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A slightly more positive view from down south. Two weeks ago I flew to La Palma via Gran Canaria. The final leg was at night and passe the north side of Tenerife.
The two big islands looked much the same as anywhere else in the overdeveloped world with a similar population density.
La Palma from the air was very different. The Santa Cruz, the capital, was visible from the air but very, very much less intrusive than the towns and roads of Gran Canaria and Tenerife.
Yet Santa Cruz de la Palma is just as well lit at ground level at night as is Santa Cruz de Tenerife.
Light pollution is entirely a legal and political problem, not a safety nor an engineering problem.
Prompted by this thread, I just took a look at the sun on the first occasion it has been readily visible for a few days.
The spot wasn’t visible to the eye at first, but was very obvious through 7x50B. Knowing a precise position, I was able to see the spot without the binoculars. My eyesight is not as keen as it used to be.
Before anyone starts panicking, all views of the sun were through aluminized milar film.
Duncan, this is an interesting idea. For the so-called ‘benchmark universe’, matter and lambda, the scale factor, a(t), is proportional to (sinh(t))^(2/3). So let’s try and see what the Friedmann equations look like if we keep this evolution of the scale factor, but restrict it to one component, which I assume is matter.
…
The universe has undoubtedly lost mass-density since the good old days. That is very much not the same as losing mass. And, as I noted, losing matter is not the same as losing mass.
It is extremely important to be precise in one’s terminology when discussing situations in General Relativity. For instance, it is very tricky to determine the mass contained within a region of spacetime other than in the context of an asymptotically flat background.
Stars loose mass processing simple elements into more complex ones. Our Sun loses about 4 million tonnes of mass per second doing this. Multiply by the number of stars in the universe….
The mass is not lost. It is converted into the mass of the photons which are emitted by the Sun.
Photons have no rest mass but they possess relativistic mass according to the famous E=mc²
The ground track from the Virgin site shows the launcher crossing La Palma at around T+ 560s. The vehicle is in the Earth’s shadow but the second stage motor will still be burning at that point (SECO is around T+ 590s). It will be over 500km up when it crosses over LP. It might be visible coming up in your north but I have no idea how bright the exhaust plume would be at that range and you have a bright Moon to contend with as well.
Thanks. I think there is a fair chance here and I have tipped off a few locals with an interest in astronomy, including a pointer to this discussion.
Nothing we can do about the moon but perhaps wide-field binoculars may help; the lack of daylight will definitely help. I’m certainly going to give it a try, weather permitting.
The attached plot should allow you to determine the visibility at your location. Use the ground track and launch profile plots to determine the altitude and great circle distance from your observing site and the curves show how far above the horizon the launcher will be. For example if it is 1000 km away and 150 km in altitude it will be around 4 degrees above your horizon.
First stage burnout (MECO) is at around 180s and occurs at an altitude of around 75km. For the far southwest tip of Cornwall the ground track shows a great circle distance of around 450km. This corresponds to an elevation of around 10 deg above the horizon so the first stage should be visible from Cornwall if the weather cooperates. The visibility from SW Ireland is similar.
If anyone gets any video or images please send them to me. I can include them in the Sky Notes at the next meeting.
If I understand the map and your plot, the launcher should be coming up from the northern horizon and reach almost the zenith from here in La Palma. The north horizon is obscured to some extent (I am due south of El Roque) but I will see what can be seen.
My mistake too — the object is (102550) 1999 UY17 — I failed to cut and paste the final digit.
I need to check other images of U Leo (there are hundreds) but most of them are properly centred and unlikely to show the region well.
When I return to LP more images can be taken; deeper too. If it is a star it’s quite likely to be brighter than 22.0 at minimum.
Yup. As I said, the MPC knows nothing. The nearest is (102550) 1999 UY1, several arcminutes away and V=19.2
Where does manipulation start though ? For example I would venture to suggest almost every deep sky, comet and planetary image in the gallery has had undocumented processing which affects the scientific value (non linear stretch, sharpening, noise reduction star elimination etc etc). As a science based organisation though contributors should welcome challenge and be able to supply the raw data if required. (With the new website there doesn’t appear to be any simple way to make contact with other members any more though)
Cheers
RobinHallelujah!
Pretty pictures are, well, pretty but the original data should always be easily available upon request.
For the avoidance of doubt: I keep all the subs which I subsequently process, whether or not the result is published.
I don’t have a Unistellar or the like and have no interest in getting one. Consequently no great research into your question has been done.
However, https://www.aavso.org/unistellar-evscope might prove an interesting and/or useful starting point.
Paul
Those hitting your hand are either absorbed (converted to heat) or reflected. Longer wavelengths are preferentially reflected than shorter ones which is why your skin looks reddish rather than greyish.
The photons hit a receptor in the retina (not the nerve directly). They are absorbed and their energy causes a chemical reaction. A long chain of subsequent reactions eventually reach the brain.
The photoreceptor is slowly (hence a long time taken for dark-adaption) returned to its initial chemical state, with the photon’s energy ultimately converted into heat.
An explanation in terms of QED would not be illuminating!
Hmm, I now appear to be Dr Paul Leyland.
Though I admit to having been doctored, I use the title only to impress the impressionable.
No worries. Perhaps there are impressionable people reading this.
Hmm. I measure the position of the nucleus as 06:20:55 +78:10:46.
There is a g=21 star at that position named EDR3-1140862546405873664 and a 15th magnitude star nearby in a whole bunch of catalogues, but I can’t find any catalogued galaxies.
There is also an IR source in the AllWISE catalogue J062057.74+780931.9 but no details other than the magnitude in various bands.
What a curious state of affairs, because it is clearly a large and bright object.
Added in edit: perhaps it isn’t a galaxy. Could it be an especially bright bit of IFN?
Caveat Lector!
I clicked on theSeqPlot link in a Firefux browser under Linux. It started creating an unlimited number of new tabs and I had to kill the browser to stop it.
Caveat Lector!
I made that comment.
https://app.aavso.org/vsp/ is the entry point. After filling various boxes, https://app.aavso.org/vsp/chart/?star=AE+And&scale=F&orientation=ccd&type=chart&fov=18.5&maglimit=20.0&resolution=150&north=up&east=left&other=all produces the chart which I use for my favourite variable.
https://app.aavso.org/vsp/chart/?ra=01%3A12%3A32.10&dec=65%3A43%3A21.0&scale=D&orientation=ccd&type=chart&fov=90.0&maglimit=14.5&title=Random+bit+of+sky&resolution=150&north=up&east=left
shows you the result of typing in specific coordinates rather than the name of a VS. This form is useful for finding solar system objects or distant galaxies as well as exoplanetary host stars.
