Advice to Observers - 20060128 - Recent Observing Changes (DPC)

January 28, 2008 - Notes by DPC

Changes in Mimir observing modes:

  1. Well depths are deeper. Saturation limits are now about 7,500 ADUs. Do not exceed this value for pixels expected to return good data
  2. Scripts have been moved. In the LOIS GUI,
    1. type "cd tcl.mimir" to move into the directory containing the Mimir scripts
    2. type "source mwbfilt.tcl" to load the filter definitions
    3. click the "Show User Buttons" button at top right of the LOIS GUI. This will put up a GUI with buttons for each filter combination for Mimir.
      1. NOTE: this does *NOT* set the slit and decker plates
  3. To insert the decker, in the yggdrasil window, type "plate d 152"
    1. To remove the decker, type "plate d home"
  4. To insert the 2-pixel (F/5) spectroscopy slit, in the yggdrasil window, type "plate s 91"
    1. check the location of the slit. If it is not at/very near column 511/512, increase or decrease the "plate s" argument by one unit
    2. to remove the slit plate, type "plate s home"
  5. The autoguider is quite ill -- the Y-axis (~Dec) is balky and often does not move at all. Hopefully this will get fixed soon, but for now, slit dithering is by hand only.
  6. LM Spectroscopy is working - we were able to obtain useful LM spectroscopy recently and so consider it "commissioned"
    • The image below is the top half of the difference of a spectral image dithered pair (to remove the background). The spectrum runs from about 2.8 microns on the left, through the atmospheric absorption trough shortward of L, then through the L-band, to the atmospheric trough between L and M, and finally (weakly) through the M-band region, ending at about 5.5 microns at the far right. The spectrum shown is for an object of about 1st magnitude in these bands, and this is a single 0.2 sec exposure.

    1. subframing is necessary (subframe say 850x200)
      1. be sure to obtain bias, dark, and flats with the same subframing configuration
    2. existing slit dither scripts move too far along the slit to stay on the subframed image
      1. we had good luck in putting the spectrum across the middle of the bottom half of the image, then offsetting 60 arcsec to put the spectrum in the middle of the top half of the image. While not as robust as full slit dithering, this was adequate considering the illness of the guider.
    3. exposure times ranged from 0.0 to about 0.5 sec.