Starship Asterisk*

here is another fascinating look at an analema posted on
http://www.spaceweather.com
today

http://www.spaceweather.com/swpod2006/24dec06/tezel1.jpg

added- Renowned astrophotographer Tunc Tezel and his brother Cenk took dozens of pictures of the sun throughout 2006 and made the analemma, below. Look carefully. One of the suns in the analemma is eclipsed:

You can also see by examining the shadows on the ruins that the ruins themselves were not photographed during any of the analemma exposures.

Hi Alex, I contacted Anthony, the author of the photo, and asked him. This is what he told me: "There is no other choice since a photo of the foreground with the sun in
the same field of view will burn out the analemma image. In fact, I have
to shoot the foreground with the sun as far away as possible so as not
to endanger to the analemma image on the film and to also get a very
blue sky." Also, "No, we cannot shoot on the same day of the year (ex. every Sunday) since
the sun's motion across the sky in both azimuth and altitude varies
dramatically (due to its elliptical orbit around the sun, the earth
moves "faster" or "slower" depending on where it is during its orbit
about the sun). Just to give you an idea, there are times during the
year when I shoot every 4-5 days and other periods when I shoot every
2-3 weeks. For example, near the solstices, the sun moves the "slowest"
and it is there where successive exposures are spaced 2-3 weeks apart.
In contrast, around the intersection point between the two loops is when
the sun moves the fastest and my exposures are every 4-5 days.

Of course, how do I know when to precisely shoot? I analyzed the
ephemeris of the sun and derived a schedule where I shoot whenever the
sun has moved by 2.5 degrees in azimuth and/or altitude (usually
altitude) relative to my previous exposure. At times I have to shoot a
day early or late due to a forecast for bad weather."

Nice explanations.... Mick

[quote="Alex Bridger"]I am concerned about APOD Dec 23 - to me the analema is totally unrelated to the photo.

I think this location is at latitude 36 to 38 degrees N (Greece?) - first question

This location would not have such a low solar angle as this in mid winter? - second question

Not sure but I would guess this analema is a 40 to 50 deg N analema?

This photo was taken at 10 am ish - see shadows on second columns and quite unrelated to any of the solar spots shown - yes I realise filters have been used but maybe it was unrealistric of me to suppose one of those spots was a real solar spot for that photo?

Does anybody know how this photo was 'engineered'?

Many thanks for your help.

Alex.[/quote]

Hi Alex

Just in case you have not done it, clicking on the "Above, 47 seperate exposures" in the explanation to the APOD will bring up a webpage that has the image and exposure details. I'm unsure if this will help you but I hope that it does. Not that it is likely to matter but note also that the analemma was taken during the period March 30 2003 to March 24 2004.

Dave.

what difference does it make where this was taken from ? This geometry is true no matter where it was taken from, except from the polar regions of the earth.

I am concerned about APOD Dec 23 - to me the analema is totally unrelated to the photo.

I think this location is at latitude 36 to 38 degrees N (Greece?) - first question

This location would not have such a low solar angle as this in mid winter? - second question

Not sure but I would guess this analema is a 40 to 50 deg N analema?

This photo was taken at 10 am ish - see shadows on second columns and quite unrelated to any of the solar spots shown - yes I realise filters have been used but maybe it was unrealistric of me to suppose one of those spots was a real solar spot for that photo?

Does anybody know how this photo was 'engineered'?

Many thanks for your help.

Alex.