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NLC 2011-05-18/19

BAA report

The report to the BAA Aurora Section gives an overview of the night, which times were cloudy, free of NLC, or with sightings of NLC.

Name of observer: Horst Meyerdierks
Location: Royal Observatory Edinburgh, 55.9N 3.2W
          unattended dSLR with limited field of view A ~325-35, h ~0-40
          images every 15 min
Date: 2011-05-18/19

  UT   forms  bright   height   azimuth   comments
               ness   top bot  left rght  e.g. weather
-----  -----  ------  --- ---  ---- ----  --------------------------------
21:00  0                                  some cloud
21:15  0                                  some cloud
21:30  0
21:45  0
22:00  0
22:15  0
22:30  0
22:45  0                                  cloud to h 5
23:00  0                                  cloud to h 5
23:15  X                                  cloud to h 5
23:30  X                                  cloud to h 5
23:45  0
00:00  0
00:15  0
00:30  0
00:45  0
01:00  0                                  fake NLC at cirrus lower boundary
01:15  0                                  fake NLC at cirrus lower boundary
01:30  X                                  fake NLC at cirrus lower boundary
01:45  X                                  fake NLC from banded cirrus
02:00  X                                  cirrus to h 15
02:15  X                                  cirrus to h 10
02:30  X                                  cloud
02:45  0                                  cloud to h 10
03:00  0                                  cloud to h 10
03:15  0                                  cloud to h 15

forms: I: veil
       II: bands
       III: waves
       IV: whirls
       NLC: other than or multiple of I-IV
       0: no NLC
       X: no decision possible (mist, cloud etc.)
brightness: 1: very weak
            2: clearly detected
            3: clearly visible
            4: very bright
            5: extremely bright

NLCnet report

The main periods of absence of NLC are reported to the NLC Observers' Home Page:

Name: Horst Meyerdierks
Country: Scotland
Location: Edinburgh
Date: 2011/05/18-19
Start: 21:00
End: 01:15
Comments: some cloud

Images

As this is the time of the first reported NLC sighting, the relevant images are listed below. These have been processed merely to adjust the brightness for underexposure.

  UT    exp    A    hSun  h15   h85  stretch  image      (masked)
----- ------ ----- ----- ----- -----  ----- -------------------------
21:00  0.025 316.0  -4.6   9.1 173.1  0-255 q11762.jpg
21:15  0.077 319.3  -6.0   2.3 168.3  0-255 q11764.jpg
21:30  0.250 322.6  -7.3   0.3 158.4  0-255 q11766.jpg
21:45  0.600 325.9  -8.5  -0.8 125.7  0-255 q11768.jpg
22:00  1.300 329.3  -9.7  -1.7  49.2  0-180 q11771.jpg
22:15  4.000 332.7 -10.7  -2.4  23.0  0-255 q11775.jpg

exp: Exposure time in seconds (400 ISO, f/3.5).
A: Azimuth of the Sun (degrees).
hSun: Altitude of the Sun (degrees, negative below horizon).
h15: Max. altitude of sunlight at 15 km height (degrees).
h85: Max. altitude of sunlight at 85 km height (degrees).
stretch: Contrast stretch (0-255 means no stretch).