Nikkei falls most in 3 wks; oil and Astellas weigh

* Resource shares slide after oil's fall

* Eyes on earnings, Honda lifts guidance

* Canon posts 54 percent drop in quarterly profit

* Economic uncertainty remains despite good earnings-analysts

By Elaine Lies

TOKYO, Oct 27 (Reuters) - Japan's Nikkei average lost 1.5 percent on Tuesday, its biggest one-day percentage fall in three weeks, as trading houses fell after oil slid and Astellas Pharma (4503.T) was hurt by a brokerage downgrade. Blue-chip exporters such as Honda Motor Co (7267.T) also dragged on the market after U.S. stocks fell on chances that lawmakers may let a federal home buyer tax credit expire, raising fears the U.S. housing industry may lose a crucial incentive that has spurred hopes of stabilisation in recent months. [.N]

Both Chuo Mitsui Trust (8309.T) and rival Sumitomo Trust (8403.T) climbed after the Nikkei business daily said the two planned to merge in early 2011. Trading in their shares was subsequently suspended by the Tokyo Stock Exchange. [ID:nTFA006475]

As Japan's earnings season moves into high gear, analysts said that while generally solid results were supporting the market concerns about the global economy lingered. "Even though the actual earnings we've seen haven't been too bad, there's a lot of uncertainty about the second half of the year, with pretty conservative forecasts," said Hiroaki Osakabe, a fund manager at Chibagin Asset Management. "In addition, I think there's a worry that economic growth may be slowing a bit in the shorter term, leading to selling." The benchmark Nikkei .N225 lost 150.16 points to 10,212.46 and marked its biggest one-day percentage drop since Oct. 2. The broader Topix lost 1.7 percent to 895.48.

Honda, which announced earnings after the bell, nearly tripled its annual profit forecasts as second-quarter earnings fell less than forecast, thanks to government stimulus schemes around the world that boosted sales. [ID:nT324227]

Canon Inc (7751.T), also announcing earnings after the close, posted a 54 percent drop in quarterly profit as weak copier demand outweighed robust digital camera sales, and stuck to its annual forecast for a 62 percent decline. [ID:nT203059]

The result, while in line with market expectations, underscores tight spending budgets by corporations.

U.S. stocks fell for a second straight session on Monday as investors sold shares in home builders and financials, while commodity shares succumbed to pressure from a higher dollar.

"There's a bit of worry that global shares may be headed for a simultaneous correction, given that they've all been rising together for a while," said Takashi Ushio, head of the investment strategy division at Marusan Securities.

"After all, the U.S. earnings and indicators that have recently come out haven't seemed to be bad enough to cause the slide of the last few days. It appears to have been more caused by concern that stocks have risen too far."

Along with corporate earnings, economic indicators are a big focus this week, market players said. On Thursday, Japan will announce its industrial output data for September and the U.S. government will report its first estimate of third-quarter gross domestic product.

ASTELLAS FALLS, OIL WEIGHS