Highlands Wilderness Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highlands Wilderness Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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	17% 11% 4 8% 5% 4 4 4 5% 7% 32%	101777
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	97225
Transparency	Day	51% 6% 11% 21% 10% 1	105375
	Night	52% 6% 11% 20% 10% 1	101715
Seeing	Day	24% 14% 31% 19% 9% 3	14603
	Night	24% 12% 29% 24% 10% 1	23654

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	17% 20% 8% 14% 5% 4 3 2 3 3 22%	2517
	11th to 20th	Day	12% 18% 8% 17% 9% 6% 5% 3 3 3 14%	2588
	21st to end	Day	19% 21% 9% 12% 5% 4 3 2 3 3 18%	3124
February	1st to 10th	Day	14% 17% 7% 16% 7% 5% 4 3 4 4 20%	1710
	11th to 20th	Day	14% 15% 6% 14% 7% 4 4 3 4 4 25%	1663
	21st to end	Day	16% 17% 6% 11% 5% 6% 4 4 5% 4 22%	1455
March	1st to 10th	Day	20% 16% 4 8% 5% 4 4 3 4 6% 26%	3397
	11th to 20th	Day	12% 18% 7% 9% 5% 5% 4 4 4 5% 25%	3480
	21st to end	Day	15% 10% 3 7% 4 4 3 3 4 5% 41%	3832
April	1st to 10th	Day	21% 15% 4 6% 4 4 4 3 5% 6% 28%	2280
	11th to 20th	Day	23% 11% 3 6% 4 3 4 2 4 4 36%	2301
	21st to end	Day	23% 11% 4 6% 4 4 4 3 4 5% 33%	2470
May	1st to 10th	Day	20% 8% 3 7% 5% 5% 4 4 5% 6% 33%	4233
	11th to 20th	Day	16% 10% 2 7% 5% 5% 5% 4 6% 8% 34%	4398
	21st to end	Day	16% 6% 2 6% 4 4 4 4 5% 7% 41%	4837
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 5% 8% 32%	2660
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 9% 36%	2660
	21st to end	Day	18% 7% 2 7% 5% 5% 4 4 6% 7% 35%	2832
July	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 11% 36%	4509
	11th to 20th	Day	12% 6% 2 5% 4 5% 5% 4 6% 8% 43%	4440
	21st to end	Day	9% 6% 2 6% 5% 4 5% 5% 7% 9% 44%	4700
August	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 6% 8% 34%	4104
	11th to 20th	Day	16% 7% 3 6% 5% 4 5% 4 7% 9% 34%	4044
	21st to end	Day	10% 5% 2 6% 5% 4 5% 4 7% 10% 42%	4322
September	1st to 10th	Day	15% 7% 2 7% 5% 4 4 3 5% 8% 39%	2280
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 46%	2228
	21st to end	Day	18% 8% 3 7% 4 4 5% 3 5% 6% 37%	2014
October	1st to 10th	Day	20% 10% 2 8% 5% 4 4 3 4 7% 32%	1900
	11th to 20th	Day	25% 11% 3 8% 5% 4 5% 4 5% 6% 24%	1900
	21st to end	Day	28% 13% 4 8% 5% 4 4 2 4 6% 22%	2090
November	1st to 10th	Day	17% 12% 4 7% 5% 5% 4 3 5% 6% 32%	1571
	11th to 20th	Day	18% 15% 4 10% 5% 5% 4 4 6% 6% 23%	1520
	21st to end	Day	22% 20% 5% 10% 5% 4 4 3 4 5% 18%	1520
December	1st to 10th	Day	19% 25% 8% 11% 4 3 3 4 4 3 15%	1520
	11th to 20th	Day	19% 18% 5% 11% 5% 4 4 3 4 3 23%	1906
	21st to end	Day	26% 22% 6% 12% 4 3 3 2 4 4 16%	2772
January	1st to 10th	Night	19% 20% 9% 14% 6% 4 3 2 4 4 15%	4429
	11th to 20th	Night	14% 15% 7% 19% 8% 6% 5% 3 4 4 16%	4368
	21st to end	Night	18% 18% 9% 12% 6% 6% 4 3 5% 4 17%	4532
February	1st to 10th	Night	14% 17% 6% 13% 8% 6% 5% 4 5% 5% 19%	2470
	11th to 20th	Night	13% 16% 7% 11% 6% 6% 5% 3 4 5% 26%	2403
	21st to end	Night	15% 16% 5% 10% 7% 5% 4 3 5% 5% 26%	1998
March	1st to 10th	Night	18% 13% 4 10% 5% 4 4 3 4 5% 29%	3441
	11th to 20th	Night	13% 18% 8% 8% 5% 4 4 3 5% 5% 27%	3479
	21st to end	Night	15% 9% 3 8% 5% 4 4 4 6% 7% 36%	3800
April	1st to 10th	Night	21% 13% 3 8% 4 5% 4 2 5% 5% 29%	1900
	11th to 20th	Night	18% 10% 3 7% 4 3 3 3 5% 6% 36%	1844
	21st to end	Night	19% 10% 3 9% 4 4 4 4 5% 5% 33%	1710
May	1st to 10th	Night	20% 6% 3 7% 5% 4 5% 3 5% 6% 38%	2706
	11th to 20th	Night	17% 7% 2 7% 5% 5% 4 3 6% 7% 38%	2495
	21st to end	Night	13% 7% 2 5% 4 5% 4 3 5% 8% 44%	2738
June	1st to 10th	Night	16% 8% 2 6% 5% 4 5% 4 7% 8% 36%	1520
	11th to 20th	Night	12% 7% 2 5% 4 5% 5% 4 6% 8% 44%	1520
	21st to end	Night	16% 7% 3 6% 4 5% 5% 4 5% 7% 38%	1336
July	1st to 10th	Night	10% 5% 2 7% 5% 5% 5% 4 7% 7% 44%	2444
	11th to 20th	Night	15% 6% 1 5% 4 3 4 3 5% 7% 47%	2520
	21st to end	Night	10% 6% 2 5% 3 4 4 4 6% 7% 49%	2850
August	1st to 10th	Night	12% 5% 2 5% 4 3 4 4 6% 7% 47%	2825
	11th to 20th	Night	15% 6% 3 6% 4 4 4 3 5% 7% 43%	2785
	21st to end	Night	14% 5% 1 5% 4 3 4 3 5% 6% 49%	3302
September	1st to 10th	Night	13% 6% 2 6% 5% 3 4 4 6% 7% 45%	1900
	11th to 20th	Night	13% 6% 2 4 4 3 3 3 5% 7% 50%	1949
	21st to end	Night	18% 8% 2 6% 4 5% 3 3 5% 5% 41%	2165
October	1st to 10th	Night	18% 8% 2 7% 5% 4 4 3 5% 6% 37%	2280
	11th to 20th	Night	23% 12% 3 7% 5% 4 4 3 5% 6% 28%	2280
	21st to end	Night	23% 13% 4 9% 5% 4 4 3 5% 5% 26%	2508
November	1st to 10th	Night	20% 11% 3 6% 5% 4 4 3 4 6% 34%	2576
	11th to 20th	Night	18% 15% 4 7% 6% 4 4 3 5% 6% 27%	2660
	21st to end	Night	22% 15% 5% 9% 6% 6% 5% 3 5% 6% 19%	2660
December	1st to 10th	Night	21% 22% 5% 11% 5% 4 4 3 4 5% 15%	2660
	11th to 20th	Night	18% 21% 6% 11% 5% 4 3 3 4 5% 21%	3288
	21st to end	Night	27% 21% 7% 12% 4 4 3 2 3 4 12%	4884

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	67% 7% 9% 10% 7% 1	2518
	11th to 20th	Day	72% 8% 7% 7% 6% 1	2588
	21st to end	Day	72% 4 7% 10% 6% 1	3124
February	1st to 10th	Day	70% 3 7% 15% 4 1	1710
	11th to 20th	Day	62% 5% 8% 14% 10% 1	1672
	21st to end	Day	64% 4 9% 13% 9% 1	1455
March	1st to 10th	Day	59% 5% 12% 12% 10% 1	3400
	11th to 20th	Day	59% 6% 10% 16% 8% 1	3480
	21st to end	Day	45% 5% 8% 22% 17% 3	3832
April	1st to 10th	Day	57% 4 7% 19% 11% 2	2280
	11th to 20th	Day	52% 5% 7% 21% 15% 1	2301
	21st to end	Day	54% 4 7% 20% 11% 3	2470
May	1st to 10th	Day	50% 6% 8% 23% 12% 1	4245
	11th to 20th	Day	47% 8% 11% 23% 10% 1	4402
	21st to end	Day	41% 6% 13% 21% 16% 3	4837
June	1st to 10th	Day	50% 6% 9% 21% 13%	2660
	11th to 20th	Day	43% 6% 11% 25% 14% 2	2660
	21st to end	Day	47% 6% 12% 22% 11% 1	2832
July	1st to 10th	Day	39% 7% 16% 25% 12% 1	4439
	11th to 20th	Day	37% 6% 15% 33% 9%	4365
	21st to end	Day	36% 7% 12% 33% 12%	4550
August	1st to 10th	Day	46% 7% 12% 25% 9% 1	4091
	11th to 20th	Day	44% 8% 13% 27% 8%	4083
	21st to end	Day	35% 7% 12% 35% 11% 1	4322
September	1st to 10th	Day	43% 5% 13% 28% 11% 1	2280
	11th to 20th	Day	37% 5% 13% 31% 13% 1	2228
	21st to end	Day	48% 5% 12% 24% 11%	2014
October	1st to 10th	Day	46% 5% 11% 28% 10% 1	3160
	11th to 20th	Day	51% 6% 12% 20% 10% 1	3140
	21st to end	Day	58% 6% 12% 19% 5%	3428
November	1st to 10th	Day	52% 6% 13% 20% 7% 1	1571
	11th to 20th	Day	59% 6% 12% 14% 7% 2	1520
	21st to end	Day	68% 6% 10% 10% 5% 1	1520
December	1st to 10th	Day	74% 4 8% 10% 4 1	1520
	11th to 20th	Day	67% 6% 8% 11% 8% 1	1906
	21st to end	Day	74% 4 6% 12% 4	2772
January	1st to 10th	Night	73% 5% 8% 10% 4	4429
	11th to 20th	Night	70% 8% 8% 8% 4 1	4368
	21st to end	Night	69% 6% 9% 9% 6% 1	4532
February	1st to 10th	Night	66% 5% 7% 15% 5% 1	2470
	11th to 20th	Night	60% 5% 8% 18% 8%	2405
	21st to end	Night	59% 4 9% 18% 8%	1998
March	1st to 10th	Night	56% 5% 9% 18% 11% 1	3451
	11th to 20th	Night	57% 6% 12% 16% 7% 1	3480
	21st to end	Night	44% 7% 9% 23% 16% 2	3800
April	1st to 10th	Night	56% 5% 7% 19% 11% 2	1900
	11th to 20th	Night	49% 5% 7% 22% 16% 1	1844
	21st to end	Night	51% 6% 9% 15% 16% 2	1710
May	1st to 10th	Night	47% 5% 11% 20% 15% 2	2713
	11th to 20th	Night	43% 8% 12% 24% 11% 2	2496
	21st to end	Night	37% 7% 11% 25% 18% 2	2739
June	1st to 10th	Night	44% 6% 10% 23% 15% 2	1520
	11th to 20th	Night	38% 6% 11% 24% 19% 2	1520
	21st to end	Night	44% 7% 13% 22% 13% 1	1336
July	1st to 10th	Night	36% 6% 15% 25% 16% 1	2404
	11th to 20th	Night	36% 6% 11% 33% 14%	2472
	21st to end	Night	33% 6% 13% 33% 15% 1	2759
August	1st to 10th	Night	35% 5% 16% 26% 17% 1	2814
	11th to 20th	Night	39% 7% 18% 24% 12% 1	2812
	21st to end	Night	35% 5% 12% 34% 12% 2	3302
September	1st to 10th	Night	37% 6% 15% 27% 13% 1	1900
	11th to 20th	Night	34% 5% 13% 34% 14% 1	1949
	21st to end	Night	45% 5% 10% 29% 11%	2165
October	1st to 10th	Night	38% 5% 10% 28% 19%	3800
	11th to 20th	Night	48% 6% 13% 24% 9%	3779
	21st to end	Night	52% 6% 14% 21% 7%	4120
November	1st to 10th	Night	51% 5% 12% 22% 9% 1	2576
	11th to 20th	Night	57% 5% 13% 15% 8% 1	2660
	21st to end	Night	64% 6% 13% 12% 5%	2660
December	1st to 10th	Night	72% 4 8% 11% 5%	2660
	11th to 20th	Night	66% 4 11% 13% 6%	3288
	21st to end	Night	77% 4 6% 9% 4	4884

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% 21% 33% 13% 6% 2	180
	11th to 20th	Day	27% 23% 32% 14% 3 2	200
	21st to end	Day	27% 13% 40% 14% 4 1	297
February	1st to 10th	Day	28% 26% 34% 9% 3	270
	11th to 20th	Day	27% 26% 40% 6% 1	270
	21st to end	Day	38% 21% 30% 11%	267
March	1st to 10th	Day	26% 18% 36% 16% 2	460
	11th to 20th	Day	29% 17% 34% 16% 3 1	460
	21st to end	Day	34% 16% 32% 13% 5%	506
April	1st to 10th	Day	30% 20% 29% 15% 5% 1	460
	11th to 20th	Day	38% 16% 21% 15% 7% 3	452
	21st to end	Day	31% 15% 32% 12% 8% 1	460
May	1st to 10th	Day	28% 13% 28% 20% 6% 5%	463
	11th to 20th	Day	21% 13% 33% 19% 11% 3	487
	21st to end	Day	19% 13% 32% 20% 10% 5%	529
June	1st to 10th	Day	24% 10% 33% 25% 7% 2	490
	11th to 20th	Day	17% 12% 32% 26% 10% 4	490
	21st to end	Day	22% 11% 32% 24% 9% 2	662
July	1st to 10th	Day	11% 9% 34% 27% 14% 5%	528
	11th to 20th	Day	17% 7% 28% 28% 14% 6%	484
	21st to end	Day	12% 10% 33% 28% 11% 6%	532
August	1st to 10th	Day	16% 5% 30% 27% 15% 6%	486
	11th to 20th	Day	15% 7% 24% 27% 19% 7%	479
	21st to end	Day	15% 10% 31% 23% 14% 7%	539
September	1st to 10th	Day	16% 11% 29% 23% 14% 6%	490
	11th to 20th	Day	13% 7% 24% 23% 21% 12%	490
	21st to end	Day	22% 13% 24% 24% 11% 5%	490
October	1st to 10th	Day	25% 14% 26% 17% 16% 3	490
	11th to 20th	Day	27% 18% 33% 16% 5% 1	490
	21st to end	Day	35% 16% 30% 16% 4	539
November	1st to 10th	Day	27% 18% 31% 18% 5%	245
	11th to 20th	Day	31% 21% 29% 14% 2 2	180
	21st to end	Day	33% 15% 43% 7% 2 1	180
December	1st to 10th	Day	33% 17% 29% 18% 2	180
	11th to 20th	Day	37% 23% 23% 14% 3 1	180
	21st to end	Day	37% 19% 31% 10% 3	198
January	1st to 10th	Night	32% 18% 29% 16% 5%	760
	11th to 20th	Night	30% 14% 31% 18% 6% 1	760
	21st to end	Night	21% 13% 34% 24% 7% 1	836
February	1st to 10th	Night	25% 21% 33% 19% 2	760
	11th to 20th	Night	23% 19% 35% 19% 4	743
	21st to end	Night	28% 20% 30% 19% 4	628
March	1st to 10th	Night	25% 18% 35% 19% 3	760
	11th to 20th	Night	24% 16% 34% 19% 4 1	760
	21st to end	Night	23% 12% 33% 23% 9%	836
April	1st to 10th	Night	28% 15% 32% 20% 5%	760
	11th to 20th	Night	27% 13% 32% 19% 8% 1	720
	21st to end	Night	25% 10% 32% 23% 9%	570
May	1st to 10th	Night	23% 6% 28% 28% 13% 2	495
	11th to 20th	Night	18% 6% 35% 29% 11%	374
	21st to end	Night	15% 5% 32% 35% 13% 1	411
June	1st to 10th	Night	19% 5% 31% 34% 10% 1	380
	11th to 20th	Night	15% 9% 25% 38% 13%	380
	21st to end	Night	18% 7% 24% 36% 13% 1	380
July	1st to 10th	Night	10% 6% 25% 42% 17% 1	370
	11th to 20th	Night	14% 4 27% 32% 23% 1	368
	21st to end	Night	11% 3 25% 40% 20%	478
August	1st to 10th	Night	13% 4 19% 36% 26% 2	567
	11th to 20th	Night	11% 6% 17% 36% 27% 3	564
	21st to end	Night	15% 5% 27% 30% 21% 2	727
September	1st to 10th	Night	14% 8% 29% 29% 18% 4	760
	11th to 20th	Night	16% 4 23% 31% 23% 4	760
	21st to end	Night	23% 8% 20% 30% 16% 3	760
October	1st to 10th	Night	23% 10% 26% 25% 15% 1	760
	11th to 20th	Night	30% 13% 26% 22% 9% 1	760
	21st to end	Night	30% 13% 31% 21% 4	836
November	1st to 10th	Night	27% 12% 28% 24% 9% 1	755
	11th to 20th	Night	28% 15% 33% 17% 6% 1	760
	21st to end	Night	31% 13% 30% 21% 4 1	760
December	1st to 10th	Night	34% 18% 29% 14% 5%	760
	11th to 20th	Night	28% 18% 33% 17% 3 1	760
	21st to end	Night	35% 14% 31% 17% 3	836

Page generated at 2024-11-01 22:47:45. Version ac07

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