MODS Instrument Manual Document Number: OSU-MODS-2011-003 Version: 1.2.4 Date: 2012 February 7 Prepared by: R.W. Pogge, The Ohio State University MODS Instrument Manual Distribution List Recipient Institution/Company Number of Copies Richard Pogge The Ohio State University 1 (file) Chris Kochanek The Ohio State University 1 (PDF) Mark Wagner LBTO 1 (PDF) Dave Thompson LBTO 1 (PDF) Olga Kuhn LBTO 1 (PDF) Document Change Record Version Date Changes Remarks 0.1 2011-09-01 Outline and block draft 1.0 2011-12 Too many to count... First release for comments 1.1 2012-01 Numerous comments… First-round comments 1.2 2012-02-07 LBTO comments First Partner Release 2 MODS Instrument Manual OSU-MODS-2011-003 Version 1.2 Contents 1 Introduction .................................................................................................................. 6 1.1 Scope .......................................................................................................................... 6 1.2 Citing and Acknowledging MODS ............................................................................ 6 1.3 Online Materials ......................................................................................................... 6 1.4 Acronyms and Abbreviations ..................................................................................... 7 2 Instrument Characteristics .......................................................................................... 8 2.1 Instrument Configurations ........................................................................................ 11 2.2 Instrumental Throughput .......................................................................................... 11 2.2.1 Imaging Throughput ......................................................................................... 11 2.2.2 Grating Mode Spectral Throughput .................................................................. 12 2.2.3 Prism Mode Spectral Throughput .................................................................... 13 2.3 Filters ........................................................................................................................ 13 2.3.1 Science Camera Filters ..................................................................................... 13 2.3.2 AGw Guide Camera Filters .............................................................................. 16 2.4 Dichroic .................................................................................................................... 17 2.5 Gratings and Prisms .................................................................................................. 18 2.5.1 Reflection Gratings ........................................................................................... 19 2.5.2 Double-Pass Prisms .......................................................................................... 19 2.6 CCD Detectors .......................................................................................................... 20 2.6.1 Basic Properties ................................................................................................ 20 2.6.2 Exposure Overheads ......................................................................................... 21 2.6.3 Quantum Efficiency .......................................................................................... 22 2.6.4 Detector Saturation ........................................................................................... 22 2.6.5 Cross-Talk ........................................................................................................ 24 2.7 Slit Masks ................................................................................................................. 25 2.7.1 Permanent Facility Slit Masks .......................................................................... 25 2.7.2 Custom Masks .................................................................................................. 26 2.7.3 Multi-Slit Mask Field of View ......................................................................... 27 2.8 Calibration Unit ........................................................................................................ 28 2.9 Acquisition, Guiding, & Wavefront Sensing (AGw) Unit ....................................... 29 2.9.1 Guide Star Patrol Field ..................................................................................... 30 2.9.2 Guiding and WFS Star Brightness Limits ........................................................ 31 2.10 Image Motion Compensation System (IMCS) ......................................................... 32 2.11 Camera Shutter ......................................................................................................... 33 2.11.1 Shutter Shading Function ............................................................................. 34 2.11.2 Shutter Lag ................................................................................................... 34 2.12 MODS Data .............................................................................................................. 34 2.12.1 Image Format ................................................................................................ 35 2.12.2 Bias and Flat-Field Structure ........................................................................ 37 2.12.3 Image Quality ............................................................................................... 38 2.12.4 Ghost Images ................................................................................................ 40 3 Observing in the Near-UV to Near-IR ...................................................................... 42 3.1 Atmospheric Transmission ....................................................................................... 42 3.2 Atmospheric Emission .............................................................................................. 42 3 MODS Instrument Manual 3.3 Moonlight and Twilight Impacts .............................................................................. 44 3.4 Differential Atmospheric Refraction ........................................................................ 44 4 Observing with MODS ............................................................................................... 47 4.1 MODS Control Panel ............................................................................................... 47 4.1.1 Setup Screen ..................................................................................................... 48 4.1.2 MODS Dashboard ............................................................................................ 49 4.1.3 Housekeeping Screen ....................................................................................... 53 4.1.4 Utilities Screen ................................................................................................. 53 4.2 MODS Observing Scripts ......................................................................................... 54 4.3 Where do the MODS data go? .................................................................................. 56 4.4 modsDisp Raw Data Display .................................................................................... 58 4.5 modsAlign Interactive Mask Alignment Tool .......................................................... 58 5 MODS Calibration ..................................................................................................... 60 5.1 Calibration Plan ........................................................................................................ 60 5.2 Bias (“Zero”) Images ................................................................................................ 60 5.3 Dark Frames ............................................................................................................. 60 5.4 Flat Fields ................................................................................................................. 61 5.4.1 Imaging Flats .................................................................................................... 61 5.4.2 Grating Spectroscopy Pixel Flats ..................................................................... 62 5.4.3 Spectral Slit Flats .............................................................................................. 63 5.4.4 Twilight Sky Flats ............................................................................................ 63 5.5 Wavelength Calibration (“Comparison Lamps”) ..................................................... 64 5.5.1 Dispersion Solutions ......................................................................................... 64 5.5.2 Calibration Lamp Files ..................................................................................... 65 5.5.3 Prism Mode Wavelength Calibration ............................................................... 65 5.6 Spectrophotometric Standard Stars .......................................................................... 65 5.7 Standard Calibration Scripts ..................................................................................... 67 Appendix A: MODS FITS Headers ...................................................................................... 68 Appendix B: Filter Bandpass Parameters ............................................................................ 74 Appendix C: Wavelength Calibration Lamps ....................................................................