The Urania Society was founded by Foerster in 1888 as a popular scientific society, in Invalidienstraße, and it had an astronomical section with its own observatory .

The main instrument was a 5 meter long, 314 millimeter refractor, built by Carl Bamberg in Berlin which, at the time, was the second-largest refractor in Germany. Gustav Witt used this, in 1898, to discover Eros (asteroid No 433), which he observed to be moving very fast.

The reason for this, it transpired, was that Eros was following an orbit not seen before. All previous asteroids had been orbiting between Mars and Jupiter, but Eros was found to be orbiting within Mars for most of its period, and would actually approach within 23 million kilometers (0.15 AU) of Earth. It was quite close to Earth when Witt had observed it. It was the first asteroid to receive a masculine name.

Witt had discovered Eros in a manner fairly common in Science - i.e. by mistake, when he was really looking for something else, in this case another asteroid, Eunike. Eros has been useful to astronomers for calculating, among other things, the Sun-Earth distance and the combined Earth-Moon mass.

(On the same night as Witt, A. Charlois observed the asteroid from Nice, although Witt was the first to announce the discovery)

About 20 years later, the Observatory was taken over by the University as a training telescope and was destroyed in the Second World War, although various of their instruments ended up elsewhere in Berlin. Also destroyed, in 1944, was the Zeiss-Planetarium am Bahnhof Zoo, which had been opened in 1926.

Eros

• was the 433rd asteroid to be discovered.
• By virtue of its unusual behavior, it was a given a masculine name. Up until then and for a long time after, only feminine names were used.
• It approaches close to Earth about every 40 years, when it becomes the sixth brightest asteroid.
• During its orbit, the brightness varies noticeably due to the rotation of its irregular, elongated shape.
• Its dimensions are approx. 38km x 13km x 13km. This about twice the size of the nucleus of Halley's Comet, but of a similar relative shape. It is one of the largest near-Earth asteroids.
• It rotates on its axis with a period of 5.27 hours
• It was the first of a new class of asteroid - the Amor class. Amor-types orbit within the Martian orbit but not the Earth's.
• Its gravity is such that a person weighing 100 kgs. on Earth would weigh about 50 grams on Eros.

On 17. February 1996 The Near Earth Asteroid Rendezvous (NEAR) spacecraft was launched to reach Eros in January 1999. NEAR encountered Eros in December 1998, but a failure of its motor aborted the planned January 10th 1999 rendezvous. Instead of entering orbit around the asteroid, NEAR could only make a fly-by. It had to circle the Sun, and rendevoused on February 14 2000.

On Monday, 12 February 2001, it touched down on Eros, after transmitting 69 close-up images of the surface during its final descent.

This has just celebrated its centenary having been established in 1896 in Treptower Park by Friedrich Archenhold, although originally he had envisaged a more scientific institution.

He had been involved in a dispute over a nebula he had discovered in Perseus, which some astronomers were reluctant to consider as a separate object from a nearby nebula discovered by Barnard. Therefore he had commissioned a new form of telescope, with a length of 21 meters, exclusively for the photographic investigation of cosmic nebulae.

Attempts to receive government funding were in direct competition to Potsdam's Great Refractor, in which Archenhold eventually lost out and it seems that the telescope was set up "temporarily" in Treptower Park for the great Berlin Industrial Exhibition of 1896 with the express aim of attracting finance. However, it seems that the telescope proved so popular with visitors that the authorities decided to give it a permanent home in Treptower Park as a People's Observatory (Volkssternwarte) - the largest and oldest Volkssternwarte in Germany.

The original building was wooden but it was moved to a new building in 1909. Archenhold remained director until 1931 and was succeeded by his son, Günter. Because they were Jewish, both were relieved of any connection with the Observatory by the Nazis but the observatory officially received its present name on its 50th. anniversary.

Before 1989, the sights of East Berlin were not well publicized (i.e. not well-publicized in western publications), and on the first two occasions that I visited Berlin (when I was less informed about its astronomical heritage), I had twice visited the Zenner cafe on the edge of Treptower Park, unaware that the Observatory was directly opposite, set back a bit from the road. I realised my omission when I came across the East German book Observatories of the World by Siegfried Marx and Werner Pfau (Blandford Press).

The Archenhold Observatory had not changed much from the DDR time (on my last visit in 1993) although I did notice the absence of a former exhibit describing the US Apollo program as a "politically-inspired program" which basically never led anywhere - probably the most accurate assessment of the Apollo program I have ever read. During the DDR-time, there was a room which was used as a public cinema (the Great Hall) - this service has been discontinued but a plaque near the door to the former cinema still reminds us that it was here that Einstein gave his first public lecture on the General Theory of Relativity in 1915. (Note - I believe the observatory has undergone a major re-furbishment recently, so these comments might not still be valid)

The Observatory is open about five afternoons a week for viewing of the museum section, and you can also access the roof and view the main telescope (referred to by a colleague as the "Iraqi Super-Gun" and still the longest refractor in the world) from close quarters. Evening sessions on this telescope are held about once a month, but observing sessions using other telescopes are held once or twice a week. Address Alt-Treptow, 12435 Berlin.

In West Berlin, the Foerster Planetarium and Observatory has been built on the Insulaner, a 75 meter-high mound created from wartime rubble. The observatory is on the top and dates from 1963, the main instrument being the Bamberg telescope rescued from the Urania Observatory. This was joined, in 1991, by a 75 cm. reflecting telescope paid for by the Berlin lottery. The lottery has also provided a library, and is currently paying for the renovation of the Bamberg telescope. The planetarium was added in 1965 and lies at the foot of the Insulaner. In 1987, a modern solar telescope was added, from which images can be projected onto the planetarium dome.

Performances are given about five or six times a week offering a one-hour long show in the planetarium followed by an observing session in the observatory. On the weekends there may be several sessions, one of which could be a multimedia-laser show. The address is Munsterdamm 90, 12169 Berlin.

In the grounds of the Cecilienhof Palace, where the Potsdam conference was held in 1945, there is a small planetarium, seating 50, which holds regular performances. The address is Im Neuen Garten 6, 14469 Potsdam.

Bruno Bürgel, shown at left, was an astronomer of the Urania Society from 1894-1899, after which he became a popularizer of the subject, and published several books.

The former Border Control buildings have been kept, and around 200 meters from these buildings there is a small observatory. At the moment, I am a bit short on details.