Wind Dancer Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wind Dancer Ridge Observatory clear sky chart from 2005-11-06 to 2025-02-06.

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	15% 10% 3 8% 5% 4 4 4 5% 7% 35%	109066
	Night	15% 10% 3 8% 5% 4 4 3 5% 7% 35%	109199
Transparency	Day	47% 5% 10% 23% 14% 2	112782
	Night	47% 5% 9% 22% 15% 3	113622
Seeing	Day	22% 11% 25% 22% 15% 6%	15287
	Night	20% 9% 23% 30% 16% 2	25442

By Month

Percentage Cloud Cover SE (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% 18% 8% 16% 7% 4 4 2 3 5% 18%	4056
	11th to 20th	Day	15% 19% 8% 12% 6% 4 3 2 3 3 25%	4060
	21st to end	Day	18% 15% 4 8% 6% 4 4 3 4 5% 28%	4466
February	1st to 10th	Day	21% 13% 6% 8% 5% 4 3 3 3 5% 29%	1755
	11th to 20th	Day	22% 12% 4 10% 4 4 3 4 4 6% 28%	1805
	21st to end	Day	22% 15% 4 6% 4 3 3 3 4 5% 31%	1570
March	1st to 10th	Day	22% 13% 4 8% 5% 4 4 4 4 6% 28%	3367
	11th to 20th	Day	15% 7% 3 6% 4 5% 4 3 5% 7% 41%	3480
	21st to end	Day	18% 9% 3 8% 4 4 5% 4 6% 7% 33%	3815
April	1st to 10th	Day	14% 11% 3 7% 5% 4 4 3 5% 7% 37%	2090
	11th to 20th	Day	16% 8% 3 7% 5% 4 3 3 4 7% 40%	2363
	21st to end	Day	18% 8% 3 6% 5% 4 4 4 6% 7% 36%	2470
May	1st to 10th	Day	19% 10% 4 8% 6% 5% 5% 4 6% 6% 28%	4082
	11th to 20th	Day	18% 10% 3 7% 5% 4 4 3 6% 7% 33%	4081
	21st to end	Day	10% 6% 3 7% 5% 6% 5% 5% 7% 10% 37%	4476
June	1st to 10th	Day	12% 6% 2 5% 5% 5% 5% 4 8% 9% 40%	2470
	11th to 20th	Day	9% 6% 2 5% 5% 5% 5% 4 8% 11% 40%	2470
	21st to end	Day	9% 6% 2 6% 5% 5% 6% 5% 7% 10% 39%	2470
July	1st to 10th	Day	9% 5% 2 7% 5% 4 5% 4 7% 9% 43%	4120
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 5% 6% 10% 41%	4120
	21st to end	Day	15% 9% 4 9% 6% 5% 6% 4 6% 8% 28%	4466
August	1st to 10th	Day	8% 7% 3 7% 5% 5% 6% 5% 8% 11% 34%	4104
	11th to 20th	Day	10% 6% 3 7% 6% 5% 6% 5% 7% 9% 35%	4044
	21st to end	Day	6% 4 2 4 4 4 4 4 6% 9% 53%	4418
September	1st to 10th	Day	13% 6% 2 4 3 4 5% 4 6% 6% 47%	2094
	11th to 20th	Day	10% 6% 2 7% 4 4 4 4 5% 8% 47%	2090
	21st to end	Day	19% 7% 2 6% 4 4 3 3 5% 6% 41%	2090
October	1st to 10th	Day	14% 6% 2 5% 3 3 4 3 5% 7% 48%	2001
	11th to 20th	Day	14% 8% 3 6% 3 4 4 3 4 6% 47%	1900
	21st to end	Day	19% 8% 3 6% 4 3 4 2 4 7% 41%	2090
November	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 4 6% 50%	1814
	11th to 20th	Day	14% 11% 4 8% 4 4 4 2 5% 6% 38%	1800
	21st to end	Day	16% 12% 3 7% 4 4 4 3 4 7% 36%	1800
December	1st to 10th	Day	19% 12% 3 11% 5% 4 4 3 4 5% 31%	2930
	11th to 20th	Day	24% 13% 4 8% 5% 4 5% 3 5% 4 26%	3373
	21st to end	Day	17% 15% 5% 11% 6% 5% 5% 4 5% 6% 21%	4466
January	1st to 10th	Night	16% 17% 6% 16% 6% 4 4 3 4 5% 20%	5889
	11th to 20th	Night	19% 14% 6% 12% 5% 4 4 3 4 5% 25%	5900
	21st to end	Night	21% 10% 4 8% 5% 5% 4 3 4 5% 31%	6490
February	1st to 10th	Night	19% 12% 4 8% 5% 5% 4 3 5% 6% 29%	2536
	11th to 20th	Night	23% 11% 4 10% 5% 4 4 3 3 5% 28%	2256
	21st to end	Night	22% 15% 3 7% 5% 4 4 4 4 6% 27%	1884
March	1st to 10th	Night	23% 12% 3 6% 4 5% 4 3 5% 5% 31%	3484
	11th to 20th	Night	14% 10% 3 6% 4 4 4 4 5% 7% 39%	3480
	21st to end	Night	14% 8% 3 7% 5% 5% 4 4 5% 7% 38%	3817
April	1st to 10th	Night	15% 10% 3 7% 5% 4 4 3 5% 8% 38%	2090
	11th to 20th	Night	13% 7% 2 8% 4 4 4 4 5% 8% 40%	1778
	21st to end	Night	15% 7% 3 6% 5% 6% 5% 3 5% 6% 39%	1710
May	1st to 10th	Night	21% 11% 4 8% 5% 4 5% 4 5% 7% 25%	2813
	11th to 20th	Night	19% 8% 3 6% 4 5% 4 3 5% 8% 35%	2812
	21st to end	Night	11% 7% 2 7% 4 4 5% 4 6% 9% 40%	3079
June	1st to 10th	Night	8% 6% 2 6% 4 4 4 5% 7% 9% 44%	1710
	11th to 20th	Night	6% 5% 3 6% 5% 5% 5% 4 7% 10% 42%	1710
	21st to end	Night	9% 6% 2 5% 4 3 5% 5% 7% 9% 44%	1710
July	1st to 10th	Night	7% 7% 2 6% 5% 5% 5% 4 7% 10% 42%	2840
	11th to 20th	Night	7% 6% 2 7% 4 5% 5% 4 6% 9% 45%	2840
	21st to end	Night	11% 9% 4 8% 5% 5% 5% 5% 6% 7% 35%	3087
August	1st to 10th	Night	10% 7% 3 8% 5% 5% 6% 4 8% 9% 34%	2825
	11th to 20th	Night	10% 6% 3 8% 5% 4 4 4 6% 8% 42%	2785
	21st to end	Night	5% 3 2 4 4 4 5% 4 7% 9% 55%	3205
September	1st to 10th	Night	11% 5% 2 5% 3 3 5% 4 6% 7% 48%	2082
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 3 5% 8% 50%	2090
	21st to end	Night	14% 7% 2 6% 4 5% 4 4 5% 6% 43%	2090
October	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 5% 6% 50%	2177
	11th to 20th	Night	13% 7% 3 6% 4 3 4 3 5% 7% 45%	2280
	21st to end	Night	18% 6% 2 7% 4 5% 4 3 4 6% 42%	2508
November	1st to 10th	Night	11% 6% 3 6% 4 3 4 4 4 5% 49%	2480
	11th to 20th	Night	17% 8% 2 7% 4 4 3 4 5% 7% 39%	2600
	21st to end	Night	17% 10% 3 7% 5% 4 3 3 4 5% 38%	2600
December	1st to 10th	Night	16% 12% 4 11% 5% 5% 3 3 5% 5% 31%	4250
	11th to 20th	Night	19% 14% 6% 9% 5% 4 3 3 4 5% 28%	4822
	21st to end	Night	16% 16% 4 10% 6% 5% 5% 4 5% 6% 22%	6490

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	70% 3 8% 13% 5%	4057
	11th to 20th	Day	66% 3 5% 15% 10% 1	4060
	21st to end	Day	60% 2 8% 21% 8% 1	4466
February	1st to 10th	Day	59% 4 9% 18% 9% 1	1755
	11th to 20th	Day	59% 5% 7% 18% 10% 2	1815
	21st to end	Day	56% 4 8% 20% 11% 2	1570
March	1st to 10th	Day	58% 4 8% 20% 8% 1	3367
	11th to 20th	Day	43% 4 8% 27% 17% 1	3480
	21st to end	Day	49% 6% 8% 24% 13% 1	3815
April	1st to 10th	Day	47% 4 10% 21% 13% 4	2090
	11th to 20th	Day	44% 4 8% 23% 17% 4	2363
	21st to end	Day	47% 5% 11% 22% 12% 3	2470
May	1st to 10th	Day	55% 6% 9% 19% 10% 1	4120
	11th to 20th	Day	50% 6% 10% 21% 12% 1	4085
	21st to end	Day	39% 7% 15% 20% 14% 4	4489
June	1st to 10th	Day	38% 6% 13% 25% 16% 1	2470
	11th to 20th	Day	37% 7% 15% 22% 17% 2	2470
	21st to end	Day	38% 8% 14% 24% 14% 3	2470
July	1st to 10th	Day	36% 7% 14% 27% 13% 3	4055
	11th to 20th	Day	35% 6% 12% 31% 14% 1	4051
	21st to end	Day	52% 6% 10% 15% 15% 1	4324
August	1st to 10th	Day	39% 8% 15% 27% 10%	4091
	11th to 20th	Day	41% 7% 11% 27% 14% 1	4083
	21st to end	Day	27% 6% 14% 30% 21% 2	4418
September	1st to 10th	Day	35% 6% 9% 23% 22% 6%	2094
	11th to 20th	Day	36% 6% 9% 26% 21% 2	2090
	21st to end	Day	44% 4 10% 22% 19% 2	2090
October	1st to 10th	Day	28% 4 8% 24% 33% 3	3326
	11th to 20th	Day	29% 2 11% 29% 23% 6%	3140
	21st to end	Day	32% 3 10% 29% 22% 4	3428
November	1st to 10th	Day	36% 4 8% 27% 21% 4	1814
	11th to 20th	Day	48% 3 6% 21% 19% 3	1800
	21st to end	Day	49% 3 10% 22% 16% 1	1800
December	1st to 10th	Day	58% 2 7% 23% 8% 1	2930
	11th to 20th	Day	62% 3 9% 16% 9%	3370
	21st to end	Day	64% 4 10% 17% 4	4466
January	1st to 10th	Night	67% 4 8% 15% 6% 1	5889
	11th to 20th	Night	63% 3 6% 17% 8% 3	5900
	21st to end	Night	57% 3 8% 22% 10% 1	6490
February	1st to 10th	Night	57% 4 9% 19% 11% 1	2536
	11th to 20th	Night	59% 4 6% 18% 12% 1	2257
	21st to end	Night	58% 3 10% 16% 10% 3	1884
March	1st to 10th	Night	54% 4 5% 22% 13% 1	3484
	11th to 20th	Night	43% 5% 8% 26% 17% 1	3480
	21st to end	Night	45% 5% 7% 24% 17% 2	3817
April	1st to 10th	Night	45% 5% 8% 21% 18% 3	2090
	11th to 20th	Night	42% 4 10% 21% 16% 7%	1778
	21st to end	Night	45% 5% 10% 20% 18% 2	1710
May	1st to 10th	Night	57% 6% 10% 15% 11% 2	2840
	11th to 20th	Night	47% 6% 11% 22% 11% 2	2813
	21st to end	Night	37% 9% 13% 24% 14% 5%	3087
June	1st to 10th	Night	35% 7% 13% 25% 17% 3	1710
	11th to 20th	Night	35% 8% 15% 18% 21% 3	1710
	21st to end	Night	33% 8% 14% 26% 16% 3	1710
July	1st to 10th	Night	36% 7% 13% 23% 16% 4	2795
	11th to 20th	Night	34% 7% 13% 29% 15% 2	2786
	21st to end	Night	45% 7% 11% 20% 12% 5%	2988
August	1st to 10th	Night	43% 8% 14% 24% 10% 1	2814
	11th to 20th	Night	39% 5% 11% 25% 20% 1	2812
	21st to end	Night	25% 6% 12% 31% 23% 2	3205
September	1st to 10th	Night	33% 6% 12% 22% 19% 8%	2082
	11th to 20th	Night	32% 6% 10% 24% 25% 4	2090
	21st to end	Night	41% 6% 10% 21% 21% 2	2090
October	1st to 10th	Night	31% 3 8% 22% 32% 4	3632
	11th to 20th	Night	29% 3 8% 26% 24% 9%	3779
	21st to end	Night	31% 3 6% 26% 27% 6%	4120
November	1st to 10th	Night	36% 4 9% 23% 23% 5%	2480
	11th to 20th	Night	45% 3 7% 20% 20% 4	2600
	21st to end	Night	49% 3 9% 23% 15% 1	2600
December	1st to 10th	Night	55% 4 11% 22% 8% 1	4250
	11th to 20th	Night	59% 3 11% 20% 7% 1	4824
	21st to end	Night	62% 4 9% 17% 7%	6490

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	32% 19% 34% 10% 4 1	300
	11th to 20th	Day	38% 23% 28% 8% 3	300
	21st to end	Day	34% 22% 28% 10% 5%	330
February	1st to 10th	Day	34% 20% 30% 13% 3	285
	11th to 20th	Day	47% 18% 26% 5% 4	270
	21st to end	Day	40% 19% 32% 8% 1	225
March	1st to 10th	Day	29% 17% 29% 18% 5% 1	414
	11th to 20th	Day	27% 19% 32% 15% 6% 1	460
	21st to end	Day	28% 19% 29% 17% 6%	506
April	1st to 10th	Day	26% 19% 27% 19% 8% 1	460
	11th to 20th	Day	21% 17% 33% 17% 9% 4	452
	21st to end	Day	26% 15% 29% 20% 8% 2	460
May	1st to 10th	Day	26% 16% 27% 20% 6% 5%	463
	11th to 20th	Day	21% 11% 26% 24% 13% 6%	487
	21st to end	Day	14% 7% 22% 27% 21% 9%	529
June	1st to 10th	Day	13% 7% 23% 26% 22% 9%	490
	11th to 20th	Day	13% 5% 21% 30% 22% 8%	490
	21st to end	Day	10% 6% 29% 25% 21% 9%	490
July	1st to 10th	Day	16% 4 17% 22% 21% 20%	485
	11th to 20th	Day	10% 3 21% 29% 25% 12%	484
	21st to end	Day	15% 4 17% 27% 26% 11%	532
August	1st to 10th	Day	13% 5% 15% 32% 23% 12%	486
	11th to 20th	Day	16% 5% 13% 30% 23% 13%	479
	21st to end	Day	10% 3 15% 29% 28% 14%	539
September	1st to 10th	Day	14% 4 15% 26% 27% 14%	490
	11th to 20th	Day	13% 2 13% 29% 31% 13%	490
	21st to end	Day	24% 7% 20% 23% 19% 6%	490
October	1st to 10th	Day	14% 6% 27% 24% 21% 8%	490
	11th to 20th	Day	18% 12% 26% 26% 13% 5%	490
	21st to end	Day	25% 10% 28% 24% 10% 2	539
November	1st to 10th	Day	17% 13% 31% 26% 11% 2	352
	11th to 20th	Day	26% 15% 31% 19% 8% 1	300
	21st to end	Day	25% 18% 31% 21% 5%	300
December	1st to 10th	Day	31% 18% 30% 14% 6% 1	300
	11th to 20th	Day	32% 17% 29% 18% 3 1	300
	21st to end	Day	32% 16% 32% 15% 5% 1	330
January	1st to 10th	Night	28% 17% 29% 22% 5%	800
	11th to 20th	Night	33% 14% 29% 21% 3	800
	21st to end	Night	26% 16% 32% 23% 4	880
February	1st to 10th	Night	29% 11% 30% 29% 2	781
	11th to 20th	Night	32% 15% 30% 21% 1	743
	21st to end	Night	32% 13% 32% 20% 2	628
March	1st to 10th	Night	27% 13% 27% 28% 5%	760
	11th to 20th	Night	25% 15% 30% 22% 7% 1	760
	21st to end	Night	24% 11% 30% 27% 7%	836
April	1st to 10th	Night	23% 13% 30% 27% 7%	760
	11th to 20th	Night	19% 10% 29% 30% 12% 1	639
	21st to end	Night	21% 7% 33% 31% 8% 1	570
May	1st to 10th	Night	19% 8% 26% 32% 13% 1	570
	11th to 20th	Night	19% 6% 23% 34% 16% 1	561
	21st to end	Night	13% 4 17% 33% 31% 3	617
June	1st to 10th	Night	11% 2 17% 40% 26% 3	570
	11th to 20th	Night	8% 3 15% 40% 29% 4	570
	21st to end	Night	11% 3 15% 38% 30% 2	570
July	1st to 10th	Night	11% 3 12% 37% 31% 7%	555
	11th to 20th	Night	9% 3 12% 37% 36% 4	552
	21st to end	Night	11% 2 12% 34% 36% 4	624
August	1st to 10th	Night	13% 2 8% 38% 34% 4	567
	11th to 20th	Night	12% 3 10% 34% 35% 7%	564
	21st to end	Night	10% 2 9% 34% 38% 7%	669
September	1st to 10th	Night	14% 2 9% 34% 36% 5%	760
	11th to 20th	Night	13% 2 13% 32% 35% 5%	760
	21st to end	Night	18% 6% 16% 33% 24% 3	760
October	1st to 10th	Night	14% 5% 19% 33% 27% 3	760
	11th to 20th	Night	16% 8% 26% 32% 17% 2	760
	21st to end	Night	22% 8% 22% 33% 14% 1	836
November	1st to 10th	Night	15% 7% 26% 34% 17% 1	780
	11th to 20th	Night	23% 11% 25% 30% 11%	800
	21st to end	Night	24% 11% 22% 35% 7% 1	800
December	1st to 10th	Night	31% 12% 26% 26% 5%	800
	11th to 20th	Night	27% 12% 27% 28% 6%	800
	21st to end	Night	29% 14% 25% 29% 4	880

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