Blurred Stars?

Question

What causes the stars to look like this and what is it called?

http://www.astro.cf.ac.uk/sas/trails.jpg

Answer 1

It's called trailing and it happens because the Earth's rotating - the stars rise and set just like the sun. The camera's shutter was left open for 20 minutes to take that picture.

Rairden - thanks for the compliment! Some experience, but I got the specifics off the website :-)

Answer 2

Good answer by iridflare, who must have recognized the constellation Lyra, or deduced the scale (5-degree trails) purely by experience. Allow me to add that behind the star trails, the big bright blurry cloud is the Milky Way, which would not show up so well if this was a short exposure (but let's not turn this into an astrophotography lesson).

iridflare - it didn't occur to me to dig thru the website. Found the specifics now. Your screen name indicates experience. We both have way too much time on our hands, at least during daylight hours.

Answer 3

The reason stars look blurry to the naked eye is caused by astigmatism. Everyone has it by to different degrees. It's a visual defect in which the unequal curvature of one or more refractive surfaces of the eye, usually the cornea, prevents light rays from focusing clearly at one point on the retina, resulting in blurred vision. For normal vision, it isn't usually a problem. But when you try to look at a star that is light years away, no human eye is perfectly curved enough to prevent blurring.
In the case of your picture, its just because of a long exposure on a camera.

Answer 4

It's a long exposure picture. As the Earth turns, the stars appear to orbit.

Answer 5

To take a picture u must rotate your telescope in right ascension and declination. it must be rotated to make the stars still. The stars rotate 15 deg. per. hour.