I have had the Pentax 20x60 for about a year now, and I think it's great value for the money: very good optics, fairly rugged construction, etc.
However, I would not consider it for use as your "main line" bino for cruising the night skies. As Kenny points out, it has a very narrow TFOV at 2.2 degrees and the AFOV is around the mid-forties. The TFOV is ok for the magnification, but requires a fair amount of star-hopping to find things. But the narrow AFOV takes some getting used to and the 3mm exit pupil means the views can sometimes be dim. I most often use it to zero in on specific objects for a close-up view after panning around with a wider field unit. You can use it handheld for short periods if seated in a zero-g chair (an additional expense), but it really shines on a mount (another expense!).
All that said, I think a 15x70 will really open up your viewing experience, either mounted or handheld while seated. Although the Oberwerk 15x70 LW fits your budget, you are likely better off saving up another $100 to get the 15x70 Deluxe. Both these models have been commented on in this CN forum, and are worthwhile reading up on. I have the Ultra model, but it's a heavy spud, is more expensive, and is best used on a decent mount.