[Prev][Next][Index][Thread]
(meteorobs) Geminids in Alaska / MeteorWB program (Re: Geminds/Earthgrazer Qu estion)
-----Oorspronkelijk bericht-----
Van: Thomas McCarty [mailto:tom@tech.engr.uafdot edu]
Onderwerp: Re: (meteorobs) Geminds/Earthgrazer Question
> As I'm new to this list and to trying to look at meteors
> I would like to ask some questions. I live in Fairbanks
> Alaska roughly 147.45 64.51.
> How and when would be the best times to look for Geminds?
> why when I try to use a star chart the stars don't match
> what I'm looking at? my computer program list my GMT -10
> but others list it as -9 what is correct?
I tried your location in SkyMap, Fairbanks is one of the presets, it's
listed as 540 minutes behind UT, when Daylight Savings Time is not active.
The first thing I noticed is that the radiant is circumpolar from your
location: it remains above the horizon all the time.
The Geminid maximum can be expected to begin between 0 UT and 4 UT in the
night between december 13/14, the enhanced activity will last for several
hours. On that day in Fairbanks, the sun will set at 14:40 Local time. Yet
it will take untill about 17:30 before it is dark enough for meteor
observing.
Still at that time the radiant is just above horizon. At 22:30 it will be 30
degrees above the horizon. So, I'd say keep an eye on the sky from 17:30 on.
The meteors should be visible all over the sky, but I think I will be
looking at a point somewhat to the right of Orion. This is about 40-45
degrees from the radiant where the balance between the length and the speed
of the meteors should be best.
Below is the output of a program I am working on. It is based on the data
given in the article:
Meteor stream activity. 1. The annual streams.
Jenniskens P.
Astron. Astrophys. 287, 990 (1994)
1994A&A...287..990J
I've set the location to Fairbanks, Alaska and added some (comments). I hope
to release a first beta version of the program soon.
Nightly Meteor Forecast
Fairbanks, Alaska, USA, 2001/12/13 to 2001/12/14
(all times are local times)
Local Conditions
Time Event Lm(Z)
14:40 Sun Set +0.2
16:04 Civil Twilight End +3.5
17:15 Nautical Twilight End +5.4
18:17 Astronomical Twilight End +6.6
00:00 Local Midnight +6.6
07:14 Astronomical Twilight Begin +6.6
08:15 Nautical Twilight Begin +5.4
09:27 Civil Twilight Begin +3.5
10:51 Sun Rise +0.2
(Lm(z) is the estimated limiting magnitude in zenith)
Moon altitude azimuth phase
at sunset -01° 217° 0.009
at midnight -47° 353° 0.003
at sunrise -01° 154° 0.000
Tonight at 17:15 nautical twilight will end. There is no lunar interference
and the sky remains dark for 15.0 hours. At 08:15 nautical twilight will
begin again.
Meteor Activity
Stream (midnight) ZHR RA DEC
Geminids 52.0 07h34m +31°57'
Puppids/Velids 1.9 09h07m -46°53'
Sigma Hydrusids 1.2 08h40m +01°00'
(ZHR is the estimated ZHR at local midnight, from the profile given in the
mentioned article)
Local Activity
Rate at:
Stream Trans TRANS NTE ATE MN ATB NTB
Geminids 02:52 46.9 3.4 14.0 41.4 34.7 9.6
Puppids/Velids 04:28 0.0 0.0 0.0 0.0 0.0 0.0
Sigma Hydrusids 04:02 0.6 0.0 0.0 0.3 0.4 0.1
(The rates are the expected visible rates, based on the expected ZHR at that
time, the estimated Limiting magnitude and the radiant altitude at that
time)
The Geminids are active tonight. The radiant location will be RA: 07h34m,
dec: +31°57'. At midnight their ZHR is expected to be between 50 and 54. The
radiant is circumpolar for your location, which means it is always above
the horizon. It will transit at 02:52 at an altitude of 57 degrees. From
your location you can then expect to see 45 to 49 meteors per hour. At the
beginning of the astronomical twilight at 07:14 the visible rate could be
between 33 and 36 meteors per hour.
(The article list the ZHR of the Geminids between 84 and 92, in recent years
it appears to have been closer to 120. It would be nice if something would
create an updated version of the Meteor Activity article :)
Daniel
The archive and Web site for our list is at http://www.meteorobs.org
If you are interested in complete links on the 2001 LEONIDS, see:
http://www.meteorobs.org/storms.html
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html