NEW YORK ( TheStreet) -- Solar stocks are taking a breather after a big rally on Wednesday, and First Solar ( FSLR) even received a downgrade, based purely on valuation and the fact that the solar bellwether has run up to an 18-month high share price.

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On Thursday, Auriga Securities downgraded First Solar to a hold, and said in its downgrade that it did not intend to be a solar "rally killer," but with First Solar already the premium-priced stock in the sector, and its shares ending Wednesday above the $164 mark, a pause was prudent.

Auriga's price target remains $167 on First Solar. The recent Goldman Sachs upgrade of First Solar with a price target of $165, and the addition of First Solar to Goldman's conviction buy list, were often cited in the recent rally in First Solar shares and the solar sector more broadly.

TheStreet has previously noted that First Solar shares have traded in a predictable pattern over the past year and a half, and at these levels, a pullback would be suggested by the charts. On the other hand, the 18-month high that First Solar reached on Wednesday was a "break-out" above the established trading range, in the least poking a minor hole in the chart trading approach to First Solar.

First Solar has benefited from another trading chart as well -- its well-established link to oil prices. As oil rises, so does First Solar, and with the recent unrest in Egypt and the rising price of oil, it's been a good trading chart for First Solar.

The Auriga analyst, though, leaves aside the chart trading noise and makes the straightforward case that a downgrade of First Solar from buy to hold is merited because it's not possible to raise earnings estimates further.

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