I am pretty late in the party but hoping to get some cake and also to help someone out having the same requirement-
You can use the below script to detect the browser type by its feature detection as specified in this post.
var isOpera = !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
// Opera 8.0+ (UA detection to detect Blink/v8-powered Opera)
var isFirefox = typeof InstallTrigger !== 'undefined'; // Firefox 1.0+
var isSafari = Object.prototype.toString.call(window.HTMLElement).indexOf('Constructor') > 0;
// At least Safari 3+: "[object HTMLElementConstructor]"
var isChrome = !!window.chrome && !isOpera; // Chrome 1+
var isIE = /*@cc_on!@*/false || !!document.documentMode; // At least IE6
After that you can turn off the stellar initialization for specific browsers like-
if(!isSafari || !isIE)
{
$(window).stellar();
}