(meteorobs) GPS - Fireball reports etc.

Ed Majden epmajden at shaw.ca
Thu Aug 26 13:55:46 EDT 2004


Hello Wally:
    Mark Davis forwarded your email to me regarding your question about GPS
units.  There are so many out there these days it is hard to recommend one.
I'm not a GPS expert by any means but here are some suggestions.  Much of it
depends on the money you have to spend.  I have an entry level Eagle
Explorer but now wish I had waited and bought an upscale model.

1.  Get one that will average readings over a period of time.  Even the best
non military ones have limited accuracy I'm told.  Good enough for boaters
and hikers etc but if you want to pin down a site for occultation
observations you want the best.  Even here, IOTA (International Occultation
Timing Association) recommends that you get elevation measurements from a
Geological Survey Map.
A Geo Map is of course the least expensive way to go.

2.  Get one that you can interface with a laptop computer and a mapping
program.

I would do a search with "google" for GPS.  There is a bunch of good
information on the web.  Garmin models seem popular.  I hope I have spelled
that correctly!

As for a "Fireball Reporting Kit", an important thing is some method to
measure the elevation of the fireball above the horizon for the start and
end point.  I have a SUUNTO clinometer which can be read by a single
individual.  An inexpensive "roof slope" measuring device is also okay but
it takes two people to use it.  One to sight the elevation of the fireball
and the other to take the reading.  This device can also be used to measure
the slope of the fireball path which is important in some cases.  One can
also use a simple plastic protractor with a weight suspended by a thread
from the apex.  You sight the elevation with the protractor and the weight
acts as a blumb-bob.  You simply squeeze the string and take the reading.
Get a good protractor marked off in 1/2 degree steps.  Make sure you are
sighting the correct way by checking at the horizon which should read "zero"
degrees, and "90 degrees" for Zenith.  Such readings if properly taken will
rival an all-sky camera photograph.  Only thing your missing is "accurate
time" and "velocity" which can be determined if the fireball is recorded by
video all-sky systems at two different locations.  Even a camcorder record
is valuable!  More important also, is a "good" sighting compass that you can
read to 1 degree accuracy or better.  There are a variety of models
available from outdoor shops.  Make sure your azmith bearings are reported
as magnetic or corrected to "true" north.  It is a good idea to include both
in a report.
    One thing I should mention, if a telescope has digital setting circles
by all means use the readings from it.  Pont the telescope at the start and
end point of the fireball path and jot down the readings with the time you
took them.  Some models can give you RA and Dec or can be switched for Az-El
readings.  Some of these scopes like Celestron an Meade LX200-GPS even have
built in GPS capability.  Amateurs often take their scopes out to dark sky
sites for observations.  You never know when you will see a bright fireball.
Stay alert, take the readings, and submit a fireball report!
    We are building a web site on Meteor Astronomy for Amateurs which will
have much of this information on it.  I will publish the url on meteorobs
when it is ready for viewing.
    Good luck with your project and may you see many large fireballs! ;-)

Ed Majden
West Coast Sandia Bolide Detection Station
Courtenay B.C. CANADA.

>From the "WET" coast, in the winter season at least!  ;-(



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