Astronomy binoculars can be an excellent choice for stargazing when mobility is one of the most important factors.  They can be easily stored in the car so you have them with you when the mood strikes. They are also a no brainer to operate, and there is no learning curve like there might be with a telescope.  These days, most astronomy binoculars are housed in light weight magnesium based alloy housings, so they are light weight and very versatile.  However most also come with a built in mounting plate so you can hook them up to a tripod or monopod should you require increased stability.