Reed D. Meyer: Downloadable Files
Downloadable Files

Computer Programs

Airmass calculator for astronomy

The term “airmass” is often used when discussing atmospheric effects on astronomical observations. It is simply the column density of the atmosphere along the line of sight of an observation, divided by the column density towards the zenith, so that the airmass is 1 at the zenith and grows towards the horizon. The program airmass.c [65 kB] computes the airmass with more precision than the approximations astronomers typically use. In fact, to quote the program itself, it “was developed to find out to just what degree the standard approximate formulas for airmass are inaccurate.”

The top of the source code contains a very extensive comments section, including a discussion of the background of the problem, a derivation of the physical formulae involved, and an analysis of all the assumptions that went into the final algorithm. The most significant assumptions are that the atmosphere is spherically symmetric and that its temperature profile conforms to the “U.S. Standard Atmosphere.” Even these assumptions are likely to have only a small effect on the calculations. The program computes the dry air column density and the airmass, and optionally compares its airmass estimate to those from the approximate formulae; it also can crudely estimate the water vapor column density. The input parameters are the zenith angle and the wavelength of the observation; the local temperature, pressure, and relative humidity; the altitude, latitude, and longitude of the observatory; and the day of the year. The zenith angle is the only significant parameter, and the program will assume default values for the other parameters if they are not specified.

The file airmass.c contains the complete source code, which is easily compiled into a standalone program with gcc on UNIX-like operating systems. Full permission is granted to copy and distribute the program, as long as the source code is left completely intact and unmodified.


CBM2ASC converts a Commodore ASCII file to standard ASCII. It runs on MS-DOS or a DOS box under Windows. I have placed it in the public domain.

The Commodore 64’s “ASCII” character set is substantially different from the ASCII character set used by most machines—so different that if you try viewing, on a PC, an unconverted Commodore 64 text file, you will mostly just see garbage. CBM2ASC makes the text legible again. CBM2ASC is also fine-tuned to the conversion of two specific types of Commodore text files, selected by passing an option on the CBM2ASC command line. These specific types of files are Commodore BASIC programs, and documents written with the SpeedScript word processor.

CBM2ASC cannot convert many of the specialized Commodore ASCII codes, notably graphics characters which have no equivalent in the PC’s ASCII character set. But it does convert the standard characters (the symbols typically found on typewriter keyboards). The “Commodore BASIC” option converts just about everything except graphics characters within BASIC strings, and the “SpeedScript” option converts an entire SpeedScript file except for escape codes, which affect text formatting, not content.

The usual procedure is to first copy the raw floppy disk image from the Commodore 64 disk drive to the PC using an X1541 cable and associated software (at least one enterprise appears to sell these cables, but I assembled my own cable so I have not interacted with them). Once the raw disk image is sitting on the PC, the next step is to use a utility like D64T641 to break the disk image up into individual binary files sitting in a DOS directory. The binary file names typically end in .PRG or .SEQ, and they correspond to individual files on the original Commodore 64 disk. Finally, CBM2ASC comes in, converting a desired binary file from Commodore ASCII to standard ASCII.

Download CBM2ASC now [22 kB]. The ZIP file contains the CBM2ASC executable (version 1.1, dated 1999 Jan. 28), and a text file that explains the program and its usage in more detail.

1Unfortunately, this utility no longer seems to be available on the Internet. CTools04 appears to provide the same functionality, but I have not used it. A variety of Commodore 64 file utilities are available at

Computer Graphics

Meyer Logo Startup and Shutdown Screens for Windows

Click to download mlogo.zipNow available—the classic ‘M’ logo, for your Windows desktop! Tired of the bland graphics that remind you everyday of your computer’s fealty to Microsoft Corporation? Replace them with graphics to remind you everyday of your new fealty to Meyer Gigacorporation! [287 kB] includes a textured high-resolution bitmap for use as a desktop background, and startup and shutdown screens for Windows 95/98/Me. The image at left shows the animation of the startup screen once it is installed. Installation instructions are in the README file within Unfortunately, Microsoft changed the specifications, so that these startup and shutdown screens will not work under Windows 2000 or XP. You can probably guess as to why Microsoft did this.

Computer Game Levels

Starcraft mission: The Citadel of Aiur [259 kB]
(click image to download)

A screenshot (click image to enlarge)
“The Citadel of Aiur” is a Starcraft: Brood War mission for the expert player. Either a single person, or two allied vs. the computer, may play; be sure to set the game type to “use map settings.” The scenario consists of a final assault on the primary citadel of the Protoss homeworld, Aiur, by the Terrans united with Kerrigan's Zergs. Needless to say, the Protoss pull out all the stops to keep this from happening. The map includes loads of “triggers” to spice up the scenario, as well as a sizeable Mission Briefing, in-game text, and one or two surprises. More information can be found in the README file within The scenario was completed on 1999 May 11.

You may find the scenario impossible when you first play it, but believe it or not, it is definitely winnable—I have single-player save games that prove it. My brother Kent and his friend, playing allied vs. the computer, also won. Kent told me that he was very irritated by the mission. I think he meant that as a compliment.

Warcraft 2 Maps

I created two custom maps, or “PUDs,” for the computer game Warcraft II when it was popular several years ago. The ZIP file [39 kB] contains these two maps, HOGITALL.PUD and SHEPHERD.PUD, as well as a README file which briefly explains them. I have placed the maps in the public domain; see the README file for legal stipulations.

HOGITALL.PUD was designed and optimized for four human players allied against four computer players. The “twist” to this map is that all four humans must share a single, but massive, gold mine in the center of the map. If you send too many peasants to the gold mine, you will probably anger your fellow players, hence the map name (“Stop hogging it all!”); I think this concept made for a rather unusual Warcraft II scenario. SHEPHERD.PUD is more ordinary, but does involve a lot of sheep.

Scientific Publications

Ph.D. Dissertation

Binary Star Speckle Photometry and Astrophysical Implications. Ph.D. dissertation, Yale University (2002). ISBN: 0-493-69280-0. U.S. Copyright Office registration number: TX 5-620-777.

Free hardbound copies are no longer available. Copies are available through the following channels:

  • Electronic. Someday I’d like to set up a webpage that offers automatic downloading of the dissertation. For now, however, please send me an email via and we can arrange a way to send you an electronic copy. The following formats are available:
    • PDF, formatted for single-sided printing [8009 kB]
    • PDF, formatted for double-sided printing [8009 kB]
    • PostScript, formatted for single-sided printing [15950 kB; 8343 kB zipped]
    • PostScript, formatted for double-sided printing [15946 kB; 8345 kB zipped]
    The PDF formats are fine for viewing on the screen, but some of the figures look mildly “gritty” when printed. The PostScript format is the definitive format; this format, usually the double-sided version, was printed directly to laser printers to create the hardbound copies that I have distributed.

  • UMI. UMI (a.k.a. ProQuest) offers, for a fee, the dissertation in the following formats: PDF (downloadable over the Web), unbound paper, softcover, hardcover, microfilm, and microfiche. However, these are all generated from microfilm, with the result that many of the figures are grossly washed out or even unreadable, and the color figures are reduced to black and white. I sent UMI a “clean” (i.e., 100% digital from start to finish; no printing and subsequent scanning involved) PDF with the master paper copy, but for some reason they ignored it, and generated their PDF from microfilm of the paper copy. The PDFs listed under the heading “electronic” above are all crisp and in full color.

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