Subject: REVIEW: Distant Suns 4.0
From: Steve Koren <[email-masked]>
Newsgroups: comp.sys.amiga.reviews

This is a review of Distant Suns 4.0, an excellent astronomy program for
Amiga computers.  Distant Suns is powerful, expandable, and well worth the
price.  It has a few usability flaws but nothing which seriously detracts
from the overall quality.

I had previously owned 3.0, and took advantage of the VRLI offer to upgrade
to version 4.0.  This upgrade was $30.  The list price if you are not
upgrading is $99 US, although it is on sale from VRLI for $59.95 through
October 1991.

Distant Suns is available from VRLI (Virtual Reality Labs Inc).

    Virtual Reality Labs
    2341 Ganador Court
    San Luis Obispo CA 93401-9826

Version 4.0 runs on any suitably equipped Amiga from a 500 to a 3000,
under 1.3 or 2.0, and requires 1 mb or more of memory (the more the
better).  A hard disk is recommended.  Some of the expansion data sets
require larger machines.  68030/882 versions are available for
machines with faster processors, and this makes the program more
enjoyable due to the faster speed. 

Distant Suns: What Is It?
------------------------

Distant Suns is an astronomy program which, among other things, can
act as a planetarium.  It will also do many things a planetarium
cannot do.  The program started life under the name "Galileo", but
there have been so many improvements since then that it can no longer
be considered to be the same program. 

Distant Suns 4.0 (hereafter referred to as DS4) comes with a database
of 4200 stars, many solar system objects, and 2000 "deep sky objects"
such as nebula, globular clusters, etc.  It can display these objects
on the screen in the same manner as a planetarium.  You see a view of
the sky on the screen, covering a field of view which is adjustable
from 1 degree to 180 degrees.  Exactly what you see can be customized
in many ways, but the default is to look at the stars and planets.
Since at large angles there is distortion induced by mapping a
spherical space onto a flat screen, you typically pick fields of view
around 30 to 50 degrees. 

You can move your field of view around the sky by several methods.
There is a small control window with arrow keys.  You may click the
mouse cursor on an area of sky to center in the screen.  You may also
search for any given object by name.  (Ie, center the sky on Saturn,
or M-78). 

In Planetarium mode, DS4 displays a location independent view of the
sky.  However, if you tell it your location on the earth and your time
zone, it will save off this information in a file, and from there on it
will be able to display the sky as it looks from your location and at
the current time.  (It gets the time from your computer's internal
clock).  In fact, the program is even able to store customized
horizons which match the actual horizon where you live. 

You can now set the program to "real time" mode, which will cause the
displayed sky to rotate in time with the sky overhead.  You can also
greatly speed up this rotation, anywhere from real time through 100 years
of simulated time per 30 seconds of real time.

DS4 can superimpose a large variety of data on the sky.  For just a
few examples, it can display planet names, constellation names and/or
outlines, and even things like the magnitude, spectral class, or
distance of every star displayed in the sky for which the data is
known.

Identifying Objects
-------------------

DS4 has a neat feature whereby data may be displayed for almost any object
in the sky.  For example, I have an expansion data disk of 20000 stars
which I bought with my program.  I can click the mouse cursor on any one
of these, and I can find out the name of the star (if it has one), the
magnitude, the position, rise and set times, the spectral class, catalog
number, whether it is a binary star, and if so the magnitude of its
companion, their orbit period, the distance from Earth, and a whole host
of other details.

Even more information is provided for DSO (Deep Sky Objects) and planets.
For example, I can click on M-31 and see not only the above information,
but a paragraph describing the nebula, galaxy, or cluster, and a small
image of it.  I can then choose to view a full screen image of the object
if I wish.  This capability is only limited by hard disk space.  All of
the DSO have textual descriptions, often including information on what
size of telescope is needed for viewing the object ("...in a 6 inch
instrument one can make out the dark bands between the clouds, but an 8
inch scope is recommended to resolve more detail").  Many DSO have images
as well.

Off-Planet Views
----------------

Distant Suns can also generate views from any location within 800 AU
of the sun.  Further, it has the ability to generate standard IFF anim
files.  The first day I had the program I created an IFF anim which
was taken from the viewpoint of Halley's Comet, covering the years 1984
to 1988.  The resulting animation was spectacular.  It is fascinating
to watch planet motion from the viewpoint of Halley as it zooms around
the sun and back out again.  Many options are available, such as
displaying the ecliptic plane, distances of planets above the
ecliptic, etc.  This ability is one of the most visually fascinating
provided by the program.  Any animations created with DS4 may be
freely distributed.  Animations with a fixed viewpoint can be a great
tool for investigating solar system object interactions, and with a
fixed viewpoint the resulting anim file is quite small.  I generated a
300 frame high-res overscan anim file which took less than 250000
bytes of disk space.  In a 2 meg animation, then, you could store
about 2400 such frames.  Of course, animations with a moving viewpoint
are much larger.  My Halley animation was 3 megabytes.  Animations are
generated directly to disk, so you do not need to have enough memory
to store the animation and the program at once. 

User Expansion
--------------

DS4 can be greatly expanded in many ways.  First, you can currently
purchase up to a 20000 star catalog for $20 US, with a 250000 star catalog
coming soon from VRLI.  You can also purchase other sets of DSO.  The
program comes with several thousand deep sky objects from the Messier and
NGC catalogs, but you can purchase many more.  VRLI also sells sets of
image disks which contain images of these deep sky objects.

The program can also be easily expanded by users.  For a few examples, you
can add your own object images to the database.  You can also add custom
objects, either within the solar system, or outside.  Perhaps, for
example, you are interested in tracking a small asteroid which the program
doesn't know about.  You can define this orbit to DS4, and thereafter, it
will be able to display and track it for you.  You may also add, for
example, a custom catalog of pulsars from an outside source.  VRLI claims
in a recent newsletter that they are looking into CD ROMS which could store
high res images for every DSO in the database.  Personally, I am looking
at the possibility of generating an animation of the Voyager I and II
journeys from earth out of the solar system.

Improvements from DS 3.0
------------------------

DS4 is substantially different than 3.0.  The general "look and feel" of
the program is now much more professional.  For example, you can now
choose to run the program in high res/overscan mode in addition to medium
resolution.  The general layout is more logical, and "thoughtful" features
have been added (such as the ability to use a dim red palette to avoid
ruining night vision).

DS4 supports external script control via AREXX.  The possibility
exists, as mentioned in the manual, for DS4 to control a real
telescope through AREXX, given the appropriate telescope control
hardware.  You could set up a system where you could click the mouse
cursor on a given nebula, and have DS move the telescope to that point
in the sky.  This is probably beyond the range of most hobbyist, but
a small university or high school observatory could make good use of
such a system. 

Thing which could use improvement
---------------------------------

As always, DS4 isn't perfect.  There are a few things I have wished could
be improved:

   - The internal IFF viewer, while it works, isn't the best.  For
     example, if a given object has multiple images, the must all be in
     the same resolution.  It also won't let you scroll around a bigger
     bitmap than your screen.  Instead of building this into the internal
     IFF viewer, it would be better to provide the ability to use an
     external picture viewer if one was available, with any command line
     options needed.  Everyone has a favorite picture viewer, and its
     not practical to make the program try to do everything.

   - This is just a nit, but it would be nice if the application was
     multithreaded (as is, for example, NComm 1.92).  Currently, if the
     "real time" screen rotation is on, the program will lock up for 5
     seconds or so out of each 30 while it recomputes new star positions.
     This prevents you from doing other things such as interacting with
     various dialogs, etc.  If different parts of the program ran as their
     own task, this problem would be prevented.  However, this isn't a
     major problem; you can just turn off real time mode, or wait for 5
     seconds.

   - The program seems to take quite a bit of CPU time even when it
     does not seem to be doing anything.  (It seems to "use" about 50% of
     the CPU when idle).  It would be nice if either the program took less
     CPU time when idle, or if there was some sort of pause feature which
     froze it.
 
   - DS4 takes various workbench "tooltype" options to configure
     itself upon invocation.  I wish some of these were provided for shell
     users also.  (They may very well be there, but I can't find them in
     the documentation).

   - Multiple horizon configurations would be nice.  It appears as if
     this possibility was planned into the program and may appear in the
     future.  This way, once could store configuration files for various
     observing locations, and be able to easily detect whether a given
     object was above the horizon from a given places.  For example, I
     would like to store one configuration where the mountains to the west
     of my house obstruct low objects to the west, and another
     configuration taken far enough east that the obstructions are low.

Conclusions
-----------

DS4 is a great astronomy program, probably one of the best available for
any personal computer.  It has a great many features and abilities which I
haven't touched on in this review.  It is a good value for the price, and
a worthwhile program for anyone interested in astronomy as a hobby.  I
could also be a fantastic tool for education; every student could have his
or her own private planetarium to interact with.  Astronomer hobbyists can
use Distant Suns to view a date in the future, easily finding interesting
objects to observe in a real telescope on that date, and even printing out
that section of the sky to assist in finding the objects.  The addition of
expansion data makes the program more valuable, and this data is available
from VRLI at a reasonable price.

Rating: 9 on a scale of 1 (worst) to 10 (best).

  - steve ([email-masked])
          303-226-4985