telescope for the Swiss Alps
Author: "Bubendorf" Group
For decades, we four or five people
have been observing in the Basle Jura Alps, where there are really dark
Naturally, the apertures of our portable
telescopes have become increasingly larger over time ... 25 years ago we
started with the construction of 6 and 8 inch models, then we contented
ourselves with 10 to 12 inch models (all DIY projects: Newton; Zerodur;
Optics on portable, tracked frame assembles). Ten years ago, we bought
an 18 inch Dobson and now we have bought a 30 inch model. As trivial as
it sounds: one sees more with a larger aperture ...
We are stationed in the Basle Jura,
where we operate our private observatory.
From June to October, when the Alpine
passes are free of snow, we climb up the pass about three to four times
a year. For any two moonless nights of observing at 2,400 to 3,000 m this
incurs a lot of transportation effort.
Three to four annual "Alps Events"
are not a lot, so we must ensure high-quality optics. For this reason,
we have chosen Alluna Optics for a 30 inch f4.0 device and a secondary
The First-Light on the largest piece
of our equipment has passed: When my friends have been convinced of their
observations, they are no long so loud - they become quiet. With the current
First-Light, some "Wows" can be detected on the faces of the observers
and in the light of a red flashlight an appreciative broad smile can be
For example, the Moon and Saturn:
Sensational resolution, just as is the contrast. We have observed with
the Zeiss-Bino and the Zeiss-Ocular eyepieces. Amazing.
We have done without a lightweight
version intentionally in favour of stability and the best optical quality.
The parabolic mirror (Astro-Sitall) has a diameter of 30 inch (760 mm)
and an edge thickness of 72 mm. Even with observations near the horizon,
the mirror shows circular stellar disks without the slightest sign of astigmatism,
as is often the case with thinner mirrors of this size. Already in intra-
and extra-focal constellations the high quality of the optics can be recognised.
The mirror with the certified ?measured values PV L1 / 10 wavefront and
a Strehl of 96 and a 94% aluminium coating provides wonderfully sharp and
We are completely satisfied.
The "Bubendorf" Group
30 inch Sitall mirror made by Alluna
Adjustment of the Dobsonian telescope