In a report to clients issued Tuesday, RBC Capital’s Mike Abramsky trots out a new survey in which 13% of respondents said they’d be interested in buying an iPad — more than the 9% who said they were keen on buying an iPhone three months before it was released.

Abramsky uses the results to support his earlier estimate that Apple (AAPL) will sell 5 million units of its new tablet computer in calendar 2010, adding between 7 cents and 59 cents to the company’s earnings per share for the year.

“While we do not expect feverish initial launch lines like iPhone,” he writes, “the data portends well for healthy initial iPad uptake.”

What Abramsky doesn’t mention is that a survey conducted by the same group in September found a significantly higher percentage of interested buyers — 21% — for an Apple tablet priced between $500 and $700. (See Apple’s tablet stoppeth one of five.)

All three surveys were conducted by ChangeWave Research in conjunction with RBC. The most recent questioned 3,200 members of the so-called ChangeWave Alliance between Feb. 1 and Feb. 10. The September 2009 survey was roughly the same size (3,100 members), but asked the question before any of the respondents knew for certain what the device looked like or what it did.

As always with ChangeWave surveys, it should be noted that the participants tend to be early adopters. They are drawn, according the Alliance website, from “a worldwide group of 20,000 highly qualified business, technology, and medical professionals … who spend their everyday lives working on the frontline of technological change.”

Below: Two more charts from the February survey that suggest which iPads are likely to be the most popular (the $499 and $829 models) and what they are likely to be used for (surfing the Web, checking e-mail and reading e-books, in that order).

[Follow Philip Elmer-DeWitt on Twitter @philiped]