Originally Posted by
Al1943
No, all Shimano 8-speed cassettes have the same cog spacing. Dura-Ace 8-speed shifters and rear derailleurs are no cross-compatible with other groups. It just happens that the D-A shifter cable pull is the same as all Shimano 9-speed shifters (less one click). The 8-speed D-A rear derailleur has a unique actuation ratio. Read the info in the link I offered above. It's all there.
Interesting... If he's got Dura-Ace 8-spd RD, he can make it work OK on 9-spd cassette by using Shimano 10-spd shifters. Almost perfect, but not as precise as Shimano 9-spd derailleur + 9-spd shifters.
Seeing as how he's using the DA shifters with Deore RD, he's got a compatible 9-spd RD+shifter combo. However, there's no way to re-use the 8-spd cassette as 9-spd without a lot of work.