Astronomy Picture of the Day 7-09-02

NASA ^ | 7-09-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2002 July 9 Analemma Credit & Copyright: Vasilij Rumyantsev (Crimean Astrophysical Obsevatory)

Explanation: If you took a picture of the Sun at the same time each day, would it remain in the same position? The answer is no, and the shape traced out by the Sun over the course of a year is called an analemma. The Sun's apparent shift is caused by the Earth's motion around the Sun when combined with the tilt of the Earth's rotation axis. The Sun will appear at its highest point of the analemma during summer and at its lowest during winter. Analemmas created from different Earth latitudes would appear at least slightly different, as well as analemmas created at a different time each day. The analemma pictured to the left was built up by Sun photographs taken from 1998 August through 1999 August from the Ukraine. The foreground picture from the same location was taken during the early evening in 1999 July.

[petuniasevan]

Astronomy Fun Fact:

Analemma: A graduated scale in the shape of a figure eight, indicating the sun's declination and the equation of time for every day of the year and usually found on sundials and globes.

ETYMOLOGY:
Latin, sundial, from Greek analmma, from analambanein, to take up.	Get on the APOD PING list!

[petuniasevan]

APOD PING!

[trussell]

That is too cool!! Thank you petuniasevan.

[MeekOneGOP]

Extraordinary picture. Thanks!

[antonz]

This is good work.
Thanks

[BossyRoofer]

Amazing, good work!

[MozartLover]

bump

[RightWhale]

The analemma photo takes a year, during which time the camera has to be left bolted to the same spot and not moved at all. The brightnesses of the suns depend on atmospheric conditions at the times the shutter is opened. The film is not advanced between each exposure, so some cameras are not suitable for this application. The background image of the hills and clouds would be possibly be taken at a separate time. The shutter can be controlled electronically so it opens at exactly the same time each day, or a very dedicated astronomer could operate the camera manually.

[dansangel]

Most excellent....thank-you for bringing this to us today!

[altair]

Very cool. Thank you for the ping, as always.