Walter D. Pullen (Astara@msn.com) wrote the original version of Astrolog. He ported the main planetary calculation routines to C. These routines were based on the work of James Neely. Neely's routines were listed in Michael Erlewine's Manual of Computer Programming for Astrologers. The program was originally written in 16 bit.
Over time, several people began writing upgraded versions of Astrolog. Walter Pullen wrote Astrolog 5.30. He borrowed the accurate ephemeris databases and formulae in the calculation routines found in the Placalc program. These were written and copyrighted by Alois Treindl and Astrodienst AG. Valja (Valentin Abramov) modified Astrolog 5.30, creating successive versions from 5.30a to 5.30g, including the last of this series, 5.30g1.
Alois Treindl then modified 5.30 to include the new Swiss Ephemeris instead of the older Placalc ephemeris, calling this 5.31. Valja included this new modification and changed the name from 5.30g1 to 5.31g.
Walter Pullen then wrote the next version of Astrolog, version 5.40, using the older Placalc ephemeris. You can download a copy of Astrolog 5.40 and auxiliary files at the Astrolog webpage at Bonnie's Links. Tyrin Price has written a miniFAQ for Astrolog 5.40; you can find it at Astrologica.
Astrolog 5.30, 5.30a to 5.30g1, and 5.40 all use the Placalc ephemeris. They look for ephemeris files in the folder that contains the astrolog.exe file. There are three types of files: CHI_##, CPJV_##, and LRZ5_##. The CHI files contain the positions of Chiron, the CHJV files contain the positions of the four main asteroids, and the LRZ5 files contain the positions of Jupiter through Pluto.
In Astrolog 5.40, the ephemeris files can be turned on and off by going to Setting -> Calculation Settings. When the ephemeris files are turned off, Astrolog 5.40 will use the Matrix routines which give locations significantly in error the further we go away from the 20th century. If the ephemeris files are turned on but can't be found, these versions of Astrolog will return an error message and use the Matrix routines. Astrolog 5.31 and 5.31g use the Swiss Ephemeris. The Swiss Ephemeris is discussed in the next section.
Astrolog 5.40 supports the YE switch which is used to modify the orbital characteristics of any selected planet. This flag can be used to "add" a new (hypothetical) planet to Astrolog 5.40. See Inserting Transpluto into Astrolog 5.4 Using the YE Switch for a full discussion of entering hypothetical planets into Astrolog 5.4.
Alois Treindl followed up Walter Pullen's version 5.40 with version 5.41. This version uses the new Swiss Ephemeris which is faster and more precise than the Placalc ephemeris. This version also included the addition of fixed stars, improved graphics, and a new method for interpretations.
Valja then took 5.41 and included all the changes he had made up to 5.31g, calling it 5.41a. He then wrote successive versions 5.41B, 5.41C, 5.41D, 5.41E, 5.41F and 5.41G. These are all 16-bit versions of Astrolog. They will not read the Placalc ephemeris files in the form of CHI_##, CPJV_##, and LRZ5_## which prior versions of Astrolog used. You can download a copy of Astrolog 5.41G at Astrologica.
These versions of Astrolog should use ephemeris files which can be downloaded from the Astrodienst website at: ftp://ftp.astro.com/pub/swisseph/ephe/. There are 3 types of Swiss Ephemeris files. Those of the form sepl_##.se1 are for the planets, semo_##.se1 are for the moon, and seas_##.se1 are for the asteroids. Each file covers 600 years, with the two digits in the file name (##) being the first two digits of the first year in the file. For example semo_18.se1 is the ephemeris file for the moon which covers the years 1800 to 2399. For files covering years that are BC, the "_" is replaced with an "m". The files can be downloaded for the time period that you need.
By default, versions such as Astrolog 5.41G look for the ephemeris files in the folder which contains the astrolog.exe file. The use of the ephemeris files can be turned on and off by going to Setting -> Calculation Settings. Like Astrolog 5.40, Astrolog 5.41G will also use the Matrix routines when the ephemeris files are turned off. This will give locations significantly in error the further we go away from the 20th century.
When the ephemeris files are turned on in Astrolog 5.41G but it can't find the ephemeris files, it will use a built-in analytical ephemeris which does provide very good precision. It appears that this built-in analytical ephemeris is provided by Swiss Ephemeris which quotes accuracy of "0.1 arc seconds for the planets and 3" for the Moon." No time period is given for this accuracy to be relevant over, however the built-in ephemeris is valid for 3000BC to 3000AD.
For the majority of purposes, this accuracy is quite acceptable. Unfortunately, this built-in analytical ephemeris does not include the asteroids, only the moon and planets. If Astrolog 5.41G can't find the asteroid ephemeris files, then it will use the rather inaccurate Matrix routines for asteroids such as Chiron.
Astrolog 5.41G also supports the YE switch which is used to modify the orbital characteristics of any selected planet. This flag can be used to "add" a new (hypothetical) planet to Astrolog 5.40. See Inserting Transpluto into Astrolog 5.4 Using the YE Switch for a full discussion of entering hypothetical planets into Astrolog 5.4.
In March 2004 Antonio Ramos, with the help of Chris Mitchell and Michael Rideout, then converted the 16-bit Astrolog 5.41G into the 32-bit version called Astrolog32 1.00. This 32-bit version was slightly faster, and had the ability to save filenames longer than 8 characters. Astrolog32 1.05 arrived in April 2004. Astrolog32 1.10 followed in June 2004. For more details on the changes made in each version of Astrolog, see the History.html file which is included when Astrolog32 is installed. You can download a copy of the latest 32-bit program at Astrolog32
The earliest editions of Astrolog32 (1.00 and 1.05) contained the ability to use the old Matrix routines. In Astrolog32 version 1.10, the capability to switch between the old Matrix routines and the ephemeris files has been removed, and the use of the ephemeris files can not be turned off. Since the Matrix routines were less accurate than the ephemeris files, this does not present any real problems in most situations. Unfortunately, hypothetical planets are not supported in Astrolog32 1.10, and need to be represented by the use of the Matrix routines. Several hypothetical planets are currently included in the Swiss ephemeris. The author plans to support them in a later release of Astrolog32. It is also the intention of the programmers to include Swiss Ephemeris routines, rather than the Matrix routines.
Like Astrolog 5.41G, Astrolog32 also uses the ephemeris files which can be downloaded from the Astrodienst website at: ftp://ftp.astro.com/pub/swisseph/ephe/. The default location of Astrolog32 is in the folder named C:\astrolog32\ephemeris. However, Astrolog32 allows you to change the location for the ephemeris files by going to Settings -> Directory Settings.
When Astrolog32 can't find the ephemeris files, it will use the built-in analytical ephemeris which does provide very good precision. Again, this built-in ephemeris only includes the moon and planets, and not the asteroids. When Astrolog32 can't find the asteroid ephemeris files, then it will use the rather inaccurate Matrix routines for asteroids such as Chiron.
Many changes were done to directories in Astrolog32 1.10. When earlier versions of Astrolog32 looked for a file, it searched for that file in five to seven directories. These were the current directory, three directories specified with environment variables plus version number, and one to three directories specified at compile time (usually c:\astrolog).
With the new changes, Astrolog32 will look for files in three directories
only, in this order:
1. current drive and directory
2. drive and directory where astrolog32.exe exists
3. a directory that depends on the type of file being located
The following directories have been defined, and the files stored in each
directory are shown:
Icons, URLs, documentation files, fixed stars catalogue
Swiss Ephemeris files
Charts and planet position files
Interpretation files (pl01.dat, house10.dat, etc)
Charts saved as text, bitmap, Windows Meta File, or Postscript
American Atlas and International Atlas
Currently, Astolog32 uses the Swiss Ephemeris in its unchanged form. Although Astrolog32 passes a list of search directories to the Swiss Ephemeris, the Swiss Ephemeris has its own file search routine. The environment variable SE_EPHE_PATH defines one of the places to be searched.
Always verify that any version of Astrolog is reading the downloaded ephemeris files. It has been found that certain other astrology programs can change where Astrolog32 searches for the files. For example, AstroFrames is a primary directions program whose ephemeris files are located in C:\Program Files\AstroFrames\. After AstroFrames has been installed, C:\Program Files\AstroFrames\ becomes the default folder for Astrolog 5.41G, Astrolog32 1.10 and even swewin32.exe (the Swiss Ephemeris program). All these programs are apparently referencing the same environment variable. This occurs even if we have defined the default directory for the ephemeris files in astrolog32.dat file.
Unfortunately, different versions of MS Windows are not consistent in how they allow the user to see the current set of environment variables. If you are running Windows XP, you can go to Start -> Control Panel -> System -> Advanced tab -> Environment Variables.
If you are using Windows ME, you can go to Start -> Programs -> Accessories -> System Tools -> System Information. This will bring up a window entitled "Microsoft Help and Support". You should open the Tools Menu at the top of the page, and select the System Configuration Utility. Then select the Environment Table, select PATH, and click on Edit. To append to the list, just type your direction onto the end of the list. You should separate filenames with a semicolon (;), but do not put a semicolon on the absolute end of the list.
Environment variables can also be found in the Autoexec.bat file. Certain versions of MS Windows will allow you to open this file with the sysedit program. You can run this program by going to Start -> Run and then typing sysedit. The system configuration editor will open with four windows. One of the windows contains Autoexec.bat.
To determine if the correct ephemeris files are being used, remove the ephemeris files from Astrolog's default directory. Then turn on the ephemeris files if you are using a 16-bit version or Astrolog32 1.00 - 1.05. Make sure that Astrolog is displaying arc-seconds. Then go back a fair amount of time to, say, Jan 1 1000 0:00 at 0W 0N (make sure you have ephemeris files for then). Note the positions of the Sun, Moon, Pluto, and an asteroid like Chiron. Then replace the ephemeris files and refresh Astrolog by going to another date and back to the original one. If the ephemeris files are being read, there should be some very small changes to the positions of the Sun, Moon and Pluto, and a major change to the position of Chiron.
Astrolog 5.40 has the ability to display the positions of 47 of the brightest and most important stars in the sky. To include these stars in a chart, use the -U option. Since stars are fixed in the sky, they will never change position in the -s sidereal zodiac. However, the fixed stars will slowly precess forward in the normal tropical zodiac. The -R restriction option can be used to determine which stars are actually included. Astrolog 5.40 always uses the Matrix routines to calculate the location of fixed stars.
As you know, Astrolog 5.41G uses the Swiss Ephemeris instead of the older ephemeris used by Astrolog 5.40. The star calculations were move from the old Matrix routines to the Swiss Ephemeris. Astrolog 5.41G depends on a file named FIXSTARS.AST for its information related to fixed stars. By default, the star catalogue is located in the folder that contains the astrolog.exe file. The value of the SE_EPHE_PATH environment variable can alter the default location.
Astrolog32 also uses the Swiss Ephemeris for its calculations. Astrolog32 1.10 depends on a file named Fixstars.cat for information related to fixed stars. This file should be in the Main folder in the astrolog32 directory tree. The actual search sequence can be affected by the SE_EPHE_PATH environment variable.
When any version of Astrolog runs, it searches for a Configuration File. This file contains the default settings for the program.
Astrolog 5.40 expects that file to be named ASTROLOG.DAT. You can view such a file by clicking ASTROLOG.DAT. Please use your [BACK] key to return to this page. This file is not very user friendly. Over the years, other versions of the file have become common. The Config.DAT file contains comments that are useful when you wish to change the default settings.
Astrolog32 expects the file to be named astrolog32.dat. If this file does not exist, the program will ask you if you wish to configure Astrolog32. The new configuration file has several new additions. You can view such a file by clicking astrolog32.dat. Please use your [Back] key to return to this page. Again, the default version of this page is not very user friendly.
A semicolon is used to mark a comment line in the Configuration File. The comment terminates at the end of the line. You may edit the configuration file using Notepad or Wordpad. If your editor or email program inserts a carriage return at line 80, it can make the file unreadable by any version of Astrolog.