By Neil Hughes

Published: 08:40 AM EST

While sales of portable machines saw tremendous growth during Apple's last financial quarter, desktop sales lagged behind. But the release of new iMacs this week is predicted to change that in a big way.

Piper Jaffray

Following the announcement of new hardware from Apple on Tuesday, Piper Jaffray Senior Research Analyst Gene Munster issued a new note to investors, in which he predicted that the new iMacs will help Apple's desktop market rebound during the December quarter. In the September quarter, desktop Macs saw a year-over-year decline in sales of 16 percent.

"The headwind that existed in the Sept. quarter due to aging Mac desktops has now been turned into a tailwind for Mac units in the Dec. quarter," Munster told investors.

In all, he expects 2.86 million total Macs to be sold in the company's first quarter of its 2010 fiscal year. That would put sales up 13 percent year-over-year -- a number that Munster said could prove conservative, given that total Mac sales of portables and desktops were up 17 percent in the September frame.

Given Tuesday's releases, he believes that Wall Street expectations for Mac sales could also be conservative.

Apple this week released new, thinner 21.5-inch and 27-inch redesigned iMacs; a new MacBook with a unibody polycarbonate design and LED-backlit display; and faster Mac minis, including one new Mac OS X Server option. The company also released a new multi-touch mouse known as the Magic Mouse that will work across the Mac lineup.

Munster said Apple's guidance for the September quarter of $1.70 to $1.78 earnings per share under the generally accepted accounting principles is conservative, though slightly less than usual. However, he said, the release of new Macs so early in the quarter means it is still likely well below what the hardware maker will actually earn.

Piper Jaffray once again reiterated its overweight rating on AAPL stock and has maintained a price target of $277.

Kaufman Bros.

Similarly, analyst Shaw Wu with Kaufman Bros. said that the new iMac and Magic Mouse are the most intriguing products announced by Apple Tuesday. He said the new iMac offers value to consumers and is positioned to be a "sleeper hit."

In his note to investors, Wu said it was particularly interesting that Apple decided to launch so many new products without holding a special event. He called the timing of new products "sooner than expected and somewhat curious."

Wu, also, said the new iMac is poised to provide a boost to the desktop Mac business, which struggled last quarter.

"We believe this refresh will ensure that strong Mac momentum is maintained and allow desktop Macs to once again be a growth business," he said.

In addition, the new Magic Mouse was viewed as another example of "horizontal integration," with Apple employing its multi-touch technology across numerous products. This strategy, Wu said, allows the Mac maker to leverage its research and development investments, and also makes it easier for new customers to learn to use other Apple products.

"We believe the Magic Mouse could serve as a key differentiator for the Mac, bringing its multi-touch technology from its iPhone and iPod touch," he said.

Kaufman Bros. restated its buy rating for AAPL and has maintained a price target of $235.