Venus AUEB Forum

Mapping the universe with open source software

Thursday November 16, 2006 (03:01 PM GMT)

By: Lisa Hoover

Astronomers at New York City's Hayden Planetarium and Rose Center for Earth and Space think space exploration should be easily accessible to anyone. To make that possible, they offer an interactive atlas of the universe that anyone can download for free.

The project, funded by NASA, originally began in 1998 as the Digital Galaxy Project, and was intended to create an accurate, interactive, 3-D representation of the Milky Way galaxy. In 2000, Hayden's Department of Astrophysics decided to expand the project and rename it Digital Universe to reflect its new goal to map the rest of the known universe. They discovered, however, that the software they had developed was not open source, and the resulting restrictions prevented them from adding the additional capabilities they needed to continue their project. To complicate matters, because the software ran on an SGI supercomputer, it was virtually inaccessible.

Fortunately, Stuart Levy, a developer for the National Center for Supercomputing Applications (NCSA), had created an open source tool named Partiview that he used to explore large data sets on his laptop. Developers at Hayden needed a tool that would interpret the large collection of data on the universe and regurgitate it as useful and comprehensible information. Partiview was a perfect fit for their needs. In April 2002, developers at Hayden began offering Digital Universe and the Partiview viewing tool for free download on their Web site. According to Brian Abbott, manager of Digital Universe at Hayden, "since that time, we have had over 100,000 downloads of the Digital Universe atlas, Partiview, and other data products combined."

Partiview is licensed under the Illinois Open Source License, which has been officially certified by the OSI. The Digital Universe license, while not open source, allows users to freely download and distribute verbatim copies of the Atlas, as well as add data and alter existing data. "It is free to those who wish to use it on a PC, for personal or educational use," says Abbott. "But we have retained some control over the data sets to maintain their quality. A curatorial process is necessary to maintain our standards for accuracy."

Although a commercial version of Digital Universe is available through companies that market products directly to planetariums and facilities that provide entertainment along with their education, Abbott says Hayden offers the free downloads because it receives money from NASA, which mandates that publicly funded research be publicly available. "We also lean philosophically toward the idea that the experience of exploring the universe should be available to everyone."

Though the commercial version is typically used in planetariums because the online version is not suitable for today's high-tech domes and digital projection systems, the free version is widely used by educators in a variety of settings, including middle and high schools, museums, and universities. According to a recent survey of users, approximately one-third use the software in an educational setting, but Abbott says Digital Universe is ideal for people who pursue astronomy as a hobby or are doing small research projects with commercially available telescopes.

Bob Lambert uses the software for student and adult education programs at the John J. McCarthy Observatory in New Milford, Conn., and proclaims it to be "dazzling. Our usage is primarily for 'introduction to the universe' awareness sessions and tours, because Partiview and Digital Universe offer such exciting visualization opportunities. No other tools come close to them for navigating the heavens. These tours do more to excite, amaze, educate, and entertain than anything else we do. On a formal basis, we use these tools integrally with the fifth and sixth grade and high school curricula to support teachers."

Educators at the Observatory had been using various planetarium simulator tools for many years, but realized they needed a more capable visualization tool. Their primary criterion was that it work "out of the box" without a lot of adjustments and tweaks. Lambert says they leaned toward an open source solution for its staying power and ability to be easily updated and upgraded as needed. After reviewing several prepackaged options, they decided that Partiview and Digital Universe would meet their needs.

"Partiview is in a class by itself with the dynamics and flexibility, and 3-D mode, which we may be using more than anyone else. The stunning visualization, easy control, superb navigation capability, and 'real data in the proper location in space' is an extraordinary combination," says Lambert. "We do still use other packages ... but Partiview/Digital Universe is the 'big gun' in our excellent arsenal [and] I am sure it will remain that way for a long time."

Open source software looks skyward

The open source software movement is making the leap from the desktop to the stars with applications like Virtual Moon Atlas, Stellarium, and Celestia. Amateur astronomers use these programs to identify lunar features, chart celestial bodies for observing sessions, and take users on virtual tours of the universe.

Virtual Moon Atlas

Since my old 60-millimeter telescope is a tad small for observing deep space objects like galaxies, my journey started with one small step to the moon. Created by a programmer (Christian LeGrand) and a lunar observer (Patrick Chevalley), Virtual Moon Atlas 2.1 is a Windows application distributed under the GNU General Public License. Written in Delphi 6, it comes in lightweight form, without OpenGL graphics, and heavyweight (basic and expert), with OpenGL graphics. The lightweight form provides a two-dimensional map of the moon and a complete database of lunar topographical features. The heavyweight form provides the same features with more graphic detail. The interfaces are identical. As a user, I simply looked at a large map of the moon on the left side of the screen, clicked on an item of interest, and read information about the feature in tabbed folders on the right side of the screen.

Each time I selected a lunar feature, Virtual Moon Atlas quickly responded with abundant information: feature type, when it was formed, dimensions, coordinates, description, level of astronomer interest, best times for observation, minimal equipment required, print references, and Web links for additional imagery. Other tabs on the right side of the screen allowed me to log my own observation notes, compute details about the position and phase of the moon, and sort the database of lunar objects based on a variety of criteria. Virtual Moon Atlas allowed me to plan several lunar observing sessions and made them more rewarding by directing me to the most intriguing objects.

Stellarium

My journey continued on to the planets with an exciting planetarium program called Stellarium. This beta version is available for the Linux, Windows, and Mac OS X operating systems, and requires a graphics card capable of rendering OpenGL graphics.

Stellarium took me from a light-polluted backyard and put me in a virtual country meadow for my observing session. To set up for an accurate depiction of the sky, you enter the latitude and longitude of your observing location (or guess by placing yourself on a world map), put in the date and the time of your observing session, and select how quickly you want time to move. As day gives way to night, the sky will darken and the virtual heavens reveal themselves. You can click on various celestial objects with the mouse to find out what they are, and center them in the screen by tapping the tool bar. The interface is unobtrusive and uses hotkeys extensively.

The fun really begins when you zoom in on an object. I found Jupiter, zoomed close in on it, and saw its moons. I was astonished to see that the great red spot and storms in the gaseous bands of the planet were animated! As my observing session progressed, the storms and red spot moved across the planet's face while the moons slowly made progress in their orbits. This detail far surpasses anything that I see with my puny telescope. However, Stellarium users wanting even more amazing views can find a link on the program's Web site to a company that can provide a compatible planetarium projector and planetarium dome for around $20,000.

This version 0.6.2 software generally ran smoothly, but it crashed when I tried to use its screen capture capabilities. This program closely mimicked my night sky, but I would have liked a function to create printer-friendly sky charts for my observing sessions.

Celestia

For the final leg of my journey, I had to leave this planet -- the views from here can be so limiting. Fortunately, Celestia 1.3.2, an open-source application for Linux, Windows, and Mac OS X, could take me virtually to the celestial bodies.
Thebe in Celestia
Jupiter's moon Thebe, in Celestia - click to enlarge

I started out from a perspective in orbit high above our planet, then took a guided tour of the universe. I took command and selected the objects I wanted to visit. The application uses vast amounts of photographic imagery compiled by space agencies and astronomers worldwide to create a richly textured virtual universe. It allows users to visit celestial bodies, fly around them, and zoom in for a closer look. Celestia draws on a database of over 100,000 stars, and has a catalog of more than 100 objects in the solar system, including man-made ones. I took a look at the International Space Station, but tinkerers can add their own spacecraft.

The only drawback I found with this program was the interface. While it is clean and uncluttered, Celestia does rely heavily on mouse gestures that take some time to become familiar.

Applications like this are almost enough to make a casual observer like me leave telescopes behind. But, then again, I could take a giant leap in telescope quality for the cost of Microsoft Office, which, thanks to open source software, I no longer need to pay.

The Punisher wrote:χρησιμοποιώ και το Stellarium αλλά και το Celestia και μπορώ να σας διαβεβαιώσω ότι αξίζει να τους ριξετε μια ματιά ... είναι καταπληκτικά.

Να προσθέσω επίσης ότι το άρθρο είναι πολύ κατατοπιστικό, καθώς αντιμετώπισα ακριβώς τα ίδια προβλήματα και δυσκολίες με αυτά που περιγράφονται παραπάνω!

Άντε ντε, μην κάθεστε ...δόκιμάστε τα !!!