[joshman (Josh)]

Originally Posted by bojan

Rotator is needed in case ALTAZ (dob) mount is used, for obvious reasons.
Also, perhaps in slitless spectrometry, it is useful. to avoid overlap of spectra with nearby stars.

Otherwise, I can't see the reason for it..

NB:
Now I know I may have just created a lots of anger in art-oriented individuals.. but IMHO, astrophotography is tech-scientific photography. So the orientation has strict limits/requirements: North direction should be UP, West direction should be to RIGHT, always.

Counterpoints.

1. The majority of Astrophotography is not being taken, nor viewed, nor judged for it's scientific content or merit. And to shoehorn the 99.9% of people into the needs of the 0.1% is an incredibly narrow point of view.
2. If the goal is scientific imagery, then yes, I can see a possible need to standardize orientation, and a rotator is of no use to you.
3. North-up/West-right orientation is really only valid for imagery taken from earth's surface. I'd be very surprised if the JWST, or EUCLID or Hubble used this convention for their actual scientific observations.
4. There is no UP in space.