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  • Allen Versfeld
    October 18, 2012
Welcome to The Urban Astronomer, where we understand what it's like to be trapped in the city and denied the full glory of a properly dark night sky. Here you will find articles on how to set up an observing site to minimise the effects of light pollution, and guides on how to get the most enjoyment from naked eye, or small instrument viewing. There are more detailed articles explaining the science behind common astronomical concepts (from Eclipses to Black Holes). There's a question and answer section (now with a Short Questions sub-section, for the researcher in a hurry), where I answer reader's emailed questions with full length articles, and a News and Updates section, where I'll post short news items, and announcements of updates to the site. There's even a 2012 section, where I attempt to cut through the fog of doomsday misinformation around the year 2012.

If you enjoy what you read, please feel free to link to it in your blogs and emails, or share it on your favourite social network! Note that, where uncredited, all images are gathered from http://commons.wikimedia.org/ and have been made free for public use by the original authors.


News and Updates

  • Public Lecture: A Rosetta Stone for Gauge/Gravity Duality Thanks to Clair Flanagan from Wits University for letting me know about this:Prof Robert de Mello Koch will be delivering his inaugural lecture at Wits University (Senate House) tonight ...
    Posted by Allen Versfeld
  • Cassini Probe to photograph Earth The famous Pale Blue Dot image of Earth, part of a larger mosaic of almost the entire Solar System, returned from the Voyager 1 interstellar probe in 1990. On 19 ...
    Posted by Allen Versfeld
  • Carnival of Space #306 Well it's been a long time coming, but Urban Astronomer is finally hosting a Carnival of Space.  This will be the 306th Carnival and for anybody who's gotten ...
    Posted Jun 17, 2013, 8:26 AM by Allen Versfeld
Showing posts 1 - 3 of 711. View more »

ATM diary

  • Let's try this again 29 months after I first put grit to glass, I've put my mirror on the test stand for the first time.  It's not as good as I'd hoped.To recap: I last touched this project 10 months ago.  Since then, the mirror and the polishing lap have been sealed into plastic containers, and left to rot in the loft while life overwhelmed me.  But today, I got in my car and hauled everything down to Joburg and the ATM class.  When I unpacked everything, I found the mirror caked with dry cerium, and the pitch lap had slumped down into a very flat mushroom shape, and gone rock hard (Also, some mildew had taken root in the ...
    Posted May 25, 2013, 1:23 PM by Allen Versfeld
  • ATM in the media I figured out why I'm taking longer and longer gaps between work: My kids are getting old enough to climb into cupboards, and curious enough to dig through and dismantle everything they find.  Therefore, if my mirror and supplies are to survive, they have to be packed and hidden away very thoroughly in hard-to-reach places.  I'll do a few hour's polishing, stash it all together in the highest darkest recess of a cupboard, and then forget about it.  It's the old "Out of sight, out of mind" principle at play.  Perhaps our new home will have a room we can use as a studio or workshop, where our stuff can be left out and ...
    Posted Sep 14, 2012, 3:21 AM by Allen Versfeld
  • The prodigal lap To recap the past few work sessions:  I tried to re-open the channels on my lap by warming the pitch and pressing a steel ruler into the existing channels.  This caused the edges of the facets to mushroom up, so I tried a warm press to fix things.  This was overdone (too hot, too much pressure, left for too long) so that I ended up with a perfectly smooth featureless lap.  I then tried fixing it by cutting channels in with a craft knife, but my knife-fu was weak and I ended up chipping great divots out of the surface.  So I tried the warm press - steel ruler combination again, this time paying more careful attention to the ...
    Posted Jul 30, 2012, 5:01 AM by Allen Versfeld
Showing posts 1 - 3 of 43. View more »