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Have a bad day here


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Ok I am having a bad day as to I can work any thing out .

done a little pic  if you can work it out  to help me.

I can not think on how far down you have to be before you could not see polaris any more in the North sky.

old age is seting in.

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So if i was standing on the equator I could set up North or South ? so any one standing on the equator can image just about all the sky is that right.

In theory yes. Some stars in both hemispheres will be too low down near the horizon though, but essentially you could be able to look north and see most of the NH stars and constellations and if you turned around to look south you would see most of what the SH sky has to offer.

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Aye, it's just as Kropster and Luke say. In any place on Earth, at any given moment at night, you see half the sky. At the poles, that half is all you ever see. At the Equator, if you wait long enough, you'll see the whole sky as the Earth rotates and gradually exposes different parts of the sky at different times.

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So if i was standing on the equator I could set up North or South ? so any one standing on the equator can image just about all the sky is that right.

Just make sure your mount tracks in the right direction if setting up on the south pole!

There will be a number of atmospheric effects at play. Refraction can cause an object below your true horizon to appear above it so even if you see it, you wouldn't want to polar align visually on Polaris.

Atmospheric extinction dims low elevation stars an awful lot too. You'd need perfect conditions.

But beyond that, you would indeed see all the constellation in both hemispheres.

Imagine having the same length of night and day all year round. No midnight twilight at the Equator!

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The weird thing about being on the equator is to see some of the usual constellations on their side. Orion in particular !

That gave me a headache. It reminds me of the time I realised the moon is upside-down in the southern hemisphere.

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The effect of Atmospheric Refraction means you actually see more than 180 degrees of sky. As you observe closer to the horizon stars start to appear higher in the sky than they actually are. Since the effect is greatest on the horizon- a star seemingly skimming the horizon is actually about half a degree below the horizon.

Thus it might be possible to see Polaris in the southern hemishere! Well at 0.5 deg South of the Equator anyway. 

BennettAtmRefractVsAlt.png

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That gave me a headache. It reminds me of the time I realised the moon is upside-down in the southern hemisphere.

No it's not. :eek: :eek:

The moon remains exactly unchanged in it's orientation. :cool: :cool:

You're upside down, not the moon. :grin: :grin: :grin:

P.S. Thanks for the "u". :icon_salut:

As LJ says owing to refraction you may still see Polaris a bit south of the equator.

Same effect at sunset and I assume sunrise. At sunset when the sun just touches the horizon to our eyes then the sun has actually just sank fully below the horizon.

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Thanks all, brain working much better today,  This all started out by looking at some images on here taking from down under , I could not work out as to some images can be seen in the Uk in the winter and some not ,So I was trying to take the tilled of the Earth to how far South I  have to be to see  North and South just about all year round . That may sound easy to some but not allways to me. So thanks again.

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I was also thinking it is possible to see Polaris about 0.5-1 degree above horizon in the southern hemisphere for the same reason Laser Jock pointed out. Nice to have my thoughts reaffirmed. Its pretty much the same effect when you see the Moon rising above the horizon. It looks many times bigger than it actually is because the light from it is being bent/stretched.

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Wait till you realize that stars on either side of the celestial equator curve in different directions :)

It is indeed a strange effect. I did a 10mm fisheye lens shot looking due south which also shows it. I thought it was some kind of lens distortion at first!

DSIR4220_noise_processed.jpg

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It is indeed a strange effect. I did a 10mm fisheye lens shot looking due south which also shows it. I thought it was some kind of lens distortion at first!

DSIR4220_noise_processed.jpg

Now that's just showing off to make most of the rest of us jealous  :Envy:

Anyone want to see some nice orange sky  :evil:  :mad:

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Now that's just showing off to make most of the rest of us jealous  :Envy:

Anyone want to see some nice orange sky  :evil:  :mad:

Here's some orange sky!

 http://i.imgur.com/EYgH9xj.jpg

I think the beauty of the milky way (specifically the cygnus rift in this image) is best expressed through at least 3 minutes 30 seconds of exposure under super-heavy LP.

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Why do it look like the Stars are going North & South at the same time?  Was thinking the N/S poles but Stars are to far aways . Look like  bad day 2 coming my way.

In that picture, the camera was pointing south, so the stars are going east and west. Its a bit weird and i dont fully grasp it either. I'll have to pay a visit to the equator one day to see it and maybe then i'll get it. 

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