What do you shoot when there is 6 weeks of all-night twilight?

[Tonk]

Noctilucent Clouds of course. This year I have already seen 3 displays before the solstice which is quite unusual

Here's a nightscape from a field close to my dark-sky site a few nights ago - hoping for some betters ones over the next 4 weeks

Last years finest display from a field near my house - this one was truly stunning electric blue bright!

And a very pretty wispy display from 2011

The bright star in all these views is Capella - Gemini/lynx region to left, Perseus/Andromeda to the right

I've managed to image NCLs every year from 2005 when we moved house and got clear low views of the northern horizon from the top of a ridge overlooking the Wharfe Valley on the West/North Yorkshire boundary

[SkyJamie]

Awesome images Tonk hopefully it'll be a good year for them

[xtreemchaos]

great shots mate, Noctilucent Clouds are great to see but not photographted enough.thanks for sharing..charl..

[Tonk]

You can do fun stuff working out where these clouds are. Some basic trigonometry will help work out how far north the clouds right on the horizon are and how far away this is by line of sight.


NLCs are about 80 to 82 km above the Earth according to various sources. Earth's radius is 6371 km (Wikipedia). Lets assume 80 km high to get into the right zone.

So the increase in latitude from your location to the clouds right down on the horizon is given by inverse cosine (6371 / (6371 + 80)) = Inverse cosine (0.9876) = 9 degrees.

My picture was taken very close to 54 North (Ripon area) so the clouds on the horizon are at latitude 63 North which is 1 degree north of the Faroe Islands.

The bright star Capella provides a guide to the locations of the highest edge of the clouds. Capella is very close to 10 degrees above the northern horizon (measured via Stellarium). In the 3 panoramas the top of the clouds range from 5 degrees to 9 degrees above the horizon, This gives (via the good old triangle sine rule and angle sum rule):

@ 5 degrees above horizon - cloud latitude = 59.3 degrees; line of sight distance = 600 km (between Orkney and Shetland Islands according to map)
@ 9 degrees above horizon - cloud latitude = 57.7 degrees; line of sight distance = 424 km (over Northern Scottish Highlands)

The direct line of sight distance to the furthest visible clouds (right down on the horizon) is tan (9) = distance / 6371. So distance to clouds = 0.1582 * 6371 = 1009 km - wow! some distance away!!!!          

[Owmuchonomy]

You can do fun stuff working out where these clouds are. Some basic trigonometry will help work out how far north the clouds right on the horizon are and how far away this is by line of sight.

NLCs are about 80 to 82 km above the Earth according to various sources. Earth's radius is 6371 km (Wikipedia). Lets assume 80 km high to get into the right zone.

So the increase in latitude from your location to the clouds right down on the horizon is given by inverse cosine (6371 / (6371 + 80)) = Inverse cosine (0.9876) = 9 degrees.

My picture was taken very close to 54 North (Ripon area) so the clouds on the horizon are at latitude 63 North which is 1 degree north of the Faroe Islands.

The bright star Capella provides a guide to the locations of the highest edge of the clouds. Capella is very close to 10 degrees above the northern horizon (measured via Stellarium). In the 3 panoramas the top of the clouds range from 5 degrees to 9 degrees above the horizon, This gives (via the good old triangle sine rule and angle sum rule):

@ 5 degrees above horizon - cloud latitude = 59.3 degrees; line of sight distance = 600 km (between Orkney and Shetland Islands according to map)

@ 9 degrees above horizon - cloud latitude = 57.7 degrees; line of sight distance = 424 km (over Northern Scottish Highlands)

The direct line of sight distance to the furthest visible clouds (right down on the horizon) is tan (9) = distance / 6371. So distance to clouds = 0.1582 * 6371 = 1009 km - wow! some distance away!!!!          

Pretty much taken from my back garden then Tonk.  Nice images.

[Essex nightsky]

I was just starting to get into some wide field deep sky imaging then the sun decided to press pause on that one (uk 52*N)... So am thinking, reconfigure eq mount (attach ra drive to declination slo motion control with ra axis parallel to ground) and try some panning, day-to-night / night-to-day (holy grail) time-lapse sequences

[Pete Presland]

Same as you of course, seen one small display so far this season.