NLCs - May 13/14th May 14, 2008 15:31:45 GMT
Post by martinastro on May 14, 2008 15:31:45 GMT
Since my first observation of NLCs on May 4/5th I have been watching the twilight sky each evening and again before dawn. Despite hazy skies hampering any NLC observation the sky gradually improved with increasing transparency during the last few days. On the morning of the 13th a pre dawn watch showed nothing then on the evening of the 14th I was pretty sure that the twilight sky looked suspicious. I figured that any developing activity could reveal itself before dawn the following morning. I was out during the hours before dawn and after a lengthy and eye-opening encounter with the local police which resulted in my camera being searched (there have been sinister events going on here at night) but after explaining about my astronomical background my story was accepted and I was on my way. I set up the camera at the same location as my last observation from a high vantage point in Maghera and immediately spotted NLCs at 02.45 BST. There was no question that the pre dawn sky was glowing yet again, the NLC had no obvious structure at first, but consisted of a uniform blue-white coloured type 1 veil which was fairly bright so I gave it a value of 2.5 on the brightness scale. It was very soft and diffuse and was only 7 degrees above the horizon. The display extended from the N to NE, a minimum distance of 80 degrees in azimuth. The display was located within Auriga, S. Perseus, Aries and Pisces. A low level blanket of tropospheric cloud and murk blocked the main body of the display so only the upper section could be seen. I observed the display until 04.00 BST when the twilight became too advanced. During the period of observation the NLCs reached a maximum of 9 degrees in height and sported bright white segments, with averted vision I am sure there was soft low contrast type IIa bands present.
Getting an image was extremely difficult, being an obvious NLC display with the naked eye it was a different story for a digital camera as the dynamic range in brightness and colour was a challenge to record. On the image the bright white-green glow above the bed of orange is the NLC veil. Capella can be seen to the L, Perseus at centre with Algol above the upper limit of the NLC veil. Triangulum and Andromeda are on the R with the core of M31 visible. This is a classic example of the faint low level NLC displays which go missed early (and late) during each NLC season. Having said that, May 14th is still very early indeed!.