The type of the present star sky would be surprising to the astronomer of the middle of the XX century when leisure of the heavenly arch was intruded upon by only rare flashes of meteors. If you look at stars now in clear moonless night, then will sweep up as among natural stars with a different speed and diversely artificial Earth satellites move.
Brightness of artificial Earth satellites
Many artificial Earth satellites (further - the artificial satellite) have the sufficient brightness allowing to observe them with the naked eye. And at the same artificial satellite throughout flight brightness can change from hardly noticeable to the brightest star exceeding brightness. The example of that is the communication satellite of Iridium during which flight the flashes on brightness exceeding light of the full Moon are observed. These differences of brightness are connected with irregular shape of artificial satellites and with their rotation during flight. Different elements of satellites have various reflective ability and the area. Reflectors of the directed antennas especially well I reflect light, heat-shielding screens - too. Also the painted parts of the building of the artificial satellite are to a lesser extent capable to light reflection of the panel of solar batteries. Naturally, the spherical satellite does not create during flight of differences of brightness and flashes.
Artificial satellites visible sizes
Most often artificial satellites are visible to the observer from Earth as dot objects. But if you had to observe flight of the ISS, then you for certain paid attention that this satellite looks as an extended object. And not only the shining structural elements, but also blackout of some stars are noticeable by a spacecraft way. Astronomers call such blackout a covering. This phenomenon becomes possible for observation thanks to very big ISS sizes.
Speed and trajectory of flight of the artificial satellite
Watching from the Earth's surface the movement artificial satellite, you can notice that the visible trajectory of flight of the satellite represents certain smoothly curved curve. Actually orbits of satellites are either circular, or elliptic. The visible effect of a curvature of a trajectory of the artificial satellite is caused by an inclination of its orbit to the terrestrial equator and rotation of Earth, simultaneous with the movement of the satellite. Also visual change of speed of flight of the satellite for the terrestrial observer is explained by the same phenomena. Here it is also necessary to consider that from Earth we estimate only the angular speed of movement of the artificial satellite, and not so linear. For this reason the geostationary satellites are visible as not movably hanging stars which do not move together with other stars, despite rotation of Earth.
Entry of the artificial satellite into a shadow of Earth and exit from a shadow
If you had to watch long the movement artificial satellite, you could notice strange effect. Brightness yet of the satellite which did not reach the horizon suddenly decreases, and the satellite disappears. No, the satellite did not fall though the observer also could see several bright gleams at the time of right after his disappearance. Just the artificial satellite came into Earth shadow. Earth shadow cone which is trying to keep step with it in space does not influence observation of stars and planets in any way, but causes lunar eclipses and makes impossible visual observations of the artificial satellite. In the same way, having come out of the terrestrial shadow, the satellite can suddenly appear in the night sky.