Making a tachometer for a grinding / polishing machine for telescope mirrors

When making a telescope mirror on the machine, two parameters are important: the rotation speed of the mirror, and the rotation speed of the overarm eccentric. Other environmental parameters also matter: temperature and humidity are foremost here. To more easily monitor and display these variables, I've built an electronic device that collects this data and shows it on the control panel. This is how to build the device.


multifactor authentication for distributed VPN mesh - part 1, server and client configuration, cloud OTP

Building a distributed VPN mesh (multiple VPN servers, authenticating same accounts, having same routing)? Want to give a security boost to authentication? Thinking about multifactor? Here's one of the many architectures that work.


Monitoring for the cloud, part 2 - architecture

There's a cornucopia of tools for monitoring cloud infrastructure: Sensu, Graphite, Logstash, Riemann, etc. The very, very good news is that most of these tools speak each other's protocols. This opens up a lot of possibilities: from small setups where some components (e.g. the message queue) are reused, serving many purposes at once, to complex architectures where the various functions are decoupled, there are large amounts of redundancy at various levels, etc.


How to see Sirius B

Note - this blog post got noticed and was reprinted by EarthSky:

Sirius is the brightest star in the night sky, visible anywhere on Earth except the far North. If you live in the northern hemisphere at a temperate latitude, Sirius is that very bright white star due south every winter in the evening. But did you know that Sirius is also a double star? The companion, Sirius B, also known as The Pup, is a very small star orbiting the primary, and can be seen using amateur telescopes, even small ones. It's not an easy observation to make, but it can be done if you follow certain guidelines. Here's how to do it.


I had no idea just how big the Solar System really is

So, we did a "science project" today, the kids and me. We made a scale model of the Solar System, out on the street, to get a visual impression of its true size. It was pretty amazing. It's a very easy project to do, takes a couple hours, and it's a lot of fun.

The Sun was a regular soccer ball, 23 cm (9") in diameter. Everything else was made to scale.

Mercury was a tiny 0.8 mm grain of sand, barely visible, about 10 m (30') away from the Sun.

Venus was a larger 2 mm grain of sand, 18 m (54') away from the Sun.


On public roads, profiling other drivers can be a good thing

A few years ago I bought a motorcycle, and quickly discovered the necessity of trying to predict other people's behavior on the road - profiling, basically, not for the sake of it, but in the interest of my own safety. On a bike, the main source of trouble is not yourself, it's other people. Also, on a bike, trouble is either absent, or very very big. So I started to collect these observations - and continued to do so even later when driving my very boring and average four-wheel sedan.

These are not inflexible rules, but merely "statistical truths". I do think the observations are sound, so I use them all the time as guidelines. Here's the list:

How to build a small laser that can burn things

It used to be that lasers were big bulky expensive things that required a laboratory to run and an entire factory to build. I remember the first He-Ne laser I saw two decades ago, the size of a small telescope and probably not more powerful than the laser pointer I carry on the keychain nowadays. Well, not anymore. It's pretty easy to build a laser today, on the kitchen table or in the garage, for a surprisingly small investment. The goal is to make a laser capable of burning small objects, such as a piece of paper, a balloon, etc, while keeping the whole project cheap - even as cheap as $35 if you don't make any mistakes. Here's how.


Bye-bye cable news

Finally got rid of cable TV today (actually Mihaela did, it was her initiative). Renting movies on Netflix is quite enough, even more so if you consider that you can do video streaming from Netflix directly to the PS3. What with their tens of thousands of titles, I'll never run out of movies to watch. Kids get their cartoons too from the same source. Plenty of fish in that pond.

"Zeitgeist", the movie, debunked (part 1)

I had no intention to write about "Zeitgeist" at all. I've skimmed it shortly after its release, seeing as it had generated a pretty consistent buzz on the blogosphere and the discussion forums. I've seen references popping up here and there afterwards, but mostly I just ignored them. So I thought the whole affair was dead and buried and I was well on my way to forget it. Except, I was not aware of the impact and influence that the movie still had in the time that followed - and still has today. That was my biggest surprise, and the reason why I'm writing now.

OK, I'm lying. I'm also writing about it because I need the exercise - you know, to keep that pen sharp, or rather that word processor busy. But regardless of the reason, here it is, my review. Sort of.

Review: "His Dark Materials" trilogy - "The Golden Compass", "The Subtle Knife", "The Amber Spyglass" by Philip Pullman

An epic fantasy trilogy, the first part already a movie ready to launch on December 7th:

The interesting part is the amount of noise the movie has generated in the media, despite the fact that the three books were not as controversial, not even close. But why the controversy?

Game review: "Bioshock", by 2K Games

Bioshock is a first-person shooter game, released in 2007.

The plot follows plane crash survivor Jack, as he enters and explores the underwater city of Rapture, the goal being survival and finding a way out of the city. The game looks and feels like a morality-based Doom, of sorts, but the story has surprising and fascinating connections which are not obvious at first sight.

The quest for intensity

This is part 3 in the motorcycle series, and a follow-up to my essay "The decision tree" which can be found here:

You're riding the sportbike on a technical road or track, quickly following the riders ahead of you, braking to shed speed, leaning through the turns, straightening up the bike, revving the engine until it's screaming with rage and joy, and you're propelled forward by the awesome acceleration of the racing bike, and you do it over and over again, until every fiber in your body is vibrating with the thrill of the extreme speed and the world disappears in a fast receding blur.


Movie review - "300" by Zack Snyder, based on Frank Miller's graphic novel

This is not the usual run-of-the-mill historically accurate movie. Those who expected that were surely disappointed. Instead, the movie chooses to stay faithful to the graphic novel by Frank Miller. So, it's a mix of stories of bravery and honor, of Miller's intense imagery, and of post-Matrix cinematography. The results are very interesting indeed.

Keep reading to find out why.

The engines of joy

On January 9th 2006, while riding my motorcycle to work, I had an accident. I thought the car ahead of me in the left-hand lane was going to swerve into my lane. That was not true, but I acted upon this false impression and I hit the front brake hard. The front wheel froze, the tire lost traction, the bike fell on the left side. I hit the road and tumbled a dozen times or more. The bike was a total loss. I was rushed to the hospital - the result: broken right ankle, broken left collarbone. I underwent surgery to fix my ankle, which put a metal piece in my foot and several screws to keep together the shattered bones. I had to do many months of physical therapy to recover the ankle, which may or may not be ever the same - it's too early to tell now, about 9 months later, although I made huge progress and the prospects look good. My own god damn fault, this whole affair, but that's not the topic of these pages.

And yet, one of the things I often - nay, I permanently dream about is to get back in the saddle. Keep reading to find out why.


Movie review: "Fearless", with Jet Li

"After a great war, foreign powers ruled China. But our traditions still gave us hope. To break our will, they staged the tournament to prove the superiority of their warriors against our own. Only one rose to challenge them. He carried our pride on his shoulders and brought the nation to its feet."

"This man was fearless."

Only human

I just watched "Borderland", an episode in the 4th season of the Star Trek Enterprise series. As the new Star Trek goes, it's pretty good. We get to see Brent Spiner again, there's lots of action, the plot - albeit not too original - is pretty well guided and has good rhythm... And yes, it's the "beyond humanity" theme again. And it's the same old comfortable yet cowardly answer to it again. Let me explain.


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