Equivalent and focal length values

[aleberti]

This discussion started in cta-observatory/magic-cta-pipe#136, and continued in #57 . This was discussed today (2023-04-26) and others two discussions were linked:

• Revert change of MAGIC focal length to 17.0 m lst-sim-config#47
• https://github.com/cta-observatory/lst-sim-config/blob/sim-telarray/MAGIC1.cfg

In particular:

focal_length        = 1697.    % Focal length for camera.
effective_focal_length = 1821.2 % corrected for 1.0713 aberration 

and the second number is 17.0*1.0713. It seems that the updated setting on focal_length was not used at the end in LSTProd2, so that is why simtel files now have 17.0m as focal_length and not 16.97m.

In any case, since there is already a small mismatch in simulations (between the MAGIC and MAGIC+LST1 ones), we decided for the moment to put the right values in the MAGICEventSource:

focal_length        = 1697.    % Focal length for camera.
effective_focal_length = 1821.2 % corrected for 1.0713 aberration 

then in the next MAGIC+LST1 production, when the right values will be used, the mismatch between settings in real and MC data will be gone.