The ornamental design for a spectrometer, as shown and described.
1. Spectrometer
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Top
1.5 : Bottom
1.6 : Left
1.7 : Right
1.8 : Partial enlarged cross-sectional view
1.9 : Partial enlarged top view
1.10 : Partial enlarged perspective view
The broken line showing is included for the purpose of illustrating portions of the “article” and forms no part of the claimed design. The dash-dot-dash lines represent the boundary of the claimed design.