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Comment by colanderman | Hacker News Reader

Have you ever looked at the moon while driving? It stays in the same position relative to the car, if the car is not turning.

Plane on autopilot + camera steadied by plane body + fisheye lens (which he was using) makes this very believable.

EDIT: not to mention, we are all hurtling around the Earth at around 1,000 miles per hour AS WE SPEAK. If that doesn't produce trails (it doesn't, see my math below), a few extra hundred MPH in a plane doesn't change jack squat.

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Sorry, I still don't believe it. Even with a fisheye lens and an incredibly stable aircraft, you're still going to see trails. If you don't believe me, I invite you to try it.

EDIT: I assume all the downvoters can provide us with links to their libraries of long-exposure, night aerial photography without using gyros?

See my edit. The only trails you will see are due to the rotation of the earth; not the movement of the plane.

EDIT: MATH: Assume the horizontal FOV is ~90 degrees (conservative according to Wikipedia). 30 (time) seconds around the Earth is (90/360)/(24x60x60/30) = 1/720 of that field. Meaning, you'd need a 720 px image to even see one PIXEL of blur due to the rotation of the Earth. The additional velocity of the plane contributes MUCH LESS than this; hence it is not visible.

Running some rough numbers:

If a 10mm lens can capture ~120° angle of view, then the image at 1024 px (low quality) represents 0.117° per pixel. In the 30s exposure, there is < 3 px represented by many stars, so that's 0.351° of tolerance.

How often have you flown in an airplane with less than 1/3 of a degree of drift on any axis over 30 seconds?

Yes, I'm quite familiar with the rotation of the earth and its effects on long exposures (I do some astrophotography myself). I'm not referring to that here, but rather to the normal instability of an airplane.

EDIT: I'm not just referring to pitch, but also to roll, yaw and vibration.

Seeing as 1/3 degree drift in a plane traveling 700 MPH translates into nearly 300 feet of elevation gain/loss; and that the seat-back altimeter readouts on commercial airlines I've flown in never seem to deviate more than 10 feet from the set altitude, I'm gonna guess every auto-piloted flight I've been on drifts less than that.

Not to mention that these are not the first pictures of stars this guy has taken from a plane: http://www.pbase.com/flying_dutchman/image/155755548

Alright, you've convinced me. To be fair, most of this guy's other night aerial photos either have shorter exposure times or exhibit some obvious trails in the stars (even the one you posted shows considerably more streaking in the stars).

Taken out of context, the few photos included in this post did seem more suspicious, but it looks like a combination of very good/stable conditions and a lack of resolution to notice more streaking.

I thought it was worth letting you know that I upvoted this comment for conceding the debate when presented with evidence. This is a commendable skill, one which many of us lack, and which all of us occasionally forget to exercise.

Yes, I also upvoted that comment and the one he made before. This is how a debate should look like - both sides present their reasoning using (however rough) numbers and facts, and settle on the result evidence suggests. Thank you for reminding us how adults should talk, and - if you forgive going meta - thanks @nitrogen for reminding us to remind this ourselves :).

And I upvoted his still-grayed-out original post. This is what figuring things out looks like. It was a reasonable thing to bring up when examining something this bizarre.

The vibration is still going to kill you, though. You don't get pinpoint stars like that in a 30 sec exposure on a tripod on a vibrating surface. Unless it's doing active image correction, I find it implausible.

1. Have you ever been on a commercial airliner? There's not really much vibration. (Yes, there's vibration, but the amplitude is not more than like a millimeter.)

2. Mechanical image stabilization exists and is common. Not sure whether fisheye lenses have it, but:

3. Fisheye lenses GREATLY reduce parallax error. Do the math out.

4. The vibration would NEED to be rotational, not lateral, for all the same reasons discussed above (stars are too far for lateral motion to change their apparent position). However little lateral vibration there is in an airplane, I guarantee there's even less rotational vibration. Sound/vibration simply doesn't work that way.

You are not incorrect about anything. The only exception to the challenge you are making could be in that assumption that the images were intentionally doctored with to disguise/obfuscate/alter reality. In face: They were intentionally doctored, there has been an editor on these files. The originals will no doubt provide further math.

EDIT: Note that JPC seems to be preparing for a naming-of-feature challenge, which in itself is an interesting aspect of the whole story! Go for it, I say!

Skepticism is mandatory on HN, except when it's forbidden.

People have taken to down voting things that they don't agree with, it's sad because it stops debate and contrary opinions.

Down vote trolls, down vote personal attacks, down vote propaganda - sure.

> People have taken to down voting things that they don't agree with, it's sad because it stops debate and contrary opinions.

Downvoting to express disagreement was explicitly sanctioned by pg back in February 2008.

https://news.ycombinator.com/item?id=117171

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