Questions tagged [declination]
Questions regarding one of the two main angles(coordinates) of an object perceived by an observer on Earth.
61
questions
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1answer
55 views
What's the Right Ascension & Declination of Galactic Left & Galactic Right?
For the purpose of being able to align my model to the galactic plane, I want to know the directions of the galactic center, anti-center, north, south, left & right.
This gives me the answer for ...
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1answer
43 views
At what rate does the right ascension and declination of a planet, the sun and moon change per hour?
I'm currently building a web app and am getting the RA's and Dec's of solar system objects based on date and time chosen by the user. Then using the gmst for 0 hours of the date, the app calculates ...
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3answers
214 views
How to calculate the nodal precession range of the Moon with respect to the celestial equator?
In the span of 18.6 years there is nodal precession of the Moon with respect to the ecliptic of 360 deg. But if we consider this precession with respect to the equator, we will find (unless I'm hugely ...
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1answer
50 views
At what time of the day of autumnal equinox the Sun's equatorial coordinates reach max value?
I'm trying to solve this task:
At what point in time of autumnal equinox day, at sunrise or sunset will
a) the declination of the Sun
b) the right ascension of the Sun
reach the maximum value?
I'm ...
7
votes
1answer
314 views
Is the Ra/Dec of Alnitak in Orion's Belt known to be correct?
I've obtained right ascension / declination information about some of stars in the Orion constellation from a few different sources and imported this into an open source video game I'm making. Using (...
3
votes
1answer
667 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 ...
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1answer
61 views
Sun right ascension and declination at date with different values on different calculators and also with my implementation
I'm reading the book "Practical Astronomy with your Calculator or Spreadsheet 4th Edition" implementing its formulas with C++.
Now, I have implemented formula 47 "Calculating orbits ...
3
votes
2answers
150 views
What is the rate of change by day for a given right ascension?
I am writing a small Julia app to get my feet wet in that language. And I want to calculate "what's up tonight" based on a table of right ascension (RA)/Dec(lination) (table of stars), a ...
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1answer
60 views
RA and Dec of Near-Earth-Objects
I'm new to the forum.
This might be a silly question. I had a confusion about how RA and Dec are calculated. So, from what I understand RA is the angle made by the position vector of an object(...
3
votes
1answer
53 views
What is the longitude of the winter solstice for the various planets?
I am looking for data showing the longitude at which the various planets in the solar system reach their winter solstice. Where could I find this data?
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1answer
163 views
How can you find the distance to a galaxy using right ascension and declination?
For example, Galaxy NGC 3689 has the right ascension of 11:28:11 and declination of +25:39:40.0. Using these values, how can we find the distance to the galaxy? If it helps, its radial velocity is ...
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2answers
201 views
Solar Azimuth angle Derivation
I tried posting this on math stack exchange to no avail so I thought maybe it's more relevant here :
I know a similar question has been posted here before but no links to any mathematical derivations ...
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1answer
192 views
How to convert Proper Motion in RA & Dec to Galactic Coordinates
I'm trying to parse stellar data in the GAIA 2 release to galactic coordinates and am struggling with the velocity component. I've tried following online documentation and papers, but end up with ...
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votes
1answer
170 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 ...
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vote
1answer
44 views
How can I find a date when the moon at zenith over a specific spot on the equator?
I would like to know when the moon is directly overhead 0° S, 166° E. Are there any websites that will show me any of those dates?
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votes
2answers
596 views
What is the area of the Summer Triangle?
I'm pretty sure spherical trigonometry comes into use here but I don't know how to calculate the area. I'm pretty sure Vega, Deneb, and Altair's declination and right ascension figures need to be ...
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vote
1answer
106 views
A Noob's question on declination
The Sun's position at noon is perpendicular to the local x-y plane on the equator during equinox. So the declination of Sun on that day is 0. Today the declination of Sun is close to 23, can this be ...
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1answer
495 views
Correct units to use while plotting mollweide projection of sky chart with RA and Dec values, matplotlib
I am trying to plot a mollweide projection of a sky chart in Python using the matplotlib package. I am using the RA and Dec values from a database containing all stars in Hipparcos, Yale Bright Star, ...
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votes
1answer
440 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 "...
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1answer
498 views
RA and Dec of the Sun at J2000
I'm in the somewhat awkward position of asking something that, despite me thinking there should be hundreds and hundreds of web pages and datasets showing this particular value, I've been unable to ...
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1answer
845 views
how to plot sky map like www.nakedeyeplanet.com with dates tags with planetary motion path
I am curious how to plot planetary motion star chart with date tags like on www.nakedeyeplanets.com by Martin J. Powell.
Is there any way to generate images similar like that. What software should ...
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1answer
178 views
How to compute Ascension / Descension cycle of the Moon
I am struggling to find out an information about how to determine ascending/descending cycle of the Moon.
I can find from this source and a bunch of others, that Moon begins to descend when reaches ...
2
votes
1answer
531 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 ...
2
votes
1answer
82 views
How can I check if we can observe a certain star (given its equatorial coordinates) from a certain location on Earth (given its DMS coordinates)?
I am given the equatorial coordinates of a star (e.g. Sirius has RA: 6h45m8.9s and Dec = -16°42'52.1"). Now my question is: can we observe this star from a specific location on Earth (e.g. from ...
2
votes
1answer
707 views
Planetary Declination and Axial Tilt
Is it a coincidence that Earth's axial tilt and maximum declination are both approximately 23 degrees?
Mechanically speaking, do planets physically cross the Solar equator, or is declination due to ...
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2answers
1k views
How do you draw the ecliptic on a celestial sphere sketch?
I don't really understand how it's drawn on sketches of the celestial sphere. At first I thought it goes through east and west, but it does not. How do you know where to draw it?
Example from Roy and ...
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2answers
1k views
How to calculate solar coordinates. (Right Ascension, Declination, and ultimately the Altitude and Azimuth of the Sun)
As the title says I am trying to calculate solar coordinates of the sun for a given location and time. I have spent many 10's of hours on this without success so I will sincerely appreciate help on ...
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1answer
4k 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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vote
1answer
2k views
How to calculate declination of Moon?
Is there any way to calculate declination of Moon for any day?I'll subtract inclination of Earth on the ecliptic from the result. I'll get Moon's the shortest angular distance from Sun.
Thanks for all ...
3
votes
1answer
254 views
Moon equatorial coordinates
It took some effort, but in the end, I successfully calculated the geographical point of the Sun. I assumed that I could do the same for the Moon.
My plan is:
Find RA and declination of the Moon
...
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vote
1answer
558 views
Precise declination of Moon
The moon follows 5.14 deg inclined path. the ecliptic and the Moon's path coincide are called 'nodes', and they travel around the ecliptic in a period of 18.66 years.
Once every 18.66 years, the ...
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0answers
81 views
Where on Earth can moon rise on the meridian?
Somewhat related to this my picture showing only diurnal motion but Moon—seen from Earth—has a rapid motion with respect to the inertial celestial sphere, unlike stars and planets. Its motion relative ...
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1answer
351 views
How to calculate the time and distance of closest approach of a star?
How should I approach this problem?
A star has a motion on the sky of 0.78 arcsec/yr in declination and 1.33 arcsec/yr in right ascension.
Calculate the velocity of the star in the plane of the sky ...
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vote
1answer
134 views
angles on the celestial sphere
This is a somewhat simplified, and drawn / formulated in a manner more targeted to astronomy, version of a diagram and a question that I've also posted in math.stackexchange.com.
In the diagram below ...
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votes
1answer
410 views
Presenting / printing Right Ascension and Declination values
Are there any standards or established practices on how to write / represent Right Ascension (RA) and Declination (DEC) values in the sexagesimal format?
I have seen all of the following. E.g. for RA:
...
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2answers
382 views
When does a star rise with the sun?
Problem: Suppose an observer's latitude is 45 S and a star's RA/DEC is
3h15min/41S. On what date will the sun set with the star.
I have been stuck on this problem for a while.
I found out that the ...
4
votes
3answers
548 views
Measuring misalignment between two positions on sky
Let's say I have the (RA,Dec) for two positions on the sky. I want to measure the position angle between these two positions. In other words, if I had the Cartesian coordinate vectors for these two ...
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1answer
1k views
Declination calculation
My task is to calculate current declination and right ascension for some artificial Earth satellite. For example ISS.
I am using latest TLE data for extracting keplerian orbital elements and then ...
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1answer
1k views
Convert a Decimal into RA or Dec
http://exoplanets.eu/ displays R.A. on screen in hh:mm:ss format but when you export the table, it gives the R.A. as a decimal. Likewise for Declination.
How can I turn for example 24.35417 (WASP-...
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1answer
70 views
Sun's position on summer solstice
Let's say I am in Brasilia (latitude = 15.78°S). This is obviously south of the equator but north of the tropic of capricorn. So on the summer solstice I know that the Sun's declination is +23.26°. ...
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1answer
457 views
Using setting circle for Right Ascension
I'm a little bit confused about the setting circle of my EQ5 mount. Basically, I'm trying to find M42 nebula using Sirius star as reference. So, considere that I did the following steps:
...
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1answer
208 views
Measuring declination in negative hours of arc?
I'm running the program found at https://www.projectpluto.com/source.htm in order to find the Right ascensions and declinations of celestial bodies at various points in time. An odd thing I've noticed ...
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1answer
455 views
Nodes and declinations of Moon
This nice page from NASA has the possibility to create an astronomical events calendar for a certain period. I tried to do that for the year 2017 for Central Europe. What comes out puzzles me:
On ...
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votes
1answer
967 views
Is there a difference between the solar elevation angle and sun declination?
I need to use the sunrise equation but one of the variables is the sun declination. On the other hand, I have the values for solar elevation angle that I need. Are they the same thing?
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0answers
169 views
Ecliptic plane, its precise definition useful for calculations
My question is similar to the one posted by Abtract, whom however never got a useful answer. I am trying to calculate from scratch the exact times of sunrise and sunset anywhere on earth taking into ...
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1answer
643 views
Where is 0 R.A.?
If declination is the degree measurement from the celestial equator roughly the Earth equator unless I've misunderstand plane. "The celestial equator is a great circle on the imaginary celestial ...
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1answer
111 views
Centre (projected) of a galaxy cluster
A galaxy cluster consists of somewhere around a few tens to several hundred galaxies.
To measure the position of a galaxy cluster, i.e. it's RA and DEC, do astronomers always assume it to be its ...
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votes
2answers
5k views
Why are tides biggest during the equinoxes?
I've read that during the equinoxes, tides are at their maximum. Shouldn't this only apply to latitudes near the equator? I mean, when the solar declination is near to 0º and we have a full or new ...
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1answer
224 views
an exercise from Spherical Astronomy by Smart
I want to solve this exercise from Spherical Astronomy by Smart:
Prove that, in latitude 45°, the interval between the moment at which a star's azimuth is 90° east and the moment of setting is ...
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votes
4answers
3k views
Need Simple equation for Rise, Transit, and Set time
I've been looking, unsuccessfully, for hours for a simple set of equations:
Input:
RA and Dec of an object
Observers Lat and Lng
Current Time
Output:
Rise Time
Transit Time
Set Time
(and, ...
