“THE DOME”

„The dome“ is a universal dome control system that can be adapted to nearly every known dome. It was developed to control the dome of the Sonnenobservatorium Kanzelhöhe that was our home for the Amos I project. Over the course of some months we took a look at the dome control packages from different vendors from all over the world. They all had one thing in common, a price tag of about 10000€. Way too much for our budget. Looking for alternatives we quickly realized that we would have to build our own.

The requirements of such a dome control system were clear from the start. It must allow for continuous rotation of the dome, had to query the telescope position, reposition the dome so that the telescope at any time has a good look out of the slit, work together with a star chart software, be adaptable to different dome types,…..

We finally realized why most of the professional system cost that much. First it is a lot of work, and second they also want to make good money with it. Since they Amos team is composed of people coming from different technical fields we were confident to find a solution. In some weeks of constructing and building in our spare time we came up with a product that satisfied all our needs.

Over 180 hours of development alone went into the control software “the dome” that coordinates and links the telescope, control-electronics and the star chart software “TheSky6”.

The system is continuously expanded with new functionalities. The current version provides the user with 5 extra relays that can be used for example to switch the lights or cooling units, and lots more.

The main part of the system is contained in this single box. The system can be adapted to nearly every existing dome and motor.

How does the dome control work?

The main box is connected with the motor control, simulating the usage of a hand controller. This is the main criteria if an existing dome can be equipped with “the dome” system. The existing motor must provide the possibility to turn the dome left and right by the means of closing a contact.

“The dome” uses an infrared reflex sensor so determine the dome movement by scanning black/white markings that have to be applied to the base of the rotating dome. The system is completed with a magnetic “home-sensor” that is used to determine the basic orientation of the dome.

The dome control system reads the actual telescope position from a sky charting program, in our case TheSky6, an moves the dome accordingly to provide the best possible view for the telescope. When the telescope is slewed to a new position the dome automatically follows to the new destination. Of course this includes the regular telescope move to compensate the earth’s rotation.

The offset positioning

This is a feature that most small dome owners will benefit from. Most amateur domes only have a diameter on 2 to 3 yards, resulting in a very small dome slit. In that case it can happen

very fast that, while the main telescope still has a perfect view through the dome slit, the guiding scope is already looking at the inside of the dome.

To avoid this the dome slit has to be positioned not perfectly aligned with the main scope, but a little bit off to the side. “The dome” allow you to define for each azimuth position how much the dome should be positioned off the perfect alignment with the scope.

Dome drift compensation

To assure a smooth start and stop of a dome and to take strain from motor and dome, a lot of systems are using frequency changers. This and the domes inertia leads to the fact that the dome is still moving a small amount when the power to the motor is cut. “The dome” enables you to compensate for that drift.

Buying the dome control system

Since we already got questions about the system, we decided to sell it for a material and work time compensation. Please understand that we cannot give an exact prize here, since every unit is single and custom build and is therefore subject to fluctuations. “The Dome” will only cost a part of the sum you would have to pay for a commercial version, but since the needed materials are not free and it takes quite some hours to assemble and test it, don’t expect it to be dirt cheap.

The delivered parts are:

- Controlbox
- Software “The Dome”
- IR sensor
- printed documentation

If you are interested in buying our control system, please send an email to

REFERENCES:

1. Sun observatory “Kanzelhöhe”

The first model of “the dome” control was installed in the 3 yard dome.

• Sun observatory of the university Graz       

2. Observatory “Sommerda”

Another installation is the private observatory “Sommerda” owned by Knut Schäffner. There “the dome” is controlling a 2.1 yard dome from Baader.

Knut Schäffner about “the dome”:      

“All I can say is … it works perfectly…. Everything is working as I expected. You did a quality job”

More about his observatory can be found HERE.