NLC 2010-05-16/17
From chi and h
Contents |
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
This 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).
