• Frame Type SCIENCE_CORONOGRAPHY
• DPR.TYPE OBJECT; SKY
• DPR.TECH CORONOGRAPHY,JITTER; CORONOGRAPHY,JITTER,PT; CORONOGRAPHY,JITTER,CUBE; CORONOGRAPHY,JITTER,CUBE,PT

description: The coronographic observations are obtained using the Lyot-type coronograph with a circular focal plane mask and undersized pupil plane mask inserted in the optical axis. Five masks are available: two opaque masks with diameter 0.7 arcsec (INS.OPTI1.NAME=C_0.7) and 1.4 arcsec (INS.OPTI1.NAME=C_1.4), a semi-transparent mask with diameter 0.7 arsec (INS.OPTI1.NAME=C_0.7_sep_10), and two four quadrant phase masks, one optimized for K-band (INS.OPTI1.NAME=4QPM_K) and the other in H-band (INS.OPTI1.NAME=4QPM_H). The coronographic observations can be also obtained in the pupil tracking (PT) and/or cube (CUBE) modes.

For more information regarding coronography, available masks and their characteristics consult the NACO User Manual

In addition (as of P86), a new Apodizing Phase Plate (APP) (see APP coronography) has been installed in the pupil plane and is operated at 4.05 um (NB and IB filters) just like direct imaging.

	This is an example of the coronographic observation using the C_0.7 mask. The mask's diameter is 0.7 arcsec, it is 100% opaque held in place by wires.
	This is an example of the coronographic sky observation using the 4QPM_K mask. This 4 quadrant phase mask is optimized for a wavelength of 2.18 um. It's FOV is 13 x 13 '' and the diameter is that of the central Lyaot spot.
	This is an example of the coronographic sky observation using the semi-transparent, C_0.7_sep_10 mask, with camera S27. The semi-transparent mask is placed on the transparent plate. It's transmissivity is measured to about 3.5x10(-3).

This mode is offered in service and visitor mode. It is not supported by the pipeline.

calibrations:The calibration plan includes

• standard detector darks with readout mode and DIT matching the one used for science;
• standard lamp and/or sky flat fields without the focal plane mask;
• users are offered possibility to design the night time flat fields for the C_0.7_sep_10 and 4QPMs masks to avoid problems with instrument flexure;
• nightly zero points;