It's a bit of a dilemma in the world of aurora chasing: do you want moonless skies, when the light from the aurora has nothing to wash it out as it paints designs across the deep darkness of the starry space above? Or do you want some moonlight - that will wash out something of the brightness of the northern lights - to cast its magical glow over the land below, revealing something of the landscapes above which the aurora is displaying?
When you're standing on the glorious scenery that is the Giant's Causeway, however, there is no dilemma at all. To coin a phrase, give me the moonlight, any time!
As we headed towards darkness on 16th April, with reasonably clear skies forecast for the night ahead, I checked the aurora forecast. With a half moon due to be high in the sky, any show would have to be good to compete with the light that would wash across the sky. Any anyway, no aurora activity was being anticipated for the mid-latitudes. But it's always worth checking the stats. And, indeed, as the day progressed, they were looking good. The ACE satellite appeared to have picked up some disturbance in the solar wind around 04.00 am - perhaps a stealth CME that had snuck past the rest of our satellites?
Whatever the cause, these stats were worth keeping an eye on. The Bt (the strength of the Interplanetary Magnetic Field) rose to around 10 nT and stayed there. That meant there was the potential for the Bz to dip quite far south (the Bt acts as a lid to the Bz - it cannot reach figures that exceed the Bt). But, for most of the day, the Bz didn't make it too far negative. And in fact, from about mid morning on, it fluctuated between slightly positive and slight negative.
However, by around 18.00 hours BST, it started to fall to around -10 nT. We were still two or three hours from darkness, but the signs were improving. In fact, the Bz stayed at those low levels until around 21.00 hours. And so, as twilight faded, it was definitely game on - and I headed out for the Giant's Causeway.
I had yet to catch the aurora here in moonlight. And I was excited at the possibility of doing so. Being able to capture that wonderful green glow above that always photogenic location as all the wonderful stones were lit by the moon was definitely on my to-do list.
As I made my way onto the stones, I quickly set my camera up and checked the screen. Even before I took a shot, the screen was revealing green along the horizon! I took a shot - and there it was. For the next hour or so, I tried out various compositions. The green arc hung low and thin to the eastern horizon, while low cloud hung stubbornly to the north and west. But I was getting it, nevertheless.
Reception was poor down there, so I could only check the stats intermittently. I hung on in the hope that the display would kick off and I would see pillars emerge from the green arc. But, when I did get to check the stats again, I realised this was unlikely.
After about 21.00 hours, the Bz moved closer to zero again, and the chance of activity strong enough to compete with the moon faded. Around the same time, the cloud from the northern horizon closed in at the Causeway. It was still clear the the east, and so I did what I rarely do these days which was to get in the car and drive during an aurora show!
As I chased the ever fading aurora east, the cloud was hot on my heels. I stopped in a few locations on the way for some quick shots, before finishing off at Ballintoy. I managed to get one or two more shots, just about picking out the aurora before it more or less faded from view even on camera.
So not the brightest, or liveliest, or most visually amazing of aurora viewings. But the wonder of the soft moonlight, combined with the rugged beauty of the coastline of the Causeway Coast, made for a wonderful few hours of aurora chase nevertheless. And I for one was more than happy to have the man on the moon for company that evening!