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BBC Weaher Forecast - A Great Tool Used Correctly.


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Hi everyone.

I use the BBC weather website to give me hr by hr reporting. This summer i generally check to see if the night they report as "clear sky". I always check 1hr to 30 mins before heading out as the weather can change or the onset of clear skies can easily be pushed back by an hr or two!

The site is: BBC Weather | London

You can insert the postcode that you intend to visit/stargaze at for finer accuracy.

I have a question for the experts. Viewing the BBC hr by hr report, to the right is a humidity from 0 to 100% and below it is a visability prediction varying from poor to exellent.

This is where the confusion comes in. I have been out on nights where the report says 85% humidity and "Very Good" visability. Yet when i get to my site. The sky is covered in a fine mist! And the stars look fuzzy with halo glows around them. So i assumed that for astronomy, lower humidity generally below 60% is good for us. And the "visiabily" prediction is for the public in terms of how clear the general atmosphere/street look. Am i correct so say we should mainly judge a site by the humidity predicition? Love to hear your experiences.

Edited by Pingster
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I've always thought of 'visibility' as a reading used mainly by airports and sailors etc, where long distance clarity is essential for safety reasons. I only consider the viewing conditions good if there is a low humidity AND and a good visibility reading. Presumably visibility is affected by a number of different factors, including humidity.

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Visibility is usually measured horizontally and improves as you look upwards. For instance, some days I cannot see the Isle of Wight across the sea and some days it is perfectly clear. This has little bearing on stargazing. I don't find the BBC forecast very accurate and much prefer Weather Pro on my iPhone and iPad for 'by the hour' updates to my exact location - which, being on the coast, is quite different from half a mile inland.

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Hi virtualpilot, i agree with you, there are lots of factors. The best ideal would be below 50% humidity and excellent visability. I am keeping an keen eye for these conditions!

I kinda missed my point in the post, what i was ment to say is for beginners like myself. When using the BBC prediction, dont rush out to a dark site just because the Visability is "Excellent", take the humidity into account. Because from my experience, if its above 70% the stars and DSO are not enjoyable to view. They are too difficult to focus on, look 'blobby' and your kit has a good chance of dewing up quickly.

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Personally, I've found Metcheck to be quite unreliable over the last 6 months or so. Even the Beeb has been more accurate, for me at least. 7Timer is not always too accurate either, For example, both Metcheck and 7timer forecast almost 100% cloud in my locality all evening last night, until around around 4:00 this morning. The BBC forecast clear from 10:00 pm. The BBC was right, Metcheck and 7timer were 100% wrong! :) Oh well! Who to believe? :eek:

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Thats a shame BlackNight, I can only say for my location Metcheck is far more accurate.

BBC is right about 50% of the time, against about 90% for metcheck.

I also like metchecks 3hr forecasts for a couple of days in advance - means I can plan my work around potentially clear nights.

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Forecasts usually have no allowance for local conditions either. If you're by the coast or in the mountains then the 'area forecast' may differ wildy from your local patch.

For instance on the coast in Aberdovey it may be blue skies and sunny (and this it what usually appears on the TV/radio forecast) but up here in the mountains less than 20 milles away, we can be having a terrific thunderstorm and it never gets a mention ???

I have learned that you basicaly have to be ready to set up (and pack up) at a moments notice. One good reason to have a permanent observatory.

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I think with any weather prediction tool you need to check it at least 30mins before you decide to venture out. As the UK weather is known to be very unpredictable.

Yes. Sites like Will it Rain Today? | Rain radar for the UK | Going to rain? | Meteogroup are quite useful for telling you what's coming your way, though they don't have much back history - and don't make any predictions. You have to extrapolate that for yourself

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