Cumulus Support

Steve,

My website this morning shows sunrise at 07:38 and sunset at 17:08. Assuming the sun is highest at noon that means it rises 4h 22m before noon but sets 5hr 08m after it.

That seems illogical. Perhaps the sun isn't at its highest position at 12:00. From those times local noon appears to be 12:22. Is that possible?

RayProudfoot wrote:Steve,

My website this morning shows sunrise at 07:38 and sunset at 17:08. Assuming the sun is highest at noon that means it rises 4h 22m before noon but sets 5hr 08m after it.

That seems illogical. Perhaps the sun isn't at its highest position at 12:00. From those times local noon appears to be 12:22. Is that possible?

In Cheshire, you are west of the Greenwich meridian, so your "local noon" (i.e. when the sun is directly south of you) is always going to be later than 12:00 - by about 10-15 minutes.
You should also read this article for some background on sunrise/set times and their apparent discrepancies: https://en.wikipedia.org/wiki/Equation_of_time

I did consider whether my longitude (2° 11'W) would be a factor but what I don't know is where those sunrise / sunset times are based on. London or local?

1 degree = aprox 4 mins so my longitude would make the sun highest at 12:09. That's still 13m difference. Hence my question.

Solar Noon where you are is at about 12:24 today - http://suncalc.net/#/53.3639,-2.195,14/2016.02.10/10:00

Thanks Steve. That confirms the times shown by Cumulus are local. I have to admit at being surprised local noon is so much later than actual noon.

I entered Greenwich into SunCalc and even there local noon is 12:15. Has someone tilted the earth?

As you'll see from the graph in that Wikipedia article, the difference is close to its maximum for this time of year.

Indeed. A massive 14 minutes! You learn something new every day. Thanks for the links gents.

I found this site which also shows local noon time. http://www.timeanddate.com/sun/uk/manchester

Steve, is there a tag for local noon time? Strikes me it would be a useful addition.

The library that I use for sunrise etc doesn't supply local noon.

That's a shame. Could they not be persuaded? It's quite important as I found out today.

The library is no longer under development. But then again, neither is Cumulus 1. The library I use for MX doesn't supply it either.

Okay, thanks.

FWIW The 'Bashewa' astro script calculates MerPass of the sun, a big scipt if you just require one variable though

Way beyond my capabilities I'm afraid. But at least I'm now aware how much it can vary from 12:00 so I'll be alert.

With the kind help of JDC (John) and Steve I now have Local Noon on my homepage.

Public statement of appreciation to both for their help and expertise. Thanks chaps!