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The aim is to create an artificial star of known size and shape. A very narrow laser beam tuned to exactly the same wavelength of sodium light stimulates fluorescence at the same wavelength from sodium in the upper atmosphere. (Incidentally, that sodium comes primarily from sea salt.)
A telescope looking at that fluorescent spot should see an immobile spot with a shape and diameter set by the resolution of the optics. In practice it sees a large shimmering moving blob because of the atmosphere. Clever software quickly works out what distortions should be made to the telescope to return that blob to its undistorted shape and very fast mechanical actuators then make the corresponding movements to an optical element. Voila, diffraction-limited images through adaptive optics.
If you watch the video feed for long enough you will find that at some times that happens about once a minute. Sometimes the vents do little but leak gently; sometimes they explode and send material hundreds of metres into the air.
Note that the side of the cone has collapsed. I watched much of that happening in real time.
All rather interesting as long as you are at a safe distance.
I have found it majestic and hypnotic but not, perhaps strangely, scary. That’s the case whether watching live or over the net.
Last night (i,e. 24 hours after the above posts) it became markedly more explosive with enormous lumps of lava being thrown a hundred metres or more into the air. It was hard to judge scale but some of those pieces must have been well over a metre in diameter and so weighing several tonnes each. I was also watching what started out as a very minor effusive vent become much bigger and explosive.
Excellent live coverage at https://rtvc.es/en-directo/
It helps if you understand Spanish …
Their live feed from the Cumbre Vieja shows that large amounts of liquid are still coming out but the explosive gouts appear to be somewhat reduced from when we left several days ago.
Not now.
By chance we took out fire / flood / vandalism / etc insurance on our place a week or so before the eruption started. The insurance company didn’t want to touch our observatories so we were going to check for specialist companies when back in the UK.
It is possible to insure almost anything against almost anything if you are prepared to pay the premium.
This is a before and after image of an amateur observatory on La Palma. Note the apertures of the telescopes — 80cm and 50cm. Serious kit.
I never met Rico but exchanged email.
Thanks Dominic.
Good work.
Have you updated the list of objects that can be tagged to include the latest asteroids and the solar system satellites?
Latest news: getting there is currently a PITA. The airports at both La Palma and La Gomera (SPC and GMZ respectively) are now closed because of ash from the volcano. The rest of the Canarian airports are still open so you could fly into LPA, TFN or TFS and get the ferry. I wouldn’t bother myself.
Thanks Dominic.
You are likely correct about the WHT. I just assumed it might be trying to look at the sky without actually checking on its current status.
Travel to and from La Palma is straightforward for fully vaccinated European citizens. SWMBO and I had no problem getting there in late June and coming back the UK required us to have PCR tests before and after the flight this week. Passenger location forms were required by both the Spanish and UK governments. The tourist industry is recovering and accommodation levels are about 80% at peak; most visitors are from Germany and The Netherlands, but that has long been the case.
Kevin’s all-sky camera is reporting a light dusting of ash at Tacande.
The INT and NOT (at least) are not opening up tonight because of ash in the air. Not yet head about the WHT and GTC.
Eruption now becoming quite explosive. Pyroclasts reaching 300m in altitude according to my rough and ready observations and trigonometry.
Certainly much noisier and brighter tonight, though the noise is mostly coming in pulses and the background roar is noticeably lower.
Now that more information is becoming available I have been able to pinpoint the location of the eruption to within a few metres. As best I can make out, it is at latitude 28°36’54″N, longitude 17°52’02″W which is 3.2±0.1 km almost due south of here. (Here being Tacande Observatory which is labelled on Google Maps.)
The view is quite impressive after dark but the volcano has caused no trouble at all for Kevin and me as yet.
The location is very close to this point in Google Maps:
https://www.google.es/maps/@28.6154215,-17.8670681,268m/data=!3m1!1e3?hl=en
Absolutely typical. Politicians always like to come rubber-necking when something mildly interesting occurs.
Further, they invariably promise that help and monetary compensation will be made available instantly. True in this case too.
There is still a very noisy pillar of hot ash visible from the window next to where I am typing.
It is a bit noisy and we have Bortle 9 skies to the south at present. I now have some more images and a few videos which are perhaps of interest.
Ah well. It all adds a modicum of interest to an otherwise tedious existence.
Incidentally I, SWMBO and two in-laws were stuck in La Palma for several days when Mount Unpronounceable erupted in Iceland a few years aback and closed down almost all European airspace. That one definitely increased the sky background brightness and reduced the transparency in the UK.
It is noisy and there is a wonderful illustration of the old saying: Red sky at night, vulcanologists’ delight but everything else is just fine. The camera has lost its cooling (as has Kevin’s in the neighbouring dome) so we wouldn’t be observing anyway but otherwise there is no good reason not to open up the domes.
This one is taken within 3 minutes of the start of the eruption. My dome is to the left, Kevin’s to the right, largely hidden by the tree.
“provided the directions are indicated”. A very very important point. Thank you for drawing it to our attention.
I understand the reasoning behind why planetary images are generally shown “upside down” but (with one major exception) most everything else these days is displayed with north to the top and east to the left. Look at any major atlas, either on paper or on-line, and it will follow this convention. As far as I can tell, most images in the BAA gallery are similarly aligned though, to be sure, some are not but those exceptions seem to show no particular pattern.
My own images are generally N-up, E-left but that is primarily because that is the result of SWarp’s stacking algorithm rather than any conscious choice of mine. The raw subs are at whatever angle the camera happened to be at the time but a single sub is rarely of much use except perhaps for photometry where the angle and parity doesn’t matter for reporting purposes.
Now the major exception;: M31. Images generally appear East-up & South-left or NE-up & SE-left. My favoured explanation is that some people prefer to see the galaxy in a landscape view rather than portrait. Hubble’s famous frontispiece to The Realm of the Galaxies adheres to the N-up & E-left convention.
Does the absence of C, O, etc, indicate that the progenitor star was of relatively small mass and so significant He burning hadn’t started before it lost its hydrogen envelope in the red giant phase?
Or does it mean that all the heavy material has sunk into the core and that convection is insignificant?
I’d love to. My last attempt was 2021-09-01 and taken through thin cloud. Not so thin, actually, as I needed several 1-minute exposures to get anything measurable. It would normally take a single exposure of somewhere between 2-5 seconds.
Clouds even thicker since then with the same forecast for several days. I hope UK observers have better luck.
The 2021-09-01 observation will be processed and uploaded RSN, honest guv.
