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 Venus Evening Star or Morning Star?
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Category Archives: Astro Navigation Topics
The Demystified Astro Navigation Course Unit 6
UNIT 6 – Calculating zenith distance and azimuth at assumed position. We can use sight reduction tables to calculate the zenith distance and azimuth at the assumed position or else we can use the traditional method of making the calculations … Continue reading →
The Demystified Astro Navigation Course – Unit 3 Part 1
Unit 3 Part 1 – Altitude and Azimuth The Azimuth is similar to the bearing in that it is the angle between the observer’s meridian and the direction of the celestial body. However, whereas bearings are measured clockwise from north … Continue reading →
Calculating the Distance Between Meridians of Longitude Along a Parallel of Latitude.
At the Equator, the distance between meridians of longitude is 60 n.m. (or 60.113 to be precise). However, as we move north or south away from the equator, we find that the distance between them decreases as they converge towards … Continue reading →
Posted in astro navigation, Astro Navigation Topics, celestial navigation, navigation

Tagged astro navigation, celestial navigation, navigation
Altitude Correction for Parallax
As shown in the following diagram, the observer measures the altitude in relation to the visible horizon from his position at O on the Earth’s surface. So, the observed altitude is the angle HOX. However, the true altitude is measured from the … Continue reading →
Posted in astro navigation, Astro Navigation Topics, astronomy, celestial navigation

Tagged astro navigation, celestial navigation, navigation
Altitude Correction for Dip
Dip. A correction has to be made to the sextant altitude to allow for the height of the observer’s eye above the horizon; this is known as Dip. Consider the diagram below: O is an observer’s position on the Earth’s … Continue reading →
Posted in astro navigation, Astro Navigation Topics, celestial navigation, navigation

Tagged astro navigation, celestial navigation, navigation
Altitude Correction for SemiDiameter
An adjustment for semidiameter is one of the corrections that may have to be made to the sextant altitude in order to calculate the True Altitude. Corrections For The Moon’s SemiDiameter. The point on the Moon’s circumference nearest to the … Continue reading →
Posted in astro navigation, Astro Navigation Topics, astronomy, celestial navigation

Tagged astro navigation, astronomy, celestial navigation
Converting GMT To GHA
Greenwich Mean Time (GMT) is the local mean time anywhere on the meridian of Greenwich. In other words it is the Local Hour Angle of the Mean Sun on the meridian of Greenwich. Since the Greenwich meridian is used as the … Continue reading →
Posted in astro navigation, Astro Navigation Topics, celestial navigation

Tagged astro navigation, celestial navigation, Equation of time, navigation, Time
The ‘Where To Look’ Method.
To determine the altitude and azimuth of a celestial body, we could make calculations by using mathematical formulae; we could compute them with the aid of sight reduction tables; we could use star globes and star charts or we could … Continue reading →
Jupiter’s Retrograde Motion
Jupiter moves across the sky in a very predictable pattern, but every now and then it reverses direction in the sky, making a tiny loop against the background stars – this is Jupiter in retrograde. The following diagram shows that, … Continue reading →
Finding Stars and Constellations, Part IV
This post continues the series Finding Stars and Constellations. Boötes The Herdsman If we take a line from Alioth to Alkaid in the Great Bear and extend that line in an imaginary curve for about roughly three handspans … Continue reading →