Dark Sky Simulator v2.0

Static, phone-friendly demo of the Dark Sky Simulator for Alachua and Levy counties and their six neighbors (Marion, Gilchrist, Putnam, Clay, Bradford, Union), built to the v2.0 scope in Dark_Sky_Simulator_v2_v3_PRD_TRD.md (Section 0A). It replaces v1's multiplier heuristics with a Garstang single-scattering skyglow model computed offline, real public data, seed economics with provenance, an observatory site-selection engine, and a browser-generated legislative brief.

Every skyglow number is an uncalibrated planning projection. No sky-quality meter data is used, utility streetlight counts are modeled, and Bortle classes are labels on a computed magnitude (PRD 0A.5). The app says so on every screen.

A tour of the app

Live at dark-sky-simulator-v2.vercel.app/dark-sky/. Screenshots are from the 2026-10-19 build (VIIRS mode) at 1440 × 860 unless noted; they are a snapshot, so retake them after visible changes. The left panel has seven tabs (Scenario, Sites, Costs, Observatory, Stargaze, AI, Brief); the map on the right follows the tab, and its layer buttons switch what it shows. How it is built: Technical architecture.

Lighting scenarios and the map

Scenario tab, Sky (scenario) layer. The panel builds a lighting scenario: which fixtures it applies to (by owner and county), then the controls. The map shows the modeled zenith sky brightness for that scenario across the eight counties (mag/arcsec²; yellow is a bright urban sky, dark is close to natural), and the reference sites carry their magnitude and Bortle class. The amber badge in the header is on every screen: all skyglow values are uncalibrated planning projections.

One-click ordinance and the Change layer. The Groveland-style ordinance preset makes every selected fixture (public and private, Alachua + Levy) fully shielded (U0), caps color temperature at 3000 K and dims to 50% from 22:00 to 06:30. Change shows where the sky gets darker (blue) or brighter (red): Paynes Prairie goes from 20.98 to 21.62 mag/arcsec². The Budget card on the map prices the public part (here $26.6M capital, $1.43M a year saved, 18.6-year payback) on the Scenario, Sites, Costs and Brief tabs.

Dark-sky overlay zones. Rings around Rosemary Hill Observatory and Chiefland Astronomy Village apply stricter rules to every fixture inside them, public or private: an LZ0 core (U0, narrow-band amber, motion-only) and an LZ1 buffer (U0, ≤ 2700 K). Shown: the Flagstaff LZ1 overlay preset (3-mile core, 5-mile buffer), about $0.79M in public retrofits.

Viewing time, growth and spectral view. Viewing time switches between the late-night window used for Bortle classes (01:00–04:00) and the evening (20:30–22:30), when sports fields are lit. Extrapolate growth trend adds 1–10 years of growth from the satellite-trained forecast (orange: brighter by 2034 where no ordinance applies). Spectral view redraws the Change layer for one band, here scotopic (night vision), and compares the drop in upward light the eye would see (−23.5%) with what the VIIRS satellite would record (−24.9%): the satellite barely sees the blue in white LEDs, so a retrofit looks like a bigger drop from orbit.

Streetlights layer. Where the model puts public streetlights: modeled fixtures per ~500 m cell, placed along OpenStreetMap roads (roads tagged lit first), and the surveyed points that exist (Gainesville open data in amber, OpenStreetMap in blue). Shown zoomed into Gainesville.

Build mode. A catalog of 17 DarkSky-compliant fixture types in six categories, each card with its spectrum, uplight rating, lumens, watts, installed unit cost (with source) and how many existing fixtures it replaces. Equipping a card updates the sky, the costs, the brief and the clustered install markers on the map. Shown: a full-cutoff 2700 K cobra-head for street lights and a shoebox area light for commercial lighting ($28.0M public, 11.7-year payback; the owners' $3.1M for private fixtures is listed separately).

3D view. Terrain (×3), buildings and every modeled light source at street level under the sky-brightness map: mapped streetlights where they stand, modeled ones spread along the roads of their cell, colored by fixture type. Shown: downtown Gainesville.

Sites and the night sky

Sites tab. Today's and the scenario's zenith brightness at ten reference sites, with Bortle class and the DarkSky Park tier, and an all-sky view of the selected site.

Full-screen all-sky view, the same moonless evening (November 9, 2026, 21:00): downtown Gainesville (18.43 mag/arcsec², Bortle 7, naked-eye limit about 4.3, with Ocala's light dome on the horizon) and Rosemary Hill Observatory (21.69, Bortle 3, limit about 6.5). Stars, Milky Way, Sun and Moon are placed for any date and time; Play runs the night, and toggles add terrain and lights, a sky-glow indicator and a false-color luminance map. Illustrative, not a photograph.

Costs

This is the beginning of the README. Read the rest at the original. Read the full README ↗