Clouds are an amazing to look at and photograph. I am sure that like me, you will have probably looked at them and tried to find faces hidden within them. From a landscape photography perspective they are interest to the sky which enhances an image. During sunrise and sunset they glow and have amazing colours. With a little knowledge you can predict to some degree of certainty if a great sunrise or sunset will happen. It certainly makes it easier to get out of bed at a ridiculous time of the morning during the summer months if you know the sky is likely to glow. However as always nothing is guaranteed and yes there are times when you expect things to be perfect and nothing really happens.
From a dark sky and astro photography perspective then clouds are not welcome at all. You want perfectly clear skies that will give an uninterrupted view of the heavens. Many a time I have cursed them when the forecast has been for a crystal clear night. There is one type of cloud however that are the exception to this rule and they are Noctilucent Clouds.
Without doubt, Nocto clouds have to be my favourite of all of our clouds. There is something truly magical in the way that they dance in the sky and to me they come a close second to the Aurora. It is little wonder then that for those of use who chase the Northern Lights during the winter months, turn our attention to these clouds during June and July. I say June and July because that it the only time of the year when they are visible. You may have already seen Nocto clouds and wondered what they were, you may also have scratched your head and wondered why they appear to be brilliant white when its dark where you are standing. It shouldn't really happen should it, the sun has set and we know that we need the sunlight our world as we do each and every day.
The reason lies in how high the Nocto clouds are in our skies. The are the highest of all known clouds. Somewhere over 50 miles (80 km) high. As you can image that they hight, any moisture is frozen and they clouds are filled with tiny ice crystals. Combine their altitude and content, gives you the answer. You are looking up and the sun has set well below the horizon. However, 50 miles up the sun is still visible but low in the sky and the clouds are well above it. What is happening is that the sunlight is hitting the bottom of the clouds and illuminating them. You therefore see them glowing in the night sky.
Now for the bad part. There is no know way of predicting when they will appear and there is a bit of luck involved. Yes you will need to have clear skies forecast. However there are plenty of people out looking for them and it is possible to forecast when they could be visible. I have put a link below to Glendale Aurora which is an amazing free service offered by Andy Stables up on the Isle of Skye. At this time of year, Andy adds information on when it may be possible to see Nocto clouds and people who use the app will add sightings in real time to the map during the night.
So there you have it. If you are lucky enough to see them this year, send me your photos, I would love to see what you are capturing. Good luck and as ever stay safe.