@Korb Biakustra @Avera9eJoe I was having the same issue on Linux, both on 1.6.1 and 1.7.1, using the latest version of Spectra (1.2.2 from CKAN). After looking into the logs, I turned out to be caused by some assets not being loaded by Scatterer:
[LOG 15:11:56.893] [Scatterer] Atmosphere config found for: Kerbin
[LOG 15:11:56.895] [Scatterer] no inscatter.raw or inscatter.half file found for Kerbin
[LOG 15:11:56.896] [Scatterer] no transmittance.raw or transmittance.half file found for Kerbin
It turns out there is a small typo in the bundled Scatterer config for the Kerbin atmosphere. In the file "Spectra/Spectra_scatterer/Planets/Kerbin/atmo.cfg" in GameData, the "assetPath" is incorrect.
Where it says:
assetPath = Spectra/Spectra_Scatterer/Planets/Kerbin/Atmo
It should be as follows:
assetPath = Spectra/Spectra_scatterer/Planets/Kerbin/Atmo
At least in the latest version of Spectra, this is also the case for the Eve and Laythe config files, as well as in "Spectra/Spectra_scatterer/Sunflares/Phi/Sun.cfg", for the sunflares. This wouldn't cause any issues on Windows or (most) macOS installs as their filesystems are case-insensitive, which is why this only pops up on Linux systems.
