Simple streetlight hack could protect astronomy from urban light pollution
A proposed “simple hack” to reduce urban light pollution would make LED streetlights flicker in sync with telescope shutters, letting observatories capture images only during brief dark intervals. Commenters question both the technical and political feasibility of citywide synchronized flicker and highlight potential health and wildlife impacts from 150 Hz pulsing light. Many argue that more effective, broadly beneficial fixes are already known: dimmer and warmer lighting, better shielding to direct light downward, motion- or time-based controls, and in some cases removing or not installing streetlights at all.
Core “streetlight hack” concept
- Thread interprets the proposal as: modulate all LED streetlights at ~150 Hz in sync, and equip telescopes with shutters that open only during the “off” phase, reducing recorded light pollution.
- Works only for imaging devices, not naked‑eye stargazing, and reduces telescope light‑gathering by the shutter duty cycle.
Technical feasibility of synchronization
- Skepticism that entire cities will retrofit fixtures and control systems for astronomy alone.
- Various synchronization mechanisms discussed: GPS timing, power‑grid phase, FM/radio signals, and distributed optical algorithms.
- Multiple commenters note propagation delays, multipath interference, transformer phase shifts, and cost/complexity as major obstacles; GPS‑disciplined solutions are seen as technically possible but not “simple.”
Flicker and health/comfort concerns
- Strong pushback against adding 150 Hz flicker to all outdoor lighting.
- Several people report personal sensitivity to LED/PWM flicker, migraines, “blinding but dark” sensations, and phantom‑array effects during eye or object motion.
- Concerns that even sub‑perceptual flicker can cause headaches, eyestrain, anxiety, and may be worse for animals with higher flicker fusion thresholds (e.g., birds, dogs).
Simpler alternatives to reduce light pollution
- Frequent advocacy for:
- Full cut‑off optics: direct light strictly downward, add shields/shrouds.
- Lower overall brightness; avoid over‑lighting.
- Warmer color temperatures; avoid harsh blue‑white LEDs.
- Turning lights off when streets are empty or dimming aggressively.
- Motion‑sensing streetlights provoke mixed reactions: praised for energy savings, criticized as visually annoying or potentially unsafe.
Spectral choices: LEDs vs sodium and filters
- Many favor low‑ or high‑pressure sodium lamps or yellow LEDs due to:
- High efficiency comparable to white LEDs.
- Narrow spectra that astronomers can filter.
- Better preservation of night vision and less skyglow.
- Criticism that LED replacements are often much brighter, bluer, and chosen to “spend” efficiency gains on extra luminance instead of restraint.
Real‑world practice and local mitigation
- Examples of towns with minimal, warm, downward‑facing lighting described very positively.
- Others report cities adding shields on request and experimenting with dim‑by‑default, brighten‑on‑motion systems, sometimes clashing with brightness regulations.
- At the household level, suggestions include lobbying utilities for shields or timers, and using blackout blinds or sleep masks when city remedies fail.