Apple reports its third-fiscal-quarter earnings after the market close on Tuesday and analysts are expecting it to be a big quarter.

Apple has become the world’s most valuable tech company, with a market capitalization of approximately $344 billion (Google Finance: AAPL), and as a result, analysts and investors closely watch its earnings as a sign of health for both the computer and mobile device businesses.

In addition to its computer business, the company also dominates the tablet market with its iPad, is one of the largest makers of smartphones, and has a strong position in distributing music and videos through its iTunes Music Store.

Thomson Financial expects revenues of $24.75 billion for the quarter ended June 30, and earnings per share of $5.73.

A year ago, Apple posted revenue of $15.7 billion and net income of $3.25 billion, or $3.51 a share, for the same quarter.

Apple itself previously said its third fiscal quarter outlook was for $23 billion in revenue and $5.03 a share in earnings per share.

A year ago, Apple sold 3.47 million Macs in its third-fiscal quarter, 8.4 million iPhones, 9.41 million iPods, and 3.27 million iPads.

Professional Wall Street analysts polled by Fortune say that they expect Apple to post of iPhones ranging from 15.6 million units to 19.64 million units; iPod sales are expected to be 7.21 million units to 9.76 million units; Mac shipments are expected to be 3.8 million to 4.4 million units; and iPad shipments are expected to be 7. 5 million to 9.0 million units.

Back in April, Apple reported these second quarter results:

Revenue:$24.67 billion, up 82 percent from a year ago.

Net income: $5.99 billion, up 95 percent from a year ago.

Mac sales: 3.76 million units, up 28 percent from a year ago.

iPhone sales: 18.65 million units, up 113 percent from 8.8 million a year ago. Overall smartphone market growth is targeted at 74 percent, according to IDC. The iPhone is available from 186 carriers in 90 countries now. About 5.2 million units are in channel inventory. About 88 percent of Fortune 500 companies are deploying or testing iPhone. Corporations adopting include Cisco, Xerox, Deloitte, General Motors and more.

iPod sales: 9.02 million units, compared to 10.9 million a year ago. U.S. market share great than 70 percent, according to NPD.

iPad sales: 4.69 million (N/A year ago). iPad 2 launch March 11 in U.S. and 25 more countries by March 25. Available in 59 countries by end of March. No impact on supply chain as a result of Japan quake. Channel inventory is thin at 400,000 units. Overall 850,000 inventory. Enterprises deploying iPad include Xerox, ADP, Boston Scientific, Estee Lauder, and Disney. Adding 13 more countries next week.

Total iOS sales to date: 189 million.

Tunes sales: $1.4 billion. 1 billionth visitor coming soon.
eBooks: More than 100 million downloaded; store has 2,500 publishers.
apps: 350,000 available and more than 10 billion downloads. More than $2 billion pad to developers.

Apple stores: 71.1 million visitors, compared to 47 million a year ago. $3.19 billion in revenue, up 90 percent. 797,000 Macs sold in stores, half to customers without Mac history. Average revenue per store $9.9 million, up 67 percent. More than 300 stores open now, 40 more opening in 2011, including fifth store coming soon in China.

Cash and cash equivalents: $65.8 billion, up $6.1 billion from previous quarter.