SECTION 1 - INTRODUCTION
A. Purpose. This guide provides information on the maintenance of classical
lenses still in use at various U.S. Coast Guard aids to navigation. The guide
is not intended to be a restoration manual, but instead provide guidance on
the correct procedures for inspecting, cleaning, focusing and stabilizing loose
prisms in classical lenses.
B. History. Many classical lenses are over 100 years old. These lenses,
comprised of brass/bronze frames and ground glass prisms, were imported
from France and England during the mid 1800's to early 1900's. Lenses
either rotate or are stationary. Stationary lenses are typically drum lenses
similar in construction to Tideland Signal Corporation's 300 mm lantern. An
exception is a bull's-eye lens used on a range, commonly called a clamshell
lens. These lenses use either a fixed or flashing 120 VAC, 250-watt or 1000-
watt lamp. Rotating lenses contain an array of bull's-eyes that determine the
flash rhythm, similar to the VRB-25. Fixed 120 VAC, 250-watt or 1000-watt
lamps are also used in these lenses. Since the lenses came with clear glass,
a red or green light required the use of a colored glass cylinder placed over
the bulb, or colored lantern panes. These cylinders, if still in use, are rare, not
easily replaced, and should be treated carefully. If a color sector is required,
colored lantern panes are generally used.
C. Policy. Guidance for the retention of classical lenses for service in an aid to
navigation is provided in the Automation Technical Guidelines, COMDTINST
M16500.8 (series). Compliance with Section 106 the National Historic
Preservation Act (NHPA), the National Environmental Policy Act (NEPA) and
their associated regulations must be completed prior to any major
modification, removal, and/or replacement of a classical lens. Compliance
with Section 106 will require coordination and consultation with the applicable
State Historic Preservation Officer and coordination with other interested
parties (i.e., local government, private local and state historic preservation
groups, etc.). Coast Guard policy on compliance with NEPA and Section 106
of the NHPA is contained in the National Environmental Policy Act
Implementing Procedures, COMDTINST M16475.1 (series). Environmental
staff at the Civil Engineering Units can assist with NHPA and NEPA
compliance requirements. Most of the Coast Guard's classical lenses have
already been removed for restoration and displayed in museums, historic
societies and other appropriate settings. Those lenses remaining in service
shall be maintained in accordance with the guidance in this instruction.
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