by Chris Peterson » Mon Aug 18, 2014 4:12 pm
Psnarf wrote:I noticed on the full-size image that the South Celestial Pole star remains a dot; in similar photographs, Polaris is off-center leaving a small streak. If the perceived motion of Polaris off center is the result of Earth's precession, why then doesn't the South Pole star wander as well?
There is no central star in this image, just a couple of dim ones very close to the SCP. They do show very short trails.
The motion of Polaris over the course of a day has nothing to do with precession. It is simply that Polaris lies 0.7° from the NCP. Over long periods, precession results in the position of the NCP changing against the background stars, meaning that Polaris isn't permanently close to the pole.
North or south, there are stars extremely close to the poles. In the north, Polaris is the closest which is visible without aid. In the south, the closest star to the pole that can (barely, and not by everyone) be seen with the naked eye is more than a degree from the pole.
[quote="Psnarf"]I noticed on the full-size image that the South Celestial Pole star remains a dot; in similar photographs, Polaris is off-center leaving a small streak. If the perceived motion of Polaris off center is the result of Earth's precession, why then doesn't the South Pole star wander as well?[/quote]
There is no central star in this image, just a couple of dim ones very close to the SCP. They do show very short trails.
The motion of Polaris over the course of a day has nothing to do with precession. It is simply that Polaris lies 0.7° from the NCP. Over long periods, precession results in the position of the NCP changing against the background stars, meaning that Polaris isn't permanently close to the pole.
North or south, there are stars extremely close to the poles. In the north, Polaris is the closest which is visible without aid. In the south, the closest star to the pole that can (barely, and not by everyone) be seen with the naked eye is more than a degree from the pole.