Frequently Asked Questions related to VISIR

•Do I need to supply a standard star OB for my imaging observation?


Answer: For imaging with VISIR, ESO will provide an observation of a standard star as part of the calibration plan. For imaging, this calibrator will be taken within three hours of the science observation at low airmass. This calibrator will be suitable to obtain an accurate zero-point for the photometric calibration. However, it may not have the S/N, or be sufficiently matched in colour and observing conditions to your science observation to be used for more detailed calibration purposes such as deconvolution. If this is a requirement for your programme, you are advised to supply an additional calibrator OB for each science OB. The time required to execute these additional calibrations will be charged to your programme.


•Do I need to supply a standard star OB for my spectroscopy observation?


Answer: For spectroscopy with VISIR, ESO only provides observations of a telluric standard as part of the standard calibration plan for observations in the low-resolution spectroscopy mode. This telluric standard star will be taken directly preceding or following the science OB and will be taken at an airmass that is close to that of the science target. Please note that for spectroscopy observations in the medium-resolution mode, the high-resolution longslit mode, or the high-resolution cross-dispersed mode, ESO does not provide telluric standard star observations as part of the standard calibration plan. If telluric standards are required, one telluric standard star OB per science OB will have to be prepared and submitted by the user. The time required to execute these calibrator OBs will be charged to your programme.


Where can I find calibrator stars that are suitable for VISIR?


Answer: A good list of calibrator stars for VISIR can be found here. For imaging, calibrator stars should be between 1 and 10 Jy for observations in the N-band, and brighter than a few Jy for observations in the Q-band. For low-resolution spectroscopy, the calibrators should be brighter than a few Jy and be located as close as possible on the sky to the science target. For medium-and high resolution spectroscopy, the calibrator should be brighter than 10 Jy or so. As the choice of such bright calibrators may be limited, larger differences in airmass between the science target and the telluric standard may have to be accepted.