by Sam » Thu Apr 05, 2012 5:20 pm
Irishman wrote:I have one question. I notice that the horizon on the left of the image is slanted at about 50 deg from the axes, but on the right side the horizon is almost vertical. What causes this change?
As I understand it, there were a series of pictures taken of the sky throughout the night. The camera angle was changed as the Earth rotated. I suspect that the answer involves the fact that the Earth is a sphere, and that the rotation of Earth is not in the same plane as the ecliptic, i.e. the zodiacal light that the image is tracing. The other comment was that the camera location was changed. In theory that could cause it, but I would expect the photographer to attempt to align the camera appropriately, and regardless, that should be absorbed when the images are stitched together for the panorama. Camera alignment might effect the shape of the image edges, but not the alignment of image components to each other.
Can anyone explain better?
In Hawaii on or around the night of April 3, 2011, the ecliptic plane in the west after sunset (on the right) comes straight up from the horizon and passess overhead. Later, before sunrise, however, the ecliptic meets the eastern horizon at the 50° angle you mentioned. The camera location change has nothing to do with the angle the ecliptic meets the horizon; the same angle would appear if the camera wasn't moved at all.
What makes this picture hard to comprehend are indeed the horizons: as your eyes move from right horizon to left horizon, you're also moving forward in time (later in the night). This is a 4D image projected onto two dimensions! Take out the horizons, however, and you just have a simple 360° wrap-around panorama which could have been taken from space.
--
Sam
[quote="Irishman"]I have one question. I notice that the horizon on the left of the image is slanted at about 50 deg from the axes, but on the right side the horizon is almost vertical. What causes this change?
As I understand it, there were a series of pictures taken of the sky throughout the night. The camera angle was changed as the Earth rotated. I suspect that the answer involves the fact that the Earth is a sphere, and that the rotation of Earth is not in the same plane as the ecliptic, i.e. the zodiacal light that the image is tracing. The other comment was that the camera location was changed. In theory that could cause it, but I would expect the photographer to attempt to align the camera appropriately, and regardless, that should be absorbed when the images are stitched together for the panorama. Camera alignment might effect the shape of the image edges, but not the alignment of image components to each other.
Can anyone explain better?[/quote]
In Hawaii on or around the night of April 3, 2011, the ecliptic plane in the west after sunset (on the right) comes straight up from the horizon and passess overhead. Later, before sunrise, however, the ecliptic meets the eastern horizon at the 50° angle you mentioned. The camera location change has nothing to do with the angle the ecliptic meets the horizon; the same angle would appear if the camera wasn't moved at all.
What makes this picture hard to comprehend are indeed the horizons: as your eyes move from right horizon to left horizon, you're also moving forward in time (later in the night). This is a 4D image projected onto two dimensions! Take out the horizons, however, and you just have a simple 360° wrap-around panorama which could have been taken from space.
--
Sam