I have finally found some time to use my Raspberry Pi as timelapse camera to capture some startrails. I found this useful page showing all the details needed to set the Pi camera to a maximum of 6s exposure. I got the best results by setting the shared video memory to the maximum setting of 256Mb. Otherwise the image numbers would have gaps.


Startrails taken with a Raspberry Pi

Now, I just need to repeat this next time there is good weather and new moon. Preferably I’m going to do this in a slightly darker spot with less light pollution.

I pointed /etc/rc.local to this srcipt (adapted from the above mentioned website)

sleep 120
cd /home/pi/starttrails raspistill -bm -tl 0 -v -set -ISO 800 -awb off -awbg 1,1 -t 14400000 -ss 6000000 -o %06d.jpg
shutdown -hP now

The pictures were assembled with the following lines:

# trail.jpg is a copy of the first immage 000000.jpg
for f in 0*.jpg
echo $f
convert trail.jpg $f -gravity center -compose lighten -composite -format jpg trail.jpg

I have also turned the stills into a short timelapse video:

ffmpeg -start_number 0000 -i 00%d.JPG -c:v libx264 -pix_fmt yuv420p video

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Energy consumption

I finally got round to writing up the analysis of the energy consumption of our home. Using almost 2 years worth of consumption and temperature readings I work out the leakage of our house and look at the seasonality of our electricity consumption.

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Maps for Garmin eTrex 30

This is more a memo to self than a blog post. For an up to date map for the Garmin eTrex 30 go to Garmin Openstreetmap and download the required map. Then copy the file on to the SD card into a top level folder called Garmin, my Great Britain map has the filename gmapsupp_GB.img for instance. And that’s it, the map can now be enabled from the appropriate map menu. Routing works, but takes interesting turns for longer distances.
2016-03-28 08.29.09

Similarly, tracks go into the Garmin/gpx. The can be selected as routes from the menu. The file Barry_s_Bristol_Ball_Buster.gpx gets displayed as Barry's Bristol Ball Bust for selection.


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Pancakes and Sunrise

Last weekend we had potato pancakes to use up our surplus potatoes from Christmas. They were particularly yummy with German bacon and apple sauce from the our own garden.

From 2016

It is a simple recipe to make potato pancakes:

  • 1kg of grated potatoes
  • 3 eggs
  • 3 table spoons of plain flour

Simply fry the mixture until golden brown and it’s done. They taste nice with apple sauce or any other sweet thing, like honey, jam or chocolate spread.
The cold weather earlier this weekend produced a stunning sunrise on Wednesday morning. Below is a picture I took from the Thames path in Reading.

From 2016
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Running Linux on a MacBook

For a while I had been contemplating replacing my 2008 Macbook (4,1) as it was stuck on OSX 10.6. But I couldn’t find any new affordable laptop that took my fancy (too expensive, too big, too small, just not right). I remembered reading about running Linux on MacBooks a while ago and thought, why don’t I try Linux?

I downloaded the 17.1 Linux Mint iso (cinnamon flavour) and followed the instructions to make a bootable USB stick.

I took out the internal hard disk and replaced it with an old one I had kicking about. After that,  I plugged in the USB stick rebooted the MacBook holding down the ALT key and the machine booted into Linux after choosing the correct device (in the second attempt). I followed instructions that I largely ignored as they were not applicable. To get the WIFI working this line

apt-get install firmware-b43-installer

sufficed. And another irritation is that the touchpad doesn’t quite work but the interwebs have solutions for that as well. Though the relevant config file appears to live in


You can experiment with the settings using synclient.

I also added




And it’s a good idea to switch off hardware acceleration in Chrome as the screen goes black when watching youtube videos otherwise.

After a weekend of testing, I splashed out on a 1Tb SSD and put that in the MacBook and now have a fairly zippy 4Gb MacBook running a modern OS. Even Google’s tensorflow installed without a hitch.


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User names in failed login attempts

Between 6 December and 22 November 2015 there were 2068 failed attempts to login into my machine exposed on the interwebs. I excluded the the ones due to me being unable to type my super-safe password correctly. This equates to about 6 attempts per hour on a machine that is not widely advertised. Presumably, this is mainly due to random attacks that you can also investigate with network telescope, in fact my machine is a network telescope of sorts. So looking at the frequency of usernames used in failed attempts (or attempted break ins if you like) root is the most popular choice and the top 20 are:

User Name Count
root 1272
admin 207
ubnt 106
user 69
pi 64
support 30
adm 25
test 22
zhangyan 20
dff 18
guest 15
reception 15
a 9
oracle 9
from 7
aaron 6
ftp 6
cisco 5
ftpuser 5

Plotting the rank of a user name against its frequency logarithmically we get the all too familiar picture of a heavy tailed distribution or power law:


However, here the x-axis barely covers 2 decades, so one should be a bit careful to declare that we see a power law with a gradient of about -1.5. Another way to visualise the data is to look at the usernames used in chronological order  (excluding repeats)  as  nodes in a network. Even this very small sample produces a surprisingly complicated graph.


This is a graph produced by the twopi program of graphviz which looked like the prettiest one. The most connected nodes are root and admin. Is this useful? One interesting way approach this question would be to compare this graph and the analysis above with a data set that contains only valid and successful logins. If the data looks suitably diffrent one could use this approach to get alerted to unwanted behaviour. Unfortunately, I do not have access to such a data set.

I was also intrigued to see the user name pi to feature quite high in the charts, ten years ago this would have been less popular.



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Sunrises and winter fayres

The last few weeks have been very wet and not very  pleasant for cycling to work. But as reward there have been some spectacular sunrises.

From 2015

And in central Reading the “Winter Wonderland” has been assembled in Forbury Gardens.

From 2015
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