Question About Declination/Right Ascension? (Second time)?

Question

I am confused so bear with me. From what I understand I can look up an object’s Declination/Right Ascension and use this info to know where to look for that object in the sky. Is this correct?

If Mars is listed as being...Dec: 23degrees21min, RA: 06h02m
Can I use this to know where to look?

If its declination is 23 degrees this should be at the Zenith for anyone whose latitude is 23 degrees. Right?

Declination is directly related to latitude which seems pretty straight forward, but there is something about right ascension that I don't understand.

Where is RA measured from? I know it is measured eastward from the March Equinox, but how do I find where the March Equinox is?

And yes I deleted this question the first time. Sorry about that. I got so confused I had to scrap it and start from scratch……and Rev. Einstein I did read your response and appreciate your input.

AWESOME thanks guys. Now I am reading about Sidereal time!!

Answer 1

Declination and right ascension in the sky are like latitude and longitude on the surface of the Earth. What complicates things is that the RA/Dec sphere is rotating relative to Earth. The missing component that you need for finding things with these coordinates is sidereal time. You local sidereal time corresponds to the right ascension of your meridian - that is, the portion of the sky currently due south (from the northern hemisphere). Sidereal time is useful only as a local time base; there are no sidereal time zones or universal sidereal time.

If Mars is at RA 06:02, it means that at sidereal time 06:02 Mars will be due south and at its highest in the sky, 23° above the celestial equator. So yes, if your terrestrial latitude is 23°N, Mars will pass through the zenith at that time. RA increases to the east in the sky, so the zero point is 06:02 (or 90.5°) to the west and on the equator, which is to say it just set.

Computerized telescopes use these coordinates to find objects in the sky. Astronomers used to use setting circles to find things by coordinates. To use setting circles you need a properly aligned equatorial mount, and know the position of a reference star. From there, you can find your way to any other object by knowing its coordinates. You find the coordinates of your target and reference star from a star atlas.

These days, setting circles on amateur mounts are pretty much just for show and hardly anybody uses them. Amateur astronomers either use computerized mounts, or they star hop. Star hopping involves using a star chart and the patterns of the stars to guide your telescope to its target.

Answer 2

Declination and right ascension will tell you where an object is located *on the celestial sphere*. But in order to know *where to look*, you need more information: you need to know your location on earth, and the time and date.

If an object is at 23 degrees declination, then it will *transit* at the zenith for an observer at 23 degrees latitude; which means that the object will be directly overhead for that observer exactly once per day. At other times of the day, it will be in different locations. This is because the earth rotates, which makes the sky appear to move.

The zero point of RA is "the first point of Aries" or the Vernal Equinox. This is the point in the sky where the Sun is on the first day of spring, and it is one of two points where the celestial equator crosses the ecliptic. The easiest way to find this point is to use a star chart.

Answer 3

What you actually have to do is find and confirm a fixed star and then set the RA and DEC circles to that fixed setting and then find the other objects you want to see.