Iridium

General physics and astronomy discussions not directly related to Celestia
granthutchison
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Post #21by granthutchison » 22.04.2004, 17:00

Evil Dr Ganymede wrote: If I'm right under the flare centre, shouldn't I have to be looking straight up since it'd be directly overhead?
No. It's like using a mirror to signal an aeroplane, except in this case the satellite is the mirror and you're the aeroplane. The satellite could be anywhere in the sky, so long as one of its flat surfaces is making equal angles with the Sun and your location. As the satellite moves, it sweeps a track of reflected sunlight across the Earth, brightest in the centre of the track. If you go and stand in the track, you see a bright light at the satellite's position in your sky.

Grant

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Post #22by Evil Dr Ganymede » 22.04.2004, 18:06

That's not what the map appears to be implying though. It seems to be showing that the satellite will be at the dot on the line there, so if you're under that, it'd be overhead.

I'm getting the impression I should ignore the map and just use the info in the text...

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Post #23by granthutchison » 22.04.2004, 18:11

Evil Dr Ganymede wrote:That's not what the map appears to be implying though. It seems to be showing that the satellite will be at the dot on the line there, so if you're under that, it'd be overhead.
Um ... that's decidely not what the map caption says:
The small map shows the path of the brightest point of the flare over the ground, relative to your location (marked "You"). The point marked "Centre" show the point on the flare's track which is nearest to your location, so if you want to get the best possible view, you can drive there. Any point along the flare's track will have more or less the same maximum intensity, so if you can't reach the nearest point, any place along the track will be just as good.
So the dot on the line has no significance except as the point on the flare centre-line that is nearest to your location. And notice that neither the flare centre-line nor the dotted connection between "You" and "Centre" have any relevance to the position of the satellite - the satellite isn't marked on the map at all, and it could be reflecting light towards the flare track from any point in the sky.

Grant

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Post #24by Evil Dr Ganymede » 22.04.2004, 18:32

Ohhh... I think I get it now. So the dot on the map is kinda like the central point of a searchlight beam, shining from the satellite, right? If you're further away from it, then you can still see the light so long as you're in the circular area covered by the beam, but it'd be dimmer. And the track is the track of the searchlight beam as the satellite moves?

If that's so, it might help considerably if they actually drew it like that on the map...

granthutchison
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Post #25by granthutchison » 22.04.2004, 18:41

Evil Dr Ganymede wrote:So the dot on the map is kinda like the central point of a searchlight beam, shining from the satellite, right? If you're further away from it, then you can still see the light so long as you're in the circular area covered by the beam, but it'd be dimmer. And the track is the track of the searchlight beam as the satellite moves?
That's it!

Grant

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Post #26by Guest » 22.04.2004, 20:45

I've got 2 scheduled for tonight, including a -8 right at my house. If the weather stays good, maybe I'll have a picture of it to post tommorow.

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Post #27by tony873004 » 23.04.2004, 07:09

It called me Guest in my last post. I guess I forgot to login.
Here's my -8. It's actually 2 images photoshopped together. Each image is 4 seconds and contains approximately 1/2 of the flare. 8 seconds was too long for a single exposure as it washed out the sky.
Image

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ElPelado
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Post #28by ElPelado » 23.04.2004, 08:58

WOW nice, -8 is very brilliant. The most brilliant I ve seen till now was -5 I think...
---------X---------
EL XENTENARIO
1905-2005

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Adirondack M
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Post #29by Adirondack » 25.04.2004, 21:27

Wow tony873004, great picture! Well done.

So as you look to an Iridium, one will look to you:

Image

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ElPelado
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Post #30by ElPelado » 03.05.2004, 20:26

The other day i was waiting to see the Hubble for the very first time, and i saw it. But at the same time another satelite appeared. It doesnt appear in heavens above. But in starry night, at the same time the hst was on sight, an atlas centaur was there. The problem is that the path that the hst did is not the path that it traveled in starry, so i dont know if i may trust or not starry....
And today, again waiting for the hst, i saw something similar to an iridium, but no iridium was at that time at heavens above..... can some one explain me what i saw??
---------X---------

EL XENTENARIO

1905-2005



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