Observing a solar eclipse with high-altitude Pis

Helen: We’re pleased to welcome back to the blog a regular guest, high-altitude balloonist Dave Akerman. You’ll have gathered that a noteworthy astronomical event is to take place across northern Europe on Friday, and as you’d expect, Dave has plans. We’ll let him tell you all about them.

As you have probably heard by now, there will be a total solar eclipse this Friday morning, with the path of totality passing north of the UK and directly over the Faroe Islands.

Path of totality

In the UK we should see about 90% of the sun eclipsed by the moon, with the north of Scotland getting the best view assuming no clouds get in the way.

By now you are probably wondering what all this has to do with the Raspberry Pi, and the answer is that I will be flying two Model A+ Pis on a balloon from (no, not the Faroes) Leicester racecourse. Additionally, there will be several more Pi boards decoding the transmissions, and a V2 Pi B+ showing the results on a large monitor. The launch will be at about 8am so that the balloon is nicely high during the peak of the eclipse at about 9:30am.

Raspberry Pi weather balloon: an earlier launch

An earlier launch of a Raspberry Pi with a weather balloon

Some of you may have followed some of my previous flights using the online map and live image page. This time though, there’s an extra special option for your viewing pleasure.

Live TV.

The launch will be recorded by the BBC and some of the footage will be transmitted on an extra BBC Stargazing show on BBC1 that morning (9am to 10am). Also, there will be a couple of very brief live segments where, hopefully, I get to show some pretty live images and say “Raspberry Pi” as often as possible. Assuming we get to recover the flight, then some of the recorded video should end up on the main Stargazing show in the evening (9pm-10pm, BBC2).

The plan looked a tad uncertain earlier in the week because weather predictions gave me a choice of landing at Heathrow or Gatwick. I spent a lot of time speaking to the BBC trying to come up with a plan that lets us launch but without getting onto the national news for all the wrong reasons! One rejected plan was to launch from Jodrell Bank (from where the main Stargazing show is broadcast), but for some reason they don’t allow mobile phones or 3G there. Another plan was to underfill the balloon and get it to land near Dieppe in France. As of Wednesday morning, though, predictions are continuing to improve and I’m now confident of getting this flight to land somewhere safe in England, instead of having to trek to France to recover the payload.

The reason for launching from Leicester is that the BBC are running a “spectacular live event” from the racecourse, open to the public from 9am to 3pm and then 6pm to 9pm. Entry is free so please do come along if you can. They have a real astronaut and plenty else of interest – see this information page. Also, Leicester is home to the National Space Centre, so there’s plenty to see if you do decide to visit.

Helen: If you want to complement the coverage from Dave and the BBC with your own observations, the Royal Astronomical Society and the Society for Popular Astronomy have produced an excellent pdf guide to this Friday’s eclipse, explaining how to view it safely and what you’ll see if cloud cover doesn’t spoil the fun. Remember that cameras, including the Raspberry Pi camera module, are liable to be damaged if you point them directly at the Sun; don’t try direct eclipse photography unless you have the proper filters, but do bear in mind that you can achieve some very pleasing results without any specialist equipment by photographing a pinhole projection of the eclipse.


Dave Conlan avatar

Sounds great, but I’m wondering how he’ll be getting the camera to face in the correct direction.

Mark A. Greenwood avatar

That was my first thought as well. I suppose if you do video and the balloon rotates then you should get at least some frames pointing in the right direction. Fingers crossed it all goes well on Friday.

Dave Akerman avatar

Time ran out on doing anything clever, however payloads naturally spin so it’ll point everywhere sometime. We have some videos cameras as well as the Pi boards transmitting live, still images.

paddyg avatar

When looking at pictures from high altitude balloons before I’d noticed that they spin but not thought how odd that it. Presumably it’s a function of ~m scale wind-shear and turbulence. I wonder if the meteorologists use that info in any way?

Michael Horne avatar

Hi Dave,
Will we be able to track the flights on the map? If so, what are they going to be called?


Dave Akerman avatar

Yes, they’ll be on the map and the image page (links in the blog post above). There are 2 Pi A+ boards each with one of my PITS+ boards for normal RTTY radio telemetry and images, plus a LoRa (Long Range Modem) board sending data about 5 times the rate. The payload names are KRYTEN (RTTY) and RIMMER (LoRa) for the first Pi, and MARVIN/ZAPHOD for the second.

MalMan35 avatar

すげー!!!That is so cool!!! I wonder when the next solar eclipse will happen in japan.
P.S. I am not actully Japanese that was just some Japanese I learned ;)

G avatar

I assume clouds are not an issue at that hight?
I would think some image SW which tracks a high intensity ‘blob’ is useful. There should be enough time to get that SW to you, but I can’t write it.

Dave Akerman avatar

Yes, this will be *well* above the clouds.

If I get time I’ll do some “blob-finding” code. I know what to do just need to get everything else done first.


G avatar

(That is what I thought. My post was an implied invitation for somebody else to do it. I assume you can test it with a Pi camera and a light bulb….)

Dave Akerman avatar

Strangely, there’s a bright yellow thing in the sky today, so I’ve been testing with that.

G avatar

Where are you? California? Can’t be UK!

Alan McC avatar

Excellent. I remember exchanging Tweets on this subject months back with Dave and Pi Guy “Matt T-B” =o) Delighted to see all is coming to fruition. Better get up on my roof to get the satellite dish pointing back in the right direction {thanks again Mr Mistral (wind)…} to follow along on BBC !


Tony M avatar

I know it would be dangerous to look at a solar eclipse with the naked eye. Would it be possible to use the Pi camera to look at it instead, or would a special filter be required on the camera lens?

dcrunkilton avatar

The previously mentioned pinhole substitute for a lense can project an image of the sun onto a wall from a blocked out window.

If you are outdoors, exposed developed (as in blackened) photographic film has been used as a direct viewing filter. This also can be used as a filter over a camera lense to protect the sensor. For eclipse videos produced by this technique search youtube for “albuquerque solar eclipse BabyFreshTV” without the quotes.

A telescope or binoculars used as a projector will display a small image on a card about 20-30cm behind the eyepiece. The pair of dark circle shadows in one of the is cast by the binoculars. The eclipsed sun shows in both photos. Do NOT look directly thru a telescope or binoculars at the sun even with a filter.

Haggishunter avatar

From the twelvecast it looks like the BBC have picked one of the few areas of the UK that won’t have cloud cover tomorrow. If so, well done them – at first I thought it odd to have the party in the half of the country furthest from the path of totality, but at least they might get a decent view.

Gavin avatar

And they’re off, good luck and congrats on successful launch.

PiGraham avatar

Did the BBC bar Dave from mentioning ‘Raspberry Pi’?
It’s a shame the gremlins struck but I look forward to seeing the HD images later on.
Well done.

Michael Horne avatar

I think he wasn’t allowed to name-drop. Which is a bit narrow-minded of the Beeb.

Dougie avatar

It seemed like Dave was trying hard not to say “Raspberry Pi”, clearly the production crew had nobbled him.

Still, it’s good science.

My efforts are https://plot.ly/~Dougie/280/_20th-mar-outdoor-temppressure/

AndrewS avatar

Having seen coverage of some of Dave’s previous launches, I thought it was incredible how “straight up” the balloon went. Must have been very windless!

Helen Lynn avatar

Travelling across East Anglia and the East Midlands to Leicester on the train between around 7am and 9am, I noticed many wind turbines, none turning.

Clive Beale avatar

Maybe you were rotating at the same speed. That’s exactly how Einstein invented relativity.

Gavin avatar

Dave’s BBC coverage is up – see iPlayer, Dave’s bit at 28:00.


Dave Akerman avatar

I got interviewed by BBC Radio Leicester and I have to say that was way nicer than the TV stuff, mainly because of the lack of time restraints. Linky here – https://soundcloud.com/david-akerman-2/bbc-radio-leicester-interview

Sally Howell avatar

Have seen ariel photo’s of when Dave Akerman was at a secondary school in Grantham last week. They are totally amazing!

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