In 1995 something very special happened: A mirror with a diameter of 20cm fell into my arms. The history of this mirror is quite complex, there are three persons involved: my father and two collegues of him at Leitz (optical company). College I made a mirror by himself in the 1960ties. He wanted to build a compact telescope so he made a central hole into the mirro. Yet, he tried to make it a paraboloid. One day he lost interested in it and so he gave it to my father. Back then I was not born let alone an astronomer. My father wasn't an active astronomer, too, so he gave the mirror to collegue II. The mirror rested somewhere for another 15 years when the collegue II finally heard of my interest in astronomy. Then the mirror came to me and within 6 months I was using it :-)
So I embarked on a special journey: Making my first telesckope. I wanted it to be Dobson with a truss rod tube. Well, I miscalculated the center of mass and had to add some weight of lead to the mirror box. That's where its name comes from: lead is "Blei" in german.
Oh was I waiting for the first light! And ... such an disappointment! The light gathering power was great compared to my 11cm telescope but the images of the stars didn't look right. Together with Stefan Schuchhardt I checked the mirror in a Foucaulttest and we noticed one thing: there was a zone right around the hole. What to do now?
I gave up using a standard mirror cell. Normally, the mirror rests on a few points and is kept in place by a kind of belt. I changed it. The mirror rested on a ring made of rubber and a screw "looked" through the hole in the middle of the mirror. With a nut and a wooden plate I was able to apply pressure to the mirror and especially to the zone ... and guess what? The image improved. Stefan named the telescope "Newton-Newton" for quite obvious reasons.
| Type: | Newton |
| Optics: | 20cm f/6 |
| Mounts: | Alt-Az, sliding bearing |
(c) by Frank Leiter