Linux, Talon and Astronomy

A new open-source application lets professional and amateur astronomers explore space from their desktops.

We've been fascinated by astronomy since the ancient Chinese first charted the skies. The computerization of astronomy, some would argue, is its greatest leap forward yet. Today, unattended robotic telescopes scan skies that have been charted over centuries, recording their findings in modern databases. CCD cameras capture images impossible to define on film. It's an exciting time to be an astronomer, whether amateur or professional.

The revolution in astronomy doesn't stop at the hardware. Research-grade telescopes in observatories from Spain to Korea are under the control of open-source software and Linux-based computers. Under the open-source model, scientists are free to modify the control software, creating a trickle-down effect that benefits amateurs. Open source and Linux even have changed the scientific method. With source code freely available, peer review now occurs not only on the data, but on the data gathering methods as well.

At the forefront of this open-source astronomy revolution is Talon. Talon was originally developed by Ellwood Downey as the Observatory Control and Astronomical Analysis Software (OCAAS). In 2001, the software was purchased by Torus Technologies of Iowa City, Iowa. In late 2002, Torus was purchased by Optical Mechanics, Inc., and the updated OCAAS package was released as Talon under the GPL.

During the past two years, I've had the daily pleasure of working with Talon. I've installed and configured the software on multiple telescope packages, and I've followed these telescopes to destinations around the world for installation and on-site configuration. It's my pleasure to share with you some of the broad points of Talon installation, configuration and use.

Talon can be downloaded at observatory.sourceforge.net. The software interacts with integrated motion control boards, available from Optical Mechanics, Inc. (Optical Mechanics Motion Controllers) or Oregon Microsystems (PC39 Motion Controllers). Object acquisition and tracking, scheduled operations, environmental monitoring, dome control, image analysis and processing all fall under the control of Talon. Networked operations also are possible using a remote X session.

Using Talon

The Talon package contains a full installation script; install.sh creates a talon user, compiles the binaries and creates a set of text configuration files for initial operation of the telescope.

Talon contains a full compliment of astronomy applications designed specifically for use as a suite of tools. The main Talon interface utilizes the Motif toolset, producing a familiar and unified look and feel throughout the application set. Although the toolset is rich, the following four tools should be of use to most observers.

xobs is the main Talon control window and is launched with the terminal command startTel. It contains all the monitoring and calibration tools necessary for operation. This window provides manual control of the telescope and any attached peripherals, such as a filter wheel or dome control. It also provides a constant display of the current position of the telescope, as calculated by feedback from the motor encoders. This feedback is provided in a set of text boxes within the xobs window.

Figure 1. xobs, the Main Talon Control Screen

When using Talon, the first important task is to find the home position of the various encoders located throughout the system. These encoders close the loop on the operation of the axes, providing a static count for the full travel of each axis. Movement of the telescope is calculated in part by the motion of the chosen axis in relation to the zero position on the encoder. Decrementing the Declination encoder, for example, generally moves the telescope to the north. The operation to find homes in the xobs window hunts for and establishes the zero positions on each axis encoder.

Using the software paddle command in the xobs window (Figure 2), the user can position the telescope, filter wheel and focus position manually. The motion of the telescope to the east and west is referred to as the right ascension (RA) or hour angle (HA) of the telescope. To travel north and south is referred to as Declination (Dec). Using positive and negative encoder counts, moving the telescope axes is a simple matter of moving the axis positive or negative x (RA) or y (Dec). These coordinates are in relation to the North Pole.

Figure 2. The Talon Software Paddle, Used to Move the Telescope Manually

Additionally, Talon provides data on the weather conditions at the observing site with an attached Davis weather station. This feature ensures that the telescope is not exposed to adverse weather conditions during unattended operations. When conditions fall within a predetermined range, the observatory dome or roll-off roof closes, the telescope moves to a stowed position and operations cease. As with the position data, this information is provided in text boxes within the xobs interface.

Finally, xobs provides a search function that allows the user to enter the name of a celestial object, search an internal database and automatically slew the telescope into position to observe and photograph the requested object.

telsched is the element of Talon that makes robotic unattended observing sessions possible. This can be a critical function for institutions conducting research from remote locations or those requiring repeated observations of particular objects over a given period of time.

Figure 3. Telsched, the Talon Operations Scheduling Program

The telsched command opens a scheduler for these unattended observing sessions. The scheduler automatically calculates images to be taken during the session based on the size (in degrees) of the chunk of sky the user selects. In general, the tighter the area of the sky (fewer degrees), the more images taken. Images taken by telsched during an unattended session are stored in a directory of the user's choice. All instructions created by the telsched program are stored in a flat file. These instructions are referenced by xobs when the telescope is slaved off to robotic control from the xobs interface.

Camera is another terminal-launched application in the Talon suite. It provides complete control over the functions of a CCD camera attached to the telescope.

Figure 4. Camera, the Talon Image Processing Application

The camera application includes tools for exposure time, image size, software image filtering and image analysis. Camera also contains tools for adjusting the brightness and contrast of images, determining the area of interest (AOI) of the image and automatically labeling objects by comparison to the World Coordinates System (WCS). The latter tool is, in fact, a pattern-matching algorithm that allows the system to compare known patterns of objects to the WCS database.

xephem provides a software ephemeris, or sky charting interface, for the rest of the Talon suite. As with other ephemerides, it relies heavily on correct geographical and time coordinates; this information can be configured manually by the user. xephem also can be configured to poll an attached GPS at regular intervals, adjusting the system time to account for internal clock drift.

Figure 5. xephem, the Ephemeris Program for Talon

The xephem program, launched from the command line with xephem, provides a granular view of the current sky. Data on each object is provided in a right-click pop-up screen. The user also can point the telescope using this pop-up, a feature used extensively for calibration. Magnification can be increased, effectively looking deeper and deeper into the sky. As an alternative to zooming, the user may select a minimum magnitude (apparent brightness) threshold. This allows brighter stars to be filtered in the ephemeris view, leaving only the dimmer objects in the window. The sky view also may be rotated, and object type filtering is provided. For example, globular clusters can be selected, eliminating the view of all other object types.

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Re: Linux, Talon and Astronomy

Anonymous's picture

I bought this issue on the news stand specifically for this article. What a disappointment to find the article was written a year ago and the software is no longer supported! I don't think I'll be buying this magazine again.

-Tom

Re: Linux, Talon and Astronomy

Anonymous's picture

So do I.

Thierry

KStars can control popular telescopes

Anonymous's picture

Most amateur astronomers use telescope from Meade and Celestron, the latest version of KStars (to be released in KDE 3.2 http://edu.kde.org/kstars) includes a support for such telescopes.

It seems that Talon is really great and professional, albeit it is limited to the Optical Mechanics and Oregen motion controllers.

For most of us amateur astronomers out there who own a Meade or a Celestron, KStars allow us to easily control the telescope.

Re: KStars can control popular telescopes

Anonymous's picture


Most amateur astronomers use telescope from Meade and Celestron

and what makes you think that?
I know a lot of amateur astronomers, and not a single one owns a meade or celestron telescope... because they just suck.
Way too pricey for what those things offer.

Re: KStars can control popular telescopes

Anonymous's picture

You're right, but the whole article is about Software Telescope Control. So maybe most amateur astronomers have Dobs or refractors, but the majority of those who have _computerized_ mounts that can be used along with a control software has Meade/Celestron.

Re: Linux, Talon and Astronomy

Anonymous's picture

Kstars, included in KDEGames, contains telescope control software.

http://edu.kde.org/kstars/

And the telescope control documentation:

http://docs.kde.org/en/HEAD/kdeedu/kstars/indi.html

KStars is being actively developed.

Derek

Re: Linux, Talon and Astronomy

Anonymous's picture

A small correction, KStars in included in the KDE Eduntainment package.

Maybe Linux Journal can review KStars when KDE 3.2 is out?

Re: Linux, Talon and Astronomy

Anonymous's picture

Interesting story, this.
The article was written nearly a year ago. Since that time the company, Optical Mechanics, Inc., has shifted its focus to high precision optics and away from telescopes. I, in the meatime, have gone to work for a presidential campaign in Little Rock, AR. The Talon project on sourceforge has, to say the least, languished.
As the result of the article, I've had several offers to help rebuild the project page and continue development on Talon. You can expect to see a new project page within the next week or so (as of December 7), and an initial release of Talon shortly thereafter. The software is available now via CVS on sourceforge.
It started strong, faded, and looks to soon be revived by the open source community. Keep an eye open.
Tony Steidler-Dennison

Re: Linux, Talon and Astronomy

Anonymous's picture

I'm in the proccess of building my observatory to house my 10" Meade. I would really like to use all of the capabilities of this software.

Another good piece of software is "The Sky" for Linux and "Satalite tracker". Both are easily found threw a "google" search.

Re: Linux, Talon and Astronomy

zedkatuf's picture

Hi Tony

I've just downloaded your first source release from the Sourceforge site...Like others on this list, the setup I'm using is an LX200, (with a Robodome arriving in the Fall, hopefully).

I'm interested in seeing something like Talon being used for my setup, as I'd like to run it all under Linux....I'll email you to chat further.

Regards,

Dez Futak.
zedkatuf@hotmail.com

Re: Linux, Talon and Astronomy

Anonymous's picture

Thanks for the info, Tony. I was able to find a page
for Talon on sourceforge at:

http://sourceforge.net/projects/observatory/

I too am very interested in seeing this project move
forward. I am building a robotic telescope and plan
on contributing to the community both the mechanical design of my mount and my coding efforts on a resurrected Talon project.

Tom Bartol

Talon Development

Fabian Lim's picture

Hi Tom,

Myself and my partner are currently working on compiling the Latest Talon Software and porting it at the University of Toronto's Observatory. We are both students from the University of Toronto and we are trying to standardize the code so that it would work on all LX200 telescopes on Linux Enterprise 3.0. We are currently facing problems compiling, and we would like to know how far you have gone with this code. Please let us know if you would be interested in working together.

Thanks,

Fabian Lim

Re: Linux, Talon and Astronomy

Anonymous's picture

Ilooked for this software, too. Not only is it missing from the claimed spot, it is not available from the optical company, nor is it even mentioned on the author's website. So, what gives? if it is a product, that fact should have been stated in the article. If it is freeware or shareware, that too should have been stated. I'm seriously disappointed, as I have a potenitial use for Talon. Too bad.
Don Latham

Re: Linux, Talon and Astronomy

Anonymous's picture

The source code for Tolon is located at "www.sourceforge.net". Just type Talon into there search window. I've downloaded it, unpacked it, and now trying to install it

Re: Linux, Talon and Astronomy

Anonymous's picture

The source code for Tolon is located at "www.sourceforge.net". I've downloaded it, unpacked it, and now trying to install it

Re: Linux, Talon and Astronomy

Anonymous's picture

Has anyone successfully downloaded this code? I was curious
enough to want to poke around at it a bit, but http://observatory.sourceforge.net/ is an empty directory, and the
sourceforge project at http://sourceforge.net/projects/observatory/
claims not to have released any files. Am I missing something?

Re: Linux, Talon and Astronomy

Anonymous's picture

The project is still there, and indeed the latest version is 0.85, Dec 29 2003. But it has moved - observatory.sourceforge.com is now an empty directory. The new URL is:

http://sourceforge.net/projects/observatory/

Re: Linux, Talon and Astronomy

Anonymous's picture

Interesting story, this.

The article was written nearly a year ago. Since that time the company, Optical Mechanics, Inc., has shifted its focus to high precision optics and away from telescopes. I, in the meatime, have gone to work for a presidential campaign in Little Rock, AR. The Talon project on sourceforge has, to say the least, languished.

As the result of the article, I've had several offers to help rebuild the project page and continue development on Talon. You can expect to see a new project page within the next week or so (as of December 7), and an initial release of Talon shortly thereafter. The software is available now via CVS on sourceforge.

It started strong, faded, and looks to soon be revived by the open source community. Keep an eye open.

Tony Steidler-Dennison

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