Sun declination

Joerg · May 19, 2021, 8:20am

Okay, now I think I get it. Its in July at 145° not in your living room because of the elevation.

Makis · May 19, 2021, 8:33am

Yes that’s right. I could not (and still can’t) figure out how to calculate the elevation and find it easier to do it this way (which probably is not). When I find some spare time I will try to calculate elevation and azimuth as koying says.

koying · May 19, 2021, 8:45am

You don’t have to “calculate”. Just check the values of the azimuth and elevation attributes

Calculating is quite difficult because, e.g.:

azimuth is based on “true north” (i.e. the north pole) and a compass will give you the “magnetic north”, which are not the same
The sun is not a point in the sky, it’s a circle, 2D speaking

Elevation of the window is the “easiest”.
It’s:

distance from the reference point to you window = X
height of the bottom (or top) of the window = Y
elevation = atan(y/x)

seanomat · May 19, 2021, 9:22am

I know, but somehow it didn’t take so I thought I give it another shot. Seems like it doesn’t help though

Makis · May 19, 2021, 9:24am

This is difficult for me to grasp. When I should check the value of the azimuth?
in the below example.

At October 2021 I know that the sun will be inside the living room when azimuth will be at 140.56

In May the azimuth should be at 172.88

I don’t understand how to fill this in your automation

koying · May 19, 2021, 9:33am

What you say doesn’t make any sense
Add or subtract 4h to both calculations and you’ll get completely different azimuths.

Just look into HA the values of the azimuth and elevation attribute of the sun.sun entity when the sun becomes bothersome any day

Makis · May 19, 2021, 9:46am

but this is my problem.
In October the sun becomes bothersome at azimuth 140 and elevation 30
and in May at 173 and 69 accordingly.
based on the values of HA and of the above charts.
Probably I don’t understand something but cannot figure out what

koying · May 19, 2021, 9:53am

But how do you know? Did you actually checked it?

The “charts” only tell you what the azimuth and elevation of the sun are at a given time (time is different on both charts, btw), i.e. tell you exactly the same as HA for now()

finity · May 19, 2021, 9:59am

Maybe I can give this a try…

let’s assume that your window is facing due (true) south. That means that the plane of the window will be from 90 degrees to 270 degrees (from inside the house looking south 90 degrees will be to your left).

That means that any time the sun’s azimuth is between 90 and 270 degrees and the elevation is above 0 and below 90 degrees (above the horizon) the sun WILL BE shining into your window.

You may not notice it at the extremes because it will be shining on the far west wall in the morning (sun azimuth 90 degrees) and shining on the far east wall in the evening (sun azimuth at 270 degrees).

as the day progresses from morning till night the sun will move up in the sky and to the west until it gets to it’s highest point in the arc (which will always be <=90 degrees) and then continue moving to the west but it will be going down in elevation.

During this time if you are in your room in front of the window looking out you will see the sun light (NOT the sun but the sun LIGHT) trace a path from your west wall down across the floor and then continue moving to the east until it reaches your east wall. If you trace the center point of the sunlight shining inside your house thru the window you will trace an arc across your room from the top of one wall to the next top of the next wall across the floor in the middle.

if you never want any sun in your room then the limits of the azimuth will be between 90 degrees and 270 degrees and elevation will be between 0 and 90 degrees.

Most people aren’t that concerned about the extremes tho. It’s UP TO YOU to decide at what point based on the suns azimuth and elevation the sun is bothersome to you. Those values will be somewhere between 90 and 180 degrees for azimuth and 0 to 90 degrees elevation. But nobody can tell you what those numbers are. you have to figure them out for yourself.

BUT, those azimuth and elevation numbers won’t change throughout the year. The only thing that changes is the time that those number coordinates are reached. There may be time of the year that the sun can never reach some of those coordinates at all depending on where you live.

the point is that it’s not the TIME that the sun is at those points in the sky. it’s just the points that matter.

you just have to pick the minimum and maximum azimuth and elevation points where you don’t want the sun shining into your room and set those values as the limits of the numeric_states in the code above.

You can ignore the time entirely since it’s the set of coordinates that we care about. not what time the sun gets to those coordinates.

EDIT: OOPS, Sorry. I meant that west was supposed to be 270 not 180 (180 is due south). Corrected.

DavidFW1960 · May 19, 2021, 10:03am

He seems incapable of grasping that… a whole bunch of people telling him that exact thing but he doesn’t get it because he’s obsessed with time not position…

Joerg · May 19, 2021, 10:05am

Maybe you can elaborate a bit what we are talking about, a window, a terrace or what the sun is shinning on.
It is strange, that you say you have sun at 140° in October (elevation 33°) and no sun at 140° in May (corresponding elevation = 64°), but you will have sun in May at an azimuth of 172° (with a 4° higher elevation)

finity · May 19, 2021, 10:05am

That’s why i took the pains to try to explain it.

Hopefully it’s understandable.

finity · May 19, 2021, 10:08am

It doesn’t matter what the aperture is that the sun is shining thru. the concept is the same.

the size and shape of the aperture only determines the limits of the azimuth and elevation at which the sun is “bothersome”. Which, again, is subjective.

Joerg · May 19, 2021, 10:12am

I think so too, but what he claims is somehow strange. I thought maybe there is a special form of window or an obstacle. Or he misunderstood “azimuth”

koying · May 19, 2021, 10:15am

I somewhat doubt he took measurements the 19th october 2021

Makis · May 19, 2021, 10:16am

Yes, I have check it.

I am talking for a particular window facing the south. The above numbers of azimuth are the exact values when the sunlight gets in my house and on my furniture’s in October and May accordingly.

for example right now the my cover closed just right when the sun touched my floor and the furniture

@ finity thanks for that explanation I will try to understand it

Makis · May 19, 2021, 10:18am

the values are the same with October 2020. In general the values are almost the same for same day of every year

koying · May 19, 2021, 10:19am

Azimuth is not enough. The elevation on 21th June might be above your window, so not bothersome, and below your window on 21st December so not bothersome, either, for the same azimuth.

EDIT: updated graph

Makis · May 19, 2021, 10:28am

below are my calculations with an excel formula
the data of 31/10/2020 + 21/12/2020 are the exact values from HA azimuth sensor

the rest are calculations from the excel file
the values are correct because as soon as light comes in the floor the covers are closing.

31/10/2020	142,81


21/12/2020	125
22/12/2020	125,32
23/12/2020	125,64
24/12/2020	125,96
25/12/2020	126,28
26/12/2020	126,6
27/12/2020	126,92
28/12/2020	127,24
29/12/2020	127,56
30/12/2020	127,88
31/12/2020	128,2
1/1/2021	128,52
2/1/2021	128,84
3/1/2021	129,16
4/1/2021	129,48
5/1/2021	129,8
6/1/2021	130,12
7/1/2021	130,44
8/1/2021	130,76
9/1/2021	131,08
10/1/2021	131,4
11/1/2021	131,72
12/1/2021	132,04
13/1/2021	132,36
14/1/2021	132,68
15/1/2021	133
16/1/2021	133,32
17/1/2021	133,64
18/1/2021	133,96
19/1/2021	134,28
20/1/2021	134,6
21/1/2021	134,92
22/1/2021	135,24
23/1/2021	135,56
24/1/2021	135,88
25/1/2021	136,2
26/1/2021	136,52
27/1/2021	136,84
28/1/2021	137,16
29/1/2021	137,48
30/1/2021	137,8
31/1/2021	138,12
1/2/2021	138,44
2/2/2021	138,76
3/2/2021	139,08
4/2/2021	139,4
5/2/2021	139,72
6/2/2021	140,04
7/2/2021	140,36
8/2/2021	140,68
9/2/2021	141
10/2/2021	141,32
11/2/2021	141,64
12/2/2021	141,96
13/2/2021	142,28
14/2/2021	142,6
15/2/2021	142,92
16/2/2021	143,24
17/2/2021	143,56
18/2/2021	143,88
19/2/2021	144,2
20/2/2021	144,52
21/2/2021	144,84
22/2/2021	145,16
23/2/2021	145,48
24/2/2021	145,8
25/2/2021	146,12
26/2/2021	146,44
27/2/2021	146,76
28/2/2021	147,08
1/3/2021	147,4
2/3/2021	147,72
3/3/2021	148,04
4/3/2021	148,36
5/3/2021	148,68
6/3/2021	149
7/3/2021	149,32
8/3/2021	149,64
9/3/2021	149,96
10/3/2021	150,28
11/3/2021	150,6
12/3/2021	150,92
13/3/2021	151,24
14/3/2021	151,56
15/3/2021	151,88
16/3/2021	152,2
17/3/2021	152,52
18/3/2021	152,84
19/3/2021	153,16
20/3/2021	153,48
21/3/2021	153,8
22/3/2021	154,12
23/3/2021	154,44
24/3/2021	154,76
25/3/2021	155,08
26/3/2021	155,4
27/3/2021	155,72
28/3/2021	156,04
29/3/2021	156,36
30/3/2021	156,68
31/3/2021	157
1/4/2021	157,32
2/4/2021	157,64
3/4/2021	157,96
4/4/2021	158,28
5/4/2021	158,6
6/4/2021	158,92
7/4/2021	159,24
8/4/2021	159,56
9/4/2021	159,88
10/4/2021	160,2
11/4/2021	160,52
12/4/2021	160,84
13/4/2021	161,16
14/4/2021	161,48
15/4/2021	161,8
16/4/2021	162,12
17/4/2021	162,44
18/4/2021	162,76
19/4/2021	163,08
20/4/2021	163,4
21/4/2021	163,72
22/4/2021	164,04
23/4/2021	164,36
24/4/2021	164,68
25/4/2021	165
26/4/2021	165,32
27/4/2021	165,64
28/4/2021	165,96
29/4/2021	166,28
30/4/2021	166,6
1/5/2021	166,92
2/5/2021	167,24
3/5/2021	167,56
4/5/2021	167,88
5/5/2021	168,2
6/5/2021	168,52
7/5/2021	168,84
8/5/2021	169,16
9/5/2021	169,48
10/5/2021	169,8
11/5/2021	170,12
12/5/2021	170,44
13/5/2021	170,76
14/5/2021	171,08
15/5/2021	171,4
16/5/2021	171,72
17/5/2021	172,04
18/5/2021	172,36
19/5/2021	172,68
20/5/2021	173
21/5/2021	173,32
22/5/2021	173,64
23/5/2021	173,96
24/5/2021	174,28
25/5/2021	174,6
26/5/2021	174,92
27/5/2021	175,24
28/5/2021	175,56
29/5/2021	175,88
30/5/2021	176,2
31/5/2021	176,52
1/6/2021	176,84
2/6/2021	177,16
3/6/2021	177,48
4/6/2021	177,8
5/6/2021	178,12
6/6/2021	178,44
7/6/2021	178,76
8/6/2021	179,08
9/6/2021	179,4
10/6/2021	179,72
11/6/2021	180,04
12/6/2021	180,36
13/6/2021	180,68
14/6/2021	181
15/6/2021	181,32
16/6/2021	181,64
17/6/2021	181,96
18/6/2021	182,28
19/6/2021	182,6
20/6/2021	182,92
21/6/2021	183,24
22/6/2021	182,92
23/6/2021	182,6
24/6/2021	182,28
25/6/2021	181,96
26/6/2021	181,64
27/6/2021	181,32
28/6/2021	181
29/6/2021	180,68
30/6/2021	180,36
1/7/2021	180,04
2/7/2021	179,72
3/7/2021	179,4
4/7/2021	179,08
5/7/2021	178,76
6/7/2021	178,44
7/7/2021	178,12
8/7/2021	177,8
9/7/2021	177,48
10/7/2021	177,16
11/7/2021	176,84
12/7/2021	176,52
13/7/2021	176,2
14/7/2021	175,88
15/7/2021	175,56
16/7/2021	175,24
17/7/2021	174,92
18/7/2021	174,6
19/7/2021	174,28
20/7/2021	173,96
21/7/2021	173,64
22/7/2021	173,32
23/7/2021	173
24/7/2021	172,68
25/7/2021	172,36
26/7/2021	172,04
27/7/2021	171,72
28/7/2021	171,4
29/7/2021	171,08
30/7/2021	170,76
31/7/2021	170,44
1/8/2021	170,12
2/8/2021	169,8
3/8/2021	169,48
4/8/2021	169,16
5/8/2021	168,84
6/8/2021	168,52
7/8/2021	168,2
8/8/2021	167,88
9/8/2021	167,56
10/8/2021	167,24
11/8/2021	166,92
12/8/2021	166,6
13/8/2021	166,28
14/8/2021	165,96
15/8/2021	165,64
16/8/2021	165,32
17/8/2021	165
18/8/2021	164,68
19/8/2021	164,36
20/8/2021	164,04
21/8/2021	163,72
22/8/2021	163,4
23/8/2021	163,08
24/8/2021	162,76
25/8/2021	162,44
26/8/2021	162,12
27/8/2021	161,8
28/8/2021	161,48
29/8/2021	161,16
30/8/2021	160,84
31/8/2021	160,52
1/9/2021	160,2
2/9/2021	159,88
3/9/2021	159,56
4/9/2021	159,24
5/9/2021	158,92
6/9/2021	158,6
7/9/2021	158,28
8/9/2021	157,96
9/9/2021	157,64
10/9/2021	157,32
11/9/2021	157
12/9/2021	156,68
13/9/2021	156,36
14/9/2021	156,04
15/9/2021	155,72
16/9/2021	155,4
17/9/2021	155,08
18/9/2021	154,76
19/9/2021	154,44
20/9/2021	154,12
21/9/2021	153,8
22/9/2021	153,48
23/9/2021	153,16
24/9/2021	152,84
25/9/2021	152,52
26/9/2021	152,2
27/9/2021	151,88
28/9/2021	151,56
29/9/2021	151,24
30/9/2021	150,92
1/10/2021	150,6
2/10/2021	150,28
3/10/2021	149,96
4/10/2021	149,64
5/10/2021	149,32
6/10/2021	149
7/10/2021	148,68
8/10/2021	148,36
9/10/2021	148,04
10/10/2021	147,72
11/10/2021	147,4
12/10/2021	147,08
13/10/2021	146,76
14/10/2021	146,44
15/10/2021	146,12
16/10/2021	145,8
17/10/2021	145,48
18/10/2021	145,16
19/10/2021	144,84
20/10/2021	144,52
21/10/2021	144,2
22/10/2021	143,88
23/10/2021	143,56
24/10/2021	143,24

Joerg · May 19, 2021, 10:36am

You are working with single values. If the sun beams through a window there is an azimuth range.

If you have a south window this range at October 31th is defined by sunrise and sunset, the range between the orange and the dark orange line which correspond to an azimuth range of 108° → ~ 250°