Why are telescopes shaped like this?

[Keatah]

Why are some telescopes shaped like this?
I'm referring to the light inlet aperture or sunshade. Why is it angled like so?

 

[Urwumpe]

Why are some telescopes shaped like this?
I'm referring to the light inlet aperture? Why is it angled like so?

To reduce the amont of sun light that shines into the telescope and disturbs the measurements. And angled for simply saving weight, since the sun will always be at about the same direction from the satellite.