Green’s Dictionary of Slang

telescope n.

1. the penis.

[Scot]Order of the Beggar's Benison and Merryland (1892) 28: Dinner Sentiments [...] Nymph. My dear, let me look through your Telescope? What a long one! Swain. [...] Pull it out. That’s not the way. You will twist it.

2. (US tramp) a nested set of tin cans used for cooking.

[US]Charleston (WV) Daily Mail 27 June 8/8: A ‘telescope’ [is] a nested set of tin cans of different sizes used for cooking.