This lab is one of a series of World Wide Web labs developed for the large introductory astronomy classes at Northwestern University. The intro courses are geared towards non-science majors, and have no formal laboratory periods. The labs are intended to provide hands-on laboratory experience despite the lack of a formal laboratory facility. The Northwestern campus is wired for Ethernet, and students are provided with free Ethernet software. Most students own their own computers, and can perform the laboratory exercises in their dorm rooms. We have created an astronomy tutorial room with seven Power Macintoshes for those students who lack an appropriate computer, or need help with a lab. The room is staffed by teaching assistants.


Funding was provided by National Science Foundation grant number DUE-9354525, with Northwestern University principal investigators Drs. David M. Meyer and David Taylor. Dave Meyer has been the primary overseer of this project.

Data and Results

A very special thanks to Dr. Laura Ferrarese and co-authors for permitting me to use their published data and figures. I hope they are pleased with my use of them.

WFPC2 image processing

The Hubble Space Telescope WFPC2 images were processed using IRAF, the Image Reduction and Analysis Facility, STSDAS, the Space Telescope Science Data Analysis System, and SAOtng, the next generation version of the Smithsonian Astrophysical Observatory SAOimage display program. GIF images of M100 fields were made within SAOtng.

IRAF is written and supported by the IRAF programming group at the National Optical Astronomy Observatories (NOAO) in Tucson, Arizona. STSDAS is written and supported by the STSDAS Group at the Space Telescope Science Institute in Baltimore. SAOtng (SAOimage: The Next Generation) is an astronomical display program being developed cooperatively by Smithsonian Astrophysical Observatory (SAO) and the National Optical Astronomy Observatories (NOAO).

I would like to give a personal note of thanks to Eric Mandel, the architect for SAOtng, for his prompt, enthusiastic and friendly support. Although SAOtng was still under development, Eric made the time to quickly fix every major problem I encountered in the Dec Alpha version. He also patiently explained details when necessary. My job was a lot easier for his efforts. Making GIFs from WFPC2 exposures is a breeze in SAOtng.

Programs and GIFs

Animated GIFs were created using whirlGIF. WhirlGIF was developed by Kevin Kadow, and is based on Mark Podlipec's txtmerge file.

Thomas Boutell's Mapedit program was used to create some of the imagemaps.

Most of the non-astronomical GIFs were hand-drawn using Adobe Photoshop. Only the stylized 5-pointed star GIFs and the stylized Sun were downloaded from other Web pages. I had to draw many of the GIFs freehand with a mouse, which was no small task. I am most grateful to Northwestern University's Learning Technologies Group, especially Dennis Glenn, Joe Germuska, and Dimitrios Dimitroyannis, for their ever-friendly technological support, and the loaner of a graphics tablet in recent months. The tablet didn't make me a better artist, but it sure made life a lot easier.

Some of the remaining GIFs were created with the aid of the gd library written by Thomas Boutell; I used the Perl version, written by Lincoln Stein of MIT. Other GIFs were created with the aid of Adobe Photoshop. Many were created or revised with the aid of XV, the X windows image display software by John Bradley.

Some of the Perl programs in this lab are based on or make use of programs written by Thomas Boutell, from his book "CGI Programming in C & Perl." One file of Perl subroutines was written by Robert Lentz, formerly of Northwestern University. John Watson kindly extracted portions of a Lentz program and inserted detailed comments to provide me with a starter CGI program which uses form elements to obtain image coordinates. The book "Teach Yourself CGI Programming with Perl in a Week," by Eric Herrmann, was extremely helpful.

Most of the animated GIFs in the Cepheid hunt were created by Northwestern graduate student Tom Renbarger. That was quite a job! Tom was supported by a GAANN Fellowship from the Department of Education.

As most browsers do not normally support the Greek alphabet, I thank Karen Strom and helpers for making Greek letters available to the community as GIFs.


When I began this project, I knew nothing about authoring Web pages. How I ended up doing this is a long story. Creating this lab required learning a vast amount of information about the Web, HTML, CGI programming, servers, software packages, and computer platforms. Robert Lentz, formerly a Web programmer and system administrator in the Northwestern astronomy group, taught me many of the basics, and pointed me to relevant sources of information. Although he is now employed elsewhere, he continues to provide support on advanced topics. He also taught me a lot about Macintoshes. Northwestern graduate students Hyong Lee and John Watson cheerfully provided a wealth of information on a variety of Web and computer topics. Northwestern research faculty Drs. Bill Purcell and Steve Matz enthusiastically offered their time, comments and suggestions when repeatedly asked, "Can I see how these pages look on your computer screens?" Last, but hardly least, working for Dave Meyer has been a pleasure.

Diane Dutkevitch, Lecturer, Northwestern University
September 1998

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