2011-08-01
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APOD: 2011 July 30 - A Tale of Two Hemispheres:
In projection, the mosaic view sandwiches the horizons visible in all-sky images taken from the northern hemisphere’s Canary Island of La Palma (top) and the south’s high Atacama Desert between the two hemispheres of the Milky Way Galaxy. The photographers’ choice of locations offered locally dark skies enjoyed by La Palma’s Roque de los Muchachos Observatory and Paranal Observatory in Chile. But it also allowed the directions to the Milky Way’s north and south galactic poles to be placed near the local zenith. That constrained the faint, diffuse glow of the plane of the Milky Way to the mountainous horizons. As a result, an even fainter S-shaped band of light, sunlight scattered by dust along the solar system’s ecliptic plane, can be completely traced through both northern and southern hemisphere night skies.
2010-11-14
Above London: a retirement notice
Over three years ago, at the Yahoo/BBC Hackday in Alexandra Palace, candace and I knocked up Above London and Above SF, two Twitter bots that would alert followers in one of those two cities that the International Space Station (or an Iridium flare) would be visible.
I’m happy with the reception it got, and I still prefer its output to that of some of the subsequent services that provide the same service (such as @overlondon or @twisst). However, it was always a bit of a pain to look after (true to the word “hack” in the event title, I cut corners when it came to handling DST, and occasionally the cron jobs running it would fall over).
Two things have finally done for it: Twitter’s move to OAuth, and more importantly, the fact I managed to leave the only copy of the code on a server that’s now sitting, unplugged, in the UK. Even the service on which I posted the write-up of the hack has now closed. Given that, it’s probably best that I post a message to the Twitter accounts, and formally shut up shop (for now, at least).
Thanks to everyone who followed either the San Francisco or London account, and good luck with one of the aforementioned alternatives. I hope you got to see the ISS at least once. It’s always warmed my heart to look up and see the few humans that circle the world, shining brightly in the evening twilight.
2010-10-19
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The Map Room: Darker Than You Think
the original Light Pollution Atlas was systematically biased by the fact that snow was on the ground when the underlying satellite measurements were taken. Lorenz recalculated the light pollution for the U.S. and southern Canada based on snow-free satellite observations, and the whole northern part of the area came out roughly one full zone darker. That means that the original atlas overestimate the skyglow in this area by a factor of three.
Even so, the Bay Area sticks out as a red spot. At least there are some good dark skies within a (relatively) easy drive. (via aemkai’s ffffound)
2010-09-08
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Asteroid Discovery From 1980 - 2010 by Scott Manley.
This is a view of the solar system showing the locations of all the asteroids starting in 1980, as asteroids are discovered they are added to the map and highlighted white so you can pick out the new ones.
Notice now the pattern of discovery follows the Earth around its orbit, most discoveries are made in the region directly opposite the Sun.
I’m mildly curious as to why there’s a slight offset from being exactly at opposition. Perhaps it’s to do with the best time for observing (I can’t be sure I’ve worked out if the direction corresponds to evening or early morning), or that you have to get two (or more) fixes to establish an orbit.
2009-09-01
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“Venus, Jupiter and the moon rise at sunset over the Nepean river, New South Wales, Australia.”
by Vincent Miu, as seen in the Guardian’s Astronomy Photographer of the Year gallery.
2009-08-10
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The sun setting behind some radio masts in Puglia, by Giuliano Froio, seen on the Telegraph’s gallery of the shortlisted photographs for the Astronomy Photographer of the Year.
2009-05-26
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“Due to its isolated location high in the arid Chilean Andes, CTIO provides breathtaking views of the southern night sky and pristine observing conditions for astronomers. Photograph courtesy of Guillermo Damke” from The Long Shot in Seed Magazine.
2009-05-21
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The kit used to take the the Milky Way timelapse video that’s proved so popular online this week.
Ironically, perhaps, all those fancy tracking tripods and telescopes aren’t what was used; it was a wide angle, not telephoto, lens, and the tripod wasn’t tracking the earth’s rotation either. The page about the video on William Castleman’s site notes the wide angle lens and has more details of how it was taken:
Canon EOS-5D (modified) ISO 1600 and EF 15mm f/2.8 @ f/2.8 Fisheye on tripod; 20 second exposure followed by 35 second interval; one exposure each minute
The modification noted is the change of the final filter in front of the sensor. Usually, it cuts out all IR light and a lot of red with it, but for astrophotography, it’s better to capture that instead (or at least, to cut a ‘hole’ for the hydrogen alpha line at 656nm). This is what brings out the nebulosity in the video.
2009-02-09
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via homepage.mac.com: ”in one small space, it shows the time of Sunrise and Sunset across the entire world throughout all Latitudes throughout the entire year of this tilted planet”
