Questions tagged [ephemeris]

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4answers
347 views

Instantaneous gravity in equation of motion for ephemerides calculation

The equation of motion used for the calculation of orbits of solar system objects (Eq(27) in https://ipnpr.jpl.nasa.gov/progress_report/42-196/196C.pdf ) is formulated in terms of instantaneous ...
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0answers
24 views

How to calculate the point on the globe with maximum magnitude with given Besselian elements and given time for a partial solar eclipse?

I am currently working on improvement of an Android app that calculates solar eclipses. For many days now I have not been able to solve a mathematical problem concerning solar eclipses, so I decided ...
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0answers
22 views

How to easily find out the periods when a planet gets into retrograde?

How to easily find out the periods when a planet gets into retrograde? for eg I want to find out all the periods, in last 5 thousand years, when mars goes into retrograde in Sidereal Scorpion? Is ...
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1answer
88 views

Can I calculate the apparent position of comet NEOWISE C/2020 F3 from a topographic position with Skyfield?

I'd like to get .altaz(next_several_weeks) of this comet from Skyfield and .separation_from() other planets. It reads the JPL ...
4
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2answers
228 views

Understanding the JPL Ephemerides

I'm working on an animation that replicates our Solar System. I know this has been done before, but I'm working on something that requires me to make one myself. With that being said, I'm having a ...
2
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1answer
46 views

Determining moonset time from Nautical Almanac

I have recently learnt to determine moonrise and moonset times using the Nautical Almanac, as part of my maritime navigation course. I have a query regarding the determination of moonset times. I will ...
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1answer
92 views

Implementing the VSOP-2000 Ephemeris

For a project I'm doing, I need to implement the VSOP-2000 ephemeris for the Moon. However, unlike VSOP-87, there is little to no documentation online on how to use the data. For example, here is the ...
3
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1answer
67 views

How accurate should sun\moon ephemeris be for calculating eclipses?

I am writing a program to simulate eclipses for about -2000 to 6000. My question is, how accurate does my ephemeris for the sun and moon have to be to get a decent accuracy for eclipses? I currently ...
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1answer
20 views

Is it correct to say vertical conjunction?

This question is related to this one: Are we seeing a conjunction these mornings? Last Feb 27, the a reporter said that, the day before, at sunset, Venus and the Moon were in vertical conjunction. Is ...
2
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1answer
154 views

Precision in the measurement of the distance to the Sun

How precisely can the distance to the Sun be measured? Wikipedia says the distance to the Moon can be measured upto millimeter precision. But Wikipedia article on distance to the Sun says only about ...
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2answers
84 views

How can I calculate 27 tropical/solar year since my birthdate?

Let's say I was born on 27th November 1993 at 03:15:15 AM. Is there any way I can calculate exact 27 tropical cycle since my birthdate/birthtime. What date and what time it will be after exact 27 ...
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1answer
51 views

L2 point ephemeris (celestial mechanics)

I'm a master student and I am trying to get the L2 ephemeris for some calculations in my master's project. It was kinda hard to find a file with the L2 ephemeris, but once I found it, I tried the next ...
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2answers
3k views

Why does the Earth have a z-component at the start of the J2000 epoch?

When I go to the NASA HORIZONS webpage https://ssd.jpl.nasa.gov/horizons.cgi and ask for the VECTOR coordinates of the Earth on 1 January 2000, it tells me that Earth has the following coordinates ...
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0answers
71 views

How to choose between methods to resample/interpolate ephemeris state vectors? Are there recognized techniques for orbital data?

I have ephemeris data for state vectors of a satellite in a J2000.0 coordinate system. This data is already filtered and cleaned. The data sample rate ranges between 1 second and 60 seconds, and I ...
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1answer
1k views

How to calculate the ground track of the Moon's position on the Earth's surface?

I would like to project the Moon's position on to the surface of the Earth, starting with its position expressed as Right Ascension in degrees. I know that the declination of the Moon corresponds to ...
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1answer
609 views

How to get ephemeris data for location?

How can I obtain ephemeris data which fits to a specific location? Differently phrased: I need ephemeris data of satellites which orbited a specific location. Is there a document where I can look up ...
2
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1answer
262 views

Calculating right ascension for two planets and their separation using python

I am experimenting with the Python library PyEphem for astronomy, and I am trying to recreate/understand some of the basic calculations there. There is a function called separation that, given two ...
5
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1answer
222 views

Why is the time between equinoxes different?

The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse. Since an ellipse, by definition, is symmetrical with respect to the foci, ...
3
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1answer
131 views

Predicting accurate time of local sunrise in mountainous area?

Is there any software which will tell me accurately at what moment any part of the solar disk will become from a specific point on the ground taking account of terrain. I feel like Google maps should ...
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1answer
194 views

Ephemeris data mismatch between Nasa Horizonz and Astro.com

I have tried to compare the Ephemeris data from Nasa's Horizons with ephemeris tables from astro.com. And they do not match. Example: Date: 22th of July 2018. Body: Mars. Time 00:00 UT Horizons: 309 ...
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1answer
141 views

What are the problems that need to be taken in consideration when trying to find planetary position by using jpl ephemerides?

I'm currently trying to determine the position of the sun and the moon from jpl ephemeris DE200 which is referred to the dynamical equator and equinox of 2000 and uses tdb time. I am using the j2000 ...
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2answers
73 views

What is the official classification and naming system of objects in the universe(, or what would my URI look like)?

Poetic human centric approach: Universe/Laniakea/Virgo/MilkyWay/Sol/Earth/Humans/AndreasT Little bit more technical: ...
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1answer
99 views

Which kernel does HORIZONS get the Geometric Albedo from?

I am new to using SPICE and the SPICE Toolkit. My goal is to extract body radius, albedo, and distance from the sun of a number of solar system objects. The tools provided by NAIF are great and I ...
4
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1answer
76 views

Where to get rate of change for calculating ephemeris from JPL Horizons

I have a working implementation of Schlyter's method for calculating the Sun's position. I would like to know how Schlyter got the 3.24587E-5_deg in the following calculation for Mercury. ...
2
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1answer
94 views

JPL Horizons - how to format TLIST input times for Email query?

I am trying to get a list of all of Mercury's Perihelia and Aphelia over a period of multiple decades. For each event I need X,Y,X and Vx,Vy,Vz data. Knowing the time of the first event it is easy to ...
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1answer
100 views

Determination of High-Accuracy Distances of Terrestrial Planets from the Sun

I understand how in olden days the Sun-Planet distances were estimated using:- (i) measures of planet orbital periods ($T$) from analysis of observations over several centuries; (ii) Kepler's 3rd Law $...
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1answer
430 views

Difference in Ephemerides Position:- PlanEph 4.2 (VSOP87) vs JPL Horizons (DE431)

I have obtained the hindcast position of Mercury relative to the Sun for the epoch 2000-Jan-01 12:00:00 using two methods: PlanEph ver 4.2 (Dos-based) and JPL Horizons DE431 (online). The two methods ...
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1answer
239 views

Finding Asteroid Geocentric Longitude and Latitude

I started using the software that comes with Jean Meeus book Astronomical Algorithms. I am now using the updated code from naughter(dot)com/aa.html. I am able to calculate the heliocentric longitude ...
2
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1answer
899 views

where to obtain ephemeris data for geodesy satellites?

Is anyone aware of where one can obtain ephemeris data in Geocentric Celestial Reference Systems (GCRS) coordinates for a geodesy satellite such as LAGEOS (It doesn't really matter which mission)? Or, ...
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1answer
490 views

Converting Earth Moon Barycenter coordinate to Geocentric coordinate

I have Earth Moon Barycenter coordinate (J2000) generated from VSOP2013 in Astronomical Units, ...
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1answer
330 views

How to visually chart HORIZON ephemeris

I'm trying to build a 3D model of the Sun, Earth and Moon in in Javascript (using Three.JS, which relies on x,y,z coordinates for all objects) in order to simulate the Aug. 21 eclipse. I've ...
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1answer
697 views

calculating lunar phases

Given a date, I'd like to return the lunar phase. Jean Meeus's Astronomical Algorithms book and the many packages like PyEphem that make use its algorithms provide ways to calculate when a primary ...
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1answer
330 views

How Can I Interpolate Ephemerides?

I have two ephemerides for orbital elements—that is, each contains $a$ (semi-major axis), $e$ (ecc.), $i$ (incl.), $\Omega$ (long. asc. node), $\omega$ (arg. of peri.), $\tau$ (time of peri.), $T$ (...
4
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2answers
161 views

JPL DE Documentation

I'm currently trying to write a C++ library that makes accessing binary data from a JPL ephemeris file easier. So far I sifted through the web, trying to find a good and thorough documentation about ...
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0answers
60 views

Is there an English translation of the Parisian Alfonsine tables

I'm interested in the Alfonsine tables published in Paris in the 1400s. I know there is an English translation of what survived of earlier Alfonsine tables from Castile, but that's not what I'm ...
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1answer
3k views

How to calculate the current distance between two planets [duplicate]

I'd like to add a feature to one of my apps that calculates the current distance between the Earth and Mars (or any other planet, for that matter). My google searches have led me to statistics of ...
3
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1answer
61 views

How can we map masses orbiting the outer Solar System by determining the orbits of planets and smaller objects?

Neptune was discovered 170 years ago with the help of observations of Uranus' orbit. A great demonstration of the scientific principle for its time. Recently, Earth and cis-Lunar based radio ...
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0answers
51 views

Did the Juno mission locate Jupiter at the same precision as Saturn (4 km)?

Juno's low perijove should be great for measuring Jupiter's gravitational effect on Juno's orbit. Cassini together with VLBI has measured Saturn's location to within 4 km. Will Was Juno be able to ...
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1answer
238 views

Exactly what in Saturn has been located to within 4 km precision?

Saturn has been located with fantastic precision thanks to Cassini and VLBI. The location of the 120,000 km diameter giant planet (when defining the 1 bar pressure level as its surface) is known to ...