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Hi a bit later than planned….
This is a multi plot of the three lyrid fireballs I captured this year. It is always re-assuring to see near identical spectra with meteors from the same stream.
Micahel, sorry for the delay, I use the 25mm (and occasionally 50mm lens) on my non spectroscopy narrow field of view rig but the spectra are all captured with 12mm f0.8 lenses.
cheers,
Bill.
This ones a bit better.
I have too many files to work with…! Just discovered I actually have the “unusual one” captured with MAD-ex! Not Definitely not a Perseid but it has a brief terminal flare. Youtube compression doesn’t do it any favours though ;-(
Nah, thats rubbish, I’ll try and get a better resolution one sorted….
Hi,
Did you happen to get the one at 21.30 (second spectra in my post) I didn’t get the zero order but if others did, then THIS is the one to concentrate on. This is potentially very interesting. The very high sodium signature is generally taken to suggest a recent origin and the fact it’s slow may be significant orbit wise.
It was a beautiful night, I even sat outside with a cuppa and some, of the now legendary (if the twitter response is anything to go by… ;-)) chocolate hob nobs for an hour or so.
NOVEX produced some interesting close ups. A few terminal flares and I was continually surprised by the narrowness of the persitent train. Didn’t get any distorting trains, the mesoshperic winds must have been calm…. I’m thinking I might add another narrow field system. It does produce fascinating results.
The MAD experiment also produced a couple of interesting results. see https://youtu.be/jXZzLsrjqpc
Although I’ve discovered I have a better one, need to upload that next.
A good night.
cheers,
Bill.
Hi All,
On the night of the peak my various camera/spectro systems recorded 482 meteor and 49 spectra (note, not all Perseids.)
Caught some very good Perseid spectra and am in the process of working through them. Here is first Perseid of the night.
Very strong signature from ionised calcium in the UV. The instrument corrected version “compresses” the other lines to such an extent I’ve just gone with the raw un-corrected spectrum in the graph. But this looks like a nice typical Perseid. Strong 557.7nm from the forbidden O line as usual in the video (not in the graph as it faded at the point I did the line scan) and ionised silicon double at ~635.9nm
Once I’ve got a couple more it’ll be interesting to compare these to previous years.
However, looking past the spectacle of the Perseids, THIS is the interesting one! (I think I’ve said elsewhere the most interesting things will be found in the sporadic population…)
I’ve now caught several with almost identical characteristics. Very slow, no IR lines at all and strong sodium line. (Take a look at Michaels’ post sporadic 3rd May. )
cheers,
Bill.
Appologies for the delay, been a bit busy last week…
The answer is yes and no, yet again. Yes the greater line count will give you greater dispersion and a “bigger” spectrum.
But due to the higher dispersion there is a magnitude penalty incurred. That is, you’d need a brighter meteor to exploit the gain and as there are fewer brighter meteors than faint it starts to play against you.
Also the shorter focal length lenses tend to have more field curvature and vignetting so there are some geometric issues that would need to be contended with should you capture a meteor.
However the bottom line is use what you have, I have captured spectra on a variety camera/lens/grating combinations. It’s just a matter of patience.
cheers,
Bill.
THAT is the toughest question of them all!!! It’s ALL a compromise. All of my spectro systems are 12mm (and now a 16mm) to get a larger image scale but that does sacrifice a lot of sky with the narrow fov’s. I did a short test with a 3-8.5mm f1.0 lens set to ~7mm a while back and that gave a decent result spectroscopically so I’m planning on running that a bit longer after the summer when the sky gets darker again. There’s also the limiting mag issue, that’s another set of problems…
I’m tempted to say 12mm is the best just from experience but there are a lot of variables! No easy answer I’m afraid.
Cheers,
Bill.
Hi,
That’s a good catch, However from my own experience working with low res spectra is always a bit tricky.
One of the things that interests me is developing what I called “comparative spectroscopy” in the Astonomy Now article, and this turns out to be an excellent example. Although relatively low res there are definite features in this example but strangely it’s not whats there it’s whats NOT there!
Firstly it is relatively slow moving, then there is a clear “gap” in the spectrum in the blue green part and finally there are no, usually very prominent, atmospheric lines in the near IR.
Take a look at this. https://www.youtube.com/watch?v=1pfwYQ_dM1E
(I wouldn’t trust the graph, the actual lines are OK but the instrument correction was highly experimental…)
Slow moving, with a gap in the blue/green and no near IR lines. So now we can start to see these may be related, they are definitely made of the same stuff and behave in the same way, ablation wise. With only one example and no clear shower association then it looked like a sporadic but with more examples then maybe it/they are not. THEN your into looking for parent bodies and new showers and that’s when it gets really interesting!
It’s a potentially a powerful tool but unlike nice neat orbital elements spectroscopic reduction is a lot more subtle!
cheers,
Bill.
Hi,
Thank you all for the kind words. I have been describing the experience as both terrifying and exhilarating at the same time. Now that it’s actually begun to sink in I’m beginning to fall more on the terrifying side of the scale 😉
It all happened VERY fast and I owe a great deal to a few academics who really pushed it through the system and pushed me to pull it together. Possibly a debt I will not be able to fully repay. It has been quite a challenge.
However it feels fantastic!
Cheers,
Dr Bill.
Hi,
There are a few more formalities to complete. Despite being employed by the university for 23 years I’ve never been involved in the academic side of things, so this is all new to me. It’ll be a couple of months before it becomes public via the library (or via me but that’ll be after the library has the offical bound version archived.) It’s all quite quaint in it’s way.
Regards,
Bill.
Hi,
The very first spectrum in this thread should be treated with caution. By that I mean a lot of the features are artifacts caused by the interline nature of the camera and very poor dispersion aspect. The others were captured with much better dispersion aspect and are pretty much genuine.
With the reference libraries that are available it is possible to have a good stab at most of the lines. There are surprisingly few elements involved. Due the electronic configuration unsurprisingly the majority are Fe. There are just a huge number if Fe multiplets from the UV right through to the green/red end.
Most pro observers only use Mg, Na and the series of Fe multiplets around the Mg line. As these are the most common and strongest lines the ratio’s can be used to construct ternary diagrams that can reveal quite a lot about any given meteor and the comparison to others. However due to the inherent lack of inital condition knowledge the method needs quite a lot of care
cheers,
Bill.
Hi Alex,
Yep, the one on the 22nd was a cracker as was the one right after it. Unfortunately I didn’t catch that on a “NOVEX” system. However the one on the 25th was equally impressive. I’m saving the “Interesting” graphs for the paper but what I can say is that the group of Lyrids I have show the most astonoshing spectrum similarity I have seen so far. Better than both the Perseids and Southern Taurids I have.
It’s truly fascinating stuff!
See you In Edinburgh.
Cheers,
Bill.
Hi James,
Thanks! It’s the technology that makes it possible. I often wonder if the engineers and designers at Watec ever considered that, what was probably made to be a high spec security camera, would have such a global impact on a subject like meteor astronomy!
I hope you get your meteor camera up and running soon.
Cheers,
Bill.
I also caught the one on 20170425:230306ut on a different system in the second order. Not as bright of course but for a video meteor spectrum this is excellent dispersion.
A beautifully resolved set of Fe lines around the bright green Mg line.
Gorgeous!
After a siginificant amount of preparation (which can often be set to naught, especially in my part of the world!) the Lyrids delivered the most remarkable spectroscopy results I have had in some time.
Here are a few more graphs etc.
My ideas about comparative spectroscopy seem to be valid!
I can feel another paper coming on…
Cheers,
Bill.
Been doing some research….
It would appear the “melting” or “dissolving” meteors might be classed as the extreme end of the “dustball” meteors. It is remarkable to consider that given the initial small particle size the meteoroid crumbles to an extremely large collection of even smaller particles. Maybe >mm to micron size before evaporation is complete. What seems a bit of a paradox to me, however, is the textbooks imply that this disintegration speeds up the evaporation due to the smaller particles. That is bigger surface area more rapid ablation. But I think it can be seen that is not what happens in the video. The more robust particle, marked as normal, pops into and out of existance much more rapidly than the dissolving one. Even considering a single tiny particle after initial ablation, the video still gives the impression of a much slower demise. …AND on top of that the theory also seems to be that the meteor should also be brighter, that too doesn’t seem to be the case!
The splitting ones might be an intermediate case of the demise of a dustball. A particular case of unusual fragmentation. The same issues apply about speed and brightness I think and although some meteors are seen to fragment into distinct bits these all appear soft. For reference. Physics of meteor flight through the atmosphere by Opik (heavy duty and I don’t understand half of it! 😉 and Meteors comets and meteorites by Hawkins (much easier read and distillation of much of Opiks work). Both quite old texts now but fundamentals are sound. The problems then are still problems now!
I also reviewed a pile of older videos made using shorter focal length lenses and when one really looks closely there are actually quite a few of this type. The longer focal length lenses bring out the effects much more clearly.
So, enigmatic is actually an apt description!
These wonderful little cameras really are re-writing the rules!
cheers,
Bill.
Hi,
Thanks. Yes, there is definitely a complete spectrum (no pun intended!) of ablation characteristics.
Reviewing the videos from the other night I also caught a “normal” one on the same system. To show how the ablation differs I made up a comparison video.
It is here:
cheers,
Bill.
These “dissolving” meteors are proving to be fascinating…
In an attempt to better visualise the unusual ablation I’ve mounted 25mm lenses on a couple of cameras to give a larger image scale Unfortunately the corollary is a smaller field of view though ;-(
However caught this near perfect example of a melting meteor this morning.
The meteoroid must be fragmenting into a large number of extremely small particles to exhibit this behaviour. Even at this size they are still undergoing very rapid heating and evaporation. Just melting into the atmosphere!
cheers,
Bill.
One observation is an oddity but two is the discovery of a previously un-noted class of meteor behaviour!
Caught a second separating meteor this morning. Fascinating. Having viewed several hundred video’s there a a few suspicious ones but this and the previous are by far the most definite.
Hi Eric,
Appologies for the delay, did I ever reply….? Just checking the forum for the first time in a while. I’m afraid I have been out of the scene for a couple of months due to a horrific multiple fracture of my right arm. Bones sticking out in all directions, it was pretty gruesome! Needed several ops and I’m still in a cast!
However as an alternative source of information immediately the most excellent Nemetode website at
http://www.nemetode.org/analysis%20techniques.htm
have the technical notes here explaining just about everything!
Hope this helps.
Cheers,
Bill.
