LOCI mounted on LT, with SPRAT in background.
Image ©2025 Chloé Miossec.

LOCI

Introduction

The Liverpool Optical Compact Imager (LOCI) is a backup instrument for IO:O. It is cooled with an onboard peltier cooler, in contrast to IO:O's external crytotiger that is connected to the instrument by coolant pipes.

Status

ONLINE

Specifications

  • Andor Ikon-L 936 Camera
  • 2048 x 2048 E2V CCD
  • Operating temperature 203K
  • 13.5 x 13.5 micron pixels giving 27.6 x 27.6 mm detector
  • BV sensor (not deep depletion)
  • Peak counts ~65000
  • Built-in iris shutter
    • NB due to differential exposure caused by finite speed of iris petals,
      we recommend a minimum exposure time of 5 seconds
  • Filter Wheel
    • 5-position Starlight Express
    • Baader Planetarium Sloan filters u'g'r'i'z' 50.4mm diameter
  • Optional foreoptics (currently not installed)
    • Edmund Optics 300mm focal length achromatic doublet
    • VIS-NIR coating
    • lens tube 3 inch (76 mm) diameter
  • Pixel scale (no foreoptics) = 0.276" per 2x2 binned pixel
  • Field of view (no foreoptics) = 4.7 x 4.7 arcmin

  • Readout Speed = 2 seconds with 2x2 binning
  • Gain = 1.87 e/ADU
  • Read noise = 7.5 electrons
  • Mean bias level = 300
  • Median dark current = 1 count (~2e) per 100s at -70C

  • Zeropoint magnitudes per one photoelectron in each filter (no foreoptics)
    • SDSS-U = 19.7
    • SDSS-G = 24.5
    • SDSS-R = 24.5
    • SDSS-I = 24.0
    • SDSS-Z = 22.7

Sensitivity

Exposure times should be similar to IO:O, although may need to be increased by ~50% in the u' and z' bands.

Pipeline

A basic data pipeline is in place which carries out debiasing and flatfielding. No correction for fringing in the i' and (particulary) z' bands is made.