# Convert right ascension to degrees calculator

Add the following snippet to your HTML:. The real-time position of any celestial body can be calculated using some parameters called Orbital Elements. Read up about this project on. These are the parameters that define an orbit at a particular time. I just googled and got orbital elements for the year text.

You can try different methods or go to the following sites to gather data.

The positions of objects in the sky as viewed from Earth are referred to a coordinate system whose alignment is changing with time in a complex way. A few of the important motions and effects are summarized below. We use the Equatorial coordinate system to refer positions to a frame in which the stars appear still, and the right ascension RA and declination DEC are used to give the coordinates of the planet with respect to the fixed stars. By using orbital elements referred to the fundamental epoch J, the orbits of the planets are described in a coordinate system which is based on the position the vernal equinox will have at J A further advantage of this dodge is that our positions for the planets will correspond exactly to the positions found in most recent star charts.

You should be able to plot the path of Mars directly onto a star chart such as The Cambridge Star Atlas.

### Decimal Degrees to Degrees Minutes Seconds

Our observation platform the Earth is nodding, so the stars and planets will appear to nod together. Our J elements will give is positions which match the co-ordinates of the stars found in star maps. There is a problem with this use of J equinox and mean ecliptic. The effect will be very small for 10 years either side of J source The main steps in the calculation are:.

The following tables show the days from the beginning of the year to the beginning of each month, and the days from J to the beginning of each year. We can find the day number corresponding to the date of the elements 16th August as follows:.

And the day number of the date we want the position for 1st Aprih is:. You must take dates before an epoch as negative in the calculations below.

For fast moving planets such as Mercury and Mars, you need to include the time of day which you want the position for. Just add the Universal Time in decimal hours divided by 24 to the day number of your position dele above :. The Mean Anomaly of the planet is given by the very simple formula:. Mean Anomaly is calculated considering the orbit to be circular, but True Anomaly gives the actual position of the planet as it considers orbit to be elliptical.

We convert Mean Anomaly to True Anomaly using the following formula:. For our Mars position, we have:. The distance from the planet to the focus of the ellipse is given by a simple formula based on the geometry of the ellipse:. Having found the true anomaly and the radius vector of the planet, we can go on to find the position of the planet with respect to the plane of the ecliptic. Similarly find M mean anomalyV true anomaly and r radius vector for Earth. We then have the geocentric ecliptic coordinates of the planet. For the case of Mars 1st March we have:. As we are using elements referred to the equinox of J The formulas are given below:. Rectangular coordinates are not much use with star charts, so we calculate the familiar right ascension and declination using the formulas:.Enter an astronomical location using one of the coordinate systems and use "Calculate" and that location in all of the coordinate systems is returned. The coordinate systems are the equatorial systems J and B plus the user's choice of year and "current date", and galactic coordinates "new" and "old".

I try to be permissive on the input grammar. You can enter RA as hours minutes seconds, or hours and minutes with a decimal, etc. The same for Dec: " Galactic coordinates are always degrees and decimal fractions.

The result-values are all round-tripped via J, so if you enter B or Galactic Coordinates, the "calculated output" has been round-tripped and you can compare the output value to your input value and check precision.

Some of the direction-cosine matrics were calculated from the rotation values. You should not expect all the transforms to be good to an arc-sec. The direction-cosine matrix I got from "Spherical Astronomy" has only six-digit values.

### How do you convert Right Ascension to degrees?

And the Old Galactic Coordinate system I am using has an imprecise guessed longitude-shift relative to modern Galactic. The transformations between J The transforms involving the user's special year use the algorithms in the Explanatory Supplement to create a direction-cosine matrix. The two methods are not the same. So the user can enter a "user year" of For user-supplied dates note that one row is called "Current Year" but the user can over-ride that, so there can be two user-supplied datesI convert to an ephemeris time without any of the fine details about the precise meaning of "Besselian Year" etc; indeed I assume that months have thirty days.

Since precession is only about twentieth of an arc-sec per yeardate-errors of a day or two are inconsequential. The "early galactic" output is presented first with a matrix-transformed value, then again using trigonometric equations in Green that transform new Galactic to Old galactic and will be good at low latitudes but poor near the poles. If you like the calculator but would like to suggest improvements, feel free to write me at astroayers gmail.

Astronomical Coordinate Calculator version 0. J RA Dec. B RA Dec.

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User Year: RA Dec. Current Year: RA Dec. Galactic: Longitude Latitude.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Astronomy Stack Exchange is a question and answer site for astronomers and astrophysicists. It only takes a minute to sign up. The answers to this question are very clear and much better than I could have written. I'm not sure what you mean by "the stellar time at Greenwich at 0h UTC is 22h20min"but I'm assuming that you mean that that is the amount of time since the culmination of Aries over the Prime Meridian Greenwich.

That being the case, the Right Ascension RA of your body can be easily calculated. All we need to do is figure out what RA is passing your meridian at the time in question. We already know that RA 22H 20m is passing over Greenwich at the time of interest or, at least that is what I am assuming as your explanation is not at all clear.

The first stage is to take a piece of ruled or graph paper and near the middle mark a short, horizontal line. This is your horizon, and is marked 'H'. Now draw upwards 9 lines and mark the top ,'Z' and downwards 9 lines and mark the bottom 'N'.

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You should end up with something that looks like this Which is, basically a picture of your meridian as you sit and gaze south at it. Now we need to add a little more detail. Imagine that the celestial sphere is actually a glass sphere surrounding the earth with the stars and stuff stuck to it that we can project anything we want on to we'll ignore porn and coke adverts for nowwhere would the celestial equator show and where would it go on our picture of the meridian?

Now we put in the body we are looking at. We can also label some of the distances we know, to end up with We want to find dec and the diagram shows us that This is much more complex to explain here than it is to do, or to teach in person.

With a bit of practice you'll be doing it in your head. I hope this has helped a bit. I should point out that I have ignored observation errors, such as height of eye, which may be significant from the place you specify and parallax but I wanted to keep it as simple as possible. Sign up to join this community.Add the following snippet to your HTML:. The real-time position of any celestial body can be calculated using some parameters called Orbital Elements.

Project tutorial by Shubham Paul and Samhita Ganguly. These are the parameters that define an orbit at a particular time. I just googled and got orbital elements for the year text. You can try different methods or go to the following sites to gather data.

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The positions of objects in the sky as viewed from Earth are referred to a coordinate system whose alignment is changing with time in a complex way. A few of the important motions and effects are summarized below. We use the Equatorial coordinate system to refer positions to a frame in which the stars appear still, and the right ascension RA and declination DEC are used to give the coordinates of the planet with respect to the fixed stars. By using orbital elements referred to the fundamental epoch J, the orbits of the planets are described in a coordinate system which is based on the position the vernal equinox will have at J A further advantage of this dodge is that our positions for the planets will correspond exactly to the positions found in most recent star charts.

You should be able to plot the path of Mars directly onto a star chart such as The Cambridge Star Atlas. Our observation platform the Earth is nodding, so the stars and planets will appear to nod together. Our J elements will give is positions which match the co-ordinates of the stars found in star maps. There is a problem with this use of J equinox and mean ecliptic.

The effect will be very small for 10 years either side of J source The main steps in the calculation are:. The following tables show the days from the beginning of the year to the beginning of each month, and the days from J to the beginning of each year. We can find the day number corresponding to the date of the elements 16th August as follows:. You must take dates before an epoch as negative in the calculations below.

For fast moving planets such as Mercury and Mars, you need to include the time of day which you want the position for. Just add the Universal Time in decimal hours divided by 24 to the day number of your position dele above :. Mean Anomaly is calculated considering the orbit to be circular, but True Anomaly gives the actual position of the planet as it considers orbit to be elliptical. We convert Mean Anomaly to True Anomaly using the following formula:.

For our Mars position, we have:. The distance from the planet to the focus of the ellipse is given by a simple formula based on the geometry of the ellipse:.Lecture 1: Introduction to Astronomy Astronomical Coordinate Systems:. Astronomers base their measurement of positions of objects on the concept of the celestial sphere upon which all objects are assumed to lie regardless of their true distances. The celestial poles and equator are the projections of the Earth's poles and equator onto the sky. The meridian is the circle running from one pole to the other through a point directly overhead for an observer. Several different coordinate systems are useful depending on the situation:.

Equatorial coordinates: An Earth-based system useful for pointing telescopes with axes that are parallel to the Earth's polar axis and equator called equatorial mount telescopes. This system was the first used in compiling stellar catalogues, and the two coordinates used to define the location of an object, right ascension abbreviated often as or RA and declination or DECare in common use today.

Right ascension is analogous to longitude, is usually measured in units of time: hours, minutes, seconds. The zero-point for right ascension is the Vernal Equinox also called the Aries Point in the textlocation on the celestial equator of sunrise on the first day of spring.

Declination is analogous to latitude and is measured as north or south of the celestial equator. Declination is usually expressed in degrees, minutes of arc, and seconds of arc. Another complication with right ascension arises from the changing angular size of circles of constant right ascension when moving from the celestial equator towards the celestial pole, the circles shrink by a factor of cos DEC which must be taken into account.

It is very important to keep minutes of time and arc minutes clear! When using equatorial coordinates, the H. The hour angle is the distance in time units that object lies east or west of the meridian.

It is related to time as measured by the stars called sidereal time via the relation. If the H. This illustrates how the equatorial system accounts for the rotation of the Earth and explains why early astronomers chose to use time units for right ascension. Coordinates based on a telescope's location can be advantageous as can coordinates based on the plane of the Solar System or on the plane of the Milky Way galaxy.

Spherical trigonometry is handy for converting between coordinates systems. Positions of stars and other objects in the sky can be used for navigation now laregely made obsolete by Global Positioning Systems.

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For example, the elevation of the North Star above an observer's horizon is equal to the observer's latitude:. The Earth's rotation is used a basic unit of time measure -- the day.

If you keep track of the intervals between successive times of maximum elevation of the Sun above the horizon e.

How to use a Scientific Calculator

These differences result from two causes -- first, we measure time with respect to the Earth's rotation axis and hence equator while the Sun's motion is along the ecliptic, and second, the Earth's orbit is elliptical and the Earth moves faster along its orbit when closer to the Sun. We also use the time that it takes the Earth to orbit the Sun as a time unit, the year.

Note that several different lengths of a year can be defined depending on what reference is used:. Seasons on our Home Planet. Seasons result from the The seasons are obviously opposite in the Earth's two hemispheres. The polar direction is slowly changing due to precession direction takes 26, yrs to complete one circuit but the angle between the polar axis and the ecliptic is fixed and invariant.Earth scientists determine positions on earth by the angular measurements of latitude and longitude.

The earth has a fixed circumference, so you can convert these to feet by calculating the distance the angles defined by latitude and longitude sweep. Angular measurements range range from degrees and degrees with respect to a reference, which is the equator when measuring latitude and the prime meridian when measuring longitude. You'll need your calculator to convert these angles to distances from their respected references. Convert the latitude and longitude measurements from degrees, minutes and seconds to decimal notation.

The conversion factors are 60 seconds per minute and 60 minutes per degree. This example is for Denver International Airport.

Convert the decimal degrees to km. The circumference of the earth around the equator is slightly different of that around the poles, because the planet isn't perfectly round.

However, they differ by only 42 km. This makes the conversion factor 10,km per 90 degrees. This factor is easier to remember and easier to use than converting directly to feet. Longitude: This is the distance of DIA from the prime meridian. The negative sign in front of the longitude value indicates the distance is west of the prime meridian.

This calculation gives the position of Denver International Airport as Latitude: This is the distance of DIA from the equator. Convert kilometers to feet using the conversion factor Copyright Leaf Group Ltd.Longitude and right ascension both start on the Greenwich meridian, which simplifies converting from one coordinate system to another. Meridians are imaginary lines along which a coordinate has a constant value and run north to south.

Right ascension meridians fall on the celestial sphere, while those for longitude fall on the earth. Right ascension is measured eastward and is in hours, minutes and seconds, with values ranging from 0 to 24 hours.

The degree line is called the International Date Line. Multiply the decimal time by 15 degrees. For example, 2. This value corresponds to the degree equivalent of 2 hours, 30 minutes and 45 seconds. Subtract degrees from the result in Step 2 if the result is greater than degrees, and this will give you the correct number of degrees longitude west.

If the number calculated in Step 2 is less than degrees, leave it alone. It correctly gives you the number of degrees east. For example, a right ascension of 13 hours in decimal form is The coordinate in longitude is degrees, and it is referencing a location west of Greenwich.

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