Index: /trunk/MagicDoku/strategy_mc_ana.tex
===================================================================
--- /trunk/MagicDoku/strategy_mc_ana.tex	(revision 778)
+++ /trunk/MagicDoku/strategy_mc_ana.tex	(revision 779)
@@ -83,23 +83,33 @@
 directed not to the position of the selected source but rather to a
 position which has a certain offset ($\Delta\beta$) from the source
-position. $\Delta\beta$ is taken as  ... degree in right ascension and
-every 20 minutes of observation the sign of $\Delta\beta$ is changed.
-The two wobble positions are called wobble-1 and wobble-2.
-
-There is no compelling reason to do the wobbling in right ascension 
-rather than in any other direction. It also appears that this choice
-has no severe consequences for the analysis.
-
-Note that the sky region projected onto the camera is different for
-wobble positions 1 and 2. For fixed wobble position the sky region
-projected onto the camera remains the same during tracking of a
-source, although the sky image is rotating in the camera.
-
-The sky region projected onto the camera would not remain the same
-during tracking of a source, if $\Delta \beta$ were defined as a fixed
-angle in the local angles $\Theta$ or $\phi$. This would not
-necessarily be a disadvantage. In the case $\Delta \beta$ is taken as
-a fixed angle in $\phi$ a sky region would be selected whose center
-has the same zenith angle $\Theta$ as the source being observed.
+position. Every 20 minutes of observation the sign of $\Delta\beta$ is 
+changed. The two wobble positions are called wobble position 1 and 2.
+
+$\Delta \beta$ may be chosen to be a direction difference 
+in celestial coordinates
+(declination $\delta$, right ascension $\Phi$) or in local coordinates
+(zenith angle $\Theta$, azimuthal angle $\phi$).
+However the direction $\Delta \beta$ is defined,
+the sky region projected onto the camera is different for
+wobble positions 1 and 2. 
+
+If $\Delta \beta$ is defined to be a direction difference 
+in celestial coordinates,
+the sky region projected onto the camera for a fixed wobble position 
+remains the same during tracking of a source, although the sky image 
+is rotating in the camera.
+
+If $\Delta \beta$ is defined to be a direction difference 
+in local coordinates,
+the sky region projected onto the camera is changing continuously 
+during tracking of a source. The centers of the projected sky regions
+lie on a circle, which is centered at the source position.
+
+If $\Delta \beta$ is defined to be a direction difference 
+in the local azimuthal 
+angle $\phi$, the center of the camera and the source position
+would always have the same zenith angle $\Theta$. Since the reconstruction
+efficiency of showers mainly depends on $\Theta$, this may be an
+advantage of defining $\Delta \beta$ in this way.
 
 The wobble mode has to be understood as an alternative to taking on-
@@ -107,4 +117,7 @@
 that one is taking on-data only, from which also the 'off-data' have to be
 obtained by some procedure.
+
+Open questions : - how should $\Delta \beta$ be defined 
+                 - how big should $\Delta \beta$ be chosen 
 
 \item Pedestals :\\
@@ -832,5 +845,5 @@
 \begin{thebibliography}{xxxxxxxxxxxxxxx}
 \bibitem{fegan96}D.J.Fegan, Space Sci.Rev. 75 (1996)137
-\bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 1 (1985) 155
+\bibitem{hillas85}A.M.Hillas, Proc. 19th ICRC, La Jolla 3 (1985) 445
 \bibitem{konopelko99}A.Konopelko et al., Astropart. Phys. 10 (1999)
 275