Start of Noctilucent Cloud Season
John Murrell
The Noctilucent Cloud Season (NLC) generally starts in the Northern hemisphere around the 1st of June so you need to get your cameras ready if you wish to image any this year. Lots of details on how to do this on my website.
The only fly in the ointment is that the AIM satellite has not seen any NLC yet. Copies of the ‘daily daisy’ are published on spaceweather.com , however to date the images have been blank. That coupled with the unusual gap in NLC in the southern hemisphere last southern summer may indicate that something unusual is happening to the mesosphere.
The other useful place to check for the possibility of NLC are the plots at http://www.geos.ed.ac.uk/~hcp/meso_ts/ basically the temperature has to be low and there has to be some moisture. It’s not an exact science but a temperature less than 160 K and a level of water above 4 seem to be required for NLC to form. For those who are not aware the temperature of the Mesosphere falls in the summer even though the surface temperature rises. It is not understood where the moisture in the Mesosphere comes from – it is sealed from the lower atmosphere. Two suggestions are either meteors or large volcanoes, the volcanoes may also provide the nuclei the water needs to condense on to form the ice clouds.
Details of the unusual frequencies over Antarctica can be seen at http://spaceweather.com/archive.php?view=1&day=01&month=03&year=2015 .
Hope you get to see some this year.
Good Observing
John Murrell
Astronomer Without Portfolio
Website www.JohnMurrell.org.uk
Roy Easto
Is it best to have a good North West horizon or doesn't it matter? My two local night spots are quite poor in this direction.
Roy
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John Murrell
Hi Roy,
You need a good NW to N horizon for the evening NLC and N to NE for the morning NLC – basically the direction the Sun is at the appropriate time NLC can be seen. They can be seen perhaps 30 degrees above the horizon at the start and end of the visibility period and sink lower as the Sun dips lower below the Horizon. A good sea horizon would be great ! Light pollution should not be too much of a problem as they are reasonably bright and the sky will probably be mostly (normal) cloud free to see them.
I use an upstairs window for the observations but a few more meters would be great as I am observing over the top of a street light which has to be kept out of the FoV. Perhaps it is time for a couple of RasPi cameras on a TV aerial mast. This would enable me to have a camera towards the NE as well – at present the window obscures the view in that direction. The only morning images I have got are with a hand held camera rather than my mounted automatic camera.
I have lots of images of aircraft trails, the odd bat and other birds amongst the few NLC images I have recorded.