Trying to add styling to WordPress site logo

I’m trying to add some CSS to a WordPress site logo and it’s driving me nuts. Here is the html:

<div id="main-container">
    <header id="top-header" >
        <div id="logo">
            <a href="http://somesite.com/"><img src="http://somesite.com/wp-content/uploads/2013/06/cropped-cropped-logo2251.jpg" width="175" height="194" alt="somesite Wood logo"/></a>
        </div><!-- end of #logo -->
        <div id="main-navigation">
            <div class="social-icons">
                <ul>
                </ul>
            </div>

And here are the CSS variations I have tried but do not work:

#logo a img { 
    opacity: 0.85;
}
#logo a { 
        opacity: 0.85;
}
#top-header #logo a img { 
        opacity: 0.85;
}
#logo img { 
        opacity: 0.85;
}

Link to the site is here: www.patchwood.ca