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Imaging

The properties of NIRI in imaging mode are summarized in the following sections. Three selectable fields of view and pixel scales are available. With adaptive optics NIRI is available at f/32 for J-L' imaging (but see caveats for L'), and at f/14 for imaging out to 2.5 microns due to the increased thermal background. Imaging at L' is impossible at f/6 and only sometimes possible at f/14. The narrow band L filters (e.g., the PAH filter, Br alpha) can be observed at f/32, f/14, and f/6. M' imaging is only possible at f/32.

NIRI occasionally suffers from vertical striping and shifts in DC levels which can both vary from quadrant to quadrant. Details can be found here.

First Frame Issue:  When starting exposures after changing the detector configuration (well-depth, read mode, exposure time, etc) the background or dark current level is different. Thus The first exposure of every new sequence will show poor background subtraction and should be rejected (see the detector array section for more detail). We recommend sequences include an extra step (either at the beginning, or repeat the first position at the end, or simply include N+1 different offsets). Short exposures that are not background limited (e.g., standard star measurements) are usually fine without an extra exposure. These bad first images ARE included in the distributed data, so care should be taken to review and reject them from all sequences (science, flats and darks) as necessary.


  • Pixel scales, Field of View, and Field Orientation
  • Imaging filters
  • Exposure times
  • Zero points
  • Observing Strategies
  • Detector array
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