NLC 2015-07-02/03

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 compact camera with limited field of view
          A ~325-35, h ~0-40; images every 15 min
Date: 2015-07-02/03

   UT     forms  bright   height   azimuth   comments
                  ness   top bot  left rght  e.g. weather
--------  -----  ------  --- ---  ---- ----  --------------------------------
21:45:02  0
22:00:02  0
22:15:01  0
22:30:02  0                                  cirrus to h 10
22:45:02  0                                  cirrus to h 10
23:00:10  0                                  cirrus to h 10
23:15:18  0                                  cirrus, above h 10 as fake NLC
23:30:32  0                                  cirrus, above h 10 as fake NLC
23:45:32  0                                  cirrus, above h 10 as fake NLC
00:00:32  0                                  cirrus, above h 10 as fake NLC
00:15:33  0                                  cirrus, above h 10 as fake NLC
00:30:32  0                                  cirrus, above h 10 as fake NLC
00:45:20  0                                  cirrus, above h 10 as fake NLC
01:00:32  0                                  cirrus, above h 10 as fake NLC
01:15:19  0                                  cirrus, above h 10 as fake NLC
01:30:09  0                                  cirrus, above h 10 as fake NLC
01:45:02  0                                  cirrus to h 10
02:00:02  0                                  cirrus to h 10
02:15:01  0                                  cirrus to h 10
02:30:01  0                                  cirrus to h 10
02:45:01  0                                  cirrus to h 10

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

Name: Horst Meyerdierks
Country: Scotland
Location: Edinburgh
Date: 2015/07/02-03
Start: 21:45
End: 02:45
Comments: Some cirrus.

Images

Listed below are the images illustrative 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.

• #3569 illustrates "fake NLC", where cirrus at higher alitude above the horizon appears bright against the background sky. This is not NLC, as can be detected from its West-to-East movement (from consecutive images, and contrary to most real NLC), its mimicking the radial pattern of the dark cirrus below, and from it extending to higher altitude above the horizon than the sunlight limit at 85 km alitude above ground.
• #3579 illustrates "fake NLC", where cirrus at higher altitude above the horizon appears bright against the background sky. This is not NLC, as can be detected from its West-to-East movement (contrary to most real NLC), its grey rather than blue colour, it matching neither form I nor form IV, the gradation of colour from grey to white at higher altitude, and from it extending to higher altitude than possible for NLC.

   UT      exp    A    hSun  h15   h85  stretch  image   (masked)
-------- ------ ----- ----- ----- -----  ----- -------------------
00:30:32  8.000   3.2 -11.0  -2.6  19.0  0-255           m3569.jpg
01:00:32  8.000  10.2 -10.5  -2.3  25.1  0-255 q3579.jpg

exp: Exposure time in seconds (200 ISO, f/2.8).
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).