fix pixel scale factor to use wavelength-dependent aperture areas

jdaviz/configs/cubeviz/plugins/spectral_extraction/spectral_extraction.py

@@ -335,6 +335,7 @@ def bg_weight_mask(self):
     def aperture_area_along_spectral(self):
         # Weight mask summed along the spatial axes so that we get area of the aperture, in pixels,
         # as a function of wavelength.
+        # To convert to steradians, multiply by self.spectral_cube.meta.get('PIXAR_SR', 1.0)
         return np.sum(self.aperture_weight_mask, axis=(0, 1))
 
     @property
@@ -478,7 +479,7 @@ def extract(self, return_bg=False, add_data=True, **kwargs):
             spec = spec - bg_spec
 
         # per https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam-performance/nircam-absolute-flux-calibration-and-zeropoints # noqa
-        pix_scale_factor = self.aperture.scale_factor * self.spectral_cube.meta.get('PIXAR_SR', 1.0)
+        pix_scale_factor = self.aperture_area_along_spectral * self.spectral_cube.meta.get('PIXAR_SR', 1.0)  # noqa
         spec.meta['_pixel_scale_factor'] = pix_scale_factor
 
         # stuff for exporting to file