This summer has been a bit of a weird one. One day it is sunny and 32C/90F, while the next day it’s cloudy, raining and cold. It’s not just been a typically varied English summer, it’s been strange with the temperature variations – I wish the Jet Stream would sort itself out and get north of Scotland, where it is supposed to be and not lurking over the south of England! Observing opportunities have been quite rare. This time last year, I’d had 4 observing sessions in August but, this year, it’s been one. Not all the nights have been cloudy, there have been 5 clear nights so far (still, a pretty crappy return nonetheless) but most have been around the gibbous Moon. August is never a good month, traditionally it is a mixed bag so I’m hoping that as autumn sets in, the percentage of clear nights will rise – this is usually the case.

Our local astronomy society, Vectis AS, has a Unihedron Sky Quality Meter for members to use. I have currently got it, having picked it up at last week’s Perseid Party, and have only played with it so far as the Moon is in the sky. Under a 95% gibbous Moon last week, the reading was 19.45 which equates to 5.1 limiting visual magnitude. Last night, with a rising 75% gibbous Moon in the sky, the reading was 20.60, which is a naked eye visual magnitude of 5.9. I’m looking forward to using it under a really dark, Moonless autumn or winter night. I might get myself one of these, they’re expensive at around £145 each but it will give a more objective reading of the sky quality than just looking up, hunting for the faintest star visible and saying ‘Oh, that’s 6.0’ or whatever – it’s easier, too. My friend Stephen, who owns the site where we had our Perseid gathering last week, has one permanently fixed to his roof and gets readings in the high 21s. My home site is not as dark as that one (I am located just outside the ‘Bay Area’ of Sandown and Shanklin, although it’s not as bad as it could be) as he’s in a blue zone while I am in a green zone, but I should get readings in the high 20s at least, and the 21s on very good nights.

I did get a short session in last night, 19th August, and it was a short one, too. I got 50 minutes before the Moon and clouds interfered, which I’ll put in a separate post.