A C# Diminished (C#dim) chord contains the notes C#, E, G. It is built from the diminished formula 1 - ♭3 - ♭5, with C# as the root.
Is C#dim the same shape as Bdim?
Yes — identical, just two frets higher. Diminished chords are symmetrical, so one movable form covers them all; sliding it up or down simply renames the chord.