LONDON, Jan 16 (Reuters) - The following FTSE 100 companies will goex-dividend on Thursday, after which investors will no longer qualify for thelatest dividend payout. According to Reuters calculations at current market prices, the effect ofthe resulting adjustment to prices by market-makers would take 2.56 points offthe index. COMPANY (RIC) DIVIDEND (pence) STOCK OPTION IMPACT Ashtead Group 4.75 0.09 Compass Group 21.1 1.37 SSE plc 27.4 Yes 1.10 Among FTSE 250 companies going ex-dividend are: COMPANY (RIC) DIVIDEND (pence) SuperGroup 7.8 Shaftesbury 4.16 UDG Healthcare 8.5 (euro cents) (Reporting by Kit Rees)