stretch
  • Member for 2 years, 8 months
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  • Columbia, MD, United States
Local mean time & Solar Noon
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You mentioned "Equation of Time," so you should be able to answer many of your questions yourself. You understand the problem. The Wikipedia article will tell you more than you want to know. ...

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Sunset and sunrise formulas adopted by IAU
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Answering your main question: if you were to correct the text in the book you would word it differently, deleting all the mentions of parallax except for a single sentence saying there is such a thing ...

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Horizontal and equatorial coordinate systems
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You don't choose a coordinate system. If you're navigating you take sights to get horizontal coordinates, then look up the equatorial coordinates, and knowing the time, calculate your position. If you'...

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TESS sector of observations in RA/DEC vs lat/long
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2 votes

Neither projection has anything to do with Earth's motion. They just show different ways of defining locations on the celestial sphere. The locations of stars are more or less fixed on that sphere. ...

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Can I derive the position of my house's shadow from sun altitude?
1 votes

Your original thought, that you could just specify the Sun's altitude was correct. The shadow will reach the end of your patio at the same altitude of the Sun every day. Considering where I think you ...

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What time and where on earth is the latest solar noon?
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Made me look. On October 15 Portugal was still observing daylight saving time. The local time for continental Portugal was one hour later than UTC and the country is about 8 degrees west longitude, ...

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Star map decode to location
2 votes

Your star map shows the right ascension and declination of the stars. The right and left edges of the map are the 0 (and 360) degrees right ascension (or sidereal hour angle). The Earth rotates, so ...

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Questions about Celestial Navigation
2 votes

You can do it all with arithmetic: no algebra or trig. The Navy publications you saw are designed that way. Starting with the Nautical Almanac: there are different treatments for the stars and for the ...

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Given a location and a time on another planet, how do you determine how many hours before or after sunrise is it there?
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https://www.giss.nasa.gov/tools/mars24/ has a link to an application that may be what you're looking for.

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Are all the steps below leading this approximation for a zero-shadow latitude correct?
1 votes

The commonly used first approximation for the latitude of the Sun's GP is $23.5 sin(\frac{2d \pi}{365.25})$,where d is the number of days since the vernal equinox. If your sine lookup is for degrees ...

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Why is the sun not directly overhead at noon on the March equinox at N 0° 0' 0.00" E 0° 0' 0.00"?
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35 votes

It never is exactly, directly overhead on the vernal equinox at the Greenwich meridian. You know that it happens on different days in different years so it must be happening at different times on ...

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Calculate viewing times at a location - when location has an obstruction
1 votes

You won't find a reference that tells you the altitude of an object when it passes your meridian. That altitude depends on your latitude. Saturn for all this year is near 18 degrees south declination, ...

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Gravitational influence of other planets?
-1 votes

Actually the gravitational tug from a nearby planet is stronger than that from a nearby person. Venus is the planet that comes closest to us - it's 42 billion meters away when it's between us and the ...

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Axial Tilt One or Two Angles
4 votes

The Earth's axial tilt is expressed as a single number because it's just an angle. It can be considered to be the angle between the plane of the equator and the plane of Earth's orbit, or the the ...

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Using parallax to find distance to the moon
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Using user38308's approach: First, find the distance between you and your friend, knowing lat/long of your positions. You need to solve a spherical triangle with vertices at the north pole and the ...

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Calculating the position of the Sun
3 votes

You shouldn't add 2010 because the date of interest is before 2010. None of the days in 2010 were in the time between 27 July 2003 and 0000 1 January 2010. Similarly, the time after 27 July 2003 until ...

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Angle the Sun makes with the horizon during sunset
5 votes

Short answers: It's not just angular velocity of Earth's rotation times elapsed time. You do need to factor in declination and latitude. Using your representative date and observer location: The ...

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rotate right ascension, declination based on delta time
1 votes

The declination won't change. The right ascension will increase by about 15 degrees per hour or 0.25 degrees per minute. The actual number is closer to 15.04 degrees per hour of time: (366.25 * 360)/(...

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What is the rate of change by day for a given right ascension?
1 votes

On the vernal equinox, first day of spring, the zero reference point for right ascension was directly overhead at 9:37 UTC this year. It has been advancing westward at a rate of 360/365.25 degrees per ...

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Conversion of Moon's Celestial Position (RA and dec) to Horizontal Coordinates
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There's no difference in the calculations, but the Moon, Sun, planets don't have more or less fixed right ascensions and declinations like all the stars. The site you linked seems to only work for ...

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How fast can you determine latitude referencing only the sun?
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2 votes

You can do it in one or two days. You'll know compass directions roughly, which is good enough, by observing the Sun's east-west path. You measure the Sun's altitude at meridian passage on two ...

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Calculate exact date and time from position of the sun - 88° degrees
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1 votes

You could try successive approximation using your Python library. Put in your best guess date/time and keep adjusting it to get 88 degrees.

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Is **Voyager I’s** reduced data transmission rate as described in [this article][1] because of the distance or because its transmitter getting slower?
1 votes

Transmitters don't slow down as they age. Red shift isn't involved, at all. As a transmitter gets further away the signal at the receiver gets weaker, so it's deliberately slowed down. Data channel ...

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How can you determine the date using nothing but a star chart from the day and the time?
2 votes

The way the star chart is drawn, the points labeled 1 and 3 are on the celestial equator, the 0 degree declination reference. The tip-off is that a line between them passes through Orion, the top-...

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Lunar Inclination
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0 votes

It is tabulated, and available online in several places. One of them is the Nautical Almanac at thenauticalalmanc.com. It has the position of the moon for every hour this year and a number of past ...

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Solar Azimuth angle Derivation
1 votes

What I think you're trying to do is workable, but approximate. You first find the Sun's geographical position (GP), the point on the Earth where the Sun is in zenith at the time of the observation. ...

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Diameter of the moon from the diameter seen in the telescope
1 votes

A telescope wouldn't have a single lens, I'm sure you know. If you were to use the setup in your diagram, focusing the image of the moon on a flat surface, you could find its diameter with the method ...

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Right Ascension of North Celestial Pole
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5 votes

The north celestial pole doesn't have a right ascension. It's like the north terrestrial pole not having a longitude. Asking for it creates an exception. In any case, the RA of a point, other than the ...

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Calculating the time a star is at my local meridian based on its right ascension
1 votes

The Equation of time has nothing to do with stars. It's just a measure of the irregularity of the Sun's apparent position, which varies over the course of a year. As planetmaker points out, the Sun's ...

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How to determine zenith coincidence from date time data sets
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1 votes

What @JohnHoltz says is correct. If you need a cook book formula for 2020: The vernal equinox starts the year at 100.1167 degrees greenwich hour angle (GHA). Every second after that it's 0....

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