(A) Shielding. All exterior illuminating devices, except those exempt from this Development Code, shall be fully or partially shielded as required by division (C) below.
(1) FULLY SHIELDED means that those fixtures shall be shielded in such a manner that light rays emitted by the fixture, either directly from the lamp or indirectly from the fixture, are projected below a horizontal plane running through the lowest point on the fixture where light is emitted.
(2) PARTIALLY SHIELDED means that those fixtures shall be shielded in such a manner that the bottom edge of the shield is below the plane center line of the light source (lamp), minimizing light above the horizontal.
(B) Filtration. Those outdoor light fixtures requiring a filter in division (C) below shall be equipped with a filter whose transmission is less than 5% total emergent flux at wavelengths less than 3,900 angstroms. TOTAL EMERGENT FLUX is defined as that between 3,000 and 7,000 angstrom units. It is recommended that existing mercury vapor fixtures shall be equipped with a filter whose transmission is less than 10% total emergent flux at wavelengths less than 4,400 angstroms or shall be replaced. Low pressure sodium lamps are the preferred lamp for minimizing adverse effects on astronomical observations.
(C) Requirements for shielding and filtering. The requirements for shielding and filtering light emissions shall be as indicated in the following table:
Fixture Lamp Type
|
Shielded | Filtered |
Fixture Lamp Type
|
Shielded | Filtered |
Low pressure sodium1 | Partially | None |
High pressure sodium | Fully | None |
Metal halide6 | Fully | Yes |
Fluorescent | Fully5 | Yes2 |
Quartz3 | Fully | None |
Incandescent greater than 150W | Fully | None |
Incandescent 150W or less | None | None |
Mercury vapor | Fully7 | Yes7 |
Fossil fuel | None | None |
Glass tubes filled with neon, argon, krypton | None | None |
Other sources | As approved by town | |
Footnotes: | ||
1. This is the preferred light source to minimize undesirable light into the night sky affecting astronomical observations. | ||
2. Warm white and natural lamps are preferred to minimize detrimental effects. | ||
3. For the purposes of this Development Code, quartz lamps shall not be considered an incandescent light source. | ||
4. Most glass, acrylic or translucent enclosures satisfy these filter requirements. | ||
5. Outdoor advertising signs of the type constructed of translucent materials and wholly illuminated from within do not require shielding. | ||
6. Metal halide display lighting shall not be used for security lighting after 11:00 p.m. (or after closing hours if before 11:00 p.m.) unless fully shielded. Metal halide lamps shall be in enclosed luminaries. | ||
7. Recommended for existing fixtures. The installation of mercury vapor fixtures is prohibited. | ||
(Prior Code, Ch. 4, Art. IV, § 4-118) (Ord. 432-06, passed 6-19-2006)