Questions tagged [right-ascension]
The right-ascension tag has no usage guidance.
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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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1answer
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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 ...
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Date and Time of Year given Sun's Right Ascension
Can anyone tell me how to calculate date of year given a specific sun's Right ascension (RA)?
I know RA at Vernox (21 March 00hh:00mm:00ss)is 0 degrees.
How can I get date and time for a given RA, ...
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2answers
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Right Ascension for epoch 2000 - physical location?
I understand that Right Ascension is a longitude-like celestial coordinate that varies from 0-24hrs, taken from a reference point of the vernal equinox. More specifically, for star maps that are based ...
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What exactly is a Right Ascension clock and how was one (mounted on a telescope) used in practice, historically?
@MikeG's answer to Why does this Lowell Observatory telescope have so many knobs? What do they all do? explains that item #6 labeled in the image there (and cropped version here) is likely to be a "...
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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
322 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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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
120 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 ...
2
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1answer
179 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 ...
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1answer
83 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
174 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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190 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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3answers
233 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
587 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
513 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
238 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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Distance from W(West) to vernal equinox
I am pretty new to astronomy and the project I am currently working on requires some knowledge of equatorial coordinate system.
As long as I have been researching this question, I understood that ...
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1answer
62 views
How are the days relating to right ascension around a polar star chart decided?
If you look at this link they have days realting to right acension.
How did they calculate nov 20th == 0h, dec 6 == 1h?
I was trying to calculate this in astropy, but I end up with nov 20th, 8pm == ...
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1answer
351 views
What is the right ascension overhead at Greenwich at noon on 21 march
My question is seen in the title: What is the right ascension overhead at Greenwich at noon on 21 march
I'm a little bit confused since the right ascension is set by the vernal equinox and don't ...
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1answer
144 views
Sidereal time and right ascension
I'm new to astronomy and have to make a star map that displays the stars above a current location. From the information I've pieced together I understand that declination is equal to the current ...
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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 ...
