Light pollution degrades astronomical observations in two main ways: sky glow (the diffuse brightening of the sky dome from artificial illumination) reduces contrast between faint objects and the background sky, and direct glare from nearby sources can cause scattered light in telescope optics. Both effects are measurable, and tools for mapping them at any given location are publicly available.
The Milky Way arch visible from a dark site. Wikimedia Commons — CC BY-SA 3.0.
Measuring Sky Darkness: The Bortle Scale
The Bortle Dark-Sky Scale, introduced by John E. Bortle in 2001 in Sky & Telescope magazine, divides sky conditions into nine classes ranging from Class 1 (the darkest skies on Earth) to Class 9 (inner-city sky). The scale is descriptive rather than instrumental, using visible phenomena as benchmarks.
| Bortle class | Description | Milky Way visibility |
|---|---|---|
| 1–2 | Remote dark sky | Extremely detailed, casts faint shadows |
| 3–4 | Rural / rural-suburban | Clearly visible with structure, some glow on horizon |
| 5 | Suburban / semi-rural | Visible but washed out; horizon glow in several directions |
| 6–7 | Suburban | Faint or barely visible near zenith |
| 8–9 | Urban / inner city | Not visible; only bright stars and planets apparent |
Most of Germany falls between Bortle classes 4 and 7 depending on location. Areas reaching class 3 or better are concentrated in low-density regions: the Rhön uplands, parts of the Eifel, the Bavarian Forest, sections of the Mecklenburg Lake District and some Alpine foothills.
How to Check Sky Darkness at a Given Location
The most widely used online light pollution map is published at Lichtverschmutzung.de, which overlays Sky Quality Meter (SQM) data and satellite-derived radiance maps on a searchable base map. Darker colours on the map indicate lower sky brightness in magnitudes per square arcsecond (mag/arcsec²) — a higher numerical value corresponds to a darker sky.
A value above 21.5 mag/arcsec² is generally considered good for visual observing of deep-sky objects. Values above 21.9 indicate exceptional conditions rare within Germany. Below 20.0, sky glow significantly limits deep-sky work.
Designated Dark Sky Areas in Germany
Sternenpark Rhön (Rhön Biosphere Reserve)
The Rhön Biosphere Reserve, straddling the borders of Bavaria, Hesse and Thuringia, was designated Germany's first internationally recognised dark sky place by DarkSky International in 2014. The designation covers parts of the Rhön uplands, a volcanic plateau reaching approximately 950 metres at its highest point. The combination of low population density, restricted industrial activity within the biosphere reserve, and relatively high altitude produces reliably dark conditions by German standards, particularly on the Bavarian side near Wasserkuppe and in the area around Tann.
Public observation points are documented by regional tourism bodies. The Sternenpark operates educational programmes and has worked with local municipalities to reduce unnecessary outdoor lighting within the designated area.
Nationalpark Eifel (Eifel National Park)
The Eifel National Park in the western part of North Rhine-Westphalia was granted Dark Sky Place status by DarkSky International in 2019, becoming Germany's second internationally designated dark sky area. The park covers approximately 110 km² of mixed forest and open upland between the cities of Aachen, Cologne and Bonn — all visible on the horizon as glow sources, but sufficiently distant to allow reasonable sky quality in the interior of the park.
The park administration has replaced outdoor lighting within its boundaries with dark-sky-compliant fixtures and enforces restrictions on event lighting. Several marked trails within the park are documented as suitable for evening and night walking, though visitors planning to observe from car parks or clearings should consult the park's current access information directly.
Bayerischer Wald / Šumava (Bavarian Forest / Bohemian Forest)
The Bavarian Forest National Park on Germany's border with the Czech Republic forms part of a larger transboundary forest complex that extends into the Šumava National Park in Bohemia. The region is among the most sparsely populated upland areas in Germany, with significant tracts of forest providing dark horizons in multiple directions. Altitudes above 1000 metres are accessible by car at certain points, further reducing horizon glow from distant settlements.
No single international designation covers the entire area, but it is well documented on observer forums maintained by the Vereinigung der Sternfreunde (VdS) as one of the more accessible dark-sky options within reach of Munich and Regensburg.
Mecklenburgische Seenplatte (Mecklenburg Lake District)
The Mecklenburg Lake District in the northeastern German state of Mecklenburg-Vorpommern is the most sparsely populated part of Germany. The flat topography means the sky horizon is unobstructed, and the low density of roads and towns produces relatively low sky glow. The area is accessible from Berlin by car in approximately two hours.
Specific observation sites are not formally designated, but the open landscape and numerous nature reserves within the region make it straightforward to find elevated positions away from road lighting. Observers should note that the flat terrain also means cold air drainage at night, which can produce low-lying fog over the lakes during autumn evenings.
Schwäbische Alb (Swabian Alb)
The Swabian Alb plateau in Baden-Württemberg and Bavaria presents an accessible compromise for observers based in Stuttgart, Ulm or Augsburg. While not designated as a formal dark sky area, portions of the Alb plateau away from main roads and larger towns show Bortle class 4–5 conditions. Several amateur astronomy clubs in the region have identified permanent observing pads at rural club sites on the plateau.
Practical Notes for Observing at Rural Sites
Legal access
In Germany, the Betretungsrecht (right of access to forests and open land) applies to forests and most open countryside under state forestry law, but use of a torch, vehicle headlights or parking in forest clearings after dark may be regulated differently by individual Länder. Nature reserve access rules vary, and protected areas may restrict entry after sunset. Always consult the specific reserve's regulations before planning a night visit. When in doubt, established observation points documented by local VdS section groups are a safe starting point.
Seasonal considerations
German winters bring long nights but also persistent cloud cover, particularly in western and northern regions influenced by Atlantic weather systems. Summer nights are short at northern latitudes — true astronomical darkness (Sun more than 18° below the horizon) does not occur at all in June and early July north of approximately 51°N. Autumn and early spring, combined with high-pressure anticyclonic weather, typically offer the most observing hours per clear night in Central Europe.
Equipment for remote sites
Carrying a charged power bank for dew heaters and a star diagonal (for Cassegrain and refractor users) reduces setup friction at unfamiliar sites. A paper all-sky chart avoids dependence on a phone screen that may time out. Red lighting for map reading is essential. Informing another person of your planned location is advisable for solo nighttime excursions in remote forests.
Light pollution map resources
- Lichtverschmutzung.de — German-language light pollution atlas with SQM overlay
- DarkSky International designated places — searchable list of internationally recognised dark sky sites
- lightpollutionmap.info — interactive world light pollution map (VIIRS satellite data)
Sources and further reading
Dark sky designations for the Rhön and Eifel are documented on the DarkSky International website. The Bortle scale description appears in the original article by John E. Bortle published in Sky & Telescope, February 2001. Regional observing site information for Germany is compiled and updated by VdS section groups, accessible at vdsnews.de.