Are these NLCs?

[hemiola]

Hi,

I only became aware of NLC about 2.5 years ago, and I'm fascinated about them, although I still know very little about the subject.
At the moment I live in Derry, Northern Ireland, so in theory the location is right. Just 2 nights ago I noticed these clouds on the sky (picture greatly enhanced, original clouds weren't as bright).
Are these NLCs? As I said, the location and time of the year is right, but I noticed them around 1:30 AM, not 30-60 min after sunset, as some sources say.
Any feedback is greatly appreciated.

Alan

[hemiola]

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[Bill W]

Hi Alan,
Welcome aboard. Yes, no doubt about it. The bright clouds are indeed nlc.
A lot of stuff printed about nlc needs to be taken with a pinch of salt.
1.30am is just about true midnight for your longitude. At this time of year and with the solar illumination at that time of night, that's pretty much what they look like.
Depending on the exact conditions they can indeed be seen about an hour after sunset right through to an hour before sunrise. But there is a lot of variability which you'll see for yourself if you start looking out for them regularly.
cheers,
Bill.

[hemiola]

Hi Bill,

Thanks a lot for the confirmation... at least I know what I'm looking for from now on
Something you said caught my attention:

Jul 13, 2011 13:25:38 GMT Bill W said:

1.30am is just about true midnight for your longitude.

I wasn't even aware of the concept of "true midnight" till now. Is there a quick, straightforward relationship between this and longitude (and time of the year or whatever else comes into play). More importantly, are nlc more visible around true midnight (I assume it is, otherwise u would not have mentioned it).
One last question, is it true that nlc cannot be predicted?

[Bill W]

Hi,
"True midnight" is only an expression I use to keep things clear in my own mind!

As the UK is on BST which is one hour ahead of UT, this means of course that "midnight" on the clock is only 23.00UT. However as NLC are seen when they are being illuminated it's a good idea to have in mind the real position of the sun. Since both civil and UT are referenced to zero degrees longitude it means that in real terms the sun will be at it's lowest point below the northern horizon a little bit later than this, in both our cases, as we are west of the zero degree meridian.

I don't know for sure but as you're about 6 degrees west this means that the sun will be at it's lowest point below the northern horizon approx 25 minutes after "midnight" UT or about 1.25 am BST.

As NLC are very variable it's not that NLC are more visible at "true midnight" it's just that if they are there they tend to be seen in a smaller part of the sky, due north. Just like in your pictures. Before (and after) this time when the sun is not so far below the horizon and illuminating a great portion of where NLC occur they'd be seen more extensilvely and higher in the sky.

It's all just observational perspective!

I don't know if that's makes it any clearer!!!

As for predicting NLC, there are indicators available from radar and satellites but I'd say they're not predictable to any great degree other than in general terms that when conditions are right they might be there....

You just need to keep watching!

cheers,
Bill.