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3 Measurements

The measurement lasted for approximately 15 minutes for each star observed. The principle of the measurements is called point run which is normally used as an angular adjusting procedure for the telescope. For such a point run a certain area of the camera is covered with a prechosen virtual point grid. On each coordinate of this grid the star is subsequently focused and the anode current of each photomultiplier is read out and recorded. At the beginning and at the end of such runs, the central pixel is pointed to the star. In this pilot study stars were only projected onto approximately 15 photomultiplier tubes of the central region of the camera. The grid had a dimension of 15 $\times$ 15 points. Covering the whole camera surface by the calibration procedure is a trivial problem of more measuring time. The selected stars (see Sect. 2) which have been used and some characteristic data are listed in Table 1.


Table 1: Stars the photon flux of which is measured for the calibration. Given are their HR number, locii (right ascension, declination), spectral type (taken out of the Astronomical Almanac, Hagen & Boksenberg [1995], and only for 68 Her and 12 Vul from Friedrichsen [1993]) and their effective temperature (estimated with Lang [1992]). 10 Lac was measured twice. We are aware that the spectral types and absolute magnitudes of the chosen stars are slightly variable. This can in principle be considered by forthcoming applications of the method but was not in the scope of the present study
Flamsteed/Bayer HR No. Right Declination Spectral Effective
Designation   Ascension   Type Temperature


$\theta$ CrB 5778 15h 32m 44.9s $+~31^{\circ}~22'~27''$ B6 Vnn $\sim$14000 K
22 $\tau $ Her 6092 16h 19m 36.3s $+~46^{\circ}~19'~26''$ B5 IV $\sim$15000 K
68   Her 6431 17h 17m 19.4s $+~33^{\circ}~06'~00''$ B3 III $\sim$17000 K
85 $\iota$ Her 6588 17h 39m 20.3s $+~46^{\circ}~00'~31''$ B3 IV $\sim$19000 K
67   Oph 6714 18h 00m 25.2s $+~02^{\circ}~55'~53''$ B5 Ib $\sim$13500 K
102   Her 6787 18h 08m 34.0s $+~20^{\circ}~48'~49''$ B2 IV $\sim$21000 K
10 $\beta$ Lyr 7106 18h 49m 54.8s $+~33^{\circ}~21'~26''$ B7 Vpe (shell) $\sim$13000 K
20 $\eta$ Lyr 7298 19h 13m 36.3s $+~39^{\circ}~08'~17''$ B2.5 IV $\sim$19000 K
8   Cyg 7426 19h 31m 36.3s $+~34^{\circ}~26'~36''$ B3 IV $\sim$18000 K
12   Vul 7565 19h 51m 04.0s $+~22^{\circ}~36'~36''$ B2.5 Ve $\sim$19000 K
59 v832 Cyg 8047 20h 59m 40.4s $+~47^{\circ}~30'~12''$ B1.5 Vnne $\sim$23000 K
66   Cyg 8146 21h 17m 44.0s $+~34^{\circ}~52'~40''$ B2 Ve $\sim$22000 K
10   Lac 8622 22h 39m 03.5s $+~39^{\circ}~01'~36''$ O9 V $\sim$33000 K
81 $\pi^2$ Cyg 8335 21h 46m 37.6s $+~49^{\circ}~17'~19''$ B2.5 III $\sim$18000 K

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