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Phase II Checklist

  • Guider:
    • When using PWFS2 the guide star must not be too close to the center or the probe arm may vignette the detector on some of the offset positions. This may be acceptable if the target is small or off-center, but it should be avoided if possible.
    • When using PWFS2 the guide star must not be too close to the edge or it may be unreachable in some offset positions. This can be checked by using the Position Editor to visualize the probe positions for each offset step.
    • The guide state in the offset iterator should be "guide" for all science dithers, and typically "freeze" for the sky dithers. Sky dithers can be guided if they are close enough to reach with the same guide star and if not offsetting frequently, as the guide probe moves rather slowly and therefore waiting for the guider will incur extra overheads.

  • OT Setup:
    • Acquisitions are typically not necessary for f/6 imaging as the field of view is quite large (120"). Acquisitions are recommended to get the best centering on f/32 imaging.
    • The sky background (which refers to optical sky background) should be set to "Any" for almost all near-IR (1-5 microns) observations.
    • The water vapor should be set to "Any" for 1-3 micron observations and carefully considered for observations at wavelengths >3 microns.
    • An extra offset is recommended to compensate for the first frame effect. This extra offset may be at the beginning (historically called a "dummy" frame) or simply added at the end.
    • If there is a chance that any source will saturate the PI should include a note telling the observer what to do. Possible actions include: 1) nothing, 2) stop the observation and request feedback from the PI, 3) decrease the exposure time, 4) decrease the exposure time and increase the number of coadds. Decreasing the exposure time may require changing the read mode and/or array ROI, so the note should state whether these changes are allowed.
    • If the target will not be obvious the PI should include a finder chart or a note stating that centering is not important.
    • If the observing sequence is non-standard the PI should include a note so that the observer is not caught off guard (and to prevent the observer from trying to "fix" the observation).
    • Offset iterators should typically be located below sequence iterators (which change the instrument configuration) since the telescope offsets much more quickly than the instrument can reconfigure (e.g. change filters).

  • Instrument Configuration:
    • The focal plane mask must be set to "imaging" since this mechanism has failed and is now locked in this position.
    • The beam splitter must be set to f/6 (also locked in position), although all the cameras may still be used for imaging.
    • The exposure times should be appropriate. This means longer than the minimum allowed by the read mode and ROI, and short enough that saturation does not occur and the background has not changed too much. See the tables of minimum and maximum exposure times and the NIRI ITC if unsure.
    • The detector read-mode, well-depth and subarray-size should be appropriate for the science goals and integration times. Typically deep-well is only used for thermal (L & M) imaging, and subarrays are only used to achieve very short exposure times.
    • The detector subarray size should not change between the science target, calibrations and standards.
    • The "Spectroscopy 1024x512" subarray size should not be used.

  • Standards and Calibrations:
    • Flats should be defined for all imaging at wavelengths < 3.3 microns. Note that these are taken during the day and will therefore not be charged to the program.
    • Flat parameters must match those in the NIRI library.
    • Photometric standards should be defined for all CC50 imaging programs, and are also recommended for CC70 programs in the case where the observations are executed under photometric conditions.
    • Photometric standards should be chosen so that they will be observed at approximately the same airmass as the science target. When in doubt, use the photometric standard search to find the best options.
    • Photometric standards should be fainter than 12th magnitude for broad-band f/6 imaging.