(meteorobs) Observation August 11/12 2008

Pierre Martin dob14.5 at sympatico.ca
Sat Aug 16 00:09:59 EDT 2008

Hello all,

With thick cloud cover appearing to persist above Ottawa, I packed  
the car and got ready to travel 180 km to the west of Ottawa, where a  
clear bubble was predicted to form after 11pm.  After picking up Ivo  
Leupi, we hit the road at 8:30pm EDT, with our GPS showing arrival  
near 11pm.  Our destination - an abandoned airstrip located deep  
within a dark sky zone (Bortle class 2, or grey on the light  
pollution map)!  The 2 hour or so drive was uneventful, with nice  
smooth roads to get there and no traffic.  The Moon and stars poked  
through a few holes overhead, which gave us some hope...  The GPS was  
quite helpful in helping us find the site entrance without any  
trouble in the dark.

We arrived at the site, and had 100% cloud cover.  The air was calm  
without a hint of wind.  We were a bit worried that maybe the clouds  
had stalled, or the clearing happened somewhere else.  We setup the  
tent and camera equipment, before taking a break to sit back and  
enjoy some tasty pastries that Ivo had made himself.  The night was  
comfortable with a temp of about 12C and no mosquitoes.  There was  
some fog in the distance.  Not a sound could be heard from this site  
- a very quiet and serene place!  About half an hour later, we  
spotted a line of clearing low in the west.  We regained some hope.   
As I prepared my cameras, I could gradually see more and more stars  
slowly coming out in the west!  Great, the clouds were dissipating!   
Soon, the bright gibbous Moon came into view and illuminated the  
ground until we didn't need flashlights to finish setting up.  Now it  
was passed midnight, and the sky was 50% clear... and was slowly  
getting better!  Every once in a while, a Perseid would flash by  
without us even trying to look for them.  Just as the Moon was about  
to set, near 1am, the last few wisps of clouds vanished!  The Milky  
Way brightened, and more and more faint stars popped out.  Meteors  
increased with many fainter ones being seen now.  I got my cameras  
operating, and settled into my lawn chair to begin recording meteors...

For the remainder of the night, I faced the east, keeping the  
Perseids radiant within my field of view.  The sky transparency  
ranged from 2/5 to 3/5, and varying layers of ground fog affected the  
horizons around us.  My field of view at 50-60 degrees elevation  
remained mostly unaffected for the rest of the night, with a limiting  
magnitude of about 6.7.  The sky overhead was impressive, with tons  
of structure in the Milky Way, and zero light pollution all around.   
The wide-open horizons gave a sense of the sky dominating the scene.   
Later in the night, the zodiacal light was bright enough to be almost  
a nuisance :0)

The Perseids were very active.  Rates exceeded one per minute, on  
average.  Observing for 3 hours and 20 minutes, I recorded 276  
meteors.  This total breaks down to 235 Perseids, 37 sporadics, 2  
Delta Aquarids, 1 Capricornid and 1 antihelion.  I also kept an eye  
for Kappa Cygnids, but none were seen.

Perseids rates for each one-hour period were 64, 72, 72.  I stayed on  
for an additional 19 minutes of observing (well into brightening  
twilight) and had 27 Perseids.  These are some of the highest rates  
that I've seen from this shower in this decade (although 2004 was  
better still for me).  The meteor "clumping" seemed to be more than  
just coincidence, with many quiet moments followed by quick, sudden  
bursts.  I counted 13 instances of a pair of Perseids appearing  
nearly simultaneously.  There was even an instance when 3 Perseids  
scooted by within 3 seconds... that brought a tiny flashback of the  
awesome 2001 Leonid meteor storm :0)

The magnitude distribution for Perseids appeared typical.  The most  
numerous meteors were in the mag +2 to +4 range.  I even got a few  
+6 !  On the other end of the scale, I got five Perseids bright  
enough to be considered fireballs.  The most impressive was the two  
mag -4 fireballs... each ending in a terminal flash.  Ivo was lucky  
enough to capture these beauties with his camera.  One of them was a  
vivid yellow-green flaring meteor that left a persistent train  
hanging for 20 sec.  Interestingly, the average limiting magnitude  
for all Perseids is +2.59 - a result that's identical to the 2004  

Because of the Perseids high velocity (59km/sec), many tend to leave  
persistent trains that can linger for seconds or even minutes.  On  
this night, 43% of all Perseids left a wake or a train.  Brighter  
Perseids were typically colored yellow or blue, with a few orange and  
blue-green meteors thrown in.

I signed off and stopped the camera exposures just before 5am EDT,  
with bright twilight quickly taking over (I know it's a good show  
when I don't want the night to end :0)  There was lots of dew, but my  
thankfully my heaters kept the camera lenses dry all night.  I  
continued to casually see a few more Perseids as the sky turned blue  
and all but the brightest stars were gone.  At the end, I was  
exhausted but very satisfied of this session!  It's one that I won't  
soon forget!

Summary data below... For now, I used standard 1 hour TEFF periods.   
I'll forward my shorter periods as soon as I get a chance to complete  

Pierre Martin
Ottawa, Ontario

DATE: August 11/12 2008
BEGIN: 0510 UT (0110 EDT) END: 0855 UT (0455 EDT)
OBSERVER: Pierre Martin (MARPI)
LOCATION: Long: -77 15' West; Lat: 45 1' North Elevation: 800 ft
City & Province: Irvine Lake Airstrip (near Bon Echo Park), Ontario,  
RECORDING METHOD: talking clock/tape recorder, cord align

OBSERVED SHOWERS:_______________________________radiant position
KCG (Kappa Cygnids)_______________________________18:56 (284) +58
CAP (Alpha Capricornids)__________________________21:12 (318) -06
ANT (Antihelions)_________________________________22:00 (330) -10
SDA (Delta Aquarids)______________________________23:16 (349) -13
PER (Perseids)____________________________________03:00 (045) +57
SPO (sporadics)

OBSERVING PERIODS: 0 = none seen; / = shower not observed



= 276

Note: The first column (Period UT) refers to observing periods broken  
down as close as possible to one hour of true observing, in Universal  
Time. The second column (Field) is the area in in the sky where I  
centered my field of view. The third column (TEFF) represents  
effective observing time (corrected for breaks or any time not spent  
looking at the sky). The column (LM) is the average naked eye  
limiting magnitude, determined by triangle star counts. All following  
columns indicate the number of meteors for each shower observed.




Note: Magnitude -8 is comparable to a quarter moon, magnitude -4 with  
the planet Venus, magnitude -1 with the brightest star Sirius,  
magnitude +2 to +3 with most average naked eye stars and magnitude +6  
to +7 are the faintest stars the naked eye can see under typical dark  
conditions. A meteor of at least magnitude -3 is considered a  
fireball. The above table contains the magnitudes from all observed  
meteors, and the average (last column) for showers.



Dead time: 24 min (incl breaks time)

Breaks (UT): 5:41-46, 6:53-54, 7:00-11, 8:28-29, 8:33-37, 8:42-44,  

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