Mile 108 Viewing Conditions
Mile 108 Elementary School
Located on Highway 97 in the British Columbia Cariboo-Chilcotin area, Mile 108 Elementary School is the site of the second AllSky camera located in School District #27 (Cariboo-Chilcotin). This camera will provide overlapping coverage with cameras in Prince George, Tatla Lake, Kelowna, Penticton, and Osoyoos, thereby increasing the likelihood of a multiple site common capture.
meteor detection on UT 2010 Sept.11
11h 30m 04s
SNOTEL An Alternative to TV Video Carriers
For forward scatter observers the SNOTEL Meteor burst system can be a viable substitute of RF when the Canadian analog TV stations are phased out. Currently this phaseout is scheduled for sometime in 2011. The US stations have already made the jump form analog to digital.
SNOTEL, is an acronym for Snowpack Telemetry. It began operation in the 1970’s and is run by the Natural Resources Conservation Service (NRCS). For complete description of the system visit the general information page at the home site at:
A quick search of the net will also bring up many hits on this system.
For our purpose we are not interested with the remote slave stations, rather we want to listen for the RF reflected from meteors from the two master stations transmitters. The stations are located near Boise, Idaho and Ogden, Utah and operate on a frequency of 40.530 MHz and run at a power of about 1,500 watts. Two types of encoding are used, a 90 degree FSK for the first ~ 10 seconds of each minute then a 30 degrees FSK for the rest of the minute.
Listen to SNOTEL signal recorded from West Kelowna during intense Es on 2009-06-23 1648 UT. During none sporadic periods expect to hear only brief pings from under dense echoes. Both SNOTEL stations put in strong echoes in southern British Columbia.
More details to come.
Dominion Astrophysical Observatory
Dave Balam will be editing this page soon. In the mean time he sent some images representing the current all-sky time lapse camera at the DAO. A Sentinel unit will be added once Sid is available to install it.
Dave does have some images that show the capabilities of their current all-sky camera. The camera is on line an updated every minute at:
A mosaic_2009_10_24 – an 8 hour stretch (1 hour per individual stack) of the sky on 2009 Oct. 24/25. The objects marked with blue boxes are meteor trails.
Image: meteor_100217 – a meteor trail seen through the clouds before dawn on 2010 Feb 17.
Image: meteor_2009_10_25_01_24_13 – a bright meteor trail from 2009 Oct. 25
More to come in the weeks to follow.
2009 09 24 Kelowna-Yarrow Fireball
On the morning of the 24th of September I (Jeff) reported the following event to the BCMN list:
It occurred on September 24, at 09:56 UT which puts it at 02:56 PDT. It was very low on my SSW horizon. It was very slow moving with several bursts.
I then wrote Alan Hildebrand, and sent on the same information and asked him if he had any reports other than mine. He said not yet. I then sent him the movie of the bolide, a composite still picture of it and a light curve of the event. It seems most of my fireballs are low on my horizon so not that spectacular looking compared to a near zenith event.
Here is the light output graph; the total amplitude is the summation of all pixels above the triggering threshold.
Ken Tapping, who would have a better view of it since his camera is south of mine reported back that he could not check his camera because he is out of town. No one else in our group recorded it. The terminal burst looked like it might have had a chance to be recorded by infrasound. I inquired Kris Walker and asked it was heard on the USArray infrasound array. He replied it had not.
Alan reported the fireball to the MIAC group and noted on human visual sighting from a person in Yarrow (west of Chilliwack), B.C. The report stated:
time: 02:50:00 am
location: Just an estimate. It appeared to have landed in this mountain range.
flares: White ball with a colored centre. Large stadium sized bright dome of light on impact
train: Yes, 0.5 sec
Note: The data folder is in the video data download category for West Kelowna/Sandia/2009_09
Sentinel Magnitude light output file
I asked Joe Chavez at Sandia National Labs what was contained in the single text file Sentinel outputs from the external video grabber.
It has this basic format:
From the Bolide of March 23, 2008
Event time: Sat 2008/03/22 04:26:41.04
-30 0 0 156.8 338.0
-29 0 0 156.8 338.0
-28 0 0 156.8 338.0
—- SNIP —-
233 1602 36538 226.4 329.6
234 1595 34884 225.4 330.2
235 1574 33285 224.5 330.7
236 1581 31824 223.6 331.3
237 1539 30273 222.5 331.9
238 1577 28940 221.4 332.3
239 1557 27557 220.3 332.8
240 1582 26090 218.9 332.9
241 1592 23868 217.2 333.3
242 1636 23007 215.7 333.3
243 1685 21843 214.1 333.4
244 1702 21038 212.6 333.6
245 1708 19880 211.1 333.6
246 1760 18637 209.6 333.6
—- SNIP —-
299 6 0 164.1 342.0
300 9 0 164.1 342.0
301 3 0 164.1 342.0
Joe informed me:
The first column shows frame counts, so each row represents about 1/30th of a second. The recording begins 30 frames (one second) before the system is triggered. The time stamp corresponds to the trigger time.
The second column shows the number of pixels that were above the threshold value.
The third column is a measure of the total amplitude and is computed by summing all pixel values above threshold. Since this value may change depending on what hardware you use, you will need to calibrate it against a known light source. We have done this by uncovering the shadow of the full moon over the sentinel camera and recording the amplitude response of the sentinel event. If you measure the amplitude response of the full moon to be XM, you can calculate the magnitude of any event of amplitude X with following formula:
Magnitude = -12.6 – 2.5 * log10( X / XM )
This assumes that the magnitude of the full moon is –12.6
The fourth column lists the X coordinate of the centroid of the event, in pixel units.
The fifth column lists the Y coordinate of the centroid of the event, in pixel units.
I have a request in to find out if the new WSentinel (internal video card) light data file uses the same equation for magnitude estimates.
Update: September 04, 2010 17:42:24
Dick Spalding responded to my WSentinel inquiry:
Regarding your magnitude question, I think the scaling for the new video card system should be the same as for the Sentinel box systems. However, you should be aware that for very bright events, the camera’s auto-iris feature will begin to reduce lens aperture, thus reducing the apparent brightness of the event. I don’t believe the full Moon causes the iris to be reduced, since planet brightness seems to be the same with or without the full Moon present. Iris control is based on total light on the camera’s CCD chip. So, a bright nearby light could potentially affect sensitivity by partially closing the iris.
Also, these HiCam HB-710E cameras have a built-in automatic gain control (AGC), which increases electronic gain as the scene becomes darker. For the typical dark sky, the gain is at the maximum permitted by the screwdriver AGC setting on the camera back. Turning that setting to its maximum clockwise position gives the camera maximum sensitivity. However, the resulting electronic noise produces an image with lots of “snow”, which forces trigger thresholds to be set higher. Cameras that we ship usually have their AGC control backed off to a level that puts the snow below the default trigger threshold. At that setting, I don’t think the presence of the full Moon causes the electronic gain to be reduced. Whether that’s true could be tested by lowering the threshold until random triggering on the snow begins to occur on a dark sky, then repeating with the full Moon in view. I have not done that test.
Meteor Spectroscopy and the Amateur
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. Because of the short duration of meteor phenomenon this was difficult but it was established that meteors produce discrete line spectra. The bright lines neutral sodium and neutral magnesium where correctly identified visually by experienced observers.
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. 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. Canadian astronomer Peter M. Millman while getting his Ph.D. at Harvard was asked to look at the meteor spectra secured thus far. This resulted in two papers, the first can be down loaded at: http://adsabs.harvard.edu/abs/1937AnHar..82..113M and the second at: http://adsabs.harvard.edu/abs/1937AnHar..82..149M Peter Millman made meteor spectroscopy a life long interest and was considered a World Authority in this field.
From 1897 to 1958 the total number of known meteor spectra secured was only 318. 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. Most were obtained using objective prisms but in the latter part of the 1950’s transmission diffraction gratings were introduced to obtain spectra. 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.
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. Few took up this challenge because of the difficulty in securing a meteor spectrum. 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. During this period conventional cameras fitted with a dispersive element, a grating or prism were used. 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.
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. The latter also used radar detection systems to study meteors in conjunction with photographic and visual observations. Sadly these programs were shut down as a result of budget cuts by the federal government. Ondrejov Observatory in the now Czech Republic became the centre to carry on this work. Others have since taken up the challenge mostly in the USA, England, Spain, and Russia.
As mentioned before it was only possible to obtain the spectra of meteors brighter than -2.0 magnitude. 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. These cameras were capable of producing spectra as faint as +1.0 magnitude or so. This effort produced 746 photographic meteor spectra during the four years they were in operation. The results of this was published in various journals including Sky & Telescope magazine and IAU Symposium publications.
Also during this time, TV systems were being experimented with increasing the faint magnitude capability down to around +3 visual magnitude. 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.
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. He can be contacted at firstname.lastname@example.org if your interested in doing this.
I personally use second generation image intensifier systems to record faint meteor spectra. 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. Now they are difficult to obtain from U.S. sellers as you have to apply for an export permit. Sometimes they are available outside of the U.S.A. so I scan eBay looking for them. 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. You just take your chances buying a surplus intensifier and hope it will work. Non U.S. made intensifies are also made by other countries, Russia, China, etc. so all is not lost. 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. 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.
I once asked Canadian meteor astronomer Ian Halliday if this was still considered worth doing. He said yes, but noted that the utility of running a meteor spectroscopy program for an individual can be difficult. 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. One must obtain a very good spectrum from these showers to get a professional interested in measuring your spectrum. One can of course attempt to measure your spectra yourself as there are computer programs available that are made for this purpose. Unlike stellar spectra most meteor spectra have relatively low dispersion so identifying a line can be difficult. In some cases you must have the experience in knowing the most probable line that should be present in that region. 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.
There are other issues to deal with also such as distortions produced by the lenses you use. 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. 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. I was lucky enough to find a surplus large reflection grating that should work using the method employed by the BAA member Mr. Aires. A reference for his BAA Journal paper can be found elsewhere on this web site. I still need to build the camera and find a source of inexpensive Tri-X or Ilford HP-5 – 8X10 film. No luck so far.
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. One can then study the height of where certain spectral lines become visible or fade out. One should also use chopping shutter to arrive at the velocity and also the spectrum of the meteor train between the shutter breaks. 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. 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. That is, until I get others in this network interested in doing meteor spectroscopy.
We could even accomplish a first, getting the spectrum of a meteor dropping fireball and recovering the meteorite. This would answer many questions about the presents and formation of spectral lines by comparing it to the analysis of an actual recovered meteorite. One can always dream! 😉
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! 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. If you do this, the direction of the meteor flight path is less important. Attached is their digital camera spectrum. They deserve congratulations! One feature is incorrectly identified as Cr at 427.4 nm. Jiri Borovicka says this is probably an Fe iron line. This spectrum is also unique as it’s in colour. B&W is preferred as this simplifies photometry intensity scans as this is established for B&W films. Jiri says this can be done with colour film also but is more complex to do.
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. Hope some of you take up the challenge!
POLISH FIREBALL SPECTRUM from http://www.pkim.org/ (In Polish)
Other papers on the calibration of an all sky lens
Here are more papers on all-sky lens calibration:
A new positional astrometric method for all-sky cameras.
This link will take you to the SAO/NASA ADS Astronomy Abstract Service where you can download the pdf. Below the abstract select Printing Options and then Print Whole Paper. Next press the send pdf button. A download of the pdf will follow.
Segon, Darmir, (2009) How many stars are needed for a good camera calibration? WGN 37:3, pp. 80-83.
Houghton, John (2008) Lens Calibration Using the Stars. Web page.
Ed Majden’s Observatory
Courtenay, BC, CANADA
Lat: 49 deg 40′ 36.4″ N – Long: 125 deg 00′ 36.2″ W
This observatory was built with the help of friends over several years. It is a work in progress. The dome is home built, made of plywood arcs cut from 3/4″ plywood and covered with tempered masonite and then painted with neoprene sundeck coat for weather protection. Several volunteers aided in this effort but Geoff Culliton deserves a mention along with my brother-in-law Lyle Wade and friend, Frank Davis. At present it has just undergone a major refit thanks to the efforts of a good friend and colleague John Purdy. His photo is included below doing roof repairs on the building proper. John has also made special accessories for the various instruments, as he is a talented hobby machinist and amateur astronomer. Most of my colleagues are ex or retired R.C.A.F./C.A.F. veterans!
DOME CONSTRUCTION DETAILS
Dome skeleton made from 3/4 inch plywood arc sections.
Geoff Culliton screwing down dome gore sections.
John Purdy working on roof repairs.
A Sandia Bolide Detection Camera was installed on the roof thanks to Richard Spalding of Sandia Labs in the United States. This is part of a West Coast Fireball Tracking Network overseen by Dr. Jeremy Tatum, retired Professor of Physics and Astronomy at the University of Victoria. Dr. Tatum asked me to be the unofficial coordinator of this West Coast Network. He still assists with the technical work of triangulating fireballs captured by these All-sky Cameras. A picture of one of the Convex Sandia All-Sky Cameras is shown below. It operates 24 hours per day recording on 8-hour vhs tapes. A new auto recording computer capture fisheye camera is also being installed at this site. Sandia Labs in the U.S.A also provided this system. It will detect moving objects and dump the images to a PC computer hard drive. It uses a special interface box designed at Sandia Labs including a software package called Sentinel installed under the Linux operating system.
Above – Washington State fireball detection near the SE horizon! North is to the right with East at the bottom. A final joint research paper is in progress. No meteorite as yet has been found. The fireball is the bright flare at the horizon. This is a single frame capture.
Convex type Sandia All-Sky Bolide Detection Camera.
One of the main areas of research conducted at this Observatory is Meteor Spectroscopy. This work is described elsewhere on this web page.
The main observatory at present houses a Celestron C14 S.C.T. Auxiliary equipment includes an Optec SSP-3 solid state Photometer and an SBig ST-6 CCD Camera. A Celestron 8 inch Schmidt Camera will soon be added on the telescope mount for wide field photography.
One of the big problems today is light pollution. A problem most astronomers have to contend with today.