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Posted: 24 Apr 2019 23:45
by Watsisname
@Midtskogen: Perfect skies!  

I haven't been up in the mountains for a while, but in the meantime I continue beach combing.  Today I found a great example of Carnelian.
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Posted: 06 May 2019 04:27
by Watsisname
The agate/chalcedony collection continues to grow, and now contains a few fluorescent specimens.  Here they all are under incandescent light.

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And now illuminated under 405nm (nearly ultraviolet) light.

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Fluorescence is always a nice surprise.  The intense green emission is caused by inclusion of Uranyl (UO22+) ions, which may also result in some radioactivity.  Also interesting is how the iron impurity which gives carnelian its vibrant red color is readily absorbing violet wavelengths, turning the stone black and opaque in this light.

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Posted: 06 May 2019 10:44
by Gnargenox
Can you take your ultraviolet laser with you while rock hunting?

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Posted: 06 May 2019 14:31
by Watsisname
It's a thought.  I normally only rock hunt during the day since that makes most objects of interest easier to find, but fluorescence is too dim to see in daylight.  Also many objects I'm interested in don't fluoresce, like petrified wood.  Hunting specifically for fluorescence at night might be interesting, but I'm not sure if my rate of finding things that way would be any better than the rate which I find them already during the day and then testing them back at home.  Maybe I'll try it anyway sometime just to see how it goes. :)

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Posted: 06 May 2019 14:58
by A-L-E-X
Watsisname wrote:
It's a thought.  I normally only rock hunt during the day since that makes most objects of interest easier to find, but fluorescence is too dim to see in daylight.  Also many objects I'm interested in don't fluoresce, like petrified wood.  Hunting specifically for fluorescence at night might be interesting, but I'm not sure if my rate of finding things that way would be any better than the rate which I find them already during the day and then testing them back at home.  Maybe I'll try it anyway sometime just to see how it goes. :)

Wat can these emissions be detected with a digital camera that has a UV pass filter on it?  UV photography is pretty neat- some plants have hidden markings that only pollinators can see (because their eyes are sensitive to near UV light.)

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Posted: 06 May 2019 19:25
by Watsisname
This isn't quite the same as ultraviolet photography, where you see the world with ultraviolet eyes.  Rather, think of it as normal photography, but with an ultraviolet light source.  Fluorescence is when that short wavelength UV light is absorbed and then the energy re-emitted it at longer, usually visible wavelengths.  Like illuminating glow-in-the-dark materials with a blacklight.  You wouldn't want to use a UV-modified camera to photograph this because then the scene would be drowned out with whatever color the sensor picks up UV as.  :)

In this case the photograph is true color, and the scene is illuminated by 405nm light (405nm is near the boundary between violet and ultraviolet, which the human eye and camera can faintly detect.)  All the re-emitted colors like the greens and yellows show up in the picture the same way your eye sees them.

Incidentally, I would love to have a UV-modified camera to play around with.  Maybe when I get an updated camera, I might try modifying my old one to do that.

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Posted: 22 May 2019 12:12
by Salvo
What do you guys think about this song? https://soundcloud.com/sidusbrist/lovely-eyes

It's a bit Guns N' Roses/Avenged Sevenfold inspired.  :)

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Posted: 26 May 2019 05:57
by midtskogen
Today's quake in Peru as recorded 10340 km away in my basement. USGS says M8.0, Peruvian authorities say M7.2.  I think the former is more correct.  The quake briefly maxed out my instrument.  The P-wave is realtively weak, having just cleared Earth's core.

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Posted: 26 May 2019 19:18
by Watsisname
Wow.  It's incredible how large and clear the signal is from such a distance.

As you gather more of these recordings I think it could be very interesting to arrange them by their distance from you, and in effect reproduce this figure showing how the seismic waves reveal Earth's inner structure.  In this case you were about 93° away, which fits what you say about almost losing the P wave to the liquid outer core.

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Posted: 26 May 2019 23:27
by midtskogen
Good idea, I'll add it do my list of very interesting this to do when I get the time.  I have 12 years of data, I think.  I could plot every 7.5+M in that time, for instance, and order by distance.

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Posted: 04 Jun 2019 03:33
by Watsisname
A somewhat random assortment of recent photos.

► Alpine Flowers


► Mountains


► Rocks and Gems

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Posted: 11 Jun 2019 22:06
by Watsisname
Giving hard rock mining a try.  There's a marvelous spot hidden up in the hills nearby where veins of blue translucent agate/chalcedony run through volcanic rock that's tough as nails.  It's some of the most intense color I've ever seen in a stone. I spent a good portion of a day working at it with rock hammer, sledge and chisels and came back with a couple kilos of raw material.  Very fun and interesting experience.

► Show Spoiler

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Posted: 12 Jun 2019 09:36
by FastFourierTransform
Beautiful. That color contrast! :D

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Posted: 24 Jun 2019 03:04
by midtskogen
Noctilucent clouds over Oslo last night.  Not very bright, but visible even in the southern sky.


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Posted: 24 Jun 2019 05:09
by Watsisname
Nice catch.  They were over here as well last week.  Saw them low in the north driving past Seattle in the morning.  Didn't get any pictures, though.