CREATE TABLE "table1_23851574_2" (
  "name" text,
  "aperture_m" text,
  "aper_in" text,
  "mirror_type" text,
  "nationality_sponsors" text,
  "site" text,
  "built_used" text
);

Question: Which aperture were built or used between 1987-2001?
SQL: SELECT "aper_in" FROM "table1_23851574_2" WHERE "built_used"='1987-2001';

Question: How many nationalities/sponsors for mirror/type schmidt uv?
SQL: SELECT COUNT("nationality_sponsors") FROM "table1_23851574_2" WHERE "mirror_type"='Schmidt UV';

Question: Which telescopes were sponsored by or originated in Belgium?
SQL: SELECT "name" FROM "table1_23851574_2" WHERE "nationality_sponsors"='Belgium';