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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questions
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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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1answer
101 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
75 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, ...
3
votes
1answer
133 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
144 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
229 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
94 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 ...
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1answer
196 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 ...
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0answers
73 views
Skyfield Subpoint() usage
Is subpoint() in skyfield used for finding subsolar point?, i cant find examples in this link subpoint. How can i use it to find ...
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1answer
61 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
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1answer
301 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
645 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
702 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
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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vote
1answer
867 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 ...
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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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1answer
270 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
77 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
183 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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1answer
108 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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1answer
270 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
263 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 ...
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votes
3answers
334 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
770 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
861 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
57 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
372 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
156 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
378 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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1answer
775 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
148 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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vote
1answer
525 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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votes
1answer
98 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
4k 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
203 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
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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, ...
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votes
1answer
1k views
Calculating Right Ascension and Declination from Latitude / Longitude / Time
I have a latitude / longitude / time of a location on Earth, I need to calculate the Right Ascension / Declination that's overhead at the time provided.
So far I've found out that Right Ascension is ...
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1answer
114 views
Why is declination positive in the northern hemisphere?
Simple question -- why is declination positive in the northern hemisphere?
Seems like it should've been called "inclination" since the word originated north of the equator.
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1answer
363 views
Declination change due to precession
I have this problem: I want to calculate the declination of the star in the year 5000. And I know RA (right ascension) and Dec (declination) of the star right now.
How can I calculate it using ...
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1answer
1k views
How to find maximum and minimum right acsension and declination based on the telescope's location?
If I am to apply at a telescope for viewing objects, how to determine (easily) what is the minimum and maximum possible RA and DEC visible from that telescope during that time of the year. For eg, ...
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votes
1answer
359 views
Low precision GMST formula clarification
According to the website http://aa.usno.navy.mil/faq/docs/GAST.php, a low-precision way of calculating the GMST is via the following formula:
GMST = 18.697374558 + 24.06570982441908 D
The website ...
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1answer
1k views
Calculate Dec and RA of a star from Euler angles and GPS data
I have 9DOF sensor (accelerometer, gyroscope, and magnetometer) that gives orientation via Euler angles (yaw, pitch, roll). Along with GPS data (latitude, longitude, elevation, time) this is passed to ...
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1answer
715 views
Which is the shape of the sky?
I'm a software developer and I'm developing a planetarium and the first thing that I don't know is: What is the shape of the sky?
First, I though that it is a semi-sphere, but searching on Internet I ...
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1answer
219 views
Declination and Ascension - the Sun and Andromeda
If Andromeda is overhead at midnight, what is the right ascension of the sun? (andromeda is ar RA =1hr, Dec = +40).
I thought I understood what Dec and RA were, but I can't think of how to start this ...
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votes
1answer
237 views
how steady over time are right ascension and declination values?
I understand that astronomers use right ascension and declination for the position of stars. However both these values strike me as very anthropocentric and, more importantly, unreliable over time as ...
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1answer
15k views
Calculation of right ascension and declination
I am confused about this problem:
If I see an object from Mount Teide (longitude is 16"30'E and latitude is 28"18'N) that passes the meridian (azimuth=0) at 5h (am) UTC, and I also know that the ...
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votes
3answers
9k views
Could someone explain RA/dec in simple terms?
The equatorial coordinate system isn't too complicated. However, for people new to this, it seems rather intimidating at first.
Is there an easy way to explain it?
