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 2024-10-25.

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	19% 10% 3 8% 5% 5% 4 4 5% 6% 30%	101246
	Night	19% 12% 4 8% 5% 4 4 3 5% 6% 30%	97569
Transparency	Day	55% 3 12% 20% 9% 1	101004
	Night	57% 3 11% 20% 9% 1	97432
Seeing	Day	28% 14% 28% 20% 8% 2	15048
	Night	27% 10% 26% 26% 9% 1	23612

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% 12% 7% 4 5% 3 4 5% 21%	2517
	11th to 20th	Day	11% 15% 7% 17% 7% 5% 4 3 4 4 24%	2520
	21st to end	Day	11% 14% 5% 10% 5% 4 5% 4 5% 7% 29%	2772
February	1st to 10th	Day	12% 17% 6% 12% 7% 6% 5% 2 4 4 25%	1531
	11th to 20th	Day	13% 17% 6% 12% 6% 5% 4 4 4 5% 24%	1819
	21st to end	Day	14% 15% 6% 12% 6% 4 4 3 5% 6% 26%	1570
March	1st to 10th	Day	22% 12% 4 8% 6% 5% 4 3 4 4 29%	3116
	11th to 20th	Day	16% 20% 5% 8% 6% 4 3 3 4 5% 26%	3283
	21st to end	Day	16% 14% 4 7% 5% 4 5% 3 4 4 36%	4100
April	1st to 10th	Day	23% 12% 4 8% 5% 5% 4 3 2 5% 29%	2280
	11th to 20th	Day	22% 8% 3 6% 5% 5% 4 3 4 5% 36%	2324
	21st to end	Day	24% 10% 3 7% 5% 4 4 3 3 6% 30%	2470
May	1st to 10th	Day	22% 8% 3 7% 4 4 4 3 5% 6% 35%	4259
	11th to 20th	Day	18% 7% 3 7% 5% 4 5% 4 7% 8% 33%	4398
	21st to end	Day	19% 7% 3 8% 5% 5% 5% 4 5% 7% 31%	4837
June	1st to 10th	Day	21% 8% 2 7% 5% 6% 6% 4 6% 8% 27%	2817
	11th to 20th	Day	20% 7% 2 6% 4 4 5% 4 6% 8% 34%	2850
	21st to end	Day	25% 9% 3 8% 5% 5% 4 4 5% 6% 26%	2825
July	1st to 10th	Day	17% 7% 3 8% 6% 5% 6% 4 6% 8% 30%	4440
	11th to 20th	Day	19% 7% 2 7% 5% 5% 6% 5% 7% 9% 29%	4440
	21st to end	Day	16% 6% 2 6% 4 5% 5% 5% 6% 8% 39%	4814
August	1st to 10th	Day	17% 7% 2 7% 5% 6% 6% 5% 7% 9% 29%	4423
	11th to 20th	Day	21% 7% 3 6% 5% 5% 5% 4 6% 9% 28%	4058
	21st to end	Day	23% 7% 2 7% 3 4 4 3 5% 7% 35%	4286
September	1st to 10th	Day	20% 6% 2 6% 3 4 5% 4 6% 7% 37%	2280
	11th to 20th	Day	19% 5% 2 5% 3 4 4 3 5% 6% 44%	2132
	21st to end	Day	24% 7% 2 6% 4 3 3 3 5% 6% 37%	2090
October	1st to 10th	Day	24% 9% 2 5% 4 5% 5% 4 5% 6% 31%	2057
	11th to 20th	Day	26% 10% 3 9% 5% 4 4 5% 5% 6% 23%	1758
	21st to end	Day	28% 10% 3 7% 5% 4 3 3 4 6% 25%	1825
November	1st to 10th	Day	21% 11% 3 8% 6% 4 3 3 4 5% 31%	1671
	11th to 20th	Day	23% 13% 4 9% 6% 5% 4 3 4 4 25%	1682
	21st to end	Day	21% 17% 4 8% 6% 5% 4 4 5% 5% 21%	1411
December	1st to 10th	Day	25% 18% 3 9% 5% 3 4 3 4 4 22%	1330
	11th to 20th	Day	23% 14% 5% 10% 5% 4 3 2 3 4 27%	1668
	21st to end	Day	22% 20% 4 8% 4 3 4 3 4 4 24%	2593
January	1st to 10th	Night	16% 19% 6% 13% 5% 4 3 3 4 5% 21%	4429
	11th to 20th	Night	13% 16% 5% 14% 6% 5% 4 3 4 5% 25%	4440
	21st to end	Night	11% 15% 5% 11% 6% 6% 5% 4 6% 6% 25%	4884
February	1st to 10th	Night	12% 15% 5% 11% 7% 5% 4 3 4 4 28%	2646
	11th to 20th	Night	13% 16% 5% 12% 5% 6% 4 4 5% 5% 26%	2247
	21st to end	Night	16% 14% 5% 9% 5% 5% 5% 3 5% 5% 29%	1884
March	1st to 10th	Night	24% 12% 4 8% 4 4 6% 3 4 5% 27%	3724
	11th to 20th	Night	17% 19% 4 9% 6% 5% 4 3 4 5% 23%	3675
	21st to end	Night	17% 13% 5% 8% 4 4 4 3 4 5% 33%	3530
April	1st to 10th	Night	22% 14% 3 7% 4 4 3 3 5% 5% 29%	1900
	11th to 20th	Night	22% 8% 2 6% 5% 4 4 3 5% 6% 33%	1804
	21st to end	Night	22% 10% 3 6% 4 3 5% 3 5% 6% 34%	1710
May	1st to 10th	Night	24% 7% 2 6% 5% 4 4 3 5% 6% 33%	2710
	11th to 20th	Night	22% 7% 2 6% 3 4 3 3 5% 7% 37%	2495
	21st to end	Night	19% 6% 3 6% 5% 5% 5% 3 6% 8% 35%	2738
June	1st to 10th	Night	22% 8% 2 6% 5% 5% 5% 4 7% 7% 29%	1359
	11th to 20th	Night	20% 7% 2 5% 5% 4 4 3 5% 8% 36%	1330
	21st to end	Night	23% 7% 3 6% 6% 4 4 3 5% 6% 31%	1348
July	1st to 10th	Night	16% 6% 2 8% 6% 5% 5% 5% 7% 7% 32%	2520
	11th to 20th	Night	20% 7% 3 6% 5% 3 4 4 5% 8% 35%	2520
	21st to end	Night	14% 5% 2 5% 5% 4 4 3 6% 7% 44%	2739
August	1st to 10th	Night	18% 7% 3 8% 4 4 5% 3 6% 8% 35%	2506
	11th to 20th	Night	21% 6% 2 7% 5% 6% 5% 4 5% 7% 32%	2739
	21st to end	Night	19% 8% 3 9% 5% 5% 4 3 5% 6% 34%	3368
September	1st to 10th	Night	19% 6% 2 6% 4 3 3 4 6% 5% 42%	1900
	11th to 20th	Night	18% 5% 2 6% 4 4 4 3 4 6% 45%	2047
	21st to end	Night	22% 7% 2 6% 3 3 4 3 4 6% 41%	2090
October	1st to 10th	Night	21% 8% 2 6% 4 4 4 3 5% 6% 38%	2119
	11th to 20th	Night	25% 9% 3 7% 4 4 5% 3 3 5% 31%	2421
	21st to end	Night	28% 10% 2 6% 4 4 4 3 5% 7% 28%	2637
November	1st to 10th	Night	20% 12% 3 8% 5% 4 4 3 4 6% 31%	2407
	11th to 20th	Night	22% 12% 3 7% 5% 4 4 3 4 6% 30%	2493
	21st to end	Night	24% 14% 4 8% 5% 4 4 3 4 5% 25%	2765
December	1st to 10th	Night	24% 18% 4 9% 6% 5% 4 3 3 4 20%	2850
	11th to 20th	Night	21% 16% 5% 9% 5% 4 4 2 4 5% 24%	3531
	21st to end	Night	24% 19% 6% 9% 4 3 3 2 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	61% 2 8% 18% 9% 3	1570
March	1st to 10th	Day	61% 1 10% 17% 9% 2	3119
	11th to 20th	Day	64% 2 8% 17% 8% 1	3283
	21st to end	Day	54% 2 7% 19% 14% 5%	4100
April	1st to 10th	Day	61% 2 9% 14% 10% 4	2280
	11th to 20th	Day	52% 2 9% 23% 12% 3	2324
	21st to end	Day	58% 2 8% 17% 13% 2	2470
May	1st to 10th	Day	52% 1 11% 18% 16% 2	4273
	11th to 20th	Day	50% 2 17% 22% 8% 1	4402
	21st to end	Day	53% 2 8% 20% 16% 1	4837
June	1st to 10th	Day	56% 3 11% 21% 8% 2	2817
	11th to 20th	Day	48% 3 14% 21% 12% 2	2850
	21st to end	Day	58% 4 11% 17% 9% 1	2825
July	1st to 10th	Day	51% 4 15% 22% 8%	4370
	11th to 20th	Day	49% 6% 20% 20% 4	4365
	21st to end	Day	44% 4 20% 25% 7%	4661
August	1st to 10th	Day	49% 6% 19% 20% 5%	4409
	11th to 20th	Day	52% 5% 19% 19% 5%	4097
	21st to end	Day	49% 4 14% 18% 14%	4286
September	1st to 10th	Day	46% 3 15% 24% 11% 1	2280
	11th to 20th	Day	42% 2 17% 28% 11% 1	2132
	21st to end	Day	50% 2 14% 26% 9%	2090
October	1st to 10th	Day	54% 2 11% 23% 9%	2057
	11th to 20th	Day	61% 3 14% 19% 3	1758
	21st to end	Day	62% 3 11% 18% 5% 1	1825
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% 13% 2	1884
March	1st to 10th	Night	62% 2 11% 14% 8% 2	3734
	11th to 20th	Night	65% 2 6% 16% 9% 1	3676
	21st to end	Night	56% 1 7% 22% 11% 3	3530
April	1st to 10th	Night	58% 1 8% 16% 14% 2	1900
	11th to 20th	Night	52% 2 7% 22% 14% 2	1804
	21st to end	Night	52% 3 8% 19% 15% 2	1710
May	1st to 10th	Night	54% 1 9% 22% 11% 2	2716
	11th to 20th	Night	49% 1 15% 22% 12% 1	2496
	21st to end	Night	49% 2 11% 20% 17% 1	2739
June	1st to 10th	Night	52% 3 11% 23% 10% 1	1359
	11th to 20th	Night	47% 4 12% 22% 13% 3	1330
	21st to end	Night	55% 3 12% 18% 12% 1	1348
July	1st to 10th	Night	48% 5% 19% 21% 7%	2480
	11th to 20th	Night	48% 4 21% 22% 5%	2472
	21st to end	Night	38% 5% 22% 26% 8%	2651
August	1st to 10th	Night	48% 5% 17% 23% 8%	2496
	11th to 20th	Night	51% 6% 20% 17% 6%	2766
	21st to end	Night	51% 4 11% 22% 11%	3368
September	1st to 10th	Night	43% 3 13% 27% 12% 1	1900
	11th to 20th	Night	42% 2 17% 29% 9% 1	2047
	21st to end	Night	46% 3 11% 28% 11%	2090
October	1st to 10th	Night	48% 3 10% 26% 13% 1	2119
	11th to 20th	Night	57% 3 13% 22% 6%	2421
	21st to end	Night	58% 2 13% 19% 8%	2637
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	382
March	1st to 10th	Day	29% 19% 27% 18% 6%	460
	11th to 20th	Day	32% 19% 27% 17% 4 1	460
	21st to end	Day	29% 21% 26% 17% 7% 1	506
April	1st to 10th	Day	32% 16% 32% 14% 5% 1	460
	11th to 20th	Day	36% 13% 27% 16% 5% 2	452
	21st to end	Day	35% 16% 31% 12% 5% 2	460
May	1st to 10th	Day	32% 16% 32% 14% 6%	463
	11th to 20th	Day	26% 14% 30% 22% 8% 1	487
	21st to end	Day	24% 21% 32% 16% 7%	529
June	1st to 10th	Day	26% 11% 32% 23% 7% 1	647
	11th to 20th	Day	24% 13% 28% 23% 11% 1	680
	21st to end	Day	27% 10% 28% 22% 11% 2	655
July	1st to 10th	Day	22% 12% 33% 21% 11% 1	485
	11th to 20th	Day	21% 8% 35% 24% 10% 2	484
	21st to end	Day	21% 8% 31% 27% 10% 3	532
August	1st to 10th	Day	20% 7% 29% 29% 11% 3	486
	11th to 20th	Day	24% 6% 22% 30% 15% 3	479
	21st to end	Day	23% 13% 24% 20% 15% 6%	539
September	1st to 10th	Day	25% 9% 26% 24% 12% 4	490
	11th to 20th	Day	22% 9% 24% 26% 15% 5%	490
	21st to end	Day	26% 13% 23% 21% 13% 4	490
October	1st to 10th	Day	27% 14% 25% 21% 12% 2	490
	11th to 20th	Day	32% 12% 27% 19% 8% 2	415
	21st to end	Day	38% 10% 27% 19% 6%	411
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%	628
March	1st to 10th	Night	25% 12% 32% 25% 6%	760
	11th to 20th	Night	28% 15% 31% 19% 6% 1	760
	21st to end	Night	27% 13% 28% 23% 7% 1	836
April	1st to 10th	Night	32% 11% 27% 23% 6%	760
	11th to 20th	Night	29% 12% 28% 25% 6%	680
	21st to end	Night	31% 14% 28% 21% 6%	570
May	1st to 10th	Night	31% 10% 32% 19% 6%	498
	11th to 20th	Night	26% 8% 28% 29% 8% 1	374
	21st to end	Night	25% 8% 30% 27% 9%	411
June	1st to 10th	Night	27% 5% 28% 33% 8% 1	380
	11th to 20th	Night	24% 7% 22% 32% 15% 1	380
	21st to end	Night	26% 2 20% 38% 13% 1	380
July	1st to 10th	Night	21% 2 25% 37% 14% 1	370
	11th to 20th	Night	20% 3 19% 42% 15% 2	368
	21st to end	Night	18% 4 20% 40% 18% 1	416
August	1st to 10th	Night	18% 3 12% 44% 22%	378
	11th to 20th	Night	19% 3 20% 38% 19%	531
	21st to end	Night	21% 7% 21% 32% 18% 1	767
September	1st to 10th	Night	22% 5% 24% 34% 14% 1	760
	11th to 20th	Night	23% 5% 19% 32% 19% 2	760
	21st to end	Night	25% 6% 23% 30% 14% 1	760
October	1st to 10th	Night	25% 8% 24% 31% 11%	760
	11th to 20th	Night	31% 9% 23% 27% 9% 1	760
	21st to end	Night	34% 9% 27% 24% 5% 1	812
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 2024-10-22 20:21:06. Version ac07

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