Offered Imaging modes
Imaging is offered with NaCo with a serie of broad and narrow (NB) band filters covering the range 1.0 to 5.0 μm. The complete list of filters and their characteristics is available.
For wavelength longer than 2.5 μm, chopping with counter-chopping is offered (Lp nd Mp). Its use is compulsory for M-band imaging.
For all other filters with wavelength longer than 2.5 μm obervations can be perfomred without
chopping. However, in order to get good sky subtraction in Lp, chopping is recommended.
The constraints for chopping have been changed: the chopping throw can be as large as 20 arcsec, but users are adviced to use the minmum value as possble. The magnitude limits for chopping applications have been tightened: chopping
can be done with AO reference targets two mgnitudes brighter than the brightness limits typically needed for NAOS (se below).
As of p82 imaging is also ofered in combination with pupil tracking and cube mode.
Simultaneous Differential Imaging (SDI+) is also offered. SDI+ can be also combined with coronagraphy by means of a 4 quadrants phase mask (4QPM_H). SDI+ shows the same performance as the old SDI but with a larger FoV, 8x8 arcsec.
| Band | J | H | Ks | L' | M' |
|---|---|---|---|---|---|
| FWHM (mas) | 32 | 42 | 56 | 98 | 123 |
| Sky background (mag) | 16.0 | 14.0 | 13.0 (1) | 3.0 | -0.5 |
| Limiting magnitude (2) | 24.05 | 24.05 | 23.35 | 18.55 | 15.15 |
(1): For the N90C10 dichroic, the background in Ks is 11 mag/square arcsecond
(2): 5 sigma in 1 hour using a V=11.5 mag. reference 10" away from the source with a visible seeing of 0.8".
These limits are valid for point sources (calculated over apertures of 1.25xFWHM radius). For NB filters, subtract 2 to 3 magnitudes.
Fabry Perot information
For technical reasons the Fabry-Perot mode will not be offered in P82.
SDI information
The SDI+ mode (SDI+) of CONICA obtains 4 images through 3 narrow band filters simultaneously. Two images are taken outside the 1.6 μm methane feature (at 1.575 and 1.60 μm) and two images are taken inside the feature (both at 1.625 μm). All filters have a FWHM of 25nm. The platescale of the SDI+ camera is 17.32mas/pixel. The FoV of each quadrant is 8x8 arcsec, even though this may be slightly smaller due to a tilt of the images.
Experienced SDI+ users advise to set the OFFSET dither box size to no more than 0.4x0.4" (enough to get rid of bad pixels).