News for SM & VM observers
Chopping/counter-chopping
Please note that we are presently experiencing somedifficulties with the choppingand counter-chopping of NACO.
While the problem is under investigation, please be informed that the behaviour of the system is quite erratic and thus difficult topredict.
However, it is advised, in order to improve chances of success, to use a small chop throw (<= 10" - 15" max) and avoid chopping at an angle of 90degrees.
SDI observations
The SDI mask has slid out of position and thus appears rotated byalmost 45 degrees. As a consequence the untilted FOV is smaller thanexpected. (See Fig. 1 for illustration).
Experienced SDI users advise to set the the OFFSET dither box size to no more than 0.2x0.2" (just enough to get rid of bad pixels).
Fig. 1: Illustration of the SDI FOV