Emmanuel,
From what I understand the G-Star has the Sony ICX429ALL CCD sensor (same as the DSI II pro) and the Stellacam II is basically the same as the Watec 120N which has the Sony ICX418ALL CCD sensor.
Here are the specs for the Stellacam II:
http://www.optcorp.com/product.aspx?...-325-3480&tb=2
Here are the DSI II pro specs:
http://www.meade.com/dsi_ii/specifications.html
Here are the G-Star specs:
http://www.myastroshop.com.au/guides...SPECIFICATIONS
You can also review the Sony datasheets for these (attached). Based on my interpretation of the Sony data sheets it would appear the ICX429ALL is more sensitive.