star maps.
The most unique feature of DEEP SPACE 3-D is depth. It can produce
stereo 3-D printouts that show the stars or the orbits of comets in
their true three dimensional relationships when viewed with a stereo
viewer. A 3-D viewer is included in the registration price.
Although DEEP SPACE 3-D has many features that will be attractive to
experts, it is simple enough to be used easily by beginners. An
extensive help menu teaches the beginner as much about astronomy as it
tells about the program. An improved user interface provides
intelligent default values in case the feature is beyond the interest or
knowledge of the user. It supports CGA, EGA, VGA and Hercules monitors.
This program is an ideal starting point for anyone who is looking for a
reliable guide to observational astronomy. For centuries man has gazed
at the night-time sky and wondered what was out there. DEEP SPACE will
help answer some of those questions.
PC-SIG
1030D East Duane Avenue
Sunnyvale Ca. 94086
(408) 730-9291
(c) Copyright 1989 PC-SIG, Inc.
GO.TXT
╔═════════════════════════════════════════════════════════════════════════╗
║ <<<< Disk #867 DEEP SPACE (disk 2 of 2, also #866) >>>> ║
╠═════════════════════════════════════════════════════════════════════════╣
║ To install program, insert disk 1, type: README.DOC (press Enter) ║
║ ║
║ To start program, insert disk 1, type: DS3D (press Enter) ║
║ ║
║ To print documentation (on this disk), type: COPY TEXT.TXT PRN (Enter) ║
╚═════════════════════════════════════════════════════════════════════════╝
(c) Copyright 1990, PC-SIG Inc.
TEXT.TXT
lL-llT--------T-----------------------T---------------T-------T-------T-----TrRr
>CATALOG & ORDER FORM
DAVID CHANDLER CO.-- SOFTWARE, SLIDES, AND PUBLICATIONS
(All items authored and published by David Chandler except as noted)
(Prices subject to change)
DEEP SPACE 3-D, Ver 2.1 -- 3-Disk Set with 3-D Viewer
Single User Registration $ 59 _____ ______
Site Registration (Per building) $ 120 _____ ______
(REGISTERED USER NAME_____________________________________________________)
(Type or print user name exactly as you want it on the title page)
LARGE TABLE-TOP 3-D VIEWER KIT $ 35 _____ ______
(For viewing pairs of 8-1/2 x 11 printouts in stereo)
COMET WATCH--A newsletter giving finder charts and orbital elements that can
be used with DEEP SPACE 3-D. 15 issues per volume, "Vol 0" gives extra
background information and lots of data to get started. (All subscriptions
begin and end at volume boundaries to simplify bookkeeping.)
Vol 0 $ 10 ea _____ ______
_____ Volumes starting with the current Volume $ 10 ea _____ ______
3-D viewer, when ordered with Comet Watch $ 3 ea _____ ______
- (Overseas Subscriptions: $ 15 / Viewer: $ 4) _____ ______
------------------------------------------------------------------------------
| (** REGISTERED USERS ONLY **) |
| ADDITIONAL STAR DATABASE FILES: 14 disks for a total of 248,709 Stars |
| Circle Disk #'s: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
| (1 or more, $10 ea / 5 or more, $8 ea / 10 or more, $7 ea) AMOUNT: ______ |
| |
| ORBITAL ELEMENTS FOR OVER 1100 COMETS dating back to 240 BC, based |
| on Brian Marsden's "Catalog of Cometary Orbits" (and more) $ 15 ______ |
------------------------------------------------------------------------------
DEEP SPACE 3-D, Ver 2.1 (Unregistered Trial Copy--2 Disks)
(With $15 coupon toward registration price) $ 15 _____ ______
3-D VIEWER (ordered separately) $ 5 _____ ______
-
OTHER IBM SOFTWARE
PLANETS IN THE CLASSROOM, IBM Version (Not Shareware) -- A program for
understanding planetary motion, specifically designed for teachers, but of
interest to amateur astronomers as well. Comes with a manual of classroom
exercises appropriate for various levels from elementary through college.
$ 39 _____ ______
ALGOL, IAU TELEGRAMS, and CELL -- Three special purpose programs. ALGOL
computes the dates and times of the minima of the eclipsing binary star
Algol in local time. TELEGRAMS takes input from a menu and encodes
telegrams in the proper format to report discoveries of comets, novas,
supernovas, etc. to the Center for Astronomical Telegrams. CELL
rigorously calculates the parameters for designing 9-point and 18-point
telescope mirror cells.
$ 10 _____ ______
|
APPLE II SOFTWARE
PLANETS IN THE CLASSROOM, Apple II Version (Not Shareware) -- Identical in
printed output with the IBM Version, except it runs much slower.
Comes with the same manual of classroom exercises. (Apple version
implemented by Michael Lovekin.)
$ 39 _____ ______
ASTRONOMY ASSORTMENT -- This is a collection of public domain programs related
to astronomy for the Apple II. They graphically display the positions of
Saturn's Moons, compute phases and eclipses, compute various calendar and
Julian day functions, compute scales for laying out model solar systems,
apply Kepler's laws to various orbital systems, and simulate radioactive
decay. (Authored by various people, some unknown)
$ 10 _____ ______
-
BOOKS AND CHARTS
THE NIGHT SKY / A specially designed low distortion rotating star chart for
anyone who really wants to get to know the sky. This practical, take-
it-out-and-use-it star finder is the real backbone of our product line.
Over 1/4 million copies are in circulation. Astronomy educators are its
most vocal fans:
"The Night Sky is not just another planisphere. I think The Night Sky
is the finest and easiest to use star finding aid in existence."
-- Jack Horkheimer, T.V.'s "Star Hustler" and Planetarium
Director at the Miami Museum of Science.
$ 5.95 _____ ______
Latitude or nearest large city ______________
- (Teachers: Ask for "Sample Classroom Exercises using The Night Sky")
\
EXPLORING THE NIGHT SKY WITH BINOCULARS -- (Illustrated by Don Davis)
A written companion to THE NIGHT SKY that leads the beginner from naked
eye astronomy to the ideal "first telescope": a pair of binoculars. It
covers both what to see and the significance of what is seen. This book
was written with adults in mind, but it received honorable mention in the
Older Children's Division of the New York Academy of Sciences Children's
Science Book Awards.
"Yes, you can quote me because it is true. It's the best short
introduction to astronomy ever written."
--Doug McCarty, Planetarium Director, Mt. Hood Community College.
"From the creator of what I consider to be the best planisphere
available (The Night Sky), comes Exploring the Night Sky with Binoculars,
a companion to that star dial. Taken together, the two items--plus a pair
of binoculars--constitute the best introduction to observational astronomy
you could ask for."
--John Mood, Astronomy Magazine. $ 5.95 _____ ______
(Star Dial and Book ordered together) $ 10 _____ ______
|
SLIDES
DON DAVIS ARTWORK -- Slides of the paintings of one of the world's greatest
space artists. These slides are like photographs from points in time and
space inaccessible to the camera. They come fully annotated to interpret the
wealth of subtle, accurate detail found in each painting. (For more
background on Don Davis, see the June 1985 issue of Sky and Telescope.)
The Moon and its Formation (21 slides) -- A classic time lapse sequence
showing the formation of the moon from its early accretion to the present
day. $ 21 _____ ______
The Earth (16 slides) -- The earth through time, continental drift, impacts
from space, theories of dinosaur extinction. $ 16 _____ ______
Eclipses (12 slides) -- Lunar and solar eclipse phenomena as seen from the
- earth, space, and the surface of the moon. $ 12 _____ ______
The Terrestrial Planets (18 slides) -- Mercury, Venus, and Mars, with
emphasis on Mars and the Viking missions. $ 18 _____ ______
The Outer Solar System (36 slides) -- The gas giants, their moons, their
rings, the solar system as seen from Pluto and the Pioneer X spacecraft as
it leaves the solar system. $ 36 _____ ______
Beyond the Solar System (10 slides) -- The Orion Nebula, the Milky Way, a
time sequence of Hercules X-1, and the gravitational lens effect of a
black hole. $ 10 _____ ______
All six sets ordered simultaneously (113 slides) $ 107.35 _____ ______
(For reproduction rights or arrangements for commercial use of slides, write
- to Don Davis, c/o Hansen Planetarium, Salt Lake City, UT.)
\ ---------------------------------------------------------------------------
6.75% Sales Tax (in CA only) ______
$3 Domestic Shipping Charge on All Slide Orders ______
** Overseas ** Large 3-D Viewer: (Air) $ 35, (Surface) $ 13 ______
** Overseas ** All other items, add: (Air) $ 5, (Surface) $ 2 ______
TOTAL: ______
(Checks must be payable in US Dollars drawn on a US bank)
(Domestic shipping will be added to invoices if not paid in advance)
Name________________________________________________________________________
Address_____________________________________________________________________
City__________________________________________________State______Zip________
+
>PROGRAM REGISTRATION
Beginning with Version 2.1 registered users may imprint their REGISTERED USER
NAME on the title page of the program. When a copy of the program is
imprinted in this way additional file capacity is unlocked. Unregistered
users have access to the initial star file, SST01, and two comet files:
CURRENT.CFL and RECENT.CFL. Registered users have access to all star files,
expandable to SST77, and any number of comet .CFL files. All functions of the
program work in both registered and unregistered form.
When registering your program, state your REGISTERED USER NAME (either a
personal or institutional name) exactly as you want it imprinted on the title
page. In return you will be sent star files SST02-SST06 and a REGISTRATION
NUMBER. Select the registration option at the Main Menu and enter your name
and number. Keep your REGISTRATION NUMBER for future reference.
If you want to share the program with a friend or colleague (and we encourage
you to do so--word of mouth is our only advertizing) select the Deregistration
option at the Main Menu, or simply delete the CONFIG.DAT file on the disks you
wish to share. Please share only the complete Deep Space 3-D disk and the
DS Supplement disk. (See CATALOG & ORDER FORM)
+
>A SAGA IN THREE PARTS
PART I
A new comet is discovered! It is faint now, but it is expected to
brighten almost to naked-eye visibility (about 6th magnitude) in a few weeks.
The newspapers won't carry stories about this one, but you know about it
within a week of its discovery because you subscribe to COMET WATCH.
You have had bad luck with comets in the past. You tried to find
Halley's Comet but couldn't find it in your brand new marketed-for-the-
occasion telescope. The bottom line is you couldn't find your way around the
sky and didn't know exactly where to point the thing...but this time things
will be different! You have all the right tools: a sturdy star dial that you
are using nightly to learn the constellations one by one, a nice little book
that made you realize the value of those binoculars you had hidden up in a
closet while you were struggling with your new telescope, and DEEP SPACE 3-D,
the most versatile comet crunching computer program available.
Back to our story. COMET WATCH arrives in the mail. You type in the six
magic numbers that specify the comet's orbit. Within minutes you have on the
screen an ephemeris for the next two months. "Ephemeris"...you just learned
the word, but it has a nice ring to it. It means lots of numbers! You go on.
Within minutes you have printed out a large-scale finder chart in "Star Atlas
Mode" which you can use to spot the faint smudge with your binoculars, and in
-turn guide your telescope to its target...
But that's not all. You run What's Up for the current date and look at
the rise and set times for the comet. You see that the comet rises at 4am, so
you run What's Up again, this time for an early morning hour. You do another
ephemeris, this one correlated with the current What's Up settings. You plot
an all sky map and see two paths for the comet: one showing its path relative
to the constellations, just what you had before, and the other one showing its
path relative to the horizons. These paths gradually separate, since the star
positions are for one particular night, but the comet is shown for several
weeks, during which time the sky will have rotated considerably. You use the
cursor to identify the dates when the comet will be highest above the horizon
and are pleased to see it will be well placed when it is at its brightest.
You run yet another ephemeris, this one not for "finding", but for
"understanding". You plot out the whole orbit on the screen and see how the
comet zips past the earth's orbit in its brief encounter with the sun before
its slow return to the outer fringes of the solar system. You put the cursor
on the screen and use the "ID" option to step along the orbit, matching the
earth's position with the comet's position day for day. You plot out the
orbit in 3-D to help visualize the orientation of the comet's orbit in space.
It is apparent that this comet's orbit is highly inclined to the plane of the
solar system. The comet will loop up and over the earth, causing it to move
far to the north in the sky then disappear below the southern horizon. Not
-only are you confident of finding this comet, you have come to know it well.
PART II
You are a teacher planning a sky observation night for your students. You
want to find a date when the moon is up for viewing in the evening sky but not
so close to full that it will drown out everything else. You want your
students to get home at a reasonable hour, but you want to stay late enough so
it will be fully dark. You would like your students to see the rings of
Saturn or the moons of Jupiter in a telescope, but you realize these planets
are not always out in the evening sky. How can you plan for a successful
session in time to announce it to parents a month or more in advance?
The What's Up option is the place you start. You enter a rough target
date and your observing site. You immediately see the dates of all the new
moons thoughout the year and all of the moon phases in your target month. You
pick a date near first quarter for a well placed evening moon. (Craters show
+up best at first quarter because they cast long shadows then.) The default
observing time is the end of evening twilight, which looks OK to you, so you
accept it. You choose the ALTER DATE option to zero in on the day best suited
for your event. You print out the information screen for your own reference.
With the date and time selected, you go on to check out the rise and set times
of the moon and planets. Returning to the main menu you run a full-sky star
map for the event, limited to 3rd magnitude stars (since you know that's all
that will be visible from town anyway). You print it out, duplicate it, you
-are ready to go.
PART III
You are an avid amateur astronomer, out on a mountain top long past most
people's bed time. You run across a faint fuzzy object in your telescope that
isn't on your star atlas. You do a careful sketch of the field stars to get a
fix on its position, estimate its magnitude, and watch it for a half hour or
so to verify that it drifts slowly past the background stars. It does! You
have a comet! Anticipating immortality (for your last name at least) you risk
life and limb rushing back down the winding mountain road...but before placing
a telegram to Cambridge, MA, you decide to check What's Up first.
You subscribe to COMET WATCH, so you have maintained a file of all the
comets that have come by in the last few years. You have copied the ones
currently visible to a smaller file for easy access. You run What's Up to get
a listing of positions, estimated magnitudes, and rise and set times. Just
for good measure you run it for the whole file so nothing will slip by. You
don't like looking at long lists of numbers, so you select all the comets for
inclusion on the star chart, return to the main menu and generate a star chart
for the current day and time. You choose the function key for "Planets etc."
and every comet in the file shows up on the screen (most of them far too faint
to be visible). You immediately notice a comet close to where you found
yours. You put the cursor on it to identify it and go back to the What's Up
-option again to take a closer look...
It becomes clear that the comet you discovered (you really discovered
it!) was also discovered several months earlier by someone named Liller. In
fact you had looked at it back then when it was much brighter and had a nice
tail, but it was in a totally different part of the sky. It had dimmed down
so much that you had removed it from your current comet file (CURRENT.CFL),
but had the good sense to keep it in your backup comet file (RECENT.CFL).
You're disappointed, but you realize that your thorough search has saved you
from the embarrassment of a false alarm and the expense of a needless
telegram. Still you realize that your comet is out there waiting for
you...but that's for another day.
.....
(That's how it might have been. The truth of the matter is I didn't have
What's Up at the time. I did have Version 1.3 of DEEP SPACE up and running,
and I did have Comet Liller on file! If I had taken the time I could have run
ephemerides for all the comets in the file and found that Comet Liller was
still bright enough to be seen and right where it should have been...but that
was too time consuming, so I just checked a few likely candidates. I sent the
telegram and later swallowed hard when I discovered my error. I decided then
and there to add a new option to the program. That's why you and I have the
handy What's Up option today. I have written this program for me. If you
+like astronomy like I like astronomy, you might find it nice for you too.)
>THE DISTRIBUTION DISKS
DEEP SPACE 3-D, Version 2.1 comes on two floppy disks (UNREGISTERED VERSION)
plus a third data disk upon registration. We encourage you to share clean
copies of the UNREGISTERED 2-disk set only. Please do not delete any files.
The DEEP SPACE 3-D disk should contain:
DS3D.EXE, DS3D.OVR -- The main program and overlay files
{CGA, HERC, EGAVGA}.BGI -- Video drivers
README.DOC, INSTALL.BAT, INST1.BAT, INST2.BAT -- Installation Files
(These are used only when transfering files to a hard drive.)
DS3D.BAT -- Batch file for use on a hard drive to transfer you to the DS3D
subdirectory and run the program.
If DSCONFIG.FIL is present, the disks have been used previously and contain
someone else's configuration data. Delete this file. (The INSTALL program
will ignore it.)
-
The DS SUPPLEMENT disk should contain:
{PLCRUNCH, CONLINE, NAMENUM}.DAT -- External files needed by the program
CONVERT.EXE -- A separate program to convert among Version 1.3 comet files,
Version 2.0 (and later) comet files, and Text files.
CURRENT.CFL -- The most current Comet orbital elements. Use this file for
comets that are still observable.
RECENT.CFL -- Comet orbital elements from the last few years. Comet files
will expand as you add data on more comets. (You can keep up to date on
your comet files by subscribing to Comet Watch.)
TEXT.TXT -- The text file you are reading at this very moment.
SST01 -- The first of 6 star data files, distrubuted with the REGISTERED
version. The only star file accessable to the UNREGISTERED version.
-
\
The hard disk installation program INSTALL.BAT creates a directory called
\DS3D, and two sub directories called DSDATA and DSFILES.
--All of the files on the DEEP SPACE 3-D disk and most of the files on DS
SUPPLEMENT are copied to the \DS3D directory.
--SST01 is copied to the DSDATA sub directory. This is where all star data
files should be placed.
--The CONVERT.EXE program and the comet data files, CURRENT.CFL and
RECENT.CFL, are copied to the DSFILES subdirectory.
--The DS3D.BAT file is copied to the root directory.
If for some reason you want to use different directories, you must specify the
new path names when running the CHANGE CONFIGURATION option at the Main Menu.
+
>STARTUP OPTIONS
If you have obtained clean copies of the distribution disks, you were led
through the configuration procedures at the beginning of the program. You can
alter your choices at any time by selecting the CHANGE CONFIGURATION option at
the Main Menu. If the file path options or the video display options are not
set properly for your system the program will most likely crash. Other
choices are more benign, but important for the user.
The first item on the configuration agenda is to specify the type of video
card in your machine. The issue is the video card, not the monitor. You may
have a monochrome monitor with a Color Graphics video card. The program will
attempt to detect which card is present. Under normal conditions you should
be able to accept the default selection. This option is provided to override
the program's choice if it is unable to detect the correct card or if more
than one video card is present.
If you have something other than a Hercules display, your next choice is the
combination of colors to use. Try the function keys as indicated to see the
range of possibilities and find a combination that is easily readable.
-
Next, give the locations of the various groups of files indicated. If they
are on floppy disks, give the drive letters. Remember, the main program files
(DS.EXE and DS.OVR) must be continuously present on the default drive. The
remaining can be anywhere on the system, or swapped in and out at the program
prompts if they are on floppy disks. Even if the main program is on a hard
disk it is possible to use floppies for some of the remaining files.
Next, specify the number of SST (Star data) files you are using. You should
have only SST01 with an UNREGISTERED disk pair, and as many as 77 files if you
are a registered user.
-
Finally, there are two screens that have to do with your geographic location.
You may describe a primary and a secondary observing site. A third site may
be defined "on the run" while running various options in the main program. It
too will be stored until it is redefined.
Look on a large scale atlas at a library to find the latitude and longidude of
your observing site as accurately as possible. Take a stab at your altitude.
The accuracy here is not critical for most purposes.
The name of your time zone is for printout purposes only. The number of the
time zone is more critical. A partial table is provided to help determine the
correct number. Daylight time shifts U.S. observers one hour closer to
Greenwich (subtract one hour), and Asian observers one hour farther from
Greenwich (add one hour).
+
+
>DEFAULTS
How do you make a program simple enough for a beginner and at the same time
powerful enough to satisfy an expert? One way is to allow lots of choices for
the experts, even regarding picky details, but to suggest an answer to every
question that at least makes sense. A "default" is computer jargon for those
pre-selected answers provided by the program. DEEP SPACE 3-D has defaults for
just about everything! This makes it easy to explore areas you may not
understand very well at first. If you come to a question you don't care about
or don't understand, just choose the default and keep going. The more you
learn about astronomy, the more you will appreciate having control over all
the picky details.
To choose a default answer, simply type the <Enter> key. You will find you
can go through almost the entire program simply hitting the <Enter> key, and
still get something of interest. If you come to a whole page of questions and
like the looks of all the default answers, simply jump to the bottom of the
page with the <PgDn> key and keep going. As you get more comfortable with the
program and read more about astronomy, you will find the program's
capabilities will keep up with your growth along the way.
>DATA ENTRY
Data is entered either by making a selecting with a scroll bar or typing data
directly into input boxes.
To use the scroll bar, move up or down with the arrow keys, page up or down
with the <PgUp> and <PgDn> keys, go all the way to the beginning or end of a
list with the <Home> or <End> keys. You can also select entries by their
first letter. The cursor will cycle through all the entries having the same
starting letter.
When entering data into the input boxes, most single character entries do not
require the use of the <Enter> key. Simply press the appropriate key. To
allow you to recover from accidental keystrokes, there is usually an entry at
the bottom of a page to confirm the earier entries on that page.
When editing an existing entry, if the first key typed is a normal character,
the entry will be erased under the assumption that you want to retype the
whole entry. If you want to edit the entry without destroying what is already
there, make the first keystroke with a <Home>, <End>, or Arrow key. After
destroying a few entries you will get used to it.
>WHAT'S UP: SUMMARY PAGE
The What's up option is a handy grab-bag of features for anyone who actively
observes the sky. After specifying a target date you are given information
that you may want to use to refine your choice of date or narrow in on a time
most suitable to your observing needs.
The sun and moon both cast a lot of light and can adversely affect
observations of other fainter objects. New Moon equals No Moon. The time of
New Moon (plus or minus a few days) is traditionally the best time of the
month for astronomy club star parties. First quarter moon will be overhead in
the evening sky, setting around midnight, and third quarter moon will not rise
until near midnight. First quarter moon is a good time for public viewing
since the moon itself is a prime telescopic subject for the general public.
First quarter is also good because the craters cast long shadows along the
terminator (the moon's "twilight zone") making them more visible.
Sunrise and sunset are also important. Times vary considerably throughout the
year, especially at higher latitudes. Astronomical twilight is defined as the
time when the sun is 18 degrees below the horizon. This is the time when the
+sky is generally considered dark for astronomical purposes.
>WHAT'S UP: PLANETS, ETC
The Planets page of the What's Up option gives a wealth of information for
anyone who wants to read it. The other option is to let the computer digest
the information and display it visually on a map of the day and time. In
summary the column headings mean the following:
R.A. --Right Ascension: angle in hours, not degrees, measured
eastward along the equator from the Vernal Equinox.
Dec --Declination: angle above or below the celestial equator
measured in degrees.
Az --Azimuth: angle in degrees measured eastward along the horizon
from due south.
Alt --Altitude: angle in degrees above or below the horizon
Elong --Elongation: the angle of the planet from the sun measured along
the ecliptic.
-
The remaining categories are rise, set and related times. Besides rise and
set times there are three other categories:
20 deg rise/set: time of rise or set at a hypothetical "smog line" 20 degrees
above the horizon. Even if there is no smog, at 20 degrees above the horizon
you are looking through 3 times as much atmosphere as directly overhead.
Transit: the time when the planet crosses the local meridian (the local
meridian being the north-south line passing directly overhead).
If a planet never rises, the rise and set times are marked: -----
If a planet never sets, the rise and set times are marked: +++++
(Similarly if a planet never crosses the 20 degree altitude mark)
The time of transit is indicated even if the planet is below the horizon at
that time.
>WHAT'S UP: COMETS
You may be able to tell this program is heavy on comets! Comets are
interesting observational targets, although beginners often have difficulty
locating them. Most require a telescope or at least binoculars to observe.
The comet ephemeris option follows a single comet over an extended period of
time. The What's Up comet section, on the other hand, is a time cross
section. It shows where any number of comets are at a single time. Usually
not more than two or three comets are actually bright enough to see at one
time, but the others are still out there and may be plotted. This is
especially useful if you want to avoid mistaking a known comet for a new
discovery (cf. SAGA, Part III).
The comet option shows R.A., Dec., Elongation, rise, set, 20-deg rise and set,
and transit times (see planet page for descriptions of these). Also if the
appropriate information is available in the file, an estimated magnitude is
given. These are only crude estimates, but they may indicate whether a given
comet is conceivably visible at a given time.
|
Finally, you are given the opportunity to "select" any number of comets. If a
comet is selected, it is put in a file with the planets to be displayed on the
Day and Time star map. For selection purposes you have several options:
Y: Select a given comet
N: Reject a given comet
S: Select all of the remaining comets
R: Reject all of the remaining comets (but still scroll through them)
<Esc>: Keep what has been selected so far, and quit.
If you type S or R, you may interrupt the scrolling at any point and revise
your selections from that point onward.
>COMET ELEMENTS
You can enter the orbital elements for a comet in the Comet Ephemeris option.
Orbital elements are six numbers that describe a comet orbit's size, shape,
orientation in space, and time of closest approach to the sun. They have
strange names, but you don't have to know anything about them to be able to
plug them into Deep Space 3-D. If you subscribe to Comet Watch or get the IAU
circulars directly, simply put the right numbers in the right slots and let
the computer go at it. Deep Space 3-D prints out the numerical data and then
allows you to display it in a variety of ways.
The knotty problem has been how to obtain the elements. This is not the kind
of thing you could get from monthly astronomy magazines. The news is of the
fast breaking variety. You could subscribe to the IAU Circulars directly, or
rely on your local planetarium for information, but now you can get elements
inexpensively and fast by subscribing to COMET WATCH. See the CATALOG & ORDER
FORM heading for information on how to subscribe.
-The six magic numbers for comets are as follows:
\
Orbital Elements
T : Time of perihelion passage--when the comet is closest to the sun
e : Eccentricity--a measure of the elongation of the orbit. For a
circle, e=0. For a parabola, e=1. Above 1 the orbit is a hyperbola.
q : Perihelion distance--closest approach to the sun
PERI : Argument of perihelion--measures the orientation of a comet's orbit
within its own orbital plane. (Symbol = lower case Greek Omega.)
NODE : Longitude of the Ascending Node--locates where the comet's orbit
crosses the ecliptic plane. (Symbol = upper case Greek Omega.)
i : Inclination--the angle bewteen the orbital planes of the earth and
comet.
These are published in IAU Circulars by the Center for Astronomical Telegrams
after a new comet has been discovered and tracked for several days. Refined
elements are typically published after a longer period of observation.
>COMET FILES
If your interest in comets is purely observational, you can delete most long
period comets after they have faded. They will never return in your lifetime.
However, for other aspects of comet study you may want to collect orbital data
to compare comets even after they are long gone. One of the optional disks
available to registered users has data on over 1100 comets dating back to the
first confirmed sighting of Comet Halley in 240 BC (which astronomers refer to
as the year -239. For astronomers, the year preceding 1 AD is 0 AD. For
historians the year preceding 1 AD is 1 BC.)
+
In any case, if you collect large amounts of orbital data it can best be kept
in multiple files. The CURRENT.CFL and RECENT.CFL files are on the
distribution disk and are the only .CFL files accessible to the UNREGISTERED
version of the program. The REGISTERED version allows you to add .CFL files
without limit.
To start a new file with fresh data, choose the Ephemeris Option at the Main
Menu. When the existing comet files are shown, type <Esc> to start a new
file, and type in the new file name when asked. You will then be presented
with the data entry form where new elements can be typed in.
-
Instead of entering fresh data into the new file, data can be copied to a new
file or between existing files. To do this, select a comet in an existing
file, and choose the Copy option shown at the bottom of the page when its
elements are displayed. A menu of existing comet files will be shown allowing
you to select which file to copy it to. If you want to start a new file, type
<Esc> to enter the new file name.
Another option at the same point where the copy option is offered, is to
delete a comet. You may well want to enter new comet data in CURRENT.CFL,
then copy it to RECENT.CFL and delete it from CURRENT.CFL when it is no longer
easily visible.
The program CONVERT.EXE is a separate program supplied with DEEP SPACE 3-D
which must be in the same subdirectory as the files it operates on (by
default, \ds3d\dsfiles, if you have a hard disk). It will convert .CFL files
to or from the old Ver. 1.3 .DAT files, and also to or from ASCII .TXT files
that can be read, edited, or organized with a text editor or word processor.
If text files are to be converted back to .CFL form, they must be in pure
ASCII and follow the exact pattern of the text files produced by CONVERT.EXE.
>DAY AND TIME OPTIONS
You can enter the starting day and time and range of dates for a comet
ephemeris in several ways, depending on the purposes you have in mind. If you
want the program to display a comet orbit in relation to the earth's orbit,
choose the "A" option. This allows you to select the calculation interval and
number of calculations, and the program chooses the starting date to be
symmetric about perihelion.
If the comet has a relatively short period you will be asked if you want to
compute positions for an entire orbit. If you intend to display the comet on
the screen, there is room in the allocated memory space for 500 points,
counting the comet head, comet tail, sun, earth, and any other planet or comet
positions that might be included. Based on this space, the program will
propose an interval and a number of positions to close the orbit. Look at the
proposal and decide if it will be satisfactory for your purposes. Remember,
comets move very quickly near the sun and very slowly far from the sun, so the
jumps can get to be quite large if the interval is too long. If the interval
is 10 to 30 days, the results will usually look reasonably good. If the
interval needed to get a complete orbit exceeds a year, the option is not even
offered.
-
Day-and-Time star maps are for a particular day and time, so comet ephemeris
calculations must be coordinated with this data to be meaningfull. This is
done automatically when you choose option "B". Option B ephimerides are
linked to particular What's Up computations. All you have to do is specify
the computation interval and number of computations.
+
The C option is new with Version 2.1. It produces special search charts for
comet recovery. When comets return after long times at the far end of their
orbits their orbits are frequently altered. The most common element to be
affected is the time of perihelion passage, T. To aid in finding "lost"
comets the Comet Recovery Mode predicts a range of positions for each date
based on an assumed uncertainty in the perihelion time provided by the user.
Unless you are an active comet hunter you will probably never use this option.
The D option allows direct entry of day, time, and calculation interval. To
intelligently decide whether to run for morning or evening hours, you need to
know whether the comet will be a morning or evening object. The program
therefore displays the times of sunrise, sunset, morning and evening twilight,
and the rise, set, and "20 degree horizon" rise and set times of the comet.
-Everything you need to make your decision is there when you need it.
Since the four time selection modes are for different purposes, their
ephemeris files are marked with different extensions: .EPA, .EPB, .EPC & .EPD.
When you want to do orbit plots, .EPA files will be listed. For Day and Time
charts, only .EPB files will be listed (and you will be warned if the one you
choose has incompatible dates). For comet recovery charts only .EPC files
will be listed. For other charts, all types of files will be listed.
>COMET EPHEMERIDES
An ephemeris (plural: e-phe-mer'-i-des) is a numerical listing that shows
where a celestial body will be in the sky over a range of dates. The
ephemeris listings produced by Deep Space 3-D also give information about the
appearance and spacial location of comets. The headings are as follows:
(The range of dates goes down the left side of the page.)
R.A. & Dec --Position in the sky in equatorial coordinates
R --Distance from sun to comet
Delta --Distance from earth to comet
Elong. --Elongation: angle from sun to comet as seen from earth
Phase --For a comet this tells to what extent the tail points away
from us. 90 degrees is directly across our line of sight.
PA --Position angle: the angle of the tail in the sky measured
counterclockwise from north
---------
Mag. --Estimated magnitude (emphasis on estimate!) if you have entered
magnitude data for the comet.
If you are planning to plot the comet path on a star map be sure to save the
output as a file. If you wish to export the printed ephemeris to a word
processor, save the printout as an ASCII file as well.
\
>STAR MAP TYPES
Deep Space 3-D can produce star maps in several different coordinate systems,
each useful for a particular purpose.
Star Atlas Mode--Equatorial Coordinates measure positions relative to the
celestial poles and equator. Right Ascension is similar to longitude, but it
is measured in hours (24ths of a circle) instead of degrees (360ths of a
circle). This is the way star atlases display various parts of the sky.
+
Day and Time Mode--Horizon Coordinates measure positions relative to the
horizons and the zenith. Since the sky rotates, this changes constantly. A
chart printed in this mode is good for a specific day and time. The charts
are actually useful over a range of dates if they are used slightly earlier
each night. If you want to observe throughout the night you will want a
planisphere (a "Star Wheel"--see CATALOG & ORDER FORM) that can be taken into
the field and updated from one hour to the next. For a specific celestial
event, or brief observing period, however, Day and Time mode charts generated
by Deep Space 3-D will give very good service. They are ideal for passing out
to a scout troop or school group for an evening's sky orientation. Day and
Time Mode charts can also be zoomed to a horizon view looking in any of 16
compass directions.
-
Solar System Mode--Ecliptic Coordinates are most useful when studying motions
of objects in our solar system. The earth's orbital plane is called the
"ecliptic" plane, hence the name. Any plane cutting through a sphere cuts it
along a circle (imagine cutting an orange in half). That circle where the
ecliptic plane meets the sky is called simply the "ecliptic". It marks the
centerline of the Zodiac band, the path of the sun, moon, and planets through
the sky. To print out a full sky map with the Zodiac as the center line, try
an E-W Mercator Projection with 360 degrees per 10 inches (for a full page)
centered at 0 degrees Longitude and Latitude in ecliptic coordinates. To look
at comet orbits from space in such a way that the earth's orbit is horizontal,
use ecliptic coordinates for the base map looking toward a slightly negative
ecliptic latitude.
-
Milky Way Mode--Galactic Coordinates are based on the circle of the Milky Way
through the sky. Zero degrees longitude and latitude is looking directly into
the center of our galaxy, which happens to lie in the direction of
Sagittarius. Try plotting a whole sky map (E-W Mercator Projection) down to
about 5th magnitude in Equatorial Coordinates. The screen will become quite
cluttered, but the dense band of stars along the Milky Way will stand out
clearly. (There is an upper limit of 5000 stars that can be held in the
allocated memory area at one time, hence the 5th magnitude suggestion.)
If the map is repeated, but this time in Galactic coordinates, the dense star
band will lie right along the center line of the page. This is a useful
projection when studying distributions of objects relative to the plane of our
galaxy. A future update to Deep Space 3-D will have a large database of
galaxies, nebulae, star clusters, etc., for which this projection will produce
some interesting results.
-
Match the Sky Mode--Starting with Version 2.1 a new option has been added to
the Map Type selection list. Match the Sky Mode produces a special type of
chart that is handy for beginners, or for people working with beginners.
Imagine pointing out a constellation to a beginner. It would be handy if you
had a picture of the constellation that matched the sky exactly, not only in
shape, but also in size. Most constellations on charts are small, while their
counterparts in the sky look huge by comparison. This can be confusing at
first. In Match the Sky Mode you simply specify the constellation of interest
and the distance in front of the eyes you want to hold the chart. The correct
projection and scale will be chosen automatically to match the sky.
+
>MAP PROJECTIONS
When a spherical surface is plotted on a flat map something has got to give.
Stretching will always occur. The question is what kind of distortion is
least bothersome for a particular application. Some projections distort
shapes, others distort areas. Others introduce more exotic distortions.
Generally speaking, for constellation recognition preserving shapes is
important. Thus the collection of projections offered here specializes in
shape preserving projections of one kind or another.
The Stereographic Projection should not be confused with stereo viewing of 3-D
images. (The possible confusion is particularly apparent in this program that
highlights stereo 3-D!) Basically, to flatten out a rubber ball, the edges
must be stretched, causing a lengthening in the east-west direction. The
Polar Equidistant Projection has just such a distortion. The Stereographic
Projection compensates for the shape distortion by stretching the surface
radially so east-west and north-south distortions match at every point. The
result is gross exaggeration of size far from the center, which is the price
paid for keeping the shapes correct. Overall, the Stereographic projection is
a reasonable compromise for general purpose use, so it has been chosen as the
default projection.
-
The Mercator Projection was designed for making earth maps for navigation. If
you follow the compass bearing of a line on a Mercator Projection you will get
to your destination.
For celestial use it is more relevant to note that this map has the same kind
of "compensatory stretching" as the Stereographic map, so it also preserves
shapes at the expense of gross area distortion far from the center line. But
whereas the Stereographic projection is accurate at a point, the Mercator
projection is accurate along a line. It is a good choice if the subject of
interest is primarily oriented along one particular direction, such as a
Zodiac band or any other wrap-around view of the sky. Two variations are
offered here: N-S and E-W, depending on the nature of the material to be
mapped.
The Gnomonic Projection is the kind of a projection produced by a camera. You
might think this would be the ideal projection, but both size and shape are
grossly distorted far from the center. It is, however, a useful projection
for small areas, especially if computer generated star maps are to be overlaid
onto photographs. The Gnomonic projection is used in Match the Sky Mode.
>STELLAR MAGNITUDE
Star brightness is measured on a "magnitude" scale. This is a scale
originally based on naked eye estimates of brightness. First magnitude
represents the brightest category or "First Rank" stars. Sixth magnitude
represented the faintest stars visible to the unaided eye. Thus increasing
magnitude implies decreasing brightness. Telescopes have extended the scale
to much higher numbers and photometers have increased the precision to several
decimal digits.
Generally speaking, if you want to plot naked eye stars, you should cut off
somewhere around 6 or 6.5, depending on whose eyes we are talking about: about
6000 stars. If you want a whole sky map, this is far too many stars for a
useful chart. The single file database with the UNREGISTERED version goes
down to Mag. 5.6, with over 3200 stars. The 6-file database that comes with
REGISTERED version goes a little beyond Mag. 7.25, for a total of more than
19,000 stars. The whole 77 file database go down to about Mag. 10, with spotty
coveage near the limits, nearly 250,000 stars in all.
+
The full database is most useful when you want to look at a small part of the
sky in detail. With the full database you could plot the Pleiades star
cluster to a scale of 1 degree per inch, and still have a field rich in stars.
>USING THE CURSOR
Once a map is plotted there are a number of interactive features accessed with
the function keys.
<F1> brings up a cursor. Move it with the arrow keys, for small jumps, or
with the arrow keys in conjunction with the <Shift> key for single pixel fine
adjustments. (The <Shift> key will only work with the arrow keys that are
part of the numeric keypad.) If the cursor is centered on any object (star,
planet, comet, etc.) the object will be identified. If two stars are overlaid
on the same pixel, both stars will be identified in sequence.
<F7> uses the cursor in a different way. If planets or comets are "overlaid"
onto the star map, the <F7> cursor will jump from one to the next. For comets
and planets generated by the What's Up routine it will simply give the name
of the object. For comets generated by the ephemeris routine, it will give
the name of the comet, and also the date, since the different images are for
different dates. One particularly impressive use of the <F7> cursor is to
trace out the path of a comet orbiting the sun along with the earth. See the
COMET PATHS FROM SPACE section for more details.
>SAVING AND MODIFYING MAPS
The <F2> function key cycles through a number of useful options for saving,
re-displaying, and altering maps after their original computation.
Star maps may be saved, previously saved maps may be restored, and the number
of stars on the map may be increased or decreased. A saved map can be
restored much faster than it can be computed in the first place because all
the heavy math has already been done. This feature will be especially
appreciated by those who have the older slower PC and XT type computers
without math co-processors.
A saved map may be redisplayed either from the <F2> function key or from the
main menu. A directory of all saved maps will be generated from which you can
select a map with the scroll bar. Once a map is restored it is ready for any
function that could be performed on a freshly computed map.
Specific constellations may be highlighted or faint distracting constellations
can be suppressed with another <F2> option. Label the constellations ahead of
time and delete the names of the constellations you wish to ignore. Using
<F2> you can re-draw the constellation lines for named constellations only.
>ZOOMING
To Zoom a star map that was printed in Star Atlas, Solar System, or Milky Way
modes, type the <F3> function key. A rectangular box will appear at the
same proportions as the full-screen map. Manipulate the box with the <PgUp>
<PgDn> and Arrow keys to frame the view that is desired. For finer
adjustments use the same keys in conjunction with the <Shift> key. <Enter>
actuates the zoom. Once the map has been zoomed, typing <F3> again will
restore the original dimensions. If the print option is chosen while a map is
zoomed, the zoomed view will be printed.
+
The Zoom feature is different for Day and Time Mode. Here the Zoom takes you
from a whole sky view to a horizon view. Directions are specified by the
points of the compass: N, S, E, and W specify the quadrants; NW, NE, SW, and
SE split half way between the primary divisions; N-NE, E-NE, E-SE, S-SE, etc.
split the difference once again for a total of 16 possible directions. The
Left and Right Arrow keys step by 16ths, the Up and Down Arrow keys step to
the nearest 8th, the <PgUp> and <PgDn> keys step to the nearest quadrants, and
the <Home> and <End> keys jump to North and South. <Esc> takes you back to
the whole sky view.
\
>CONSTELLATIONS
Constellation lines are drawn with the <F4> key. Once they are drawn, the
<F4> key generates constellation names. Once the names are generated the <F4>
key is used for moving the names.
The constellation names present a bit of a programming challenge if the goal
is to use them on printouts. First, they tend to obscure the stars, and
secondly, the screen representations (which differ from one type of video
monitor to another) may bear little resemblence to the actual text size on
paper. Furthermore, not all constellation names that show up on the screen
may be desirable. Sometimes only a tiny corner of a constellation intrudes on
the edge of the paper and you may want to ignore it. Or, if you are dealing
with students, you may want to focus their attention on a few of the brighter
constellations only.
To solve these problems as conveniently as possible the following method has
-been devised:
1. Constellation names on screen are in the smallest font for that screen
provided by Turbo Pascal (the programming language being used).
2. Names are popped into position automatically on the second <F4> for quick
and easy identification of constellations even though they might overwrite
significant details of the maps. Each constellation name is associated
with the brightest star of a constellation that is shown on the screen,
usually displayed a short distance to the right of the star.
3. By typing <F4> a third time you can enter a mode that will cycle through
the constellation names, forward through the alphabet with the <Enter> key,
or backward with the <Backspace> key. The highlighted name can be
positioned with the arrow keys, in conjunction with the <Shift> key for
finer spacing.
4. As a name is being moved, it is represented by a small rectangle that
represents the computed size of the printed version of the name. This
will aid you in placing it properly. Once the <Enter> key is typed the
name will pop to the location of the rectangle.
5. For crowded conditions you may wish to substitute the three letter
abbreviations for the full constellation names. Use the <PgDn> key to
shift to abbreviation mode and the <PgUp> key for full name mode.
6. Double word names, such as "Ursa Major" or "Canis Minor" are by default
placed one above the other. The <End> key will link them end-to-end and
the <Home> key will return them to stacked form. The form of each double
- name is controlled individually.
7. Names may be deleted with the <Del> key.
8. If you plan to print out a zoomed view, you should postpone positioning the
names until your final step before printing. Names positioned for one view
do not necessarily match what would be desirable in a zoomed view, so the
offsets are canceled upon zooming.
9. If constellation lines are drawn the <F2> Save/Modify command offers an
option to erase all the lines and draw only the constellations that are
named. Faint constellations that might be a distraction for some purposes
can be eliminated in this way.
+
>PLANETS, ETC.
Planets come in two varieties: those that outshine most if not all of the
stars (Mercury, Venus, Mars, Jupiter, and Saturn), and those that require
optical aid even to be seen (Uranus [borderline], Neptune, and Pluto). The
positions of the Sun, Moon, and all the planets are computed in the What's Up
routine. This information may be displayed on a star map (any variety) by
pressing the <F5> key. On first press the sun, moon, and bright planets will
be shown. To get Uranus, Neptune, and Pluto, press it a second time. Any
comets computed with the What's Up routine will also be shown along with the
bright planets.
The planets are identifiable by their symbols. Further identification is
possible using the <F7> key to jump from one to the next, displaying their
names in a box at the top left corner of the screen. Planets may also be
identified manually by placing the <F1> cursor on the symbol. For symbols
with a circular portion, such as the Sun, Moon, Earth, Mercury, Venus, Mars,
and Uranus, the pixel to hit is the center of the circle. The asymmetric
symbols, Jupiter, Saturn, Neptune, and Pluto, have a small dot added near the
center of the symbol for targeting.
>COMET PATHS FROM EARTH
Comet paths seen from earth could be termed "finder charts". They can be
plotted on any kind of base map, but equatorial "Star Atlas" mode and "Day and
Time" mode charts would usually be the most useful. For detailed finder
charts, plot an ephemeris for intervals of 1-5 days, usually for 10 or 15
calculations at a time. Find the center of the path from the ephemeris as a
best first guess for the map coordinates to use.
A word here about comet tails is in order. The tail displayed by the program
is in no way a prediction of actual tail length: it is fixed at an artificial
a 1/10 AU length (about 10 million miles). However, it does reflect the
effect of distance and phase on apparent tail length, and it is shown at the
correct position angle on the sky for an ion tail, which points directly away
from the sun. This can be a useful observing aid if you think you detect a
possible faint tail and wonder if it is in a plausible direction. Remember,
some comets have anti-tails and dust tails are sometimes quite curved. The
length of the displayed tail is the length the tail would appear if it were
actually 1/10 AU long. If the observed tail is half that long you know that
the physical length is about 5 million miles. The plotted tail is thus not a
prediction, but a yardstick.
-
Another interesting question arises when plotting a comet path on a Day and
Time mode star map. By definition a Day and Time mode map is for a particular
day and time, yet also by definition, a comet path is extended over a period
of time. How can the two be meaningfully combined? The method of display
here is somewhat of an innovation, but I think it is a very helpful way to
treat the data.
On the Day and Time mode maps, two paths are shown: one follows the path of
the comet relative to the stars, the other follows the path of the comet
relative to the horizons. If the starting day for the ephemeris matches the
date of the map, the two initial marks will coincide. But then, since the sky
rotates over the plotted interval, the two paths diverge. The normal plot
(plus mark with a tail) indicates the path relative to the stars. The other
path is marked with X's. This is the path that for a given time of night
shows when the comet will be highest above the horizon and how long it will
remain in the observable portion of the sky. Some comets are "horizon
huggers", so this information is critical to evaluating their potential
+visibility.
>COMET ORBITS FROM SPACE
When a comet ephemeris is generated with the "A" option (symmetric about
perihelion) it is suitable for tracing out the whole orbit, or a significant
portion of its inner orbit, as seen from a point off the earth. To create a
sample orbit view follow this recipe:
1. Pick a comet and generate an ephemeris using day and time option A. Take
all of the default settings from there on out. When asked for a file name,
choose the default name (good for "scratchpad" storage) or choose a
different file name.
2. Generate an Ecliptic Coordinate star map (Option C). Select by
Coordinates (option B): any Longitude you want (0 is ok), but some negative
angle (-25 would be good) for the Latitude. That is so you will be looking
down on the solar system at an angle from above. The direction specified
is the direction we are looking TOWARD. Take all the defaults for scale,
projection, etc. (or choose the Gnomonic projection for somewhat better
renditions of ellipses and parabolas).
3. When the star map comes up choose Option 6 for comet paths, and select to
see it from Space rather than earth. Take the default viewer distance (5
AUs is about the distance of Jupiter) and at the menu select the ephemeris
- you have just generated.
4. The sun will be plotted first, followed by a comet path. When the comet
gets within 6 months of perihelion the earth will also kick in, so both
will be orbiting the sun together.
5. Now comes the good part. Choose the <F7> cursor option. The cursor should
land on the sun and a box at the top left corner of the screen will say
SUN. Typing the <Enter> key, the cursor will jump sequentially to each
position that was plotted, identifying the object and the date. To speed
up the process type the <End> key to disable the identification box.
(There is no mention of the <End> run option in the program itself; you
have to learn it here.) Typing it again will bring the box back, but leave
it off for now. Hold down the <Enter> key for an animated view of the
earth-comet encounter. The motion can be stopped and the <End> key typed
to bring up a date at any point.
6. Several comets can be put on the screen simultaneously as long as the total
number of points (counting heads, tails, sun and earth) does not exceed
500. If tails are left off, more comets can be included.
\
>CLEARING OVERLAYS
The Planet and comet images on the video screen can be though of as overlays
superimposed on a star base map. Typing <F8> (twice for safety) clears the
overlays without having to start the map computation from scratch. You can
thus experiment with various options without committing to them for the final
printing.
\
>3-D / LARGE AND SMALL
Space is 3-dimensional. The sky we see is a two dimensional surface because
of the limitations of our depth perception. At great distances all things
look the same distance away, hence we seem to be at the center of a sphere.
In other words, the dome of the sky is an illusion. It takes the illusion of
stereo graphics to dispell the illusion of the sky.
To see 3-D you need two points of view that are sufficiently far apart
compared to the distances of the objects being viewed. In a room, normal eye
spacing gives ample depth perception. Depth is easily judged 10 or 20 feet
away by eyes that are about 2.5 inches apart: a factor of 50-100 eye spacings.
Keep this in mind when it comes to plotting stereo views of the stars. A
simulated "eye spacing" of a few tenths of a light year will bring out depth
+well into the distance among the stars. Over doing the eye separation is like
trying to look at something an inch or two in front of your face. On the
other hand, increased eye spacing can bring out the relative depth at greater
distances if there are few nearby stars sitting distractingly on the end of
your nose. Be flexible and experiment. See for yourself the difference
changing the eye spacing makes for different views.
-
To see 3-D you probably need a viewer. Some people can teach themselves to
view the small scale 3-D views without a viewer, one eye looking at each
frame, but the viewer makes the process much easier. The small scale 3-D
views are limited by the actual spacing of human eyes: the squares can be no
larger than the distance between the eyes. The small scale viewer that comes
with the registered program helps focus each eye onto a separate picture. The
brain fuses the information from the two slightly different flat pictures into
a single 3-dimensional image.
The large scale 3-D printouts are for use with a table-top viewer using
mirrors. With the large viewer two 8-1/2 x 11 sheets can be viewed side-by-
side for an incredible sensation of depth. It's like sticking your head into
a porthole.
Some of the things to notice when viewing the stars in 3-D:
--Some stars are bright because they are close, whereas others are bright
because they are BRIGHT.
--Some pairs of stars are close together in the sky but far apart in space.
Other stars are far apart in the sky but close to each other (and us) in
space.
--Some familiar constellations contain actual star groupings, others only
- apparent groupings.
\
Besides viewing the stars in 3-D, try viewing the planets and comets in 3-D.
When solar system objects are present the stars are flat in the background
since they are so much farther away by comparison. Eye spacings are now
specified in Astronomical Units (AUs) rather than light years. 1 AU is the
distance from the earth to the sun. An AU is to a light year as an inch is to
a mile (almost exactly!). Planets are really very local. Using the distance
to eye spacing ratio of 50 or 100 as discussed above, a 3-D view looking at
the sun and inner planets from the earth should require an eye separation of
only about 0.01 to 0.02 AUs. 0.1 AU is adequate for viewing a comet orbit
from the distance of Jupiter.
When comets are seen in 3-D the main point of interest is the orientation of
the orbits relative to the earth's orbital plane. Most of the solar system is
flat, but comets come in from all angles. The inclinations stand out
dramatically in this format.
-
The mechanics of getting the 3-D views is simple. For small scale 3-D hit
<F9>. A square frame will appear on the screen. Zoom it in and out with the
<PgUp> and <PgDn> keys and move it around with the Arrow keys. Make fine
adjustments with the same keys in conjunction with the <Shift> key. Hit
<Enter> when the desired view has been selected. Whatever has been chosen
will be scaled to a 2.5 inch format and printed in stereo.
The large scale 3-D views are whole page printouts and are requested through
the <F10> printout option. Simply type <F10> as printing normally, but answer
yes to whether you want the printouts to be in 3-D.
+
>PRINTOUTS
To make printouts of a whole map or a zoomed view, display whatever features
are desired on the video screen and then print by typing the <F10> key. You
will be asked whether you want the view to be flat or in 3-D. This would be
for the large scale 3-D view printed out on two consecutive pages. If you
have chosen a horizontal format and have the large viewer the two 8-1/2 x 11
inch pages can usually be left attatched for viewing in stereo. Keep in mind
that each picture in a stereo pair has points that are offset from their
normal positions, so the 3-D option is inappropriate if you intend to use the
printouts as finder charts at night.
>
Directory of PC-SIG Library Disk #0867
Volume in drive A has no label
Directory of A:\
NAMENUM DAT 41067 8-28-90 2:10a
CONLINE DAT 1800 8-28-90 2:10a
PLCRUNCH DAT 7964 8-28-90 2:10a
TEXT TXT 66882 8-28-90 2:10a
RECENT CFL 11792 8-28-90 2:10a
CURRENT CFL 402 8-28-90 2:10a
CONVERT EXE 59907 8-28-90 2:10a
SST01 65400 8-28-90 2:10a
FILE0867 TXT 3405 9-07-90 1:47p
GO BAT 38 1-01-80 1:37a
GO TXT 729 1-01-80 5:24a
11 file(s) 259386 bytes
57344 bytes free