For more on the Samhain alignment of Cairn L, see this page.
For more on the equinox alignment of Cairn T, see this page.
Don't forget to watch the video below, in which I give a quick overview of the hills of Loughcrew using Google Earth. This will give you a sense of where the various cairns are located and which are considered the principal peaks. It will also give you a good idea of the location of the cairns in relation to the Brú na Bóinne complex (Newgrange, Knowth and Dowth):