Spectroscope will chase an Australian Group One win in the Doncaster Mile at his third local start after earning his way with victory in the Prelude.

The French import is scheduled to back up in Saturday's $3 million race seven days after his win in the Prelude at Rosehill.

Corey Brown rode Spectroscope in the Prelude (1500m) but Hong Kong champion Joao Moreira will take his place in the Doncaster in which the horse will carry 51kg when weights are raised one kilogram as expected.

The defections of Hartnell, Black Heart Bart and Chautauqua means Spectroscope's Godolphin stablemate Hauraki will be the 57kg topweight.

"We think Spectroscope is up to the top level particularly in Australia,"O'Shea said.

The trainer was also pleased with how Spectroscope handled the heavy track with rain expected to return to Sydney late in the week.

Spectroscope is now on the third line of Doncaster betting at $11 with Le Romain the $6 favourite ahead of Hauraki, and McCreery at $8.

Formerly trained by Andre Fabre in France, where he won two 2000m races, Spectroscope came from the tail of the field in the Prelude under hard riding from Brown to beat No Doubt by a length.

Godolphin Australia managing director Henry Plumptre said the four-year-old was one of six horses selected by John Ferguson as ideal candidates for Australian racing.

"He seems to be the best of the six that came over late last year," Plumptre said.

"He has certainly settled in the best of the bunch."

Last year's Doncaster runner-up to Winx, Happy Clapper is also an $11 chance and showed he had returned to form with his win in the Newcastle Newmarket last Friday week.

With the rise in weights, the Pat Webster-trained Happy Clapper will carry 55.5kg, putting him comfortably in the range of his Newmarket-winning jockey Blake Shinn.