Predict spring and neap tides by hand. For anyone curious why Montauk's tides swing bigger some days than others. Rotate the two-lobed tide arm around the fixed Earth hub through the four raised stops at 0, 90, 180, and 270 degrees, lining the Moon marker up with or across from the fixed Sun arrow to compare spring-tide alignment against neap-tide quadrature.

How the alignment works. Turning the two-lobed tide arm around the fixed Earth hub carries it past four raised stops at 0, 90, 180, and 270 degrees. Lining the Moon marker up with the fixed Sun arrow marks spring-tide alignment; setting them at a right angle marks neap-tide quadrature, the same qualitative swing behind Montauk's real tide range, framed here as a prediction to work out before you check it.

How the four pieces fit. The Montauk base arrives with its center post and domed Earth hub fixed in place, plus three loose pieces: the two-lobed tide arm, the Moon marker, and the Sun arrow. The arm fits over the center post and pivots around the Earth hub; the Moon marker seats on the arm's outer lobe, and the Sun arrow sets into the base at its own fixed position.

Deep ocean navy, instrument gold. Finished as a display instrument: the circular base is deep ocean navy and the tide arm, Earth hub, Moon marker, Sun arrow, and raised stops are instrument gold, a two-tone scheme built for the shelf, not just the desk. Layer lines run fine and even, with clean, precise seams where the post, arm, and markers meet.