Parallax is just basic trigonometry. The longer the baseline, the better. But even if you do assume a 180ish million mile, 6 month base line, even nearby stars have some pretty small parallax angles. The hard part is getting very accurate and precise measurements of those angles and the earth's atmosphere becomes a limiting factor. That's why parallax measurements from earth based observatories are limited to around 300 or so light years. With smaller baselines (resulting in smaller parallax angles), the measurable distance would be significantly less.