2463: Astrophotography

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Astrophotography

Title text: [One hill over, a competing astrophotographer does a backflip over a commercial airliner while throwing a tray of plastic space stations into the air, through which a falcon swoops to 'grab' the real one.]

Explanation

Astrophotography is the practice of taking pictures of astronomical objects. Sometimes it is specified as a hobby, as opposed to the work of professional astronomers. Astrophotographers like to take pretty pictures of all sorts of objects in the sky, but photographing the Sun is a popular subgenre within the field, especially if something is transiting in front of it. Typical things include planes, the International Space Station (ISS), and the Moon (Solar eclipses).

During the Total Solar Eclipse 2017 visible across US it was possible to see the ISS pass in front of the Sun during a partial part of the Eclipse (from a site that was later in the total Eclipse zone.) This was photographed and filmed by Destin from Smarter Every Day and can be seen in his video Space Station Transiting 2017 ECLIPSE. (Go to the time of the flyby of the ISS in the video here).

Two years later he did another episode South American Eclipse - Argentina. In this video there was only the moon eclipsing the sun, at first, but then towards the end the sun begins to set behind the distant mountains creating a shadow scenario between Moon and mountain shadows as displayed in this comic.

This comic thus combines those two videos, which Randall must have seen, and then adds several more layers caused by the Astrophotography community's One-Upmanship. The practice of "one-upmanship" refers to the practice of achieving something superior to what another has achieved, or "getting one up on" them. The term originated in the 1950s or earlier.

The caption claims that the photo shown in the comic is the result of a continuous string of one-upmanship among astrophotographers in a community, each striving to one-up the other.

In this comic there seems to be an abundance of things:

• The ISS can be seen transiting in the upper center. (as in this picture)
• There is an ongoing partial solar eclipse so the view of the Sun is partially obscured by the Moon in the upper right quadrant.
  • These two things are what Destin managed in his first video.
• The Sun is setting or rising from behind a hill while partially eclipsed.
  • This is what Destin managed in his second video.
• This photographer achieved a combination of those two plus several other ones-up those two videos.
• Megan is standing slightly below the peak of a hill and seems to be juggling, with five balls, which are also in front of the sun. One or more of those balls might actually be sunspots or the planets Mercury or Venus.
• Cueball is standing at the peak of the hill, shooting an arrow from a bow, one arrow has pierced what at first appears to be one of the juggling balls, but may be a Transit of Venus.
  • A simultaneous Eclipse and Transit of Venus is actually expected in the future, but not until April 5, 15232 (13211 years after the publishing of this comic).
    • It would though likely be easier to make the arrow "hit" Venus than one of the juggled balls, as the planet's angular velocity is significantly lower.
    • The other four balls are too large that any of them could represent Mercury, the only other planet that can transit the Sun, when seen from Earth. But Megan has been careful to make one ball go so much higher than the middle two, that it seems to fit that Venus has been shot out from between them.
  • Given the long time before this could happen, it could also just be five balls. And in that case the easiest way to make this picture is to put the fifth ball on the arrow before shooting it.
• Two airplanes pulling banners with the words "nice" and "shot" (which could refer to both the archer and the photographer) are flying in opposite directions above them. (Airplane banners that are not continuous sheets are made with thin support lines spanning the openings, which explains the presence of the apparently unsupported central disc in the "O".)

Taking the picture required precisely scheduling and arranging the relative positions of several of the various subjects (and photographer) to coincide with the predictable but rare conjunctions of the rest of the scene, as well as special equipment:

• All this had to be timed very very precisely as the transit of the ISS only takes a second.
• A solar filter must be used to photograph the sun without overexposing the image or even damaging equipment.
• The photograph must be taken during a partial solar eclipse. These only happen a few times per year and are only visible in part of the world.
• The photographer must be quite far away with a telephoto lens to achieve the visual scale. A nearby person appears larger than the moon. It is possible to photograph the silhouette of a person or a cityscape in front of a full moon, making the moon look comparatively larger or smaller by adjusting the distance to the closer subject, and then the lenses used by the photographer to make them both fill just the right amount of the frame.
  • The photographer would need to be approximately one kilometer distant if the image is a typical human scale. Both Sun and Moon have a visual angle of about 0.5 degrees. The characters are approximately 1/5 the Sun's height giving a 0.1 degree visual angle. A right triangle with a height of 1.7 meters (a typical human height) spanning 0.1 degrees for the side angle, the distance would be 974 meters (3195 feet) from Cueball and Megan.
  • The photographer taking this image would need a high magnification 2-meter (2000mm) equivalent lens or a shorter lens with a cropped image to fill the frame as in the comic. Long telephoto lenses like those are uncommon for most photographers, but would be available among astrophotography groups.
• The exposure time of the photograph had to be short enough to capture clear silhouettes of the ISS, the juggling balls and the arrow while these were in the air.
• The mountain had to be in a location that would happen to see the ISS passing in front of the sun at the same time as the sun was rising from behind it.
• The subjects had to achieve a moment in which four juggling balls were in the air and an arrow had pierced the point where Venus would appear, while sideways relative to the sun's light, with still near normal intensity.
• The planes also needed to be flying in the correct directions for the text of the signs to be visible, and with very precise timing for them to be in the correct positions to read "Nice" as coming before "Shot" just as the ISS passes by.
• The sky (at least between the photographer and the Sun) had to be free of clouds.

The title text describes a similarly outlandish photo attempting to one-up Cueball and Megan, done simultaneously on the next hill over, thus a place where the same ISS transit can be seen:

• A commercial airliner is flying in front of the Sun, thus this has to be timed with the flight plan (or it has to be chartred, to pass there at the correct height and position, within a few seconds.
• The astrophotographer is performing a backflip such that they appear to be over the airliner.
• The astrophotographer is tossing several tiny models of the ISS from a tray, so they also appear in front of the Sun with the real one (like the joggling balls and Venus).
• A falcon is flying in front of the Sun, presumably intending to capture prey, in such a way that it appears to be snatching the real ISS out of the fakes. The falcon moves slowly compared to the ISS, so it just needs its talons to be on the line the ISS makes across the Sun, then a picture where it is close to the talons can be used. The other parts are slower than this.

Transcript

[Cueball and Megan stand on a hill with the dark yellow sun setting behind them. Outside the Sun's disc everything is black. All that can be seen is silhouettes against the sun. Cueball is at the top-left of the hill, holding a bow in his left arm, which has been recently shot, as indicated with lines along the string. The the arrow is to right, where it has speared a ball. Megan is at the bottom-right of the hill, juggling four other balls, one near her hand, two above her and one higher up than the path of the arrow. There are two planes going in opposite directions with banners on them with words readable against the Sun. Above the planes is the shadow of the International Space Station. Finally Sun is partially eclipsed by the moon in the upper right corner.]

[Banner 1]: Nice

[Banner 2]: Shot

[Caption beneath the panel]:

Our astrophotography community's one-upsmanship[sic] is getting out of hand.

Trivia

• Randall has commented on extreme photography in comics 1855: Telephoto and 1719: Superzoom, and the How To chapter "How to take a selfie".

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Discussion

So are any of those "balls" actually sunspots or the transit of Venus or something? 173.245.54.227 22:47, 14 May 2021 (UTC)

This looks like Destin from Smarter Every Day's lunar eclipse shot https://youtu.be/Nk0MRxXqo9s?t=610 108.162.219.78 23:20, 14 May 2021 (UTC)Yeedle

Destin also caught the ISS transiting during a previous eclipse: https://youtu.be/lepQoU4oek4?t=230 Astroboy (talk) 02:11, 15 May 2021 (UTC)

Yes and that was probably the one that needed to on up so I have added this to the explanation, before I read this coment. The other video has not much to do with transit. But that was also really cool, and I had not seen that one so thx. --Kynde (talk) 06:42, 15 May 2021 (UTC)

I now disagree with my self. Of course it is the combination of those two videos that are the backbone of the comic, with the other things put on top. Have added the second video to the ecplanation --Kynde (talk) 11:00, 17 May 2021 (UTC)

This is actually really cool. ISaveXKCDpapers (talk) 02:26, 15 May 2021 (UTC)

It might have been better with two planes that didn't look like they were dangerously within normal flight separation distances. Given they're not obviously 1000ft (300m) vertically apart (and very likely in Opposite Conflict, heading-wise) horizontal separation depthwise to the image should make the two similar models towing (similarly-sized?) banners noticeably off-scale to each other, even with the extreme foreshortening from the much distant cameraman. (Maybe the viewing angle 'up the mountain' would provide sufficient composite diagonal separation to comply with Reduced Flight Levels for two planes obeying hemispherical RVSM, but still with notable off-scaling.) They could be a stunt-pair, of course, asked for and given ATC dispensation (further complicated by the banner-towing) to cross absurdly close (by normal, sane standards) as per a fast-jet criss-cross at an airshow. It might have been even more impressive if one had been a notably 'bigger' class of plane (but silouetted at the same or smaller size) towing a similarly (give or take) rescaled banner. 162.158.158.131 02:43, 15 May 2021 (UTC)

That 1000ft separation rule only really applies to IFR flights at altitude. Under VFR (or, say, on approach where the aircraft can see each other) they can fly as close as is safe... whatever that might be. VFR flights can be scary close sometimes when crossing (especially when weaving through the corridors near to suburban airfields). I don't think the photo poses a particular problem in that respect. 141.101.98.38 09:03, 21 May 2021 (UTC)

I am really looking forward to seeing the simultaneous Eclipse and Transit of Venus 108.162.249.18 03:46, 15 May 2021 (UTC)

I look forward to reading Comic #2070397(ish?), and seeing if Randall revisits this! 162.158.159.122 13:19, 15 May 2021 (UTC)

The comic appears to say "one-upsmanship" rather than "one-upmanship". 141.101.98.46 17:16, 15 May 2021 (UTC)

One "one-upmanship" begets further multiple "one-upsmanship". (c.f. "Courts Martial", etc.) Or should they actually be "ones-upmanship"? ;) 141.101.98.30 17:56, 15 May 2021 (UTC)

"Sometimes it is specified as a hobby" "photographing the Sun is a popular subgenre within the field" seems like a perfect example of xkcd.com/1095 108.162.216.248 18:01, 15 May 2021 (UTC)

We are impressed with your creativity and determination and have a major international political issue we would like your guidance around. 108.162.219.204 19:33, 15 May 2021 (UTC)

i vote on changing it all to "ones-upsmansships" a la comic 1167. 172.70.34.162 13:04, 16 May 2021 (UTC)

Destin's video is in the second paragraph of the explanation of this comic For something that's not directly related to the content of the comic, that's quite a place of prominence. I don't think it should be there. At best, it should be moved to the trivia section as an example of astrophotography, not presented as fundamental to understanding this comic. Argis13 (talk) 19:44, 16 May 2021 (UTC)

As the whole comic is based on a combination of his two videos (also added the second) I think they deserve a very prominent place. It is obvious that Randall saw those two and made this tribute. --Kynde (talk) 11:00, 17 May 2021 (UTC)

Now that the comic points out the transit of Venus won't occur during an eclipse for thousands of years, it dawns on me the easiest way of achieving the apparent arrow puncture in the trick photo would be to put the ball on the arrow before shooting it. 172.69.62.9 05:03, 17 May 2021 (UTC)

Done --Kynde (talk) 11:11, 17 May 2021 (UTC)