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Automate your backyard observatory: operate your telescope remotely from the comfort of your living room by using off-the-shelf components.

ONE BITTERLY COLD February morning I was doing CCD photography in my backyard observatory with a 12-inch Meade LX200 Schmidt-Cassegrain telescope under crystal clear Virginia skies, but I wasn't enjoying the experience. I can endure temperatures of 12[degrees] F (-11[degrees] C) for about an hour, which is really only enough time to set up the equipment and acquire a few short exposures. I began wondering if there weren't some way to do this from the comfort of my warm house.

After some research, I realized that it is possible to come in from the cold, thanks to a range of off-the-shelf products. I purchased all the necessary hardware and software for about $2,500, and with a few afternoons of puttering around, my observatory was set up for remote-control operation.

Automation Basics

Although I wanted to automate my observatory mainly so I could do CCD photography in the winter, there are many ancillary benefits. I can slave the observatory dome to the motion of the telescope, focus by remote control, and use desktop-planetarium software to point the telescope. If you have a backyard observatory like mine, you may find that automation is easier than you imagined.

My remote system uses a wireless network and consists of a computer in my house, one in the observatory, and the adapters and network router necessary for the two to communicate with one another. All automated functions are performed by the in-dome computer, which I control with a laptop computer from my living room. This setup allows me to run relatively short cables from the automation devices (the telescope's motorized focuser, for example) to the in-dome computer and to use a single network connection to link the two computers.

All the peripherals I used are Astronomy Common Object Model (ASCOM) compatible. ASCOM is a set of standards for the control of astronomical instruments. Adhering to ASCOM enables me to easily add new tools and scripting possibilities so that the automation system can expand.

Computer Considerations

Automating an observatory greatly increases the workload on the in-dome computer. In my case, I went from a single piece of software for CCD control to five programs operating simultaneously to control the CCD, telescope motions, focusing, dome automation, and communications with the remote computer. The first step was to upgrade my in-dome machine to one with a 3-GHz processor and 1,024 megabytes of RAM. The new computer came with Windows XP, which provides more robust networking functionality and reliability than Windows 98 did on my old machine. In addition, the computer needed three more RS-232 ports to control the telescope, focuser, and dome. I was fortunate to find a PCI card on eBay that provides four additional RS-232 ports for just $35. Once I had optimized the computers, the next task was to establish a robust data link between them. There are two simple ways to accomplish this. You can run a dedicated Ethernet cable, or use a wireless router. I chose the latter with the addition of a repeater for improved signal strength and data-transfer rates. A wireless system also allowed me to avoid running a cable through the walls of my house, underneath a sidewalk, and across the yard to the observatory.

My first attempt at a wireless hookup between the two computers resulted only in frustration and in the realization that it was best to use a router and repeater that are actually designed to work with each other. After an Internet search I discovered the Buffalo Technologies (www.buffalotech. com) WRB-G54K matched wireless router and repeater. The pair are preconfigured at the factory to work together and, sure enough, they came to life as soon as I plugged them in. To further improve the signal, I added directional antennas (also from Buffalo Technologies) to both the repeater and the USB adapter on the in-dome computer. The result is a consistent, excellent signal.

Dome and Telescope Control

Once the computers were hooked up to the wireless equipment, the next step was to establish remote control of the in-dome computer via the laptop inside my house. Before embarking on this project, my biggest concern was getting this part to work, but it turned out to be very easy.

An experienced CCD photographer suggested UltraVNC ( or RealVNC ( client/server software, rather than a full-featured commercial package. In addition to being free, these programs are extremely small and don't tax the computer's resources very much. One downside of using UltraVNC is that the operating instructions are not very detailed. However, the two programs are similar enough that the user's guide for RealVNC (which is available online) can be used for both.

With the computers talking to each other, the next step was to establish computer control of the telescope. Of course your telescope has to be computer controllable to begin with, but you also need to choose control software that matches your needs. I upgraded my version of the TheSky ( to Level IV to take advantage of a number of new capabilities such as seamless integration with TPoint for improved telescope pointing accuracy and the ability to track satellites. Another feature of TheSky that I have found very handy is its ability to map my observatory's local horizon so that I know when a given object is up.

I used one of the RS-232 ports to connect my telescope to the in-dome machine running TheSky. This took only about 10 minutes following the directions in the software's user's guide. Indeed, the hardest part was determining which COM port was which, a question settled through trial and error.

It would be impractical to operate the telescope remotely without the ability to adjust its focus. There are many great products to choose from, but since I already owned a JMI microfocuser equipped with Digital Read Out, I chose PCFocus with FocusAide from Aquest (, which works with this focuser without requiring additional hardware. PCFocus provides the RS-232 connection to the focuser, and FocusAide is software that enables automated computer focusing with a number of image-processing algorithms.

Achieving automated focus has been one of the biggest ancillary benefits of my project. Rather than manually focus using a diffraction mask, with software I'm now able to achieve a better, more reliable focus automatically in just minutes.

Another virtual necessity for automated operation is having the dome rotation slaved to the telescope's movements. Without this feature, I would have to go outside at regular intervals and move the dome so that it doesn't eclipse the view through the telescope.

There are relatively few commercial products for dome automation. I chose Digital Dome Works (DDW), which is an integrated hardware and software product made by Technical Innovations (, the company that manufactured my observatory. DDW includes a control box, a shutter relay box, a number of position sensors, a convenient hand controller, and all the necessary wiring, interface devices, accessories, and software. Installation of DDW is a straightforward task for those who have already built their own observatories.

Once DDW was up and running, all observatory functions were controlled by the in-dome computer, which in turn is controlled by my remote computer. DDW not only enables the user to control the dome and slave the dome to the telescope; it also provides shutdown procedures, safety interlocks, telescope parking features, and a host of other powerful capabilities.

First Light and Beyond

Ironically, first light for my fully automated observatory took place on a beautifully mild late-spring night. My target for the evening was Comet 2002 Q4 NEAT. I began the session by connecting to the in-dome computer over the wireless network with UltraVNC and commanding the shutter to open. I went outside to remove the lens cover from my telescope and performed a quick alignment to establish its orientation. Back inside the house, while I sipped hot chocolate on the sofa next to my wife, Rose, I established a link between TheSky software and the LX200 and focused the scope with FocusAide. All ready to roll, I slewed the telescope to the comet and turned on the CCD camera to compose the photograph and record a sequence of images.

After a successful evening of imaging, I disconnected the link with TheSky and went outside to put the lens cover back on the scope and close the observatory for the night. The fruits of that first night's labor are shown on the facing page.

Encouraged by this success, in the future I plan to install a camera to monitor the status of the telescope, hook up an electronic finderscope, and implement a large-format SBIG CCD camera for long-exposure color images. Someday I would also like to be able to control the observatory over the Internet so that I can operate the telescope when I'm away from home, and so that club members and school groups can access the observatory.

With the basic observatory automation infrastructure now in place, the sky really is the limit.

Robert Capon has been a backyard astronomer and amateur radio operator for more than 30 years. A mechanical engineer, he built his first telescope when he was 16 years old and continues to enjoy building radio kits and working in his observatory. Rob is a guest operator of the 2614-inch Clark refractor at the University of Virginia McCormick Observatory, where he shares his love of the sky with school groups. He can be contacted at
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Title Annotation:amateur telescope making
Author:Capon, Robert
Publication:Sky & Telescope
Geographic Code:1USA
Date:Jul 1, 2005
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