Spotting scopes are usually only thought to be good for land lubbers, but nothing could be further from the truth.  Spotting scopes provide a wide field image and are usually free from chromatic aberrations without having to pay for expensive extra lenses, giving a crisp image of the night sky.  They are extremely portable since most are housed in light weight magnesium based housings.  Although you may not be able to see some of the deep field galactic marvels with a spotting scope, you can still see spectacular views of the moon and stars.  All in all, a spotting scope can be a great alternative for a portable stargazing instrument.