Is it illegal to take an archery sight and attach a non-electronic 2x lens to the sight scope. No cross-hairs just a lens, and hunt big game.

Question:

See excel archery sights for an example.

Answer:

 It is illegal to use any magnifying lens during an archery-only​ season for big game in Idaho.  However, it is legal to use a magnifying lens while archery hunting during an any-weapon season for big game in Idaho.