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.

Composite:

 

Here is the light output graph; the total amplitude is the summation of all pixels above the triggering threshold.

Light Graph of the bolide

 

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:

Yarrow BC
V2R 5C5
phone_home: 604-328-2864
date: 24/09/09
time: 02:50:00 am
cloud: none
latitude: 49.04585724220807
location: Just an estimate. It appeared to have landed in this mountain range.
longitude: -122.05484390258789
duration: 3
speed: Fast
flares: White ball with a colored centre. Large stadium sized bright dome of light on impact
colour: White
train: Yes, 0.5 sec
sound: Sharp
stime: 2

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:

Jeff,

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.

Dick Spalding

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.

 


 

 

 

 

Sentinel Camera Calibration

In December of 2008, after a series of back of the envelope type discussions on how to calibrate a Sentinel camera, Ken formalized the discussions in a pdf. To see Ken’s method Click here for Ken’s original paper on how we can calibrate the Sentinel camera.

As a footnote I (Jeff) did a work through with my camera system. After the spreadsheet was made and a small Python program run Ken took my results and plotted it to see how his model stood up. Here are those results.

 

Hi Jeff,

I could not resist having a quick look. Your data is lovely. I simply plotted

R = sqrt((x-x0)2+(y-y0)2)

against zenith angle.

In the first plot I assumed the camera zenith was (371,240), and in the second I optimized it, and got (370,231). This of course would be the camera zenith not the centre of the frame.

HOWEVER: Look at the nice clean plot and good correlation. I think you can use the camera zenith method and ignore trying to find the centre of the frame; they are obviously very close because the plot, including the very slight nonlinearity due to the fisheye effect, integrates so cleanly.

The very slight fisheye effect can be approximated more than adequately by a 2nd-order polynomial, as Martin Connors said it would.

I would say, for your system, you should be able to simply calculate R and use the equation to get the zenith angle, and then do a rotation to find the azimuth error…. job done.

Regards,

Ken

 

 

2009 11 08 Prince George Fireball

On November 8, 2009, Wayne, at RDL Observatory, reported a capture of a bright fireball to our network. He told us:

“All
Late night capture, direction of travel westward. Event seen at Telkwa BC. UFO analyzer places impact area some where in the Terrace / Telkwa area but calibration of ufo analyzer is uncertain.  Witness at Telkwa said phosphor like drops falling between him and hill 1 mile to his north.  No Sound heard. enjoy
wayne”

Wayne sent a movie of the event to the BCMN group. You can view it here:

 

Upon receipt of Wayne’s report Brower wrote Alan Hildebrand, Coordinator of the Canadian Fireball Reporting Centre, and asked if he was getting any additional reports of the event. He said he had not heard of the event.

In between e-mails Hildebrand checked back in his mail and found the alert Wayne had sent earlier. (It’s always  good to follow up if you don’t hear back).

CBC carried and article the next day. You can view the article by clicking here.

On November 9th Hidlebrand (personal communication to Brower) summarized to the MIAC group. The fireball was:

  1. Seen widely.
  2. It caused explosive booms and cast ground shadows.
  3. He estimated the fireball to be in the  -17 to -18 magnitude range.
  4. Estimate ‘conservatively in 100 kg to 1 tonne order of magnitude’.
  5. Had an east to west motion (and apparently some south to north and at least modestly steep) which would be reasonable for prefall orbits.
  6. Was probably a meteorite dropper.

No other BCMN camera recorded the fireball.

 

Sentinel III system in photos

The Camera and Housing

The housing for the camera, the anti-dew heater, the thermostat, and fan are all housed inside a PVC tube and toilet flange.
As packed for shipping. Stands approximately 0.5 meter tall.

Top shipping end removed reveals the camera and baffle.

Top Baffle

The Rainbow L163VDC4P fisheye lens mounted on the camera body. Note the PVC stiffener rods with coax cable running through it..

fisheye lens

Student UFO2 User Guide

The Sonotaco.com site provides you with the latest capture and analysis software. The basic requirements are:

1) UFOCaptureV2 V2.22 to capture the data. Registration of this program is required after 30 days and the cost is 18900 Japanese Yen. Use this currency converter to determine the cost in your currency. You’ll also need the Users Manual. It is offered in an html and zipped format.

2) UFOAnalyzer V2 V2.28 to analyze the data. This is a free program. Provided in a pdf and zipped format, the Users Manual is essential to understanding this program. If you are a BC camera operator, download and install the Map of Canada (West) file. Scroll down to the bottom of the page to locate it. Extract the file to the UA2 root directory.

3) UFOOrbitV2 V2.25 to determine the meteor’s orbit. This is a free program. The Users Manual for this utility is offered in a pdf and zipped format.

The BBS Forum is also a good source of user information. You don’t need to speak or read Japanese 🙂


For those people that simply want to analyze the data, follow steps 2 and 3, and then do the following:

4) Download the contents of the UProfiles for UFO2 operators folder found in the Data Downloads/Video Data Downloads section and install the contents into the PROF folder of UA2.

5) To analyze individual captures, select a file found in the Data Downloads/Video Data Downloads section from any of the observatories using UFO2. At the moment, they are RASCPG, RDL, Shane, and Tatla. Download and extract the files into your directory. How you set up your directory is up to you. Use UA2 to analyze the data and plot a ground map.

6) To analyze common captures, you will download and analyze the files from Data Downloads/Video Data Downloads/Common Captures individually (don’t forget to select the profile for the site you are working with)…but you will perform one final step involving the use of Paint.NET. You will have saved the UA2 ground map from each site analysis. Using the Paint.NET tutorial, overlay the ground maps to determine the intersecting point.

7) When you have determined the intersecting point, email your results for confirmation to the administrator of this site. Your files will include the .XML and ground map files for each of the sites you worked with, as well as the overlay map from Paint.NET. Once your data is confirmed with other site users, it will be posted in the Video Results and Papers section and forwarded on to the Coordinator of the Canadian Fireball Reporting Centre at the University of Calgary.