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(meteorobs) Geminids from Down Under
Hello all,
I'm fairly new to this mailing list (been here a week), and I hope I'm not
out of place, being all the way from Australia. I have thoroughly enjoyed
reading about everyones observations and stories, and other informative
tid-bits that may make a night under the stars/meteors more enjoyable.
Anyway, I thought I might bore you guys with some of my observations of
the Geminids from my location around Melbourne. (Note: there is a fair bit
of stuff here.)
A bit of background first, though. I've been observing meteors for about 9
years now, and before this year I was living in Adelaide, and did my
observations from its light polluted suburbs. I've always enjoyed the
Geminids mainly because they occur in the warm nights of summer here. Why,
I've even done a full night wearing shorts! However, at this southerly
latitude, the radiant just reaches an altitude of 20 degrees when due
north, and a full night typically only yielded a total of 50-60 meteors
(30 Gems) with LM~=5.0
Anyway, back to the present. I headed away from Melbourne to the country
and darker skies for Dec 13/14 and Dec 14/15 and was delighted with what I
saw. Dec 12/13 was completely clouded out.
[Note: this is by no means supposed to be a report, so I haven't included
stuff like dead time or breaks etc. Anyway, with the radiant so low I
figure that the data would be hard to make conclusions from anyway.]
Also, twilight starts at about 04:00 (17:00UT) in this neck of the woods,
and the radiant rises around 23:30 (12:30UT).
Data on individual meteors were recorded via manual entry. Typically I was
facing the Monoceros region.
==
Dec 13/14 (00:00->05:00 local time = 13:00->18:00UT)
Lat = -37 degs 54' : Long = 145 degs 30' east (11 hours ahead of UTC)
LM=5.7 (~50km east of Melbourne)
13:00->13:59UT 6 GEM, 2 HYD, 2 SPO : 10
14:00->14:59UT 7 GEM, 1 HYD, 10 SPO : 18
15:00->15:59UT 7 GEM, 2 HYD, 5 SPO : 14
16:00->16:59UT 19 GEM, 4 HYD, 12 SPO : 35
17:00->17:59UT 11 GEM, 0 HYD, 5 SPO : 16
- -------------------------------------------
TOTAL 50 GEM, 9 HYD, 34 SPO : 93 in total
This broke my previous record for the most meteors observed in one night.
Mag distribution
GEM: -2(2), -1(3), 0(8), +1(7), +2(5), +3(11), +4(12), +5(2)
HYD: +2(2), +3(2), +4(3), +5(2)
SPO: -2(1), -1(1), 0(2), +1(3), +2(2), +3(11), +4(13), +5(1)
Nothing special was seen. Perhaps the highlights of the night were
(1) a slow, mag -2 Geminid heading southeast for 40 degs through Puppis to
Vela,
(2) 4 meteors within a minute, and
(3) a clean pair of shoes considering the mounds of horse poop scattered
around the site.
(lesson #1: check out the site you're going to observe at during daylight
hours BEFORE you go to observe there.)
===================
Dec 14/15 (23:00->05:00 local time = 12:00->18:00UT)
LM=6.2 (~120km east of Melbourne)
Moonset at about 01:00 (13:00)
12:00->12:59UT 0 GEM, 0 HYD, 7 SPO : 7
13:00->13:59UT 14 GEM, 0 HYD, 6 SPO : 20
14:00->14:59UT 23 GEM, 2 HYD, 12 SPO : 37
15:00->15:59UT 22 GEM, 0 HYD, 7 SPO : 29
16:00->16:59UT 20 GEM, 0 HYD, 9 SPO : 29
17:00->17:59UT 22 GEM, 0 HYD, 10 SPO : 32
- --------------------------------------------
TOTAL 101 GEM, 2 HYD, 51 SPO : 154 in total
Another broken record for the most meteors in one night.
Mag distribution
GEM: -2(2), -1(8), 0(15), +1(11), +2(20), +3(32), +4(13), +5(0)
HYD: +3(1), +4(1)
SPO: 0(3), +1(5), +2(15), +3(16), +4(10), +5(2)
I was anticipating the peak to occur around Dec 14/15 22:00 (11:00UT)
local time, hence the earlier start. And indeed, activity was higher
early on compared to the previous night.
During this watch, I thought I was going to get something bigger than I
expected. At about 01:44 (14:44UT) I got up off my lawn chair to
stretch my legs and orient the chair northwards (originally facing
northeast). To do this, I needed to find due south which can be done using
Crux and the star Achernar (we need to do a bit more work down here to
find the celestial pole!).
Anyway, as soon as I gazed southward, a 10 deg, medium fast meteor of mag
2 headed south through Octans. Wow, that was convenient, I thought.
Whilst writing the details of this one down and looking up at the same
time, another medium fast meteor appeared, this time of mag 1 heading
south, cutting through the Small Magellanic Cloud and Hydrus in the
process. Then a minute later, another medium fast meteor appeared heading
west for 2 degs through Tucana.
Mentally I traced these three meteors back and they seemed to originate
from Phoenix. I remembered that there is a meteor shower originating from
Phoenix which is quite irregular, but I couldn't remember their exact peak
date. Perhaps this could be some sort of "storm" I thought jokingly to
myself.
2 minutes after the last meteor, a mag 3, medium fast meteor appeared
heading west for 2 degrees through Phoenix. "Too close to be from the
shower", I thought. Then another appeared heading northwest for 5 degs
through Eridanus. This was medium fast of mag 2. "This could be a member".
At this stage I was excited about this unknown prospect and didn't know
what to do. "Do I risk losing some Geminids to see if anything comes from
this?". I sat back down and faced north whilst I pondered this. After
seeing 4 GEMs and 1 SPO in 10 mins, I thought I should observe southwards
for at least 10 mins to see what happens. I did, and although I saw no
further activity from Phoenix, I did see a white, mag 0, fast, southward
heading Geminid pass through Puppis on to Carina for 30 degs with a train
visible for about 0.5 sec. I probably wouldn't have seen this if I
continued facing north.
Anyway, viewing the dates for when the Phoenicids are active suggests
that these meteors were probably sporadics coincidently lined up. These
were listed as such in the above observations.
At 03:55 (16:55UT) I saw my first pair of simultaneous meteors, ever, both
of which were Geminids. One was through Leo, medium fast, mag 2 heading
southeast for 10 degs, and the other through Gemini heading slowly south
for 3 degs of magnitude 3. They also ended at the same time due to their
appropriate speeds and path lengths.
This night concluded magnificently with, in twilight (stars brighter than
mag 3 visible), the appearance of two mag 0 Geminids within seconds of
each other, one heading south for 15 degs through Monoceros and the other
heading east for 5 degs through Cancer. Both were slow and white with a
green finish. This was followed 3 mins later by a very slow mag -2
white/green Geminid heading northwest for 10 degs through Auriga.
===
If I haven't bored everyone to tears by this stage, then perhaps you guys
can help me out with a query I have. I have looked at all the
documentation on the NAMN website but I cannot recall this being
mentioned. Apologies if this was mentioned somewhere and I overlooked it.
My query relates to the meteor length and its position in the sky. I
understand that the further you are from a radiant, the longer the meteor
is. This is stated in all texts. However, does the meteor length
also depend on its altitude and the component of motion directed
perpendicular to the horizon? I think (hope) it does.
For example, on Dec 13/14 I saw about a dozen meteors throughout the night
heading southeast through the Corvus/Crater/tail of Hydra region whilst
this region was about 30 degs high in the east-southeast (radiant about
due north). These had lengths of about 10-15 degs and when projected back
seemed to originate from Gemini (although, on the night I recorded them as
sigma Hydrids because of their short lengths).
And on Dec 14/15 I saw half a dozen meteors of length 10 degs heading
southwest through Cetus early on, and later on Eridanus, which when
projected back, appeared to come from Gemini. Judging by the distance from
the radiant, these meteors appeared rather short.
I would assume that being closer to the horizon and with some component of
motion directed downwards, I would be seeing them with a greater radial
component of motion away from me. This would reduce their path length, and
accordingly, their apparent speed. However, when occurring directly
overhead, the radial motion would be minimal and thus translate to a
greater path length and speed. Is this correct? Any comments?
Note: the above data present from my observations is based on this
assumption being correct.
Thanks for bearing with me for all of that.
Cheers.
- --
Robert A. Goler
E-mail robert@neumann.maths.monashdot edu.au
Department of Mathematics and Statistics
Monash University
Clayton, Vic 3168
Australia
- --
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