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FastFourierTransform
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27 Oct 2020 04:33

Watsisname wrote:
Source of the post I wondered if I could actually resolve the spectrum of a plasma using nothing but an old audio CD-R. Turns out, yes! Sometimes high-tech problems have low-tech solutions.

Just amazing. Do you mind if I show it to some collegues?
 
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27 Oct 2020 13:00

FastFourierTransform wrote:
Source of the post Just amazing. Do you mind if I show it to some collegues?

Please feel free! We're a public forum. :)

A-L-E-X wrote:
Source of the post can this be done with any optical disk (DVD//DVD-R/W//CD//CD-R/W,etc.)?

Yes, I believe any of those will work. The key here is that the regular spacing of groves on an optical disk acts as a high quality diffraction grating. 

I've long known of this effect (it's rather hard to miss), but did not realize that it could resolve a spectrum this well (and it's even more distinct by eye than I was able to capture on camera due to imperfect focus). Also, just like how most spectrometers limit the light through a tiny slit so that you can distinguish individual spectral 'lines', it's helpful if the light source you want to see a spectrum of is either a point source or very narrow, in this case a thin plasma filament. Otherwise an extended source will make a smeared out overlapping spectrum, and the unique spectral features may be harder to see.
 
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27 Oct 2020 15:08

Yes!  I've seen the beautiful patterns visually too but didn't realize it could be captured like this!  Great point about the light source, I was going to use a regular light bulb, I guess it wouldn't work well.  Can I still use a light bulb if I put a piece of cardboard in front of it with a very small hole in it to let the light through?  I dont have any plasma sources, unless I try using the fire from a fireplace or an open fire from a stove with the cardboard in front of it maybe?

edit- either of those might be too risky, I'll just look around for a place to get a plasma filament from.


edit 2- I wonder if a plasma TV with cardboard with a pinhole in front of it could work too ;-)
 
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27 Oct 2020 19:45

A-L-E-X, you could try things like various kinds of street lights.
 
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midtskogen
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27 Oct 2020 23:18

CD, DVD and blueray have different track spacings (I presume).  I wonder if they can be accurately measured (through low-tech science).  Sounds like another funny student exercise.
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28 Oct 2020 08:02

Watsisname wrote:
A-L-E-X, you could try things like various kinds of street lights.

Thank you Wat!  I have plenty to choose from ;-)  besides I want to see the differences in spectra between mercury vapor lights and sodium vapor lights vs broadband LEDs.
 
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08 Nov 2020 05:12

Fireball over western Uppsala, Sweden 2020-11-07.  Seen at a distance of around 450 km.

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A-L-E-X
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08 Nov 2020 05:55

Wow do you think that was from an asteroid or a meteor and how can one find out?  I recently saw a video from a doorbell cam in Alabama where it was stated that the fireball in it was from an asteroid from the asteroid belt and it was moving 4500 mph and burned about 20 miles up.  From that information can one determine its actual size?

https://www.wsfa.com/2020/11/03/video-b ... l-alabama/

https://www.al.com/news/2020/11/firebal ... ideos.html

That second link has a NASA scientist confirming that it came from an asteroid.
Last edited by A-L-E-X on 08 Nov 2020 07:34, edited 1 time in total.
 
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midtskogen
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08 Nov 2020 07:06

Asteroids and meteoroids are the same thing, just different in size.  If you mean from the asteroid belt, I haven't had time yet to verify it, but will do the homework.  Most meteors do.
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08 Nov 2020 07:35

Thanks Mid...I was wondering if something like this could also originate from a meteor shower (especially one that is known for fireballs like the Leonids or Geminids).
 
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08 Nov 2020 08:30

A-L-E-X wrote:
Source of the post I was wondering if something like this could also originate from a meteor shower (especially one that is known for fireballs like the Leonids or Geminids).

Too early for both Leonids and Geminids.  Also, Leonids are very fast and do not produce fireballs like this.  The only meteor shower that is capable of producing fireballs not too dissimilar to this one (though hardly this bright) is the Geminids.  Generally, meteor showers are associated with comets, which leave mostly dust and ice and rarely appear different from regular shooting stars (but bright flashes reaching full moon brightness are not uncommon for some showers).  The fireball in this case, however, was likely caused by a big rock, something in the order of a few hundred kilos.  It most cloudy where it fell, but the landscape was fully illuminated for a couple of seconds.  Swedish television has collected a few videos.
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08 Nov 2020 09:26

Thanks Mid.  I wonder if this fireball is in any way related to the one that was recorded over Alabama?
 
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08 Nov 2020 13:11

A-L-E-X wrote:
Source of the post I wonder if this fireball is in any way related to the one that was recorded over Alabama?

That was a week ago and we can be pretty confident that they have nothing to do with each other.  The one last night does not belong to any shower.

I have studied it a bit further, but haven't been able to make all observations agree perfectly yet.  Unfortunately, all cameras recorded it from similar angles, which makes thing more difficult.  But so far it seems to have been very bright even at 20 km altitude, and possibly still visible at 15 km.  That is almost unheard of.  The slope was likely pretty steep as well.  I wonder whether it could be iron rich and something that doesn't easily disintegrate. It may be something worth searching for, but it needs to be done quickly, since winter is coming.
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08 Nov 2020 14:33

This sounds like a very rare event- glad you were able to capture it!  Can you tell its composition from its color as it burned up?  Maybe you could triangulate its approximate landing spot if it did indeed reach the ground?
 
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08 Nov 2020 19:11

These seem to be more widespread right now, dashboard cam of a bright low flying meteor over NJ (also spotted in eastern Canada)

https://twitter.com/LakewoodScoop/statu ... 6%3Fs%3D19

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