Questions tagged [declination]

Questions regarding one of the two main angles(coordinates) of an object perceived by an observer on Earth.

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Sidereal time of rising and setting of the sun on the arctic circle

$$ cos(h)= -tan(\delta)tan(\phi) $$ $$ \Theta = h + \alpha $$ if these two equations are the correct equations to solve the following question why doesnt it yield the same answer for the sideral ...
Moiz khokhar's user avatar
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0 answers
94 views

How to even approach this type of question

Can someone tell me how one would approach this type of question. is there an equation we would use or something of the sort. Ths solution to this question is given below but I just want to understand ...
Moiz khokhar's user avatar
1 vote
1 answer
39 views

Definition for Day Angle

I am searching for a proper definition for day angle. The day angle $\Gamma$ is calculated as follows:$$\Gamma = 2\pi\cdot \frac{n_{day} - 1}{365}$$
Sadira Khan's user avatar
1 vote
0 answers
76 views

Plotting galactic latitude in Ra vs Dec plane

I have an open cluster with calculated percentage of polarization and position angle. I want to have it's scatter plot in Ra vs Dec plane and superimpose a galactic parallel on it. How to plot the ...
Samrat Biswas's user avatar
2 votes
1 answer
90 views

Does RA/Dec vary with the Earth's orbit around the Sun?

I think the RA and Dec of a celestial object should change (ever so slightly) with the Earth's position in its orbit. So do we ignore this in general?
Ambica Govind's user avatar
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35 views

What is the declination of the Sun as a function of its angular distance to solstice?

I will show my own answer, hoping that you guys either confirm it or show me where I went wrong. First, let's have in mind that we are not concerned with the distance Sun-Earth, only with the angle. ...
Guilherme Bahia's user avatar
2 votes
2 answers
199 views

Right ascension and declination visible at that local time and location

If I know the local time of an observer and her/his latitude and longitude, how can I know which stars are visible? I'm developing a planetarium software using the Hipparcos Catalogue. I have also ...
VansFannel's user avatar
2 votes
0 answers
104 views

Figuring out camera pitch and roll given RA and DEC of center of image, as well as lat,long of camera and time taken

What I am trying to figure out is how to get the camera pitch and roll, as described in this image (the green yaw line is where the camera sensor is pointing if given a RA, DEC (of center of image,ie ...
cheesemas46's user avatar
4 votes
2 answers
144 views

Why isn't Amplitude the same as Declination?

From the way I understand Amplitude and Declination, it seems to me that they should always be the same, yet they are not, why? P.S. In the picture I am imagining that the declination remains constant ...
Harbard's user avatar
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1 answer
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Meaning of $\cos H$ in the rising and setting formula

In the rising and setting formula$$\cos H=-\frac{\left(\sin\nu+\sin\phi\sin\delta\right)}{\cos\phi\cos\delta},$$ $H$ is hour angle, $\nu$ is vertical shift, $\delta$ is declination and $\phi$ is the ...
Peter's user avatar
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What is the "sunrise equation" for non-constant declination component?

The standard Sunrise Equation (refraction neglected) is this: $$ \cos(\text{hour angle}) = \tan(\text{declination})\tan(\text{latitude}) $$ This equation - which really has nothing to do with the Sun ...
d_e's user avatar
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When was/will Polaris's declination be maximised?

When was/will Polaris's declination be maximised? In what year was/will Polaris be closest to the north celestial pole.
blademan9999's user avatar
2 votes
0 answers
170 views

Azimuth and Altitude angle between two points in the sky

I want to know how to correctly calculate altitude and azimuth difference, separately, between two points in the sky. The same way will be with icrs coordinates. For the altitude difference, I simply ...
Falco Peregrinus's user avatar
17 votes
2 answers
3k views

On Mars, why are the seasons "strongly amplified" in the southern hemisphere and masked in the northern hemisphere?

In the Darian calendar entry on Wikipedia we read (emphasis mine): The Martian year is treated as beginning near the equinox marking spring in the northern hemisphere of the planet. Mars currently ...
d_e's user avatar
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4 votes
2 answers
674 views

Deriving the apparent angular speed of a star

The angular speed of stars in the sky is constant but the apparent angular speed is not, due to the star moving faster on the celestial equator and slower near the celestial pole. The apparent angular ...
radastro's user avatar
1 vote
2 answers
165 views

How to calculate the local time of sunrise and azimuth of rising point of Sirius?

I know that right ascension equals to $6^h45^m$ and declination equals to $-16°43'$. I need to calculate local time of sunrise and azimuth of rising point of Sirius on 23 of September for an ...
ALiCe P.'s user avatar
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3 votes
1 answer
264 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 ...
danglingPointer's user avatar
1 vote
1 answer
242 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 ...
Peter Orji's user avatar
4 votes
3 answers
706 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 ...
d_e's user avatar
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1 vote
1 answer
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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 ...
ALiCe P.'s user avatar
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7 votes
1 answer
420 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 (...
aggregate1166877's user avatar
5 votes
1 answer
1k 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 ...
Peter's user avatar
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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 ...
VansFannel's user avatar
3 votes
2 answers
1k 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 ...
Ray Walker's user avatar
0 votes
1 answer
213 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(...
Prajwal's user avatar
3 votes
1 answer
66 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?
magnolia1's user avatar
0 votes
1 answer
537 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 ...
andi's user avatar
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4 votes
3 answers
924 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 ...
aman's user avatar
  • 165
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1 answer
1k 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 ...
Borborbor's user avatar
2 votes
1 answer
204 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 ...
luchonacho's user avatar
1 vote
1 answer
250 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?
Bob516's user avatar
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5 votes
2 answers
640 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 ...
user177107's user avatar
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1 vote
1 answer
111 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 ...
Rasika's user avatar
  • 63
0 votes
1 answer
1k 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, ...
user avatar
3 votes
1 answer
1k 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 "...
NeutronStar's user avatar
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0 votes
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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 ...
Izhido's user avatar
  • 103
2 votes
1 answer
1k 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 ...
M10 Radalpha's user avatar
1 vote
1 answer
337 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 ...
Kube Kubow's user avatar
2 votes
1 answer
1k 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 ...
SidS's user avatar
  • 225
2 votes
1 answer
108 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 ...
Q.Ask's user avatar
  • 23
2 votes
1 answer
1k 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 ...
Dave Hook's user avatar
0 votes
2 answers
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 ...
T jey's user avatar
  • 53
2 votes
3 answers
2k 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 ...
noCodeMonkeys's user avatar
2 votes
1 answer
7k 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 ...
Borja's user avatar
  • 123
1 vote
1 answer
3k 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 ...
User123's user avatar
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3 votes
1 answer
399 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 ...
bitemybyte's user avatar
2 votes
1 answer
1k 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 ...
Asael Aiken's user avatar
2 votes
0 answers
96 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 ...
Incnis Mrsi's user avatar
1 vote
1 answer
592 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 ...
AHMED KRS's user avatar
1 vote
1 answer
190 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 ...
Marcus Junius Brutus's user avatar