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

The shadow is not right

[MoobY]

If this is a single film photo, then there are a couple of things disturbingly wrong:

1. The shadow on the parthenon is no in line with the suns

2. the suns look like frightingly stupid white circles

3. the cloud in the lower left corner can only be on the picture if that particular cloud is there every time the film is exposed

What about the "wiggle"

[Optical Voodoo Man]

The clouds I understand. They either come from a single, unfiltered exposure or they were illuminated on any given exposure by the sun. The Parthenon superimposed I can see the same way. I think the big problem with this new image is the "wobble."

We go around the sun pretty smoothly, right? Shouldn't the path that the sun traces be a smooth one? On the image with the Parthenon, there is some time issues certainly, but the wiggle off of a "perfect" figure 8 shows that the camera wasn't always replaced exactly the same.

Nice try, nice image, but not as good as the second image pointed to in the article. That's why there are so few of these images around.

wrong time

[crow]

For something like this, wouldn't you want to use true local time instead of the time in the given timezone? Remember that time zones with the absence of daylight savings time are set up so that the sun is in the highest point in the sky at noon somewhere roughly in the middle of the time zone. Before time zones were created, each town set their clocks so that noon was true noon.

So the first thing to do in something like this is use GPS to determine your longituted and thereby compute the exact +/- UTC for your location.

Re:wrong time

[perdu]

I dont think that matters so much so long as it's the same time, though it will be highest around the local noon. The exact time of local noon changes a bit from day to day as the earth is going a little faster when it's closer to the sun. That's why you get the figure 8 pattern - otherwise it would be a straight line up and down.

Slash for Astronomy at M57:The Ring