Ruisseau d'or
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ruisseau d'or clear sky chart from 2005-11-06 to 2026-05-17.

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% 13% 5% 11% 6% 5% 5% 4 5% 6% 25%	131144
	Night	15% 14% 5% 12% 7% 5% 5% 3 4 5% 24%	131655
Transparency	Day	56% 7% 11% 17% 8% 1	134612
	Night	58% 7% 11% 15% 7% 1	136275
Seeing	Day	27% 21% 28% 15% 6% 2	17138
	Night	24% 19% 26% 22% 8% 1	25840

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	11% 16% 9% 19% 9% 8% 7% 3 4 4 11%	4661
	11th to 20th	Day	6% 16% 9% 25% 15% 6% 3 2 2 3 11%	4650
	21st to end	Day	5% 12% 6% 17% 9% 15% 8% 3 5% 4 15%	5124
February	1st to 10th	Day	11% 15% 6% 17% 11% 7% 5% 3 3 3 18%	1751
	11th to 20th	Day	10% 19% 9% 16% 8% 6% 5% 2 3 3 18%	2033
	21st to end	Day	9% 19% 4 14% 9% 7% 5% 3 4 4 21%	1730
March	1st to 10th	Day	17% 17% 6% 13% 8% 5% 4 2 3 4 21%	4576
	11th to 20th	Day	14% 17% 5% 12% 5% 4 4 3 5% 5% 25%	4920
	21st to end	Day	18% 17% 6% 11% 6% 4 4 3 4 4 24%	5838
April	1st to 10th	Day	20% 19% 4 10% 6% 3 3 3 4 5% 23%	2520
	11th to 20th	Day	18% 18% 4 8% 4 3 3 3 4 4 31%	2603
	21st to end	Day	22% 15% 4 8% 4 4 3 2 4 6% 28%	2730
May	1st to 10th	Day	25% 12% 4 10% 6% 5% 5% 4 5% 5% 20%	6016
	11th to 20th	Day	22% 10% 3 8% 6% 6% 5% 3 5% 6% 26%	6326
	21st to end	Day	19% 10% 3 8% 5% 6% 6% 4 6% 7% 27%	6949
June	1st to 10th	Day	27% 10% 3 6% 5% 5% 4 4 6% 7% 23%	2965
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 5% 6% 8% 30%	3000
	21st to end	Day	22% 10% 4 8% 5% 6% 5% 4 6% 6% 24%	2961
July	1st to 10th	Day	16% 8% 3 9% 6% 7% 7% 6% 7% 8% 24%	6360
	11th to 20th	Day	14% 7% 3 8% 5% 6% 5% 4 7% 9% 33%	6360
	21st to end	Day	14% 7% 3 7% 5% 4 5% 4 6% 8% 38%	6926
August	1st to 10th	Day	18% 8% 3 8% 5% 6% 6% 5% 7% 8% 26%	4415
	11th to 20th	Day	18% 8% 3 10% 6% 5% 6% 4 6% 8% 25%	4175
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 6% 7% 34%	4487
September	1st to 10th	Day	17% 7% 2 6% 4 5% 4 4 6% 6% 38%	2390
	11th to 20th	Day	17% 9% 2 6% 4 3 3 4 4 6% 42%	2200
	21st to end	Day	18% 8% 3 7% 4 4 4 4 5% 8% 34%	2200
October	1st to 10th	Day	18% 12% 3 7% 4 3 4 4 5% 8% 32%	2200
	11th to 20th	Day	16% 17% 4 10% 5% 4 5% 3 5% 6% 25%	1866
	21st to end	Day	22% 20% 5% 9% 4 4 3 3 4 4 21%	1980
November	1st to 10th	Day	16% 21% 6% 9% 5% 4 3 3 4 4 26%	1851
	11th to 20th	Day	16% 19% 7% 13% 5% 4 4 3 3 5% 21%	1890
	21st to end	Day	16% 19% 8% 15% 6% 5% 4 3 4 5% 17%	1647
December	1st to 10th	Day	12% 20% 9% 20% 10% 5% 4 2 3 3 12%	2350
	11th to 20th	Day	15% 18% 7% 13% 6% 4 4 3 3 5% 22%	2688
	21st to end	Day	15% 20% 6% 14% 6% 4 5% 3 3 5% 18%	3806
January	1st to 10th	Night	9% 18% 8% 21% 10% 8% 6% 3 4 3 10%	8234
	11th to 20th	Night	8% 19% 10% 22% 14% 7% 5% 3 3 2 8%	8235
	21st to end	Night	6% 12% 8% 16% 9% 12% 8% 5% 5% 4 15%	9057
February	1st to 10th	Night	10% 15% 6% 15% 10% 7% 6% 3 4 4 20%	2867
	11th to 20th	Night	9% 18% 7% 18% 8% 7% 4 3 3 5% 18%	2468
	21st to end	Night	10% 17% 7% 13% 7% 6% 6% 3 3 5% 24%	2076
March	1st to 10th	Night	17% 18% 6% 14% 5% 5% 7% 2 3 4 18%	5484
	11th to 20th	Night	12% 16% 6% 13% 6% 5% 4 3 4 5% 24%	5245
	21st to end	Night	17% 16% 5% 12% 6% 4 3 3 4 4 25%	5319
April	1st to 10th	Night	20% 17% 5% 9% 4 3 3 3 4 4 27%	2100
	11th to 20th	Night	19% 14% 4 7% 5% 4 4 4 4 5% 30%	1965
	21st to end	Night	20% 14% 4 8% 5% 3 5% 3 5% 5% 29%	1890
May	1st to 10th	Night	24% 11% 4 9% 5% 5% 5% 4 5% 6% 22%	4144
	11th to 20th	Night	21% 10% 3 7% 5% 4 4 3 5% 6% 30%	3728
	21st to end	Night	21% 8% 2 6% 5% 4 4 4 6% 8% 33%	3926
June	1st to 10th	Night	26% 10% 2 7% 4 4 5% 3 5% 7% 27%	1430
	11th to 20th	Night	18% 9% 2 7% 4 4 4 5% 6% 8% 33%	1400
	21st to end	Night	19% 8% 3 9% 5% 4 5% 4 6% 6% 32%	1432
July	1st to 10th	Night	17% 9% 4 9% 5% 6% 5% 4 5% 7% 30%	3600
	11th to 20th	Night	17% 7% 2 7% 5% 5% 4 4 6% 7% 36%	3600
	21st to end	Night	12% 7% 3 6% 4 5% 5% 5% 7% 8% 38%	3926
August	1st to 10th	Night	21% 8% 3 8% 4 4 4 4 4 7% 33%	2701
	11th to 20th	Night	15% 8% 3 8% 6% 7% 6% 4 7% 7% 31%	2872
	21st to end	Night	17% 8% 2 6% 4 5% 4 3 5% 6% 39%	3408
September	1st to 10th	Night	14% 8% 2 6% 3 4 4 4 5% 7% 42%	2010
	11th to 20th	Night	16% 8% 2 5% 3 3 3 4 5% 6% 45%	2200
	21st to end	Night	17% 9% 2 6% 4 4 3 3 4 8% 40%	2200
October	1st to 10th	Night	18% 9% 3 6% 5% 4 4 3 5% 7% 37%	2200
	11th to 20th	Night	20% 15% 4 7% 5% 4 4 3 5% 5% 29%	2529
	21st to end	Night	21% 17% 4 8% 5% 4 4 4 4 4 25%	2860
November	1st to 10th	Night	19% 18% 5% 9% 4 4 4 3 4 5% 25%	2667
	11th to 20th	Night	16% 15% 7% 13% 5% 4 3 3 4 5% 24%	2730
	21st to end	Night	15% 18% 8% 14% 7% 4 4 2 4 4 19%	2966
December	1st to 10th	Night	12% 19% 10% 22% 10% 5% 4 3 3 3 9%	5060
	11th to 20th	Night	14% 20% 6% 16% 9% 5% 4 3 4 4 15%	5741
	21st to end	Night	16% 19% 7% 10% 7% 4 4 3 3 4 23%	7385

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	69% 9% 8% 11% 3 1	4662
	11th to 20th	Day	71% 8% 5% 10% 4 1	4680
	21st to end	Day	62% 9% 8% 9% 11% 1	5124
February	1st to 10th	Day	68% 6% 5% 12% 8% 1	1751
	11th to 20th	Day	69% 6% 7% 11% 7% 1	2042
	21st to end	Day	63% 6% 7% 13% 8% 2	1730
March	1st to 10th	Day	66% 6% 7% 9% 8% 4	4579
	11th to 20th	Day	57% 8% 13% 13% 8% 1	4920
	21st to end	Day	60% 7% 6% 14% 12% 2	5838
April	1st to 10th	Day	64% 4 8% 13% 9% 2	2520
	11th to 20th	Day	56% 4 8% 19% 12% 1	2603
	21st to end	Day	58% 5% 8% 16% 10% 3	2730
May	1st to 10th	Day	65% 7% 8% 14% 6% 1	6027
	11th to 20th	Day	58% 8% 12% 14% 6% 2	6330
	21st to end	Day	52% 9% 11% 18% 9% 1	6949
June	1st to 10th	Day	59% 7% 9% 19% 6%	2965
	11th to 20th	Day	49% 8% 12% 21% 10% 1	3000
	21st to end	Day	57% 8% 10% 18% 7%	2961
July	1st to 10th	Day	50% 9% 17% 17% 6%	6290
	11th to 20th	Day	43% 10% 15% 27% 5%	6285
	21st to end	Day	43% 7% 14% 29% 7%	6728
August	1st to 10th	Day	51% 9% 16% 20% 4	4401
	11th to 20th	Day	52% 10% 16% 17% 5%	4214
	21st to end	Day	46% 8% 14% 20% 11% 2	4487
September	1st to 10th	Day	42% 8% 14% 24% 11%	2390
	11th to 20th	Day	41% 5% 11% 28% 14% 1	2200
	21st to end	Day	46% 7% 12% 23% 11% 1	2200
October	1st to 10th	Day	50% 8% 13% 21% 8%	3590
	11th to 20th	Day	53% 6% 11% 22% 7%	3004
	21st to end	Day	52% 5% 15% 18% 10%	3180
November	1st to 10th	Day	60% 5% 10% 16% 8% 1	1851
	11th to 20th	Day	64% 6% 9% 13% 7% 1	1890
	21st to end	Day	66% 8% 9% 13% 3	1647
December	1st to 10th	Day	75% 6% 7% 8% 4	2350
	11th to 20th	Day	60% 7% 9% 11% 12% 1	2688
	21st to end	Day	65% 6% 6% 10% 8% 3	3806
January	1st to 10th	Night	71% 9% 9% 8% 3	8234
	11th to 20th	Night	77% 7% 6% 6% 3	8280
	21st to end	Night	61% 8% 9% 12% 9% 1	9057
February	1st to 10th	Night	64% 7% 8% 13% 7% 1	2867
	11th to 20th	Night	67% 6% 8% 12% 6% 1	2470
	21st to end	Night	60% 6% 7% 16% 10% 1	2076
March	1st to 10th	Night	68% 5% 8% 11% 6% 2	5494
	11th to 20th	Night	60% 7% 14% 11% 7% 1	5246
	21st to end	Night	58% 6% 7% 15% 13% 1	5319
April	1st to 10th	Night	60% 4 8% 14% 12% 1	2100
	11th to 20th	Night	53% 7% 10% 17% 12% 1	1965
	21st to end	Night	56% 6% 10% 16% 10% 2	1890
May	1st to 10th	Night	60% 8% 13% 12% 6%	4150
	11th to 20th	Night	54% 8% 13% 20% 5%	3729
	21st to end	Night	47% 8% 16% 17% 12%	3927
June	1st to 10th	Night	56% 6% 12% 19% 7%	1430
	11th to 20th	Night	48% 7% 13% 20% 11% 1	1400
	21st to end	Night	52% 7% 13% 21% 8%	1432
July	1st to 10th	Night	47% 10% 17% 19% 6%	3560
	11th to 20th	Night	42% 10% 15% 27% 5%	3552
	21st to end	Night	40% 10% 17% 26% 6%	3809
August	1st to 10th	Night	50% 9% 15% 23% 3	2691
	11th to 20th	Night	46% 12% 19% 18% 5% 1	2899
	21st to end	Night	42% 8% 14% 22% 14% 1	3408
September	1st to 10th	Night	39% 7% 16% 28% 10%	2010
	11th to 20th	Night	39% 5% 14% 28% 13% 1	2200
	21st to end	Night	43% 7% 13% 24% 11% 1	2200
October	1st to 10th	Night	47% 8% 12% 22% 11%	3590
	11th to 20th	Night	50% 8% 11% 22% 8%	4130
	21st to end	Night	51% 7% 14% 19% 8% 2	4610
November	1st to 10th	Night	61% 5% 11% 15% 7% 1	2667
	11th to 20th	Night	62% 5% 10% 13% 9% 1	2730
	21st to end	Night	67% 6% 11% 12% 4	2966
December	1st to 10th	Night	75% 7% 8% 8% 2	5060
	11th to 20th	Night	68% 7% 8% 10% 7%	5742
	21st to end	Night	64% 6% 6% 13% 9% 2	7385

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	31% 31% 30% 9%	220
	11th to 20th	Day	30% 29% 28% 11% 2	220
	21st to end	Day	30% 21% 36% 12% 1	242
February	1st to 10th	Day	30% 29% 24% 15% 2	291
	11th to 20th	Day	30% 33% 28% 8% 2	529
	21st to end	Day	31% 28% 27% 12% 2	446
March	1st to 10th	Day	29% 29% 29% 10% 3	540
	11th to 20th	Day	34% 27% 24% 11% 3 1	540
	21st to end	Day	35% 22% 24% 11% 6% 1	594
April	1st to 10th	Day	39% 21% 23% 10% 5% 1	540
	11th to 20th	Day	35% 27% 22% 10% 4 2	532
	21st to end	Day	35% 24% 27% 8% 4 2	540
May	1st to 10th	Day	38% 19% 30% 9% 3 1	543
	11th to 20th	Day	28% 21% 28% 16% 6% 1	551
	21st to end	Day	22% 25% 34% 14% 4 1	573
June	1st to 10th	Day	30% 19% 29% 16% 6% 1	695
	11th to 20th	Day	22% 18% 28% 21% 10% 1	730
	21st to end	Day	26% 14% 31% 20% 8% 1	691
July	1st to 10th	Day	19% 18% 34% 20% 7% 1	525
	11th to 20th	Day	18% 14% 40% 18% 9% 1	524
	21st to end	Day	16% 16% 37% 22% 8% 1	576
August	1st to 10th	Day	17% 15% 33% 23% 10% 2	526
	11th to 20th	Day	17% 16% 27% 23% 13% 4	519
	21st to end	Day	19% 20% 25% 21% 11% 3	583
September	1st to 10th	Day	19% 18% 26% 21% 11% 5%	530
	11th to 20th	Day	21% 13% 25% 21% 12% 8%	530
	21st to end	Day	21% 16% 28% 19% 12% 5%	530
October	1st to 10th	Day	23% 18% 25% 18% 11% 4	530
	11th to 20th	Day	27% 24% 23% 16% 8% 2	428
	21st to end	Day	32% 24% 24% 16% 5%	462
November	1st to 10th	Day	33% 23% 24% 16% 4	425
	11th to 20th	Day	28% 26% 25% 13% 6% 1	430
	21st to end	Day	34% 25% 25% 12% 2 1	321
December	1st to 10th	Day	27% 25% 32% 13% 3	220
	11th to 20th	Day	36% 28% 26% 6% 3	220
	21st to end	Day	37% 28% 22% 8% 5% 1	242
January	1st to 10th	Night	24% 28% 31% 14% 3	840
	11th to 20th	Night	23% 28% 28% 17% 3	840
	21st to end	Night	18% 27% 33% 18% 3	924
February	1st to 10th	Night	22% 26% 33% 16% 4	840
	11th to 20th	Night	24% 29% 30% 16% 2	823
	21st to end	Night	25% 23% 34% 15% 2	692
March	1st to 10th	Night	27% 22% 30% 18% 3	840
	11th to 20th	Night	27% 25% 25% 18% 5%	840
	21st to end	Night	27% 23% 24% 20% 6% 1	924
April	1st to 10th	Night	32% 21% 26% 16% 5%	840
	11th to 20th	Night	28% 20% 23% 23% 6%	721
	21st to end	Night	31% 19% 25% 19% 6%	630
May	1st to 10th	Night	27% 16% 27% 23% 6% 1	630
	11th to 20th	Night	23% 15% 29% 27% 6% 1	459
	21st to end	Night	24% 11% 27% 29% 8%	433
June	1st to 10th	Night	28% 12% 26% 29% 7%	400
	11th to 20th	Night	21% 14% 19% 30% 16% 1	400
	21st to end	Night	20% 8% 30% 33% 10%	400
July	1st to 10th	Night	15% 10% 27% 32% 13% 1	390
	11th to 20th	Night	17% 6% 26% 37% 13% 2	388
	21st to end	Night	16% 8% 22% 39% 15%	438
August	1st to 10th	Night	17% 5% 22% 36% 18% 2	461
	11th to 20th	Night	14% 10% 23% 34% 18% 1	592
	21st to end	Night	17% 9% 26% 30% 16% 2	767
September	1st to 10th	Night	15% 10% 27% 31% 16% 1	800
	11th to 20th	Night	20% 10% 19% 28% 21% 2	800
	21st to end	Night	21% 12% 25% 25% 16% 2	800
October	1st to 10th	Night	23% 12% 23% 29% 13% 1	800
	11th to 20th	Night	27% 18% 24% 20% 9% 2	800
	21st to end	Night	30% 21% 25% 20% 4	880
November	1st to 10th	Night	31% 20% 23% 21% 5%	820
	11th to 20th	Night	25% 24% 25% 17% 8% 2	840
	21st to end	Night	27% 23% 26% 18% 5% 1	909
December	1st to 10th	Night	29% 24% 29% 15% 4	950
	11th to 20th	Night	32% 25% 22% 16% 5%	950
	21st to end	Night	32% 25% 27% 12% 4	979

Page generated at 2026-05-14 01:59:00. Version ac07

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