According to the present invention, an optical apparatus is provided that comprises a recording medium, a distance-detecting sensor, an illustrated-guide selector, and an image-indicating device. The recording medium stores illustrated-guide data for a plurality of illustrated guides. The distance-detecting sensor detects distance information relating to an observation target. The illustrated-guide selector selects one illustrated guide from the plurality of illustrated guides, in accordance with the distance information. The image-indicating device displays information of the illustrated-guide data.