At 2234 ZT on 14 July you are in DR position...

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Question 1 of 2066636eea28f7522a1c51ad41

At 2234 ZT on 14 July you are in DR position LAT 34° 03' N, LONG 150° 16' W, when you observe an amplitude of Saturn. The planet is about one Sun's diameter above the visible horizon and bears 272.1° pgc. The variation is 14° E. What is the gyro error?

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Question 1 of 20

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🔍 Key Concepts

• Amplitude of a celestial body as a check on compass or gyro error • Difference between pgc (per gyro compass) bearing and true bearing • How to apply variation (14° E) and the planet’s true amplitude to find gyro error

💭 Think About

• First, think about whether you are working with rising or setting amplitude and how that affects the sign (N or S, E or W) of the amplitude. • Use your DR latitude and the planet’s declination from the Nautical Almanac to determine its true amplitude at the time of observation. • Once you have the true bearing of Saturn at the horizon, compare it to the observed pgc bearing corrected for variation. Is the gyro reading too far east or too far west of truth, and by how many degrees?

✅ Before You Answer

• Be sure you are using planet amplitude formula correctly for a body low on the horizon, with the correct sign for declination and whether it is rising/setting. • Carefully convert from true bearing to gyro bearing or vice versa, applying variation in the correct direction ("east is least, west is best" for going from true to magnetic). • Double‑check the direction (E or W) of the gyro error: decide if the gyro is reading higher or lower than the true bearing, then match that to the correct choice.

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