The opticThe objectiv is a twolense-cemented fully coated achromat with 63mm aperture and a focal length of 840mm (ratio: f/13.3). There is another (more rare) version, the AS-63/840 lense. This is an airspaced semiapochromatic lens.
Today - in times of bigger apertures - many people say derogatory: "oh what a dinky little thing". This is on the one hand correct but - on the other hand not real intelligent. If you observe under poor conditions (seeing!), you can in the most cases forget bigger apertures, but you will get with that little aperture a sharp - high contrast image! Than, with a little aperture such this, you will perform out in conditions of strong seeing the most scopes with maybe 6, 8 or more inches diameter.
I did make observations with max. magnification until 210x (4mm ortho). With 140x there was nearly zero false color. The optic shows always a clear, high-contrast image. With 210x there is a little bit more falsecolor. But its well tolerable. Here it doesn´t matter, whether I observed the moon, the planets or the brighter deep-sky objekts ... always I got great views!
The diffractions rings are - intra- and extrafocal - total the same. There was no "spreading", no differences. Instead of this - perfect figures. Well done, Zeiss!
At splitting double stars you can see the high quality-level of this optic: I splitted l Lynxidis (1"8 5m9/5m9) without any problems. I saw two starpoints with a little black zone between. Great!
Some years later - now (2018) I´ve owned both versions of this great scope: the AS 63/840 (left) and the C-Version (right)- Telementor: