On August 19, 2026, the U.S. Coast Guard updated the official Light List entry for Chatham Light (LLNR 525), changing its published nominal range from 24 nautical miles to 14 nautical miles. The 10-nautical-mile change is a reduction of approximately 42%.

The 24-nautical-mile benchmark dates to the installation of Chatham Light’s powerful rotating aerobeacon in 1969 and remained in the Light List through subsequent equipment changes, including the DCB-224 beacons installed in 1993, until the August 19, 2026 update.

The Coast Guard has explained the 14-nautical-mile specification in relation to the location of the commercial shipping lanes and has said it does not consider the revised range to present a safety issue. NOAA’s current electronic-chart data show that portions of the offshore traffic separation scheme are at or beyond 14 nautical miles from Chatham Light. The Coast Guard is responsible for establishing and maintaining federal aids to navigation, including their published nominal ranges.

Nominal range is a standardized rating based on 10-nautical-mile meteorological visibility. Actual sighting distance varies with atmospheric conditions, the observer and other factors. For that reason, the revised listing and the location of the shipping lanes are useful parts of the navigational context, along with the light’s performance in fog, haze, rain, snow and other conditions encountered off Chatham.

At the time the LED beacon was installed, Coast Guard personnel also said the replacement was expected to provide “the same, if not better, visibility offshore,” and reported that it could be seen more than 25 nautical miles away in clear conditions. Those statements concern observed or expected visibility, while the new Light List entry establishes a 14-nautical-mile nominal range. The distinction is important when evaluating the light’s performance.

The prior beacon was rated at approximately 2.8 million candela, compared with approximately 78,000 candela for the installed LED configuration—less than 3% of the prior rated intensity. Candela is one measure of a light’s output, but it does not by itself determine how the complete system performs for mariners. Beam pattern, flash duration, atmospheric conditions, observer location and background lighting also affect visibility and recognition.

These differences make on-water observation and technical review valuable. Such an evaluation could consider offshore detection, performance in reduced visibility, near-shore conspicuity and the recognizable rotating sweep, while accounting for the design and operating characteristics of both systems.

The community concern also extends beyond the commercial shipping channel. Chatham Light serves local commercial fishermen, recreational boaters and smaller vessels operating near Chatham’s harbor approaches, shifting shoals and near-shore waters. Nominal range, clear-air sightings, degraded-visibility performance, near-shore conspicuity and the recognizable rotating sweep are related but distinct parts of that navigational role.

U.S. Coast Pilot 2 ties these local hazards and routes directly to Chatham Light. It states that Chatham Harbor can be entered east of the light, says that “shoals are constantly shifting in the entrance” and advises extreme caution because of dangerous currents and surf on the outer bar. It locates the unmarked shoal area extending toward Monomoy Island by its position about 2.7 miles south of Chatham Light. For Chatham Roads and Stage Harbor, it lists Chatham Light among the conspicuous landmarks and directs approaching vessels to “steer 063° with Stage Harbor and Chatham Lights in range.” In each instance, the light is part of the Coast Pilot’s description of the navigational setting—not merely a nearby historic feature.

Our focus is a constructive partnership. We hope the Town, mariners, community representatives and the Coast Guard can review the available information together, clarify the navigational objectives for Chatham Light and determine whether any further evaluation or adjustment would be useful.

View the Coast Guard’s current Maritime Safety Information and Light List resources.

View NOAA’s current ENC traffic-lane data, the official U.S. Coast Pilot 1 description and coordinates for the Boston Traffic Separation Scheme, and the U.S. Coast Pilot 2 coverage of Chatham Light, Chatham Harbor, Chatham Roads and the surrounding approaches.