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30-inch Dobsonian 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 places.

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 mirror.

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 seen... 
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 crisp images. 

We are completely satisfied.

The "Bubendorf" Group
 
 

parabolic mirror 30 inches
30 inch Sitall mirror made by Alluna Optics

Dobsonian telescopes
Adjustment of the Dobsonian telescope

30 Inch Dobson

 telescope mirrors

 

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