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ASTRO: 2001 SN263 Triple Amor Asteroid passing by
On Tuesday Arecibo's radio telescope discovered this asteroid, which is
making a close pass by earth, is really triple. Obviously that can't be seen visually but it isn't often that a tiny near earth asteroid is bright enough and well positioned for most all the inhabited parts of the earth as this one is. It is in Gemini headed for Hydra's head over the next 11 days or so. It is moving about 8" of arc per minute. This will stay pretty constant over the next couple of weeks. It was 6.5 million miles away when I imaged it at magnitude 12.5. In a week it will be magnitude 12 and about 6 million miles away, its closest for this encounter. http://www.skyandtelescope.com/news/15637782.html You can construct an ephemeris for your viewing times at: http://cfa-www.harvard.edu/iau/MPEph/MPEph.html The orbital elements for computer scopes is available there as well. i found it dead on accurate. Being in the Milky Way of Gemini I figured it hard to find, I'd have to expose several minutes and look for the trail but there was this nice 12 mag star dead center and yep, that was it. Nice when things work like they are supposed to. I used 15 exposures of 30 seconds with a wait of 60 seconds between each to generate a dotted trail. Star field is 30 such exposures. They were combined with Sigma Reject so the asteroid was rejected leaving only the non moving objects. That was processed for the stars. I then combined 15 of these using averaging. It was processed for the asteroid while the stars and galaxies looked awful because of this and were much fainter. I then used two layers in photoshop combining using the lighten mode. This has the effect of grabbing the asteroid from one and the star field from the other and combining them effortlessly on my part. A neat trick the photoshop expert I know taught me. Due to clouds there was a 20 minute period I couldn't image so rather than put a large break in the trail I just used the last 15 for the asteroid. The moon was in Taurus and the asteroid in Gemini so I had horrid gradients with part of the corrector plate moonlit. I'm still rather poor with such strong gradients. Left side in direct moonlight had a background count of 21000 while the right side had one of 540. That's a gradient! It started snowing only an hour after I took this. So never had a chance for color data. Scale is 1.5" of arc per pixel. 14" LX200R @ f/10, 15x30 asteroid, 30x30 background all binned 3x3, STL-11000XM, Paramount ME Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
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