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The First Telescope Has Arrived for the Total Solar Eclipse in Cairns and “Black Sun” November 11, 2012

Posted by admin in : Astronomy and Astrophysics (ASTRO), Earth and Planetary Systems Sciences (EPSS) , add a comment

by JC Holbrook

Dr. Alphonse Sterling arrived safely in Cairns with telescope, mount, filters, cameras, and a suitcase. His excess baggage fees were unmentionable. The blue case is the body of the telescope. Alphonse is staying about 30 minutes to the west of Cairns in the Trinity Beach area in a very swank three bedroom apartment with ocean views. He will be sharing the apartment with scientific teammembers students Amy Steele and Roderick Gray.

In preparation for the eclipse, Alphonse has to create a ‘flat’ image as part of the calibration of the flaws in the telescope. When doing traditional night observing at an observatory, flats are taken of the dome. That is, before you start observing you put diffuse light onto the dome of the telescope and take a series of images. What is revealed is any specs of dust in the optics and other flaws. Next, the astronomer would go on to observe the celestial bodies and at dawn take another series of flats. When processing the images of the celestial bodies these flats would be used to remove the optical flaws thus flattening the images. This way what you have is just what is found in space not some artifact left by the optics of the telescope.

When doing observations of the Sun, daytime observing, creating a flat is not so simple. Alphonse has experimented with multiple different light sources to determine which is the best for creating a good flat.
What he found is he has to rig something up himself. That meant that we had to go to the hardware store to find the parts he needed!

After a long search we found: exacto knife, white cardboard, LCD flashlight, masking tape, electrical switch, compass. He had his own wire to create an external switch for his new light source. Over the next couple of days he will be putting everything together. I can’t wait to see what the final device will look like!

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Reports from PhysCon November 9, 2012

Posted by admin in : Astronomy and Astrophysics (ASTRO) , add a comment

NSBP members are reporting live from PhysCon. Check back here and follow the #PhysCon hashtag at Twitter for continuous updates.

Professor Mercedes Richards gives plenary talk, “The Incredible Tomography Imaging Technique”.

Tomography is the reconstruction of a multidimensional physical field from its integral projections in different directions.  Tomography can be used in astronomy for systems that are rotating, such as stars, binary systems, extrasolar planets and accretion disks.   Rotation of the system allows astronomers to see multiple angles of the system.  By observing light emissions from accretion disks and taking Doppler shift into account and other relativistic effects, it is possible to derive velocity profiles throughout the disk.   It then possible to reconstruct a velocity space “image” into an actual spatial image of the accretion disk.  Examples of systems include binary stars, and stars near black holes where the black hole is stripping off matter from the star.   Tomography can also be used to  study orbital mechanics.

Since the technique of Doppler tomography was introduced 18 years ago, it has been used to provide indirect images of accretion structures in close binaries which cannot be resolved spatially with the largest telescopes.   The more general technique of tomography has been used successfully in medicine, geophysics, archaeology, and oceanography to construct 3D images from 2D pictures or “slices” through the object collected at many positions around the object.  These slices or projections are represented by the Radon transform.   The 3D image is recovered through a summation process called back projection; and the overall image reconstruction procedure is known as tomography.  In astronomy, the technique can be readily applied to eclipsing binaries and rotating stars, which provide changing views of the system, and the process is called Doppler Tomography because the gas motions detected through Doppler shifts provide an image of the accretion flows in velocity coordinates.

Doppler tomography has been used successfully to produce images of accretion flows in a variety of interacting binaries including the cataclysmic variable stars and x-ray binaries.  It would not have been possible to create these images otherwise since these systems and too distant to be directly imaged.  The major highlights of Doppler tomography have been the discovery of spiral structures in accretion disks, and the comparison of gas stream tomography maps to hydrodynamics models.

Professor Mercedes Richards is in the Department of Astronomy and Astrophysics at Penn State University.  Originally from Jamaica, she attended the University of the West Indies where she graduated with special honors in physics.  She attended graduate school in Canada, earning her Ph.D. at the University of Toronto.   She was recently elected president of the Close Binary Stars commission of the International Astronomical Union.   At PSU she founded a 6-week summer research program for high school students.