News about chopping for SM & VM observers

Chopping with counter-chopping

Chopping (with counter chopping) is mandatory for M-band observations with NaCo in imaging mode.

For all other filters / mode, an autojitter pattern performs exactly as well.

Chopping with counter-chopping does work but under a number ofrestrictions, due to physical limitations of the system, and which arestated here.

  • Chopping can only work on targets using a bright AO reference star, i.e. allowing the AO to correct at >= 50Hz.
    Typically that would mean V <=15 or K <=10.
  • The quality if the counter-chopping is at best when the chop throw is <= 10".
    Greater chop throw can be accepted if the idea is to have one of the beam out of the field of view.
Due to these limitations, as of P77, only OBs respecting these limits will be accepted.