Minor refactoring

[teutoburg]

See commit msgs for details.

[codecov]

Codecov Report

Patch coverage: 96.00% and project coverage change: -0.01% ⚠️

Comparison is base (7650119) 80.19% compared to head (57f84f0) 80.19%.

Additional details and impacted files

@@              Coverage Diff               @@
##           dev_master     #272      +/-   ##
==============================================
- Coverage       80.19%   80.19%   -0.01%     
==============================================
  Files             143      143              
  Lines           14792    14791       -1     
==============================================
- Hits            11862    11861       -1     
  Misses           2930     2930              

Files Changed	Coverage Δ
scopesim/effects/metis_lms_trace_list.py	31.55% <0.00%> (ø)
scopesim/effects/detector_list.py	92.70% <100.00%> (ø)
scopesim/effects/psfs.py	71.80% <100.00%> (ø)
scopesim/effects/spectral_trace_list.py	60.62% <100.00%> (ø)
scopesim/optics/image_plane_utils.py	93.39% <100.00%> (-0.03%)	⬇️

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[hugobuddel]

LGTM!