Telescope Test and Refactor

[GermanHydrogen]

TODO

• Unit test BaseTelescope
• Refactor BaseTelescope
• Unit test DummyTelescope
• Refactor DummyTelescope

[GermanHydrogen]

@thusser Do you know, why we are updating the "celestial" header every 30sec?

pyobs-core/pyobs/modules/telescope/basetelescope.py

Line 261 in d5f7952

async def _celestial(self) -> None:

I do not see any reason, why this can't be calculated, when get_fits_header_before is called. Even if it would be computationally expensive, caching the result for 30sec seems like the better approach.