# How do you solve the meridian passage?

## How do you solve the meridian passage?

Meridian Passage – Short Method.

1. Latitude and declination same names but latitude greater than declination: LAT = DEC + (90o – ALT)
2. Latitude and declination same names but declination greater than latitude: LAT = DEC – (90o – ALT)
3. Latitude and declination opposite names: LAT = (90o – ALT) – DEC.

What is meridian passage of sun?

The position at the Meridian passage is the position of the ship when the sun is on the observer’s celestial meridian. That is when the sun is directly (and exactly) above the observer’s head.

How Meridian is calculated?

There are the steps to do the meridian calculation: 1- About 20 minutes before the expected meridian passage time, take a Sun sight with the sextant. 2- At the expected meridian passage time, the Sun will reach the higher altitude for the day, and will appear to hang with constant altitude for a while.

### How do you find the Meridian?

Meridians, celestial and terrestrial, are determined by the axial-pencil of planes passing through the axis of Earth’s rotation. For a location not at a geographical pole there is a unique plane in this axial-pencil through that location.

Why do we solve meridian passage?

A Meridian Passage is a quick method of getting a position line that happens to be your Latitude. This occurs once a day at your local noon, when the sun is directly overhead. In fact, its GHA will be the same as your Longitude. It is a lot simpler to work out, and does not require precise time.

How do you find the meridian?

#### What is meridian Transit?

Quick Reference. The instant at which a celestial object crosses the observer’s meridian. When in transit, an object is at its highest altitude above the horizon and has an hour angle of 0 h. Meridian transit is also known as culmination or meridian passage.

What is the use of meridian passage?

A Meridian Passage is a quick method of getting a position line that happens to be your Latitude. This occurs once a day at your local noon, when the sun is directly overhead. In fact, its GHA will be the same as your Longitude.

How do you calculate local noon?

The Local Noon can be determined from the times when the end of the shadow crosses this circle, before and after noon. This idea dates back to ancient Egypt. In the example above, point B is passed at 11 hours 15 minutes and point A at 13 hours 15 minutes, so the Local Noon is at 12 hours 15 minutes.

## How to determine UT of meridian passage of the Sun?

1. Determine UT of meridian passage of the sun; As the sun approaches the observer’s meridian, the altitude will get larger and larger until it is on the observer’s meridian, which is Local Apparent Noon (LAN) where it reaches maximum alti- tude, then, as is descends, the altitude will get smaller.

When to put sextant on for meridian passage?

This is the time the sun passes overhead at Greenwich, and also the same time it passes overhead your position by your LOCAL TIME (see time zones). Take your Sextant on deck approximately 20 minutes before your local mer pas. Bring the sun down to the horizon, and keep monitoring it. As the sun rises slowly, keep bringing it down to the horizon.

When does a meridian passage occur in the day?

A Meridian Passage is a quick method of getting a position line that happens to be your Latitude. This occurs once a day at your local noon, when the sun is directly overhead. In fact, its GHA will be the same as your Longitude. It is a lot simpler to work out, and does not require precise time. The first step is to find the time of the ‘mer pas’.

### When does a celestial body cross the meridian of longitude?

Meridian Passage occurs when a celestial body crosses the observer’s meridian of longitude and at that instant, it will reach its greatest altitude above the observer’s horizon. The following diagrams will help to explain how the latitude can be calculated from the Sun’s declination and altitude at Mer. Pas. Consider the following diagram:

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