okay, check this out. i did some more research on the web, (out of desperation, i really want to get this fork) and i came across this page.

http://www.parktool.com/repair_help/..._headset.shtml

if you scroll to the bottom of the page, it gives all the dimensions for all the different standards out there, at least that i can think of. now the dimension it lists as 1 1/8" on the 1 1/8" standard is the "fork collumn outside diameter" (read: steerer tube ouside diameter) and it lists the "acceptable headtube ID(inside diameter) as 33.75 -33.9 mm ( in the range of 1 5/16".) sure enough, i took the measurement once again, and it is somewhere within that range. I don't mean to doubt you Astra, but it seems pretty clear. are you sure that the diameter that i need is the head tube inside diameter, or is the site correct, and the diameter that i need the steerer outside diameter?