Rigaud
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rigaud clear sky chart from 2005-11-06 to 2026-03-18.

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	16% 10% 4 8% 5% 5% 5% 4 5% 7% 31%	131277
	Night	17% 11% 4 9% 5% 5% 4 4 5% 6% 30%	130230
Transparency	Day	50% 6% 12% 20% 10% 1	134721
	Night	54% 6% 12% 19% 10% 1	134873
Seeing	Day	21% 14% 30% 22% 10% 3	16164
	Night	22% 12% 29% 27% 10% 1	25298

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	15% 18% 5% 14% 5% 4 4 4 4 5% 21%	4661
	11th to 20th	Day	13% 16% 6% 13% 6% 5% 5% 3 5% 5% 21%	4650
	21st to end	Day	9% 15% 6% 13% 9% 7% 6% 4 5% 5% 22%	5124
February	1st to 10th	Day	13% 15% 4 11% 6% 5% 5% 3 5% 6% 25%	1878
	11th to 20th	Day	14% 13% 4 11% 7% 6% 5% 3 5% 6% 26%	1925
	21st to end	Day	18% 15% 5% 9% 6% 5% 4 3 5% 5% 25%	1730
March	1st to 10th	Day	18% 13% 6% 12% 6% 4 4 3 4 5% 25%	4576
	11th to 20th	Day	11% 14% 4 10% 6% 4 4 4 6% 6% 30%	4840
	21st to end	Day	19% 9% 4 9% 5% 5% 4 3 4 4 34%	5919
April	1st to 10th	Day	21% 11% 3 7% 5% 4 4 3 5% 5% 33%	2400
	11th to 20th	Day	21% 9% 3 7% 5% 4 4 3 5% 5% 35%	2374
	21st to end	Day	22% 9% 3 7% 5% 4 4 4 5% 5% 32%	2533
May	1st to 10th	Day	25% 10% 3 10% 5% 5% 5% 4 5% 6% 22%	6339
	11th to 20th	Day	18% 10% 3 8% 6% 5% 4 4 5% 7% 30%	6318
	21st to end	Day	21% 9% 3 7% 5% 4 4 4 6% 6% 31%	6949
June	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 7% 30%	2800
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 8% 38%	2800
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 7% 7% 31%	2800
July	1st to 10th	Day	13% 6% 3 8% 6% 5% 6% 5% 7% 8% 33%	6360
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 9% 41%	6360
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 46%	6926
August	1st to 10th	Day	14% 6% 2 8% 5% 5% 6% 4 7% 8% 35%	4563
	11th to 20th	Day	13% 7% 4 7% 4 4 4 3 6% 8% 39%	4110
	21st to end	Day	15% 4 2 5% 5% 4 5% 4 7% 9% 39%	4312
September	1st to 10th	Day	11% 6% 3 5% 4 4 5% 4 6% 8% 42%	2400
	11th to 20th	Day	12% 5% 2 5% 3 4 4 4 5% 7% 50%	2338
	21st to end	Day	16% 6% 3 6% 4 4 4 3 6% 8% 41%	2200
October	1st to 10th	Day	19% 7% 3 7% 4 4 4 3 4 7% 39%	2030
	11th to 20th	Day	18% 9% 3 8% 6% 5% 5% 3 5% 5% 31%	1983
	21st to end	Day	24% 11% 3 7% 4 3 4 3 6% 6% 29%	1980
November	1st to 10th	Day	16% 11% 3 7% 5% 5% 5% 4 6% 6% 32%	1851
	11th to 20th	Day	17% 11% 4 8% 5% 5% 5% 4 6% 7% 29%	1774
	21st to end	Day	22% 12% 4 8% 6% 5% 6% 4 5% 5% 22%	1680
December	1st to 10th	Day	20% 21% 5% 9% 5% 4 5% 4 6% 5% 17%	2680
	11th to 20th	Day	19% 14% 5% 11% 5% 5% 5% 3 4 4 26%	3066
	21st to end	Day	23% 15% 4 10% 5% 4 5% 3 4 4 23%	4048
January	1st to 10th	Night	14% 19% 8% 13% 5% 4 4 3 4 5% 20%	8234
	11th to 20th	Night	12% 17% 7% 18% 8% 5% 4 3 5% 4 16%	8235
	21st to end	Night	11% 15% 5% 12% 8% 6% 5% 3 5% 6% 25%	9057
February	1st to 10th	Night	14% 13% 5% 12% 6% 5% 5% 4 6% 6% 24%	2740
	11th to 20th	Night	13% 12% 4 11% 6% 5% 5% 5% 6% 5% 28%	2579
	21st to end	Night	14% 15% 5% 10% 5% 5% 4 4 4 5% 30%	2076
March	1st to 10th	Night	21% 13% 3 8% 5% 4 4 4 4 4 29%	5484
	11th to 20th	Night	15% 14% 4 8% 5% 5% 5% 4 6% 7% 29%	5257
	21st to end	Night	16% 11% 3 9% 5% 6% 5% 3 4 5% 32%	5013
April	1st to 10th	Night	22% 10% 3 7% 4 5% 5% 3 4 6% 31%	2000
	11th to 20th	Night	21% 9% 3 7% 5% 3 5% 3 5% 5% 33%	1975
	21st to end	Night	22% 9% 2 7% 5% 5% 4 3 5% 6% 34%	1865
May	1st to 10th	Night	24% 10% 3 8% 5% 5% 5% 4 5% 6% 24%	3644
	11th to 20th	Night	21% 8% 3 7% 4 4 4 3 5% 7% 33%	3575
	21st to end	Night	18% 10% 4 9% 5% 5% 4 3 5% 7% 30%	3926
June	1st to 10th	Night	20% 7% 3 6% 4 5% 5% 5% 7% 8% 30%	1600
	11th to 20th	Night	15% 8% 2 7% 4 4 4 4 5% 8% 40%	1600
	21st to end	Night	18% 7% 2 6% 4 5% 5% 5% 6% 8% 35%	1600
July	1st to 10th	Night	14% 5% 3 7% 6% 5% 6% 5% 8% 9% 33%	3600
	11th to 20th	Night	15% 6% 2 7% 5% 4 4 3 6% 8% 42%	3600
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 46%	3926
August	1st to 10th	Night	14% 7% 3 7% 4 4 4 4 6% 7% 39%	2586
	11th to 20th	Night	15% 7% 3 6% 4 4 4 4 5% 6% 40%	2902
	21st to end	Night	16% 5% 2 7% 5% 4 5% 4 6% 7% 40%	3586
September	1st to 10th	Night	11% 6% 3 7% 4 4 4 4 6% 7% 44%	2000
	11th to 20th	Night	14% 6% 3 4 3 3 3 3 4 7% 50%	2060
	21st to end	Night	17% 6% 1 6% 4 4 3 3 5% 7% 44%	2200
October	1st to 10th	Night	18% 6% 2 6% 4 4 4 3 5% 7% 39%	2367
	11th to 20th	Night	19% 8% 3 8% 5% 5% 5% 3 5% 6% 35%	2415
	21st to end	Night	21% 8% 3 8% 5% 5% 4 3 5% 6% 30%	2860
November	1st to 10th	Night	20% 10% 3 7% 5% 4 5% 4 5% 7% 32%	2667
	11th to 20th	Night	18% 9% 4 8% 5% 5% 5% 4 5% 6% 32%	2843
	21st to end	Night	22% 12% 5% 10% 6% 4 4 3 5% 6% 24%	2940
December	1st to 10th	Night	18% 17% 6% 11% 6% 5% 5% 4 5% 5% 18%	4720
	11th to 20th	Night	23% 14% 5% 10% 5% 4 4 3 4 5% 23%	5348
	21st to end	Night	25% 17% 4 9% 4 3 3 3 5% 5% 23%	7150

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	63% 7% 10% 16% 4	4662
	11th to 20th	Day	62% 6% 9% 13% 9% 1	4680
	21st to end	Day	62% 6% 11% 11% 10% 1	5124
February	1st to 10th	Day	59% 4 10% 20% 6% 2	1878
	11th to 20th	Day	58% 5% 11% 17% 8% 1	1934
	21st to end	Day	61% 3 10% 14% 10% 1	1730
March	1st to 10th	Day	61% 5% 8% 13% 10% 3	4579
	11th to 20th	Day	51% 7% 16% 15% 10% 2	4840
	21st to end	Day	52% 4 7% 16% 18% 2	5919
April	1st to 10th	Day	53% 4 8% 20% 13% 2	2400
	11th to 20th	Day	49% 5% 7% 21% 15% 2	2374
	21st to end	Day	53% 5% 8% 17% 13% 3	2533
May	1st to 10th	Day	60% 6% 8% 17% 7% 1	6350
	11th to 20th	Day	52% 8% 13% 17% 9% 2	6322
	21st to end	Day	50% 7% 11% 19% 12% 1	6949
June	1st to 10th	Day	51% 7% 10% 18% 13% 1	2800
	11th to 20th	Day	41% 8% 12% 23% 14% 3	2800
	21st to end	Day	50% 8% 12% 19% 10% 1	2800
July	1st to 10th	Day	45% 8% 13% 25% 9%	6290
	11th to 20th	Day	38% 7% 13% 30% 12%	6285
	21st to end	Day	33% 7% 16% 36% 9%	6728
August	1st to 10th	Day	44% 7% 17% 23% 9%	4549
	11th to 20th	Day	41% 7% 16% 29% 6%	4152
	21st to end	Day	40% 7% 17% 22% 13% 1	4312
September	1st to 10th	Day	37% 7% 15% 29% 12%	2400
	11th to 20th	Day	33% 6% 14% 31% 15% 1	2338
	21st to end	Day	41% 6% 15% 26% 12% 1	2200
October	1st to 10th	Day	44% 6% 13% 27% 10%	3303
	11th to 20th	Day	44% 5% 17% 26% 7%	3211
	21st to end	Day	45% 6% 20% 21% 8%	3180
November	1st to 10th	Day	50% 6% 15% 21% 8% 1	1851
	11th to 20th	Day	54% 6% 12% 17% 10% 1	1774
	21st to end	Day	61% 7% 13% 13% 5%	1680
December	1st to 10th	Day	68% 6% 10% 14% 3	2680
	11th to 20th	Day	62% 4 9% 16% 8%	3066
	21st to end	Day	65% 4 10% 15% 6%	4048
January	1st to 10th	Night	66% 5% 11% 13% 5%	8234
	11th to 20th	Night	69% 6% 9% 10% 5%	8280
	21st to end	Night	60% 5% 9% 14% 12%	9057
February	1st to 10th	Night	59% 4 11% 17% 7% 1	2740
	11th to 20th	Night	55% 6% 11% 21% 7% 1	2581
	21st to end	Night	56% 4 9% 17% 12% 1	2076
March	1st to 10th	Night	57% 4 9% 15% 12% 4	5494
	11th to 20th	Night	52% 6% 13% 15% 10% 3	5258
	21st to end	Night	53% 5% 6% 21% 12% 2	5013
April	1st to 10th	Night	54% 3 8% 19% 14% 2	2000
	11th to 20th	Night	51% 5% 8% 20% 14% 2	1975
	21st to end	Night	51% 5% 8% 19% 14% 4	1865
May	1st to 10th	Night	59% 6% 9% 17% 7% 2	3650
	11th to 20th	Night	49% 6% 12% 19% 11% 2	3576
	21st to end	Night	52% 6% 9% 17% 14% 1	3927
June	1st to 10th	Night	49% 7% 12% 19% 12% 1	1600
	11th to 20th	Night	42% 6% 12% 22% 16% 2	1600
	21st to end	Night	46% 8% 12% 20% 14% 1	1600
July	1st to 10th	Night	44% 8% 17% 20% 10%	3560
	11th to 20th	Night	39% 7% 15% 29% 10%	3552
	21st to end	Night	35% 6% 16% 29% 14%	3809
August	1st to 10th	Night	42% 6% 15% 27% 9%	2576
	11th to 20th	Night	43% 6% 17% 26% 8%	2926
	21st to end	Night	41% 8% 16% 21% 13% 1	3586
September	1st to 10th	Night	37% 6% 13% 27% 16% 1	2000
	11th to 20th	Night	34% 5% 13% 34% 12% 1	2060
	21st to end	Night	41% 5% 13% 27% 14%	2200
October	1st to 10th	Night	41% 7% 15% 26% 11% 1	3874
	11th to 20th	Night	44% 6% 14% 27% 8%	3926
	21st to end	Night	46% 5% 18% 19% 11% 1	4610
November	1st to 10th	Night	51% 6% 13% 21% 8% 1	2667
	11th to 20th	Night	54% 5% 13% 18% 9% 1	2843
	21st to end	Night	60% 5% 13% 16% 5%	2940
December	1st to 10th	Night	67% 5% 12% 12% 4	4720
	11th to 20th	Night	64% 4 7% 16% 9%	5348
	21st to end	Night	64% 4 8% 14% 10%	7150

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	26% 17% 30% 21% 6%	220
	11th to 20th	Day	29% 21% 33% 12% 5%	220
	21st to end	Day	20% 17% 36% 21% 6%	242
February	1st to 10th	Day	27% 22% 33% 14% 3	325
	11th to 20th	Day	23% 21% 39% 16% 1	412
	21st to end	Day	29% 17% 32% 20% 2	446
March	1st to 10th	Day	24% 19% 33% 20% 4	540
	11th to 20th	Day	23% 21% 34% 17% 4 1	528
	21st to end	Day	27% 18% 29% 17% 8% 2	550
April	1st to 10th	Day	28% 18% 29% 18% 6% 2	500
	11th to 20th	Day	26% 20% 28% 15% 9% 2	492
	21st to end	Day	28% 18% 31% 15% 7% 2	500
May	1st to 10th	Day	23% 14% 32% 22% 7% 2	503
	11th to 20th	Day	19% 14% 31% 24% 10% 2	527
	21st to end	Day	20% 15% 30% 23% 10% 2	573
June	1st to 10th	Day	19% 16% 27% 27% 9% 2	530
	11th to 20th	Day	16% 13% 32% 25% 13% 2	530
	21st to end	Day	21% 12% 32% 23% 10% 3	530
July	1st to 10th	Day	12% 10% 30% 29% 14% 4	525
	11th to 20th	Day	14% 9% 31% 29% 15% 2	524
	21st to end	Day	14% 8% 29% 30% 16% 3	576
August	1st to 10th	Day	15% 6% 25% 31% 18% 4	526
	11th to 20th	Day	11% 8% 24% 31% 18% 8%	519
	21st to end	Day	14% 9% 26% 26% 18% 6%	583
September	1st to 10th	Day	15% 8% 30% 23% 18% 6%	530
	11th to 20th	Day	11% 8% 22% 26% 20% 13%	530
	21st to end	Day	19% 12% 28% 20% 16% 5%	530
October	1st to 10th	Day	22% 10% 28% 22% 15% 4	530
	11th to 20th	Day	21% 19% 28% 21% 10% 1	520
	21st to end	Day	29% 13% 29% 21% 7%	462
November	1st to 10th	Day	29% 16% 26% 20% 8% 1	425
	11th to 20th	Day	24% 20% 32% 19% 4	314
	21st to end	Day	29% 20% 29% 16% 5%	220
December	1st to 10th	Day	31% 15% 27% 20% 6% 2	220
	11th to 20th	Day	30% 18% 35% 13% 4	220
	21st to end	Day	32% 16% 32% 14% 4 2	242
January	1st to 10th	Night	24% 16% 32% 24% 3	840
	11th to 20th	Night	28% 17% 28% 22% 5% 1	840
	21st to end	Night	19% 13% 36% 25% 7% 1	924
February	1st to 10th	Night	20% 14% 35% 26% 5%	840
	11th to 20th	Night	20% 16% 37% 22% 4	823
	21st to end	Night	22% 14% 33% 27% 3	692
March	1st to 10th	Night	24% 15% 33% 24% 4	840
	11th to 20th	Night	26% 15% 31% 23% 5%	829
	21st to end	Night	23% 13% 30% 26% 7% 1	880
April	1st to 10th	Night	27% 14% 27% 26% 5%	800
	11th to 20th	Night	24% 15% 31% 25% 5% 1	791
	21st to end	Night	27% 10% 31% 23% 8%	665
May	1st to 10th	Night	25% 8% 30% 25% 8% 3	424
	11th to 20th	Night	21% 8% 29% 31% 10% 1	394
	21st to end	Night	17% 8% 34% 31% 10%	433
June	1st to 10th	Night	22% 8% 27% 32% 11% 1	400
	11th to 20th	Night	18% 7% 27% 35% 12% 1	400
	21st to end	Night	20% 6% 27% 31% 15% 1	400
July	1st to 10th	Night	12% 6% 28% 35% 18% 1	390
	11th to 20th	Night	14% 4 23% 40% 19%	388
	21st to end	Night	13% 4 25% 40% 18% 1	438
August	1st to 10th	Night	14% 3 18% 43% 20% 1	398
	11th to 20th	Night	14% 3 22% 33% 24% 3	605
	21st to end	Night	14% 5% 25% 34% 19% 2	880
September	1st to 10th	Night	13% 5% 26% 37% 17% 1	800
	11th to 20th	Night	17% 6% 17% 35% 24% 3	800
	21st to end	Night	19% 8% 25% 28% 19% 2	800
October	1st to 10th	Night	22% 10% 25% 29% 14% 1	800
	11th to 20th	Night	23% 12% 28% 28% 9% 1	800
	21st to end	Night	27% 11% 30% 26% 5%	880
November	1st to 10th	Night	26% 15% 24% 27% 7%	820
	11th to 20th	Night	22% 18% 30% 21% 8%	840
	21st to end	Night	29% 16% 29% 19% 6%	840
December	1st to 10th	Night	29% 14% 31% 22% 4	840
	11th to 20th	Night	29% 18% 31% 16% 5% 1	840
	21st to end	Night	35% 15% 28% 16% 6%	924

Page generated at 2026-03-15 02:23:58. Version ac07

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