Equitorial/Horizontal co-ordinate questions

[Brewer]

I have the following question and I'm interested in if any of you can help me with it.

What are the altitude and azimuth of the south celestial pole as seen from Sydney, Australia (latitude = 33°55'S)?

From my diagram that I've drawn, it appears that the altitude is either 146°05'S or 56°05'S, but is that right? And if it is which one do I use? The smaller (i.e. >90°) answer?

The azimuth I'm more concerned with. My initial thought is that because its the south celestial pole it should have an azimuth of 180°. Is this the correct way of thinking?

Thanks for any help/info.

Brewer

 

[Garth]

What are the altitude and azimuth of the south celestial pole as seen from Sydney, Australia (latitude = 33°55'S)?
From my diagram that I've drawn, it appears that the altitude is either 146°05'S or 56°05'S, but is that right? And if it is which one do I use? The smaller (i.e. >90°) answer?

If you face North the altitude is 146°05' and if you face South it is 56°05'. As altitude is measured from the nearest horizon and is not more than 90⁰, it is the latter figure that is correct.

Garth

 

[Brewer]

If you face North the altitude is 146°05' and if you face South it is 56°05'. As altitude is measured from the nearest horizon and is not more than 90⁰, it is the latter figure that is correct.
Garth

So I was right then?

Thanks for that. What about the azimuth? Was I correct in thinking that this is 180⁰?

 

[Garth]

So I was right then?
Thanks for that. What about the azimuth? Was I correct in thinking that this is 180⁰?

Azimuth has been defined in different ways:
as the angle between the vertical through the south point and the vertical through the object measured westwards along the horizon from 0⁰ to 360⁰(so the SCP will have an azimuth of 0⁰),
or the angle between the vertical through the north point and the vertical through the object measured eastwards or westwards along the horizon from 0⁰ to 180⁰ (so the SCP will have an azimuth of +/-180⁰),
or the angle from the vertical through the north point and the vertical through the object measured eastwards along the horizon from 0⁰ to 360⁰(so the SCP will have an azimuth of +180⁰), this final definition is similar to true bearing and is the one I would use.

Garth

 

[Brewer]

Azimuth has been defined in different ways:
as the angle between the vertical through the south point and the vertical through the object measured westwards along the horizon from 0⁰ to 360⁰(so the SCP will have an azimuth of 0⁰),
or the angle between the vertical through the north point and the vertical through the object measured eastwards or westwards along the horizon from 0⁰ to 180⁰ (so the SCP will have an azimuth of +/-180⁰),
or the angle from the vertical through the north point and the vertical through the object measured eastwards along the horizon from 0⁰ to 360⁰(so the SCP will have an azimuth of +180⁰), this final definition is similar to true bearing and is the one I would use.

Garth

Thanks for that. We had it defined as the second one you mentioned, from North through East. I just wasn't sure how the SCP checked out, as my original diagram got a bit confusing!

You've been a great help though. Thanks a lot.

 

[tony873004]

Check your altitude answer. What would the altitude of the South Celestial Pole be if you were on the South Pole with a latitude of 90 degrees? What would the altitude of the South Celestial Pole be if you were on the equator with a latitude of 0 degrees?

 

[Garth]

Check your altitude answer. What would the altitude of the South Celestial Pole be if you were on the South Pole with a latitude of 90 degrees? What would the altitude of the South Celestial Pole be if you were on the equator with a latitude of 0 degrees?

Quite correct I was thinking of zenith distance, that's the problem with hurried posts!

"Why keep your mouth shut for fear of being thought a fool when you can open it and prove yourself to be so?"

Garth