Left out overnight in low single digits with snow falling. 9°F when I started this morning.
The Swarovski X5 and Minox ZP5 are on rifles and they were in the truck. Still 9° on them.
From the top of the image down, checking for power ring and parallax smoothness, turret feel, and anything else effected by the cold.
1). Burris Veracity 2-10x42mm: No effect
2). Sightron STAC 3-16x42mm: Stiffer mag ring
3). Sightron Siii 6-24x50mm: Stiffer mag ring
3). Trijicon 2.5-15x42mm Credo HX: Parallax a bit stiffer
5). Trijicon 3-18x44mm Tenmile: No effect
6). SWFA SS 3-15x42mm FFP: Maybe very slightly mushier elevation turret
7). Leupold MK5 3.6-18x44mm: No effect
8). Vortex Razor HD LHT 4.5-22x50mm: Extremly tight mag ring. Almost not able to turn. Bad enough that if using hunting I would set it at 7-8x and leave it- no way to quickly adjust it on an animal. Elevation turret extremely soft and mushy.
9). Vortex Viper PST Gen 1 2.5-10x32mm: Mag ring very stiff- almost unusable. Stiff parallax.
10). Bushnell Elite Tactical 3-12x44mm LRTS: No effect.
11). NF 4-16x42mm ATACR: No effect.
12). NF 4-32x50mm NX8: No effect.
13). NF 3.5-15x50mm F1: No effect.
14). Meopta Optika 6 3-18x50mm: No effect.
15). Swarovski X5 5-25x56mm: Stiff power ring.
16). Minox ZP5 5-25x56mm: No effect.