pinhole camera made from a drink can

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Astronomy Picture of the Day
“”If every picture tells a story, this one might make a novel. The six month long exposure compresses the time from December 17, 2007 to June 21, 2008 into a single point of view. Dubbed a solargraph, the remarkable image was recorded with a simple pinhole camera made from a drink can lined with a piece of photographic paper. The Clifton Suspension Bridge over the Avon River Gorge in Bristol, UK emerges from the foreground, but rising and setting each day the Sun arcs overhead, tracing a glowing path through the sky. Cloud cover causes dark gaps in the daily Sun trails. In December, the Sun trails begin lower down and are short, corresponding to a time near the northern hemisphere’s winter solstice date. They grow longer and climb higher in the sky as the June 21st summer solstice approaches.””

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Ok you astronomers (amateur and otherwise), help me to understand why the slope of the sun’s apparent trajectory starts/ends at a virtual point on the left but is spread across a significant portion of the right horizon.

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(Edited by chrisgreaves on 19-Jan-09 06:42. added link to Analemma Over the Porch of Maidens )

>a virtual point
Good point.
It’s virtual.
Inspect, instead, the RHS.
Obviously all depends on the range of view.
If you go to the original site/image you’ll see that the RHS is truncated by a tree.
To see the effect of viewpoint, place your left hand palm facing the screen at the LHS of the image, and gradually slide your hand to the right (collecting dust, cat hairs etc).
Now imagine that in place of your hand, the camera had been oriented a bit towards the right; you’d get the same effect.
Now imagine what would happen (‘what you would see?”) if the camera’s view at the RHS had been a bit more towards the left.
Hope This helps.

(later) You might like to inspect this image

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Thanks Chris

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Chris

I love this web site. I have it as my home page so It’s the first thing to great me as I fire up the internet each day.

Here is an Analemma over the Ukraine taken in the evening.

Regards

Graeme

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>I have it as my home page
Oh. I haven’t sunk to those depths*(grin!)
It’s part of my “Weekly Dose” which I “Open All in Tabs”

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How could you not when you get awe inspiring pictures like this and like this on your screen each morning!

Regards

Graeme

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>How could you not when you get awe inspiring pictures like this and like this on your screen each morning!

Because I’ve got this (post 753,548) in my life each morning!

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Is that the fine feline you call Jupiter ? Or is it Saturn ?

Regards

Graeme

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