Satellites Overhead

13:50 Fri, 30 Sep 2011

Wolfram Alpha has a cool web page that shows satellites overhead, where overhead is defined as visible, i.e. above the local horizon.

I was very surprised to find I have 1,685 satellites overhead right now. If I had to guess, I suppose I would have said 3 or 4, not 1,685!

On the other hand, Wolfram Alpha define a satellite as anything, including junk. Even so, when we restrict it to non-debris satellites it is still a big number, 670 to be exact.

You can click on each satellite and get the orbital elements, range, azimuth and a bunch of other stuff including a map showing the orbits.

It is pretty cool and worth a visit to play around.

Categories: science, astronomy

Moving House

11:12 Fri, 30 Sep 2011

I will be moving over the next two weeks. I'll go offline while the ADSL connection gets moved, so there will not be much if anything here for a couple of weeks.

Categories: moving

Fringing Reef

08:15 Sun, 25 Sep 2011

Being raised in Western Australia, I guess I was spoiled when it came to snorkelling or diving. Perth has many reefs nearby, some of them accessible from shore and some of them around local islands including Garden Island and Rottnest Island about 12 km off the coast.

I never thought too much about it, they were just there.

The local Perth reefs are limestone, not coral. It turns out that coral reefs near the shore are very rare. Coral is sensitive to fresh water and as a result most reefs are either some distance off shore where they are not affected by freshwater run-off that you get from river outlets or are isolated atolls such as in the Pacific.

Fringing reefs are much rarer because they can only exist where there is no run-off. W.A. is lucky in having a couple of places like that, the most famous of which is Ningaloo Reef, the world's biggest. Another one was discovered in the Kimberley a couple of years ago.


Categories: science, general

Decoding a Spammer's Attempt to Obfuscate His IP Address

18:47 Sun, 18 Sep 2011

IP v4 addresses are familiar as dotted quads. A spammer uses an interesting feature of IP addressing to obfuscate his address. A look at the various ways of specifying an IPv4 address.

I received a spam email yesterday that was phishing for some banking details. It contained the usual "your account has been disabled, you need to reactivate it" spiel, along with a link to click. When I hovered the cursor over the link, it displayed the bank's URL. Or did it?

URL address shown on

URL displayed when hovering over the link

A cursory glance shows the link's URL pointing to There is some other stuff before the, but I wonder if many people would query it, especially since it appears to contain the quite-common www1 prefix.

If we look closely, however, we can see that the actual domain part of the URL is 95.11064393, which is followed by a directory of There is a "/" almost hidden between the two parts. It is quite easy to overlook, which is

Categories: internet, unix, general

Prey: Replace Streamer with Mplayer

10:35 Sun, 11 Sep 2011

Prey is a recovery application for stolen mobile devices that, among other things, takes a photo through the webcam. It uses streamer, which can be problematic. Replace streamer with mplayer.

Prey is an application that can help you track your mobile device if it is stolen. It is pretty neat and I have it installed on my laptop.

It does its job by checking in with a central server every so often. If your device is stolen, you mark it on the server (using another computer) and then prey, upon checking in and realising the device is marked as missing, will run its recovery routine. It gathers information about the device's IP address, GPS location if available, MAC address and so on, takes a snapshot of the screen, and takes a photo through the device's camera. It bundles that up and sends it to the central server, or you can tell it to send to you in an email.

Armed with that information, you can set about recovering your device.

Prey is available for all the major platforms: Windows, Mac and Linux. It uses common unix utilities (compiled especially in the case of Windows). For Linux it

Categories: internet, unix, general

Moving Image of New York Skyline on 9/11

11:28 Fri, 09 Sep 2011

This image of the New York skyline from Brooklyn almost on the eve of 9/11 is particularly apposite.

New York Skyline

The way the light beams hit the clouds and burst into a shining globe is quite beautiful and poignant.

Categories: general

Blog Content for Mobile Users

10:28 Thu, 08 Sep 2011

Quick, easy and simple way to convert blog content to a mobile-friendly format using sed.

When I set up this blog three years ago I did not bother to design anything different for mobile users, mainly because I had the notion of mobile as meaning laptop users. It was a safe bet to assume that the screen would be at least 800 pixels wide, or more commonly at least 1280 pixels wide. Phone users of web content were still very much in the minority.

In the three years since, the landscape has changed enormously. Now, there are plenty of users of mobile devices and they are using netbooks, tablets and mobile phones. It was time to cater to those users with small screens by providing special content.

I was not looking forward to this. My CSS skills are average at best and the thought of trudging through the CSS and HTML to set up special handling was daunting.

Then I googled how other people handled it and read a neat idea: use sed or awk to filter the normal output. I would not have to rewrite the application or the CSS. Great!

Categories: blogging

Top Two Must-Have Utilities for Windows

09:00 Mon, 05 Sep 2011

There are only two must-have tools for Windows that are on my machines. If you are running an OS later than XP (Vista or 7), then there is only one.

Windows is let down by a poor file management tool. It tries to push file management into a quasi browser, Explorer, and the result is a bad compromise.

The first thing I do on any Windows machine is install xplorer² from Zabkat, a small software company run by a chap called Nikos. There is a free lite version and a subscription-based fully featured version. If you are a command line guru from the unix world, spring for the full featured version: the list of features is huge, you can read them here. If you don't need all those features, the free lite version will still provide much better file management and exploring abilities than the default Windows Explorer; two-pane browsing alone is worth it.

I've been using xplorer² for about a decade and bought a licence several years ago. It is the best file management utility I've found. It is even better than the various unix ones and I wish there was a port of it for Linux.


Categories: general, microsoft

DNA Testing Means More Elderly Prisoners

09:02 Sun, 04 Sep 2011

New technology and science in crime fighting means that old crimes from 20 or 30 years ago are now being solved, mainly from DNA evidence.

One of the perhaps unexpected outcomes is that there are more elderly prisoners than before, to the point that prisons are having problems coping with them.

An example of the change is in Victoria's prison system where the number of prisoners over 50 has doubled in the last ten years, and there are more new prisoners in their 70s and 80s, which used to be a rare event.

Australia Bureau of Statistics figures show that over the last ten years the number of Australians over 50 has grown by 31%, whereas in prison it has grown by 84%.

The implications are wide: some of elderly prisoners can't use the top bunk, can't wash themselves and can't get around to do exercise without a frame. It also means that prison hospitals are increasingly being used as aged-care facilities.

We might end up like the U.S. and have special nursing home prisons. More in The Age.

Categories: general, politics, law

Spectacular Coronal Ejection

11:18 Fri, 02 Sep 2011

Check out this image of a big coronal mass ejection a few days ago.

lasco c2 coronagraph small image

Click for full size


The white circle represents the Sun, hidden by the coronagraph's occulting disk. Eye-balling the image using my Mk-1 thumb, the ejection was 2 or 3 times the Sun's diameter.

The instrument is part of the SOHO project, the Solar and Heliographic Observatory, and the actual instrument is the Large Angle and Spectrometric Coronagraph Experiment (LASCO).


Categories: astronomy, science