Large Monolithic Imager (LMI)

LDT Facility Instrument – Always Available

Mounting Port:  Instrument Cube – Through Port

Manual:  LMI User Manual (30 September 2020)

Instrument Scientist:  Phil Massey (massey at lowell dot edu)

The Large Monolithic Imager (LMI) is the DCT'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 6144x6150 pixels, each 15 µm square, with base pixel scale 0.120"/pixel.  The instrument is typically operated binned 2x2 (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.

Instrument Quick Facts:

Detector:  e2v CCD231-SN-10382-14-01: 6144x6160 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 2x2)

Gain: 2.89 e^-/ADU (amplifier A, but other amplifiers similar)

Readnoise: 2.1 ADUs, about 6.0 e^- (amplifier A, others similar)

Normal Operating Temperature: -120ºC

One Bad Column: (1597 when binned 2x2). 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.  See write-up here.

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 Sloan u: 130 e/sec

B: 610 e/sec Sloan g: 715 e/sec

V: 595 e/sec Sloan r: 690 e/sec

R: 575 e/sec Sloan i: 500 e/sec

I: 410 e/sec Sloan 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 (1x1): 73 sec

Standard binning (2x2): 24 sec

Highly binned (4x4): 10 sec

Recommended settings:

{ Amplier: A

{ Binning: 2 2

{ Overscan: 32