Movement of the Southern Cross
Submitted: Monday, Sep 27, 2004 at 12:44
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Vince NSW
Sitting out on the back deck having a few quite glasses of wine last night, the conversation drifted on to stars. In particular the
Southern Cross. We all know that the Crux rotates around the South Celestial pole in a 24 hr period, and we agreed that it gets later by 4 mins per day.
I have since discovered that it is DEAD vertical on 29 March each year.
The question for the Brains Trust is :-
At the Latitude of
Sydney (about 33 deg) will the Cross set (drop below the horizon) at any time in the 24 hr period?
I await your gems.
Vince
Reply By: Member - Michael (NSW) - Monday, Sep 27, 2004 at 12:47
Monday, Sep 27, 2004 at 12:47
Was that "a few quite glasses" or "quite a few glasses"..... (:0)
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Follow Up By: Vince NSW - Monday, Sep 27, 2004 at 12:50
Monday, Sep 27, 2004 at 12:50
The former. Just enought to get the mind drifting away from the troubles of the world.
Vince
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Reply By: Member - Michael (NSW) - Monday, Sep 27, 2004 at 12:54
Monday, Sep 27, 2004 at 12:54
I think you did ok............ LoL
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Reply By: equinox - Monday, Sep 27, 2004 at 13:12
Monday, Sep 27, 2004 at 13:12
Vince,
The fact that it is dead vertical on 29 March is irrevalent.
The cruical figure is how many degress the cross is from the pole. If it is less than 33 degrees (in
Sydney) it will never go below the horizon. It is more than 33 degrees it will go below the hozizon once a day.
Remember that the angle of the South Celestial Pole from the horizon is equal to the latitude of the point of observance. (in the southern hemisphere)
Cheers
Equinox
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Follow Up By: Member - Michael (NSW) - Monday, Sep 27, 2004 at 13:19
Monday, Sep 27, 2004 at 13:19
I must be missing something here!!!
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Follow Up By: Vince NSW - Monday, Sep 27, 2004 at 13:20
Monday, Sep 27, 2004 at 13:20
Thanks Equinox thats the information I needed. This is a very usefull piece of information. Now for a suplmentry question :-
Whwer is the best place to start learning about celestial navigation ?
Vince
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Follow Up By: David T - Monday, Sep 27, 2004 at 15:52
Monday, Sep 27, 2004 at 15:52
When the cross will be dead vertical depends on the time of day. The earth is continuously rotating, so the stars appear to be moving continuously. It may be dead vertical at 6pm one night and at 8pm another night.
I think the declination of the cross is ~60 degrees south, so it may just skim above the horizon all the time in
Sydney, Certainly doesn't in
Brisbane at lattitude 27 south.
Best place to learn about the stars - join an Astronomical Association. Was in such a thing at high school, but there are two few hours in my life to continue such things now.....
My 2 cents worth, which in this age of rounding equals nothing!
Bye
David
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Follow Up By: Vince NSW - Monday, Sep 27, 2004 at 16:26
Monday, Sep 27, 2004 at 16:26
David,
It should be vertical at midnight on the 29 march each yearfrom what I have been able to find on the net
Vince
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Reply By: Well 55 - Monday, Sep 27, 2004 at 13:38
Monday, Sep 27, 2004 at 13:38
At sea.
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Reply By: Baz (NSW) - Monday, Sep 27, 2004 at 14:54
Monday, Sep 27, 2004 at 14:54
I'm all at sea !!!
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Reply By: Member - John (Vic) - Monday, Sep 27, 2004 at 15:46
Monday, Sep 27, 2004 at 15:46
I was recently in outback WA on a 4x4 club trip.
We have two surveyors in our club who came on this trip and bought their Theodolite with them.
It was the most interesting evenings entertainment that I have had out bush.
We looked at the stars etc and the knowledge these guys had was unreal.
It certainly sparked my interest in all things space.
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Follow Up By: cokeaddict - Monday, Sep 27, 2004 at 20:19
Monday, Sep 27, 2004 at 20:19
interesting last comment you made there John.....
"It certainly sparked my interest in all things space"
Am wondering if this would work on my wife? lots of "space" up there too.!
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Follow Up By: Baz (NSW) - Tuesday, Sep 28, 2004 at 09:29
Tuesday, Sep 28, 2004 at 09:29
"Not nice"
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Follow Up By: Des Lexic - Tuesday, Sep 28, 2004 at 09:48
Tuesday, Sep 28, 2004 at 09:48
Cokeadict maybe your wife and
mine are related.
Does she wear those christmas earings with flashing lights too. I keep telling her the lights are on and no-ones home. LOL
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Follow Up By: cokeaddict - Tuesday, Sep 28, 2004 at 10:07
Tuesday, Sep 28, 2004 at 10:07
Hello Des Lexic,
Thats a scary thought mate .... 2 of them out there
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