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With boating season approaching and the first warm-weather walkers already picking their way across Devereux Beach at low tide, a Marblehead resident has built a small, free web tool designed to answer a set of questions that coastal New Englanders ask all year long: When is low tide? What's the moon doing? And when, exactly, is the best time to walk the beach?
The tool is moon.boston, a web app created by Alexander Falk that displays real-time moon phase data, tide charts and a calculated window for optimal beach walking, all tied to the user's nearest NOAA tide station. It requires no download, no account and no login. It runs no advertisements.
"The web app is totally free and not running any ads," Falk said. "It also doesn't require a login or signup or anything."
When a user first opens moon.boston in a browser, the app defaults to Boston — hence the domain name. But it is not limited to the city. Users can tap a location pin icon to pull data for their current GPS coordinates, or use a search tool to find a nearby tide station by name. For Marblehead, Falk said, the recommended station is Salem Harbor, which provides tide predictions closely matched to local conditions. Users who leave the app set to the default Boston station will still get data that is accurate to within a few minutes, he said.
The app's main screen is divided into three sections. At the top, a rendering of the moon displays the current phase along with the percentage of the lunar disk illuminated and local times for moonrise, moonset, sunrise and sunset. Below that, a tide chart plots the day's high and low tides in a visual curve, with precise times and water levels marked for each. The chart pulls its predictions from NOAA station data — in the case of Salem Harbor, station 8442645.
The third section is the one Falk designed with the non-boating public in mind. Labeled "Best Beach Walk Time," it calculates a recommended window for walking the shore based on the hours surrounding low tide, when the most sand is exposed and tidal flats are accessible. On a recent day, for example, the app recommended a beach-walk window of 4:30 to 7 p.m., centered on a low tide of 0.21 feet at 5:51 p.m.
"For landlubbers, it calculates the optimal times for a beach walk around the low tide window," Falk said.
The feature has a practical application in a town where residents regularly walk Devereux, Grace Oliver and the Causeway, all of which are significantly affected by tidal range. Marblehead's tidal swing can exceed nine feet between low and high water, meaning the difference between an easy stroll on packed sand and a narrow strip of cobble pressed against the seawall.
Falk said users can subscribe to a calendar feed that automatically populates their Google Calendar or other calendar system with the recommended beach-walk times for their selected station. The subscription updates dynamically, so the entries adjust as tide predictions are refreshed.
The app can also be added to an iPhone home screen, where it behaves like a native application. A small help icon near the top of the screen provides built-in documentation for new users.
Moon.boston draws its astronomical data from publicly available sources and its tide predictions from NOAA's CO-OPS database, the same system used by mariners and harbor masters. The app does not store user data or track location history, Falk said.
For Marblehead's boating community, the tide chart alone may justify a bookmark. Knowing the precise timing and height of high and low water is essential for navigating the harbor's mooring fields, launching from public ramps and clearing the shallow channel near the Causeway. The moon phase display adds a layer of information useful for night sailing and fishing, as lunar illumination affects both visibility and fish behavior.
Falk, who can be reached through his website at a.fa.lk, said he built the project independently and has no plans to charge for it or introduce advertising. The app is accessible at moon.boston from any web browser.
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