1) Magnetic device 
A magnetograph is one of two types of scientific instrument: ...
instrument for recording measurements of magnetic fields
• (n.) An automatic instrument for registering, by photography or otherwise, the states and variations of any of the terrestrial magnetic elements.
An instrument attached to a solar telescope for the purpose of producing magnetograms. The first solar magnetograph was developed by Horace Babcock in 1953.
Mag·net'o·graph noun [ Magneto- + -graph .] (Physics) An automatic instrument for registering, by photography or otherwise, the states and variations of any of the terrestrial magnetic elements. 
A special telescope which analyzes the color and polarization of sunlight in order to measure the magnetic field of the Sun.
magnetogram; magnetograph A graphic representation of magnetic field strengths and polarity.
noun a scientific instrument that registers magnetic variations (especially variations of the earth`s magnetic field)