Full Lunar Eclipse Feb 20/21 / Earth picture |
Full Lunar Eclipse Feb 20/21 / Earth picture |
Feb 7 2008, 10:26 PM
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Newbie Group: Members Posts: 2 Joined: 23-January 08 Member No.: 4025 |
I see we have a full lunar eclipse coming on Feb 20/21 (depending where you live).
I know that even during a full eclipse the Moon is still visible with a coppery hue, due to the refraction of light around the Earth. Now that we have a bunch of probes in orbit of the Moon, is there any plan / is it possible to take an image of the Earth from the Moon during totality? (or has this already been done?) I would think that a picture of the Earth surrounded by a red ring would be amazing! |
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Dec 26 2016, 02:52 PM
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Senior Member Group: Members Posts: 1669 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Below is a cropped view of an 8K animation zooming in along the Earth's limb at a scale of 1.6km per pixel, rotated 90 degrees clockwise. The first frame has the apparent sun about 45km off the limb (true sun 28km) though we're still technically in the umbra here. The edge of the umbra happens when the sun is about 85km up by the most widely used definition. We can see the sun is bright at the top where there is little extinction in the upper stratosphere. Below that is a blue layer due to ozone absorption in the lower stratosphere. The lowest part of the sun is red due to Rayleigh scattering in the lower troposphere just above the Earth's surface. The slight reddening effect of solar limb darkening isn't yet included in this model.
Here (click image below) is an animated crop of a 16K version that zooms in closer at 800m per pixel. The time lapse frames step every minute. The viewport shifts around the circumference of the Earth during the 3 hour period. The breaks in the ring shift noticeably even on the 1 minute time scale. This is caused by individual clouds that can be seen rising and falling in response to the Earths' rotation as if we're looking at the edge of a merry-go-round. Would be mesmerizing to see these shifting red arcs in reality. This is a long (real-time) version. If you were actually on the moon looking through a telescope a solar filter would be advisable with a neutral density of about 2, except around 4.5 in the beginning. The upper limb of the apparent (refracted) sun slowly sinks as the actual solar limb goes farther down below the Earth's limb. Between the first 2 frames of the animation, when the actual sun and Earth limb coincide, the apparent sun reaches around 35km off the limb. An alternate definition of the umbral edge (effective or notional eclipsing layer) would be when the angular velocity of the apparent sun is half the true angular velocity. By a rough calculation this happens when the true sun is about 34km up and the apparent is 47km. The velocities get within about 10% of each other when the respective limbs are 70km and 71km up. Here is a table of the actual and apparent values. Actual Apparent ------ -------- 74km 75km 65km 67km 55km 59km 42km 51km 26km 43km 0km 35km And just for fun here's a simulation of a lunar eclipse seen from the Earth, along with a more detailed description of all the simulations. ------------ (UPDATED DEC 28) ------------- -------------------- Steve [ my home page and planetary maps page ]
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