Observatoire Saint-Raymond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Saint-Raymond clear sky chart from 2005-11-06 to 2024-02-25.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	20% 10% 4 7% 6% 3 5% 5% 5% 6% 30%	78011
	Night	19% 11% 4 7% 6% 3 4 4 4 6% 30%	81273
Transparency	Day	56% 3 11% 20% 9% 1	77716
	Night	57% 2 10% 20% 10% 1	81103
Seeing	Day	28% 14% 28% 20% 8% 2	14058
	Night	27% 10% 26% 26% 9% 1	22865

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 17% 5% 10% 9% 3 5% 4 5% 5% 21%	2517
	11th to 20th	Day	11% 14% 7% 15% 10% 3 5% 4 4 4 24%	2520
	21st to end	Day	12% 13% 6% 9% 6% 3 4 5% 5% 7% 29%	2772
February	1st to 10th	Day	12% 15% 7% 11% 8% 4 6% 3 4 5% 25%	1531
	11th to 20th	Day	14% 16% 7% 11% 6% 4 5% 5% 4 5% 25%	1819
	21st to end	Day	14% 14% 7% 11% 7% 3 4 4 5% 6% 27%	1520
March	1st to 10th	Day	16% 12% 5% 7% 7% 4 5% 3 5% 4 31%	1797
	11th to 20th	Day	18% 13% 5% 6% 7% 4 4 5% 4 5% 31%	1867
	21st to end	Day	15% 11% 4 7% 7% 4 6% 5% 5% 5% 32%	2338
April	1st to 10th	Day	24% 10% 5% 7% 6% 4 5% 4 2 5% 28%	2160
	11th to 20th	Day	22% 7% 3 5% 6% 4 4 4 4 5% 37%	2200
	21st to end	Day	24% 10% 3 7% 6% 3 5% 4 3 6% 30%	2340
May	1st to 10th	Day	23% 8% 3 6% 5% 3 4 4 4 5% 34%	2423
	11th to 20th	Day	20% 7% 3 7% 6% 3 5% 5% 5% 6% 34%	2478
	21st to end	Day	22% 7% 3 6% 6% 4 4 5% 5% 6% 32%	2725
June	1st to 10th	Day	22% 7% 3 6% 6% 4 6% 5% 6% 8% 27%	2668
	11th to 20th	Day	21% 6% 3 6% 4 3 5% 4 6% 8% 33%	2700
	21st to end	Day	24% 8% 4 7% 6% 3 4 5% 5% 6% 26%	2677
July	1st to 10th	Day	17% 6% 3 6% 7% 4 6% 5% 7% 9% 31%	2520
	11th to 20th	Day	17% 7% 3 5% 5% 4 6% 6% 8% 10% 30%	2520
	21st to end	Day	18% 6% 2 6% 6% 5% 5% 7% 7% 9% 30%	2744
August	1st to 10th	Day	19% 7% 2 7% 6% 4 6% 6% 7% 10% 28%	2506
	11th to 20th	Day	18% 7% 3 5% 6% 4 5% 5% 6% 9% 33%	2317
	21st to end	Day	18% 6% 3 6% 4 3 5% 5% 6% 8% 35%	2440
September	1st to 10th	Day	21% 6% 2 5% 4 3 5% 5% 6% 7% 36%	2160
	11th to 20th	Day	20% 5% 2 4 4 3 4 4 5% 7% 43%	2020
	21st to end	Day	25% 6% 2 5% 4 2 3 4 4 7% 37%	1980
October	1st to 10th	Day	25% 8% 2 5% 5% 3 5% 5% 5% 6% 32%	1949
	11th to 20th	Day	27% 10% 3 8% 6% 4 5% 5% 5% 6% 23%	1666
	21st to end	Day	29% 10% 3 7% 7% 3 4 4 3 6% 24%	1782
November	1st to 10th	Day	21% 10% 4 8% 7% 3 3 3 4 5% 31%	1671
	11th to 20th	Day	24% 12% 4 8% 7% 4 4 4 4 4 25%	1682
	21st to end	Day	22% 17% 4 8% 6% 4 4 5% 5% 5% 21%	1411
December	1st to 10th	Day	26% 16% 4 7% 6% 2 4 4 4 4 22%	1330
	11th to 20th	Day	23% 13% 5% 8% 7% 3 3 3 3 4 27%	1668
	21st to end	Day	22% 19% 5% 7% 5% 2 3 4 4 4 24%	2593
January	1st to 10th	Night	17% 18% 6% 11% 7% 3 4 4 4 5% 21%	4429
	11th to 20th	Night	13% 16% 6% 12% 8% 4 4 4 4 5% 25%	4440
	21st to end	Night	11% 15% 5% 9% 8% 4 5% 5% 5% 6% 25%	4884
February	1st to 10th	Night	13% 14% 5% 10% 8% 4 5% 4 4 5% 28%	2646
	11th to 20th	Night	13% 15% 6% 10% 6% 4 5% 4 4 5% 26%	2247
	21st to end	Night	16% 13% 5% 9% 5% 4 5% 4 5% 5% 29%	1831
March	1st to 10th	Night	15% 12% 6% 9% 6% 3 5% 4 4 6% 30%	2150
	11th to 20th	Night	18% 13% 4 7% 6% 4 5% 5% 4 6% 28%	2091
	21st to end	Night	17% 11% 5% 7% 4 2 5% 4 5% 5% 36%	2016
April	1st to 10th	Night	23% 13% 4 6% 6% 3 4 4 5% 6% 27%	1800
	11th to 20th	Night	21% 7% 3 6% 5% 3 4 4 5% 7% 34%	1708
	21st to end	Night	22% 10% 3 5% 5% 3 4 5% 4 6% 33%	1620
May	1st to 10th	Night	25% 7% 3 6% 5% 3 5% 4 4 5% 33%	1552
	11th to 20th	Night	22% 6% 3 5% 5% 3 5% 3 4 6% 37%	1415
	21st to end	Night	23% 6% 2 6% 5% 3 3 3 5% 6% 38%	1550
June	1st to 10th	Night	22% 8% 3 6% 5% 3 5% 5% 7% 8% 29%	1288
	11th to 20th	Night	20% 6% 2 4 6% 3 4 4 5% 8% 36%	1260
	21st to end	Night	23% 6% 4 6% 7% 3 5% 4 5% 7% 31%	1277
July	1st to 10th	Night	17% 6% 2 6% 5% 2 4 6% 7% 8% 36%	1440
	11th to 20th	Night	17% 6% 3 6% 4 3 5% 6% 6% 8% 36%	1440
	21st to end	Night	17% 7% 3 4 6% 3 5% 5% 6% 7% 36%	1574
August	1st to 10th	Night	16% 5% 2 5% 4 2 6% 5% 7% 10% 38%	1432
	11th to 20th	Night	17% 5% 3 6% 6% 5% 5% 5% 5% 8% 35%	1566
	21st to end	Night	18% 5% 2 5% 5% 3 4 4 5% 7% 40%	1914
September	1st to 10th	Night	19% 6% 3 5% 5% 3 3 4 6% 6% 42%	1800
	11th to 20th	Night	19% 5% 2 5% 4 3 4 4 4 6% 43%	1939
	21st to end	Night	22% 6% 2 5% 4 2 4 4 4 6% 42%	1980
October	1st to 10th	Night	21% 7% 3 5% 5% 3 4 4 5% 6% 39%	2007
	11th to 20th	Night	26% 8% 3 6% 6% 3 5% 4 3 6% 30%	2293
	21st to end	Night	29% 9% 3 5% 5% 3 3 4 4 6% 27%	2574
November	1st to 10th	Night	20% 12% 4 6% 6% 3 4 4 4 6% 31%	2407
	11th to 20th	Night	22% 11% 3 6% 5% 4 4 4 4 6% 30%	2493
	21st to end	Night	25% 13% 4 7% 6% 3 4 4 4 5% 25%	2765
December	1st to 10th	Night	24% 16% 5% 8% 6% 4 5% 4 4 4 20%	2850
	11th to 20th	Night	22% 15% 6% 8% 6% 3 4 3 4 5% 24%	3531
	21st to end	Night	24% 19% 6% 8% 5% 2 3 3 3 3 24%	5064

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	67% 2 9% 16% 5% 1	2518
	11th to 20th	Day	66% 2 7% 18% 6% 1	2520
	21st to end	Day	55% 2 10% 23% 9% 1	2772
February	1st to 10th	Day	64% 2 8% 15% 9% 2	1531
	11th to 20th	Day	64% 2 10% 13% 10% 1	1828
	21st to end	Day	60% 2 7% 19% 9% 3	1520
March	1st to 10th	Day	58% 2 9% 17% 13% 2	1800
	11th to 20th	Day	57% 3 9% 16% 13% 2	1867
	21st to end	Day	55% 3 8% 18% 12% 3	2338
April	1st to 10th	Day	62% 2 9% 13% 10% 4	2160
	11th to 20th	Day	52% 2 9% 23% 12% 3	2200
	21st to end	Day	58% 2 8% 16% 13% 2	2340
May	1st to 10th	Day	53% 2 9% 18% 15% 3	2423
	11th to 20th	Day	51% 2 10% 21% 14% 2	2482
	21st to end	Day	53% 4 9% 18% 14% 1	2725
June	1st to 10th	Day	56% 3 11% 20% 8% 2	2668
	11th to 20th	Day	49% 3 13% 21% 12% 2	2700
	21st to end	Day	58% 3 12% 17% 9% 1	2677
July	1st to 10th	Day	49% 3 17% 24% 7%	2450
	11th to 20th	Day	48% 4 17% 24% 7%	2445
	21st to end	Day	52% 3 18% 20% 7%	2591
August	1st to 10th	Day	52% 4 20% 20% 4	2492
	11th to 20th	Day	48% 3 17% 24% 8%	2317
	21st to end	Day	47% 3 14% 26% 10%	2440
September	1st to 10th	Day	47% 3 15% 23% 11% 1	2160
	11th to 20th	Day	43% 2 17% 27% 11% 1	2020
	21st to end	Day	49% 2 14% 26% 9%	1980
October	1st to 10th	Day	54% 2 11% 23% 10%	1949
	11th to 20th	Day	62% 3 13% 19% 3	1666
	21st to end	Day	64% 2 10% 18% 5% 1	1782
November	1st to 10th	Day	57% 2 11% 20% 9%	1671
	11th to 20th	Day	64% 2 9% 17% 7% 1	1682
	21st to end	Day	65% 3 12% 15% 5% 1	1411
December	1st to 10th	Day	67% 2 9% 16% 6%	1330
	11th to 20th	Day	63% 2 5% 20% 8%	1668
	21st to end	Day	65% 2 9% 14% 8% 1	2593
January	1st to 10th	Night	67% 2 11% 13% 6%	4429
	11th to 20th	Night	65% 2 8% 21% 5% 1	4440
	21st to end	Night	60% 2 11% 17% 9%	4884
February	1st to 10th	Night	60% 2 7% 19% 10% 1	2646
	11th to 20th	Night	62% 2 9% 16% 10% 1	2249
	21st to end	Night	58% 2 7% 18% 14% 1	1831
March	1st to 10th	Night	58% 2 9% 16% 12% 2	2160
	11th to 20th	Night	58% 3 8% 14% 14% 3	2092
	21st to end	Night	51% 2 8% 21% 13% 4	2016
April	1st to 10th	Night	60% 1 8% 16% 12% 2	1800
	11th to 20th	Night	51% 2 8% 23% 14% 2	1708
	21st to end	Night	53% 3 8% 19% 15% 2	1620
May	1st to 10th	Night	54% 2 8% 18% 15% 3	1552
	11th to 20th	Night	50% 1 10% 20% 15% 3	1416
	21st to end	Night	49% 3 10% 20% 16% 2	1551
June	1st to 10th	Night	52% 3 11% 22% 10% 1	1288
	11th to 20th	Night	47% 4 11% 22% 13% 3	1260
	21st to end	Night	53% 3 13% 18% 12% 1	1277
July	1st to 10th	Night	44% 4 20% 23% 9%	1400
	11th to 20th	Night	45% 3 18% 25% 8% 1	1392
	21st to end	Night	47% 4 17% 23% 9%	1486
August	1st to 10th	Night	42% 5% 20% 27% 6%	1422
	11th to 20th	Night	49% 3 20% 20% 8% 1	1566
	21st to end	Night	45% 3 13% 31% 9%	1914
September	1st to 10th	Night	44% 3 14% 27% 12% 1	1800
	11th to 20th	Night	43% 2 17% 28% 9% 1	1939
	21st to end	Night	46% 3 11% 29% 12% 1	1980
October	1st to 10th	Night	48% 2 9% 27% 13% 1	2007
	11th to 20th	Night	58% 3 12% 21% 6%	2293
	21st to end	Night	59% 2 12% 19% 8%	2574
November	1st to 10th	Night	56% 3 11% 20% 9% 1	2407
	11th to 20th	Night	57% 3 11% 19% 10%	2493
	21st to end	Night	63% 2 9% 17% 8%	2765
December	1st to 10th	Night	69% 2 10% 14% 5%	2850
	11th to 20th	Night	65% 2 6% 18% 9%	3532
	21st to end	Night	68% 1 6% 16% 6% 1	5064

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	33% 14% 32% 18% 3	180
	11th to 20th	Day	32% 21% 24% 18% 5%	180
	21st to end	Day	18% 21% 38% 14% 8% 1	198
February	1st to 10th	Day	33% 19% 32% 12% 3	186
	11th to 20th	Day	27% 23% 31% 15% 4	427
	21st to end	Day	29% 23% 28% 16% 3 1	362
March	1st to 10th	Day	28% 20% 27% 18% 6%	420
	11th to 20th	Day	33% 19% 25% 17% 4 1	420
	21st to end	Day	28% 20% 26% 18% 8% 1	462
April	1st to 10th	Day	32% 16% 32% 15% 5% 1	420
	11th to 20th	Day	35% 14% 26% 17% 5% 2	412
	21st to end	Day	35% 15% 31% 12% 5% 2	420
May	1st to 10th	Day	31% 16% 32% 14% 6%	423
	11th to 20th	Day	27% 15% 30% 20% 8% 1	447
	21st to end	Day	24% 21% 32% 16% 7%	485
June	1st to 10th	Day	27% 12% 33% 22% 6% 1	598
	11th to 20th	Day	25% 12% 27% 23% 11% 1	630
	21st to end	Day	26% 9% 28% 23% 12% 2	607
July	1st to 10th	Day	22% 10% 32% 22% 11% 2	445
	11th to 20th	Day	22% 7% 34% 25% 10% 2	444
	21st to end	Day	21% 8% 31% 27% 10% 3	488
August	1st to 10th	Day	21% 6% 29% 30% 11% 3	446
	11th to 20th	Day	23% 5% 23% 30% 15% 3	439
	21st to end	Day	24% 13% 23% 19% 15% 6%	495
September	1st to 10th	Day	26% 9% 25% 24% 12% 4	450
	11th to 20th	Day	24% 9% 25% 24% 14% 5%	450
	21st to end	Day	27% 13% 22% 21% 13% 4	450
October	1st to 10th	Day	28% 13% 26% 20% 12% 2	450
	11th to 20th	Day	33% 11% 27% 19% 8% 2	383
	21st to end	Day	39% 10% 26% 18% 7% 1	396
November	1st to 10th	Day	36% 12% 22% 22% 8% 1	365
	11th to 20th	Day	33% 13% 28% 18% 8%	342
	21st to end	Day	36% 17% 29% 15% 3 1	180
December	1st to 10th	Day	37% 8% 32% 17% 6% 1	180
	11th to 20th	Day	32% 17% 29% 17% 3 2	180
	21st to end	Day	37% 17% 28% 12% 5% 1	198
January	1st to 10th	Night	30% 13% 30% 23% 4 1	760
	11th to 20th	Night	29% 17% 27% 20% 7%	760
	21st to end	Night	17% 14% 31% 30% 8% 1	836
February	1st to 10th	Night	19% 15% 34% 25% 6%	760
	11th to 20th	Night	23% 16% 35% 20% 6%	743
	21st to end	Night	27% 14% 28% 25% 5%	611
March	1st to 10th	Night	24% 13% 32% 25% 6%	720
	11th to 20th	Night	28% 15% 31% 19% 7% 1	720
	21st to end	Night	27% 13% 27% 24% 8% 1	792
April	1st to 10th	Night	33% 11% 27% 23% 6%	720
	11th to 20th	Night	27% 12% 27% 26% 7%	644
	21st to end	Night	31% 14% 27% 22% 6%	540
May	1st to 10th	Night	31% 11% 31% 20% 7%	472
	11th to 20th	Night	26% 8% 28% 29% 8% 1	354
	21st to end	Night	25% 9% 29% 27% 10%	389
June	1st to 10th	Night	27% 5% 28% 33% 8%	360
	11th to 20th	Night	25% 7% 20% 32% 14% 1	360
	21st to end	Night	25% 2 19% 39% 14% 1	360
July	1st to 10th	Night	21% 3 26% 37% 13% 1	350
	11th to 20th	Night	20% 3 19% 42% 15% 2	348
	21st to end	Night	19% 4 19% 39% 18% 1	394
August	1st to 10th	Night	19% 3 12% 43% 23%	358
	11th to 20th	Night	19% 3 20% 38% 19%	502
	21st to end	Night	21% 7% 22% 32% 17% 1	726
September	1st to 10th	Night	21% 4 25% 33% 15% 1	720
	11th to 20th	Night	24% 6% 20% 32% 17% 2	720
	21st to end	Night	26% 6% 23% 29% 14% 2	720
October	1st to 10th	Night	25% 9% 24% 31% 11%	720
	11th to 20th	Night	31% 9% 23% 26% 10% 1	720
	21st to end	Night	35% 9% 28% 23% 4 1	792
November	1st to 10th	Night	30% 10% 26% 25% 8% 1	740
	11th to 20th	Night	31% 13% 25% 22% 9% 1	760
	21st to end	Night	34% 14% 23% 21% 7% 1	810
December	1st to 10th	Night	35% 12% 24% 21% 8%	850
	11th to 20th	Night	31% 15% 26% 21% 7% 1	850
	21st to end	Night	37% 13% 27% 18% 4	884

Page generated at 2024-02-22 06:05:46. Version ac07

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