Isak,
Yes all the PhaseOne P+ series backs are good for long exposures, so this has the same capability in that respect as the P45+, using the Xpose+ technology i believe, just a lower resolution.
The CCD is 36.9x36.9mm
Pixel size is 9x9 micron
Giving 4080x4080 active pixels
Resolution 16 mpx
ISO 50-800
Exposure time1/10,000 up to one hour with Xpose+
The back is about 3.5 years old.
I hope this helps
Thanks