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Atlantis and Hubble transiting the sun

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  • Atlantis and Hubble transiting the sun

    Amazing...

  • #2
    Thats a fantastic photo. Strange that this is the "first" one ever taken. With space travel becoming the norm instead of rare, one would think that an armature had already done this.

    Very cool

    rock~
    Civil engineers build targets, Mechanical engineers build weapons.

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    • #3
      The difficulty involved in successfully obtaining such a photo is hard to explain. Everything has to be just right. The size of the zone of visible transit on the ground is very small, and the orbital parameters of any low earth orbit satellite vary every orbit and must be updated daily at the least.

      I haven't checked but I suspect that the margin of error for Hubble's orbit may exceed the size of the zone in which the transit is visible. The problem is mainly due to the irregularity of Earth's gravitational field and the fact that on every orbit Hubble passes over a different part of the surface. Other factors are orbital decay that varies due to the orientation of the telescope as well as light pressure which also perturbs the orbit. Even the orientation of the spacecraft in respect of the gravity field will alter the orbital velocity because of gravitational tides.

      Gravitation anomaly map



      There is also the matter of time dilation caused by the orbital velocity relative to the Earth's surface. This is counteracted by the fact that the spacecraft is further out of the gravity well than the surface and the net term is that time on the Hubble is slightly faster than on the surface. The difference in "real" vs apparent position is surprisingly large. If not accounted for the cumulative relativistic error of a GPS satellite would be about 10 kilometres actual position per day.

      Then we have the ordinary but very important issues such as weather and availability of a suitable observing location at the right time and place. Those two items alone will make it very unlikely that anybody with the appropriate equipment is situated where an observation can be made.

      On top of that, it is no small feat to have everything work exactly correctly in the tiny window of time available to take the images.

      Hat's off to the fellow that did it.
      Last edited by Evan; 05-17-2009, 02:00 AM.
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        That is just awesome!

        Why are planets spherical? I realize they are not ball bearing smooth or round but why are they all essentially spherical?

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        • #5
          Originally posted by Ken_Shea
          That is just awesome!

          Why are planets spherical? I realize they are not ball bearing smooth or round but why are they all essentially spherical?
          Gravity pulls a molten planet into a sphere; that's the lowest energy configuration.

          - Bart
          Bart Smaalders
          http://smaalders.net/barts

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          • #6
            That and surface tension. The earth for the most part is still a molten ball of rock.

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            • #7
              Surface tension is a microsopic effect.

              Gravity pulls a molten planet into a sphere; that's the lowest energy configuration.
              The interesting thing about gravity is that it is the weakest force of the 4 known forces. It is about 10^39 times weaker than the strong force that hold atoms together. However, it is gravity that wins in the end.

              Planets are approximately round because even solid granite cannot resist the force of gravity once an object becomes larger than the asteroid Ceres which is a little under 1000 km in diameter.

              http://www.planetary.org/explore/top...ets/ceres.html

              This is also why the tallest mountain known is not on Earth but on Mars instead. Olympus Mons make Everest seem like a foothill. It is about three times higher at around 17 miles tall. This is possible because of the weaker surface gravity of Mars.
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              • #8
                Originally posted by Evan

                This is also why the tallest mountain known is not on Earth but on Mars instead. Olympus Mons make Everest seem like a foothill. It is about three times higher at around 17 miles tall. This is possible because of the weaker surface gravity of Mars.
                Now tell us you walked up that both way when you were a lad, with no shoes on and a slice of bread and dripping

                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • #9
                  Well, I didn't wear shoes most of the summer as I grew up in California and I rode my bicycle to school clocking over 1000 miles per semester. It was uphill both ways as I had to cross over a ridge on the way. The steepness of that ridge road is suggested by the name of the road, Hillgrade Rd.

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                  • #10
                    But what about the slice of bread and dripping ??
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                    • #11
                      Originally posted by Evan
                      The difficulty involved in successfully obtaining such a photo is hard to explain. Everything has to be just right.
                      Oh, dont get me wrong. I can imagine the need to be in the right place at the right time. My thought was more toward the amateur. I have seen the amateurs with the The CAS up at Perkins Observatory (shameless plugs) lock up on the shuttle, iss and the such with a dob by hand as well as program the encoders on the more expensive scopes for tracking and photography of the faster moving objects.

                      It just doesnt seem that far off to take this photo with a solar filter (or hydrogen alpha, that could be sweet) on the scope. And yes, our location does not seem to allow us the best transits, clear skys or seeing but every once in a while even we get lucky.

                      So couple all of the with groups that chase things such as the solar eclipse, it was just hard to believe that this was the first shot. But hey, some one had to do it first so congrats to Thierry.

                      rock~
                      Civil engineers build targets, Mechanical engineers build weapons.

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                      • #12
                        Originally posted by Evan
                        The steepness of that ridge road is suggested by the name of the road, Hillgrade Rd.
                        There is a Hillgrade Ave in Alamo http://maps.google.com/maps?f=q&sour...h&z=14&iwloc=A. Was that near your house?

                        That was long before I-680 existed, and I expect you felt like you were living on the outer frontier of the East Bay.
                        Allan Ostling

                        Phoenix, Arizona

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                        • #13
                          Did you notice how long the transit lasted? 0.8 seconds. The footprint of the visible zone was around 6 kilometers. Locking up on the shuttle isn't hard when you only have to be concerned about getting JUST it in your field of view. The problem here is being able to forecast long enough in advance where to set up in order to capture the event so that your field of view also includes the sun. It's like lighting a match with a .22 halfway to the target AND hitting the bull at the same time.
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                          • #14
                            But what about the slice of bread and dripping
                            Luxury! When I was growing up we had to farm our own bread while we were walking to school! And we didn't have shoes! AND WE LIKED IT THAT WAY!

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                            • #15
                              Well, that took me by surprise. They have street level view of the entire area including right in front of our old home. I lived just down Lunada Lane a short distance from Hillgrade. Here is the view at the intersection looking up Hillgrade. Amazing technology.



                              Back then it was 1/10 as many houses as there are now with large areas in walnut orchards and just open fields. It was excellent for sky watching and on one occasion we had taken my father's six inch telescope to the top of Mt. Diablo and discovered the comet Ikeya Seki on the same night as the official discovery. We knew nothing about reporting it but if we had the comet would have been named Ikeya-Seki-Williams.
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