Principles of Celestial Navigation

A Day in the Life of a Navigator » Fomalhaut Sight Reduction

Let’s repeat the process for the Fomalhaut observation.

strip form for Capella, Deneb, and Formalhaut, for 0800 UT morning three-star fix

From the Nautical Almanac, the altitude correction for Fomalhaut is -1.9 arcminutes. What is the resulting Ho?

The Ho for Fomalhaut is 26 degrees 55.0 minutes. If you did not get this result, you may wish to work through the calculations again to locate your error. Remember that the index and dip corrections will the same as those used for Capella and Deneb, since we took the observations from the same location at the same time.

What is the computed altitude (Hc) and azimuth (Zn) for Fomalhaut at 0800 UT, 17 July 2018, based on the current assumed position (31° 25.0' N, 054° 12' W)? Recall that the U.S. Naval Observatory has a Celestial Navigation calculator available at

Computed altitude (Hc):

Azimuth (Zn):

Using the USNO Celestial Navigation calculator, you find that the computed altitude (Hc) for Fomalhaut is 27 degrees 08.4 minutes. The azimuth (Zn) is 195.9.

For the star Fomalhaut, you found an observed altitude (Ho) value and a computed altitude (Hc). Based on the numbers, where would you mark the intercept on your plot?

The correct answer is d.

The Ho for Fomalhaut is 26 degrees 55.0 minutes and the Hc is 27 degrees 08.4 minutes. The azimuth (Zn) is 195.9. The intercept should be marked along the azimuth line for Fomalhaut, 13.4 arcminutes away from the GP. Next, Chief Sheedy will demonstrate plotting the three-star fix on the Universal Plotting Sheet.

Please make a selection.