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NLC 2010-05-16/17

This night is an example how tropospheric cloud can be mistaken for NLC. In theory, the former is dark and the latter bright compared to clear sky. If the observation is of a dark and bright banding, this can be caused by either type of cloud.

This night was also on the whole clouded out, so in the end no report at all is sent to the BAA or the NLC Observers' Home Page. But I leave the would-be report to the BAA and the images here as examples of fake NLC.

Would-be BAA report

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

Name of observer: Horst Meyerdierks
Location: Stichill Eastfield, 55.7N 2.4W
          unattended dSLR with limited field of view A ~310-20, h ~0-40
          images every 15 min
Date: 2010-05-16/17

  UT   forms  bright   height   azimuth   comments
               ness   top bot  left rght  e.g. weather
-----  -----  ------  --- ---  ---- ----  --------------------------------
21:00  X                                  cloud patches all over
21:15  X                                  cloud patches all over
21:30  X                                  cloud patches all over
21:45  X                                  cloud patches all over
22:00  X                                  cloud to h 10, on left to h 20
22:15  NLC?     2       8      <310   >5  cloud patches, NLC likely cirrus or volcanic ash
22:30  NLC?     1       7                 cloud patches, NLC likely cirrus or volcanic ash
22:45  NLC?     2       4      <350   >5  cloud, NLC likely cirrus or volcanic ash
23:00  NLC?     1       3      <355   >8  cloud, NLC likely cirrus or volcanic ash
23:15  X                                  cloud cover almost complete
23:30  X                                  overcast
23:45  X                                  overcast
00:00  X                                  overcast
00:15  X                                  overcast
00:30  X                                  overcast
00:45  X                                  cloud cover almost complete
01:00  X                                  cloud cover almost complete
01:15  X                                  cloud cover almost complete
01:30  X                                  cloud cover almost complete
01:45  X                                  cloud cover almost complete
02:00  X                                  cloud cover almost complete
02:15  X                                  overcast
02:30  X                                  overcast
02:45  X                                  overcast
03:00  X                                  cloud at bottom, right and top
03:15  X                                  cloud patches all over

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

Images

Listed below are the images with sightings of fake NLC. These have been processed merely to adjust the brightness for underexposure. For some there may also be an unsharp-masked version of the image.

  UT    exp    A    hSun  h15   h85  stretch  image     (masked)
----- ------ ----- ----- ----- -----  ----- ---------------------
22:15 15.000 333.3 -11.5  -2.9  15.1  0-200 q27704.jpg m27704.jpg
22:30 30.000 336.8 -12.4  -3.4  10.5  0-150 q27710.jpg
22:45 30.000 340.4 -13.2  -3.9   7.9  0-80  q27716.jpg
23:00 30.000 343.9 -13.8  -4.3   6.2  0-50  q27722.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).