Written by Ed Majden<\/p>\n
First a bit of history.<\/p>\n
In the second half of the 1800’s attempts were made to observe meteor spectra visually using prisms.\u00a0 Because of the short duration of meteor phenomenon this was difficult but it was established that meteors produce discrete line spectra.\u00a0 The bright lines neutral sodium and neutral magnesium where correctly identified visually by experienced observers.<\/p>\n
The first photographic meteor spectrum was secured by chance during a routine stellar spectroscopy program by Pickering in 1897 at Harvard. S. N. Blazhko in Russia set up the first successful photographic program in 1904 – 1907.\u00a0 This pioneer program yielded the spectra of three bright meteors. Up until 1931 only 11 meteor spectra had been secured, mostly by chance, except for the tree obtained by Blazhko.\u00a0 Canadian astronomer Peter M. Millman while getting his Ph.D. at Harvard was asked to look at the meteor spectra secured thus far.\u00a0 This resulted in two papers, the first can be down loaded at:\u00a0 http:\/\/adsabs.harvard.edu\/abs\/1937AnHar..82..113M<\/a> and the second at:\u00a0 http:\/\/adsabs.harvard.edu\/abs\/1937AnHar..82..149M<\/a> Peter Millman made meteor spectroscopy a life long interest and was considered a World Authority in this field.<\/p>\n From 1897 to 1958 the total number of known meteor spectra secured was only 318.\u00a0 This was partly due to the few people engaged in this field and also because it was only possible to obtain spectra of meteors brighter than -2.0 magnitude and brighter with conventional cameras and films available at this time.\u00a0 Most were obtained using objective prisms but in the latter part of the 1950’s transmission diffraction gratings were introduced to obtain spectra.\u00a0 This was a great improvement as gratings produce near linear dispersion spectra unlike prisms which have good dispersion at the blue end but crowded dispersion at the red end making line identifications more difficult.<\/p>\n Dr. Millman encourage amateurs to get involved in this field and he published a paper promoting this, Amateur Telescope Making – Book Two, Scientific American included this paper, Meteor Photography.\u00a0 Few took up this challenge because of the difficulty in securing a meteor spectrum.\u00a0 The technique is simple but one cannot predict where a meteor bright enough to produce a spectrum crosses the camera field of view in the correct direction so some got discouraged and did not continue trying.\u00a0 During this period conventional cameras fitted with a dispersive element, a grating or prism were used.\u00a0 At the end of WW11 good quality aero cameras hit the surplus markets at very reasonable cost and these were adopted for use as meteor spectrographs.<\/p>\n Millman, and later with Ian Halliday and others established the Meanook\/Newbrook Meteor Observatories in Alberta and later the Spring Hill Meteor Observatory near Ottawa.\u00a0 The latter also used radar detection systems to study meteors in conjunction with photographic and visual observations.\u00a0 Sadly these programs were shut down as a result of budget cuts by the federal government.\u00a0 Ondrejov Observatory in the now Czech Republic became the centre to carry on this work.\u00a0 Others have since taken up the challenge mostly in the USA, England, Spain, and Russia.<\/p>\n As mentioned before it was only possible to obtain the spectra of meteors brighter than -2.0 magnitude.\u00a0 Hi speed cameras like the large aperture Maksutov Cameras were introduced by Gale A. Harvey NASA\/LRC, in the late 1960’s and and 1970’s.\u00a0 These cameras were capable of producing spectra as faint as +1.0 magnitude or so.\u00a0 This effort produced 746 photographic meteor spectra during the four years they were in operation.\u00a0 The results of this was published in various journals including Sky & Telescope magazine and IAU Symposium publications.<\/p>\n Also during this time, TV systems were being experimented with increasing the faint magnitude capability down to around +3 visual magnitude.\u00a0 A paper on this, Spectroscopy of Perseid Meteors with an Image Orthicon by Peter M. Millman, A.F. Cook and C.L. Hemenway was published, refr. NRCC No. 11822 and I believe also in Sky & Telescope.<\/p>\n Since this time military night vision devices using image intensifiers became available and have been adopted by both professionals and some amateurs to obtain and record faint meteors and also meteor spectroscopy. Sirko Molau from the IMO runs a direct meteor recording program using image intensifiers systems and also faint lux security type cameras with fast lenses for his programs.\u00a0 He can be contacted at sirko@molau.de if your interested in doing this.<\/p>\n I personally use second generation image intensifier systems to record faint meteor spectra.\u00a0 As a Canadian I was lucky enough to buy a surplus 2nd Generation 25mm Image Intensifier, type MX9944\/UV, before the U.S. government put export restrictions on these devices after 9\/11.\u00a0 Now they are difficult to obtain from U.S. sellers as you have to apply for an export permit.\u00a0 Sometimes they are available outside of the U.S.A. so I scan eBay looking for them.\u00a0 New ones are probably too expensive for an amateur’s budget so one hopes that a surplus one still has some life left in it.\u00a0 You just take your chances buying a surplus intensifier and hope it will work.\u00a0 Non U.S. made intensifies are also made by other countries, Russia, China, etc.\u00a0 so all is not lost.\u00a0 I recently bought a XX1335\/Q image intensifier from a British surplus dealer which is nice for meteor spectra as it has a 50mm diameter input screen which will accommodate higher dispersion spectra.\u00a0 I would love to get a 3rd Generation 25 mm ITT Intensifier as these have a longer life but alas the U.S. export restriction is in effect.<\/p>\n I once asked Canadian meteor astronomer Ian Halliday if this was still considered worth doing.\u00a0 He said yes, but noted that the utility of running a meteor spectroscopy program for an individual can be difficult.\u00a0 Conventional photographic meteor cameras require about 100 hours of exposure time to secure one spectrum. That’s a lot of film! One can of course concentrate your efforts during major meteor showers like the Perseids or Geminids to increase your chance of success.\u00a0 One must obtain a very good spectrum from these showers to get a professional interested in measuring your spectrum.\u00a0 One can of course attempt to measure your spectra yourself as there are computer programs available that are made for this purpose.\u00a0 Unlike stellar spectra most meteor spectra have relatively low dispersion so identifying a line can be difficult.\u00a0 In some cases you must have the experience in knowing the most probable line that should be present in that region.\u00a0 I once tried a program and had Jiri Borovicka at Ondrejov measure the same spectrum and nearly 1\/2 the lines I had identified were not the correct ones even though the computer program said they were correct.<\/p>\n There are other issues to deal with also such as distortions produced by the lenses you use.\u00a0 It is very desirable to get a high dispersion spectrum but this requires a long focus lens a large grating and large format film, at least 4X5, 8X10 even better but the cost goes up exponentially.\u00a0 I would love to find a large grating for a Kodak F-2.5 – 12 inch focal length lens and use 8X10 film but alas, this costs money.\u00a0 I was lucky enough to find a surplus large reflection grating that should work using the method employed by the BAA member Mr. Aires.\u00a0 A reference for his BAA Journal paper can be found elsewhere on this web site.\u00a0 I still need to build the camera and find a source of inexpensive\u00a0 Tri-X or Ilford HP-5 – 8X10 film.\u00a0 No luck so far.<\/p>\n When doing spectroscopy one should try and work with another person situated 50 or so km away so heights of the start and end point can be arrived at.\u00a0 One can then study the height of where certain spectral lines become visible or fade out.\u00a0 One should also use\u00a0 chopping shutter to arrive at the velocity and also the spectrum of the meteor train between the shutter breaks.\u00a0 This also allows longer exposures as it takes longer for sky fog to build up on the film as it is exposed to the sky for 1\/2 the time.\u00a0 Our fireball camera network is very useful as it can provide height and velocity of your meteor spectrum if your doing this on your own as I’m doing.\u00a0 That is, until I\u00a0 get others in this network interested in doing meteor spectroscopy.<\/p>\n We could even accomplish a first, getting the spectrum of a meteor dropping fireball and recovering the meteorite.\u00a0 This would answer many questions about the presents and formation of spectral lines by comparing it to the analysis of an actual recovered meteorite.\u00a0 One can always dream!\u00a0 \ud83d\ude09<\/p>\n Too bad on can’t get a large format ccd detector for meteor spectra but robbing a bank to pay for one is probably not a good idea!\u00a0 A Polish fireball group did have a nice success using a Canon 20D digital camera using crossed thin film gratings, a first by the way, using crossed gratings.\u00a0 If you do this, the direction of the meteor flight path is less important.\u00a0 Attached is their digital camera spectrum.\u00a0 They deserve congratulations!\u00a0 One feature is incorrectly identified as Cr at 427.4 nm.\u00a0 Jiri Borovicka says this is probably an Fe iron line.\u00a0 This spectrum is also unique as it’s in colour.\u00a0 B&W is preferred as this simplifies photometry intensity scans as this is established for B&W films.\u00a0 Jiri says this can be done with colour film also but is more complex to do.<\/p>\n I will try and answer any questions on meteor spectroscopy and if I can’t I will ask my friend Jiri Borovicka for an answer.\u00a0 Hope some of you take up the challenge!<\/p>\n Ed Majden<\/p>\n POLISH FIREBALL SPECTRUM\u00a0 from\u00a0 http:\/\/www.pkim.org\/ <\/a> (In Polish)<\/p>\n<\/p>\n \u00a0<\/p>\n","protected":false},"excerpt":{"rendered":" Written by Ed Majden First a bit of history. In the second half of the 1800’s attempts were made to observe meteor spectra visually using prisms.\u00a0 Because of the short duration of meteor phenomenon this was difficult but it was established that meteors produce discrete line spectra.\u00a0 The bright lines neutral sodium and neutral magnesium … Continue reading “Meteor Spectroscopy and the Amateur”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":362,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[],"class_list":["post-363","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-spectroscopy-methods"],"_links":{"self":[{"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/posts\/363","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=363"}],"version-history":[{"count":0,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/posts\/363\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=\/wp\/v2\/media\/362"}],"wp:attachment":[{"href":"https:\/\/bcmeteors.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=363"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=363"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bcmeteors.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=363"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}