In some embodiments, an auxiliary optical system comprises an adapter that is either separable from or unitary with a retainer. The adapter permits the retainer to removably attach to a plurality of mobile electronic devices of different sizes. In some embodiments, an auxiliary optical system comprises a mounting component configured to removably attach to a mobile electronic device and to a base which includes a plurality of attachable subcomponent securement members. Each securement member is configured to receive at least one optical element. In some embodiments, an auxiliary optical system comprises a retainer component configured to removably receive an optical element and to removably receive a non-optical component and/or an electronic component.