APOD: Solargraphic Analemmas (2022 Jul 02)

[APOD Robot]

Solargraphic Analemmas

Explanation: For the northern hemisphere June 21 was the summer solstice, the Sun reaching its northernmost declination for the year. That would put it at the top of each of these three figure-8 curves, or analemmas, as it passed through the daytime sky over the village of Proboszczow, Poland. No sequence of digital exposures was used to construct the remarkable image though. Using a pinhole camera fixed to face south during the period June 26, 2021 to June 26, 2022, the image was formed directly on a single sheet of photographic paper, a technique known as solargraphy. The three analemmas are the result of briefly exposing the photo paper through the pinhole each day at 11:00, 12:00, and 13:00 CET. Groups of dashed lines on the sides show partial tracks of the Sun from daily exposures made every 15 minutes. Over the year-long solargraphic photo opportunity clouds blocking the Sun during the pinhole exposures created the dark gaps.

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[VictorBorun]

my attempt at solarography

and an overlay with a stitched panorama from the same balcony

[XgeoX]

Victor, those are wonderful!

Eric

[Joe Col]

So that's how the idea of barcodes surfaced...Nice

[orin stepanek]

I thought they were made by putting film in a tin can with a
pin hole opening and placing it in a dark spot and facing an
opening to the horizon! Shows what I know! These guys
have pretty sophisticated cameras!
https://apod.nasa.gov/apod/ap090626.html

[DonB312]

my attempt at solarography

Thanks for sharing those with us Victor.

[Larry from Boston, USA]

This is one of my favorite APODs of the past few years. The technical bits are inspiring (I don't understand Polish but the You Tube video linked from the explanation was great), the composition is great, and the orbital mechanics so nicely displayed! 10/10.

[johnnydeep]

I truly don't understand how this image was made. Oh well, analemmas seem to be my nemesis. Sure, the three differently positioned analemmas are from three times an hour apart (why three?), taken by a pinhole camera every day over a year. But what exactly is causing the dashed lines on the sides, and why are there only two sets of these not three? And why are they only half-figure-eights?

[alter-ego]

Analemma1_1024c.jpg
I thought they were made by putting film in a tin can with a
pin hole opening and placing it in a dark spot and facing an
opening to the horizon!
...

That's what he used, but he added an electronic shutter to "snap" the images.
The thermal-sensitive paper essentially creates a negative of the final APOD image: The sun makes a dark spot, the landscape is light, silhouetted against the darker background. Colorizing is a post-processing step. He did a nice job creating that image.

[alter-ego]

I truly don't understand how this image was made. Oh well, analemmas seem to be my nemesis. Sure, the three differently positioned analemmas are from three times an hour apart (why three?), taken by a pinhole camera every day over a year. But what exactly is causing the dashed lines on the sides, and why are there only two sets of these not three? And why are they only half-figure-eights?

He timed, and limited, the exposures to only capture 3 full analemmas. Technically, he could have captured 16 full analemmas, but only middle full three would be clearly identifiable. All the ones on each side would be overlapped kind of a mess, with only partial analemmas near the edge of the image. Instead, he took "left" and "right" halves to artistically accent the center three. Interestingly, the "left" halves consist of images between the summer solstice and Aug 31 (the analemma's intersection point), and images between winter solstice and April 13 (also the intersection point). The "right" halves are images taken between Apr 13 to the summer solstice, and images between Aug 31 to the winter solstice. (Sorry if my description is confusing.

All the exposures were made in one year. The full analemma exposures are all sequential, but the left and right halves are staggered. It'd be neat to make a time-lapsed simulation gif to visually show the development of the image.

Added graphic of showing Analemma halves and segment dates:
Left Half = RED
Right Half = BLUE
 

Not a time lapse, but visual should help.

[alter-ego]

...
But what exactly is causing the dashed lines on the sides...?

I missed answering this part. As the description states, the dashed lines are extended exposure times so that the sun trails instead of just forming a dot. The intermittent dark regions within trails are clouds blocking the sun.

[johnnydeep]

...
But what exactly is causing the dashed lines on the sides...?

I missed answering this part. As the description states, the dashed lines are extended exposure times so that the sun trails instead of just forming a dot. The intermittent dark regions within trails are clouds blocking the sun.

Thanks for this and your prior response, but I still don't get it. Were the long exposure times necessary to take the pin hole camera shots? I'd think not since it's the bright sun being imaged and not a dim nighttime star. Why couldn't the result just be the three full analemmas shown in the middle?

[orin stepanek]

Analemma1_1024c.jpg
I thought they were made by putting film in a tin can with a
pin hole opening and placing it in a dark spot and facing an
opening to the horizon!
...

That's what he used, but he added an electronic shutter to "snap" the images.
The thermal-sensitive paper essentially creates a negative of the final APOD image: The sun makes a dark spot, the landscape is light, silhouetted against the darker background. Colorizing is a post-processing step. He did a nice job creating that image.

Thanks! I admire these photographers that send these awesome photos to APOD!

[alter-ego]

...
But what exactly is causing the dashed lines on the sides...?

I missed answering this part. As the description states, the dashed lines are extended exposure times so that the sun trails instead of just forming a dot. The intermittent dark regions within trails are clouds blocking the sun.

Thanks for this and your prior response, but I still don't get it. Were the long exposure times necessary to take the pin hole camera shots? I'd think not since it's the bright sun being imaged and not a dim nighttime star. Why couldn't the result just be the three full analemmas shown in the middle?

→ For the sun trails (to the left and right of the full analemmas), the exposure times were somewhere between 15min and 20min long. They were that long only to create the trails, not for improving light collection.
→ I estimate individual sun exposures to be 10's of seconds. This exposure time is longer than needed to image the sun on a cloudless day but seems quick to me for solargraphy and the paper that's used. Only the sun can be recorded during a single image having these exposure times. The landscape, however, benefits from cumulative exposures over the year.
→ Not sure what you're asking. The result is what was wanted. If no sun-trails were made, the result would be just the 3 full analemmas. To capture this image, the camera shutter opened thousands of times over the year. Personally, I like the half-analemmas on each side. The composition of tilted full and half analemmas on each side of the central, due south analemma is a new and artful representation the seasonal sun.

[MarkBour]

I missed answering this part. As the description states, the dashed lines are extended exposure times so that the sun trails instead of just forming a dot. The intermittent dark regions within trails are clouds blocking the sun.

Thanks for this and your prior response, but I still don't get it. Were the long exposure times necessary to take the pin hole camera shots? I'd think not since it's the bright sun being imaged and not a dim nighttime star. Why couldn't the result just be the three full analemmas shown in the middle?

→ For the sun trails (to the left and right of the full analemmas), the exposure times were somewhere between 15min and 20min long. They were that long only to create the trails, not for improving light collection.
→ I estimate individual sun exposures to be 10's of seconds. This exposure time is longer than needed to image the sun on a cloudless day but seems quick to me for solargraphy and the paper that's used. Only the sun can be recorded during a single image having these exposure times. The landscape, however, benefits from cumulative exposures over the year.
→ Not sure what you're asking. The result is what was wanted. If no sun-trails were made, the result would be just the 3 full analemmas. To capture this image, the camera shutter opened thousands of times over the year. Personally, I like the half-analemmas on each side. The composition of tilted full and half analemmas on each side of the central, due south analemma is a new and artful representation the seasonal sun.

@johnnydeep, maybe not your nemesis, I think you understand them well enough to ask intelligent questions!

So, as June 21 is the summer solstice and "peak" day, let's look at a few sample daily exposures. If by some chance I have this figured out correctly.

On June 20, like many days leading up to the solstice, you'd:

• Leave the shutter closed up until 13:15,
• except for a very brief exposure at 11:00, 12:00, and 13:00.
• Then open from 13:15-13:30, closed from 13:30-13:45,
• open from 13:45-14:00, closed from 14:00-14:15,
• open from 14:15-14:30, closed from 14:30-14:45,
• open from 14:45-15:00, closed from 15:00 for the rest of the day.

The result, for June 20 et al, you'd get 3 dots near the middle, and 4 line segments on the right half of the sky.

June 21:
This day is special. You take more exposures:

• You first open the shutter from 9:00-9:15, close the shutter from 9:15-9:30,
• open from 9:30-9:45, close from 9:45-10:00,
• open from 10:00-10:15, close from 10:15-10:30,
• open from 10:30-10:45, close from 10:45 to 13:15,
• except for a very brief exposure at 11:00, 12:00, and 13:00.
• open from 13:15-13:30, closed from 13:30-13:45,
• open from 13:45-14:00, closed from 14:00-14:15,
• open from 14:15-14:30, closed from 14:30-14:45,
• open from 14:45-15:00, closed from 15:00 for the rest of the day.

The result, for June 21, you'd get 4 bright line segments on the left half, 3 dots near the middle, and 4 line segments on the right half.
after June 21, drop the right half captures and keep the left half captures.

So, on June 22 and for many days thereafter:

• For the day, you first open the shutter from 9:00-9:15, close the shutter from 9:15-9:30,
• open from 9:30-9:45, close from 9:45-10:00,
• open from 10:00-10:15, close from 10:15-10:30,
• open from 10:30-10:45, close from 10:45 for the rest of the day,
• except for a very brief exposure at 11:00, 12:00, and 13:00.

The result, for June 22 and on, you'd get 4 bright line segments on the left half and 3 dots near the middle.

If that much makes sense, then we can go back to @alter-ego 's fine diagram for the more complete picture of the year. Really, they were capturing more than 4 line segments on each half, it looks like maybe about 7, but the idea is an easy extension of my description to more 15-minute segments earlier in the morning and later in the afternoon. You do the 11:00, 12:00 and 13:00 exposures year-round, so you get the 3 central full analemmas, which I realize you already understood. But you capture these morning segments only from June 21 to August 30 and December 21 to April 13, and you capture the afternoon segments from April 13 to June 21 and from August 30 to December 21. Those are thus drawing smeared-out half-analemmas.

Maybe I have this right. And maybe that helps it make more sense.

[johnnydeep]

Ok, so in summary:

So, doing it this way is solely for the purpose of the visual effect. Sadly, the aesthetic was lost on me and it just managed to confuse.