[meteorite-list] 10/04/14 AZ Fireball: Sextant-Compass readings of Belmont, AZ smoke tr ail

From: Steve Schoner <schoner_at_meteoritecentral.com>
Date: Sat, 11 Oct 2014 00:55:13 GMT
Message-ID: <20141010.185513.15764.0_at_webmail08.dca.untd.com>

Hello all,

I took a trip out to the Belmont, AZ Weather Service and stood in front of the camera that took the photo of the smoke cloud 5 or 6 minutes after it had ended. I had the photo in hand to estimate to the best of my ability as to where the clouds were in the sky as related to Fremont Peak that morning. These clouds might have dissipated somewhat and drifted slightly to the south east 5 to 6 min after the fireball passed.

I spent over an hour taking readings with my WWII Bendix A-7 sextant, and two WWI British prismatic compasses, averaging the readings of each.

(BTW: these compasses are top notch, so good that they were used by sailors lost at sea to find destinations even without a sextant. The WWII Bendix A-7 is a fantastic sextant and very accurate as well)

Readings from the compasses: (Magnetic) 35 - 36 degrees Easterly direction.

Sextant, after estimating where the clouds were over Fremont Peak.

Top cloud (larger one): 13.0 degrees above horizon.

Bottom cloud (smaller one): 7.25 degrees above horizon.

Average between both as the two clouds are linked in a chain ~8.6 degrees above horizon.

The top cloud which is very dispersed after the six or so min after the fireball end at 15:52:32 represents the start of the fireball, and from reports it came in a a very steep angle ~45 degrees from the North East. This fireball was observed from the Belmont location and others West of Flagstaff including my all sky camera, as going DOWNWARD. If it rose up, or remained stationary instead of downward as it did, then it would appear heading toward and above the Belmont Weather station camera. In all sightings west of Flagstaff it went DOWNWARD and to the East.

So the higher cloud appears higher in the sky due to the fact that the luminous flight began at about 60 miles or so. The smaller more defined cloud is the lower one to the ground maybe 15 to 20 miles above ground and closer to the Belmont Weather camera than the more distant larger dispersed portion of the smoke cloud.

Do the trig. 13, 7.25 degrees above the horizon and an average between the two above the horizon taking into account the downward angle of the Fireball and the average assumed height between the beginning and the end of the event between 60 and 15 miles above the ground.

The larger cloud is most likely over 120 miles away from the camera. The lower one most likely over 70 miles away from the camera.

And the compass heading of 35-36 degrees is a magnetic heading, keeping in mind the magnetic variation of 10.5 degrees to East of the the Celestial Pole which is True North to which my all sky camera is aligned.

Draw your lines accordingly from the Belmont Weather Station at Navajo Army Depot along that line of magnetic bearing 35-36 degrees average between the two 35.5 degrees. If you transpose to a map that is aligned to the true Celestial North, be sure to take into account the magnetic variation of 10.5 degrees in drawing the line.


Steve Schoner.
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Received on Fri 10 Oct 2014 08:55:13 PM PDT