Ilmu Pelayaran Astronomi (Part 1 - SEXTAN)

Summary

This educational video script delves into the world of celestial navigation, focusing on the sextant—an essential tool for maritime use. It explains the sextant's purpose, types, and components, while detailing its operation and common errors. The script guides viewers on how to measure celestial objects' altitudes for navigation, emphasizing the sextant's importance even in modern times when technology might fail. It concludes with an invitation for questions and comments, highlighting the need for understanding this traditional skill.

Takeaways

• 📚 The script is an educational video about celestial navigation using a sextant, a tool for measuring the altitude of celestial bodies to determine a ship's position while navigating.
• 🔭 Sextants are optical navigation instruments that can measure the altitude of the sun, moon, stars, and other celestial bodies to ascertain a ship's location.
• 🌟 The video discusses two types of sextants: the traditional one's sextant and the more modern tromol sextant, with the latter being more flexible and widely used today.
• 🛥 Despite advancements in technology, sextants are still essential on ships as a backup navigation tool in case of technological failure or errors.
• 🔍 The sextant consists of several parts including the index mirror, horizon mirror, index glass, horizon glass, micrometer drum, and other components that work together for precise measurements.
• 👁️ The index mirror reflects the celestial body's light into the telescope, while the horizon mirror allows the observer to see the horizon and the reflected light of the celestial body simultaneously.
• 🔄 The micrometer drum is used for fine-tuning the measurement by adjusting the angle to achieve a precise altitude reading of the celestial body.
• 🧭 The sextant is used for various purposes including obtaining celestial body altitudes, measuring horizontal angles between visible objects, and vertical angles for hydrographic surveys.
• 🔬 The video explains the importance of proper sextant usage, including checking for obstructions to the sun and horizon, adjusting for index error, and ensuring the sextant is correctly positioned for accurate readings.
• ⚖️ The process of reading a sextant involves noting the degree and minute measurements from the micrometer drum to determine the exact altitude of the celestial body.
• 🚫 The video also covers common errors that can occur with sextants, such as sea refraction, perpendicularity, and parallelism, and provides methods to correct these errors for accurate navigation.

Q & A

What is the main topic discussed in the video script?

The main topic discussed in the video script is the study of celestial navigation, specifically focusing on the use of the sextant.

What is a sextant and what is its primary purpose?

A sextant is an optical navigation instrument used to measure the altitude of celestial bodies above the horizon to determine the position of a ship during navigation.

What are the two types of sextants mentioned in the script?

The two types of sextants mentioned are the 'sextant onew's' and the 'sextant tromol'. The latter is more commonly used due to its flexible system compared to the former.

Why is it important for sailors to learn how to use a sextant even with modern technology available on ships?

It is important for sailors to learn how to use a sextant because, despite the availability of modern technology, it can fail or malfunction, and having the ability to use a sextant ensures they can still navigate in such situations.

What are some common errors that can occur when using a sextant?

Some common errors include 'sheterror', which is caused by the horizon glass not being perpendicular to the plane of the sextant, 'perpendicularity' error when the index mirror is not perpendicular to the frame, and 'parallelism' error when the index mirror and horizon mirror are not parallel to each other.

What is the function of the index mirror in a sextant?

The index mirror in a sextant is used to reflect the celestial object, such as the sun, to the horizon mirror, which then reflects the light to the telescope for observation.

What is the purpose of the micrometer drum in a sextant?

The micrometer drum in a sextant is used to make precise measurements of the altitude of celestial bodies by rotating it to adjust the position of the index mirror until the celestial body is exactly on the horizon line.

What is the significance of the horizon mirror in a sextant?

The horizon mirror in a sextant allows the observer to see both the celestial body and the horizon line simultaneously, which is crucial for determining the altitude of the celestial body accurately.

How can the 'sheterror' be corrected when using a sextant?

To correct 'sheterror', the observer should position the alidade at the zero point and hold the sextant at an angle, or rotate the micrometer drum knob around the zero-degree mark while observing the celestial body.

What is the process of reading the altitude measurement from a sextant?

The process involves noting the degree from the index arm's position and the minute from the micrometer drum's position, which together give the altitude of the celestial body in degrees and minutes.