To measure the angular distance between the components of a double star by Michelson's method, in front

To measure the angular distance ψ between the components of a double star by Michelson's method, in front of a telescope's lens a diaphragm was placed, which had two narrow parallel slits separated by an adjustable distance d. While diminishing d, the first smearing of the pattern was observed in the focal plane of the objective at d = 95 cm. Find ψ, assuming the wavelength of light to be equal to λ = 0.55μm.