Just been outside.
It's 19:00
I was outside at 0700 this morning.
It's the same darkness at 07:00 and at 19:00
I've kept an eye on the light-level because I suspected that the light was the same 07 and 19
Autumn Equinox was in September.
Wot's goin' on?
Equinox?
Re: Equinox?
The actual way of deciding it is the equinox is on the length between sunrise and sunset and by that definition the nights are now longer than the days.
Judging the same light level, without even instruments to help, is a bit too subjective.
Plus it is an state which can exist at any point for about twenty minutes either side of sunrise and sunset.
Judging the same light level, without even instruments to help, is a bit too subjective.
Plus it is an state which can exist at any point for about twenty minutes either side of sunrise and sunset.
Yma o Hyd
Re: Equinox?
Ah, so the equinox - meaning equal night - has a specific definition, but that doesn't take into account the local actual sunrise and sunset.
I would say we here are at Equal Night today. No doubt other places have different dates.
From what I remember from my geography O level, the equinox is when the sun is directly overhead the equator at noon.
I would say we here are at Equal Night today. No doubt other places have different dates.
From what I remember from my geography O level, the equinox is when the sun is directly overhead the equator at noon.
Mick F. Cornwall
Re: Equinox?
but that doesn't take into account the local actual sunrise and sunset.
If you are in Cornwall your sunrise may well be twenty minutes after that in London but so will your sunset be.
Yma o Hyd
Re: Equinox?
Sunrise here is late.
Maybe sunrise has a definition, but the sun rises here quite late due to the fact that Devon has a high steep bank across the river.
The Cornwall side is less steep, so sunset isn't too early, but later than the definition of sunset.
Maybe sunrise has a definition, but the sun rises here quite late due to the fact that Devon has a high steep bank across the river.
The Cornwall side is less steep, so sunset isn't too early, but later than the definition of sunset.
Mick F. Cornwall
Re: Equinox?
Yes, it is the time that it would set behind the horizon on an even spherical surface.
Like wise here, we last see the sun quite sometime before it officially sets due to some steepish hills close by.
Like wise here, we last see the sun quite sometime before it officially sets due to some steepish hills close by.
Yma o Hyd
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fausto copy
- Posts: 2809
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- Location: Pembrokeshire
Re: Equinox?
Steepish hills.....steepish hills. 
They're the Preseli MOUNTAINS dear boy!
They're the Preseli MOUNTAINS dear boy!
Re: Equinox?
Does that include atmospheric lensing?
IIRC when we see the sun touch the horizon it has just disappeared over the theoretical one (because of the lens of the atmosphere) - lucky coincidence of timing/scale)
IIRC when we see the sun touch the horizon it has just disappeared over the theoretical one (because of the lens of the atmosphere) - lucky coincidence of timing/scale)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Re: Equinox?
quote from Wikipeadia
"An equinox is the moment in which the plane of Earth's equator passes through the center of the Sun's disk,[2] which occurs twice each year, around 20 March and 23 September.
On an equinox, day and night are of approximately equal duration all over the planet. They are not exactly equal, however, due to the angular size of the sun and atmospheric refraction. The word is derived from the Latin aequinoctium, from aequus (equal) and nox (genitive noctis) (night"
"An equinox is the moment in which the plane of Earth's equator passes through the center of the Sun's disk,[2] which occurs twice each year, around 20 March and 23 September.
On an equinox, day and night are of approximately equal duration all over the planet. They are not exactly equal, however, due to the angular size of the sun and atmospheric refraction. The word is derived from the Latin aequinoctium, from aequus (equal) and nox (genitive noctis) (night"
NUKe
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Re: Equinox?
Anyone, by any chance, forgotten it's British Summer Time?
7am BST = 6am GMT; likewise 7pm BST = 6pm GMT. At this time of year, the Equation of Time is about -13 minutes - but this discrepancy is roughly cancelled out by the longitude difference between Greenwich and the West Country. So you can expect the sun's azimuth to be due east at 7am BST - and due west at 7pm - with the same altitude above or below the horizon at both times. So not surprising the light levels are the same.
Moreover, judging light level by eye is a very subjective thing. Unless you used a light meter, that is.
7am BST = 6am GMT; likewise 7pm BST = 6pm GMT. At this time of year, the Equation of Time is about -13 minutes - but this discrepancy is roughly cancelled out by the longitude difference between Greenwich and the West Country. So you can expect the sun's azimuth to be due east at 7am BST - and due west at 7pm - with the same altitude above or below the horizon at both times. So not surprising the light levels are the same.
Moreover, judging light level by eye is a very subjective thing. Unless you used a light meter, that is.
Suppose that this room is a lift. The support breaks and down we go with ever-increasing velocity.
Let us pass the time by performing physical experiments...
--- Arthur Eddington (creator of the Eddington Number).
Let us pass the time by performing physical experiments...
--- Arthur Eddington (creator of the Eddington Number).
Re: Equinox?
I was just observing by eye, that the daylight level didn't seem even at 12hrs, in fact the similar light levels were maybe 12.5hrs.
Mick F. Cornwall
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old_windbag
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Re: Equinox?
[XAP]Bob wrote:IIRC when we see the sun touch the horizon it has just disappeared over the theoretical one (because of the lens of the atmosphere) - lucky coincidence of timing/scale)
Yes and you also get the "teardrop" type effect too with sun on horizon. This book below is very good for explaining all manner of atmospheric effects with light and colour. I once had it from a library as purchae price rather high but I'd imagine by now there'll be an online pdf somewhere. It covers umpteen things including refraction, castles in the air, sundogs, sun pillars......
https://www.amazon.co.uk/Light-Color-Outdoors-Mgj-Minnaert/dp/0387979352
The dynamo light is clearly having an effect on mickf's light perception.
Re: Equinox?
The beer as well maybe?old_windbag wrote:The dynamo light is clearly having an effect on mickf's light perception.
Dynamo lighting going well BTW.
Mick F. Cornwall
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old_windbag
- Posts: 1869
- Joined: 19 Feb 2015, 3:55pm
Re: Equinox?
Mick F wrote:Dynamo lighting going well BTW.
Where bicycle lighting is concerned we have never had it so good. Modern led lights, dyno form or battery are phenomenal.... when designed well but we know the importance of a good beam pattern.
When I look back at my cateye hl1500 nimh battery light it staggers me to think I'd use such. It worked fine in a cityscape but when I used it in a rural setting it was a tiny rectangle of light about 15ft ahead. But I once dreamed of owning a lumicycle halogen, thank god LED's have advanced and I was saved the expense.