Dark Skies

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Light pollution is a glaring problem, but it's more abstract that other types of pollution that we think of.  It's not like water pollution or trash that produces something undesirable; its impact is what it takes away - our view of the night sky with its natural lights of the stars and the moon.  

In addition to limiting our view of the night sky, light pollution wastes energy, has dramatic ecological consequences, impacts human health, and can reduce night-time safety.  But unlike some of the other pernicious pollution problems that we face, light pollution can be addressed easily and effectively.  Guidance on doing this is based on the Dark Sky principles developed by the International Dark Sky Association (IDSA).  These have been addressed in updates to the Lakeway zoning code which were adopted in 2023.  They are the mechanism which the city is using to promote Dark Sky principles to manage the inappropriate or excessive use of outdoor lighting.    

Dark Sky Transect Credit ESO P.Horalek M. Wallner


Managing Light Pollution to Protect the Night Sky


Lighting is a natural and inevitable result of development; we can't have houses, businesses, parks, and streets active after dark without also having some lighting.  The point is to manage our use of light.  The International Dark Sky Association has defined five principles for responsible outdoor lighting:     

Five Lighting Principles IDA


These are the principles which were followed in developing the Dark Sky provisions to the Lakeway zoning code. The outcome of following these principles will be an improved environment and an improved quality of life without degrading any of our after-dark outdoor activities.  Dark Skies does not mean dark ground; it is simply a more responsible way to manage our use of lighting to have the proper amount of lighting in the proper places at the proper times.    


1. Useful Outdoor Lighting


too bright - lighting that is too bright to help with dark skiesGood lighting on a house for dark skies


Outdoor lighting should be used only where needed.  This illustration from the IDSA shows how lighting the entryway is the useful; the lights which illuminate other places do not serve any useful purpose.


2. Targeted Outdoor Lighting


shielded-vs-unshielded-bad-better-best-2023 IDA


Unshielded light fixtures result in light trespass - light going where it is not wanted - and light glare - light shining directly in your eyes.  

Light fixtures which are certified as Dark Sky Friendly are shielded to prevent light trespass and glare. 

3. Low Level Outdoor Lighting


Recessed Lighting BadRecessed Lighting Good


The intensity of outdoor lighting is an obvious area where light pollution can be managed.  Reducing lighting to only what is needed not only protects the night sky and saves energy, but as this illustration shows, it can reduce glare and improve visibility. 


4. Controlled Outdoor Lighting


Baseball Field 2 am credit stretch shutterstock

No one can question the need for outdoor lighting for sports fields such as this baseball field.  However, this particular photo was taken at 2:00 am - and it is not very likely that this lighting is necessary at that time. 

Controlling the timing of lighting is helpful to reduce light pollution and nuisance.  Lighting curfews as recommended by the International Dark Sky Association specify reducing light by at least 30% or turning it completely off when it is not needed.  This applies to sports, commercial, and residential areas.  


5. Warm-Colored Outdoor Lighting


Color Temperture credit lumistripsThe color of light varies throughout the day, with more yellow colors in the evening and more blue colors towards noon. Colors are classified by their temperature in degrees Kelvin. Colors with a temperature less than 3,000 degrees Kelvin are best for nighttime lighting. Outdoor lighting at the blue end of the spectrum has harmful effects on humans and wildlife by disrupting the natural circadian cycle.