Comparison of TV Magnitudes and Visual Magnitudes of Meteors
Yoshihiko Shigeno and Masayuki Toda
The generally accepted belief is that a meteor, with a large amount of infrared rays, can be captured brighter
than it actually is by infrared-sensitive image intensifiers (I.I.) or CCD. We conducted observations of meteors using
three methodologies: 1) I.I. attached with a filter that has visual magnitude equivalent to human eye spectrum
sensitivity at night vision, 2) I.I. without the filter and 3) visually to determine meteor magnitudes. A total of 31
members of the astronomical club at Meiji University observed 50 meteors in Perseids, 19 meteors in Geminids aswell as 44 sporadic meteors and the results were tabulated. The results helped us understand that on average I.I.
can capture meteors brighter than visual observation by the magnitude equivalent of 0.5 for Perseids, 1.0 for
Geminids and 0.5 for sporadic meteors.
For I.I. with a filter that has equivalent spectrum magnitude with the human eye at night vision, it turned outthat we could obtain almost the same magnitude with observation by the human eye.
We learned that a bright meteor with negative magnitude can be observed by I.I. brighter than the human eye.
From several examples, we found I.I. could capture a meteor with about -1 visual magnitude brighter by about threemagnitudes. We could probably do so because a bright meteor with negative magnitude may contain more infrared
rays and the brightness could be amplified.

1

Introduction

Magnitudes are important yardsticks to express the2 Comparison between TV Magnitudes andVisual Magnitudes

mass of meteoric materials and conventionally visual

Shigeno and Toda conducted a series of observations

magnitude or photographic magnitude have been used

to determine meteor magnitudes by both I.I. and visual

as the index (Opic, 1958; Verniani, 1967). Since aobservations: one time in April and two times in August

meteor contains more infrared rays (Borovicka et al.,2004. During the observations, we found a total of 211999), the generally accepted belief is that meteors canmeteors; for each meteor, its TV magnitudes werelook brighter when photographed by new observationbrighter than visual magnitude by 0.2 to 2.6 magnitude

instruments such as I.I. or CCD with more sensitivity toor 1.2 magnitude on average. It will be attributed to I.I.

infrared rays. By obtaining precisely the difference

that is also sensitive to infrared rays and capture

between conventional and new magnitudes of the samebrighter image of meteors as they contain more infrared

meteors, we are able to compare the conventional andrays.

new observation in a correct manner. However, it

We studied between TV magnitudes and visualappears that this comparison has not yet beenmagnitudes (Mtv-Mv) could be changed or not by other

implemented in a full scale. We would like to report thefactors. Figure 1 shows the relation between visual

results of the comparison of I.I. and visual observations.

magnitude (Mv), angular velocity (Va) and velocity ofobservation (VO) where the trend is not clear yet(Shigeno and Toda, 2005).

Figure 1 - Comparison between deviation(TV magnitude - Visual magnitude)(Mtv-Mv)
and Visual magnitude(Mv), Angular velocity(Va), Observed velocity(VO).

3
Observation by I.I. with Filter for 3.3 A bright meteor with negative magnitude
Spectrum Magnitude Equivalent of VisualA bright meteor with negative magnitude can beMagnitude
caught by I.I. brighter than visual observation. Figure 2
The above observation method cannot determine theis a list of typical examples of meteors with negative

correct visual magnitude. We, therefore, observed tomagnitudes. They are classified as approximately -1

determine meteor magnitudes by three other methods:

magnitude by visual observation whereas 1) MtvF are1) I.I. with a filter that has the same amount ofbrighter by approximately 1 magnitude and 2) Mtv arespectrum magnitude with visual magnitude at nightfurther brighter by approximately 2 magnitudes.

vision (MtvF), 2) I.I. without the filter (Mtv) and 3)

We assume the reason for the above item 1 is due tovisually. Magnitudes of TV meteors were obtained fromthe fact that the magnitude by TV observation is tothe relations between brightness, size and magnitudes

determine the brightest spot instantaneously whileof fixed stars and corrected by angular velocity. A total

visual observation determines averaged magnitude.

of 31 members of Meiji University's astronomical club

Therefore, as a brighter meteor may likely generate

observed 50 meteors in Perseids, from August 11 tomore

August 13, 2007, 19 meteors in Geminids on December

estimate

14 of the same year and 44 sporadic meteors. The

observation.

light instantaneously,
themagnitude

TV observationbrighterthanmayvisualresults are shown in Table 1 as tabulations by observers

For the reason noted in item 2, we assume thatfor comparison of magnitudes by I.I. and visualbrighter meteors with negative magnitude may beobservation.

caught brighter as they may contain a large amount ofinfrared rays.

3.1

Comparison of Mtv with MtvF

As shown by the upper column titled "Mtv-MtvF" ofTable 1, we obtained the following data: -0.5 magnitudefor Perseids, -1.0 magnitude for Geminids and -0.5
magnitude for sporadic meteors. These results suggestthat without filter observation shows brighter than theobservation with filter by 0.5 to 1.0 magnitude. In thetable, SD indicates the dispersion of data as standard
deviation and the results ranged from +/-0.6 to 0.7
magnitude, meaning they were the variation of data but
not errors in the average values.

3.2

Comparison of Mv with MtvF

The middle column of Table 1 shows the tabulated
results by observers. Negative values mean that theobservers had estimated brighter than actual while
positive values mean they had estimated darker. We

Figure 2 - Bright meteors with negative magnitude.

learned that some observers had estimated brighter byUpper photo. : No.P40 Aug.12,2007 17:07:50(UT) Per.

almost one magnitude while others had estimatedUpper left : Mtv = -4.0mag.

darker. However, from the total results of all theUpper right : MtvF = -1.7mag.

observers, i.e., "All Visual Observation Data" in theMv = -0.5mag.

bottom column of Table 1, it turned out that thedifference between the average of Mv and the average ofLower photo. : No.G05 Dec.14,2007 13:42:39(UT) Gem.

MtvF was somewhere between 0.0 to 0.2 magnitude andLower left : Mtv = -4.8mag.

the difference was minimal. That means MtvF in thisLower right : MtvF = -2.2mag.

report was almost meant to be Mv. However, we also

Mv = -1.4mag.

learned data variation by the observers was rather
large at +/-0.8 to 0.9 magnitude.

Filter : SCHOTT BG18 2mm (Filter that has equivalent
spectrum magnitude with the human eye at nightvision (400nm-600nm).)Spectrum sensitivity of I.I. : 350nm-900nm.

Table 1 - Tabulations by observers for comparison of magnitudes by I.I. and visual observation.
Mtv-MtvF : Comparison of magnitudes by without a filter(Mtv) and with a filter(MtvF).
Mv-MtvF : Comparison of magnitudes by Visual magnitude(Mv) and with a filter(MtvF).

4Conclusion

straight-line and curved line. Figure 3 shows the case ofPrevious infrared spectrum observation of Perseids

observation without the filter and the approximation ishad discovered several molecular bands such asdifferent in the case of observation with the filter.

630-670nm and 730-780nm nitrogen molecular bands

Figure 4 shows a fire ball discovered at TV

as well as many kinds of atomic luminescent lines suchobservation of a Leonids meteor swarm in 2001

as 777nm oxygen atomic luminescent lines (Ebizuka,(ShigenoN., personal communication). We learned that theserecomputed by the methodologies in this report and theinfrared rays make meteors look brighter by 0.5 to 1.0

magnitude turned out to be Mtv: -7.6. Unfortunately,

magnitude; especially meteors of negative magnitudes

however, we did not observe this meteor visually. Thatcanmakethe

differenceofbrightness

etal.,

2003).

The

original

datawaslarger.

particular day happened to be a meteor storm occasion

Meanwhile, we also learned that I.I. with the filter thatand a large number of people were observing but there

has the same amount of spectrum magnitude with

was no report of such a bright meteor. The actual

visual magnitude at night vision can observe meteors

magnitude of visual observation of the meteor iswith almost identical magnitude of visual observation.

assumed to be about -4 as there is a difference of

We would like to express our gratitude for valuableapproximately 3.5 magnitudes between Mv and Mtv asadvice from Mr. Mitsuru Terada for the relations

shown in Figure 2.

between magnitude and mass of meteors and from Mr.
Noboru Ebizuka for the infrared spectrum.

5

Supplementary Notes
We studied the relation between magnitudes andimage sizes of fixed stars in order to precisely obtain
magnitudes of meteors. Figure 3 shows the results ofobservations from two types of often-used objective
lenses: 85mm/F1.2 and 24mm/F1.4, respectively. The
relation between magnitudes of fixed stars darker thanFigure 4 - The figure on the left shows the TV0 magnitude and the size of image can be approximatedobservation equipment. The device with the Image

into an almost straight-line. However, we learned thatIntensifier (Delft High Tech XX1470 etc.). The figure on

fixed stars brighter than 0 magnitude may make thethe right shows an example of a double station TV

image size bigger rapidly. This would be because of themeteor. ID: MSSJBZ on Nov 18 2001 at 18:19:34 (UT).

characteristics of I.I. Then, we chose straight-line

TV magnitude (Mtv) = -7.6.

approximation at an area darker than 0 magnitude
while we used quadratic functional approximation atReferences

another area brighter than 0 magnitude in Figure 3 byOpic E. J. (1958). "Physics of meteor flight in theatmosphere", Interscience Publishers, Inc, 148.
Verniani F. (1967). "Meteor Masses and Luminosity",
Smithsonian Contributions to Astrophysics, Vol.10,
181-195.
Borovicka J., Stork R., Bocek J. (1999). "First resultsfrom video spectroscopy of 1998 Leonid meteors",
Meteoritics & Planetary Science, 34, 987-994.
Shigeno Y.,Toda M. (2005). "Double-station TV meteor
observations(2004.08.11-12)", Nippon Meteor Society,Apr,2005.
Shigeno Y., Shioi H., Shigeno T. (2003). "Radiants andorbits of the 2001 Leonids", The Institute of Space andAstronautical Science Report SP No.15, 55-62.
Allmeteors

have

been

openedhttp://www.imo.net/files/data/msswg/

Figure 3 - Comparison between magnitude of star andsize of image.

tothepublic.