desihub · dkirkby · Nov 23, 2017 · Nov 23, 2017 · Nov 23, 2017 · Nov 23, 2017
diff --git a/.travis.yml b/.travis.yml
@@ -77,10 +77,12 @@ matrix:
         - os: linux
           env: SETUP_CMD='build_docs -w'
 
-        # Now try Astropy dev and LTS vesions with the latest 3.x and 2.7.
+        # Try astropy dev version.
         - os: linux
           env: ASTROPY_VERSION=development
                EVENT_TYPE='pull_request push cron'
+
+        # Now try Astropy LTS vesions with the latest 3.x and 2.7.
         - os: linux
           env: PYTHON_VERSION=2.7 ASTROPY_VERSION=lts
         - os: linux
@@ -110,6 +112,13 @@ matrix:
           env: MAIN_CMD='pycodestyle packagename --count' SETUP_CMD=''
 
     allow_failures:
+        # Try astropy dev version.  This current causes some doctests
+        # to fail because they produce the following unexpected output:
+        # Downloading http://maia.usno.navy.mil/ser7/finals2000A.all [Done]
+        # from `simulator = specsim.simulator.Simulator('test')``
+        - os: linux
+          env: ASTROPY_VERSION=development
+               EVENT_TYPE='pull_request push cron'
         # Do a PEP8 test with pycodestyle
         # (allow to fail unless your code completely compliant)
         - os: linux

diff --git a/CHANGES.rst b/CHANGES.rst
@@ -1,9 +1,11 @@
 0.12 (unreleased)
 -----------------
 
-- No changes yet.
+- Scale the dark sky spectrum with airmass.
+- Implement Twilight sky brightness model and integrate with Atmosphere model.
+- Remove obsolete sky_conditions parameter and only read tabulated dark sky.
 
-0.11 (2017-10-10)
+0.11 (2017-11-10)
 -----------------
 
 - Implement fast fiberloss calculator that interpolates GalSim results (#78).

diff --git a/docs/_static/desi_atmosphere.png b/docs/_static/desi_atmosphere.png
diff --git a/docs/_static/desi_moon_atmosphere.png b/docs/_static/desi_moon_atmosphere.png
diff --git a/docs/_static/desi_moon_twilight_atmosphere.png b/docs/_static/desi_moon_twilight_atmosphere.png
diff --git a/docs/_static/desi_twilight_polar.png b/docs/_static/desi_twilight_polar.png
diff --git a/docs/_static/twilight_spectrum.png b/docs/_static/twilight_spectrum.png
diff --git a/docs/config.rst b/docs/config.rst
@@ -117,13 +117,14 @@ multi-HDU FITS file::
 In this case the HDU and columns are identified by their names in the FITS file.
 
 Finally, some tabulated data uses different files to represent different options.
-For example, sky surface brightness tables under different conditions are
+For example, fiberloss tables for different source types are
 specified by replacing the ``path`` node with a ``paths`` node as follows::
 
     paths:
-        dark: dark-sky.csv
-        grey: grey-sky.csv
-        bright: bright-sky.csv
+        # Each path corresponds to a different source type.
+        qso: throughput/fiberloss-qso.dat
+        elg: throughput/fiberloss-elg.dat
+        lrg: throughput/fiberloss-lrg.dat
 
 For additional examples of specifying tabular data, refer to the configurations
 included with this package and described below.
@@ -182,37 +183,67 @@ The following plot summarizes the default DESI atmosphere used for simulations,
 and was created using::
 
     config = specsim.config.load_config('desi')
-    specsim.atmosphere.initialize(config).plot()
+    atm = specsim.atmosphere.initialize(config)
+    atm.plot()
 
 .. image:: _static/desi_atmosphere.png
     :alt: DESI default atmosphere configuration
 
-The default atmosphere has the moon below the horizon. To simulate grey or
-bright conditions, add scattered moon light by :doc:`modifying the relevant
-parameters in the configuration </api>`, or else by changing attributes of the
-initialized atmosphere model. For example::
+The default atmosphere has the moon below the horizon. To add scattered
+moonlight, :doc:`adjust the relevant parameters in the configuration </api>`,
+or change attributes of the initialized atmosphere model. For example::
 
-    atm = specsim.atmosphere.initialize(config)
     atm.airmass = 1.3
     atm.moon.moon_zenith = 60 * u.deg
     atm.moon.separation_angle = 50 * u.deg
     atm.moon.moon_phase = 0.25
     atm.plot()
 
-.. image:: _static/desi_bright_atmosphere.png
-    :alt: DESI bright atmosphere configuration
+.. image:: _static/desi_moon_atmosphere.png
+    :alt: DESI moon configuration
+
+To add an additional twilight component::
+
+    atm.twilight.sun_altitude = -13 * u.deg
+    atm.twilight.sun_relative_azimuth = 30 * u.deg
+    atm.plot()
+
+.. image:: _static/desi_moon_twilight_atmosphere.png
+    :alt: DESI moon plus twilight configuration
 
 Note how total sky emission has increased significantly and is dominated by
-scattered moon at the blue end.  To explore the dependence of the scattered
-moon brightness on the observed field, use
-:func:`specsim.atmosphere.plot_lunar_brightness`.  For example::
+scattered moon at the blue end and twilight sun at the red end.  To explore
+the dependence of scattering on the observing conditions, use the
+:func:`plot_lunar_brightness <specsim.atmosphere.plot_lunar_brightness>` and
+:func:`plot_twlight_brightness <specsim.atmosphere.plot_twilight_brightness>`
+functions.  For example::
 
     specsim.atmosphere.plot_lunar_brightness(
         moon_zenith=60*u.deg, moon_azimuth=90*u.deg, moon_phase=0.25)
 
 .. image:: _static/desi_scattered_moon.png
     :alt: DESI scattered moon brightness
 
+and::
+
+    specsim.atmosphere.plot_twilight_brightness(
+            sun_altitude=-13*u.deg, sun_azimuth=90*u.deg)
+
+.. image:: _static/desi_twilight_polar.png
+    :alt: DESI twlight brightness
+
+For an explanatory plot of the twilight spectrum, use::
+
+    atm.twilight.plot_spectrum()
+
+.. image:: _static/twilight_spectrum.png
+    :alt: DESI twilight spectrum
+
+Note how the twilight spectrum is significantly reddened relative to the
+solar spectrum above the atmosphere (yellow) since it passes through a
+large airmass (X~40) before scattering in the atmosphere above the observing
+line of sight.
+
 Instrument
 ^^^^^^^^^^
 

diff --git a/docs/guide.rst b/docs/guide.rst
@@ -42,9 +42,9 @@ independent of its SED.
 Atmosphere Model
 ----------------
 
-The atmosphere adds its own emission spectrum :math:`b(\lambda)` to that of the
-source and then both are attenuated by their passage through the atmosphere by
-the extinction factor:
+The atmosphere adds its own emission spectrum :math:`b(\lambda) X` to that of
+the source and then both are attenuated by their passage through the atmosphere
+by the extinction factor:
 
 .. math::
 

diff --git a/docs/nb/config/desi-blur-offset-scale-stochastic.yaml b/docs/nb/config/desi-blur-offset-scale-stochastic.yaml
@@ -31,7 +31,7 @@ wavelength_grid:
 # The atmosphere configuration is interpreted and validated by the
 # specsim.atmosphere module.
 atmosphere:
-    # Sky emission surface brightness.
+    # Dark sky emission surface brightness.
     sky:
         table:
             # The .dat extension is not automatically recognized as ascii.
@@ -42,13 +42,7 @@ atmosphere:
                     index: 1
                     # Note the factor of 1e-17 in the units!
                     unit: 1e-17 erg / (Angstrom arcsec2 cm2 s)
-            paths:
-                # Each path defines a possible condition.
-                dark: spectra/spec-sky.dat
-                grey: spectra/spec-sky-grey.dat
-                bright: spectra/spec-sky-bright.dat
-        # Specify the current condition.
-        condition: dark
+            path: spectra/spec-sky.dat
     # Atmospheric seeing (only used when instrument.fiberloss.method = galsim)
     seeing:
         # The seeing is assumed to scale with wavelength as

diff --git a/docs/nb/config/desi-blur-offset-scale.yaml b/docs/nb/config/desi-blur-offset-scale.yaml
@@ -31,7 +31,7 @@ wavelength_grid:
 # The atmosphere configuration is interpreted and validated by the
 # specsim.atmosphere module.
 atmosphere:
-    # Sky emission surface brightness.
+    # Dark sky emission surface brightness.
     sky:
         table:
             # The .dat extension is not automatically recognized as ascii.
@@ -42,13 +42,7 @@ atmosphere:
                     index: 1
                     # Note the factor of 1e-17 in the units!
                     unit: 1e-17 erg / (Angstrom arcsec2 cm2 s)
-            paths:
-                # Each path defines a possible condition.
-                dark: spectra/spec-sky.dat
-                grey: spectra/spec-sky-grey.dat
-                bright: spectra/spec-sky-bright.dat
-        # Specify the current condition.
-        condition: dark
+            path: spectra/spec-sky.dat
     # Atmospheric seeing (only used when instrument.fiberloss.method = galsim)
     seeing:
         # The seeing is assumed to scale with wavelength as

diff --git a/docs/nb/config/desi-blur-offset.yaml b/docs/nb/config/desi-blur-offset.yaml
@@ -31,7 +31,7 @@ wavelength_grid:
 # The atmosphere configuration is interpreted and validated by the
 # specsim.atmosphere module.
 atmosphere:
-    # Sky emission surface brightness.
+    # Dark sky emission surface brightness.
     sky:
         table:
             # The .dat extension is not automatically recognized as ascii.
@@ -42,13 +42,7 @@ atmosphere:
                     index: 1
                     # Note the factor of 1e-17 in the units!
                     unit: 1e-17 erg / (Angstrom arcsec2 cm2 s)
-            paths:
-                # Each path defines a possible condition.
-                dark: spectra/spec-sky.dat
-                grey: spectra/spec-sky-grey.dat
-                bright: spectra/spec-sky-bright.dat
-        # Specify the current condition.
-        condition: dark
+            path: spectra/spec-sky.dat
     # Atmospheric seeing (only used when instrument.fiberloss.method = galsim)
     seeing:
         # The seeing is assumed to scale with wavelength as

diff --git a/docs/nb/config/desi-blur.yaml b/docs/nb/config/desi-blur.yaml
@@ -31,7 +31,7 @@ wavelength_grid:
 # The atmosphere configuration is interpreted and validated by the
 # specsim.atmosphere module.
 atmosphere:
-    # Sky emission surface brightness.
+    # Dark sky emission surface brightness.
     sky:
         table:
             # The .dat extension is not automatically recognized as ascii.
@@ -42,13 +42,7 @@ atmosphere:
                     index: 1
                     # Note the factor of 1e-17 in the units!
                     unit: 1e-17 erg / (Angstrom arcsec2 cm2 s)
-            paths:
-                # Each path defines a possible condition.
-                dark: spectra/spec-sky.dat
-                grey: spectra/spec-sky-grey.dat
-                bright: spectra/spec-sky-bright.dat
-        # Specify the current condition.
-        condition: dark
+            path: spectra/spec-sky.dat
     # Atmospheric seeing (only used when instrument.fiberloss.method = galsim)
     seeing:
         # The seeing is assumed to scale with wavelength as