Astronomical point

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Astronomical point
« Reply #60 on: October 11, 2006, 07:41:55 AM »
The field of vision of a telescope on the surface of the FE is not 180 degrees. For the same reason that the sun appears to set, stars below a certain angle relative to the plane of the earth appear "below" the horizon, and so will not be visible to an observer sufficiently far away.

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Ma

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Astronomical point
« Reply #61 on: October 11, 2006, 11:59:16 AM »
Quote from: "Unimportant"
The field of vision of a telescope on the surface of the FE is not 180 degrees. For the same reason that the sun appears to set, stars below a certain angle relative to the plane of the earth appear "below" the horizon, and so will not be visible to an observer sufficiently far away.


I never said that 180' at once but you can rotate it to any angle possible. So you can infact see 180'. Not to mention there are
fish eye telescopes that see 180'+360' at once.

To be honest I don't quite get what your meaning when you say
"for the same reason as the sun appears to set" 'cos that's one of the
unanswered question at the FAQ... So that's hardly good enough to be used as comparison. Any other explanations to the horizon stars would be
appreciated.

Astronomical point
« Reply #62 on: October 11, 2006, 01:02:50 PM »
Quote from: "Ma"
To be honest I don't quite get what your meaning when you say
"for the same reason as the sun appears to set" 'cos that's one of the
unanswered question at the FAQ... So that's hardly good enough to be used as comparison.

Think of it like RE gravity; we don't know why it happens, we just know that it does. Given that it does happen for the sun, it is safe to assume that it also happens for the stars.

You misunderstood what I was trying to say about the field of vision thing. Sure you can move your telescope from one horizon all the way over to the other to create 180 degrees of movement. My assertion was that - for the same reason the sun appears to set - when your telescope is "flat" and looking at the horizon, you are actually seeing the stars 20 or 30 degrees above the true horizon. Those stars whose true line of sight would lie beneath that 30 degree barrier would thus appear below the horizon, and so you can't see them because the ground is in the way. These stars that you can't see are the ones that would be very far away, such as those southern hemisphere stars to an obersver in the northern hemisphere, and vice versa.

Note I'm not saying that the stars go below the plane of the earth, just that the path of the light behaves in such a way as to create that illusion; again like the illusion of sun setting.