Highwinds Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highwinds Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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% 10% 4 9% 6% 5% 5% 4 6% 7% 30%	101879
	Night	14% 11% 4 9% 6% 5% 5% 4 5% 7% 31%	98230
Transparency	Day	50% 8% 12% 19% 9% 1	105453
	Night	51% 8% 13% 19% 9% 1	102744
Seeing	Day	21% 18% 30% 19% 9% 3	14753
	Night	20% 17% 29% 24% 9% 1	24113

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	12% 23% 8% 12% 7% 5% 4 3 4 4 20%	2517
	11th to 20th	Day	11% 19% 8% 17% 8% 5% 5% 4 4 5% 15%	2594
	21st to end	Day	14% 18% 10% 13% 11% 6% 5% 3 4 5% 12%	3124
February	1st to 10th	Day	15% 17% 6% 12% 8% 5% 5% 3 5% 4 19%	1710
	11th to 20th	Day	11% 15% 8% 16% 9% 5% 5% 3 4 5% 19%	1663
	21st to end	Day	18% 14% 4 13% 9% 4 4 3 4 5% 23%	1559
March	1st to 10th	Day	18% 13% 5% 11% 5% 4 4 2 4 6% 28%	3294
	11th to 20th	Day	8% 16% 5% 11% 6% 5% 5% 3 5% 6% 30%	3480
	21st to end	Day	13% 12% 4 12% 6% 5% 4 4 5% 6% 29%	3910
April	1st to 10th	Day	15% 15% 4 8% 6% 5% 4 3 5% 7% 28%	2280
	11th to 20th	Day	16% 11% 4 8% 4 5% 4 3 5% 5% 34%	2254
	21st to end	Day	18% 11% 4 8% 4 5% 4 3 5% 6% 32%	2359
May	1st to 10th	Day	19% 9% 3 8% 5% 4 5% 4 5% 6% 33%	4258
	11th to 20th	Day	14% 9% 4 9% 6% 6% 5% 5% 6% 8% 29%	4398
	21st to end	Day	10% 6% 3 6% 5% 6% 5% 4 6% 8% 42%	4837
June	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 7% 8% 34%	2660
	11th to 20th	Day	12% 5% 3 7% 5% 5% 5% 5% 7% 10% 35%	2660
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 4 7% 9% 37%	2660
July	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 5% 8% 11% 36%	4440
	11th to 20th	Day	7% 5% 2 6% 5% 5% 7% 6% 9% 12% 35%	4440
	21st to end	Day	8% 5% 3 8% 6% 6% 6% 6% 8% 9% 36%	4701
August	1st to 10th	Day	16% 6% 3 7% 5% 5% 6% 4 7% 8% 34%	4104
	11th to 20th	Day	12% 7% 3 7% 6% 6% 7% 5% 8% 9% 28%	3994
	21st to end	Day	11% 6% 2 9% 6% 5% 5% 4 6% 9% 37%	4180
September	1st to 10th	Day	15% 7% 2 6% 5% 4 5% 5% 5% 9% 38%	2280
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 4 5% 6% 45%	2280
	21st to end	Day	17% 7% 3 8% 6% 5% 5% 4 7% 7% 33%	1999
October	1st to 10th	Day	18% 7% 3 8% 5% 4 5% 4 6% 7% 34%	1900
	11th to 20th	Day	18% 10% 3 8% 5% 5% 5% 3 6% 6% 31%	1900
	21st to end	Day	21% 12% 4 8% 5% 4 4 4 5% 6% 26%	2066
November	1st to 10th	Day	12% 11% 3 9% 6% 5% 6% 4 5% 5% 34%	1761
	11th to 20th	Day	12% 14% 5% 9% 6% 6% 6% 4 6% 7% 26%	1635
	21st to end	Day	15% 16% 4 10% 7% 5% 5% 4 5% 6% 22%	1600
December	1st to 10th	Day	15% 19% 6% 14% 7% 4 5% 4 6% 4 17%	1600
	11th to 20th	Day	17% 17% 6% 12% 6% 5% 4 4 6% 5% 19%	1986
	21st to end	Day	21% 21% 6% 13% 6% 5% 4 3 4 5% 13%	2796
January	1st to 10th	Night	15% 16% 6% 14% 7% 5% 5% 3 5% 5% 17%	4429
	11th to 20th	Night	10% 18% 8% 15% 10% 6% 5% 3 5% 5% 16%	4362
	21st to end	Night	18% 16% 6% 15% 9% 5% 4 3 4 4 15%	4532
February	1st to 10th	Night	13% 17% 5% 12% 7% 4 5% 4 6% 5% 21%	2470
	11th to 20th	Night	10% 13% 6% 15% 8% 7% 6% 4 5% 5% 21%	2403
	21st to end	Night	14% 11% 4 14% 6% 6% 5% 4 6% 6% 23%	1894
March	1st to 10th	Night	16% 11% 4 9% 6% 5% 5% 4 5% 5% 30%	3542
	11th to 20th	Night	12% 16% 6% 9% 6% 5% 5% 4 5% 6% 26%	3479
	21st to end	Night	15% 11% 3 10% 6% 4 5% 4 5% 6% 31%	3708
April	1st to 10th	Night	16% 11% 4 7% 4 5% 5% 4 6% 7% 31%	1900
	11th to 20th	Night	17% 10% 4 8% 5% 4 3 3 5% 6% 35%	1875
	21st to end	Night	16% 7% 3 8% 4 4 4 4 5% 7% 37%	1838
May	1st to 10th	Night	20% 9% 3 6% 5% 5% 5% 4 5% 7% 30%	2681
	11th to 20th	Night	14% 9% 3 8% 5% 4 4 4 7% 8% 34%	2495
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 6% 9% 43%	2738
June	1st to 10th	Night	14% 6% 3 7% 5% 4 5% 3 6% 10% 38%	1520
	11th to 20th	Night	9% 6% 3 7% 5% 4 4 5% 7% 8% 43%	1520
	21st to end	Night	9% 5% 2 7% 5% 5% 5% 6% 5% 9% 42%	1520
July	1st to 10th	Night	6% 7% 3 8% 6% 5% 5% 4 6% 10% 41%	2520
	11th to 20th	Night	8% 4 2 5% 4 4 5% 5% 7% 9% 48%	2520
	21st to end	Night	11% 5% 2 6% 4 5% 5% 5% 6% 9% 43%	2849
August	1st to 10th	Night	15% 6% 2 6% 4 4 4 4 7% 8% 39%	2825
	11th to 20th	Night	13% 7% 2 7% 4 5% 4 4 5% 7% 41%	2802
	21st to end	Night	8% 4 2 6% 5% 5% 5% 4 7% 9% 45%	3476
September	1st to 10th	Night	13% 5% 2 5% 4 5% 4 4 6% 7% 46%	1900
	11th to 20th	Night	13% 4 2 6% 5% 4 3 4 6% 6% 46%	1900
	21st to end	Night	15% 8% 3 6% 4 4 6% 4 6% 7% 37%	2178
October	1st to 10th	Night	15% 7% 3 8% 5% 5% 4 3 6% 7% 37%	2280
	11th to 20th	Night	17% 8% 2 7% 5% 4 4 3 6% 8% 35%	2280
	21st to end	Night	23% 10% 3 8% 4 4 4 3 5% 6% 29%	2531
November	1st to 10th	Night	13% 11% 3 7% 5% 4 5% 4 5% 6% 37%	2537
	11th to 20th	Night	14% 12% 3 9% 5% 5% 5% 4 6% 7% 30%	2765
	21st to end	Night	14% 14% 5% 9% 6% 6% 6% 4 6% 8% 24%	2800
December	1st to 10th	Night	14% 16% 6% 11% 7% 6% 5% 4 6% 6% 18%	2800
	11th to 20th	Night	16% 16% 5% 12% 6% 5% 4 4 4 5% 23%	3428
	21st to end	Night	23% 18% 6% 10% 6% 4 4 3 5% 6% 13%	4933

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% 6% 8% 13% 4	2518
	11th to 20th	Day	71% 7% 8% 10% 4	2594
	21st to end	Day	74% 7% 10% 7% 2	3124
February	1st to 10th	Day	68% 7% 9% 11% 4	1710
	11th to 20th	Day	68% 5% 8% 14% 5%	1672
	21st to end	Day	63% 6% 10% 14% 6% 1	1559
March	1st to 10th	Day	58% 6% 10% 19% 6%	3297
	11th to 20th	Day	52% 8% 15% 16% 8% 1	3480
	21st to end	Day	54% 8% 7% 23% 7% 1	3910
April	1st to 10th	Day	55% 6% 10% 18% 9% 2	2280
	11th to 20th	Day	51% 7% 9% 18% 13% 1	2254
	21st to end	Day	52% 6% 9% 18% 13% 2	2359
May	1st to 10th	Day	50% 7% 11% 19% 12% 2	4270
	11th to 20th	Day	50% 11% 12% 19% 7% 1	4402
	21st to end	Day	38% 10% 12% 24% 14% 2	4837
June	1st to 10th	Day	46% 9% 12% 19% 14% 1	2660
	11th to 20th	Day	42% 10% 15% 22% 11% 1	2660
	21st to end	Day	42% 9% 15% 21% 13% 1	2660
July	1st to 10th	Day	38% 9% 15% 26% 10% 1	4370
	11th to 20th	Day	34% 11% 18% 23% 13%	4365
	21st to end	Day	40% 12% 15% 21% 11% 1	4551
August	1st to 10th	Day	46% 8% 14% 20% 11% 1	4091
	11th to 20th	Day	46% 10% 16% 22% 5%	4033
	21st to end	Day	42% 8% 11% 30% 8% 1	4180
September	1st to 10th	Day	42% 9% 11% 25% 12% 1	2280
	11th to 20th	Day	39% 6% 13% 25% 16% 1	2280
	21st to end	Day	49% 9% 11% 20% 11% 1	1999
October	1st to 10th	Day	39% 8% 14% 24% 14% 1	3160
	11th to 20th	Day	46% 7% 13% 17% 16%	3140
	21st to end	Day	43% 8% 14% 26% 8% 1	3380
November	1st to 10th	Day	50% 9% 12% 17% 10% 2	1761
	11th to 20th	Day	56% 8% 12% 15% 7% 2	1635
	21st to end	Day	62% 8% 13% 14% 3	1600
December	1st to 10th	Day	70% 8% 10% 10% 3	1600
	11th to 20th	Day	66% 7% 14% 10% 3 1	1986
	21st to end	Day	73% 7% 10% 8% 1	2796
January	1st to 10th	Night	66% 9% 12% 9% 4	4429
	11th to 20th	Night	68% 9% 10% 11% 3	4362
	21st to end	Night	74% 6% 7% 10% 2	4532
February	1st to 10th	Night	63% 7% 12% 12% 5%	2470
	11th to 20th	Night	62% 8% 11% 14% 5% 1	2405
	21st to end	Night	60% 8% 11% 13% 8% 1	1894
March	1st to 10th	Night	54% 8% 13% 17% 6% 1	3552
	11th to 20th	Night	56% 10% 12% 16% 6%	3480
	21st to end	Night	50% 8% 11% 20% 9% 2	3708
April	1st to 10th	Night	52% 8% 11% 18% 10% 1	1900
	11th to 20th	Night	49% 7% 11% 18% 13% 1	1875
	21st to end	Night	46% 8% 11% 19% 13% 2	1838
May	1st to 10th	Night	52% 8% 12% 18% 9% 2	2688
	11th to 20th	Night	46% 11% 16% 18% 8% 1	2496
	21st to end	Night	34% 11% 16% 20% 16% 3	2739
June	1st to 10th	Night	41% 7% 13% 24% 14% 1	1520
	11th to 20th	Night	36% 9% 16% 24% 13% 3	1520
	21st to end	Night	36% 11% 13% 25% 14% 1	1520
July	1st to 10th	Night	38% 9% 15% 22% 14% 2	2480
	11th to 20th	Night	30% 10% 16% 31% 13% 1	2472
	21st to end	Night	37% 9% 14% 24% 15% 2	2758
August	1st to 10th	Night	41% 8% 15% 25% 9% 1	2814
	11th to 20th	Night	41% 8% 15% 28% 8%	2829
	21st to end	Night	32% 10% 16% 32% 10% 1	3476
September	1st to 10th	Night	36% 8% 17% 25% 12% 2	1900
	11th to 20th	Night	35% 7% 14% 27% 16% 1	1900
	21st to end	Night	44% 8% 14% 21% 12% 1	2178
October	1st to 10th	Night	42% 9% 12% 24% 13%	3800
	11th to 20th	Night	40% 7% 14% 21% 14% 4	3779
	21st to end	Night	41% 7% 16% 27% 9% 1	4167
November	1st to 10th	Night	46% 8% 12% 21% 11% 2	2537
	11th to 20th	Night	51% 9% 13% 18% 8% 2	2765
	21st to end	Night	57% 10% 15% 15% 4	2800
December	1st to 10th	Night	66% 9% 14% 10% 2	2800
	11th to 20th	Night	65% 8% 10% 13% 4	3428
	21st to end	Night	72% 8% 10% 10% 2	4933

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	25% 27% 33% 11% 4	180
	11th to 20th	Day	29% 33% 31% 5% 1	203
	21st to end	Day	20% 30% 37% 10% 2	297
February	1st to 10th	Day	33% 31% 27% 9%	270
	11th to 20th	Day	33% 30% 33% 4	270
	21st to end	Day	35% 23% 32% 10% 1	371
March	1st to 10th	Day	27% 27% 29% 14% 3 1	460
	11th to 20th	Day	27% 25% 32% 12% 4	460
	21st to end	Day	31% 23% 29% 13% 4 1	506
April	1st to 10th	Day	27% 25% 30% 13% 4 1	460
	11th to 20th	Day	28% 25% 26% 12% 7% 2	452
	21st to end	Day	27% 20% 30% 16% 6% 1	460
May	1st to 10th	Day	25% 21% 28% 15% 8% 3	463
	11th to 20th	Day	18% 17% 32% 22% 10% 2	487
	21st to end	Day	15% 14% 31% 24% 13% 3	529
June	1st to 10th	Day	18% 17% 30% 23% 10% 3	490
	11th to 20th	Day	13% 14% 32% 28% 12% 2	490
	21st to end	Day	13% 16% 35% 24% 8% 3	490
July	1st to 10th	Day	10% 8% 31% 32% 15% 4	485
	11th to 20th	Day	10% 9% 27% 32% 17% 5%	484
	21st to end	Day	11% 8% 39% 27% 12% 3	532
August	1st to 10th	Day	10% 9% 28% 29% 17% 7%	486
	11th to 20th	Day	13% 8% 30% 27% 14% 8%	479
	21st to end	Day	13% 10% 28% 24% 17% 8%	539
September	1st to 10th	Day	18% 11% 25% 23% 15% 8%	490
	11th to 20th	Day	11% 9% 23% 25% 21% 10%	490
	21st to end	Day	19% 16% 28% 20% 13% 4	490
October	1st to 10th	Day	20% 15% 28% 20% 12% 4	490
	11th to 20th	Day	23% 19% 31% 19% 7% 2	490
	21st to end	Day	26% 22% 32% 16% 3	526
November	1st to 10th	Day	20% 25% 29% 17% 8% 1	395
	11th to 20th	Day	26% 26% 29% 15% 2	235
	21st to end	Day	28% 31% 32% 10% 1	200
December	1st to 10th	Day	31% 25% 33% 9% 3 1	200
	11th to 20th	Day	33% 29% 29% 9% 1 1	200
	21st to end	Day	25% 28% 38% 7% 1	204
January	1st to 10th	Night	23% 27% 34% 14% 2	760
	11th to 20th	Night	23% 25% 30% 18% 3 1	760
	21st to end	Night	18% 26% 36% 18% 2	836
February	1st to 10th	Night	25% 25% 32% 18% 1	760
	11th to 20th	Night	23% 29% 32% 14% 2	743
	21st to end	Night	28% 24% 29% 16% 3	628
March	1st to 10th	Night	22% 24% 33% 18% 3	760
	11th to 20th	Night	26% 24% 27% 20% 3	760
	21st to end	Night	24% 21% 30% 19% 6%	836
April	1st to 10th	Night	24% 22% 30% 22% 2	760
	11th to 20th	Night	23% 18% 31% 20% 6% 1	751
	21st to end	Night	20% 13% 33% 26% 8%	698
May	1st to 10th	Night	19% 13% 24% 32% 11% 1	483
	11th to 20th	Night	15% 9% 33% 32% 10% 1	374
	21st to end	Night	11% 9% 29% 34% 17%	411
June	1st to 10th	Night	15% 8% 28% 33% 15% 1	380
	11th to 20th	Night	11% 10% 27% 35% 16%	380
	21st to end	Night	12% 7% 28% 42% 10% 1	380
July	1st to 10th	Night	8% 4 22% 45% 19% 2	370
	11th to 20th	Night	11% 2 22% 42% 22% 2	368
	21st to end	Night	11% 3 25% 41% 18% 2	477
August	1st to 10th	Night	11% 4 22% 37% 25% 2	567
	11th to 20th	Night	11% 6% 22% 32% 26% 3	568
	21st to end	Night	11% 6% 23% 35% 23% 2	836
September	1st to 10th	Night	15% 8% 24% 31% 18% 3	760
	11th to 20th	Night	14% 9% 19% 28% 26% 4	760
	21st to end	Night	18% 12% 25% 25% 16% 3	760
October	1st to 10th	Night	19% 13% 28% 21% 17% 2	760
	11th to 20th	Night	23% 17% 29% 24% 7% 1	760
	21st to end	Night	29% 16% 32% 19% 3	836
November	1st to 10th	Night	22% 17% 31% 22% 8%	780
	11th to 20th	Night	23% 22% 32% 16% 5% 2	800
	21st to end	Night	22% 24% 30% 19% 4	800
December	1st to 10th	Night	25% 25% 31% 16% 3	800
	11th to 20th	Night	25% 24% 31% 17% 3	800
	21st to end	Night	26% 25% 34% 14% 1	851

Page generated at 2024-12-21 04:13:52. Version ac07

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