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 2026-06-01.

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	14% 9% 3 8% 5% 4 5% 4 6% 7% 34%	132411
	Night	15% 10% 3 8% 5% 4 4 4 5% 7% 35%	130751
Transparency	Day	47% 5% 10% 22% 14% 2	136083
	Night	47% 5% 10% 21% 15% 2	135149
Seeing	Day	22% 12% 25% 22% 14% 6%	17063
	Night	21% 9% 23% 30% 16% 2	27177

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% 19% 8% 14% 6% 4 3 2 3 5% 20%	5258
	11th to 20th	Day	14% 17% 7% 13% 6% 4 3 2 3 4 27%	5280
	21st to end	Day	17% 14% 4 11% 7% 5% 4 4 4 6% 24%	5780
February	1st to 10th	Day	20% 13% 6% 8% 5% 4 3 3 3 5% 29%	1890
	11th to 20th	Day	23% 12% 4 10% 4 4 3 3 4 5% 27%	2001
	21st to end	Day	21% 14% 4 6% 4 3 4 3 4 5% 31%	1730
March	1st to 10th	Day	17% 13% 4 8% 5% 5% 4 4 4 6% 31%	4947
	11th to 20th	Day	13% 7% 3 6% 4 5% 4 3 5% 7% 42%	5090
	21st to end	Day	16% 9% 3 8% 4 5% 5% 4 6% 7% 32%	5586
April	1st to 10th	Day	14% 11% 2 7% 5% 4 4 3 5% 7% 38%	2310
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 7% 40%	2615
	21st to end	Day	17% 8% 3 7% 6% 4 4 4 6% 7% 36%	2730
May	1st to 10th	Day	16% 9% 4 9% 6% 5% 6% 5% 7% 8% 26%	5992
	11th to 20th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 8% 30%	5991
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 5% 7% 9% 33%	6576
June	1st to 10th	Day	12% 6% 2 5% 5% 5% 5% 4 8% 9% 40%	2600
	11th to 20th	Day	9% 6% 2 6% 5% 5% 6% 4 8% 11% 39%	2600
	21st to end	Day	9% 6% 2 5% 5% 5% 6% 5% 8% 10% 39%	2600
July	1st to 10th	Day	8% 6% 3 7% 5% 4 5% 4 6% 9% 44%	5900
	11th to 20th	Day	9% 7% 3 7% 6% 6% 6% 5% 8% 11% 33%	5900
	21st to end	Day	12% 8% 4 9% 6% 5% 6% 4 7% 9% 30%	6424
August	1st to 10th	Day	9% 7% 3 7% 5% 5% 6% 5% 8% 11% 34%	4234
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 10% 36%	4174
	21st to end	Day	5% 4 2 4 4 4 4 4 6% 9% 53%	4558
September	1st to 10th	Day	13% 6% 2 4 3 4 5% 4 6% 6% 48%	2204
	11th to 20th	Day	10% 6% 2 7% 4 4 4 4 5% 8% 47%	2200
	21st to end	Day	18% 7% 2 6% 4 4 3 3 5% 6% 40%	2200
October	1st to 10th	Day	14% 6% 2 5% 3 3 4 3 5% 7% 50%	2106
	11th to 20th	Day	14% 8% 3 5% 3 4 4 3 4 6% 48%	2000
	21st to end	Day	19% 8% 3 6% 4 3 4 2 4 7% 41%	2200
November	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 4 6% 49%	1907
	11th to 20th	Day	14% 11% 4 8% 4 4 4 2 5% 6% 38%	1890
	21st to end	Day	16% 12% 3 7% 4 4 4 3 4 7% 35%	1890
December	1st to 10th	Day	19% 13% 3 11% 5% 4 4 3 4 4 30%	3020
	11th to 20th	Day	23% 13% 4 8% 5% 4 4 3 5% 5% 26%	3463
	21st to end	Day	17% 16% 5% 12% 6% 5% 5% 4 5% 6% 21%	4565
January	1st to 10th	Night	16% 16% 5% 14% 5% 5% 5% 3 5% 5% 21%	7635
	11th to 20th	Night	17% 13% 5% 13% 6% 4 4 3 4 5% 25%	7680
	21st to end	Night	19% 11% 4 10% 7% 5% 4 3 4 5% 29%	8401
February	1st to 10th	Night	19% 13% 4 8% 5% 5% 4 3 5% 6% 29%	2730
	11th to 20th	Night	23% 12% 4 10% 5% 4 4 3 3 6% 27%	2500
	21st to end	Night	20% 14% 3 7% 5% 4 4 4 4 6% 28%	2076
March	1st to 10th	Night	20% 10% 3 6% 4 4 3 3 5% 6% 37%	5124
	11th to 20th	Night	12% 8% 3 5% 4 4 3 3 5% 9% 43%	5090
	21st to end	Night	14% 9% 3 8% 6% 5% 5% 4 5% 6% 33%	5588
April	1st to 10th	Night	15% 9% 3 7% 5% 4 4 3 5% 8% 38%	2310
	11th to 20th	Night	13% 7% 2 7% 5% 4 5% 4 6% 8% 39%	1968
	21st to end	Night	15% 7% 3 6% 5% 6% 5% 4 5% 7% 40%	1890
May	1st to 10th	Night	18% 10% 4 8% 5% 4 5% 5% 7% 8% 26%	4123
	11th to 20th	Night	15% 7% 3 8% 5% 6% 5% 4 6% 8% 32%	4122
	21st to end	Night	15% 9% 3 8% 5% 5% 5% 4 6% 8% 33%	4520
June	1st to 10th	Night	8% 6% 3 6% 4 4 4 5% 7% 9% 44%	1800
	11th to 20th	Night	7% 6% 3 7% 5% 5% 5% 4 7% 10% 42%	1800
	21st to end	Night	9% 5% 2 5% 4 4 5% 5% 7% 9% 45%	1800
July	1st to 10th	Night	7% 7% 2 7% 5% 5% 5% 5% 7% 9% 42%	4058
	11th to 20th	Night	9% 8% 3 8% 5% 5% 5% 5% 7% 10% 36%	4057
	21st to end	Night	9% 8% 3 8% 5% 5% 5% 5% 7% 8% 35%	4427
August	1st to 10th	Night	10% 7% 3 8% 5% 5% 6% 4 7% 9% 34%	2915
	11th to 20th	Night	10% 6% 3 8% 5% 4 5% 4 6% 8% 42%	2875
	21st to end	Night	5% 3 2 4 4 4 5% 4 7% 9% 55%	3306
September	1st to 10th	Night	11% 5% 2 5% 3 3 5% 4 6% 8% 48%	2192
	11th to 20th	Night	9% 6% 2 5% 4 4 5% 3 5% 8% 51%	2200
	21st to end	Night	14% 7% 2 7% 4 5% 5% 4 5% 6% 42%	2200
October	1st to 10th	Night	12% 4 2 6% 3 4 4 3 4 6% 51%	2292
	11th to 20th	Night	13% 7% 3 6% 4 3 4 3 5% 7% 46%	2400
	21st to end	Night	19% 6% 2 7% 3 5% 4 3 4 6% 42%	2640
November	1st to 10th	Night	11% 6% 3 6% 3 3 4 4 4 6% 49%	2607
	11th to 20th	Night	17% 9% 2 6% 4 4 3 4 5% 7% 39%	2730
	21st to end	Night	17% 11% 4 7% 5% 4 3 3 4 5% 37%	2730
December	1st to 10th	Night	16% 13% 4 11% 5% 5% 3 3 5% 5% 30%	4380
	11th to 20th	Night	18% 14% 6% 9% 5% 4 3 3 4 5% 29%	4952
	21st to end	Night	17% 16% 5% 10% 6% 5% 5% 4 5% 6% 22%	6633

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% 3 10% 14% 4	5259
	11th to 20th	Day	62% 3 6% 16% 11% 2	5280
	21st to end	Day	63% 2 7% 20% 6% 1	5780
February	1st to 10th	Day	58% 3 9% 19% 10% 1	1890
	11th to 20th	Day	59% 4 7% 18% 10% 2	2011
	21st to end	Day	55% 4 8% 22% 11% 2	1730
March	1st to 10th	Day	54% 3 7% 20% 11% 4	4947
	11th to 20th	Day	41% 3 8% 25% 20% 3	5090
	21st to end	Day	49% 5% 8% 23% 13% 2	5586
April	1st to 10th	Day	47% 4 10% 22% 13% 4	2310
	11th to 20th	Day	43% 4 10% 22% 17% 4	2615
	21st to end	Day	47% 5% 11% 23% 12% 3	2730
May	1st to 10th	Day	53% 6% 11% 18% 10% 2	6027
	11th to 20th	Day	50% 6% 10% 22% 11% 1	5995
	21st to end	Day	45% 6% 13% 20% 12% 4	6590
June	1st to 10th	Day	38% 6% 14% 25% 16% 1	2600
	11th to 20th	Day	38% 7% 15% 22% 17% 2	2600
	21st to end	Day	37% 8% 15% 24% 14% 3	2600
July	1st to 10th	Day	36% 7% 12% 28% 16% 2	5835
	11th to 20th	Day	42% 8% 15% 25% 10% 1	5831
	21st to end	Day	48% 6% 12% 18% 15% 1	6240
August	1st to 10th	Day	39% 8% 15% 27% 10%	4221
	11th to 20th	Day	40% 6% 11% 28% 14% 1	4213
	21st to end	Day	27% 6% 14% 30% 21% 2	4558
September	1st to 10th	Day	35% 5% 9% 23% 22% 5%	2204
	11th to 20th	Day	35% 6% 9% 27% 22% 2	2200
	21st to end	Day	44% 5% 10% 21% 19% 2	2200
October	1st to 10th	Day	28% 4 8% 24% 34% 3	3431
	11th to 20th	Day	29% 2 11% 29% 24% 6%	3240
	21st to end	Day	33% 3 10% 28% 23% 4	3538
November	1st to 10th	Day	37% 4 8% 27% 21% 4	1907
	11th to 20th	Day	47% 3 7% 22% 19% 2	1890
	21st to end	Day	51% 3 10% 21% 15% 1	1890
December	1st to 10th	Day	59% 2 7% 23% 8% 1	3020
	11th to 20th	Day	61% 3 9% 17% 9%	3460
	21st to end	Day	64% 4 10% 17% 4	4565
January	1st to 10th	Night	65% 3 10% 16% 5%	7636
	11th to 20th	Night	62% 3 6% 17% 11% 2	7680
	21st to end	Night	59% 3 9% 20% 9% 1	8401
February	1st to 10th	Night	57% 3 9% 19% 12% 1	2730
	11th to 20th	Night	59% 4 7% 18% 11% 1	2501
	21st to end	Night	58% 3 10% 17% 10% 3	2076
March	1st to 10th	Night	49% 4 5% 24% 15% 3	5124
	11th to 20th	Night	38% 4 7% 26% 22% 2	5090
	21st to end	Night	51% 4 7% 21% 15% 2	5588
April	1st to 10th	Night	45% 5% 8% 21% 18% 3	2310
	11th to 20th	Night	42% 4 10% 22% 15% 6%	1968
	21st to end	Night	44% 5% 10% 21% 18% 2	1890
May	1st to 10th	Night	54% 7% 12% 14% 11% 2	4150
	11th to 20th	Night	47% 8% 13% 20% 11% 1	4123
	21st to end	Night	46% 7% 13% 20% 10% 3	4528
June	1st to 10th	Night	35% 7% 13% 24% 19% 3	1800
	11th to 20th	Night	36% 8% 15% 17% 21% 3	1800
	21st to end	Night	33% 9% 14% 25% 18% 2	1800
July	1st to 10th	Night	37% 8% 12% 23% 18% 3	4015
	11th to 20th	Night	41% 8% 16% 23% 11% 1	4006
	21st to end	Night	43% 7% 12% 22% 13% 3	4297
August	1st to 10th	Night	43% 8% 14% 24% 10% 1	2904
	11th to 20th	Night	39% 5% 11% 25% 19% 1	2902
	21st to end	Night	25% 6% 12% 31% 23% 2	3306
September	1st to 10th	Night	33% 6% 12% 21% 20% 8%	2192
	11th to 20th	Night	31% 6% 10% 24% 26% 4	2200
	21st to end	Night	42% 6% 10% 20% 20% 2	2200
October	1st to 10th	Night	30% 3 8% 22% 32% 4	3747
	11th to 20th	Night	29% 3 9% 26% 25% 9%	3899
	21st to end	Night	32% 3 6% 26% 27% 6%	4252
November	1st to 10th	Night	36% 4 9% 23% 23% 5%	2607
	11th to 20th	Night	45% 3 7% 21% 20% 4	2730
	21st to end	Night	50% 3 9% 22% 14% 1	2730
December	1st to 10th	Night	55% 4 11% 21% 7% 1	4380
	11th to 20th	Night	59% 3 10% 20% 7% 1	4954
	21st to end	Night	62% 4 9% 17% 7%	6633

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% 18% 34% 10% 4 1	330
	11th to 20th	Day	39% 25% 26% 8% 2	330
	21st to end	Day	35% 23% 28% 9% 5%	363
February	1st to 10th	Day	31% 20% 31% 15% 3	330
	11th to 20th	Day	48% 18% 25% 6% 3	330
	21st to end	Day	35% 22% 32% 10% 1	273
March	1st to 10th	Day	29% 19% 28% 18% 6% 1	490
	11th to 20th	Day	29% 18% 32% 15% 5% 1	540
	21st to end	Day	29% 19% 30% 17% 5%	594
April	1st to 10th	Day	26% 19% 26% 19% 8% 1	540
	11th to 20th	Day	21% 18% 34% 16% 8% 3	532
	21st to end	Day	24% 16% 28% 21% 8% 2	540
May	1st to 10th	Day	25% 18% 28% 19% 6% 4	543
	11th to 20th	Day	20% 12% 28% 24% 12% 5%	567
	21st to end	Day	17% 8% 23% 25% 19% 7%	617
June	1st to 10th	Day	13% 8% 24% 26% 22% 8%	530
	11th to 20th	Day	13% 5% 21% 31% 23% 7%	530
	21st to end	Day	10% 6% 27% 25% 23% 10%	530
July	1st to 10th	Day	16% 3 16% 23% 22% 19%	525
	11th to 20th	Day	10% 4 21% 29% 25% 11%	524
	21st to end	Day	15% 4 17% 27% 26% 11%	576
August	1st to 10th	Day	13% 5% 15% 31% 24% 12%	526
	11th to 20th	Day	16% 5% 13% 28% 25% 13%	519
	21st to end	Day	9% 3 16% 31% 28% 14%	583
September	1st to 10th	Day	15% 5% 15% 25% 27% 14%	530
	11th to 20th	Day	12% 2 12% 28% 31% 15%	530
	21st to end	Day	25% 7% 21% 23% 18% 6%	530
October	1st to 10th	Day	14% 6% 25% 24% 22% 8%	530
	11th to 20th	Day	17% 12% 26% 26% 14% 5%	530
	21st to end	Day	26% 11% 28% 23% 10% 2	583
November	1st to 10th	Day	18% 14% 31% 25% 10% 2	385
	11th to 20th	Day	28% 15% 31% 18% 8% 1	330
	21st to end	Day	27% 18% 30% 21% 5%	330
December	1st to 10th	Day	31% 18% 32% 13% 5% 1	330
	11th to 20th	Day	32% 17% 30% 17% 3 1	330
	21st to end	Day	33% 16% 31% 14% 5% 1	363
January	1st to 10th	Night	28% 16% 29% 22% 5%	840
	11th to 20th	Night	33% 15% 29% 20% 3	840
	21st to end	Night	26% 16% 32% 22% 3	924
February	1st to 10th	Night	30% 10% 30% 29% 2	840
	11th to 20th	Night	32% 15% 30% 21% 1	823
	21st to end	Night	30% 14% 33% 21% 2	692
March	1st to 10th	Night	27% 13% 27% 28% 5%	840
	11th to 20th	Night	25% 15% 31% 21% 7% 1	840
	21st to end	Night	23% 12% 32% 26% 6%	924
April	1st to 10th	Night	23% 13% 31% 26% 6%	840
	11th to 20th	Night	18% 10% 29% 30% 12% 1	707
	21st to end	Night	20% 7% 33% 31% 9%	630
May	1st to 10th	Night	20% 8% 27% 32% 12% 1	630
	11th to 20th	Night	18% 7% 24% 34% 16% 1	621
	21st to end	Night	16% 4 17% 33% 28% 2	683
June	1st to 10th	Night	12% 2 17% 40% 26% 3	600
	11th to 20th	Night	9% 3 16% 40% 28% 4	600
	21st to end	Night	11% 3 15% 37% 31% 3	600
July	1st to 10th	Night	11% 3 11% 37% 32% 6%	585
	11th to 20th	Night	9% 3 12% 36% 36% 4	582
	21st to end	Night	11% 2 12% 34% 37% 5%	657
August	1st to 10th	Night	13% 3 9% 38% 33% 4	597
	11th to 20th	Night	11% 3 10% 33% 36% 7%	594
	21st to end	Night	10% 2 10% 35% 37% 7%	704
September	1st to 10th	Night	14% 2 9% 34% 36% 5%	800
	11th to 20th	Night	13% 2 13% 32% 35% 5%	800
	21st to end	Night	18% 6% 16% 34% 23% 3	800
October	1st to 10th	Night	14% 4 18% 32% 28% 3	800
	11th to 20th	Night	16% 8% 26% 32% 17% 2	800
	21st to end	Night	22% 9% 22% 33% 13% 1	880
November	1st to 10th	Night	15% 7% 26% 34% 16% 1	820
	11th to 20th	Night	23% 12% 25% 29% 10%	840
	21st to end	Night	25% 11% 21% 35% 7% 1	840
December	1st to 10th	Night	31% 12% 26% 26% 5%	840
	11th to 20th	Night	27% 12% 27% 28% 5%	840
	21st to end	Night	29% 14% 25% 28% 4	924

Page generated at 2026-05-29 01:53:27. Version ac07

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