Instruments
The Goal
The Arizona desert can get quite cool on winter nights. Moreover, I do my spring, summer and fall viewing in Colorado at elevations of 8,000 feet and above, where it is frequently downright frigid! (See “Star Ranch” ). My goal was to make my skywatching sessions a little more comfortable by remotely controlling my telescope and the CCD camera from the comfort of my living room.
To achieve this, I would need several things:
- A telescope with computerized “Go To” capability
- A CCD camera to be my remote “eye” for imaging
- Remote control software for telescope pointing.
1. The Telescope
The telescope is a Celestron Ultima 2000. I purchased the telescope in the spring of 1998 from Dean Koenig of Starizona in Tucson, Arizona. I was very much a novice … so much so that I was concerned that I might not be able to locate two known stars necessary to align the scope. However, I quickly learned the night sky well enough to have many enjoyable evenings with this fine instrument.
It was some of my early teeth-chattering sessions from my Colorado viewing sites that lead me to quickly consider remote control. To my delight, I discovered that not only was the Ultima 2000 a great “beginners” instrument, it also had the flexibility and power to grow with me as I gained more experience, and it allowed me to address my remote control aspirations.
2. The Camera
In November, 1998, I purchased the Celestron Pixcel 237 (later converted to SBIG ST237A) CCD camera. The very first night I acquired some satisfying images in the f/10 (eyepiece) position. The next night I was even more delighted with the deep sky objects I imaged in the f/1.95 (prime focus) position.
The camera dramatically expands the observing possibilities of the Ultima 2000, and it is the electronic “eye” necessary to make remote observations through the telescope. The camera consists of the camera head, a CPU camera control unit, and appropriate cabling. The camera CPU connects to the parallel port of the computer via a 25-pin connector. The camera CPU connects to the camera head via another 25-pin connection on the back of the CPU unit.
The camera software, “CCDOPS” (Santa Barbara Instrument Group) can control the telescope position through a 6-pin telephone cord running between the camera CPU and the telescope AUX port. This feature is used to fine tune image framing prior to exposure, and to automatically make tracking adjustments during lengthy exposures.
3. Telescope Control
“The Sky” Astronomy Software, Version 5.0, Level IV (Software Bisque) is a great tool for exploring the sky and selecting objects for a viewing session. In addition it has the capability of controlling the Celestron Ultima 2000 remotely to direct it at the desired objects. This was the final critical piece necessary for me to implement my plans for a “Living Room Observatory”.
“The Sky” communicates with the telescope through a special serial cable, which has a standard RS-232 connector on the computer end, and a telephone type plug on the other, which plugs into the hand controller on the Ultima 2000. This cable is available through Celestron. Click for cabling details…
Making It All Work Together
In theory, I now had all the parts necessary for remote telescope control and observing. However, due to cable length, the distance between the telescope and my computer was limited to just a few feet … not enough to achieve my goal of a comfortable observing environment. I would have to lengthen the cables. No one seemed to know exactly how much I could extend the cables and still get reliable communication between the devices. It was experiment time.
In addition to the cable length question, I found the documentation for both the camera and “The Sky” software somewhat lacking with regard to controlling the Ultima 2000. However, with the help of Dean Koening at Starizona, the good folks at Software Bisque, and some trial and error on my part, I successfully had the system working together indoors in a couple of evenings of experimentation.
After verifying system operation with the provided cable lengths, I then added extensions. I ended up with a total of 37 feet of parallel cable between the camera CPU and camera head, 50 feet of 6-wire telephone cord between the camera CPU and telescope AUX port, and 60 feet of 4-wire telephone cord between the computer serial port and the telescope hand controller. I anticipated communication problems, but I have had none. The system is functioning perfectly even with the cable extensions.
Aligning the Ultima 2000 and Establishing a Link with “The Sky”
The last step in achieving remote telescope control is to establish a link between the Ultima 2000 and “The Sky” software. This undocumented procedure is critical for a successful alignment and link. After aligning the telescope with two known stars using the hand controller in the normal way, it is necessary to select the “Catalog” mode on the hand controller menu before attempting to link “The Sky” with the telescope. If the hand controller is left inany other mode, a link cannot be established.
A Final Refinement … “Permanent” Installation
Using the above system turned my image gathering sessions into a living room easy chair operation. However, the setup was still a pain. I had to set up my tripod, polar align the telescope, and drag out the assembly of cables that I was guaranteed to trip over in the dark at least once. I had visions of a permanently aligned telescope pier and underground cables, which would allow me to simply turn the system on and start using it.
I described my goals to a friend who is a wizard in the machine shop. The next thing I knew I had the “Timperley Telescope Pier.” This thing is a monster! The one inch thick solid steel base is about 250 lbs by itself. I was provided with a variety of hardware to anchor and level the pier in concrete if necessary. However the massive base made anchoring unnecessary … a fortunate thing, since digging a hole in the hard pack desert clay is nearly impossible. I simply exposed the clay surface, smoothed and precisely leveled it and stood the pier in place.
The top of the pier was designed with an adjustable mounting plate, which allowed the plate to be pointed roughly north without manhandling the entire pier.
I then installed the Celestron wedge on the mounting plate, mounted the telescope on the wedge, and spent the time necessary to achieve precise polar alignment using the fine tuning adjustments on the wedge. Then I tightened everything down.
To bury the cables, I dug a shallow trench, fitted the cables into ¼” foam pipe insulation, and covered the cables with dirt and landscape rock.
The result is a clean, semi-permanent installation. My setup procedure now consists of mounting my scope onto the pre-polar aligned wedge, plugging in the cables and turning on my computer. A quick two-star alignment and focus adjustment and I am imaging the Arizona sky.