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SkyBase 2000.0 SkyChart
Copyright 1988 - 90 Logan R. Zintsmaster
Logan R. Zintsmaster
450 Spring Hill Drive
Morgan Hill, CA 95037
CompuServe 71211, 2440
SkyBase 2000.0 SkyChart User's Manual
Table of Contents
1. INTRODUCTION 1
1.1 PROGRAM OVERVIEW....................................2
1.2 HARDWARE REQUIREMENTS...............................3
1.3 MANUAL OVERVIEW.....................................3
1.4 SHAREWARE RELEASE CONTENTS..........................3
1.5 RETAIL RELEASE......................................3
2. TERMS AND CONDITIONS OF USE 4
2.1 COPYRIGHT NOTICE....................................4
2.2 PROGRAM LICENSE.....................................4
2.3 WARRANTY............................................4
3. OPERATING INSTRUCTIONS 5
3.1 INSTALLATION........................................5
3.2 RUNNING THE PROGRAM.................................6
4. USING SKYBASE 2000.0 SKYCHART 7
4.1 KEYBOARD............................................7
4.2 MOUSE SUPPORT.......................................8
4.3 OPENING SCREEN......................................8
4.4 MAIN SCREEN.........................................8
4.5 CONFIGURATION SCREEN................................9
4.6 FINDER VIEW SCREEN..................................11
4.7 MAP VIEW SCREEN.....................................14
5. PLOT DISPLAY 18
6. NOTES 20
6.1 BUGS................................................20
6.2 DATABASES...........................................20
6.2.1 Star Databases....................................20
6.2.2 Non-Stellar Databases.............................20
6.2.3 Database Accuracy.................................21
6.2.4 Printer Aspect Ratios.............................21
SkyBase 2000.0 SkyChart User's Manual
Copyright 1988 - 90 Logan R. Zintsmaster
ALL RIGHTS RESERVED
1. INTRODUCTION
SkyBase 2000.0 SkyChart was written as shareware to make sky charts that
are oriented the way you need them: normal, inverted, or mirror image. The
sky charts can cover the whole sky or just enough to star hop with your
finder scope to the selected object.
SkyBase 2000.0 SkyChart was designed to use a disk database format so you
can select the database with enough data to be useful but not so much as to
be confusing. Current databases are constructed from the Yale Bright Star
Catalog, the Smithsonian Astrophysical Observatory star catalog, the
Messier objects, a collection of "best" NGC objects, and the Saguaro
Astronomy Club catalog. As new data sources become available, new
databases will be added.
The program can be used with a graphics-capable IBM compatible computer,
including lap-tops, and can produce hardcopy on an Epson or IBM compatible
dot matrix printer.
- Page 1 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
1.1 PROGRAM OVERVIEW
The initial requirement for SkyBase 2000.0 SkyChart was to produce finder
charts for users of telescopes which have an odd number of reflecting
surfaces. This optical configuration produces a mirror image, that is,
upright but left-right reversed. Conventional practice to develop finder
charts is to trace the required area of the sky from a sky chart, then flip
the paper over and shine a light through it. SkyBase 2000.0 SkyChart does
this electronically and more.
The features of SkyBase 2000.0 SkyChart include:
- Generation of Finder Charts: You pick chart center and size
and field of view of your finder scope or telescope.
- Generation of Star Charts: You pick the Right Ascension and
Declination limits.
- Display either erect, inverted, or mirror image, with or
without grid lines.
- Selectable limiting magnitudes, objects, and databases.
- Available databases include data from the Yale Bright Star
Catalog, SAO Star Catalog, Messier Objects, a collection of
"Best" NGC objects, and the SAC 5.0 database of non-stellar
objects.
- Display configurable for lap-top screens for use at the
telescope.
- CGA/EGA compatible with Microsoft Mouse support.
- Screen oriented input with fill-in-the-blank data entry for
ease of use.
- Hardcopy output for Epson and IBM compatible dot matrix
printers.
The next question on your mind is likely to be, "But does it work?" Yes,
it does. I have taken SkyBase 2000.0 SkyChart and my lap-top out to my
telescope and used it to find several Messier objects. The objects were
found by matching the SkyBase 2000.0 SkyChart display of the field around
the object with the view in my finder scope. When I switched to the
eyepiece, the object was there to be seen. In my book, that's the acid
test.
So much for the editorial, now enjoy the program.
- Page 2 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
1.2 HARDWARE REQUIREMENTS
SkyBase 2000.0 SkyChart runs on an IBM PC or PC compatible with 512kB of
memory, a CGA, EGA, or compatible display, either monochrome or color
monitor, and one or two floppy disk drives (depending on the databases
used), or 1 MB of hard disk space. It will also operate on an IBM
compatible lap-top.
1.3 MANUAL OVERVIEW
The manual for SkyBase 2000.0 SkyChart is simple and straightforward. Each
of the input screens is described, as well as the plot display. The input
fields in these screens are discussed and the operation presented. The
special keys used on the keyboard are also explained.
SkyBase 2000.0 SkyChart was designed to be easy to use, so it is hoped that
this manual will not be needed often.
1.4 SHAREWARE RELEASE CONTENTS
The shareware release of SkyBase 2000.0 SkyChart contains a fully
functional program plus a stellar database, a non-stellar database, and a
text file for producing this manual on a printer. This package is a
reasonable size for downloading.
Due to their sizes, the other databases are mailed upon request. Operation
of SkyBase 2000.0 SkyChart is not changed, only more objects are available
for plotting.
1.5 RETAIL RELEASE
A retail version, SkyBase 2000.0 Plus, is also available. This version
incorporates the features of the shareware release and adds on screen
identification of non-stellar objects, additional hardcopy information, and
stellar data to magnitude 10 (258,000 stars). The registration fee (less
sales tax) for the shareware version may be applied to the cost of the
retail version. Shipping and handling are $4.00 additional.
- Page 3 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
2. TERMS AND CONDITIONS OF USE
2.1 COPYRIGHT NOTICE
The SkyBase 2000.0 SkyChart program and documentation are protected under
the copyright laws of the United States. The Runtime module is copyrighted
by Microsoft Corporation. The SkyBase 2000.0 SkyChart program, character
fonts, screen displays, and databases are copyrighted by Logan R.
Zintsmaster. All rights are reserved.
2.2 PROGRAM LICENSE
SkyBase 2000.0 SkyChart is licensed to the user under the "shareware"
concept for use on a single or subsequent computer by a single user. Non-
registered users are granted a limited license to use SkyBase 2000.0
SkyChart on a trial basis. A user is authorized to make copies and
distribute the program, freely, as long as no copyright or license notices
are removed; all documentation is included; and no fee, compensation, or
other charge is accepted or requested. SkyBase 2000.0 SkyChart may be
posted on electronic bulletin board systems for downloading by their users,
providing the above conditions are met. All rights are reserved by the
author.
Should SkyBase 2000.0 SkyChart be found useful, a license registration fee
of $25.00 shall be sent to the author (CA residents, please add 7% sales
tax),
Logan R. Zintsmaster
450 Spring Hill Drive
Morgan Hill, CA 95037
Registered users will receive a printed manual with a menu map, the latest
version of SkyBase 2000.0 SkyChart, and all available databases.
Retention and use of SkyBase 2000.0 SkyChart by a user shall be construed
as accepting this license agreement and the terms and conditions of use
specified herein. If the terms and conditions are unacceptable, a user
shall destroy or erase his copy(s) of the program, data files, and
documentation.
2.3 WARRANTY
There are no warranties, expressed or implied, and any such warranty is
expressly disclaimed including but not limited to implied warranties of
merchantability and fitness for a particular purpose either with respect to
defects in a supplied diskette, documentation, and the program license
granted herein in particular, and without limiting operation of the program
license with respect to any particular application, use or purpose.
In no event shall anyone developing, using, or distributing this program be
liable for any loss of profit or any other commercial damage, including but
not limited to special, incidental, consequential or other damages.
- Page 4 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
3. OPERATING INSTRUCTIONS
3.1 INSTALLATION
The files associated with SkyBase begin with the prefix 'SKY'. To install
SkyBase 2000.0 SkyChart on a hard disk, create a subdirectory with an
appropriate name, like 'SKYBASE'.
For example, on the C drive, the command to do this is
MD C: \ SKYBASE
----------------------------------------------------------------- -----------------------------------------------------------------
Please note that keyboard entries will be presented on a separate
line, or when embedded in text, surrounded by single quotes.
When making the entries, do not enter the single quote marks.
All DOS commands are ended by pressing the 'Enter' key, which
will not be shown, explicitly.
----------------------------------------------------------------- -----------------------------------------------------------------
Place the Program disk in your floppy drive and copy all files into the
subdirectory. Next, remove the Program disk and insert any Data disks.
Copy all the files to the subdirectory.
For example, to copy all the files on a floppy in the A drive,
use the command
COPY A: *.* C: \ SKYBASE
Repeat this until all data disks have been copied.
When installation of the downloaded version is complete, the following
files are needed for execution and should be in the subdirectory.
SKYBASE.EXE SkyBase executable
SKYBAS87.EXE SkyBase executable for 80x87 (registered users only)
SKYBASE.CGA Font File for CGA
SKYBASE.EGA Font File for EGA
SKYBASE.MDA Font File for EGA on Monochrome Display
SKYYLE.RND Yale Bright Star Catalog data
SKYYLE.NDX Yale Bright Star Catalog index
SKYMESS.RND Messier Objects data
SKYMESS.NDX Messier Objects index
SKYSAO.RND Star data from SAO Catalog (registered users only)
SKYSAO.NDX Star data from SAO Catalog index (registered users only)
SKYNGC.RND NGC Objects data (500 objects) (registered users only)
SKYNGC.NDX NGC Objects index (registered users only)
SKY.CFG Configuration data
- Page 5 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
The following files contain the manual and user registration form,
respectively.
SKYBASE.DOC Shareware version manual
SKYREGS.FRM Shareware registration form
3.2 RUNNING THE PROGRAM
To run SkyBase 2000.0 SkyChart, change directories to the SkyBase
subdirectory and start the program by using the command: 'SKYBASE'.
For example, using the subdirectory described earlier the
commands to start the program are:
CD C: \ SKYBASE
C:
SKYBASE
Once loaded, the copyright message is presented and the program begins
execution.
To try out SkyBase 2000.0 SkyChart, the following coordinates are suggested
for the Finder Screen.
Orion Right Ascension 5.30
Declination 0
Chart FOV 15
Big Dipper Right Ascension 12.30
Declination 55
Chart FOV 30
Sagittarius Right Ascension 18.40
Declination -30
Chart FOV 12
In the Map Screen, it is interesting set the ranges to plot the full 24
hour Right Ascension range over the full 180 degree Declination range and
note the dense band of stars that constitute the Milky Way.
- Page 6 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
4. USING SKYBASE 2000.0 SKYCHART
As stated in the introduction, SkyBase 2000.0 SkyChart was designed to be
easy to use. This section describes the keys used to control the program,
the five input screens used to control its operation, and, finally, the
plotted data.
4.1 KEYBOARD
SkyBase 2000.0 SkyChart is controlled by a series of fill-in-the-blank
screens. To enter data, several keys are used to control the data entry
process. These are discussed below.
The 'Enter' key finishes a field but generally does not conclude the entry
processing for the screen. This is reserved for the 'End' key on the
numeric keypad (the '1' key) or the 'F10' function key.
One exception is in the Main Screen where there is only one entry field.
Pressing the 'Enter' key will cause the selection to be processed.
The other exception is at the end of a sky plot. Pressing the 'Enter' key
will return to the Main Screen.
The 'End' and 'F10' function key are used to signal the end of the input to
a screen. When either of these keys are pressed, the actions entered on
the screen are performed.
'Del' and the 'Backspace (<-)' keys perform their usual functions. 'Del'
deletes the character under the cursor. 'Backspace' deletes the character
to the left of the cursor and moves the cursor one space to the left.
The Insert key, 'Ins', is not implemented because the fields are small.
The 'Esc' key stops the current action and returns to the previous screen.
The Numeric keypad is automatically set to the cursor control mode (i.e.
'NumLock' is disabled.) During data entry, the arrow keys can be used to
move within a field or from field to field. If you wish to use the keypad
to enter data, press the 'Shift' key to enter numbers; release it to move
the cursor.
The screen fields carry default settings on program startup or the values
from the previous entry. These defaults will be discussed in detail for
each screen.
On-screen messages are provided at the bottom of the screen as prompts.
These messages explain which keys to press to accomplish the next action in
the sequence.
- Page 7 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
4.2 MOUSE SUPPORT
If a Microsoft compatible mouse is available, it can be used to select
screen fields to be changed, enter input values, signal the end of input,
and select the plotting center for a Finder Chart. It can be used in the
Main Screen, Map View Screen, and Finder View Screen. It can not be used
in the Configuration Screen.
When entering data, clicking the left button will cycle the character under
the cursor through the sequence of acceptable input values.
Clicking the right button has the same effect as pressing the 'End' key.
Please note that when using a Microsoft Bus Mouse with an EGA display, the
mouse driver must be version 6.11 or later. Otherwise, the arrow will not
appear in the Plot Screen.
4.3 OPENING SCREEN
When SkyBase 2000.0 begins execution, the licensing and copyright screen is
displayed. To continue, press any key.
4.4 MAIN SCREEN
The Main Screen allows you to select one of three input screens in SkyBase
2000.0 SkyChart or to exit the program. Each of these selections is chosen
by means of a single letter entry. When the letter has been entered in the
field, press the 'F10', 'End' or 'Enter' key.
The data files which are currently in use are shown on this screen for
reference. They may be changed with the Configuration selection as will be
described later.
Also shown on the screen is the Local Sidereal Time (LST) at midnight (0
hours) Local Mean Time (LMT) for the date read from the system clock. This
value of LST is used to create a default set of parameters for a full sky
map centered on this time.
In some cases, SkyBase 2000.0 SkyChart will be used on the evening
following the calculated LST; however, this shifts the chart only 4m in
Right Ascension, a tolerable amount for most uses. If desired, these
default values can be changed when the Map Screen is entered.
- Page 8 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
Four selections are possible in the Main Screen:
C - Configuration: Configure SkyBase 2000.0 SkyChart
for the selected databases, display type, and
screen size.
F - Finder: Display a finder chart centered around an
object or a point of Right Ascension and
Declination.
M - Map: Display a section of the sky using Right
Ascension and Declination limits.
Q - Quit: Stop the program and return to DOS.
Each of these selections will be discussed in detail.
4.5 CONFIGURATION SCREEN
The Configuration Screen is used to tell SkyBase 2000.0 SkyChart where the
database files are located and the dimensions of your display. The
Configuration Screen can be entered from the Main Screen at any time during
execution.
The Configuration Screen consists of the following fields.
Star Database File: Enter the full pathname of the file to be
used for the star database. The path should start at the drive
and include the file name without the file extension (i.e. the
three letters after the period in the filename shown in the disk
directory.)
Following the installation example above, the entry for the Yale
Bright Star Catalog on a hard disk system would be:
C: \ SKYBASE \ SKYYLE
On a floppy based system, with the data on drive B:, the command
would be:
B: \ SKYYLE
The Notes section contains the names of the star databases that are
currently available. These database file names are also shown at the
bottom of the configuration screen.
Non-Stellar Database File: Enter the full pathname of the file to
be used for the non-stellar objects database. The path should
start at the drive and include the file name without the file
extension (i.e. the three letters after the period in the
filename shown in the disk directory.)
- Page 9 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
Following the installation example above, the entry for the
Messier Object database would be:
C: \ SKYBASE \ SKYMESS
On a floppy based system, with the data on drive B:, the command
would be:
B: \ SKYMESS
The Notes section contains the names of the star databases that are
currently available. These database file names are also shown at the
bottom of the configuration screen.
Monitor: Select the type of display that you would like on the
monitor. There are three selections:
B - Used for single color or monochrome displays.
R - Used for single color or monochrome displays but
reverses black and white when plotting. May be
used for backlit LCD displays, at night.
C - Used for color displays, especially EGA or VGA
monitors. Star magnitudes are both color coded
and size coded.
Horizontal Screen Size: Enter the horizontal dimension of the
displayed area of the screen.
Vertical Screen Size: Enter the vertical dimension of the
displayed area of the screen.
----------------------------------------------------------------- -----------------------------------------------------------------
Note: These dimensions are not the screen size since the commonly
quoted screen size (i.e. 14" monitor) is a diagonal, corner to
corner measurement of the screen. The horizontal and vertical
dimensions can be measured from the double line box displayed on
the screen during execution since it is plotted at the display
size limits.
----------------------------------------------------------------- -----------------------------------------------------------------
Printer Type :
1 - For Epson MX/FX 80 type printers, IBM Graphics
printers, or printers which emulate these models,
such as the Okidata printers with Plug 'N Play (a
registered trademark of Okidata).
2 - For the Epson FX-86 and later model printers, IBM
Proprinters, or models which emulate either of
these printers.
- Page 10 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
It is important to note the impact of screen size and printer type on the
hardcopy output. In some cases, the horizontal and vertical sizes which
produce a round circle on the display will produce an ellipse on the
hardcopy output. This problem will be encountered when using a lap-top
computer with the short, wide LCD display, like that seen on the NEC,
Toshiba, and Sharp models.
To determine the sizes for hardcopy output, set both the Horizontal Size
and Vertical Size to 1 and make a Finder chart. Measure sides of the chart
and use these values for the Horizontal Size and Vertical Size. The Notes
section contains some typical values.
Once these values are determined, you may use the actual screen size to
obtain the correct sky mapping parameters. When you are happy with the
display, enter the Configuration Screen and enter the horizontal and
vertical size needed for the printed copy. The mapping parameters are held
in the other screens, so it is easy to return to the previous field screen,
re-plot the display, and then print it.
Alternatively, you can set the screen size to the nominal size required by
the printer when you begin and not worry about the elongation on the screen
display while you select the mapping parameters. The printed output will
have the proper shape.
The screen size can also be used in the Finder View for all plot types and
the Map View for the Lambert type to distort the display to meet other
needs, such as a skychart for a column in a newsletter. Increasing the
horizontal dimension will cause the chart to shrink in the Right Ascension
axis. Increasing the vertical dimension will cause the chart to shrink in
the Declination axis.
When all entries are complete, press the 'End' key to return to the Main
Screen.
4.6 FINDER VIEW SCREEN
The Finder View Screen contains the fields for specifying a Finder Chart
centered on an object or a point specified by Right Ascension and
Declination. The plotted chart will contain a circle which represents the
field of view entered for your finder scope, a smaller circle, 45' (arc
minutes) in radius, which is used in many finder scopes for polar
alignment, and cross-hairs in Right Ascension and Declination.
- Page 11 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
The Finder View Screen consists of several fields used to specify the
location, the size, and the type of objects plotted. The fields are
described below.
Viewing Center R.A.: Enter the Right Ascension for the center of
the Finder Chart. The form of entry is two digits for the hour,
a decimal point, and then two digits for the minutes. For
example: 5.30 corresponds to 5h 30m, the nominal location of the
Orion constellation.
Alternatively, the number of a Messier object can also be
entered, in the form ' Mnnn '. When using this form of entry, it
is not necessary to enter the Declination. For example, the
Andromeda Galaxy can be selected by entering ' M31 ' in the Right
Ascension field. SkyBase 2000.0 SkyChart will determine the
location of the object and insert the appropriate values for
Right Ascension and Declination.
Viewing Center Declination: Enter the Declination for the center
of the Finder Chart. The entry should be in decimal degrees and
include the minus sign ' - ' for the Southern sky.
If the Messier number has been entered into the Right Ascension
field above, an entry in this field is not required.
The next set of fields are used to specify how much of the sky is plotted
on the screen.
Finder field of view: The entry for this field is the field of
view for your finder scope, in degrees. When the chart is
plotted, the Finder field of view will be shown as a circle on
the chart. Inside the Finder circle is a circle whose radius is
45', corresponding to the polar alignment circle found in many
finder scopes. If zero (0) is entered, the circles and cross-
hairs will not be plotted.
Chart field of view: The overall size of the plotted chart, in
degrees, is entered in this field. This parameter may be larger
or smaller than the Finder field of view, entered above.
If the Chart field of view is larger than the Finder field of
view, then the plotted chart can be used to star-hop to the
desired location. If the Chart field of view is smaller, then it
has the effect of magnifying the Finder field of view. In this
case, the cross-hairs may extend past the chart limits as a
reminder that the Finder field of view extends past the plotted
chart.
Based on these entries, SkyBase 2000.0 SkyChart calculates the needed Right
Ascension and Declination limits for the plot. These limits are
automatically entered in the Map View Screen, which will be discussed
later.
- Page 12 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
The next series of entries are used to control the plotting of the chart.
SkyBase 2000.0 SkyChart has four types of plotting transformations which
can be used to plot the celestial sphere data onto a two dimensional
surface. The plot can be erect, mirror image, or inverted and grid lines
may be added, if desired.
Plot Type: Select the desired plotting transformation.
R - The Rectangular Plot Type places Right Ascension
along the x-axis and Declination along the y-axis
without any transformation. This representation
is fairly accurate for twenty (20) degrees around
the Celestial Equator. But at the poles it is
highly inaccurate, since it stretches the pole
completely across the screen. Plotting data using
this plot type is very fast.
C - The Cosine Plot Type accounts for the fact that
the distance between lines of constant Right
Ascension converge as they approach the poles.
The convergence is proportional to the cosine of
the Declination.
E - The Elliptical Plot Type maps the Celestial sphere
onto an ellipse similar to a Mollweide projection.
L - The Lambert Plot Type uses a conical
transformation to generate the plot. This type of
transform should be used above 45 degrees
Declination, and must be used near the poles.
However, it involves lots of calculation and plots
slowly.
Image Type: Enter the type of image display desired for the
plot.
N - Display a Normal image, that is, North Celestial
Pole at the top, South Celestial Pole at the
bottom, Right Ascension increasing from right to
left.
I - Display an Inverted image, that is, North
Celestial Pole at the bottom, South Celestial Pole
at the top, Right Ascension increasing from left
to right.
M - Display a Mirror image, that is, North Celestial
Pole at the top, South Celestial Pole at the
bottom, Right Ascension increasing from left to
right.
Grid Lines: Enter 'Y' for a grid lines at major axis points.
Enter 'N' for no grid lines.
- Page 13 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
The next series of fields are used to control the objects that are plotted.
Plot NGC: Enter 'Y' to plot the objects in the non-stellar
database. Enter 'N' to prevent plotting.
Plot stars: Enter 'Y' to plot the stars in the stellar database.
Enter 'N' to prevent plotting.
Magnitude Limit: Enter the largest magnitude to be plotted.
Enter '9' to plot all stars. If the database in use does not
have stars to the magnitude selected here, no additional stars
will be plotted.
When all entries are complete, press the 'End' key to start the plotting.
4.7 MAP VIEW SCREEN
The Map View Screen contains the fields for specifying a star chart which
is plotted between user specified limits of Right Ascension and
Declination. When this screen is entered the first time, default limits
are set to center a chart on the LST of local midnight. This time is shown
in the lower left corner of the screen.
When a Finder Chart has been plotted, this screen will contain the Right
Ascension and Declination limits used to plot the Finder Chart.
The Map View Screen consists of several fields which are used to specify
the location, the size, and the type of objects plotted. The fields are
described below.
Low limit of R.A.: Enter the Right Ascension for the right-hand
side of a Normal Image Map Chart. The form of entry is two
digits for the hour, a decimal point, then two digits for the
minutes. For example: 5.30 corresponds to 5h 30m.
High limit of R.A.: Enter the Right Ascension for the left-hand
side of a Normal Image Map Chart. The form of entry is two
digits for the hour, a decimal point, then two digits for the
minutes. For example: 5.30 corresponds to 5h 30m.
----------------------------------------------------------------- -----------------------------------------------------------------
If the chart crosses the 23h 59m 0h 0m boundary, enter the Low
Limit normally. For the High Limit, enter the desired value,
plus 24 hours. For example, for a chart covering the sky from
23h to 5h, the entries would be: 23.00 and 29.00, respectively.
----------------------------------------------------------------- -----------------------------------------------------------------
- Page 14 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
Low limit of Declination: Enter the Declination for the lower
boundary of Normal Image Map Chart. The entry should be in
decimal degrees and include the minus sign '-' for the Southern
sky.
High limit of Declination: Enter the Declination for the upper
boundary of a Normal Image Map Chart. The entry should be in
decimal degrees and include the minus sign '-' for the Southern
sky.
It is not necessary to account for the negative signs in deciding which is
the lower boundary and which is the upper boundary in these entries.
SkyBase 2000.0 SkyChart will take care of the problem for you. The limits
will be adjusted so that the North Celestial pole is at the top and the
South Celestial pole is at the bottom of the chart (Normal Image).
The Messier Object selection, which can be used in the Finder View Screen,
can not be used in the Map View Screen. However, if a Messier Object is
selected in the Finder View Screen and plotted, the Map View Screen will
automatically default to the Right Ascension and Declination limits used in
the Finder plot. They can then be extended or narrowed, as desired.
The next series of entries are used to control the plotting of the chart.
SkyBase 2000.0 SkyChart has four types of plotting transformations which
can be used to plot the celestial sphere data onto a two dimensional
surface. The plot can be erect, mirror image, or inverted and grid lines
may be added, if desired.
- Page 15 -
(V 4.6)
SkyBase 2000.0 SkyChart User's Manual
Plot Type: Select the desired plotting transformation.
R - The Rectangular Plot Type places Right Ascension
along the x-axis and Declination along the y-axis
without any transformation. This representation
is fairly accurate for twenty (20) degrees around
the Celestial Equator. But at the poles it is
highly inaccurate, since it stretches the pole
completely across the screen. Plotting data using
this plot type is very fast.
C - The Cosine Plot Type accounts for the fact that
the distance between lines of constant Right
Ascension converge as they approach the poles.
The convergence is proportional to the cosine of
the Declination.
E - The Elliptical Plot Type maps the Celestial sphere
onto an ellipse similar to a Mollweide projection.
L - The Lambert Plot Type uses a conical
transformation to generate the plot. This type of
transform should be used above 45 degrees,
Declination. However, it involves lots of
calculation and plots slowly.
Image Type: Enter the type of image display desired for the
plot.
N - Display a Normal image, that is, North Celestial
Pole at the top, South Celestial Pole at the
bottom, Right Ascension increasing from right to
left.
I - Display an Inverted image, that is, North
Celestial Pole at the bottom, South Celestial Pole
at the top, Right Ascension increasing from left
to right.
M - Display a Mirror image, that is, North Celestial
Pole at the top, South Celestial Pole at the
bottom, Right Ascension increasing from left to
right.
Grid Lines: Enter 'Y' for a grid lines at major axis points.
Enter 'N' for no grid lines.
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The next series of fields are used to control the objects that are plotted.
Plot NGC: Enter 'Y' to plot the objects in the non-stellar
database. Enter 'N' to prevent plotting.
Plot stars: Enter 'Y' to plot the stars in the stellar database.
Enter 'N' to prevent plotting.
Magnitude Limit: Enter the largest magnitude to be plotted.
Enter '9' to plot all stars. If the database in use does not
have stars to the magnitude selected here, no additional stars
will be plotted.
Uniform star size: Enter 'Y' if the stars should be plotted with
their size determined by magnitude. Enter 'N' if they are to
plotted the same size. When 'N' is selected, the stars will be
plotted at their minimum size to reduce the overlap in the chart.
When all entries are complete, press the 'End' key to start the plotting.
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5. PLOT DISPLAY
Once all parameters are entered into either the Chart or Finder View Screen
and the 'End' key pressed, the plotting begins. The grid boundaries are
plotted first, followed by the stars and non-stellar objects. The plotting
may be terminated at any time by pressing the 'Esc' key.
Both stellar and non-stellar objects are plotted. The stars are plotted as
circles which are then filled. In some cases, two stars will be plotted on
top of each other and the larger circle will not be filled completely.
This is a minor quirk in the screen display routines which has not yet been
circumvented for CGA displays. Since EGA and VGA displays use color as
well as size, this effect will not be seen. In that case, two different
colored stars are plotted.
It will also be noted, that objects which are plotted close to the chart
boundaries will extend past the limits of the chart. This is not a problem
and represents common practice for star charts.
The Map View display is sized to fit all of the available screen area. In
this case, the relation: "One hour of Right Ascension equals fifteen
degrees of Declination at the equator" does not hold true. However, the
Finder View is scaled properly in both Right Ascension and Declination and
the "one hour equals fifteen degrees" relationship is maintained.
When the plotting is complete, a message is displayed at the bottom of the
screen. If the 'Enter' key is pressed, the program returns to the previous
screen.
If the 'P' key is pressed, then a hardcopy of the screen is printed. This
process takes longer than the usual print screen operation since SkyBase
2000.0 SkyChart prints the screen in the portrait mode and expands the
vertical lines to correct for the 8.5 by 11 inch paper aspect ratio.
Pressing the 'Esc' key will stop the printing.
When a mouse is present, an additional option is possible. A pointer is
displayed which can be positioned with the mouse. Left to right movement
of the mouse moves the pointer in Right Ascension. Up and down movement
moves the pointer in Declination. The current pointer location is
displayed in the lower left corner of the screen.
It is important to note that the mouse pointer movement is affected by the
transformation selected. For example, if the display is a Lambert plot
about the celestial pole, then left-right motion for Right Acension results
in a rotation about the pole and up-down motion for Declination becomes
radial motion from the pole.
Once a new chart center is selected, pressing the left button will replot
the diagram, using the parameters set previously. If the original plot was
a Map View, then the new plot will be a Finder View plotted at the selected
center. If the plot was a Finder View, a new Finder View, centered on the
new position, will be plotted. The display limits are updated
automatically to the new center. Pressing the right button will return the
program to the Main Screen.
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6. NOTES
6.1 BUGS
This program has been extensively tested by some pretty tricky people, but
if you find a problem, please let me know. You can leave a message on
CompuServe: 71211, 2440 or put the US Post Office to work.
I would also like to hear your suggestions for improvements and
enhancements.
6.2 DATABASES
Several databases have been constructed for use with SkyBase 2000.0
SkyChart. They are listed below, along with the title of the source data
used in their construction. It is important to note that much of the
original data has been removed to achieve a practical size.
6.2.1 Star Databases
The following star databases are available.
SKYYLE: From the Yale Bright Star Catalog, 4th Edition.
Contains over 9,000 stars to magnitude 6.
File names: SKYYLE.RND, SKYYLE.NDX
This is a good catalog to use when making charts to use for
visual and binocular observations. With fewer stars, plots are
faster.
SKYSAO: From the Smithsonian Astrophysical Observatory catalog.
Contains over 45,000 stars to magnitude 8.0
File names: SKYSAO.RND, SKYSAO.NDX
6.2.2 Non-Stellar Databases
The following non-stellar object databases are available.
SKYMESS: The Messier objects.
File names: SKYMESS.RND, SKYMESS,NDX
SKYNGC: Over 400 "Best" NGC objects from a public domain file
and cross-checked against SAC 5.0.
File names: SKYNGC.RND, SKYNGC.NDX
SKYSAC: From the SAC 5.0 database of nonstellar objects by the
Saguaro Astronomy Club of Phoenix, AZ. Contains over 10,000
entries.
File names: SKYSAC.RND, SKYSAC.NDX
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6.2.3 Database Accuracy
The databases used in SkyBase 2000.0 SkyChart have been obtained from
public sources and they are believed to be accurate. However, their
absolute accuracy can not be guaranteed due to the sheer number of entries.
If a discrepancy is suspected, a reference sky atlas or catalog should be
used for a cross-check.
6.2.4 Printer Aspect Ratios
Unfortunately, the print head spacings and vertical paper movements do not
match the aspect ratios of the various screen displays. Thus, it is
necessary to change the horizontal and vertical sizes in the Configuration
Screen to produce a correct hardcopy. The following table contains values
which I have determined for several configurations. These should provide a
good starting point.
Printer Type 1 2
H V H V
CGA Monitor 4.56 4.78 6.08 4.78
EGA Monitor 4.43 4.07 5.92 4.07
As mentioned previously, if you want to determine your own values, set the
Horizontal and Vertical sizes to 1 and make a Finder View plot. Measure
the sides of the chart along the axis borders and use these values for the
Horizontal and Vertical sizes.
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