The objectiv is a twolense-cemented fully coated achromat with 63mm aperture and a focal length of 840mm (ratio: f/13.3).
There is another (rare) version, the AS-63/840 lense. This is an airspaced semiapochromatic objective.
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 have made observations with max. magnifications until 210 x (4mm ortho). With 140x there was nearly zero false color. The optic shows ever
a clear, high-contrast image. At 210x there is a little bit more falsecolor. But its well tolerable.
Here it doesn´´t matter, whether I observed moon, planets or the brighter dep-sky objekts, 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 splittet l Lynxidis (1"8 5m9/5m9) without any
problems. I saw two starpoints with a little black zone between. Great!