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Very impressive. 3D printing (or ALM as we should call it now) really is quite a mature technology. What printer are you using?
I suspect that would be a bit high-brow for most US commercial FM stations and one wouldn’t want to condone putting someone’s eyes out just because they didn’t cut their hair.
Steve – I remember driving back from the eclipse and they were playing “eclipse related” tracks in rotation on most of the Nebraska FM stations we could find. TEotH was one, You’re So Vain was another. Then the eclipse connection got really weak.
Grant – Nice. This Celestron astrograph seems to perform very well at f/2.2 although your H18 isn’t that much of a test for a thing that is supposed to have a 40mm diameter well corrected focal plane! Are you going to try it with a bigger sensor? I’d certainly be interested to see how it performs in real life with a full-frame (36x24mm) sensor.
Andrew – Nice observation. I guess this is way too faint to see any colour in the SN even with the 24-inch.
Here’s an image of it from a few minutes ago. The telescope wasn’t tracking very well and the SN is very close to the centre of the galaxy but you can see it.
Those were the days. We made a Wimshurst Machine at school a long time ago and used it for all sorts of interesting experiments. I wouldn’t want to fill in the risk assessment for one of those now. Just think of all of those volts.
So they have. Here’s a link to the Times obit although it is behind a paywall so you’ll need to register or be a Times subscriber to read it.
Thanks Martin. You can certainly see where all the Dexion went! I wonder what his neighbours in Dartford though of it all?
Roy. It may be the video compression but different decoders behave differently too. Could you give me a specific video and time offset where the effect is significant so that I can have a look. Nick.
You don’t need the HD version of UFO capture for SD cameras. I’m using UFO Capture V2.24 under Windows 7/64-bit. The PC has three PCI Osprey 210 video capture cards and I run three instances of UFO capture for three cameras, 2 Watec 902H2s and 1 other B&W monitor camera. The PC is an old Dell Optiplex 780 with an Intel E8400 CPU running at 3GHz and 8 GB of memory. Each instance of UFO Capture uses around 150MB of memory so they are very lightweight. Each instance will use a different CPU core if it can and even with all three cards detecting the CPU load never goes above 30%
I certainly prefer having a PCI card for the video capture since I occasionally had dropped frames using a USB dongle. The Osprey 210 is a really nice card. They are a bit pricey but occasionally come up at a decent price on ebay. I’ve never had any problems since I started using it.
I don’t know the details of their licensing model but the problem is solved if you use a single PC.
Jimmy, Thanks for pointing me at Baker’s work. I really should have known about him as a famous local writer. I’ve bought The Peregrine from Amazon and look forward to reading it.
Yes, Denis does live in a fantastic location. I’ve visited many times and the scenery and skies are stunning. I was only teasing him, slightly, over the temperatures. I would have thought that it was too windy on Tarbatness for midges but I did suffer from them at the Falls of Shin the last time I was up although that was mainly my fault for wearing inappropriate clothing.
I don’t keep stats on how many nights that I observe since they would be dependent on many more things than the weather. My meteor cameras are running every night though so stats from them do have some significance. In 2017 I detected 3751 meteors on two cameras (4451 in 2016) and I detected at least one meteor on 227 mornings and 180 evenings (238 and 189 in 2016) so it does look as if 2017 was a bit cloudier than 2016.
Also, slightly off topic, I attach the max/min temperatures for my back garden weather station over the past three years. Denis may get the best observing weather but how many days were over 20C last year?
I think corkscrewing meteors with this kind of observable transverse displacement are physically impossible.
A very hand-wavey argument goes as follows (although you might like to check my maths since I worked this out while cycling home tonight). Let’s assume the meteor has an entry velocity of 60 km/s and it decelerates to zero in 1s. That means it is visible for a track of length 30km. Your photos show around 7 cycles of wiggles with an amplitude of around 1/50 of the trail length, so let’s say 600m. That’s +/- 600m transverse displacement in 1/7s. Assuming the transverse displacement is sinusoidal the peak transverse velocity would then be 600*(2*pi*7) m/s and the peak transverse acceleration would be 600*(2*pi*7)^2. This would require a sinusoidally acting transverse force more than 40 times the along-track drag force. That is just not physically possible.
I still think the best explanation of this is wind vibration.
One other explanation which I have seen in practice on my images is wind vibration of the camera. This can have a negligible effect on the star images since they are integrated over minutes but show up very clearly on meteors which are only present for a fraction of a second. You even see this on trailed objects like minor planets in long exposure images. If this were a real, physical effect on the meteroid itself you should be able to calculate the transverse acceleration using the amplitude of the corkscrew and the presumed range and along-track angular rate. It would be interesting to see whether this looked physically reasonable given the kind of off-track lift force that you might imagine.
And the Guardian has ‘Oumuamua on its front page today. Hmmm. And I was worried that the Daily Mail might pick it up.
