Gerard Ashton
  • Member for 6 years, 7 months
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  • New England
Where is 0 R.A.?
3 votes

0 RA is the direction from the center of the Earth to the vernal equinox. You've already imagined the plane in space created by projecting the equator into space. Now consider the plane formed by the ...

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What is the axial tilt of a planet measured relative to?
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3 votes

If you look at the Astronomical Almanac for the year 2011 as an example, in the table at the top of page E3, you find two measures of axial tilt. The third column is the declination of the planet's ...

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Local Standard Time Meridian - LSTM (Units)
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2 votes

In a time, the word "standard" normally means the civil time, recognized by the government in the place of interest. I'm not sure about other countries, but in general conversation in the USA, "...

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How to calculate a planet's current position within the solar system
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2 votes

Buy Astronomical Algorithms 2nd ed. by Jean Meeus. It is published by Willmann-Bell Inc. If you buy it direct from the publisher, you will get a corrected printing with all errata up to August 10, ...

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Mathematics for Conversion between ICRS and AltAz
1 votes

Sean E. Urban and P. Kenneth Seidelmann, Explanatory Supplemement to the Astronomical Almanac 3rd ed. (Mill Valley, CA: University Science Books, 2013). This book provides a detailed treatment, and ...

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Is the equinox Sun always at the same zodiac sign in the ecliptic belt?
1 votes

Terminology is critical. As mentioned in other answers, precession causes the equinoxes (the points where the ecliptic intersects the celestial equator) to move from one constellation to another. For ...

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How did Meeus calculate equinox and solstice dates?
1 votes

I obtained a more recent (2002) book by Meeus, More Mathematical Astronomy Morsels, published by Willmann-Bell. Chapter 63 is about the Gregorian calendar and the vernal equinox. It contains ...

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Calculating Local Sidereal Time
1 votes

The USNO page refers to USNO Circular 163 which in turn refers to a paper by Aoki et al. and one by Moyer. These papers explain how the expressions created by Simon Newcomb at the end of the 19th ...

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How do GHA of vernal equinox, GHA of astronomical object and RA relate?
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1 votes

I'm using the Explanatory Supplement to the Astronomical Almanac 3rd ed. as a reference. The glossary tells us that Greenwich Apparent Sidereal Time (GAST) is the GHA of the true equinox of date, that ...

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Calculate Local Sidereal Time
1 votes

A highly authoritative source is Explanatory Supplement to the Astronomical Almanac 3rd ed., Urban & Seidelmann, 2013. Chapter 1 gives the introductory explanations, without all the refinements ...

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Finding the suns position in the sky anywhere at any time
1 votes

There are many resources that will let you compute the position of the Sun in a coordinate system with its center at the center of the Earth. The answer will be an angle above or below the equator, an ...

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Simulating location of the moon
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1 votes

The US Naval Observatory has a web page which lets you print a table of moonrise/moonset times for any location, together with twilight times. If you use this approach, you would print the data and ...

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What should I consider in order to accurately calculate the moon phase?
0 votes

The procedure for finding the phase of the Moon is outlined in The Explanatory Supplement to the Astronomical Almanac, University Science Books, 3rd ed., p. 507. The annual "Astronomical Almanac" ...

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Calculate Dec and RA of a star from Euler angles and GPS data
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0 votes

Obtain from the publisher Willmann-Bell the book ''Astronomical Algorithms'' by Jean Meeus. If obtaining elsewhere, be sure to obtain the 2nd ed. with corrections as of August 10, 2009. The equations ...

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