Astronomy Software: TheSky for Macintosh

2001 – This is the third in a series of reviews of planetarium software for the Macintosh, with emphasis on use in schools. Planetarium software, at a minimum, simulates the appearance of the night sky given certain parameters such as the date, time, and observer location.

System Requirements

To install and run TheSky, you should have the following:

  • A PowerPC Mac
  • Mac OS 7.6 or later (Mac OS 8.5 or later is recommended)
  • 16 MB of free RAM
  • 45 MB of free disk space
  • A display with 256 or more colors


TheSky is not, perhaps, the best-selling planetarium program for the Mac. However, as Mac users know, the most popular products are not necessarily the best. The Sky is a real workhorse program for serious amateur astronomers and has much to offer the beginner as well. The nice folks at Software Bisque kindly provided a review copy of the software, promptly delivered after a single emailed request.


This is from the publisher’s web site:

TheSky is available in three different “Levels” called Level II, Level III, and Level IV. Levels II and III contain databases and features broad enough to keep most armchair astronomers satisfied for a lifetime. TheSky Level IV for Windows has even more data, more pictures and more capabilities. Order your copy today for $129 (Level II or TheSky for Macintosh), $199 (Level III), or $249 (Level IV)!

Reading the software specifications here, you would think that TheSky for Macintosh is equivalent to the lowest-end version for Windows. This is not the case! TheSky for Macintosh has all the features of Level III for Windows – and it contains databases not found until you get to Level IV. However, Level IV for Windows has several features not found in the Mac version, particularly dealing with more powerful automated telescope controls, planetarium management functions, and so on.

Software Bisque has solved the dilemma facing developers wanting to support the Mac but unable to fund separate-but-equal development costs by giving the Mac user a discount (at least $70) over the equivalent Windows user (which is almost unheard of) plus adding as many features as possible with a minimum of development overhead – namely, the half-million objects provided as data files on a second CD-ROM, only available to Windows Users at essentially twice the price. If you can’t keep the versions exactly the same, this is a great way to convince your customers that you’re serious about the Mac platform.

Test Activities

Ease of Sky Navigation

TheSky opens with the usual view of the local horizon facing south that is common to planetarium software. There’s also one of those annoying Microsoft-like Tip Screens, which you can turn off if you’re a real Mac user – you want to learn the software by exploring, not by being led by the nose.

Maneuvering around the sky is straightforward. The button bar contains cardinal points (NSEW), which is something lacking in other software packages. The screen changes the user’s point of view in response to cursor arrows, just like a first-person arcade shooter, also a standard convention. After using the “grabber” tool in Starry Night, I found I missed having the equivalent function in TheSky.

The appearance of the sky in this program is more like looking at a printed star map than the real sky. Star brightnesses are indicated by different size circles, labels are made with a sans serif font, and deep sky objects are indicated with a font-like symbol for each type of object. This is not as pretty to look at, or as realistic, as Starry Night, but it makes a much more effective printed sky chart.

Mac-like Interface

TheSky uses a different convention than most other planetarium software for the Mac: It relies on dialog boxes and buttons on a button bar to make selections. The button bar images are fairly obvious to interpret if you have some background in astronomy, and passing the cursor over them will allow a popup to show the name of the button, as in most Windows-style applications. Segments of related buttons on each button bar can be moved around, but individual button placement within the segments is fixed. The button bars can be dragged around the edges of the screen and provide a floating palette when dragged to the center of the screen, which is very Mac-like.

Some of the choices for the interface reveal that the software was ported from a Windows version. For example, the Data menu contains mostly functions for selecting or editing data files, which a Mac user would expect to find under the Edit menu. The Edit menu has the required functions, but nothing specific to TheSky. Some of the dialog boxes are designed to be controlled exclusively with a mouse, such as the Find function. Presumably this is so the user can use a trackpad or extended-cable pointing device for telescope and software control without having to go to the keyboard.

Unlike RedShift, which uses tabs on dialog windows like McDonald’s uses salt on french fries, TheSky’s use of tabs is sparing and appropriate. Most dialog boxes do not have tabs at all, and options that would be tab driven are relegated to another menu item choice.

buttons in TheSkyHere’s another example of the quirky interface. Look at these time controls and guess which one makes the clock move forward continuously, like an animated movie. If you guessed the single pointing arrow, you’d be wrong; it’s the double-pointing arrow.

Now there is some logic in the choice: The double-arrow moves through time faster, like a fast-forward button, but the convention in almost every other program of this type that I’ve ever seen is that the single-arrow makes time march forward at the rate specified in another control window.

All in all, TheSky could stand some improvement in interface design, but it remains quite functional as it is.


Unfortunately, I must report that the stability of TheSky on the systems I tested was poor. The program has a tendency to crash hard, either freezing the operating system or just disappearing without warning. On the copy I am using right now, for example, on a 300 MHz Beige Power Mac G3 with 192 MB of RAM and plenty of hard drive space, TheSky crashes repeatedly with a type 2 error each time I select the “Filters” function. I increased the memory partition substantially to no effect.

Last month, while doing a presentation on planetarium software for our local astronomy club, the Mt. Diablo Astronomical Society, TheSky crashed repeatedly on a brand-new, never before used iBook. I later found out that the crash happened because I forgot to put the CD back in the drive and had not run a full install (thanks, James) but the program did not prompt me with a “please insert the disk” either. I had tested the software earlier, but always with the CD in the drive. Under those conditions it seemed to work fine for the short time I had the iBook on loan. Fortunately I had a copy of Starry Night installed on the same machine, which performed without a hitch for the remainder of the presentation.

I’ve also experienced unexpected crashes on a new 500 MHz iMac and a 233 MHz Beige Power Mac G3 tower running Mac OS 8.1. The other machines were running OS 9.1. Restarting with everything but the base extensions disabled did not help, at least on my Beige G3 desktop at home. It seems most stable on the iMac, and I’ve since deleted the test copies from all the other machines out of respect for the license.

I went to the support Web page for the product and located an updater, which, when applied, eliminated some of the crashes described above. However, the program froze twice switching to Chart mode. After restarting the computer, it allowed me to enter Chart mode and look at it. It also froze once while I was looking at the popup labels on the button bar to learn the button functions. On another occasion it froze when opening the Help window. I haven’t yet had the time to eliminate all the things that might be causing the problems, although I did increase the memory allocation and trim down my extensions folder a bit.

Appearance of Objects

As stated earlier, TheSky is not necessarily about providing beautiful pictures; it bills itself more as a tool for amateur astronomers seeking technical information. For example, zooming in on most deep sky objects reveals an outline similar to what is seen in Wil Tirion’s star atlases.

tiny camera iconClicking on an object does not necessarily bring up a picture on the first try, either; you either have to hit the minuscule camera icon that is literally this big (right) or click the multimedia tab on the Info window that pops up. (Once chosen, the multimedia tab stays on top for subsequent searches.)

Diehard amateur astronomers will tell you this is because you’re supposed to be looking at the real thing with your own eyes, not browsing through some (lazy-armchair-astronomer’s) online picture book. That’s as may be, but when I zoom in on an object, I like to see an image by default instead of a finder-chart view – or at least have a choice about it.

magnified view of M21 and M20

Magnified view of M21 (upper left) and M20 (The Trifid Nebula, lower right) from TheSky. Note the cartoon-like quality of the Trifid illustration and the outline that indicates the location of M21. M21 is an open star cluster and looks pretty much like this illustration.

view of M8

This is a view of M8, which is an extended emission nebula. The cloudy appearance of the nebula is lost in this view. The red circles represent the targeting circles of a Telrad, a popular telescope pointing aid.

Clicking on the tiny camera icon at the center of these objects brings up a full color illustration of the object. The information window for each object has position information, descriptions in words, and links to photographs – sometimes quite a few photographs. The amount of material accessible with TheSky’s internal databases is easily greater than for any of the other programs I have examined.

One more picture: To compare to the other packages, look at this image of Jupiter drawn by TheSky:

Jupiter as shown in TheSky

Compared to the images in RedShift and Starry Night, this is essentially a cartoon. However, when you double click on Jupiter or use the Find feature to locate it – and then click on Multimedia, you get actual space probe images in an extensive list like this:

Object Information for Jupiter

The list of images for objects in TheSky is extensive and contains both beautiful and technical pictures.

Draw an Analemma

analemma displayed in TheSkyAn analemma shows the sun’s apparent change in position when viewed at the same time of day over the course of a year. TheSky has the ability to draw an analemma (this one shows the motion of the sun at one-week intervals), but I could find no way to label the sun positions with dates, which would be a nice touch for teaching about the seasons. This function is a bit hard to find; you have to first set up the tracking options from the Time Skip submenu of the Tools menu in the menu bar; then you have to go back again to actually turn tracking on. (There are shortcut buttons for these functions too, if you can find them.)

Define Horizon

TheSky lets you define your local horizon, drawing an outline of the horizon with an easy-to-use tool that pastes your local obstructions in front of the sky. Starry Night does the same thing, but it also includes sprites for trees and other objects, which you can move around and observe shadows being cast from during daylight simulations. Again, TheSky is catering to the kind of user who would say, “Who needs that fluff? I want to look at the sky, not a simulated tree.”

Show Jupiter’s Moons

Jupiter’s moons are easily observed with TheSky and can be observed rotating around the planet as with all the other software I’ve reviewed.

As with the others, there is no feature available for generating position vs. time charts for Jupiter’s moons (as shown in Sky and Telescope and Astronomy magazines) directly.

Measure Angular Separation

An important tool for astronomy educators is the ability to measure the angular separation between objects (say, between the moon and the horizon, or between the planet Venus and the Sun). A tool is provided for this function in TheSky. It reports the angular separation between the last two selected objects.

Adding Objects to the Database

There is a built-in dialog window for adding data to the user database. All the necessary fields to define objects are included.

Remote Control of Telescopes

There is no question that TheSky is the most versatile telescope control program for the Mac, although it is not the only contender. Here is a partial list of the telescopes TheSky can control:

  • Celestron Ultima 2000™
  • Celestron Nexstar™ 5 and 8
  • Celestron Compustar
  • Meade LX200™ Series
  • Meade Autostar™
  • Software Bisque Paramount GT-1100S™
  • Astro-Physics GTO German Equatorial Mount
  • Vixen SkySensor (emulates LX200)
  • Losmandy Gemini (emulates LX200)
  • DFM Engineering Telescopes
  • Any Telescope supporting the Astronomy Command Language (ACL)
  • Meridian Systems ArcImage
  • Telescope Applications Programming Interface (TeleAPI) for third party-custom telescope support
  • Quadrant Systems Coordinate III
  • Autoscope

With this feature users can locate an object in the sky and tell the telescope to slew (move) to the object. If your telescope has digital setting circles (sensors) and is not motorized, you can have the software track with the telescope, enabling comfortable and easy pointing toward unfamiliar objects. I will report my experiences in connecting a Mac to a telescope via TheSky in a future article.

One nice feature about the software is that you can connect to a simulated telescope to see what controlling one is like.


TheSky doesn’t include drawings of the constellations other than the traditional stick figure interpretations. Boundaries between official constellations can be toggled on and off. Otherwise display of the constellation pictures is left as an exercise for the user’s imagination.


As far as I can find, TheSky provides many more options for sorting and exporting data than Starry Night, but both it and Starry Night apparently cannot generate data for events over time. This is an important educational tool for generating graphs and charts of motion over time, and it would be nice if it were included. For example, you can generate a telescope observing run chart, which lists the coordinates of objects the telescope you have connected is scheduled to acquire – it’ll even show those objects connected by red lines – but there’s no provision for generating a table of ephemerides such as RedShift 2.0 used to do.

Sky Charts

TheSky’s Sky Charts are one of its best features. These are clearly meant to be printed for use at a telescope. The default is white background with black stars, just as is expected in a field copy of a star atlas. Even better, the program can operate in Chart Mode, where everything is reversed on the screen so you can preview what you will print. The style of printing is blocky and chunky, but it should be legible and useful for finding objects even if printed on a dot matrix printer. Again, these folks have sacrificed beauty for utility; water-based inkjet maps are likely to run and wrinkle in a cold, damp environment outside with a telescope late at night.

Other Features

A nice feature is the moon calendar function, which tells the phase of the moon over the course of a month with a calendar layout. This tells the serious amateur when it is time to observe. (These people consider the moon an annoyance to be avoided.)

A Night Vision mode is more finely controllable than Starry Night’s version, so you can prevent your computer screen from blinding everyone at the star party. This turns your entire screen a dim shade of red.

A computer time window shows the local sidereal time, which is the time based on the stars rather than the sun. Astronomers use local sidereal time and the coordinates of an object to estimate when it will rise and be highest in the sky. I haven’t seen local sidereal time displayed in a program such as this until now.


In my previous article in this series, reviewing Starry Night, I said:

From first glances, however, competitor TheSky is the Sky and Telescope of planetarium software where Starry Night is the Astronomy.

I feel even more strongly about that now. Starry Night is prettier, better animated, refreshes the screen faster, and is easier to use. TheSky is more powerful, has access to far more data catalogs, does more sorts of functions, and is directed more at the serious amateur than it is at the armchair astronomer or the educator.

The same is true, I think, for the two most popular astronomy magazines. Sky and Telescope is packed with technical information and generally avoids white space where a data table or sidebar explaining Universal Time will fit in. Astronomy is targeted at the more casual reader who may not want the same level of technical detail. Both magazines have their place and are well suited to their audiences. The same is true for these programs.

I would recommend this software as an exciting purchase for serious amateur astronomers wishing to push the envelope of what their Mac and their telescope can do. Software Bisque has certainly treated the Mac user with respect, given that they cannot keep both Mac and Windows versions identical due to development costs.

However, I cannot recommend the software for beginners or educators due to its rather clunky interface and tendency to crash. If you have the software, apply the update, because it does help.

TheSky is published by Software Bisque, 912 12th Street, Golden, Colorado 80401-1114. Sales: (800) 843-7599. Web:

Correction: In my review of Starry Night, I said Starry Night was a relative newcomer to the Mac platform. Several readers, including Pisces X and Alan Sill, pointed out the application was more than 10 years old and was originally a Mac-only app. I must have been off in my own little universe to have missed it!

Update: Since I wrote this review, an updated version of TheSky has come out that addressed some of the points I made in this review plus many other enhancements, such as additional models of telescopes available for control, some user interface tweaks, and additional object databases. The program has also been “carbonized” for Classic Mode use in Mac OS X and tested on “all the latest Macintosh models.” If you have the program, check out the extensive notes at and download the free update.

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