I believe this to be developing NLCs - this photo taken from Larne, NI close to midnight on Thursday 31st May. Unfortunately a haze rose from the sea very shortly after this was taken so I never got to see if it developed further.
The caveat is that there was a Full Moon rising behind me so there is the possibility that this was lower cloud being illuminated by the Moon.
That sure looks like forming Veil NLC to me and the reason why is because I seen it myself which I followed with a 2nd observation later in the night which showed that this display had developed remarkably in magnitude. So far this season the NLCs which have appeared seem to reach their 'best' after midnight and before dawn which contrasts greatly with the 2006 season which produced a number of structured displays in the evening sky. This season is certainly very different to last year so far.
I think the problem is that digital cameras have a difficult task capturing faint Veil forms against bright twilight with the resulting image looking nothing like the visual scene. I have noticed this with my own images which do little to replicate the naked eye treat. My camera in particular is very poor at picking up faint or soft subjects so I end up getting unconvincing captures. Having said that, it does wonders with the more complex displays which I hope to be getting images of very soon.
Not easy to be conclusive one way or the other, but, if pushed, I'd tend toward this not being NLC. With light haze and moonlight present I think this is more likely to be tropospheric cloud/layers of haze with twilight penetrating the thinner, more transparent bands, or, reflecting moonlight (or a bit of both?). However, as I say, not easy to be 100 percent sure either way, especially from photographs!
Well Tom, ideally I'd have been able to follow the display through and see it develop, which would have confirmed it. The colour was definitely that of past NLC displays I've seen and my camera is pretty good at picking that up - it's a Minolta DSLR with "big" pixels and I find this sort of camera is better at getting smooth textures right than cameras with smaller pixels.
Martin did confirm a similar display - he is some 40 miles from me and not by the sea so his view wasn't spoilt by the rising haze that I experienced so I'm minded to think that was the start of a display I saw but I agree - not 100% certain.
Not to worry, there'll be better along any day now!