Shipley Farms · Vilas, Watauga County, North Carolina
The dark on 115 acres
Artificial light and the galaxy contribute almost exactly the same amount to the sky over this farm. The ridge that costs us an hour of morning sun also hides every streetlight in Boone — which is why we are darker than the ridgetop towns around us.
- Zenith brightness magnitudes per square arcsecond
- Bortle class rural sky, Milky Way visible
- Artificial vs natural times the natural night sky
- Boone’s share of the glow
- Centroid 36.2466° N, 81.7504° W
- Elevation 2,896 ft / 883 m
- Tract 115 acres / 46.5 ha
- Basis World Atlas, 2015 satellite data
How dark it actually is
Measured against the 2015 World Atlas of Artificial Night Sky Brightness, the artificial glow over this farm is millicandela per square metre — times the natural brightness of a starlit sky.
Together they give a zenith brightness of magnitudes per square arcsecond, which is Bortle class : a rural sky. The Milky Way is visible and structured overhead; the glow of towns is obvious along the skyline; the faintest detail an experienced observer would see at a genuinely pristine site is gone. Each magnitude on that scale is a factor of 2.5 in light, so the gap between this farm and Charlotte — magnitudes — is a factor of about in how much light the sky throws back at you.
Night sky brightness, the farm against its neighbours
Zenith brightness in magnitudes per square arcsecond — higher is darker. The dashed line is the natural sky with no artificial contribution at all.
The farm is darker than Blowing Rock and darker than Banner Elk, and about level with the summit of Beech Mountain — which is 700 m higher and surrounded by ski lighting. Being low in a valley is worth more here than being high on a ridge. That is the opposite of how altitude works for rainfall, and the reason is the same one: what matters is what the ground around you blocks.
The ridge hides the lamps
Boone sits km away at bearing °. The town is 130 m higher than the farm, so its lights subtend only degrees above the farm’s own level. The skyline in that direction stands degrees up.
Not one streetlight in Boone is visible from this tract. What reaches the farm is the scattered dome above the town, not the fixtures themselves. Two things follow. Shielding fixtures so they throw light down rather than sideways would genuinely help here, because the sideways light is all the farm ever receives. And a hilltop a mile away, with a clear line of sight to the same town, would have a markedly worse sky.
The skyline, and where the light comes over it
The same horizon profile computed for the sunlight page, from USGS 3DEP elevation. The spokes mark the bearing of each major source of artificial light, scaled by its modelled share of the glow. Where a spoke is short and the grey mass is thick, the ground is doing the work.
Hover a bearing, or focus the chart and use the arrow keys, to read the ridge behind it.
Where the glow comes from
To attribute it, every incorporated place within 320 km was treated as a point source scaling with its population, and the brightness was propagated with Walker’s law. Both the coefficient and the distance exponent were fitted against the atlas at sample points across the region rather than taken from a textbook.
The fit lands on an exponent of , explains of the variation in log brightness, and reproduces this farm’s atlas value to per cent.
| Source | People | Distance | Bearing | Share of glow | Ridge |
|---|
Boone is a quarter of it
One town of people, km away over the ridge, supplies per cent of the artificial light in this farm’s sky. Charlotte, forty-seven times larger and seventeen times further, supplies per cent.
But most of it is not local
Adding up by distance band, per cent of the modelled glow comes from beyond 75 km — the Piedmont cities, the Tri-Cities, Knoxville, Asheville. No amount of shielding in Watauga County reaches that light.
How much that split depends on one fitted number
Share of the farm’s glow by distance band, at four values of the propagation exponent. The fitted value is the left-hand group; Walker’s classic 2.5 is the third. They give opposite answers, so the fit has to earn its place.
Why the fitted exponent, and not the textbook one
It matters completely, so it is worth being explicit. At the fitted exponent of , Boone is per cent of the glow. At Walker’s classic exponent of 2.5, Boone would be per cent and the far field almost nothing.
The reason for preferring the fitted value is not elegance. An exponent of 2.5 reproduces the observed brightness field across this region with an R² on log brightness of — it does not merely fit worse, it fails. The fitted is the only value in the range tested that reproduces the field at all. UNKNOWN A shallow exponent is also what you would expect if the model is quietly absorbing sources it does not list — highways, industry, settlements under 500 people. The direction of the conclusion is sound; the exact percentages are not precision figures.
What this cannot tell you
The measurement is eleven years old
UNKNOWN The World Atlas is built from satellite data collected in 2014 and 2015. In the decade since, this region converted most of its street lighting to LED and added considerable development around Boone. Published work finds sky brightness over the United States rising at a few per cent a year, with citizen-science estimates far higher.
The real sky over this farm in 2026 is very likely brighter than , and nothing on this page measures by how much. A sky quality meter left on site for a year would settle it for a few hundred dollars, and would be the single most useful thing anyone could do to this page.
Other limits
UNKNOWN Zenith only. Every brightness figure here is for straight overhead. The sky toward Boone, low in the east, is considerably brighter than the number suggests, and the sky to the west considerably darker. The page does not model the full dome.
DESIGN The attribution is a model. Walker’s law is an empirical envelope, not physics. It knows nothing about shielding, lamp spectrum, terrain or aerosol. Fitting it tells you which town dominates; it does not give precise percentages.
No instrument has ever measured sky brightness on this tract.
How the numbers were built
Artificial brightness is read from the Falchi et al. 2016 atlas at the tract centroid, converted to magnitudes per square arcsecond with the standard photometric zero point, and compared to the natural sky value of 0.174 mcd/m² that the same work uses. The 30 arc-second cell is about 750 × 920 m, so it is the farm rather than a region.
Source populations are U.S. Census estimates; the horizon is the same 3DEP profile computed for the sunlight page. The licence on the atlas permits neither redistribution nor commercial use, so no map derived from it appears here — only point values, used to check a model built from public census data.
Sources
- Night sky brightness
- Falchi, Cinzano, Duriscoe, Kyba, Elvidge, Baugh, Portnov, Rybnikova & Furgoni (2016), The new world atlas of artificial night sky brightness, Science Advances 2(6):e1600377, doi:10.1126/sciadv.1600377; dataset doi:10.5880/GFZ.1.4.2016.001. Point values only; the dataset is licence-restricted and no part of it is reproduced here.
- Glow sources
- U.S. Census Bureau Vintage 2024 subcounty population estimates and 2023 Gazetteer place centroids.
- Terrain
- USGS 3DEP elevation, delivered through the National Map ImageServer. Independent horizon check: European Commission PVGIS 5.3, SRTM-derived.
- Position
- Tract centroid as used throughout this site’s weather pages.
Shipley Farms, 1699 Linville Creek Rd, Vilas, NC 28692. Five generations in Watauga County since 1872. All measurements on this page describe the 115-acre home tract at 36.2466° N, 81.7504° W.
No shortcuts since 1872