Selecting Bulbs 

LED Light Bulb Guide for Dark Skies

Does the bulb screw into a socket? Y/N

• If yes, does the base look like a standard size light bulb?

• If yes, the base size to look for is “E26” or “Medium”

• If no, the smaller base is “E12” or “Candelabra” and the large base is“E39” or “Mogul”

• If no, see base options at the end of this document.

Pick the shape of the bulb:

PAR shapes  - pick the diameter of the bulb:

Is the light fixture exposed to the weather (not under a roof or a canopy)? Y/N

• If yes, the bulb must be labeled for “wet location” outdoor use or indoor/outdoor use.

• If no, the bulb must still be labeled for “damp location”. Wet location bulbs can also be used.

Is the bulb directly exposed to the weather – like a floodlight fixture socket? Y/N

• Replace the fixture with a shielded fixture. Exposed bulbs create the most light pollution.

Is the fixture open at the bottom? Y/N

• If no, the bulb must say “Suitable for enclosed fixtures”.

Is there an existing dimmer?

• If yes, then bulb must be labeled as “Dimmable”

• If no, consider adding a dimmer switch to improve control and reduce energy use.

Is the light fixture 10 feet or less from the ground?

• If yes, then look for bulbs that are labeled 1000 lumens or less and/or install a dimmer switch.

• Bulbs brighter than 1000 lumens at low mounting heights produce “hot spots” and excess contrast which reduces safety.

• If no, then consider the consider the size of the area the fixture is intended to light and refer to the illustrations at the end of this document for guidance.

Pick a bulb that has a color temperature label of 2700K or less to create a warm and inviting appearance, to reduce glare and sky glow and to minimize negative environmental impacts.

• Find this label on the box for the lumen output and color temperature you want: