Since 2009 I have tried to keep a record of clear nights and cloudy ones, and I’ve tried to be as accurate and as consistent as possible, with other people keeping a note of the conditions for me when I am away. Obviously it’s far from scientific, especially as I only started this in July 2009 and it’s a case of me keeping an eye on the sky and writing down what I see, but it gives some overview of the amounts of clear nights v cloudy ones.
2012 seemed to be a diabolical year for astronomy, the weather was useless, particularly through the summer months, with August in particular being very cool and wet, and I did very little from May onwards. However, looking at my clear sky spreadsheet, which I’ve kept going through all that time, paints a somewhat different and not quite so bleak picture which is somewhat surprising. I guess another factor in putting astronomy aside for a while has been burnout; simply put I’d been thinking of and doing nothing but astronomy for the previous few years so, combined with the cold, miserable summer we had, a fairly cloudy autumn season and a very cold and snowy winter, it’s not surprising that I put it aside in favour of my other interests for a while.
Anyway, this is what I have so far (ignoring the latter half of 2009, as I only started doing this in July of that year). For the purposes of this, I consider ‘partly clear’ to mean 50% or more of the sky to be clear; these are ‘observationally usable’ nights, in that I can at least do something.
2010 – 116 totally clear nights (32%); 54 partly clear nights (15%); Total = 170 (47%)
2011 – 104 totally clear nights (28%); 52 partly clear nights (14%); Total = 156 (43%)
2012 – 101 totally clear nights (27%); 48 partly clear nights (13%); Total = 149 (41%)
2012 was a leap year and 29 February was partly clear and not cloudy.
It looks like a downward trend, we’ve gone from 116 clear nights in 2010 to 104 in 2011 and 101 last year, but as this is so far only representative of three complete years, it’s too early to say whether this will continue. Obviously I hope it won’t but a decade or, preferably, two of this unscientific method of mine may reveal more.
As I type, the weather is quite chilly, windy and showery, not unusual for early May but I sincerely hope we get a reasonable summer this year. Even an okayish summer will be better than last year.