This is a multi-exposure of three frames,(or maybe it was four, can`t really remember..), done in the camera when shooting. This is in fact not a new technique regarding Nikon cameras and I am quite used to it from the "good old" film days, so it was quite stunning when I recently heard that the Canon digital cams didn`t have it. For me, it`s a bit of "cheating" to do such thing later in the post processing part, I just wouldn't have done it..
The image consists of one long exposure with a nd110 and two shorter exposures about a second each. (If I can recall right though..)
My equipment isn`t that much these days, all I shoot with,(all I own) is a Nikon D2x and a Tokina AT-X PRO 116, 11-16mm 2.8, a good tripod and a remote shutter release. And because I think that a "normal" short exposure gets kind of to hard when shooting landscape, so that`s why I usually prefer to use my nd110 and a longer exposure time. To soften out the waves and get some motion in the skies.
Hope you enjoy the picture though!! ;-)