DS,
A flashlight and globe doesn’t make for a good model of the earth’s shadow. When the light source is smaller than the object, the object’s umbra is an expanding cone.
A flood light and golf ball would be better.
Peace.
I doubt it could have been an airplane. The only time you can see an airplane in the sky, is when it’s landing or launching lights are on. These are usually on during the last part of the decent or begining of the acsent. When I saw them late at night, I was 100’s of miles from an major airport, in the Sierra’s. Jets were so high, that no way could you see just their cabin lights.
True, but the point is that for most purposes, the narrowing of the earth’s umbra is essentially irrelevant when discussing satellite shadowing. At the distance of even a geostationary satellite, the narrowing effect would be so small that it wouldn’t matter much. My point with the experiment was to give him an easy way to see that the satellite can remain visible in the zenith because the shadow is so relatively small to the whole of the night sky.
I would do the whole math for you on the shadow thing, but as an attorney I hate working with numbers that don’t have dollar signs in front of them 
Pl,
Which month of S&T does that picture appear.
I’m not doubting you, just interested.
Even airplanes landing at minor airports still use landing lights 
I doubt you’re 100 miles from any airport.
I don’t know what the object you saw was, but I would be hesitant to rule out airplanes altogether, since they’re so common and at night they can look like they’re doing things they’re really not doing. And since human memory is so poor at recalling details, just because it seems like it was “straight up” doesn’t mean it actually was.
As an aside, you can see a/c landing lights from much farther away than you might think. I’ve seen them from over 50 miles, and even 100 would not surprise me in the least.
peas on earth
Peas,
Maybe your right, but I doubt it. There is a certain feeling to an airplane, as oppossed to a satellite. For one there are 2 lights.
Jim - Commercial aircraft are equipped with navigation lights that include a red and green on either wingtip, a red light on top, a white light on the tail and two strobe lights, one on the starboard wing and one on the belly under the wings.
These are designed, of course, to make the aircraft highly visible (primarily to other aircraft). Their placement on the plane also gives pilots a means whereby they can determine (hopefully) the physical orientation of the other plane and so take evasive or other corrective actions as necessary.
I live about 20 miles from O’Hare Field in Chicago, and I’m very familiar with the landing patterns. On a clear night, I can frequently see as many as five or six aircraft stacked in a pattern that stretches out 20 miles or more into the night sky, and the ones farthest away have not turned on their landing lights. Since commercial aircraft rarely fly above 40,000 or so feet, (7.4 miles) I think it’s a safe bet you’re seeing the lights of an airplane.
Especially if they are “blinking.”
Especially if they “change color.”
I am also 20 miles from SFO. I see planes in their landing patterns all the time. For one it is obvious it’s a plane, they are pretty low and their lights are bright, for 2 this satellite was not in a landing pattern and was travelling way to fast. The landing patterns is north to south, they take off to the south, this satellite was from south west to north west. I don’t think you can see a plane up at 40,000 feet, strobes & all.
Nicrz
Not ALL commercial airplanes have the same lighting configuration, but modern aircraft usually have two RED strobes, one on “the roof” and one on “the belly”, and two WHITE strobes, one on each wingtip. And you’re right about them being useful to help pilots determine the orientation of incoming aircraft.
Now, JimFox, I have seen traffic (air traffic, that is) at MORE than 10 miles (60000 ft) from me. It’s easy, especially if you have the right seeing conditions. Now, I’m not excluding the possibilty of you seeing a satellite at midnight, directly overhead, changing colors, and blinking. Just tell me a few things:
- Where do you live (I need to know the latitude)
- What were the “seeing” conditions? (air temperature, wind velocities, humidity, etc. at different altitudes)
- Were you drinking? (alcohol, that is) KIDDING!!!
Seriously, it is possible to see satellites the way you have described it, it is just not very usual.
Men will cease to commit atrocities only when they cease to believe absurdities.
-Voltaire
Ok,
It was Friday August 13th 1999 at 10PM Pacific Daylight Time, which makes it actually 9:00 PM. I believe more that it was a booster than a plane. I live 12 miles north of San Francisco, which is in California, maybe that explains it.
The satellites I saw overhead at midnight were years ago in the Sierra’s on a dark night. They seemed to bve everywhere, Going West To East.
I’m also not discounting a satellite, but for a point source of light at night, it can be almost impossible to judge how fast it is going. All you know is its angular speed, but not how far away it is, so its linear speed could be almost anything. And even more than that, you’re essentially just looking at a 2D projection of its movement, which can lead to all sorts of mistaken impressions about an object’s speed and direction. Gut feel can easily be totally wrong at night.
BTW, here is a good web page with a lot of info about observing satellites:
http://home.att.net/~janjeff/satintro.htm
It has quite a bit of info on when they are and are not visible, including the effect of the earth’s shadow depending on your location and the satellite’s orbital inclination.
peas on earth
quote
So it seems to me that if it’s dark here, it’s dark up there too. Especially late at night. The ones I saw late at night I think went from west to east, horizon to horizon. I think they were at about 11:00PM Standard Time.
No doubt you’ve heard of the ‘White Nights.’ During summer, north of 60 degrees latitude, the Sun dips just below the horizon, but the sky never quite gets dark.
Orbiting satellites are easily above the Earth’s shadow until the Sun has set more than 25 degrees below your local horizon. If you live North of say, 40 degrees latitude, even the lower East-West orbits are above the Earth’s shadow all night long, since the sun never goes more than ~20 degrees below your local horizon.
I live in Florida (28 deg latitude) and during late June to early July, the ending ‘Window’ for viewing sats (in easily viewed ‘naked eye’ orbits) runs until 11:30 PM.
I’d like to thank UndeadDude for posting the link earlier. If anyone is interested in downloading a shareware program for predicting the passage of visible satellite passes (and plotting their path among the stars, among other features). I’ve written just such a program “Satellite Hunting”. You can find it at http://stephen.fathom.org/sathunt.html (as mentioned in my sig). You can also find descriptions and graphics explaining many of the principles involved in visible satellite observing, as well as links to related sites such as the Visual Satellite Observer’s Homepage and the SeeSatL email list. Happy Hunting!
Am downloading sathunt111, boy this has become rather technical, I hope I can comprehend. Why can’t things be simple? Or is that another topic?
I tried to keep it as simple as possible. IMHO, it is easier to get started with than any similar software that came before (most of which is DOS based and requires careful editing of (often cryptic) control files). If you have any questions, try the online help, or feel free to email me.
Stephen
stephmon@aol.com
http://stephen.fathom.org
Satellite Hunting 1.1.0 visible satellite pass prediction shareware available for download at
http://stephen.fathom.org/sathunt.html
For just about everything you might want to know about major stuff still in earth orbit (including Vanguard 2 and some used rocket boosters), try
http://liftoff.msfc.nasa.gov/RealTime/JTrack/Spacecraft.html
Ya got yer sighting calculations, ya got yer ground tracks, ya got yer satellite information, ya got yer real-time 3D display of the satellites’ positions in space.
Nickrz: was it actually Telstar you saw, or was it Echo? I remember seeing Echo many times in the early 60’s.
When I first came across the above site, I checked out possible views for the brighter objects and found they were only visible two or three hours before dawn. Remembering Echo nearly overhead before midnight, I looked for info on it. I finally found the info on a Japanese space program page. As I recall from there, the Echo satellites (there were two) had orbits between 1000 and 2000 km high. The current bright objects are under 500 km, so they are more likely to be in the earth’s shadow than Echo was.