(meteorobs) Southern meteors from a northern outpost
Bruce McCurdy
bmccurdy at telusplanet.net
Thu Jul 31 03:49:09 EDT 2008
The peak of the South Delta Aquariids this week was just the impetus I
needed to get out to RASC Edmonton Centre's observing site in the Beaver
Hills Dark Sky Preserve for a few hours early Tuesday morning. Pulling in to
an otherwise empty parking lot just after midnight, I was greeted with a
superb view of a long-lost friend: the Milky Way. After 12 long weeks of
perpetual twilight, not to mention much longer than that of perpetual light
pollution, what a joy to be under a dark sky again!
My rustiness showed in a few ways as Mr. Murphy struck again and again
without mercy. The Sky Quality Meter didn't work, presumably due to battery
malfunction; unfortunately I couldn't figure out how to open the darn thing
in the darkness that persisted due to *both* of my red flashlights also
malfunctioning. The one of those I could open in the dark needed the wrong
size batteries. Oh well, I didn't really need those flashlights to read the
Limiting Magnitude Field Locator charts I had forgotten at home. :( So I had
to resort to old-fashioned estimating of the LM. Fortunately my talking
watch and microcassette -- the two devices I actually tested before leaving
home -- worked fine, so the enumeration proceeded without further glitches.
Like its namesake shower on the other shoulder of perpetual twilight, the
Eta Aquariids, the SDAs are poorly situated for us far northern observers so
counts are always low. Last year I saw exactly one of each type of Aquariid
in what was ultimately a successful attempt to observe members of all twelve
major showers in the same calendar year. This May I again saw exactly one
Eta Aquariid, which was essentially the sum total of my meteor observing
since the Quadrantids. So my expectations were low; I was just happy to be
there.
Three hours later those expectations had been pleasantly exceeded, as I
had observed 10 SDAs among almost 50 meteors of all types. My hourly counts
stayed fairly consistent at 16, 15 and 18, as the rising radiants were
counteracted by the rising Moon as well as some light cloud which combined
to reduce limiting magnitude in the last hour. There were a number of very
nice meteors, notably a Venus-bright sporadic that dissected the Milky Way
leaving a three-second persistent train; and three -1 Capricornids.
Nonetheless in transcribing my tapes I am surprised to find how bright the
average meteor seems to have been, to the point that I am questioning my own
methodology. While I'm reasonably confident in my estimates of the brighter
meteors, I suspect I may have been consistently overrating the fainter ones.
Only one fifth-magnitude meteor in sixth magnitude skies seems improbable in
retrospect. (I told you I was rusty.)
The Moon cleared the trees around 2:30 local time. It was a compelling
sight, just three days from new and the pending Total Solar Eclipse that
some of my pals are going to see from the extreme north of Canada. The
waning crescent replete with earthshine towered above the most northerly
portion of the ecliptic, hanging just below Auriga like a temporary pendant
for the pentagon. Given that the SDAs peak occurs exactly a fortnight ahead
of the Perseids, it was easy to visualize the exact opposite conditions
applying w.r.t. both phase and declination on Perseid peak night: a fat
waxing gibbous Moon hovering far below the most southerly part of the
ecliptic. Indeed, in the morning hours of August 12 the Moon will be at
about -28° declination and will set well in advance of local midnight
despite its fairly advanced 11-day-old phase. (A similar opposite-Moon
relationship exists between the Lyrids and Eta Aquariids; the Orionids and
the (peak of the) South Taurids; and, imperfectly, the Ursids and
Quadrantids, meaning that every year one of each pair should be relatively
Moon-free, the other more problematic.)
The Perseids were already well in evidence on this night, as I saw more
of them (12) than meteors from any other radiant. That is one thing that
stands out from my count compared to others given on MeteorObs this week,
and surely speaks to my relatively extreme northerly latitude. My relatively
modest counts of 10 Aquariids and 7 Capricornids during the three hours are
both "personal bests", and I consider myself extremely fortunate to have
seen a single example of a Piscis Austrinid, whose radiant reaches just 6
degrees above my southern horizon at best. The one PAU I did spot, very late
and due south, was actually *dropping* to the lower left of Fomalhaut and
right into the treetops.
I had hoped to get right back out the very next night to see which way
the SDAs were trending, given the very interesting discussion on MeteorObs
about the uncertain date of the maximum. Alas, clouds rolled in just before
midnight on Tuesday evening and continue to persist, so that will have to be
a question for another year. Given the fine showing I saw this week, this
shower will be written on my calendar in pen for the foreseeable future.
In the immediate short term, now that the Water Bearer has sufficiently
"whetted" my appetite, it's on to the Perseids.
Bruce
*****
Observer: Bruce McCurdy, MCCBR
Date: 2008 July 29, 06:33 - 09:50; Teff = 3.0 hours
Location: Beaver Hills Dark Sky Preserve (Blackfoot), IMO Location Code
51128, 53°32'12" N, 112°, 46m 48s W, elevation 711 metres
Limiting magnitude: 6.2 until moonrise, 6.0 thereafter, gradually
deteriorating under light cloud in last hour // no SQM reading
due to equipment failure (hopefully just batteries)
Direction faced: East until moonrise, South thereafter
Method: Visual; microcassette recorder and talking watch
Comments in "quotations" are verbatim transcripts
/ = description of meteor in path length and duration
~ = description of persistent train in length and duration
Active radiants:
Alpha Capricornids (CAP) 20:20, -11; Velocity = 23km/sec.
Antihelion (ANT) 21:08, -15; Velocity = 30km/sec.
Delta Aquariids (SDA) 21:48, -19; Velocity = 41km/sec.
Pisces Austrinids (PAU) 22:44, -30; Velocity = 35km/sec.
Perseids (PER) 01:40, +53; Velocity = 59km/sec.
***
06:33 - 07:40 (less 7 minutes in breaks) ; clear; LM = ~6.2; facing E 90°;
Teff = 1.0 hour
Time Type Mag Comments
---------------------------------
06:33 start; facing due east, LM ~6.2
06:35 Spor +4
06:36 ANT +3
06:41 Spor +1
06:41 SDA 0
06:50 CAP -1
06:54 PER +4
06:55 Spor 0
06:57 PER +1
07:05 Spor -2 "faster than a Perseid"; heading straight up from E; ~
1s
07:12 Spor +4
07:12 SDA -1 ~ 0.5 s
07:14 Spor +3
07:16 CAP +4
07:20 PER +2
07:25 Spor -4 white w/ bronze tinge; broadened as it went; ~3s;
07:33 PER +1
***
2 CAP: -1, +4
1 ANT: +3
2 SDA: -1, 0
0 PAU
4 PER: +1 (2), +2, +4
7 Spor: -4, -2, 0, +1, +3, +4 (2)
Total meteors: sixteen
*****
07:40 - 08:40; clear; LM = ~6.2; facing E 90°; Teff = 1.0 hour
Time Type Mag Comments
---------------------------------
07:44 ANT +4
07:47 CAP +2 / 1 s, 20°
07:56 SDA 0
07:57 PER +3 near radiant, ~0.5 s
07:58 PER -1 bronze
08:06 CAP +2
08:07 SDA +4
08:08 Spor +3
08:09 PER +5
08:15 Spor +3
08:16 PER +3
08:24 PER +3
08:27 Spor +4
08:34 Spor +2 Moon above trees
08:35 SDA +2
***
2 CAP: +2 (2)
1 ANT: +4
3 SDA: 0, +2, +4
0 PAU
5 PER: -1, +3 (3), +5
4 Spor: +2, +3 (2), +4
Total meteors: fifteen
*****
08:40 - 09:50 (less 10 minutes in breaks) Moonlight reflecting off of light
incoming cloud; LM = 5.0 - 6.0; facing S 180°; Teff = 1.0 hour
Time Type Mag Comments
---------------------------------
08:44 Spor -3 (estimated) saw persistent train ~2 s
08:46 SDA -1 ~ 0.5 s
08:48 PER +2
08:50 Spor +3
08:52 Spor +3
09:03 Spor +4 ~1 mag extinction by thin cloud
09:03 CAP -1
09:08 ANT +1 ?? possible CAP, consistent with either radiants
09:15 PER +1
09:18 SDA +4
09:18 CAP +2
09:18 SDA +3
09:19 ANT +2
09:32 CAP -1 ~ 1 s
09:35 PER +3 "blue darter"
09:39 SDA +2
09:42 PAU +2 v. low in S
09:47 SDA +2 ~0.5 s
***
3 CAP: -1 (2), +2
2 ANT: +1, +2
5 SDA: -1, +2 (2), +3, +4
1 PAU: +2
3 PER: +1, +2, +3
4 SPO: -3, +3 (2), +4
Total meteors: eighteen
*****
Observing summary, Teff = 3.0 hours
--------------------------------------
7 CAP: -1(3), +2(3), +4 [avg. = +1.0]
4 ANT: +1, +2, +3, +4 [avg. = +2.5]
10 SDA: -1(2), 0(2), +2(3), +3, +4(2) [avg. = +1.5]
1 PAU: +2 [avg. = +2.0]
12 PER: -1, +1 (3), +2 (2), +3 (4), +4, +5 [avg. = +2.2]
15 Spor: -4, -3, -2, 0, +1, +2, +3(5), +4(4) [avg. = +1.7]
Total meteors: forty-nine
*****
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