Sky Image Processor

since October 1999

[Sky Image Processor ---
a web-based astronomical image reduction and analysis system]

Your browser doesn't understand the <APPLET> tag. In a Java-compatible browser you would see a button here labeled "Start SIP". See Will SIP run on my machine?

[To open a SIP window click on the "Start SIP" button above (once everything is done loading). Example images to load from this server are m51dss.fit, m1dss.fit, m13dss.fit, m51ccd.fit, atlas1.fit, and atlas2.fit (use lower case letters). For instance, after selecting the menu item "File, Open Image File from the Internet..." enter "http://www1.phys.vt.edu/~jhs/SIP/images/m51dss.fit" in the dialog box.]

SIP is an astronomical image processing program which runs over the Web. This package was written specifically for students (SIP could stand for "Student Image Processor," or "Standard Image Processor," or even "Simple Image Processor"). While SIP is designed for use by instructors and students at any educational institution, it can certainly be used by anyone with access to the Web. The program provides simple, yet quite general tools that enable the user to carry out standard CCD image processing procedures. Complicated procedures (e.g., unsharp masking) can be accomplished in a step-by-step fashion, using the tools provided, allowing the user to learn and understand how the procedures work (no "black box" procedures). The author is John Simonetti, a faculty member of the Department of Physics at Virginia Tech.

The program is written in the Java(tm) programming language in order to make it usable over the Web. It should run on any machine with a Java 1.1 compatible web browser; for more details see Will SIP run on my machine?.

The goal of the SIP project is to provide a means for students to learn how to accomplish the three major tasks of astronomical imaging:

image processing and analysis -- combining images, or massaging images in order to extract quality information present in those images. What is the structure of distant galaxies?
photometry -- measuring the precise brightness of variable stars or flickering quasars, for example. Studies of variable stars yield measuring sticks for determining the size and age of the universe.
astrometry -- measuring accurate positions of moving asteroids or comets, for example. Position measurements of asteroids yield the data necessary to determine accurate orbits --- when will we discover that a near-earth asteroid is on a collision course with Earth?

These tasks, while of basic astronomical importance, are similar to much of the image processing and analysis done in a wide variety of scientific and technological fields. In this regard, astronomical image processing and analysis provides these experiences in a subject which has universal appeal to students. For information on how to use SIP for these tasks, and for example materials, see the links on the left side of this page.

Starting SIP

Click on the "Start SIP" button near the top of this page to open a SIP window. Example images to try loading from this server and playing with are m51dss.fit, m1dss.fit, m13dss.fit, m51ccd.fit, atlas1.fit, and atlas2.fit (use lower case letters in the names as shown; image credits). For instance, after selecting the menu item "File, Open Image File from the Internet..." enter "http://www1.phys.vt.edu/~jhs/SIP/images/m51dss.fit" in the dialog box. In browsers that can run signed applets you can also load images from your own machine or any location on the web (if you explicity give the applet permission to do so). See the links at the left side of this page for other images.

Mac users may not see a "Start SIP" button. Button or no button, Mac users will want to read Will SIP run on my machine?.

(For the Java-knowlegable, the SIP applet has been signed; the digital "signature" is "John H. Simonetti" and the certificate was produced by the "Virginia Tech Certification Authority." A signed applet cannot be tampered with by anyone. For more information on signed objects, and digital IDs see Netscape Object Signing: Establishing Trust for Downloaded Software. Also, please see the disclaimer at the end of this page.)

Why SIP?

Why use SIP as an image processor? SIP is unique in many ways. When using a browser that can run signed applets, SIP can load images not only from your machine but from anywhere on the Web. The program is loaded into your machine along with this Web page. This means you never need to worry about installing the software, or any upgrades. You always get the latest version. Once you click on the Start SIP button the program runs on your machine (not on this server), so you also get the speed advantages available to a program run off the local disk.

An instructor in Astronomy can use SIP to enable students to load and analyze images from anywhere on the Web (including the instructor's own collection placed on a local Web server). The instructor can be assured that everyone gets the same program, without the students or the instructor having to load any software onto any machines. Students can do the work from any computer: in a collective lab setting, from a campus computer lab, or from home. This sort of decentralized, distance-learning usage was the main motivation for writing this program (we use it in our Introductory Astronomy course, and plan to use it in our public and school outreach programs).

Finally, what's with the name? Well, you "sip" java, don't you?

Sign Up as a SIP User!

Please consider signing up as a SIP user. Web-distributed software, such as SIP, provides some advantages to the user compared to, for example, commercially purchased software: it's free, it requires no installation, upgrades occur without the user having to bother with another purchase/download, and anyone can use it anywhere they can sit down at a computer with internet access. However, the developer (me) has one problem: I can't easily tell how much interest there is in SIP! It helps me, personally and professionally, if I can show that there is interest in SIP. Please show your interest in SIP by signing up as a SIP user. In addition to helping me by signing up, if you choose to, you can receive a periodic e-mail newsletter about any improvements in SIP and other related information. The sign-up page has more information about signing up and about the newsletter.

SIP Poster at Atlanta meeting of the American Astronomical Society

I presented a poster on SIP at the AAS meeting in Atlanta (January 11-15, 2000).

jsimonetti@vt.edu | VT Physics | Virginia Tech | Java

This work was partially funded by grants from the Center for Excellence in Undergraduate Teaching at Virginia Tech. Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and other countries. Counter provided by WebCounter

Disclaimer: Neither I (John H. Simonetti), nor Virginia Tech make any representations or warranties about the suitability of this software (SIP), either express or implied, including but not limited to the implied warranty of fitness for a particular purpose. Neither I nor Virginia Tech shall be liable for any damages suffered as a result of using this software.