Transit of Venus light curve: exoplanet detection demo

Ok, so Venus isn’t an extrasolar planet (exoplanet), but I thought this would be a cool thing to try.  A while ago I put together a time-lapse movie of the 2012 Transit of Venus.  More recently, during a public talk on exoplanets, I saw a video someone had made to demonstrate the transit method used to detect planets around other stars.  The video looked a bit like my time-lapse, except that it was a simulation.  I thought, “why not try to get a real light curve from my transit footage?”

A History of the British Sky

I have compiled the following time-lapse video, inspired by Ken Murphy’s “A History of the Sky”.  Ken’s time-lapse is actually a mosaic of 360 smaller individual movies, each showing the San Francisco sky throughout a single day.  The result is a brilliant and unique visualisation of an entire year of weather in just a few minutes.

I present Her Majesty’s equivalent, “A History of the British Sky”, recorded from the top of a building near the Welsh border.  I’m sure you’ll agree that the time taken to process over 3 million individual photographs is repaid ten times over in this video.  Such a wealth of information in one view; it’s a feast for the eyes.  You can see the change in the length of the British day, for example. And you can clearly pick out the season of summer.

EDIT: Positive responses to A History of the British Sky:

“I always knew you could get different shades of grey, but never so many different types of grey.” -Gordon

“I can see summer! It’s up in the top-right!” -Tina

“This particular year looks drier than most.” -Margaret

Seriously though, I’d like to thank Ken for his original and actually genuine creation, which, unlike my version, took an awful lot of commitment and skill to pull off.  Such a cool idea!

Astrocinemagraphy (not a real term)

Here, I just had a stab at making a cinemagraph of the Anglo-Australian Telescope (AAT) using frames from colleague Ángel R. López-Sánchez‘ excellent time-lapse movie “A 2dF night at the Anglo-Australian Telescope”.  Ángel is an astrophysicist at the Australian Astronomical Observatory (AAO) and spends a lot of time using the AAT for his research.

As for the image, I made it with Adobe After Effects.

Aligning sun images using Python

Fix it in post. It’s a common phrase in photography and one which is widely recognised as landing you in hot water if you’re not careful. Fix it in post-production, fix it after the fact. “Hm, I’ll just fix that in post.”

Well when I spent a day taking a few hundred photos of Venus crossing the sun last year with the intention of creating a time-lapse but without a tracking system, “fix it post” was my mantra by necessity. For 7 hours I followed the sun across the sky just by nudging my camera mount this way or that. As a result the sun was in a different place in every photo. The fact I wasn’t standing on the equator at the time meant it rotated too.

Transit of Venus 2012 time-lapse

Venus passed in front of the sun on 6th June 2012, and all the while I was happily photographing it from tropical North Queensland.  Here is the time-lapse of all the photos I took throughout the day.  The music is by Kevin Macleod – thanks Kevin!

Graphically verifying time-lapse intervals using ExifTool (and Excel)

Here’s a quick and easy way to check time-lapse intervals using a combination of ExifTool, (a great command-line application for reading and writing image EXIF data) and a program such as Excel to process and plot the data.

Hyperlapse photography test using existing structures

I’ve long been a bit of a time-lapse junkie, so when I saw this video of Moscow a few months ago I was really impressed. People have started calling this technique ‘hyperlapse’, and it’s a combination of time-lapse photography with a large but calculated movement of the camera between shots. I thought I’d have a go without using any special rigs or mounts – instead of worrying about moving the camera precise distances, I thought I’d find some existing structure to do the measuring for me.

PIR motion sensors for time-lapse photography

Using a household security sensor to trigger time-lapse cameras “when stuff is happening”

How do you efficiently capture something about as big as a truck being sporadically hand assembled over a period of one year?  This is a question I recently faced when setting up time-lapse cameras on a major instrumentation project at the Australian Astronomical Observatory (AAO).

A typical time-lapse approach is to take photos at fixed intervals for the duration of whatever process you’re trying to capture.  The AAO’s assembly schedule for HERMES, a high resolution astronomical spectrograph, didn’t lend itself to this approach for three reasons: i) nothing was going to happen on evenings or weekends; ii) there would be many ‘dead’ periods when work was being done outside of the main assembly area and therefore out of shot; and iii) it would go on for a year, which meant camera shutter life might have become a limiting factor.  What I needed was for photos to be taken only when work was being done, and to do so at short intervals so that these events translated into a reasonable number of frames in the final video.

I decided to use a Passive Infra-Red (PIR) motion sensor to govern when the cameras were triggered.  These sensors are used all the time for outdoor security lights, and they’re super cheap (about $20 from a DIY store).  By using a PIR sensor, the cameras would only fire when someone was in the room, i.e. “when stuff was happening”.