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Mmm, having tried a few comparisons and matching existing spectra I have no clue as to what this thing is!
I found some spectra of the Hyubusa 1 probe re-entry which actually had some similarities but were of much lower resolution.
Rather re-enforces my suspicion it might be space debris. However an allsky shot has been secured of what might be the same object. A nice bright greenish coloured fireball. So I’d wager most of these lines will be iron or magnesium, magnesium alloy’s are probably common in space frames I’d imagine.
Next plan is just a slog to try and match up library lines….
Cheers,
Bill.
Interesting watch.
Thanks for posting it Ronan.
The comment in the presentation that there were over 1000 people attending the BA meetings got me thinking. There were probably a lot more “gentlemen astronomers” from this era, viz Mr Birmingham, than maybe we realise!
The list of big scopes is revealing, “the biggest refractor in the world at the time”! How many amateurs can make a claim like that today!? ; – ))
Like Mr Birminghams’ work, all of this great effort has more than likely been lost forever, which is rather sad.
I really like the quote at the bottom of the last image, “… to excite simple admiration rather than scientific reflections”.
A wonderful reminder that we all need to take a step back from time to time.
As I don’t have her direct contact details I’d just like to let Ann D. (on the sales desk) know that the observing guide arrived safely.
Thanks!
Bill.
Indeed it was an excellent weekend! I was particularly delighted to meet up with the Armagh Observatory director Prof Michael Burton. Michael was my supervisor when I got my first student job at the Anglo Australian Observatory in 1991.
Where does the time go….!?
As you say, the evening sessions were most entertaining. I have no doubt that this is where the real meeting actually happens ; – ))
I’m looking forward to the next one….
cheers,
Bill.
Hi,
With running out of the stuff myself I had a look around the net at the various suppliers. Not that it makes much practical difference but it appears the film grating is sold as 1000 lines/mm (25400 lines/inch) or 500 lines/mm (12700 lines/inch).
I also found a supplier of 532 lines/mm crossed grating material which is an interesting product. In theory that should produce a useable spectrum no matter what angle the meteor fall across the FOV. However there is a BIG penalty in magnitude as the light per spectrum would now be divided into 8 spectra, four at right angles to each other and 4 fainter at 45 degrees. It’s probably more of a novelty laser pointer effect filter but….
I can feel some olde fashioned optical experiments coming along….
cheers,
Bill.
Hi,
Done some more work on the spectrum and the lines in the trail are coming out with a FWHM of around 1nm and the measured dispersion is 0.46nm/pix. It’s now just about where I want to be. It’s seeing how all the little lines behave that tells the story…
Cheers,
Bill.
Hi,
Thanks Jack.
It gets better….!
Whilst concentrating on the flare as it had so many lines I didn’t really pay attention to the bright pair that ran close to the bottom of the image and through the camera ID text.
Taking a closer look revealed something remarkable. Since I started regular meteor spectroscopy around 2007 I’ve had the rather arbitrary goal of getting to a system that would resolve the bright green Mg triplet ~517nm. It’s tough to do completely!
When I chopped up the image and fitted the lines, it turns out that the “pair” is actually a partial resolution of the triplet! The 516.73nm and 517.27nm are just too close for this lens/grating/seeing combo but at the 1nm FWHM and 0.46nm/pix level it is just enough to see the 518.36nm line as separate, just over 1nm (2 pixels) between them. Here’s a plot with the brighter lines identified.
Well pleased with that!
Cheers,
Bill.
ah ha, I knew I had a picture of the triplet some where….
The power of spectroscopy, the same elements but on the sun (in absorption, not in emission as in a meteor spectrum!) I took this with a home made solar spectroscope, donkey’s years ago, it shows the main Mg lines plus a ton of Fe, Cr and Ti lines. These’ll be hiding in the meteor spectrum too!
Cheers,
Bill.
Hi,
The set up has always been, more or less…, the same. Stick a grating in front of your lens and see how it goes!
The plastic grating film now seems to be sold all over the place. The stuff I currently use I bought from Edmond Optics in 2009, £6.99 plus shipping etc. This was the second batch. The first was from the early 90’s. Trying searching for “holographic plastic grating film” or similar combination. Again, the stuff I bought, of US origin was sold in 12 inch x 6 inch sheets with either 12500 or 25000 lines per inch. I use the 12500 version which is just under 500 lines/mm.
It’s on Amazon and ebay as effect filter, novelty pattern filter, rainbow generator etc etc. You can even buy a 200 foot roll if you want to!
I should caution that TWO results (this and one other spoardic of almost the same magnitude) might not represent a statistically significant sample but with a bright enough meteor the plastic film seems to have a better throughput at the blue end of the spectrum than my much more costly glass gratings. Given the spec of the glass gratings this seriously surprises me! So I have now come to the conclusion that it’s a much more cost effective way to start should anyone wish to give meteor spectroscopy a go. I think this is pretty much old hat now as lots of stuff is online about it. I gave up on it when I ultimately stopped trying film based photographic spectroscopy which yielded precisely zero over 15 years prior to me using video. I decided to try it out again for financial reasons.
Due to the embossing process the grating is not blazed so equal amounts of light go into the spectrum on each side and because it’s a simple sinusoidal embossing the spectral throughput, overall, is less than a good glass replica. The upshot is you need brighter meteors to produce a spectrum all else being equal. Effectively you get half the light in your spectrum but at 1/20 the cost of a proper grating. It’s up to the prospective observer to decide whether that’s a reasonable cost/benefit analysis.
I used to have quite a bit of the stuff as I bought several sheets at the time but I have given it all away in little bits and pieces to those who wanted some to experiment with. At seven quid, cheaper from ebay, I don’t know if it’s exactly the same stuff though, it’s not going to break the bank.
Bit of a ramble but I hope it helps….
Bill.
Exactly!, whilst I tried to resist I couldn’t help it given the subject…
Without being overly crude, in youthspeak… I LMFAO ; – ))
Hi,
Phaeton (3200) is indeed interesting. After reading a paper by Rendtel and Ryabova (I’ll dig up the full reference….) which mentioned that we might encounter very recently emitted particles during the Geminids in 2017, I hoped to pick up some significant differences in their spectra. Particularly an excess of sodium. But despite catching 7 good spectra nothing seemed out of the ordinary.
I’m looking forward to what Destiny will reveal….
cheers,
Bill.
Your wish is my command… 😉
First is across the third “chop” back from the terminal flare.
Second is across the terminal flare. Ca+ saturated but lot’s of metal lines light up. At least 35 lines (maybe a couple more) including the usual Mg, Ca and Fe but also Cr and Mn as well as possibly Ni.
Despite it’s low efficiency, due to it’s embossed profile, I’m really surprised (and pleased) with the performance of the plastic film. I’m becoming convinced that it does have slightly better properties in the UV/Blue compared to the expensive glass gratings.The results are evidence enough I think…
R is around 1000, not bad for such a basic transmission set up.
Going to leave a couple of glass ones on but change the rest to plastic and see how it goes over the next season.
The weather gods certainly gave me a break last night but I think we’re in for more heavy showers tonight….
Cheers,
Bill.
Hi,
Will do, I’m planning on positioning the cameras where we’ve had detection’s before. Even with the bigger chip, using the 25mm lenses gives a slightly smaller FOV than the 12mm’s on the WATEC’s. I’ve got some 12.5mm lenses that will fully illuminate the ZWO chip but there is a magnitude penalty. I might try one of each, as the lenses use the same hood thread sizes so the gratings are effectively interchangeable.
Positive thought…. it WILL be clear on Monday night!
cheers,
Bill.
Hi,
I cut out some disc’s of plastic grating film and mounted them in little cardboard holders last night. So the system is now good to go. I’m hoping the weather will co-operate so I can get at least one spectrum (of anything…!).
I received an email from Derek with his first spectrum. Taken through this grating film and looking at his results, as with mine, either the meteor was very “blue” or the grating film has indeed better performance in the blue compared to the glass gratings I have used previously.
We’ll see…
cheers,
Bill.
Hi,
Thanks, with a bit of processing the ZWO174’s are decent performers. However your question is a VERY good one.
The issue is with the drivers. The response I’ve had from some of my Japanese friends is that they are surprised I could get it to work with UFOHD at all! I’m no expert in this field but from what I gather it is to do with the way UFO uses Directshow.
ZWO have continuously updated their camera drivers so something has changed to get it to work. Another issue seems to be the way the USB works. No matter what I do I cannot get the USB3 connection to work without dropped frames and crashing regularly and I can’t set the frame rate. But, and it seems odd to me, if I use an USB2 connection it works absolutely fine but you’re stuck with whatever the pc can crunch through. The global shutter places a high demand on the computer as it’s a lot of pixels to shunt around.
In my setup the native camera driver is running at 17.1fps with 50ms exposures on USB2 (3.3GHz quad cores) BUT UFOHD thinks it’s seeing 25fps… For detection, as you say, it is indeed fine when it’s just the spectrum your after but I think this may affect the velocity determinations and thus everything else downstream orbitwise.
So I would say probably not, but I’m not really sure how it’s actually working and I’ve never tried it so I can’t say for sure…
Cheers,
Bill.
Hi Derek,
Thanks, Having tried film based spectroscopy for some 15 years I know the difficulties. I never captured a single one!
I was glad to help, it has been an interesting challenge. It always feels good when you finally see it come together and you actually understand what you’re looking at!
Great fun,
Cheers,
Bill.
PS. Will you be attending the BAA weekend in September at Armagh, or perhaps the IMC again, in Germany this year. Looking forward to catching up with you at some point.
Hi,
I was sent Henry Soper’s remaining original material a while back but I’ve never seen any of Harold’s. It’s quite fascinating to see the differences between the film results and current video systems.
cheers,
Bill.
PS, Had to check. Yes, one of Harold’s photographs is in Neil Bones’ book. I knew I had seen one recently. Do you know what happened to his originals?
I have scanned the ones from Henry, ultimately I’ll send them to the BAA for archiving.
Hi,
Since I may well have done the same thing, (but realised what was going on and am sticking to that story), I’m keeping it a secret to save their blushes… ;-))
cheers,
Bill.
Hi,
Well, as I said, all things being equal…
You can see the curvature on the image and if it was this small discrepancy then that’s more lazy than I am! As long as there is no point of inflection along the dispersion then the spectrum can be corrected on the fly provided a few bright lines can be identified.
I’ve tried the method that C. Buil described using images of grids for distortion correction but it’s frankly not worth the trouble at your average meteor spectrum resolution.
Cheers,
Bill.
