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Hi Stuart,
Hey, it was really great to see you in June which already seems like ancient history! I hope all is well with you, Donna and Bob.
I had a question regarding counteracting radial distance star thinning in Hipparcos which I know you have been able to achieve in your production work. If I remember correctly, you made selective cloning of Hipparcos to do that along your flight path for the local tour and pull out from Milky Way in the traverse you all did for Tom Lucas's "Runaway Universe" (...and may be for "Black Holes" as well??). We need to counteract star thinning in our current production (entitled "The Stars") by some means, so I wanted to ask you if you might be willing to collaborate / advise us on such. If you thought that was at all feasible, I would then want to involve our producer, Sarah Dowland to get in contact with Donna, of course to work out whatever might be necessary. Since our star rendering already reads the Hipparcos speck files, I also though asking you what you did might work off that same format. I
I just wrote to Ka Chun also as I know he had shown me a nice real-time procedural star generator he coded some time ago. Brian still has our very old C-Galaxy procedurally produced star data cubes of varying dimensions according to abs. mag., but that whole solution had certain complexity and never really worked as we had hoped.
Also, regarding the below mail from you of over a year ago (my apologies for not responding then), I wanted to tell you that we are working on an extension of the app. mag. scale beyond the exponentials for our current production. We are adding in an effect of optical diffraction radial ray noise for objects brighter than Sirius. We are working with Sabastian Lepine on this, one of our astrophysicists. Since we have to get close to stars, we felt we needed this. Once we get up close to an actual model of stars we want to examine, we will then cross dissolve from the glare to the simulation.
Thanks,
Carter
On Aug 31, 2007, at 10:40 AM, Stuart Levy wrote:
On Fri, Aug 31, 2007 at 03:35:45AM -0000, w_bridgman wrote:
> I found the duplications and regenerated the page. It fixed some other
> oddities around the image as well. Betelgeuse looks much nicer now. ;^)
>
> http://svs.gsfc.nasa.gov/ vis/a000000/ a003400/a003442/ index.html
Say, have you tried other star profiles (PSFs) besides Gaussians?
We've been using exponentials, as in exp(-abs(r)/r0) rather than
exp(-r^2/r0^2), as I first heard from I think Carter Emmart of AMNH,
and as Andy Hanson of IU noted from a paper of Peter King
("The Profile of a Star Image", PASP, v. 83, April 1971, pp. 199-201).
It has the visual advantage that, where stars are bright enough to
cover a lot of screen space, they still have bright sharp cores.
Dr. Carter Emmart
Director of Astrovisualization
Rose Center for Earth and Space
American Museum of Natural History
79th Street at Central Park West
New York, N.Y. 10024
Office: +1 (212) 496 3570
Mobile: +1 (917) 567 7033
Digital Universe: http://haydenplanetarium.org/universe/
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