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Navicula

Universal, Altitude, Equal and Unequal hours

The navicula seamlessly merges practicality with form, with each element of the dial coalescing to contribute to the visage of the "little ship."

The hull of the ship features a set of parallel hour lines situated beneath a pivoted mast which is used to set the date. Able to slide up and down the mast is a latitude collar. This dual-axis motion of the mast and collar allow the dial its universal range.

On the dial's reverse can be found a seasonal hour quadrant and shadow square.

The navicula occasionally features a gazetteer of cities with their corresponding latitudes inscribed on the back of its mast.

These dials are adaptable for a wide range of latitudes, making them incredibly useful to travelers. The one caveat to this level of universality is that their operation is complex and requires a certain level of understanding that may be beyond someone simply looking for a convenient way to tell the time quickly.

This dial functions under the same principles as the Regiomontanus dial, though was developed independently.

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How to use

1. Tilt the mast so that the indicator on its lowest point points to the current date.

2. Slide the latitude collar up the mast and fix it so that the plumb line hangs from the latitude of use.

2. Hold the dial vertically so that the thread hangs parallel to the hour scale, then tilt it up, causing the thread to fall against the second date scale on the far right edge of the instrument.

Keep tilting the dial up or down until the string indicates the current date on the leftmost side of the date scale. Clamp the thread in this position.

3. With the thread oriented to the current date, slide the thread's bead onto the 12th hour line.

4. With the bead set, let the string fall loose. The dial is now ready to be used.

5. Tilt the dial up so that the shadow of the bow's sighting hole falls on the second sight atop the stern. With this done, the dial is now pointing directly at the sun (the front of the dial is the edge farthest from the date scale used to set the bead).

6. Take note of where the string is positioned on the hour scale and clamp it down. The position of the bead on the hour scale indicates the current time.

 

The top labels of the hour scale are used when taking a reading before noon, and the lower labels are used for the afternoon.

7. To determine civil time, add the appropriate longitude correction and equation of time correction (more information here). If applicable, add one hour during daylight saving time.

Overview of Instrument
Outdoor Demonstration
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