Questions tagged [positional-astronomy]

Questions about positions of objects in the sky, either relative to a fixed coordinate system like the equatorial and ecliptic coordinate systems, or relative to an observer's point of view.

Filter by
Sorted by
Tagged with
1
vote
3answers
100 views

Calculating the position of stars at a given point in time

Is there any particular methods that help us calculate the position of a star at a certain point in time? This question is what I am trying to achieve, but for me, I do not want to use the data ...
5
votes
1answer
251 views

What is the meaning of integrated emission maps for these chemical species?

In the Astrobites article Spectral Line Survey Reveals New Molecules in Two Protoplanetary Disks integrated emission maps depict the spatial distribution of the flux received from each "line.&...
3
votes
1answer
73 views

Where can I find planetary rotational axis direction?

I can find axial tilt of planets easily, but that doesn't specify the direction of that tilt, i.e. planet's rotation axis may be anywhere in circle defined on a sphere by axial tilt value. And I can't ...
1
vote
0answers
77 views

Why is Earth at centre of Celestial Sphere?

Why do we consider Earth to be at the centre for Celestial Sphere ? If so, then how will Sun revolve around Earth ? Doesn't it mean its like the geocentric model ?
3
votes
1answer
548 views

Straightforward derivation of the sunrise equation

I'm looking for a reasonably straightforward derivation of the sunrise equation$$\cos\omega=-\tan\phi\tan\delta$$as referenced in the Wikipedia article here. I've dipped into Astronomical Algorithms ...
1
vote
4answers
129 views
2
votes
0answers
37 views

Question on positional astronomy

I was preparing for an Astronomy Olympiad which has this question: On the evening of an autumnal equinox day Siddhant noticed that Mars was exactly along the north-south meridian in his sky at the ...
3
votes
3answers
334 views

Calculating the position of the Sun

I'm reading the book "Practical Astronomy with your Calculator or Spreadsheet 4th Edition" implementing its formulas with C++. Now, I'm implementing formula 46 "Calculating the position ...
1
vote
1answer
56 views

How precise are Saemundsson/Bennett refraction formulas?

I was trying to reproduce the predictions of the Bennett formula* by physically-based calculations with a model based on a real-life refractivity profile. My calculations based on Table V from ref. 1 ...
3
votes
3answers
157 views

Best Books on Spherical Astronomy

I am preparing for an astronomy olympiad and a good amount of questions in the olympiad come from Spherical astronomy, some of the books ive tried reading were too hard to understand as this topic ...
3
votes
3answers
200 views

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

I'm doing a science olympiad event called Reach for the Stars, and one question that I've encountered provides a star chart and time of day, and you must figure out what month of the year it is from. ...
1
vote
0answers
36 views

Finding Observer Latitude/Longitude - In Simple Terms

I was wondering if someone could explain to me in simple terms how to determine the observer latitude/longitude at a given location. For instance, if an observer is positioned at Cleveland, Ohio, how ...
0
votes
2answers
112 views

A comet orbits the Sun in the same plane as Earth's orbit

If the Earth around the Sun follows a practically circular orbit of radius equal to one astronomical unit, determine its orbital speed in astronomical units per year. If the Earth around the Sun ...
3
votes
0answers
43 views

Secular parallax calculation in Binney and Merrifield

I am now reading Galactic Astronomy (1998) by Binney and Merrifield. In this book at p. 44 there is this formula for calculating proper motion vector: $$\boldsymbol\mu_i = \frac{(\mathbf u_i \times\...
0
votes
0answers
24 views

How to Calculate TRUE geocentric longitude of Moon's Ascending and Descending Nodes [duplicate]

I have already computed the Mean and True geocentric longitude of the planets like Sun, Moon, Saturn, Jupiter etc.. Even I have calculated the MEAN geocentric longitude of Moon's Ascending and ...
1
vote
1answer
48 views

Translating a zenith position to the nadir

What would be the easiest way to translate a zenith position to a nadir on the celestial sphere? For example I have a position from the azimuthal grid in Stellarium; 3h44m32.64s/+50°50'16.2" ...
4
votes
2answers
87 views

Constellation a celestial body is in

Given its right ascension and declination, find out the constellation a celestial body is in. Does anyone know of an algorithm (C#, js) for that? It would read the constellation boundaries (e.g. ...
1
vote
0answers
41 views

About coordinate systems and angle differences

If I want to measure the beam-width of a radio telescope sweeping through a ~ puntual object (the Sun) with a ~ constant flux output when measured: The value measured sweeping in one frame of ...
5
votes
1answer
120 views

Stellar Aberration and Lorentz Transformation

The aberration of starlight is claimed to result from the Lorentz transformation of Special Relativity, but I am having problems to understand this. Assume we have two reference frames $x,y,z$ (the ...
2
votes
1answer
160 views

How to manually locate a certain declination in the sky for a given location? (no sextant available)

Consider this example. I am standing in a flat surface, at latitude X, looking to the equator, in a random day of the year. (For simplicity, let's assume X > 23.5º) I want to find the position of ...
2
votes
0answers
54 views

How to I calcuate observed position of the Sun and Moon using the SOFA C library?

There are a number of answers on here that skirt the topic, but no concrete answers. I currently have an implementation based on "Astronomical Algorithms by Jean Meeus" for stars, moon, and ...
0
votes
1answer
72 views

Confused about the significance of sidereal time

My understanding of sidereal time is that the position of a star will be in the same place 4 minutes earlier the next day. So a 20 days later the star will be 1hr 20 mins earlier. So if the star is in ...
4
votes
3answers
299 views

What are the correct positions or alignment of planets in relation to each other and the Sun, is it vertical center, baseline or completely random

From a lot a illustrations and videos, the planets seem to align in vertical center to each other like this: Is this really true? I like to imagine that the planets are actually in weird alignment to ...
2
votes
2answers
117 views

The Jupiter Effect Book

This evening I have been thinking about the anxiety caused in 1982 by predictions in John Gribbin and Stephen Plagemann 1974 book The Jupiter Effect. I was a teenager in 1982. The planets aligning ...
3
votes
1answer
114 views

What measurements helped us in understanding 'Oumuamua's location and speed?

What measurements helped scientists understand 'Oumuamua's location and speed? I wanted to know how it was achieved and with what accuracy if possible.
1
vote
1answer
82 views

Right ascension, Equinox, Positions Help

I am trying to answer the following question which I slightly understand but need a clearer explanation: What are the times of year to observe an object at X hours of RA at visual wavelength? I am ...
5
votes
1answer
312 views

What are the Mathematical Algorithms/Formulas behind hindu Sunrise and Sunset Calculations?

There are differences between Astronomical Sunrise/Sunset calculation and Hindu calendar Sunrise/Sunset calculations. The astronomical algorithms to calculate the sunrise/sunset can be found over the ...
2
votes
1answer
83 views

Where can I get J2000 epoch initial mean longitudes for all planets and celestial bodies?

I'm following this paper to calculate geocentric coordinates. The authors have provided the initial mean longitude values for the planets (provided in attached table) for 01.01.2000 @ 00.00 UT but I'...
1
vote
2answers
47 views

Converting rectangular to polar coordinates

I'm following the steps in this paper on how to calculate geocentric longitude. In section 3.4.2 it says the Geocentric rectangular co-ordinates of Mercury then are: ...
-2
votes
1answer
71 views

Map planetary eccentricity on a perfect circle? [closed]

What is the formula to plot an eccentric orbit on a perfect circle? I have estimated the full degrees each planet would occupy on a 360 degree wheel (natal chart) but how do I take into account a ...
4
votes
2answers
311 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 ...
3
votes
0answers
82 views

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

I'd like to pull in my awning if my house's shadow has reached a point where the awning has no use any more. The house is almost perfectly aligned in a North-South direction, the garden with the ...
0
votes
0answers
109 views

Position Angle Relative to North

I am trying to find the position angle of a star whose Ra and dec are known. I have already looked at the 'Measuring misalignment between two positions on sky' question and answer, but the answer ...
2
votes
3answers
97 views

Looking for a Solar System Simulator including the smaller celestial body, for macOS

I am researching for a sci-fi novel that will happen in 2136. For this I would like to know specific positions of "smaller" celestial bodies in our Solar System. An example can be the dwarf planet ...
3
votes
1answer
380 views

What is meant by *topocentric* right ascension and declination?

I'm looking up how to convert an azimuth/elevation measurement from a specific location on Earth's surface to right ascension/declination. I'm coming across the terms "topocentric declination" and "...
3
votes
1answer
89 views

Galactic Equator zenith transit

I need to find the two times of zenith passage of the Galactic Equator for a given Earth Lat/Lon on any day between 3500 BC and 1500 AD. Since the Galactic Equator is a line and not a point, I try to ...
2
votes
1answer
154 views

how to calculate distance between galaxies in the distant past

for example, assume there is a high redshift galaxy called "A" with z=6, so how to calculate the distance between us and another galaxy B when the light left the galaxy A? For example, say B has a ...
3
votes
1answer
90 views

Visible satellites real time position API

I'm trying to obtain the azimuth and elevation of all (or at least the majority) visible artificial satellites from a given latitude and longitude. Is there a quite stable API that does that for free? ...
1
vote
0answers
49 views

What book(s) should I read to get started learning about astronomy? [duplicate]

I'm an undergrad software engineer but I also love physics and math. I'm starting to get going in AI/Machine Learning techniques and I'm going to use NASA data-sets to conduct analysis. However, I am ...
0
votes
2answers
282 views

What constellation is closest to the Zenith with RA=12 and Dec =47.6?

I have several options, but I do not know how to calculate which option is closest to the zenith in title. Could you please help me with this? Thank you. ...
4
votes
1answer
740 views

Plotting Astronomical Data Using Python

I have been trying to create a graph which shows the distances between the stars and the earth, yet I could not obtain the desired graph as seen below (click to zoom in): My graph: As @uhoh ...
2
votes
1answer
452 views

Help with Converting Right Ascension and Declination into 3D Vectors

Using the Right Ascension and Declination values from the HYG Database from The Astronomy Nexus: Right ascension is measured in hours and declination is measured in degrees. 1 - Convert right ...
3
votes
1answer
111 views

Latitude of given altitude of Sun

From Question #6 of USAAAO First Round 2018 (1 point) For the following problem find the range in which the answer lies: on the day of summer solstice, on which geographic latitude is the sun ...
6
votes
1answer
729 views

Galactic Coordinate System and distance

If the Galactic Coordinate System is made up of two values, angles of longitude and latitude, how is distance measured? If you have those two values, you get a line from the sun in a certain direction....
3
votes
2answers
262 views

Client-side JavaScript astronomy libraries which are not based on node.js?

Are there any client-side JavaScript astronomy libraries? Almost every library I see appears to be server side for node.js. I realize some node.js libraries can be adapted for client-side use, so I'd ...
2
votes
1answer
318 views

Jean Meeus - calculating moon rise, transit and set times - help isolating error in logic

I've been working my way through the Jean Meeus Astronomical Algorithms book for a few weeks, to implement some of the key algorithms for a personal project. This task has been a little more complex ...
0
votes
1answer
96 views

ra for sun vs stars

There is formula for stars sideral time: $$ra - \arccos(-\tan(dec)*\tan(lat)).$$ where $ra$ - is right of ascension at the vernal equinox. $lat$ = latitude $dec$ = declination Is it applicable ...
1
vote
1answer
130 views

Could someone please explain to me how I can extract velocity component values from Stellarium, for a given planet?

For a project that I am currently working on, I would like to know how one could extract velocity component values ($v_x$, $v_y$ and $v_z$) for a planet from the Stellarium software. The current ...
-2
votes
1answer
44 views

Data in measures paper

What do this data mean please? http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1904AnOBN...8a...1N&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
0
votes
1answer
73 views

Sky from Equator at 8,000 years Before Present?

The Stellarium software allows future views of the sky. I need an online resource (planetarium projector?) that shows pre-historical views, and from the Equator at 8,000 years before the present.