Manipulate[
ContourPlot[
({Sin[θ] Cos[ω(t-t0)],Sin[θ] Sin[ω(t-t0)],Cos[θ]}.{-Cos[(Subscript[θ, 0])] Cos[T Ω], - Sin[T Ω], -Cos[T Ω] Sin[(Subscript[θ, 0])]}/.{t0->-Ω/ω T}/.{ω->2π/24, Ω->2π/(365.25)} )== 0,
{T,-365.25/2,365.25/2},{t,0,24},
BaseStyle->{FontSize->14,FontWeight->"Bold"},ContourStyle->{{Thick,Black}},FrameLabel->{"T in Tagen","t in Stunden"},
Epilog->{
{Dashed,Line[{{0,-2},{0,26}}]}
}
],
 {{(Subscript[θ, 0]),FromDMS[{23,26,5}] Degree},0,π/2},{{θ,49 Degree},0,π/2},FrameLabel->"Zeit von Sonnenauf- und untergang",
ControlPlacement->Bottom
]