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Hi,
I use the free spectroscopy package Visual Spec. It is much better than Rspec AND you don’t get stiffed for 100 bucks every time they decide to update it. Note, for legal reasons I stress this is my opinion only… 😉
Cheers,
Bill.
Mmmm, could be, the time is spot on however the direction on cam 8 is quite a bit to the south azimuth wise. If I get time I might do a manual run through with UFO Orbit. I’ll keep you posted (Or if any other observations pop up….)
Bill.
Hi,
The weather here was extremely poor on the 8/9 so thank goodness for the radio observations! Saw a nice clear peak on the radio. Tweeted a few graphs but they could still do with some tweaks. 10 min bins loses some of the general form and hourly bins lose the detail, might try 30min counts….!
In any case the peak rate with me was between 0000ut and 0100ut with a total count of 138 meteors (Draconids plus any others) Entirely subjective manual counts from the HROfft captures, so probably a few +/- throughout . A good result though.
Would’ve been nice to have have had a peek at the shower visually.
cheers,
Bill.
Hi,
I am relieved, put it down as another success for my comparative meteor spectroscopy method…!
The power of the spectrum!
cheers,
Bill.
Here’s the frame I used to extract the spectrum. The star field can be identified by Dubhe, brightest star lower left. The actual meteor would be ~30/40mm off the edge of the frame on this scale. I hope someone else has it because I’d be surprised if this pans out to be a Perseid, it doesn’t fit the profile…. but you never know!
Hi,
Regarding space junk, I’m not sure. The fact that the spectrum had a set of the near IR atmospheric lines suggests it was doing a fair clip. All of the re-entry video’s and spectra I’ve seen have been relatively slow (and horrendously complex!) Whilst the most prominent metal lines are certainly Mg and Ca there are weak Fe features which are in the background of most spectra. No guarantee but I’d put my money on it being a tiny bit of something natural.
Cheers,
Bill.
Hi,
I was hoping you’d catch something with your N facing camera. However even considering the diffration angles involved I don’t think that was the one. I’m on a different machine at the moment but I will double check.
cheers,
Bill.
Hi,
An excellent summary of the problems! As strategies evolve one of the things I continue to do (after the “discovery” of the rapid changes in spectrum of the bright Perseid, 2013) is to examine the spectrum videos frame by frame. This is in an effort to mitigate some of the very noise and absorption issues you mention. By taking the shortest possible “length” of spectrum to sum up to get a viable spectrum. The best, of course only need one frame but on others you need to use longer temporal sections.
I have been saying for years that meteor spectroscopy is a tricky proposition analytically speaking. There are a few published papers by Jeniskens that discuss “quantitative” spectroscopy but without some assumptions I’m not fully convinced (maybe I just don’t understand the maths!)
Nobody knows any physical information about the particular meteoroid that produces a particular spectrum beforehand and THAT is the problem. EVERY other aspect of the meteor we then capture is entirely random. Time, position, duration, luminous efficiency (and that’s the big one…) etc.
All we can determine with any certainty is the geocentric velocity, then comes along a spectrum carrying all these observational variables, did I mention tricky… ;-))
I think this is one of the reasons that the technique of comparing particular line ratio’s (as devised by Borovicka) is about as good as we can get.
HOWEVER even with qualitative results significant differences is spectrum characteristics can be identified and I think that’s why sporadics are the most interesting proposition and what I’ve called Comparative Meteor Spectroscopy can get us into some sort of new taxonomy over the coming years as data builds up.
Observers have been conducting meteor spectroscopy for a lot longer than me but these programs caught large fireballs on rare occasions but I think I’ve been the first to do regular video meteor spectroscopy, (in the UK?), and that’s only been since 2008 (or 2006 if you include my very first tests). So we’re only just starting a new field. Another 10 years and we’ll have a whole new picture of what’s in our planets neighbourhood.
All we can do is work with what we’ve got…
cheers,
Bill.
Well if they’re driven EXACTLY in phase they’ll either both be open or both be closed. If driven exactly out of phase it’ll look either always open or always closed. If the drive signal is allowed to drift they’ll strobe in and out of phase. If that’s not what happens then I’ve no idea!
Hi,
Some objective perfomance,
First pic is the LCTec shutter running at 20Hz. The upper trace is the photodiode output. You can see how it is twice the frequency of the driving signal, lower trace.
The second picture is what I reckon is the best performance of the smaller, cheaper shutter. It only has the upper trace. Ignore the frequency on the image, the scope is picking up some of the much higher frequency noise. The drive signal was 6Hz giving 12 breaks/second.
You can see the photodiode output is much more rounded. This would translate into a “softer” edge to the segments of the meteor image. This might actually be ok for slow meteor measurements but probably just for purely aesthetic effect (and, rather usefully, differentiation between satellites and meteors!), we’ll see…
(The “delta T” is given as 85ms between the cursors. So working backwards gives a drive frequency of 5.9Hz so I don’t exactly have the cursors one pulse apart.)
cheers,
Bill.
Just noticed, 2011, I need to reset my clock!!!
YUK! Hi hopes dashed! Much truth in the expression ” you get what you pay for”!
My ultra cheap LCD shutters arrived today. They work quite well at 5 Hz
By 10Hz things are going down hill.
I imagine they’d work after a fashion but the trail would not be as clean as the LCTec FOS.
At £2.95 for the 36mm square one and £4.95 for the 48mm x 98mm ( which is actually pretty big), not too expensive an experiment.
I’m going to mount the smaller one in front of a camera anyway and see how it goes. Be interesting to see a side by side comparison. All I need is some clear sky, that’s the big ask!
Cheers,
Bill.
Hi, I use the same basic method with my WATEC’s however when you dig into the numbers even 1/25 sec isn’t fast enough to get the required precision to determine decelerations for orbital corrections. Steve Evans’ paper from 20 years ago (!!!) out lines the requirements nicely. (JBAA Vol 108 4 1998 “Experiments in digital meteor astrometry”) His work then was with his rotating shutter system, which I have and am trying to reinstate, running with three blades giving a chopping interval of ~33.3ms that’s faster than 1/25 sec (40ms) and it still wasn’t enough. He ultimately was working with a 6 blade shutter to give ~16.7ms (Which is the one I’ve been given). Astrometrica is the program he mentions.
The costs are high but not prohibitively so compared to the camera’s your using. Even with the cost of a LCD shutter and function generator as they are at the moment is still ~tenth of a SONY A7SII and if you include include a cheap dslr and lens and you’ll get five systems for the money. Despite all of the limitations with meteor observing it’s all about sky coverage!
I’ve found a supplier of very cheap LCD shutters and have ordered a couple to experiment with. IF these work then it becomes extremely feasible to have a high speed optical chopper that may yield arcsec precision for less than £20 (if you build a function gen kit from ebay!)
The consumer technology is quite remarkable.
Hi,
The exposures were 27 secs at iso1600. 30mm f1.4. In short you can’t know. The chopping, in principle, is used to provide accurate meteor duration and precision astrometry allowing meteor velocity and decelerations to be measured. This in turn is used with other observations to produce better orbits. The previous owner of the mechanical system I’m trying to re-instate, the late Steve Evans, wrote a very interesting paper in the BAA journal on precision observations. One of the reasons his shutter system was designed to chop at 60 breaks/sec.
I’m having some trouble with vibrations so will need to re-evaluate my design. The advantage of the mechanical shutter is that it is working at 100% efficiency. The shutter blades completely block or not. The LCD shutters have both polarisation issues and the fact that when open are still ~30% opaque (thats ~0.6 of a stop). Any meteor needs to be that much brighter with a LCD cf mechanical.
Like everything with meteor astronomy it’s all a trade off!
cheers,
Bill.
Hi,
I couldn’t find her address as I was going to do just that. Could be the Flash issue, I tried other pages and they were fine too. If you have her address it might be worth dropping her a line just in case. Feel free to reference my experience. It’s THE most important piece of software I use!!!
cheers,
Bill.
Michael,
An update… After posting I decided to check the tutorial on the Visual Spec site. There is some sort of hack or virus or something going on. My laptop security went mental. Approach with caution…!
Bill.
Michael,
It’s easy enough to do but a pain to describe….
There are tutorials on the RSpec site (looks like that’s the package your using).
Also take a look on the Visual Spec site (http://astrosurf.com/vdesnoux/) , there’s a comprehensive tutorial using Vega. That’s the technique I use. I much prefer working with Visual Spec and IRIS. They don’t have the slick interface but I like the command line method, makes you think about what your doing.
cheers,
Bill.
Hi,
The 8/9 and 10/11 Aug 2018 provided some good results. 31 spectra over both nights. This is the best Perseid (so far, maybe it’ll be clear tonight… ;-))
)
Here is the instrument corrected spectrum graph.
Note: I’ve cropped the O and N lines from the atmosphere, in the near IR. I’ve also binned by 3 to smooth out the de-slanting artifacts but probably at the loss of some small lines (mostly Fe).
It’s always re-assuring to see similar results from other observers. However there are two lines (or maybe very close bands) that I have not been able to tie down. I’ve got these on lots of Perseids from the last several years. Not sure what the bumps are around the Na line…. Could be any of several but at this resolution it’s difficult to be absolutely certain.
I also got a small section of this same meteor on another system. Almost perfect dispersion too… Still to process that one.
cheers,
Bill.
