Changeset 779


Ignore:
Timestamp:
May 4, 2001, 10:40:57 AM (20 years ago)
Author:
wittek
Message:
*** empty log message ***
File:
1 edited

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  • trunk/MagicDoku/strategy_mc_ana.tex

    r777 r779  
    8383directed not to the position of the selected source but rather to a
    8484position 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.
     85position. Every 20 minutes of observation the sign of $\Delta\beta$ is
     86changed. The two wobble positions are called wobble position 1 and 2.
     87
     88$\Delta \beta$ may be chosen to be a direction difference
     89in celestial coordinates
     90(declination $\delta$, right ascension $\Phi$) or in local coordinates
     91(zenith angle $\Theta$, azimuthal angle $\phi$).
     92However the direction $\Delta \beta$ is defined,
     93the sky region projected onto the camera is different for
     94wobble positions 1 and 2.
     95
     96If $\Delta \beta$ is defined to be a direction difference
     97in celestial coordinates,
     98the sky region projected onto the camera for a fixed wobble position
     99remains the same during tracking of a source, although the sky image
     100is rotating in the camera.
     101
     102If $\Delta \beta$ is defined to be a direction difference
     103in local coordinates,
     104the sky region projected onto the camera is changing continuously
     105during tracking of a source. The centers of the projected sky regions
     106lie on a circle, which is centered at the source position.
     107
     108If $\Delta \beta$ is defined to be a direction difference
     109in the local azimuthal
     110angle $\phi$, the center of the camera and the source position
     111would always have the same zenith angle $\Theta$. Since the reconstruction
     112efficiency of showers mainly depends on $\Theta$, this may be an
     113advantage of defining $\Delta \beta$ in this way.
    104114
    105115The wobble mode has to be understood as an alternative to taking on-
     
    107117that one is taking on-data only, from which also the 'off-data' have to be
    108118obtained by some procedure.
     119
     120Open questions : - how should $\Delta \beta$ be defined
     121                 - how big should $\Delta \beta$ be chosen
    109122
    110123\item Pedestals :\\
     
    832845\begin{thebibliography}{xxxxxxxxxxxxxxx}
    833846\bibitem{fegan96}D.J.Fegan, Space Sci.Rev. 75 (1996)137
    834 \bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 1 (1985) 155
     847\bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 3 (1985) 445
    835848\bibitem{konopelko99}A.Konopelko et al., Astropart. Phys. 10 (1999)
    836849275
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