Fix SST-1M to be DC and not SC. Solves #905

[thomasgas]

No description provided.

[maxnoe]

What does DC stand for in this context?

And is this lookuptable really needed?
What does it give us, that's not readable from the simtel files?

[thomasgas]

DC is Davies-Cotton. I think it's a useful piece of information (to distinguish Davies-Cotton from Schwarzschild-Couder). This look up table is fine for now but maybe these information can be also read from the mc. I would fix it for now and leave other changes to another PR.

[maxnoe]

But LST is not Davies Cotton afaik, its parabolic

[codecov]

Codecov Report

Merging #908 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #908   +/-   ##
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  Coverage    82.7%   82.7%           
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  Files         186     186           
  Lines       10978   10978           
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  Hits         9079    9079           
  Misses       1899    1899

Impacted Files	Coverage Δ
ctapipe/instrument/optics.py	94.23% <ø> (ø)	⬆️

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[thomasgas]

But LST is not Davies Cotton afaik, its parabolic

You're right. So i guess that by now "DC" is kind of an alias for "1-mirror-telescope" and "SC" is for "2-mirror-telescope". Which is clearly wrong...
what shall we do with this LUT? fill it with correct info or create it from the mc?

[kosack]

This info is there since one is not always reading an MC file, so you need a lookup for it. Also at the time, it wasn't possible to read it from the MCs - is there now some accessor?

For the names, I agree it's not ideal - we can easily change the optics type names, however, since they are not fixed or used anywhere yet. The main reason was to be able to adapt algorithms to different types, which could be simply the number of mirrors, but also may have other aspects such as off-axis corrections. I'm happy if we update these to be correct, or use better names.

• SC: Swartzschild-Couder
• DC: Davies Cotton
• might need another for modified Davies-Cotton (e.g. LST) - is there a name for that mirror type? Parabolic DC?

[maxnoe]

might need another for modified Davies-Cotton

LST is afaik not a modified Davies–Cotton but a pure Segmented Parabolic Mirror

[thomasgas]

so do you want to merge this or do you want to change LST optics.mirror_type in order to be consistent?

[maxnoe]

Apply this simple fix now, i'd say, rest later

[GernotMaier]

For completeness: the 1-mirror MST has a 'modified DC design' (something between DC and parabolic).

I don't think this matters anywhere (unless one needs e.g. the smearing in time due to the optics or if one wants to fold the expected optical PSF into the image reconstruction), and knowing that it is a one or two-mirror instrument should be enough.