# Calculating RA and Dec from long/lat/time/alt/azm

• B-80
In summary, the conversation discusses the need to convert telescope coordinates from altitude and time to the celestial coordinates of right ascension (RA) and declination (Dec). The individual is looking for resources to assist with the conversion process and is directed to a comprehensive website for help.
B-80
I am writing a script right now which at one point needs to calculate RA and Dec.

There is a telescope pointing directly upwards(altitude=90 deg) and I know where the telescope is located and the time when I get an event. When the telescope sees something my script reads some info and I need to convert where it saw something to RA and Dec.

It's been forever since I had a class on how to do this conversion, and I don't have my book anymore. Any chance someone can point me to a good link that can help me out with an equation for this conversion? I don't really remember enough to derive this myself unfortunately.

## 1. How do I calculate the Right Ascension (RA) and Declination (Dec) from longitude, latitude, time, altitude, and azimuth?

To calculate the RA and Dec, you will need to use specialized astronomical software or online tools. These tools take into account the observer's location (longitude and latitude), time, and altitude and azimuth angles of the celestial object to determine its position in the sky. You can also use mathematical formulas and conversion tables, but these can be more complex and time-consuming.

## 2. What is the purpose of calculating RA and Dec?

Calculating the RA and Dec of celestial objects is essential for astronomical observations and research. It allows astronomers to precisely locate objects in the sky and track their movements over time. RA and Dec are also used to plot the positions of stars, galaxies, and other celestial bodies on star charts and maps.

## 3. How does time impact the calculation of RA and Dec?

Time is a crucial factor in calculating RA and Dec, as the position of celestial objects changes over time due to the Earth's rotation. The time of observation is used to determine the object's hour angle, which, when combined with its declination, gives its precise position in the sky. The date and time must be converted to Julian date for accurate calculations.

## 4. Can RA and Dec be calculated for any location on Earth?

Yes, RA and Dec can be calculated for any location on Earth, as long as the observer's longitude and latitude are known. However, the further away from the equator an observer is, the more complex the calculations become due to the Earth's tilt and curvature.

## 5. Are there any other factors that need to be considered when calculating RA and Dec?

In addition to the observer's location and time, the altitude and azimuth angles of the object must also be taken into account. These angles represent the object's position above the horizon and its direction from the observer, respectively. They are necessary for accurately determining the object's position in the sky and are often measured using a telescope or other instruments.

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