1 Introduction

For more than 15 years, astrometric and photometric observations of asteroids and comets have been made at the Astronomical and Geophysical Observatory (AGO) of the Comenius University in Modra, as well as all-sky photographic meteor observations using Zeiss Distagon photographic cameras fitted with 3.5/30 mm fish-eye lenses (Zigo et al. 2006; Gajdoš et al. 2006). Two photographic meteor cameras operate at the site, one in fixed and another in a guided mode. Our station No. 21 Modra (Fig. 1a) is a part of the European Network (EN) for fireball detection coordinated by Ondřejov Observatory, Czech Republic. In the past, we had used TV cameras for major meteor shower observations (Tóth and Kornoš 2007). Recently we have developed a new fish-eye TV system to be used mainly for minor meteor shower observations.

Fig. 1
figure 1

(a) Part of European Fireball Network (Oberst et al. 1998), Modra station is marked by No. 21. The assumed observed radius is depicted by the circle. (b) The new fish-eye TV meteor system (in the middle) has started regular observations on April 1, 2007

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2 The Fish-eye TV System

The new fish-eye TV meteor system (Fig. 1b) has started regular observations on April 1, 2007. The system consists of a fish-eye Canon 2.4/15 mm objective, 2″ Mullard image intensifier, Meopta 1.9/16 mm lens and a Watec 120N camera. The analog video signal is digitized in real time and analysed by “UFOCapture" software (author SonotaCo, http://www.sonotaco.com/e_index.html), which is able to detect any moving object including meteors. The resolution of the system is 720 × 540 (15 arcmin/px), corresponding to a field of view of 170° × 140° (Fig. 2). The limiting stellar magnitude is +5.5m and meteors up to magnitude +3m are detected. The system operates autonomously.

Fig. 2
figure 2

An example of the all-sky composite negative image obtained from an avi file of TV fish-eye system. The bright meteor, stars and Milky way are clearly visible. The limiting stellar magnitude is +5.5m. South is up and west is on the left

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The astrometric precision of this fish-eye TV system is quite good. The standard deviation for more than 50 stars reduced by the “UFOAnalyserV2" is less than 0.05° for zenithal distances up to 60°. Also we have tested the position accuracy for several stars and planets near the horizon, where the astrometric precision of the measurement decreases to 0.5°. The fourth order polynomial expansion used by UFOAnalyserV2 is insufficient to correct fish-eye projection, especially near horizon.

3 Results

3.1 April 2007 Results

Our TV system, operating as a single station worked 27 nights (199 h) during April 2007, including nights with a bright Moon. In total 300 meteors were detected: 74 Lyrids, 24 meteors from antihelion source, 10 meteors from helion source, 20 meteors from other sources and 172 other sporadics. The identification of Lyrids were based in their radiant position and angular velocity. The sporadic meteor frequency was in the range of 0.5–3 meteors per hour, depending on the Moon phase, which reduced meteor rates due to the bright background of the sky. During this month, TV and photographic fish-eye cameras observed 7 fireballs. The brightest fireball was about −10th magnitude. The orbit of the “Kozmice" fireball from April 14 was also observed by our TV system and the EN photographic cameras for which Spurný (pers. comm. 2007) calculated its precise orbit as a = 1.2780 ± 0.0007 AU, e = 0.5073 ± 0.0003, q = 0.62961 ± 0.00014 AU, Q = 1.9263 ± 0.0014 AU, ω = 276.09° ± 0.03°, Ω = 24.36223° ± 0.00001°, i = 7.934° ± 0.009°. The meteoroid, which had photometric mass of 3 kg, has a typical NEO orbit of Apollo type. The observed astrometric position of the fireball by TV and photographic method from Modra station correspond to each other within 3 arcmin.

3.2 Single Station Observations of the 2007 Lyrids

We observed the Lyrid activity for the period April 10–26. The activity profile during the night of maximum activity (April 22/23) was derived from fish-eye TV single station observations that were corrected to the radiant position (Fig. 3a). The discrepancy between our video and the IMO visual data for the Lyrid ZHRs is mainly caused by the Moon light, which reduced meteor rates during the first part of the night. We also obtained a single station radiant position at the time of maximum activity (α = 272.5°, δ = 33.2°, \(\lambda_{\odot} =33.2^\circ)\) for these 74 Lyrids (Fig. 3b). The diameter of the radiant area from the entire activity interval was 10°. The faintest observed Lyrid meteor was about magnitude +3m and the brightest one was about −6th magnitude.

Fig. 3
figure 3

(a) The activity profile (histogram) compared with the visual observations (black square) from IMO (Barentsen 2007). (b) Single station radiant of 74 Lyrids has diameter 10°. The scale of the image is about 100° ×  100°

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3.3 Two Station Orbits from the 2006 Geminids

The activity of the Geminid meteor shower was monitored from two stations at Modra and Stupava that were both equipped with test non-intensified cameras (details in Tóth and Kornoš 2007) with 20° field of view.

Tóth and Kornoš (2007) presented the activity profile that was derived for this TV system and found that maximum activity peaked at 1:30 ± 0:30 UT December 14, 2006 and the single station radiant position was α =  114.0°, δ = 33.3°.

The radiant area derived from 31 Geminid meteor observations is very compact (less than 1°). This is indirect confirmation of the astrometric precision of “UFOAnalyser” software, because Geminids are very well known for their compact radiant. Six Geminids were simultaneously observed from both stations. The heliocentric orbits for the two brightest meteors were computed by the “UFOOrbit" software (Table 1).

Table 1 The individual radiant positions and orbit parameters of two Geminids observed at 1:34:23 and 5:07:01 UT on December 14, 2006. The mean radiant and mean orbit of Geminid meteor shower are mentioned for comparison with our data
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4 Conclusions

We described our first experience with the new fish-eye TV system as well as the “UFOCapture", “UFOAnalyser" and “UFOOrbit" software. We are able to capture meteor activity under suitable conditions and provide reliable data, although we do not have permanent and identical second station yet. We hope we will be able to provide TV meteor orbital data on the regular bases in the near future.