Multiple Exposures Of The Sun

Stormbringer_X1 writes "This image holds many first. Called an analemma (a figure 8 loop), it is a multiple exposure of the sun, where one observes the sun at the same time of day, over the period of a year. The patience and dedication to pull this off are emphasized by the fact that there are so few in existence (7 total including the first in 1979). It is the first analemma imaged in a single calendar year, the first on the southern meridian, and the first in Greece. The author has other images from 2002 that will be available soon. So stay tuned. Here is an image from NASA archives"

Comments

Bah

[0x0d0a]

Bah, looks like 3 minute job with a white paintbrush in the GIMP. :-)

Seriously, though, at least some of this *has* to be a photo-manipulated composite, or else they never would have gotten that cloud in the background.

Film

[Xner]

From the article:

Incredible as it may sound, only seven times has someone ever managed to successfully image the solar analemma as a multi-exposure on a single piece of film.

"Single piece of film" is apparently one of the requirements. You could do it with a digital camera, but then it wouldn't count...

The shadow knows

[tdemark]

There is nothing wrong with the image.

41 pictures were taken with a solar filter on - after which the negative was unexposed except for the 41 "dots" that are the sun.

The solar filter is then taken off. The photographer waits until the frame looks good and the negative is then exposed one more time to "add" the foreground. The cloud and the Parthenon are only exposed once.

Judging from the shadows and the fact that the suns are due south, the foreground shot was taken in the morning (lit from left, which is east).

- Tony

Seven analemma?

[Anonymous Coward]

There are definitely more than just seven analemma exposures in existence. There was an issue of Sky & Telescope with six by amateur astronomers alone.

Re:What about the "wiggle"

[toybuilder]

For much of the last month or so, I've been studying techniques for accurately predicting the position (and some other parameters) of the sun at any given time of day and then setting up experiments to verify the results.

(It's not exactly fun work, especially having to get up at 5 am to prepare for the 6:30 sunrise measurements.)

The wobbles you see probably can be attributed to being off by a minute or so in taking each of the multiple exposures.

The diamter of the sun is about 0.5 degrees (31.48' according to the page accompanying the image). A one minute delay in taking the shot will mean the sun has moved (for example on 5-1-2002) about .3 degrees in azimuth, and .16 degrees in elevation. It's also possible that the camera itself was slightly mispointed (nudged? wind? who knows?)

There's 41 images taken between January 12 and December 21, all supposedly at 10:28:16.

The sun would start at (149.99,22.53) (azimuth, elevation), move upward and to the left in time until June 12 where it reaches (112.84, 60.88) and then starts to move downward until June 27, where it reaches (111.64, 60.47) and starts to swing back toward the right, until November 27 (152.86, 25.75), where it'll start swinging back to the left until his last position at (151.55, 22.72).

The sun would have reached it's "lowest" point in 2002 on 12-28 at (150.59, 22.48).

I originally thought the wobble might be due to atmospheric ("optical air mass") refraction variation due to tmperature and barometric pressure, but at those elevations, those effects turn out to be negligible.

This program from NREL will let you calculate the position of the sun and some of the properties that affect its perceived position. If you don't want to compile a program on your machine, you can check out the a href="ssd.jpl.nasa.gov/horizons">web-based "ephemeris" calculator from JPL.

Extreme photography.

[mnmn]

How about using ISO 25 speed film in a camera with an EXTREMELY tiny aperture so that the whole exposure takes 1 year?? How about using a field camera maybe 6x7" kodak pan film?

The result will be the sun painting the sky strip by strip. Now that should be a first.. with the trees superimposed throughout the year.

Come to think of it, we can aim the camera at a mall or busy street area. With the blurs, you could see where people stand most and what color clothes they wear. You can definitely make out the dots where homeless people sit. Sounds like a feasable project... hmmm..