All Sky Camera Update

In 2020 I started a new job as a science technician in a school. A few months later the UK went into a coronavirus lockdown and I was told to do my job from home…which was an interesting challenge. We’d all seen it coming, so I’d already filled my home workshop with two carloads of broken equipment and antique science stuff in need of a polish, but it didn’t quite fill the time. So I started looking around for funding opportunities for…well, anything.

The Institute of Physics was offering grants for £800 for anything not-curriculum related and ideally relevant to the local area, and we’ve got a fairly dark sky, even from the roof of the school, and an all sky camera costs about £800…so I applied and they sent us some money. All Sky Optics, who supply this kind of thing, were hugely helpful both supplying the right bits and with lots of advice.

It’s been up there for three years now (it took a while to build as a project with students), without a break, in all weathers, taking hundreds of long exposure photographs each night, and then automatically stitching them together into videos each morning, all run by a Raspberry Pi and an astronomical camera.

As the name implies, it films (nearly) the whole sky with an ultra-wide angle lens, like an extreme fish-eye. The centre of the image is directly overhead, and the circumference of the circular image is the horizon. We’ve caught noctilucent couds, meteors, satellites including the international space station, the milky way slowly rotating, and quite a lot of seagulls. And the aurora. From our location it’s a reasonably regular thing, and wow, did it kick off last week. We normally get a green arc and some pillars on the northern horizon, but this one was directly overhead, with a lot of red in it.

The Class Of ’24

Oh. Some of you found this blog. Oh well.

So first bit of advice as you all go out into the big, bad, good, boring, fascinating world: if you have a blog, assume your 6th years will find it.

Not only that, assume everything you do online will be found by your friends, family, employers, prospective employers, that cute person from last Friday….the internet is as public as it gets, even things that claim to be private. (Hey, if you were a hacker, would you concentrate on the public stuff or the stuff that claims to be private?)

Other bits of advice: Learn to cook, it makes life cheaper and more fun. Always have an order-of-magnitude estimate in your head before doing the sums, it catches the easy mistakes. Google “Wheaton’s Law”, “Godwin’s Law” and “The Ballmer Peak”. Be generous with minstrels – yes, both the chocolates and the buskers. Anything is fixable, some things are not worth fixing, telling the difference is a major skill. If the folk on the spaceship had listened to Ripley and followed the quarantine protocol, Alien would have been a much shorter film. Do not stare into the laser with your remaining eye. Never leave your wing man (/woman/person….the original quote is “man”). RTFM.

My images of the year (the abstract blocks-of-colour one is MM’s photosynthesis project, shot through the various coloured filters being used, the prism is from WH’s spectroscopy project, when it was just sat out on a bench catching a few more wavelengths than just Neon’s:

A fractal-esque pattern of residue on filter paper, dark brown on off-white.

Fractal Filters

There’s some chemicals, even in a high school setting, that you can’t just pour down the sink. Some you have to neutralise, some you have to filter…some you have to neutralise to produce a precipitate, and then filter that.

These are in the latter camp. I noticed after leaving a particularly sludgy iron chloride suspension over a weekend that the precipitate in the filter paper had dried in a pretty fractal pattern, the larger surface area at the top of the filter paper and capillary action leading to a gradient of drying and cracking. I’ve been slightly more careful with further disposal methods, trying to find pretty examples.

She’s More Accurately Kerosene

I’ve been on a big The Interrupters kick recently, a fabulously tight punk/ska band who have instantly become one of my favourites.

But…one of their big tracks is She’s Kerosene, which got lodged in my head while I was working with kerosene. The big problem is the first two lines:

I’m a match, she’s kerosene,
You know she’s gonna burn down everything

I’d been trying to set petroleum fractions on fire, a millilitre or two at a time. They come in mixtures according to boiling point, the lighter ones are similar to petrol and will just ignite, but get towards the kerosene-heavy ones, or kerosene itself, and when you throw a match in…it just puts out the match.

Obviously, it still has those warning signs for a reason, dump a bunch of heat in, say a blowtorch, and you may have a problem. Create an aerosol or heat it up and yeah, it’ll burn. The vapour form is definitely dangerous, anything between 0.7% and 5% atmospheric concentration is explosive. That’s why it’s called, aside from kerosene or paraffin, “jet fuel”. It’s really good at dumping energy under extreme temperatures or pressures, and damn safe compared to gasoline. You want that in a jet plane.

But throw an match into a bucket of kerosene and you get a slight fizzle as the match is extinguished.

So to get this earworm out of my head, I’m recording it here. I love you, The Interrupters, but if you play with me you’re playing with pedantry.

I’m a match, she’s kerosene
But she won’t ignite like gasoline
She’s not, all that volatile
Arson with matches probably takes a while
While, while, while, woah
Matches might take a while
While, while, while, woah
Matches might take a while

She needs a chemistry refresher,
She won’t ignite at standard temp and pressure
She needs a mist, for this caper
Or a five percent atmospheric vapour
If she’d run a, trial experiment
She’d have used a faster accelerant
But now she, must admit defeat
Cos she forgot to read the hazard sheet
Matches, out of action, should have used
A lighter crude oil fraction
She’s not, all that volatile
Arson with matches probably takes a while
While, while, while, woah
Matches may take a while
While, while, while, woah

You play with me…you’re playing with pedantry…
You play with me…you’re playing with pedantry…

[repeat to fade]

Project Fish: Clachtoll Jellyfish Bloom

We took The Fish (need to find a better name?) over to Clachtoll on the west coast of the northern Highlands of Scotland to see what was under the surface. Good timing, it turns out, as a jellyfish bloom was going on. When conditions are right jellyfish reproduce in huge numbers all over Scotland, sometimes even resulting in issues for nuclear power stations!

Project Fish is the “engineering arm” of Fishing For Footage by Julia McGhee. (I use the term “engineering” loosely, especially in this context!)

The barn.megaparsec measuring spoon

Barn.Megaparsec measuring spoon.

A Barn is a unit of area used in particle physics, specifically particle accelerators like the LHC. It’s roughly the cross-section of a Uranium atom.

A Barn is pretty damn small.

A parsec is a unit of length used in astronomy, it’s roughly 3.26 light years, most of the way to the nearest star other than the Sun. A megaparsec is a million parsecs, which is nearly twice the distance to the Andromeda galaxy (at the time of writing…it’s heading towards us…)

A parsec is pretty damn big.

So what happens when you create a volume by multiplying them? A disc a barn across, extended into a cylinder a megaparsec long? You get a pretty useful measuring spoon, about 3ml.

STL file is here

Blender file is here

 

StellarSynth Image

StellarSynth / Timbre Of Starlight

This is a fun one, a bit of art-meets-science, which I’m finding myself doing more and more of these days, seemingly by accident.

A chat on twitter with an online friend about aurora on other planets spiraled a little, and now there’s two different projects on the go, from literally opposite ends of a spectrum.

Gahlord Dewald is a Hawaii based experimental musician, mainly double bass and old-school (literally circuit-design) electronics driven. In his own words, he “operates along several axis: improvised to composed, acoustic to electronic, beat structure to chaos”.

I can play the bass intro to “Little Green Bag” on a guitar. Badly.

Gahlord’s “Timbre Of Starlight”

Geoff’s “StellarSynth”

 

But we both love a bit of starlight (Scotland and Hawaii both have that in abundance), and starlight is really interesting to compare to music. Everyone is familiar with a rainbow? A nice continuous spectrum of the visible frequencies of light, from violet through blues, greens, orange and red…some people can even detect slightly further, for example into the UV…if you’ve ever thought flowers at dusk looked brighter than they should, you might have been picking up the ultraviolet they reflect.

But the light from the Sun isn’t that perfectly continuous spectrum, it has very particular gaps, which appear as black lines….like this

A spectrum with various lines missing

Public domain, via Wikimedia Commons user https://nl.wikipedia.org/wiki/Gebruiker:MaureenV

So we have a spectrum, measured in nanometers (a billionth of a metre) with particular lines missing. These lines occur because of the way individual atoms absorb and emit light, and it’s not just limited to the Sun. All stars do this…and clouds of interstellar gas, and the atmospheres of planets, and, in principle, the accretion disks around black holes.

Most modern astronomy is built on this idea: we can work out how abundant various elements are in anything we can see a bright light from. It’s incredibly useful.

But music…have a look at those wavelengths, in nanometers, again. Convert the nanometers to Hertz (“cycles per second”) and it’s bang in the middle of the human hearing range. So you can, mostly unscientifically, just “play” a spectrum. And it turns out to sound….interesting.

Gahlord is working on his own version from a very musical angle, with the beautiful name “Timbre Of Starlight“. I’m being far less artistic, and trying to stick to the raw data as much as possible, with a “playable keyboard” of the stellar elements. It reminds me of the Edinburgh University Design Informatics “Space And Satellites” art/science crossover project I was recently involved in, where we had a constant battle between “pretty” art and ensuring the originating data was justifiably represented (something the other artists, weavers, glassworkers etc also struggled with).

More to follow, both works very much in the initial stages

 

Gahlord’s “Timbre Of Starlight”

Geoff’s “StellarSynth”

 

Exoplanet Hunting (With Help From Tia)

As part of a course for work I’ve been tasked with completing a small project using one of a range of pieces of physics software. I picked one called Tracker, which allows you to track various physical properties in a video – including movement, acceleration, and light intensity.

 

Being able to track light intensity means we can simulate the “transit photometry” technique for detecting exoplanets – observe a distant star and look for periodic dips in the brightness as an exoplanet travels between us and the star, blocking some of the light.

 

To simulate this I used a spherical table lamp and a ball on a string hanging from the ceiling.  Note that the exposure setting on the camera is changed half-way through – the 50Hz flicker in the lamp due to the mains AC cycle is more obvious and produces more noise at lower exposure settings. Also note the upward spikes in luminosity just after the “planet” transits – this is due to the auto-exposure on the camera overcompensating, fixed exposure should ideally be used for this demonstration.

 

 

Because a ball on a string is effectively a pendulum, and because all “orbits” (including a pendulum) have the same period regardless of eccentricity (see tweet below), we can use a simple pendulum equation to get a good estimate of the period: T = 2Pi sqrt(L/g) , where L is the length of the string and g is local gravity.

 

 

With a string length of 1.63m we predict a period of 2.56s

 

Taking measurements of the minimal luminosity points on the right hand half of the graph we get the following periods:

 

2.49 , 2.53 , 2.53 , 2.53 , 2.53 , 2.53

 

Remarkably consistent, and taking an average of 2.52s it varies from our pendulum estimate by 0.04s, or 1.6% out.

 

Our main sources of experimental error are the 50Hz flicker on the lamp, the frame rate on the camera not necessarily catching the moments of maximal luminosity, and the autoexposure on the camera providing biased data. These could all be minimised by using a smoothing circuit or DC lamp for the flicker, and by using a high frame-rate camera with fixed exposure.  The latter solution could also reveal the characteristic details of the light curve that allow calculation of semi-major axis, star mass, star radius, planet radius, eccentricity, and inclination of orbit.

 


Note: The official installer for Tracker fails on an Ubuntu 20.04 system (previous versions on 18.04 worked), but it can be installed using the .deb file located here. I can’t guarantee unofficial sources, but opensuse.org are usually reliable.

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