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Mid-IR Phase I/II Checklist

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To demonstrate technical feasibility in your proposal, and to speed acceptance of your phase II file, you may wish to consider the following checklist. When setting up your programme in the OT, please download and look at the example observations in the OT libraries.

  • Field of view:
    • Does the source fit within the 32"x24" Michelle or 29"x22" T-ReCS field of view, and is it smaller in at least one dimension than the current 15 arcsec maximum chop throw? If not, have you specified a mosaicing strategy and included the proper overheads in your time estimate?

  • Chopping and nodding (these issues are especially important in crowded fields or if mosaics are to be constructed):
    • Have you specified a chop throw consistent with the currently allowed maximum of 15 arcsec?
    • Is there a preferred chop direction? For brighter targets one should chop at 45 degrees (or some other intermediate angle) rather than either 0 or 90 degrees, or completely off-chip (to minimise the effect of level drop phenomena).

  • Telescope peripheral wavefront sensors:
    • Have you specified one or more guide stars for the peripheral wavefront sensor (PWFS2) of adequate brightness? Stars should be R<13 mag for use with chopping. The guide star must be within the 7' PWFS patrol field and the probe arm must not vignette the science field at any chop/nod position. This can be checked using the OT position editor.

  • Desired observing conditions:
    • What are the loosest observing condition constraints (cloud cover, precipitable water vapour and image quality) under which your programme can be scheduled? Please note that polarimetry and Q-band observations are particularly sensitive to cloud cover and high water vapour column, and that the image quality constraints refer to the zenith, not the airmass at which your target is observed.
    • Did you run your time calculations with the ITC using the same observing conditions as requested in your proposal (or specified in the OT, if you decided to relax them at that stage)? Changes in conditions can make a substantial difference to the total time required to obtain the desired S/N.

  • Astrometry:
    • If accurate astrometry is required, have you specified one or more suitable astrometric standards in your programme, and added extra time in your proposal for this standard to be observed?

  • Photometric, PSF and polarimetry calibrations:
    • What photometric calibration accuracy is required for your program?
    • Are the baseline calibrations sufficient, or will special standard star observations be required?
    • Have you included observing time (and overheads) for any special calibrations in your time estimate?
    • What are the PSF calibration requirements of your program? If highly accurate knowledge of the PSF is needed, frequent observations of standards need to be carefully planned. Are these requirements described in your proposal and any extra time included in your time request? PSF calibration star observations must be explicitly defined in the OT at phase II in the same way as a science observation.
    • Unpolarised standard stars are part of the baseline calibrations for polarimetry, but polarised standards are not. Should these be required, the necessary time must be requested in your proposal.

  • Spectroscopic calibrations:
    • Do you require calibration observations beyond the telluric standard star provided by the baseline calibrations? Time for e.g. spectrophotometric standards, if required, must be requested and justified in your proposal. Note that even for baseline calibrations we require that two telluric standards be provided in the OT to roughly match the airmass of the target if observed before or if observed after. These guidelines may help you choose appropriate objects.

  • Flatfields and bias frames:
    • Flatfields are not taken for mid-IR imaging nor for T-ReCS spectroscopy, but for Michelle spectroscopy we now require that flats and biases be included in observing sequences; see the Michelle OT library for examples.
  • Observing time:
    • Observing overheads in the mid-IR can be considerable. Please make sure that they are included in your time request; see each instrument's Overheads page for more details.

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