How do you compute for position of a celestial body?
Zenith distance + True Altitude = 90 Degrees. All we want is True altitude of the celestial body which can be calculated by measuring the altitude of the celestial body by a sextant and applying few corrections to the measured altitude by sextant.
What is ZD in celestial navigation?
The sun crosses 15 degrees of longitude in an hour (360 divided by 24 is 15). Each zone has a standard meridian and the zone extends 7.5 degrees to either side of the standard meridian. Each zone also has a zone description (ZD), which tells the hours needed to correct to GMT.
How is sextant calculated?
To make this correction, multiply 1.7725′ by the square root of your elevation, including the height of your eye, in meters. Subtract this number from your observed altitude (the reading you got on the sextant when you measured the elevation of an object). The ‘ in this formula represents minutes (60ths of a degree).
What is intercept in celestial navigation?
In astronomical navigation, the intercept method, also known as Marcq St. Hilaire method, is a method of calculating an observer’s position on earth (geopositioning). It was originally called the azimuth intercept method because the process involves drawing a line which intercepts the azimuth line.
What is time diagram in celestial navigation?
Time diagrams are simple sketches showing the relationship between time and longitude. They help to visualise the relationships between the local time, Greenwich Mean Time (GMT), and the time associated with the celestial body.
How do you calculate sun sight?
For sun sight, we get first position line in the morning by measuring the sextant altitude and calculating the position line with Long-by-Chron. 2nd position line is by measuring the sextant altitude of the sun exactly at the time of its Mer-pass.
How is sextant altitude calculated?
Dip = 1.77 h², where h= height of observer above sea level in meters. The navigator on the ship’s bridge when observing any celestial body brings the body down to the line of sea horizon and measures the angle of one of its limb. This angle measured is called as the Sextant altitude of the body.
How do you find the GHA and declination of stars?
Find the SHA of the star on the daily page and add that to the GHA of Aries. This gives you the GHA of the star that then can be combined with the assumed longitude to yield the LHA of the star. The declination of the star is found next to the SHA, and there is no d correction.