Declination, near the meridian ??? Help!

[BlackWidow (Mardy)]

I am reading info on some software and it is telling me the following. I am having a little trouble understanding, so some help would be great.

I think I have this correct.
Declination = Up and down with my scope
Right Assention = Left and right with my scope

Alt = Up and down
Az = Right and left

My instruction is the following: point your telescope to a 5-6 th magnitude star near 0 degrees declination and near the meridian (due south in the Northern Hemisphere, due north in the Southern Hemisphere).

I live in Adelaide so if I look at the southern celestrial pole do I assume this is 90 Declination and looking North towards the horizon is about 0 Degrees?? Then the line that passes from North to South is the Meridian? So I need to look for a star that is in the North a little to the East or West???? Have I got this all wrong? Some simple help would be great.


Regards
Mardy

[stephenb (Stephen)]

Hi Mardy,

I assume you're trying to align a computer/GOTO type telescope? Tell us all the make and model as another forum members may be able to help with more specific answers, but in the meantime:

When you are talking telescope mounts, there are two types: Alt-azimuth and Equatorial (often called GEM or German Equatorial Mounts)

Alt-azimuth, short for Altitude-azimuth, is a mount that swings around and around (Azimuth) and up and down (Altitude).

I think I have this correct.
Declination = Up and down with my scope
Right Assention = Left and right with my scope

Right Ascension and declination are the sky equivalent to Latitude and Longitude which we use on the Earth.

Then the line that passes from North to South is the Meridian?

Spot on The imaginary line in the sky which runs from due north, directly over your head , and then to due south is the Meridian. This is the highest point in the sky that any object can get to. For example, the Sun crosses the Meridian at Noon!

I know I didn't answer all of your questions, but others will chime in here, for sure.

Download a free copy of Stellarium (http://stellarium.org/) - Set it up for your home location and turn on the coordinates. This will help you understand the relationship of the Declination and Right Ascension in the sky.

[astro744]

Adelaide is almost 35 dewg. south in latitude. Therefore your south celestial pole (SCP) will be 35 deg. high from due south (geographic not magnetic). Zero declination will be an arc 90 deg. from the SCP running east to west. The zero deg. declination arc will intercept the meridian (north south line) at an angle of 55 deg (90-35) high from the north horizon. Anything below (north) of this arc will have a positve declination and anything above the arc will have a negative declination. The local sidereal time (LST) is equal to the RA of any object on the meridian.

If you move to the south pole your SCP is at zenith and zero deg. declination runs along the horizon.

[stephenb (Stephen)]

Hi Mardy,

I assume you're trying to align a computer/GOTO type telescope? Tell us all the make and model as another forum member may be able to help with more specifics answers, but in the meantime:

When you are talking telescope mounts, there are two types: Alt-azimuth and Equatorial (often called GEM or German Equatorial Mounts)

Alt-azimuth, short for Altitude-azimuth, is a mount that swings around and around (Azimuth) and up and down (Altitude).

[quote]I think I have this correct.
Declination = Up and down with my scope
Right Assention = Left and right with my scope[quote]

Right Ascension and declination are the sky equivalent to Latitude and Longitude which we use on the Earth.

Then the line that passes from North to South is the Meridian?

Spot on The imaginary line in the sky which runs from due north, directly over your head , and then to due south is the Meridian. This is the highest point in the sky that any object can get to. For example, the Sun crosses the Meridian at Noon!

I know I didn't answer all of your questions, but other will chime in here, for sure.

Download a free copy of Stellarium (http://stellarium.org/) - Set it up for your home location and turn on the coordinates. This will help you understand the relationship of the Declination and Right Ascension in the sky.

[sheeny (Al)]

Originally Posted by BlackWidow

I am reading info on some software and it is telling me the following. I am having a little trouble understanding, so some help would be great.

I think I have this correct.
Declination = Up and down with my scope
Right Assention = Left and right with my scope

Alt = Up and down
Az = Right and left

My instruction is the following: point your telescope to a 5-6 th magnitude star near 0 degrees declination and near the meridian (due south in the Northern Hemisphere, due north in the Southern Hemisphere).

I live in Adelaide so if I look at the southern celestrial pole do I assume this is 90 Declination and looking North towards the horizon is about 0 Degrees?? Then the line that passes from North to South is the Meridian? So I need to look for a star that is in the North a little to the East or West???? Have I got this all wrong? Some simple help would be great.


Regards
Mardy

G'Day Mardy!

You are correct about the meridian being the north south line directly overhead.

Zero degrees declination means on the equator of the "celestial sphere" or where the equator would be in the sky when projected outwards. So 0 dec on the meridian is a point that is your latitude north of directly overhead.

90° dec is the North celestial pole (NCP) and -90° dec is the South Celestial Pole (SCP). The SCP will be due south from you location and the same number of degrees above the horizon as your latitude is South.

Unfortunately some mount manuals can get a little confusing because they write the same text for both Alt-az and GEM mounts.

Al.

[BlackWidow (Mardy)]

Thanks for ALL of your assistance... Question for Sheeny.... Just to make sure I have got this correct. If I stand in my yard and look straight up above my head and follow the Meridian looking about 35degrees towards the North, I would be at 0 Declination approx?

Thanks glenluceskies for the Stallarium Advice, I am loading it up now.




Regards
Martin

[sheeny (Al)]

Originally Posted by BlackWidow

Thanks for ALL of your assistance... Question for Sheeny.... Just to make sure I have got this correct. If I stand in my yard and look straight up above my head and follow the Meridian looking about 35degrees towards the North, I would be at 0 Declination approx?

Thanks glenluceskies for the Stallarium Advice, I am loading it up now.




Regards
Martin

Al.