Halley Observatory

Halley Observatory


Astro Systems Holland has been involved in the realization of Halley Observatory.

This observatory is one of Holland's most popular public observatories. ASH has designed and built many crucial items of the observatory. ASH, in person of Herman ten Haaf, did also the projectmanagement. On this page you can see some highlights.


It was back in 1984 that I got a phonecall from two 12 year old boys from Heesch. They were both interested in astronomy and wanted their own small observatory. They sent a not to the mayor asking for help and therefore they asked me if I could assist them. I understood their wishes and put many time in finding a small spot in the countryside for a simple small observatory. When a local farmer heard that there would be youngsters on his farmyard at night the enthousiasm was quickly gone. Only one possibility remained and therefore I made a sketch of a simple small building. This also encountered objections from the inhabitants.


The observatory

Once busy I realised myself that it would be a good idea to further "professionalize" the plans into a real observatory for an astronomical association. This idea was already in my head for some time because of my own experience with the observatory in Muiderberg. For that reason I made the first sketch drawing to further arouse the interest in our region.


​This led to the founding of the the Sterrenwacht Halley association.


Because of the good contacts with the community we we obtained a suitable piece of land. A great deal of time was spent on obtaining the neccesary funding. Lateron I met our architect that developed the further evolving plans, supplemented with the many technical wishes I had for an observatory.​

The observatory has two domes. The big one for the public, and the small one for the amateur-astronomers. There is also an option for a third dome, this has been reserved for a solar telescope. Inbetween the domes a a large rooftop terrace.

The domes

For the two polyester domes I had two exeptional thoughts. The large dome had to have a wide opening that could be opened for two thirds. This to allow for a wide field of view and to get rid of the hot air quickly. The small dome is (was) of a very special construction: completely closed, so a relatively large telescope could turn fixed to the dome. Only the open side of the telescope would peek through the hole in the dome.


All neccesary design- and detailing drawings have been made.​

At first the two molds were made. Making these molds was as difficult as the domes themselves. The molds have been constructed on a sturdy frame with a polyuretane foam underground and a polyester topcoating. A steel construction was fixed to the molds to enable a cardan-axle in the center of the domes. A heavy steel rod was fixed to the cardan-axle and a grinding machine was fixed to the end of the rod. With the help of this machine the soft polyuretane foam was ground into the correct radius and lateron the hard polyester top-coating.

The finishing quality of the mold determines the quality of the final result. Because not all parts of the dome have the same form, many trusses were made that had to be put in place in very specific positions. Given the large amount of work it can be considered as the construction of four domes in total.


You can read about these domes in an article in our association magazine.

For the time being a Polarex refractor was put in the dome.


The original design of the main telescope

From the beginning I wanted to design and construct an instrument of very high quality. At that time the APO was introduced and it was clear to me: the observatory would have a large APO refractor. After a large search I came back to Carl Zeiss that had a good name for its APQ objectives.


A 15 cm telescope was the largest, but there would come a 20 cm version. For this reason a 20 cm APQ was ordered. In the meantime I designed a very heavy mount for this telescope. The underside would be made of concrete, the topside of steel. 


Zeiss however stopped with the production of APQ objectives and cancelled our order.


I then went on searching for an alternative and found the Russian company Aries that offered a 25 cm Fluorite Triplet for a lower price than the 20 cm of Zeiss. The orderr was quicly placed. Meanwhile various detailed design and construction drawings were made for the mount.


The design of the telescope was also adapted to the 25 cm. The design was a folded refractor.


About 100 drawings were made of different parts and various parts (like precision encoders, servomotors, servo control, bearings etc.) were ordered and made.

The delivery time of the objective became very long. A lot of correspondence was made with Aries of the developments. Finally the board asked me to stop. The objective was still ordered and at a certain time I got the message that is was finished. Then I cancelled the order myself and received the downpayment. A missed opportunity for Halley. They could have had one of the best amateur telescopes in the world.

The current instruments

At a certain time a CP 180 mount of Astrotechniek was for sale, together with a 30 cm Jones Bird telescope of Opticon. Later the 30 cm Epsilon astrocamera of Takahashi was bought. This was previously owned by the well known astrophotographer Jean Dragesco.

The two telescopes and the mount were extensively modified. After the modifications the mount carries both heavy telescopes with ease. Originally the telescope and mount were dissapointing. A lot had to be changed and that took a lot of time and effort. Even the Takahashi had its limitations that I had to solve.

To properly store all accessories a cabinet has been made with turnable shelves where each accessory has its own place. After being in the large dome for a long the the setup has been moved to the smaller dome, which was originally meant for this telescope.


One can set up small telescopes on the rooftop terrace between the two domes​.