- Timestamp:
- 05/04/01 10:40:57 (24 years ago)
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trunk/MagicDoku/strategy_mc_ana.tex
r777 r779 83 83 directed not to the position of the selected source but rather to a 84 84 position which has a certain offset ($\Delta\beta$) from the source 85 position. $\Delta\beta$ is taken as ... degree in right ascension and 86 every 20 minutes of observation the sign of $\Delta\beta$ is changed. 87 The two wobble positions are called wobble-1 and wobble-2. 88 89 There is no compelling reason to do the wobbling in right ascension 90 rather than in any other direction. It also appears that this choice 91 has no severe consequences for the analysis. 92 93 Note that the sky region projected onto the camera is different for 94 wobble positions 1 and 2. For fixed wobble position the sky region 95 projected onto the camera remains the same during tracking of a 96 source, although the sky image is rotating in the camera. 97 98 The sky region projected onto the camera would not remain the same 99 during tracking of a source, if $\Delta \beta$ were defined as a fixed 100 angle in the local angles $\Theta$ or $\phi$. This would not 101 necessarily be a disadvantage. In the case $\Delta \beta$ is taken as 102 a fixed angle in $\phi$ a sky region would be selected whose center 103 has the same zenith angle $\Theta$ as the source being observed. 85 position. Every 20 minutes of observation the sign of $\Delta\beta$ is 86 changed. The two wobble positions are called wobble position 1 and 2. 87 88 $\Delta \beta$ may be chosen to be a direction difference 89 in celestial coordinates 90 (declination $\delta$, right ascension $\Phi$) or in local coordinates 91 (zenith angle $\Theta$, azimuthal angle $\phi$). 92 However the direction $\Delta \beta$ is defined, 93 the sky region projected onto the camera is different for 94 wobble positions 1 and 2. 95 96 If $\Delta \beta$ is defined to be a direction difference 97 in celestial coordinates, 98 the sky region projected onto the camera for a fixed wobble position 99 remains the same during tracking of a source, although the sky image 100 is rotating in the camera. 101 102 If $\Delta \beta$ is defined to be a direction difference 103 in local coordinates, 104 the sky region projected onto the camera is changing continuously 105 during tracking of a source. The centers of the projected sky regions 106 lie on a circle, which is centered at the source position. 107 108 If $\Delta \beta$ is defined to be a direction difference 109 in the local azimuthal 110 angle $\phi$, the center of the camera and the source position 111 would always have the same zenith angle $\Theta$. Since the reconstruction 112 efficiency of showers mainly depends on $\Theta$, this may be an 113 advantage of defining $\Delta \beta$ in this way. 104 114 105 115 The wobble mode has to be understood as an alternative to taking on- … … 107 117 that one is taking on-data only, from which also the 'off-data' have to be 108 118 obtained by some procedure. 119 120 Open questions : - how should $\Delta \beta$ be defined 121 - how big should $\Delta \beta$ be chosen 109 122 110 123 \item Pedestals :\\ … … 832 845 \begin{thebibliography}{xxxxxxxxxxxxxxx} 833 846 \bibitem{fegan96}D.J.Fegan, Space Sci.Rev. 75 (1996)137 834 \bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 1 (1985) 155847 \bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 3 (1985) 445 835 848 \bibitem{konopelko99}A.Konopelko et al., Astropart. Phys. 10 (1999) 836 849 275
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