The two links below explain why the rare 7x42 and 8X42 binoculars are a better choice than the popular the 10X42 for low light use. A 10X binocular in low light is best paired with an objective of 50 (or larger)which few are because of the size/weight. A human pupil will dilate 5-7 mm in low light. A 10x42 binocular has an exit pupil of 4.2 mm. An 8x42 pair has an exit pupil of 5.25 mm which is more usable light. A 7x42 has even more usable light with an exit pupil of 6.0 mm.
Not only does the 10x42 have less usable light in low light conditions than the 7X or 8X. They also have less FOV and are harder to hold steady without the aid of a tripod.
Light Gathering & Exit Pupil
Binoculars: How to Choose