Testing Vespera in Extreme Conditions: Our Installation at Mont Aigoual’s Subarctic Climate Site
15 Dec. 2025
In October 2024, Vaonis’ Research & Development (R&D) team set out to push Vespera to its limits. Their destination: the Mont Aigoual meteorological observatory, in the heart of the Cevennes National Park, where Vaonis collaborates with the Centre d’Essais Climatiques de l’Aigoual (CECA, Mont Aigoual Climate Research Center).
Located at an altitude of 1,571 m, this site with a subarctic climate is exposed to extreme conditions similar to those found in polar regions. Thanks to a permanent installation, our teams can assess the resistance, reliability, and optical performance of our smart telescopes in an environment far more demanding than what most users will ever encounter.
Why Mont Aigoual?
Perched at 1,571 meters, Mont Aigoual is known for its subarctic microclimate, comparable to that of regions such as northern Canada or Russia. Its weather patterns make it a unique natural laboratory: heavy rainfall, frequent fog, strong winds, harsh cold, and sudden, dramatic temperature shifts.
Located less than two hours from Vaonis’ headquarters, the summit offers an ideal and easily accessible testing ground for our teams.
The mountain range also holds the Dark Sky Reserve label (RICE label for "Réserve Internationale de Ciel Etoilé", in French), awarded to the Cévennes National Park by the International Dark Sky Association in 2018 and renewed in 2022. Spanning more than 3,560 km², it is the largest dark sky reserve in Europe—a major asset for testing the optical quality of our instruments.
Research goals
The two instruments operate exactly like Vespera units intended for the general public. Permanently installed at the summit, they remain continuously exposed to cold, wind, and humidity—an environment far more demanding than typical use, and an ideal setting to observe, day after day, how Vespera responds to environmental stress.
This approach allows us to evaluate:
- Mechanical resistance to extreme weather
- The long-term stability of tracking performance, without additional manual adjustments
- Maintenance of image quality (star sharpness, aberrations, distortions, etc.)
- The aging of materials when exposed to harsh elements.
In practice:
- Freezing temperatures test resistance to cold, frost, and freeze/thaw cycles,
- Strong winds validate long-term stability and mechanical integrity,
- Summer heat combined with sunlight evaluates durability, insulation, and waterproofing,
- Constant exposure to snow, rain, or frost challenges sealing and resistance to humidity and corrosion.
The technical installation
The Mont Aigoual setup includes one Vespera II and one Vespera Pro, both released in 2024 and taken directly from the production line. The instruments are mounted side by side on a permanent rail, fully exposed to summit conditions.
They are connected to a technical enclosure containing a monitoring camera for continuous inspection of the installation and a 220 V power supply. The enclosure is 3D-printed in ASA, a UV-resistant polymer suited for outdoor exposure.
One year on Mont Aigoual: results
After four full seasons of continuous exposure, our teams now have significant insight into Vespera’s behavior under extreme conditions. Only three maintenance operations were required, mostly related to the monitoring and power enclosure, which proved far more affected by the subarctic climate than the instruments themselves.
In autumn–winter 2024, Mont Aigoual experienced an exceptionally stormy and harsh season. While temperatures reached lows of –10°C, it was the wind—with gusts regularly exceeding 100 km/h—that intensified the severity of the climate, plunging the mountain into an icy, unforgiving cold.
In spring–summer 2025, the season was milder and drier than usual, yet still dynamic: persistent strong winds, extreme gusts exceeding 150 km/h, and occasional thunderstorms producing sudden, sharp bursts of wind.
After reviewing the instruments and the images collected periodically, the results are particularly encouraging. Tracking accuracy remained consistent throughout the year, despite gusts, frost, and rapid temperature changes. The image rejection rate—a key indicator of stability and tracking quality—remained steady, with no notable drift over time. Additionally, no measurable degradation was detected on the optics, electronics, or waterproofing. The shells, seals, and internal components showed no premature wear or signs of damage from cold, humidity, UV exposure, or corrosion.
In summary, Vespera has demonstrated outstanding resistance in an exceptionally harsh environment, confirming the robustness of its design and the long-term reliability of its performance.
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M31 captured with Vespera Pro from Mont Aigoual. Original vs processed version.
If you visit the Cévennes Regional Park and the Mont Aigoual observatory—offering stunning views over the massif—take a moment to look through the railings: you might spot our installation (visible but not accessible to the public).
