wcc-etc: Exposure Time Calculator for the Lazuli WCC

wcc-etc is the exposure time calculator for the Wide-field Context Camera (WCC) on Lazuli, the flagship instrument of the Schmidt Observatory System. You describe what is on the sky, pick a sensor and filter, and it returns the signal-to-noise ratio, the exposure time that reaches a target SNR, a simulated detector image, a saturation flag, and a plot of any of these.

A hosted web version of the ETC is available at simulators.schmidtobservatorysystem.org/wcc.

Note

New here? Read Installation, then work through Quick start. The Tutorials are Jupyter notebooks that cover each major feature end to end, with their figures and printed numbers saved in place.

What it models

• A scene: a stellar or galaxy template, or a parametric spectrum (blackbody, flat \(F_\nu\) or \(F_\lambda\), power law, emission lines), with an optional host galaxy that may have a Sersic profile, and a sky background (zodiacal light, moon scatter).

• Signal-to-noise from circular-aperture photometry on a rendered image, with the aperture fixed, set by enclosed energy, or optimized for SNR. The older analytic Airy formula is kept for cross-checks.

• The exposure time that reaches a target SNR, including the effect of splitting an exposure into n_reads frames.

• PSFs and images: diffraction-limited Airy PSFs rendered at the source-weighted effective wavelength, polychromatic coadds, bundled Zemax defocus PSFs, custom PSF arrays, telescope jitter, Poisson and read noise, and per-pixel saturation masks.

• Plots: SNR against time, magnitude, aperture or any parameter; peak pixel against time with the saturation ceiling; images, radial profiles, encircled energy and filter curves, in matplotlib and bokeh, under one house style.

Contents

Getting started

• Installation
  • Requirements
  • Install from source (recommended)
  • Using a conda environment
  • Verify the installation
  • Running the test suite
  • Building the documentation locally
• Quick start
  • The mental model
  • 1. Build a scene
  • 2. Create a simulation for a sensor
  • 3. Compute signal-to-noise
  • 4. Invert: exposure time for a target SNR
  • 5. Change parameters and recompute
  • 6. Check saturation
  • 7. Simulate a detector image and plot it
  • Where to go next

User guide

• User guide
  • Concepts and architecture
  • Scenes, sources, and backgrounds
  • Signal-to-noise and exposure time
  • PSFs and image simulation
  • Saturation
  • Plotting

Tutorials

• Tutorials

Reference

• API reference
  • Top-level public API
  • Modules
• Configuration and sensors
  • Sensor strings
  • The configuration files
  • Example: the Sony detector config
  • Example: the telescope config
  • Overriding configuration at runtime
  • Reading configs programmatically
• Changelog
  • v0.1.0 (2026-10-12)

Indices and tables

• Index

• Module Index

• Search Page