Defining a noctilucent cloud

[JOC]

OK, I've taken some time to try and find where to post discussion on the imaging challenges, but can't find an open thread that I can post on.

What I was wondering is if there is a definition of what these 'Noctilucent Clouds' are.  I've look up on Wikipaedia, and understand that they are seen after the sun sets and that they are high clouds - I've also looked at the pictures, but it seems to me that it doesn't probably cover all clouds illuminated at this time and is there a way of def. knowing if you are looking at this type of cloud (and therefore eligible) vs. any other?  Or is it that any high cloud in the sky after the sun sets and illuminated in that way will do?  Many thanks

If this should be on a discussion thread somewhere then please feel free to move it, but I can't see where to post it.

[oobydooby]

I will ask Ken Kennedy who was co-ordinator of the NLC team at BAA until fairly recently and is still actively involved, has written in the BAA journal for several years on the subject and is Hon Member of our society.  I am sure he will have a definitive answer.

I have been looking for these for several season without any luck, but can be sure I will know an NLC when I see one.

You might like to take a look in our web-site galleries, there are several pictures of NLC from Ken and another of our members,in the "Earth" gallery - even a few movies somewhere.

https://stargazerslounge.com/forum/227-imaging-challenge-4-noctilucent-clouds/

There's the link to start a topic for this challenge, by the way.

[JeremyS]

Hello JOC,

there is an article on Noctilucent Cloud (NLC) by the BAA's Aurora & NLC Section Director, Sandra Brantingham, on the BAA website here: https://britastro.org/node/9456

I think that should help you.

Also have a look at the Section website here: http://www.britastro.org/aurora/ and the NLC page here: http://www.britastro.org/aurora/nlc.htm

Jeremy

[oobydooby]

I made a boo-boo.  Our Ken is NLC co-ordinator for Europe.  Sandra Brantingham and he will be at Edinburgh on 24th June with NLC and aurora information.  The exhibition is from 10.00 am to 5.00 pm at the National Museum of Scotland,  Edinburgh.  There will be astronomical items from every section of the BAA, so would be an interesting day out for everyone.

Not so good for anyone living in deepest Essex, unfortunately

[lukebl]

I saw my first NLCs about 6 years ago, after imagining them for ages, and trying to turn Cirrus clouds into them. They're one of those things that, once you see a real one, you realise that there's nothing really like them. Very ethereal. Glowing clouds against a dark sky late into the night.

Not much of an identification guide, I know, but good luck everyone!

[JeremyS]

There's a nice time lapse video of NLC, showing how they compare to normal cirrus, on this page: https://britastro.org/node/7770

It's the first post on the page by Nick James' who's video shows NLC over Chelmsford last summer.

Jeremy

[RichM63]

It is a good question.

I always thought that they were the ones that went behind the Moon!

[StuartJPP]

I have seen them on a few occasions now, usually around midnight, i.e. well after the sun has set.

If there are other "normal" clouds in the sky at the same time, they obscure light/stars.

I am not sure what the definition of them is but I am sure the challenge isn't that restrictive as long as they fall into that category.

[JeremyS]

There's a new article on "NLC and what to look for" by Sandra Brantingham here: https://britastro.org/node/10472

Enjoy!

Jeremy

[Pete Presland]

Saw my first display about 3 years ago after a few false alarms. After I saw them I wonder how I could have had a false alarm  they are very distinctive especially at 2.30am.

[barkis]

My understanding  is that noctilucent clouds are exposed when they are at very high altitude, and the sun has set well below the
horizon, but the sunlight illuminates them, thereby making them visible in early  night skies.
Of course as the earth revolves and the sun is blocked by  the earths disc, the noctilucents  fade and disappear. Some light may still be refracted through the Earths atmosphere, but I'm not sure it would be sufficient to light up the clouds, considering the amount of dust in our atmosphere, which is
responsible for a Copper coloured Moon during a lunar eclipse
Not sure If High altitude ice crystals too  play a part in this phenomena.
 

[JOC]

This is an interesting if difficult and frustrating subject, first you have to work out if Mother Nature has delivered on some of these clouds, then you have work out how to take photos of them, it's very difficult to focus when you don't have much to aim at!  Apart from the obvious contrails do you think I've caught any in the backgrounds?

 

[bejay1957]

Not obvious NLCs to my eyes; what was the time for these photos, and indeed direction - I'm assuming that is sunrise in the second one?  
Due to increasing height of foliage, cloud, and LP haven't seen a good display for a couple of years; they are one of those things that are very obvious once you see them - I know kind of a Catch 22..  
Photographing them isn't too tricky, I have used my Panasonic compact and/or travelzoom cameras in their night-shot mode

[JOC]

6 hours ago, bejay1957 said:

I'm assuming that is sunrise in the second one?  

It was actually about 22:45 last night!  Both taken West to North West around that time.  Nice pic BTW

[bejay1957]

2 hours ago, JOC said:

It was actually about 22:45 last night!  Both taken West to North West around that time.  Nice pic BTW

Ah, perhaps a tad early, best NLCs tend to be around/after midnight, and in the north; some good ones seen from Oxfordshire last week were at 02:50 - well after I'd called it a night here!

Got lingering Ci all around my N horizon now, not sure if it will clear later; will be too late when I go out to greet the sunrise tomorrow..

[JOC]

So was this a noctilucent cloud please?  NB.  I did like that I appear to have got planets in these too.