This Luftwaffe Oberleutnant appears to be checking something on a Me109 with the help of an optical instrument of sorts. Can someone tell me what he's doing? Thanks in advance, Neutral.

Checking the propeller's shaft/engine?

A Deutsches Afrikakorps officer exchanging perhaps a message (the aircraft’s strut mask the type of object) with the pilot of a Luftwaffe’s observation plane Henschel Hs 126B of 2.(H)/14. The Hs 126 remained in service in North Africa until August 1942. Victor Sierra

Hs 126 in North Africa

From this airfield March 7, 1945, Major Erich Leie took off for the last flight.
source: http://lotniczapolska.pl/Smierc-asa-Luftwaffe-w-Drogomyslu,21172
