Fw: (meteorobs) Bright Fireball over Alberta Dec. 18

[Bruce McCurdy]

>From Mike Noble in answer to GeoZay's question. 

Bruce
*****

----- Original Message ----- 
From: "Noble, Mike" <MNoble at NRCan.gc.ca>
To: "Bruce McCurdy" <bmccurdy at telusplanet.net>; <GeoZay at aol.com>
Sent: Sunday, December 24, 2006 2:57 PM
Subject: RE: (meteorobs) Bright Fireball over Alberta Dec. 18


Hi Bruce,
To answer GeoZay's query, no I didn't hear any boom, but I'm at fault
for not waiting longer and listening for one.

Here's the sequence of events.
Driving east at 100kph and I observe the event.

1st second, I see snow covered fields lit up ahead of me with Blue green
tint on either side of the road. I blink and I think "What the ....?"

2nd second, I glance upwards and forward and see overcast sky lit up.
Brightest area of sky appears to my left (North) which draws my eyes.

3rd second, I turn my head to look through the driver side window and
look up to see brightest illuminated patch of overcast sky centered at
55 degrees altitude and straight North.

4th second, The final fall of the meteor then comes into my view easily
visible through the overcast sky.  I noted a mottled pattern of shadows
in the overcast.  The meteor to be descending vertically straight down.
There was no flashes visible to me during this last second but the
meteor appeared to be decelerating rapidly.  The fall as initially
estimated was from 60 degrees to 45 degrees before the
whitish-blue-green meteor then broke up into several fragments and these
changed colour to a reddish orange.  These traversed another 2 to 3
degrees before fading out.  Please note I traveled to the same road 2
nights later with clear skies at virtually the same time of night and
quickly tested what I could see.  My original estimates for altitude of
the event need to be reduced by 5 degrees because I could only see 2 or
3 degrees above Polaris from my driver's side window.  Polaris in our
skies is about 53 degrees altitude at that location so my initial
altitude should be 55 degrees.  Another observation to confirm this
suspicion was Cassiopeia was visible to the west in a break in the
overcast skies and it's lowest altitude seemed similar to the
termination point of the meteor.  At that time of night, that makes the
lower altitude for the meteor as 40 degrees.

It took me another 10-15 seconds before I decided to stop or to turn
around.  This is the shock value that was hard to calculate to come up
with an absolutely accurate time for the fall.  I calc'd, it took me
about 10 to 15 seconds then to slow down and stop at a field access
point in order to turn around at.  I stepped out of the van for 15 to 20
seconds to note the time (I estimated 1:13:50 taking into consideration
of my stopping time) and to look at the sky to note what I could out of
the overcast skies.  I left my van running and didn't note any boom
during that short period of time.  I realize now I should have stopped
the engine and waited at least 5 minutes to listen but I wanted to back
track to remind myself of the position of the vehicle as per the
farmhouses nearby and any other points that could help in pinpointing
the azimuth of the fall against this overcast sky.  My first impression
was North or slightly West of North (even up to 355), but after my
second drive by 2 nights later, I'm leaning more to the final fall
azimuth as being slightly east of North by 2 to 5 degrees.  This is
strictly from being able to see Polaris that night and the memory of how
far I turned my head to look at the meteor.

My final time estimate was then adjusted to 1:14:22 MST to correct for
the watch being 32 seconds slow.  Since the Calgary All sky camera
started recording the meteor at 1:14:08 MST, this confirms that I failed
to correctly calculated the shock value I spoke of earlier.

I hope this better clears up what I saw that night.  I'm still wondering
if Brian Martin's Camera in Ardrossan saw anything of the event.  I
think it will give us the best geometry to develop the trajectory of the
fall, if there was one.  I'm also wondering if the UofA's camera is
working right now because of the move of the Physics Department?  Maybe
Doug Hube can report on this.

Mike Noble




-----Original Message-----
From: Bruce McCurdy [mailto:bmccurdy at telusplanet.net] 
Sent: December 24, 2006 1:45 PM
To: Noble, Mike
Subject: Fw: (meteorobs) Bright Fireball over Alberta Dec. 18


Hi Mike, this question came up on meteorobs (where I forwarded your
report). 
I would assume you would have said something if yes, but I won't presume
to answer on your behalf.

Bruce
*****

----- Original Message -----
From: <GeoZay at aol.com>
To: <meteorobs at meteorobs.org>
Sent: Sunday, December 24, 2006 12:44 PM
Subject: Re: (meteorobs) Bright Fireball over Alberta Dec. 18



>>>BTW, this was the brightest fireball that I have ever seen,  by many 
>>>magnitudes.<<

> Were there any sonic sounds...such as a thunderclap or rumbling within
the next few minutes?
> GeoZay

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