Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_30057479_1 ( researched_at VARCHAR, geometry VARCHAR )

### Question ###
Where was d: ~50nm, l: ~600nm geometry researched?

### Accurate SQL ###

SELECT researched_at FROM table_30057479_1 WHERE geometry = "D: ~50nm, L: ~600nm"