Sight Calc 2.0

Sight Calc is a specialized calculator designed for calculating sight reductions using the "Law of Cosines" method. This tool does not rely on Nautical Almanac data, requiring users to calculate the Local Hour Angle (LHA) and declination beforehand, along with determining an approximate latitude. It is tailored for students studying celestial navigation, particularly in programs like the Celestial Navigation courses offered by the United States Power Squadrons®. For those unfamiliar with sight reductions, valuable resources are available from the United States Power Squadrons® at www.usps.org. Specifically, this calculator complements Form SR96a found at www.usps.org/eddept/n/files/sr96a.pdf.

Inputs can be provided in two formats:

• Degrees on the left column and minutes on the right column.
• Decimal degrees (e.g., 44.48833).

Sight Calc will guide users through entering six numbers sequentially:

• LHA (degrees)
• LHA (minutes)
• Latitude (degrees)
• Latitude (minutes)
• Declination (degrees)
• Declination (minutes)

In version 2.0, values can be entered in any order. The calculated values for Hc, Z, and Zn are updated continuously.

Ensure to enter North Latitude as a positive number and South Latitude as a negative number. Sight Calc automatically considers the absolute value of Latitude in the Law of Cosines formula but requires the hemisphere for calculating azimuth (Zn). Similarly, enter positive values for Declination if North and negative if South. Note that this differs from version 1.x of Sight Calc.

If conducting repeated calculations with some unchanged numbers, input only the updated values. To reset all entries at any point, press "C" to clear all data. The "CE" key removes the current entry. Optionally, use the "o" key to convert minutes to decimal degrees, which adds to the degrees field and clears the minutes field, without affecting calculations.

Feedback on bugs or suggestions can be shared at: [email protected].