Thanks Dad. Thinking of you.
If you’re around Melbourne, interested in astronomy and fancy visiting a community powered astronomical observatory that has a very active outreach and amateur astronomy focus then can I interest you in the Mount Burnett Observatory open day this Saturday (January 23rd) from noon onwards?
We’re going to have all sorts of things going on – talks, telescopes, radio astronomy, tours of the observatory dome (originally built by Monash University), lots of enthusiastic volunteers!
We’re fundraising to build a new accessible modern dome to complement the existing facilities so please come and help us out.
For those who’ve not been paying attention the Let’s Encrypt project entered public beta recently so that anyone could get their own SSL certificates. So I jumped right in with the simp_le client (as the standard client tries to configure Apache for you, and I didn’t want that as my config is pretty custom) and used this tutorial as inspiration.
My server is running Debian Squeeze LTS (for long painful reasons that I won’t go into here now) but the client installation was painless, I just patched out a warning about Python 2.6 no longer being supported in
It worked well until I got rate limited for creating more than 10 certificates in a day (yeah, I host a number of domains).
Very happy with the outcome, A+ would buy again.. 🙂
I was playing around with some code and after having got it working I thought I’d make just one more little quick easy change to finish it off and found that I was descending a spiral of additional complexity due to the environment in which it had to work. As this was going to be “easy” I’d been pushing the commits to master on Github (I’m the only one using this code) and of course a few reworks in I’d realised that this was never going to work out well and needed to be abandoned.
So, how to fix this? The ideal situation would be to just disappear all the commits after the last good one, but that’s not really an option, so what I wanted was to create a branch from the last good point and then swap master and that branch over. Googling pointed me to some possibilities, including this “deprecated feedback” item from “githubtraining” which was a useful guide so I thought I should blog what worked for me in case it helps others.
git checkout -b good $LAST_GOOD_COMMIT # This creates a new branch from the last good commit
git branch -m master development # This renames the "master" branch to "development"
git branch -m good master # This renames the "good" branch to "master".
git push origin development # This pushes the "development" branch to Github
- In the Github web interface I went to my repos “Settings” on the right hand side (just above the “clone URL” part) and changed the default branch to “
git push origin :master # This deletes the "master" branch on Github
git push --all # This pushes our new master branch (and everything else) to Github
- In the Github web interface I went and changed my default branch back to “
…and that was it, not too bad!
You probably don’t want to do this if anyone else is using this repo though. 😉
If you’ve been paying attention to the world of planetary exploration you’ll have noticed the excitement about the unexpected white spots on the dwarf planet Ceres. Here’s an image from May 29th that shows them well.
Having looked at a few images my theory is that impacts are exposing some much higher albedo material, which you can see here at the top of the rebound peak at the center of the crater, and that the impact has thrown some of this material up and that material has fallen back as Ceres has rotated slowly beneath it giving rise to the blobs to the side of the crater.
If my theory is right then if you know Ceres gravity and its rotational speed and the distance between the rebound peak and the other spots then you should be able to work out how far up the material was thrown up. That might tell you something about the size of the impact (depending on how much you know about the structure of Ceres itself).
As an analogy, here’s an impact on Mars captured by the HiRise camera on MRO that shows an area of ice exposed by an impact.
— HiRISE (@HiRISE) June 6, 2015
At work we’ve started using some UniFi wireless gear and the system I’ve managed to commandeer to do the control system for it is running Kubuntu 15.04 which uses systemd. Now the UniFi Debian packages don’t supply systemd unit files so I went hunting and found a blog post by Derek Horn about getting it running on CentOS7 so I nabbed his and adapted it for Ubuntu (which wasn’t that hard).
The file lives in
/etc/systemd/system/unifi.service and was enabled with
systemctl enable unifi.service (from memory, there might have been another step that involved getting systemd to rescan unit files to pick up the new one, but I don’t remember for sure).
Here is the unit file:
# # Systemd unit file for unifi-rapid # [Unit] Description=UniFi Wireless AP Control System After=rsyslog.target network.target [Service] Type=simple User=root #ExecStart=/usr/bin/java -Xmx1024M -jar /usr/lib/unifi/lib/ace.jar start ExecStart=/usr/bin/jsvc -nodetach -home /usr/lib/jvm/java-7-openjdk-amd64 -cp /usr/share/java/commons-daemon.jar:/usr/lib/unifi/lib/ace.jar -pidfile /var/run/unifi/unifi.pid -procname unifi -outfile SYSLOG -errfile SYSLOG -Djava.awt.headless=true -Dfile.encoding=UTF-8 -Xmx1024M com.ubnt.ace.Launcher start #ExecStop=/usr/bin/java -jar /usr/lib/unifi/lib/ace.jar stop ExecStop=/usr/bin/jsvc -home /usr/lib/jvm/java-7-openjdk-amd64 -cp /usr/share/java/commons-daemon.jar:/usr/lib/unifi/lib/ace.jar -pidfile /var/run/unifi/unifi.pid -procname unifi -outfile SYSLOG -errfile SYSLOG -Djava.awt.headless=true -Dfile.encoding=UTF-8 -Xmx1024M -stop com.ubnt.ace.Launcher stop SuccessStartStatus=0 SuccessExitStatus=255 [Install] WantedBy=multi-user.target
Those around Victoria will be familiar with our public transport payment system called “Myki” which has had, shall we say, some teething troubles. It appears this was well known to the Vikings over 1,000 years ago as this list of Old Norse words that made it into English has:
muck – myki (cow dung)
So there you go, Myki is actually Old Norse for bullshit. 🙂
As some of you know I’m involved with the Mount Burnett Observatory, a community run astronomical observatory in the Dandenong Ranges of Victoria near Emerald to the south-east of Melbourne. Originally built by Monash University in the early 1970’s it’s 3 years since a small group of people formed a community association, took over the site and starting resurrecting it as an observatory by and for the people. It’s now three years on and by the end of last year we were the second largest astronomical association in Victoria!
This Saturday (24th January) is our third birthday celebration so we’re having an open day running from 1pm through to 6pm with tours, activities, a solar telescope and components from the Murchison Widefield Array (MWA), one of the precursor telescopes to the massive Square Kilometer Array telescope project!
At 6pm we have a barbecue and then at 7pm there will be a talk by Perry Vlahos on what there will be to see in the sky over the coming month. After that we’ll be socialising and, if the weather behaves itself, viewing the stars through the many observatory telescopes.
Looks like things are moving along in the world of 64-bit ARM, systems aimed at early adopting developers are now around. For instance APM have their X-C1 Development Kit Plus which has 8 x 2.4GHz ARMv8 cores, 16GB RAM, 500GB HDD, 1x10gigE, 3x1gigE for ~US$2,500 (or a steep discount if you qualify as a developer). Oh, and it ships with Linux by default of course.
Found via a blog post by Steve McIntyre about bringing up Debian Jessie on ARMv8 (it’ll be a release architecture for it) which has the interesting titbit that (before ARM had their Juno developer boxes):
Then Chen Baozi and the folks running the Tianhe-2 supercomputer project in Guangzhou, China contacted us to offer access to some arm64 hardware
So it looks like (I presume) NUDT are paying it some attention & building/acquiring their own ARMv8 systems.