Doc:
Issue
Date
Page
VLT-MAN-ESO-14650-4942
P96
24.06.2015
118 of 161
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
7.1.2 Examples of position angles and offsets
TEL.ROT.OFFANGLE is the keyword in the acquisition templates to set up the slit position
angle on sky. A value of 9999 (default) means that the parallactic angle is used.
The parallactic angle is not followed during the exposure, the system uses the parallactic
angle at the start of the OB. If another PA is defined, the telescope will follow this angle on
sky.
h) Examples of position angles
If the user needs a position angle of +45 degrees, it is just needed to enter + 45 degrees in
the acquisition template. If the user needs a position angle of 315 degrees, it is needed to
enter in the acquisition template an angle of –45 degrees (=315-360).
The convention is to use angles from 0 to +180 degrees and from 0 to –180 degrees.
PA=0 degree PA=+45 degrees PA=
45 or +315 degrees
N
E
N
E
N
E
+45
-45