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STIS Instrument Handbook
Chapter 6: Exposure Time Calculations

Chapter 6: Exposure Time Calculations

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Chapter Contents

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STIS Instrument Handbook
- • Acknowledgments
- Chapter 1: Introduction
  - • 1.1 Overview
  - • 1.2 Introduction to the Handbook
  - • 1.3 Handbook Layout
  - • 1.4 Proposal Preparations and Observations with STIS
  - • 1.5 The Help Desk at STScI
  - • 1.6 The STIS Web Pages and Support Information
  - • 1.7 Non-proprietary STIS Data
- Chapter 2: Special Considerations for Cycle 32
  - • 2.1 STIS Repair and Return to Operations
  - • 2.2 Summary of STIS Performance Changes Since 2004
  - • 2.3 New Capabilities for Cycle 32
  - • 2.4 Use of Available-but-Unsupported Capabilities
  - • 2.5 Choosing Between COS and STIS
  - • 2.6 Scheduling Efficiency and Visit Orbit Limits
  - • 2.7 MAMA Scheduling Policies
  - • 2.8 Prime and Parallel Observing: MAMA Bright-Object Constraints
  - • 2.9 STIS Snapshot Program Policies
- Chapter 3: STIS Capabilities, Design, Operations, and Observations
  - • 3.1 Instrument Capabilities
  - • 3.2 Instrument Design
  - • 3.3 Basic Instrument Operations
  - • 3.4 Designing STIS Observations
- Chapter 4: Spectroscopy
  - • 4.1 Overview
  - • 4.2 First-Order Long-Slit Spectroscopy
  - • 4.3 Echelle Spectroscopy in the Ultraviolet
  - • 4.4 Objective Prism Spectroscopy
- Chapter 5: Imaging
  - • 5.1 Imaging Overview
  - • 5.2 Optical CCD Imaging
  - • 5.3 Ultraviolet Imaging with the MAMA Detectors
  - • 5.4 Neutral Density Filters
- Chapter 6: Exposure Time Calculations
  - • 6.1 Overview
  - • 6.2 Determining Count Rates from Sensitivities
  - • 6.3 Throughput and Sensitivity
  - • 6.4 Computing Exposure Times
  - • 6.5 Detector and Sky Backgrounds
  - • 6.6 Tabular Sky Backgrounds
  - • 6.7 Extinction Correction
  - • 6.8 Exposure Time Examples
- Chapter 7: Feasibility and Detector Performance
  - • 7.1 STIS Detectors
  - • 7.2 The CCD
  - • 7.3 CCD Operation and Feasibility Considerations
  - • 7.4 The MAMA Detectors
  - • 7.5 MAMA Operation and Feasibility Considerations
  - • 7.6 MAMA Spectral and Spatial Offsetting
  - • 7.7 MAMA Bright Object Limits
- Chapter 8: Target Acquisition
  - • 8.1 Introduction
  - • 8.2 STIS Onboard CCD Target Acquisitions - ACQ
  - • 8.3 Onboard Target Acquisition Peakups - ACQ PEAK
  - • 8.4 Determining Coordinates in the International Celestial Reference System (ICRS) Reference Frame
  - • 8.5 Acquisition Examples
  - • 8.6 STIS Post-Observation Target Acquisition Analysis
- Chapter 9: Overheads and Orbit-Time Determination
  - • 9.1 Overview
  - • 9.2 STIS Exposure Overheads
  - • 9.3 Orbit Use Determination Examples
- Chapter 10: Summary and Checklist
  - • 10.1 Phase I Proposing
  - • 10.2 Phase II - Scheduling Approved Observations
- Chapter 11: Data Taking
  - • 11.1 Basic Operating Modes
  - • 11.2 Exposure Sequences and Contemporaneous Calibrations
  - • 11.3 Patterns and Dithering
  - • 11.4 Fixing Orientation on the Sky
  - • 11.5 Target Positioning
- Chapter 12: Special Uses of STIS
  - • 12.1 Slitless First-Order Spectroscopy
  - • 12.2 Long-Slit Echelle Spectroscopy
  - • 12.3 Time-Resolved Observations
  - • 12.4 Observing Too-Bright Objects with STIS
  - • 12.5 High Signal-to-Noise Ratio Observations
  - • 12.6 Improving the Sampling of the Line Spread Function
  - • 12.7 Considerations for Observing Planetary Targets
  - • 12.8 Special Considerations for Extended Targets
  - • 12.9 Parallel Observing with STIS
  - • 12.10 Coronagraphic Spectroscopy
  - • 12.11 Coronagraphic Imaging - 50CORON
  - • 12.12 Spatial Scans with the STIS CCD
- Chapter 13: Spectroscopic Reference Material
  - • 13.1 Introduction
  - • 13.2 Using the Information in this Chapter
  - 13.3 Gratings
    - • First-Order Grating G750L
    - • First-Order Grating G750M
    - • First-Order Grating G430L
    - • First-Order Grating G430M
    - • First-Order Grating G230LB
    - • Comparison of G230LB and G230L
    - • First-Order Grating G230MB
    - • Comparison of G230MB and G230M
    - • First-Order Grating G230L
    - • First-Order Grating G230M
    - • First-Order Grating G140L
    - • First-Order Grating G140M
    - • Echelle Grating E230M
    - • Echelle Grating E230H
    - • Echelle Grating E140M
    - • Echelle Grating E140H
    - • PRISM
    - • PRISM Wavelength Relationship
  - 13.4 Apertures
    - • 52X0.05 Aperture
    - • 52X0.05E1 and 52X0.05D1 Pseudo-Apertures
    - • 52X0.1 Aperture
    - • 52X0.1E1 and 52X0.1D1 Pseudo-Apertures
    - • 52X0.2 Aperture
    - • 52X0.2E1, 52X0.2E2, and 52X0.2D1 Pseudo-Apertures
    - • 52X0.5 Aperture
    - • 52X0.5E1, 52X0.5E2, and 52X0.5D1 Pseudo-Apertures
    - • 52X2 Aperture
    - • 52X2E1, 52X2E2, and 52X2D1 Pseudo-Apertures
    - • 52X0.2F1 Aperture
    - • 0.2X0.06 Aperture
    - • 0.2X0.2 Aperture
    - • 0.2X0.09 Aperture
    - • 6X0.2 Aperture
    - • 0.1X0.03 Aperture
    - • FP-SPLIT Slits 0.2X0.06FP(A-E) Apertures
    - • FP-SPLIT Slits 0.2X0.2FP(A-E) Apertures
    - • 31X0.05ND(A-C) Apertures
    - • 0.2X0.05ND Aperture
    - • 0.3X0.05ND Aperture
    - • F25NDQ Aperture
  - 13.5 Spatial Profiles
    - • First-Order Spatial Profiles
    - • Echelle Spatial Profiles
  - 13.6 Line Spread Functions
    - • First-Order Line Spread Functions
    - • Echelle Line Spread Functions
  - • 13.7 Spectral Purity, Order Confusion, and Peculiarities
  - • 13.8 MAMA Spectroscopic Bright Object Limits
- Chapter 14: Imaging Reference Material
  - • 14.1 Introduction
  - • 14.2 Using the Information in this Chapter
  - 14.3 CCD
    - • CCD Clear Imaging - 50CCD
    - • CCD Long-Pass Imaging F28X50LP
    - • F28X50OIII - CCD
    - • F28X50OII - CCD
    - • 50CORON - Clear CCD
  - 14.4 NUV-MAMA
    - • 25MAMA - NUV-MAMA, Clear
    - • F25ND3 - NUV-MAMA
    - • F25ND5 - NUV-MAMA
    - • F25NDQ - NUV-MAMA
    - • F25QTZ - NUV-MAMA, Longpass
    - • F25SRF2 - NUV-MAMA, Longpass
    - • F25MGII - NUV-MAMA
    - • F25CN270 - NUV-MAMA
    - • F25CIII - NUV-MAMA
    - • F25CN182 - NUV-MAMA
  - 14.5 FUV-MAMA
    - • 25MAMA - FUV-MAMA, Clear
    - • 25MAMAD1 - FUV-MAMA Pseudo-Aperture
    - • F25ND3 - FUV-MAMA
    - • F25ND5 - FUV-MAMA
    - • F25NDQ - FUV-MAMA
    - • F25QTZ - FUV-MAMA, Longpass
    - • F25QTZD1 - FUV-MAMA, Longpass Pseudo-Aperture
    - • F25SRF2 - FUV-MAMA, Longpass
    - • F25SRF2D1 - FUV-MAMA, Longpass Pseudo-Aperture
    - • F25LYA - FUV-MAMA, Lyman-alpha
  - • 14.6 Image Mode Geometric Distortion
  - • 14.7 Spatial Dependence of the STIS PSF
  - • 14.8 MAMA Imaging Bright Object Limits
- Chapter 15: Overview of Pipeline Calibration
  - • 15.1 Pipeline Processing Overview
  - • 15.2 How Phase II Parameter Choices Affect Calibration
  - • 15.3 More Detailed Information
- Chapter 16: Accuracies
  - • 16.1 Summary of Accuracies
- Chapter 17: Calibration Status and Plans
  - • 17.1 Introduction
  - • 17.2 Ground Testing and Calibration
  - • 17.3 STIS Installation and Verification (SMOV2)
  - • 17.4 Cycle 7 Calibration
  - • 17.5 Cycle 8 Calibration
  - • 17.6 Cycle 9 Calibration
  - • 17.7 Cycle 10 Calibration
  - • 17.8 Cycle 11 Calibration
  - • 17.9 Cycle 12 Calibration
  - • 17.10 SM4 and SMOV4 Calibration
  - • 17.11 Cycle 17 Calibration Plan
  - • 17.12 Cycle 18 Calibration Plan
  - • 17.13 Cycle 19 Calibration Plan
  - • 17.14 Cycle 20 Calibration Plan
  - • 17.15 Cycle 21 Calibration Plan
  - • 17.16 Cycle 22 Calibration Plan
  - • 17.17 Cycle 23 Calibration Plan
  - • 17.18 Cycle 24 Calibration Plan
  - • 17.19 Cycle 25 Calibration Plan
  - • 17.20 Cycle 26 Calibration Plan
  - • 17.21 Cycle 27 Calibration Plan
  - • 17.22 Cycle 28 Calibration Plan
  - • 17.23 Cycle 29 Calibration Plan
  - • 17.24 Cycle 30 Calibration Plan
  - • 17.25 Cycle 31 Calibration Plan
- Appendix A: Available-But-Unsupported Spectroscopic Capabilities
  - • A.1 Introduction
  - • A.2 Full Aperture Complement
  - • A.3: Additional Available-but-Unsupported Options
- • Glossary