Large Monolithic Imager (LMI)

The Large Monolithic Imager (LMI) is the LDT’s workhorse camera, and contains the largest CCD that can be made using current manufacturing techniques.  Covering a field of view 12.3′ square, the CCD format is 6144×6150 pixels, each 15 µm square, with base pixel scale 0.120″/pixel.  The instrument is typically operated binned 2×2 (0.24″/pixel), but the user may select the binning factor of their choice.

LMI’s two filter wheels hold 17 filters (plus two open slots and a dark blank).  Available filters are: Johnson-Cousins UBVRI, SDSS u’g’r’i’z’, VR, HalphaOn, HalphaOff, OIII, Y-ish (a UKIDSS/WFCAM Y, extended in the red) filters, and three Wolf-Rayet emission line filters (WC, WN, and CT).  A set of 11 narrow band comet filters is also available, but anyone wishing to use the filters should contact Dave Schleicher (dgs at lowell dot edu) first.  The comet filters are 4″ rounds, and will vignette the LMI field of view.  Filter swaps will only be done during daytime hours to minimize risk.  Users must specify their needed filters in their proposals to ensure the necessary filters are mounted for their observing run.

Phil Massey is Principal Investigator for the instrument. Funded by a grant from the National Science Foundation, the LMI was commissioned in 2013 and 2014.

See a sample of pictures at the LMI image gallery.

See LMI on Confluence

Specifications

  • Detector:  e2v CCD231-SN-10382-14-01: 6144×6160 15µm pixels (92.16 mm x 92.40 mm). (Spec sheet at http://www2.lowell.edu/users/massey/LMI/G5.pdf, although instrumental QE at short wavelengths is better than quoted.)
  • FOV: 12.3′ x 12.3′
  • Pixel Scale: 0.12″/pixel (unbinned), 0.24″/pixel (binned 2×2)
  • Gain: 2.89 e–/ADU (amplifier A, but other amplifiers similar)
  • Read Noise: 2.1 ADUs, about 6.0 e– (amplifier A, others similar)
  • Normal Operating Temperature: -120ºC
  • One Bad Column: (1597 when binned 2×2). Bad pixel masks available here (no link yet).
  • Linearity: All 4 amplifiers are linear to <1.5% over the full data range.
  • Exposure Midtime: Actual mid-time of exposure=[(UTCSTART + 2.05 sec)+(UTCEND-0.19 sec)]/2.
  • Example Count Rates:
    • For an object U=B=V=R=I=20th at an airmass of 1.0, integrated over a stellar profile:
    • U: 70 e–/sec                           SDSS u’: 130 e–/sec
    • B: 610 e–/sec                         SDSS g’: 715 e–/sec
    • V: 595 e–/sec                         SDSS r’: 690 e–/sec
    • R: 575 e–/sec                         SDSS i’: 500 e–/sec
    • I: 410 e–/sec                           SDSS z’: 310 e–/sec
    • VR: 890 e–/sec                      Y-ish 19 e–/sec
    • HON: 14 e–/sec                      HOFF: 65 e–/sec
    • OIII: 14 e–/sec                        WC,WN,CT: 32 e–/sec
  • Exposure Time Calculator: Available here.
  • Readout (plus prescan) Times:
    • Unbinned (1×1): 73 sec
    • Standard binning (2×2): 24 sec
    • Highly binned (4×4): 10 sec
  • Recommended settings:
    • Amplifier: A
    • Binning: 2×2
    • Overscan: 32

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