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Going Deeper: Telescopic Meteors
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MeteorObs - an Internet forum for meteor observers of all levels
Going Deeper: Telescopic Meteor Observing
Telescopic Meteor Observing is just what the name implies: observing
(and recording) meteors with a telescope or binoculars! This type of observing
is very demanding on the observing (it requires looking through an eyepiece
steadily at one field for a full half hour), but also offers some wonderful
and unique opportunities to contribute to the science of
meteors.
Note that the best way to introduce yourself to telescopic meteor
observing is by first learning as much as possible about unaided-eye
meteor observing, and in particular meteor plotting! If you would like to
find out how YOU can see a "Shooting Star Show" in your area, please take
the time to review in detail our pages on How to View
Meteor Showers.
If you are interested in subscribing to the 'meteorobs' mailing list, you may
use the MeteorObs Subscription Web form now!
Otherwise, you may post a (moderated)
message to the list even if you are not a subscriber.
If you're determined to try telescopic observing (which I encourage all meteor
observers to do at some point!), then keep in mind that the best way to make use
of the telescope is by plotting what you see... Counting meteors
through a telescope can be fun: However, please be aware that there are no
currently accepted methods for calibrating, analyzing or researching meteor
rates as seen through an eyepiece. Measuring fluxes of faint meteors would be
possible only with many more active observers and far more historical data.
Plotting is the raison d'etre for telescopic observing. And in fact,
shower association at the eyepiece can be very difficult indeed! In any case,
it's actually prefered that you don't make shower associations immediately at
the eyepiece. Instead, simply plot what you see relative to the star background,
as accurately as possible. The plotted trails allow objective criteria to be
applied in assessing shower assignment. The criteria can also be modified,
something that's not possible with an on-the-spot decision.
One Tip: Don't observe telescopically by pointing your instrument directly at a
shower radiant. You will see far more if instead you choose a field 15 to 25
degrees away from the radiant point in the sky. Some visual observers have their
center of vision at major-shower radiants. That's feasible because the unaided
eye has a much wider field of view than telescopes.
For those interested in trying "TM" (Telescopic Meteor plotting), be aware that
you'll see relatively fewer meteors than with unaided-eye observing: Telescopic
rates tend to be about 50% to 80% of visual rates for experienced observers.
This goes down in major showers which have relatively few faint meteors, such as
the Perseids.
Both telescopes and binoculars can be used for TM. But no matter what instrument
you choose to observe with, be sure it is one you can use in a very comfortable
position, and one you do not have to hold in your hands throughout the time you
are watching - in other words, your instrument must be mounted! This is PARAMOUNT.
Malcolm Currie, Telescopic Meteor
Commission Chairman of the International Meteor
Organization, suggests the following route for getting started in TM:
a) Begin with visual (unaided-eye) counts: learning the constellations and the
basics of meteor observing, including estimating your Limiting
Magnitude. You can read up on these basics
via the Web.
b) After becoming proficient at (a), try visual plotting when there is no major
shower active. This means obtaining a set of standard gnomonic star
charts (charts that show Great Circles as straight lines). Instructions on
plotting can be obtained at the American Meteor Society's Web site, in Norman
McLeod's Meteor Plotting.
Proper gnomonic charts can be obtained from the North American Meteor Network
and from the International Meteor Organization.
c) Once you are comfortable with unaided-eye plotting, you are ready to try
telescopic meteors. Telescopic observing is demanding, for it requires good
concentration and patience to start. Rates start slowly but increase with
experience. (It took Malcolm Currie, IMO Telescopic Commissioner, several
false starts to get going. Now he has an observing set up which allows him
to observe comfortably for many hours.)
The most definitive current TM reference is Malcolm Currie's guide:
http://www.jach.hawaii.edu/~mjc/imo/tele/telescopic.html
Though there are still non-functioning links on these pages, and some
are in an unfinished state, they are "required browsing" for anyone
who is seriously interested in Telescopic Observing. See in particular
the Introduction and pages on "Observation Techniques" and "Reports".
The NAMN observing Guide also has a chapter on telescopic meteors:
http://www.namnmeteors.org/guidechap4.html
These two showers, both active throughout the middle of June, have
both proved elusive for visual observers in recent years. The June
Lyrids (JLYs), a long known shower, and the Xi Draconids, a recently
"discovered" shower that may or may not be related to the JLYs, both
represent an excellent opportunity for Telescopic observers to
contribute to our knowledge of annual streams!
According to IMO Telescopic Commissioner Malcolm Currie, "Telescopic
(and video) techniques will let us locate the radiant if these showers
actually occur, and thus complement visual observing which can provide
a ZHR/flux curve."
Malcolm goes on to note, "The 'usual rules' apply: alternate between
fields every half hour. Concentrate on careful plotting. For many
observers, it will be a short night affected by twilight. If given a
choice of instruments to use under twilight skies, choose the one with
the smaller exit pupil - this will make for more comfortable viewing,
as the eye can accept the smaller beam and the contrast improves."
Below are downloadable copies of the best trio of charts to use for
researching BOTH of these elusive showers. NOTE that
observers who have trouble locating Chart 68 may choose instead to use
nearby Chart 67. Chart 68 has few unaided-eye stars, whereas Chart 67
contains the bright asterism of Nu, Phi, and Chi Herculis, and so may
be easier to find.
Still, Chart 68 is preferred as it lies closer to the radiants of
these two relatively fast-moving showers.
These "A" charts are scaled for small (30-50mm) binoculars:
For those with large-aperture binoculars or small non-inverting
telescopes (binoculars or scopes in the 60-80mm aperture range),
these deeper-magnitude and narrower-field "B" versions of the
charts above will be more useful!
Finally, if you have a rich field telescope (of over 80mm
aperture, but with at least 3 degrees true field at low power),
use the following "D" charts. These show stars all the way down
to magnitude 12.5, and are laterally inverted so that they may
be used with a (90 degree) star diagonal.
Clear skies!
Lew Gramer
<dedalus@alum.mit.edu>
Malcolm Currie
<mjc@star.rl.ac.uk>
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