Classic Computer Magazine Archive COMPUTE! ISSUE 146 / NOVEMBER 1992 / PAGE A4

Final frontiers. (Distant Suns 4.1 and Voyager astronomical software) (Software Review) (Evaluation)
by Robert Du Gaue

>From the dawn of time, mankind has gazed upward in awe at the stars. Those twinkling objects are responsible for the inspiration of poets, lovers, mathematicians, physicists, and many others.

Long before Nicolaus Copernicus (1473--1543) theorized that it was the earth that revolved around the sun, rather than the sun around the earth, the heavens were entwined in myth and controversy. In 1609, Galileo Galilei (1564-1642) heard about one of the first telescopes constructed by Dutch spectacle maker Hans Lippershey. Galileo then assembled one himself and began the astronomy revolution. He eventually went on to build a telescope that could make distant objects appear 30 times nearer.

Today's telescopes are considerably more powerful and advanced, and computers now play a large role in our ongoing observation of the heavens. By taking advantage of inexpensive, full-featured planetarium software, amateur astronomers and enthusiasts are beginning to use their computers as home observatories. These programs let you view the stars on the cloudiest nights. The Amiga is fortunate to have two superb astronomy programs: Virtual Reality Laboratories' Distant Suns 4.1 and Carina Software's Voyager. Each product is excellent in a number of ways, and competition between them promises to bring more control of the night skies to Amiga astronomers.

Distant Suns 4.1

Distant Suns 4.1 has evolved from one of the first astronomy programs for the Amiga, Galileo. After Galileo's distributors went out of business, an updated version of the program was released by Virtual Reality Labs. The latest version ships with a database of over 2000 deep sky objects and about 4200 stars from NASA's SkyMap star catalog, to about the sixth magnitude. (Magnitudes classify a star or deep sky object's brightness; the larger the magnitude number, the fainter the object.) Given a clear, smog-free sky, the naked eye can fathom objects as faint as magnitude 6.0; with binoculars, objects to about the tenth magnitude can be discerned. Polaris, the North Star, shines at an approximate brightness of magnitude 2.0.

Distant Suns displays stars onscreen in varying shades and sizes, depending on their magnitudes. For instance, Arcturus, the fourth brightest star in the sky, appears quite large among its seventh-magnitude neighbors. Distant Suns shines when it comes to providing information regarding stars. A star's data window displays facts such as magnitude, distance, and rise and set times. You also get other interesting information, such as stellar and spectral class, b-v magnitude, and whether it has a companion. Informative history and science lessons also pop up in separate windows when you pull up information about certain stars.

While Distant Suns' display method works well, I did find one small problem with the way it displays planets. Drawn much like stars, with smaller and fainter dots representing objects of lesser brightness, dimmer planets such as Pluto and Uranus are difficult to find. Turning on planet labels will help, but it's still difficult to pinpoint the location of a planet unless you use the menus to center on the planet or narrow your field of view.

Deep sky objects such as galaxies, nebulae, and clusters appear as large symbols against the background of stars. Their sizes are the same, regardless of their magnitudes. Pulling up an information window on a deep sky object displays information similar to the star data. In addition, Distant Suns will display full-color photos of planets and certain deep sky objects, if they have an associated file image. The basic package ships with a meager set of three sample images. Virtual Reality Labs does offer the Space Visions collection of 246 high-resolution images, almost 20MB of data. Most of the Space Visions images are devoted to planets and various shuttle missions. Although these pictures are interesting, some seem out of place or redundant; only about 20 percent really relate to deep sky observation. More appropriate objects are needed to realize the power of this wonderful feature. If you want to forego purchasing the data disks, you can add your own pictures. I did this with the aid of my DCTV digitizer and collection of astronomy magazines.

You can control Distant Suns with macros, using its ARexx port. Conceivably, it should be fairly easy to develop a controller to point a remote-controlled telescope using Distant Suns and its ARexx interface. Most telescopes with this capability, however, tend to be quite expensive. A more common use would be to set up scripts to center on objects, change your location, or configure viewing modes. You could also use AmigaVision or another authoring tool that supports ARexx to build a custom interface to Distant Suns.

One feature that sets Distant Suns apart from Voyager is its animation capability. Simply set your start position and time rate, then put Distant Suns in motion. Each time change creates a new frame, which is stored in a standard Anim-format file. It's easy to create complex animations using ARexx scripts to control Distant Suns. A sample ARexx script creates a 2MB animation of Halley's comet passing through the solar system. One note of caution: The more data that changes between each frame, the larger the Anim file. It doesn't take much for an animation to fill up your precious disk space. To avoid wasted time and a full disk, animate a few frames first, and then calculate an anticipated file size.

Distant Suns' manual contains many historical facts, helpful definitions, and basic concepts of astronomy. It also has a section for the first-time telescope buyer that will help you choose an adequate instrument for your needs. Appendices contain useful data about Messier objects, NGC data, planetary facts, and meteor showers. Several illustrations and interesting pictures of old Grandville woodcuts provide added enjoyment. While the manual is adequate, it lacks screen shots.


Voyager was born on the Macintosh, but don't think the Amiga version is a simple port; it's substantially different from its Macintosh ancestor. Using the Yale Bright Star Catalog, Voyager has a database of over 9000 stars and 1200 deep sky objects. Although Voyager has more stars than Distant Suns, it has just over half as many deep sky objects--which are of more interest than stars and more likely to require assistance to locate.

Voyager's user interface is more comfortable than Distant Suns', even if it doesn't follow Amiga user interface guidelines as closely. Its layout and design will allow you to perform tasks with little effort. Placed in logical locations, gadgets and controls barely obscure the star field. When you request object information, the program takes measures to avoid covering the object with the information box. The mouse can center objects, identify them, and zoom in. Voyager's interface will have you performing even complex operations in a minimal amount of time. Voyager 1.1 adds the ability to bring up IFF pictures of various objects when they're clicked, as in Distant Suns.

Voyager displays stars in four different modes. Star Atlas shows the sky much as a conventional atlas does, while the Local Horizon view will display stars as seen from your location. The Celestial Sphere view displays an entire hemisphere of the sky at one time, and Full Sky view widens the field of view to 360 degrees. Both of these views introduce considerable distortion but are useful for tracking planets and for showing the distribution of objects within the universe. As in Distant Suns, stars are displayed in varying sizes and shades according to their magnitudes. Sky color is adjustable to black, blue, gray, light blue, white (for printing), or a dynamic mix of colors correlated with the time to simulate daylight, twilight, or evening.

Deep sky objects and planets are easy to spot. Each type of deep sky object has a symbol associated with it. For instance, a starburst is a globular cluster, a diamond is a dark nebula, and an S-shape is a spiral galaxy. You can toggle any of the ten deep sky object types on and off. Planets appear as dots of color but can also be shown as unique symbols, and, unlike the planets in Distant Suns, appear regardless of their magnitudes. Finding Pluto is just as easy as finding Mars or Jupiter. Four special symbols depict the earth's shadow, comets, asteroids, and spacecraft. One minor nuisance is the inability to print the information boxes for objects, a function which Distant Suns allows and one that's most helpful when planning an evening's viewing at a remote site away from your computer.

You'll find Voyager loaded with plenty of extras. Voyager's Day-Night map presents a map of the earth laid flat, showing daylight and darkness around the world at your chosen time. Different time cycles allow you to explore the shifting of dark and light caused by the sun's movement from above to below the horizon throughout the year. A Galilean Moon option depicts the orbits of the four brightest moons of Jupiter (lo, Europa, Ganymede, and Callisto) over a period of a few days. A small window displays the moons as seen through a telescope, to help you to identify them when using your own telescope.

In an option similar to Distant Suns' What's Up option, Voyager provides a dynamic table of current planet positions and marks whether a planet is above or below the horizon. Another noteworthy feature is Voyager's ability to accurately search for and find eclipses, conjunctions, and occultations. To find solar eclipses, simply select the sun and moon as your target objects and instruct Voyager to search for the dates and times when these objects are less than 1/2 degree apart. In just a few seconds, Voyager will list all eclipses occurring at your location within a specified time period.

Voyager's manual contains an adequate mix of screen shots and basic concepts. It includes examples and exercises which aid you with Voyager's controls. Views, menus, and functions are all explained in detail. A small technical section is included in case you have problems, and you're encouraged to contact Carina Software for technical support.

The Sky's the Limit

Both Distant Suns and Voyager have several optional extended data disk packages. Distant Suns has two disk sets which will increase your database to 10,000 or 20,000 stars. Virtual Reality Labs also offers individual data sets for specific areas of the sky to the tenth magnitude; that complete set includes over 20MB of information.

Besides the hugh Space Visions collection, a smaller library of 213 black-and-white photos of deep sky objects is also available. Voyager offers three sets of extended databases, each set designed to increase the star field by about one magnitude. Data Set One contains stars from magnitude 6.5 to magnitude 7.5, about 17,000 additional stars; another 3000 deep sky objects also are included in this bundle. Data Set Two delivers an additional 62,000 stars to magnitude 8.5. The last collection increases the field resolution to magnitude 9.5, giving you over 250,000 stars if you add all three sets.

Universal Acclaim

Both programs require at least 1MB of memory to run comfortably. Optional data disks demand more memory. A hard drive is recommended, especially if you add the data disks. Both Distant Suns and Voyager cry out for an accelerated Amiga and math coprocessor.

I found technical support excellent with both companies, and I learned that they take customer suggestions seriously. Many of the features found in Distant Suns and Voyager are the direct results of customer input. Both titles are excellent choices for educators, students, and home astronomers. In fact, since they are equally inexpensive, I'd suggest that serious astronomy buffs use them both. You'll find that they complement each other, putting at your fingertips the power which was once available only with expensive telescope installations. More casual users can't go wrong with either program; take a close look at each program's features and decide which one is best for you. Whichever you choose, you'll find many hours of educational fun exploring the infinite heavens.