The ornamental design for a compasshead, as shown and described.
1.1 is a front perspective view of a compass head in a first position;
1.2 is a perspective view thereof in a second position;
1.3 is a top plan view thereof;
1.4 is a bottom plan view thereof;
1.5 is a top plan view thereof in the first position;
1.6 is a side view thereof in the second position;
1.7 is an opposite side view thereof; and
1.8 is a rear view thereof.
The long and short broken lines in 1.1 and 1.2 that define the bounds of the claimed design form no part thereof. The evenly spaced broken lines in 1.6 show a portion of the compass head that forms no part of the claimed design.