In planetary imaging, like in sports photography, speed is the key.
A typical planetary camera like an ASI290mm at full frame (1936x1096) delivers 130fps.
That means roughly 2x130x8 = 2Gb/s
Do you think a Raspberry Pi will be able to grab & write a SD card at such a speed without losing frames ?
Of course, you can use ROIs for planets, but for the moon, you'll need full frame.