NLCs - May 14/15th

[martinastro]

On the evening of May 14/15th from 23.00 - 23.30 BST I observed yet another NLC display which formed during the twilight hours over N. Ireland. When I left home I was concerned about the bright waxing Moon between Virgo and Leo which could cause a few false alarms but when I got to my high location there was no doubt at all. There was an obvious NLC display in the NW to N sky sector extending 60 degrees in azimuth but only a shy 7 degrees above my local horizon. The display was a fairly conspicuous type 1 very soft veil glowing a blue-white colour which I rated at 2 in magnitude. White was the dominating colour however after 15 min's the display began to rapidly lower in height and fade to a magnitude value of 1. The colour then became blue dominated and it was then that I could make out numerous but very delicate low surface brightness type IIa bands clustered within that blue cut-off point. I text John McConnell who then drove out the road to a good location and confirmed the presence of a very weak NLC display. By 23.30 the display was a very sorry sight and faded from naked eye visibility. This was hardly a spectacular display but shows that Noctilucent Clouds are forming earlier than usual. I hope to be seeing good structured displays by early June.

On the image the blue-white glow above the orange horizon murk are the NLCs. Subtle structure can be seen. This was a 10 second exposure at ISO400, with a lens aperture of F/3.2 using a UV filter. Auriga and Capella are to the L, Perseus at centre with Algol almost 'touching' the NLCs. To the R is Andromeda with Gamma embedded within the NLC. Time of image: 23.24 BST. Cassiopeia is the to the upper R.

[markt]

Like Martin I was out looking for NLC's last night, and I have to say i've thought the twilight arc slightly different than what i'm used to. I took a couple of pics for good measure



22:33GMT 18mm f2.8 iso 400 3.2secs



22:44GMT 18mm f2.8 iso800 1.3 secs

Not quite as scenic a landscape as Martins I know but similar sky conditions...

[martinastro]

Nice one Mark, I can see that enhancement to the twilight no problem. You got your images earlier than I did so that helps to cover a wider time frame.

Has anybody else been out?

[tmcewan]

May 15, 2008 16:56:02 GMT martinastro said:

Has anybody else been out?

Hi Martin,

Yes, I was out from 2145 UT until it became overcast around 2235 UT. There was what superficially looked like NLC but examination with binoculars soon convinced me that this was just thin streaks of tropospheric cloud across the twilight arch, creating a pseudo NLC (with moonlight, no doubt, contributing to the effect). Here's a photograph from 2149 UT:

[Bill W]

Hi,
I was also observing from 22.00BST (the sun gets to the -6 degrees mark at around 22.20) to 23.00BST.
Same here, with binoculars I couldn't see anything.
I also ran a video camera from 21.00BST (14th) to 07.00 (15th) and didn't record anything that would convince me that there were NLC present.
Similarly last night 15th/16th, got some nice hi res time lapse and plenty of stills, only low level tropo cloud in the glow.
There were a few faint "bands" well above the glow which I would say were moonlight clouds.
cheers,
Bill.

[martinastro]

Did you see anything before dawn this morning guys?. Very obvious blue veil here at brighness value of 3. 10 deg high and 80 deg long. Very similar to first sightning on 5th.

[tmcewan]

May 16, 2008 11:57:07 GMT martinastro said:

Did you see anything before dawn this morning guys?. Very obvious blue veil here at brighness value of 3. 10 deg high and 80 deg long. Very similar to first sightning on 5th.

Hi Martin,

I was out from 2130-2300 UT and didn't see anything, apart from, that is, some thin streaks of normal cloud similar in appearance to the previous night.

Tom

[martinastro]

Cheers for the reply Tom, good to know others are out watching the twilight regions.