Full Idea
Earlier, Frege divided objects into subjective, actual objective, and non-actual objective; in the 'Grundgesetze' he emphasised logical objects; but in 'The Thought' the non-actual objects become exclusively thoughts and their constituent senses.
Gist of Idea
Late Frege saw his non-actual objective objects as exclusively thoughts and senses
Source
report of Gottlob Frege (The Thought: a Logical Enquiry [1918]) by Michael Dummett - Frege philosophy of mathematics Ch.18
Book Reference
Dummett,Michael: 'Frege: philosophy of mathematics' [Duckworth 1991], p.225
A Reaction
Sounds to me like Frege was finally waking up and taking a dose of common sense. The Equator is the standard example of a non-actual objective object.