But if you turned round 180 degrees after taking that photo you would see crepuscular rays. The shadows are parallel, passing overhead, so they appear widest overhead and converge at both horizons.
There is no difference between crepuscular and anticrepuscular rays, any more than there is between the train tracks stretching out in front of you and those behind you. It's just rarer to be able to see them all the way to the horizon opposite the sun.
The shadows will only appear parallel on a photo if the camera is looking either straight up or straight down. The photo from space has the camera pointing at an angle, so the shadows appear to converge. I think that's what you are saying, but calling them "anticrepuscular rays" is rather confusing because that term applies to viewing the same shadows from the ground so that they appear to converge opposite the sun.
Yes, everything is defined by observer position.
My point about cropping the photo is that it doesn't change the nature of the photo. The camera was in the position it was in. If you go back to my post I'll think you'll see that. But that was a side note.
I don't think that last bit is right. The camera pointing at an angle doesn't make the shadows appear to converge or diverge. It's the observer's position that does so.
The important part about the angle of the camera is that it can be difficult to tell from a photo of relatively ambiguous objects like clouds if the camera was angled or not. An angled shot can look like a straight down shot.
And in the case of the photo Abishua was asking about... He was assuming the cloud shadows would be parallel in the photo because he was assuming it was taken looking straight down. I say the cloud shadows are not exactly parallel as he expected, because the camera was not pointing straight down. That's the simplest form I can put that in.
I then showed a cropped portion of a photo taken from a larger photo to prove that the illusion of the straight down angle can be just that; a seductive illusion.
(Incidentally, when I first linked to that photo, I also assumed that the camera was pointing straight down and the shadows were parallel. It wasn't until Abishua pointed out that they aren't that we took a second look, so kudos to him.)
Of little consequence but interesting to think about...
If you do have to be on the ground to see a crepuscular ray, exactly at what point above the ground does a crepuscular ray become not a crepuscular ray?
After some thought here's my answer:
The anti-solar point is defined by the observer and is a point on the celestial sphere opposite to the sun from the observer's viewpoint. You don't have to be on the ground for that to be true, and the anti-solar point doesn't have to be in the sky from your viewpoint.
Crepuscular and anti-crepuscular rays are created by the contrast between the brighter areas where the sunlight is being scattered (Rayleigh scattering) and the darker areas of the shadows. The fundamental issue in our discussion is that they are undistorted. In the case of anti-crepuscular rays, they aim directly at the anti-solar point on the celestial sphere as defined by our viewpoint.
But if we are above the clouds and seeing shadows cast by the clouds on the earth's surface, the shadows will be distorted and will not point directly to the anti-solar point. It's not the same situation.
This is the question. In this photo below, are we seeing shadows and rays in the atmosphere, or are we seeing the shadows of clouds cast on the earth's surface? If the former I say that these are still anti-crepuscular rays
and they are aimed at the anti-solar point on the celestial sphere as defined by the observer's position, even though that position is in space. That's kind of a mind-bender but it would have to be true.
If they are shadows cast by the clouds on the earth's surface then they are
mostly aimed at the anti-solar point but are distorted and are not anti-crepuscular rays.
Regardless, the observer's position determines whether they appear to converge or diverge. Whether they are aimed directly at the anti-solar point or not won't change that.