🔍 Key Concepts

• Apparent altitude vs. geocentric altitude when using a sextant • The meaning of parallax in celestial navigation • Which corrections relate to the observer’s position on Earth vs. the body’s apparent size or shape

💭 Think About

• Which correction deals with the difference between observing from the Earth’s surface and what the angle would be if observed from the center of the Earth? • Which corrections only adjust for the apparent size or illuminated portion of the celestial body, rather than your location relative to Earth’s center? • When you think of the Earth’s center, does that relate more to the position of the observer or the apparent characteristics (size/shape/illumination) of the observed body?

✅ Before You Answer

• Identify which option specifically concerns observer’s position relative to Earth’s center • Eliminate any options that refer mainly to disc size (apparent radius) of the body • Eliminate any options that refer mainly to illumination or visible portion of the body’s disc