An Air Carrier First Officer called in fatigued after the pilots were scheduled to fly a repositioning flight very late at night since he had been up very early that and the previous several mornings.

Narrative

After arriving; I was made aware by my Captain late in the evening that the weather at our destination was below minimums and we were going to wait 45 minutes to see if the weather would improve. About 45 minutes later; he advised me that the weather had not improved and company had decided to cancel the return flight. Company was now considering having us reposition the aircraft to an airport near our destination which was reporting 1/2 SM visibility and 100 FT overcast. My Captain was unable to receive timely instructions from the Company on how to proceed and very late that night I was advised that the Company was to have us reposition the aircraft the diversion with a different alternate. They were then going to begin working on scheduling this flight. I advised my Captain that; due to the 2 previous days of early showtimes; I did not feel that I could safely perform my flight duties at the late hours required to make this flight happen. He supported my position and I called Company to report fatigued. I have been assigned two other very similar trips this month flying for this Air Carrier. These trips expect crews to report at before dawn; immediately followed on the third day by a later report time which will work the crew until approximately midnight-thirty; assuming no delays. This schedule needs to be altered so that crews are not established on a completely different sleep cycle than one which is required in successive days of the same trip.