IDA recommendations for outdoor light bulbs

According to The International Dark-Sky Association (IDA), there are several types of outdoor light fixtures that are ideal in terms of whether they affect the view of the heavens. Some are better than others in terms of energy consumed and light produced. I’ll outline them briefly here:

• Incandescent/Quatz: As we all know, this is the least efficient bulb out there, but has been used extensively in low-voltage applications, especially in residential settings.
• Compact Fluorescent (CFL): This has become a very popular option for consumers as it is much more energy efficient than Incandescents, however it is not as well-suited for outdoor applications as cold weather can cause them damage. However, in warmer climes, these can make good choices, when properly directed and shielded, for residential applications.
• Mercury Vapor (MV): This is older technology and rather energy inefficient. It has been used in the past in many outdoor applications, and where it is well shielded, can be filtered by astronomical instruments.
• Metal Halide (MH): Has a broader application of white light, which allows for greater color rendering, but which is very difficult to filter out. It is often used for sports complexes and outdoor public spaces where color is important.
• High Pressure Sodium (HPS): Provides a wider wavelength spectrum, so it used where color is important, such as in sport parks and arenas. But this makes them a hazardous for nighttime star viewing.
• Low Pressure Sodium (LPS): The IDA’s preferred choice, this bulb has nearly monochromatic yellow light that can be filtered out by astronomers peering into the night sky. It is extremely energy efficient (probably the most energy efficient light source around) and provides a comfortable wavelength for humans. They are most often used in public spaces, like roadways, walkways, and parking lots, but are also seen in residential areas where security lighting is required.

To further improve any bulb, the IDA recommends full shielding to prevent light from spewing into the night sky. Additional energy can be saved by installing timers and motion sensors where only intermittent illumination is required.