Hutville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hutville clear sky chart from 2005-11-06 to 2025-10-19.

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% 5% 5% 5% 4 5% 7% 32%	126843
	Night	14% 10% 4 9% 5% 5% 4 4 5% 7% 33%	122847
Transparency	Day	49% 6% 11% 21% 12% 1	130492
	Night	49% 6% 11% 21% 13% 2	127267
Seeing	Day	19% 12% 27% 22% 15% 6%	16339
	Night	18% 9% 28% 29% 14% 2	26176

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	14% 17% 9% 18% 8% 5% 4 3 4 4 13%	4056
	11th to 20th	Day	12% 20% 8% 14% 7% 7% 6% 3 3 4 15%	4060
	21st to end	Day	21% 16% 9% 11% 8% 6% 5% 3 4 4 13%	4466
February	1st to 10th	Day	18% 15% 6% 10% 7% 6% 3 3 4 4 24%	1800
	11th to 20th	Day	16% 12% 6% 15% 7% 4 4 3 5% 6% 23%	1898
	21st to end	Day	16% 16% 4 10% 6% 3 3 3 4 7% 28%	1650
March	1st to 10th	Day	16% 12% 7% 13% 5% 4 4 3 4 5% 26%	4724
	11th to 20th	Day	11% 9% 4 8% 5% 5% 4 3 5% 6% 40%	4980
	21st to end	Day	19% 10% 4 9% 5% 5% 4 3 5% 6% 31%	5465
April	1st to 10th	Day	15% 13% 3 8% 6% 4 5% 3 5% 6% 31%	2227
	11th to 20th	Day	15% 11% 3 7% 5% 5% 3 3 4 6% 36%	2546
	21st to end	Day	17% 9% 3 8% 5% 5% 4 4 6% 6% 33%	2600
May	1st to 10th	Day	22% 9% 3 8% 6% 5% 5% 4 5% 5% 28%	5862
	11th to 20th	Day	19% 9% 3 8% 5% 4 5% 4 5% 8% 32%	5861
	21st to end	Day	16% 7% 2 6% 5% 4 5% 5% 7% 8% 34%	6433
June	1st to 10th	Day	11% 6% 2 8% 6% 5% 5% 5% 7% 8% 37%	2600
	11th to 20th	Day	11% 6% 3 8% 5% 5% 5% 4 7% 9% 37%	2600
	21st to end	Day	10% 6% 2 6% 5% 6% 5% 5% 8% 10% 36%	2748
July	1st to 10th	Day	9% 6% 3 7% 6% 5% 5% 4 6% 9% 41%	6020
	11th to 20th	Day	10% 7% 2 7% 5% 6% 5% 5% 8% 11% 34%	5900
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 4 7% 9% 37%	6424
August	1st to 10th	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 10% 39%	4234
	11th to 20th	Day	8% 7% 2 7% 5% 6% 6% 6% 9% 10% 36%	4174
	21st to end	Day	6% 4 2 6% 5% 5% 7% 5% 7% 9% 44%	4632
September	1st to 10th	Day	12% 6% 2 5% 4 4 4 4 5% 7% 48%	2200
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 5% 9% 47%	2200
	21st to end	Day	19% 7% 2 6% 4 4 4 3 4 6% 42%	2200
October	1st to 10th	Day	13% 6% 3 6% 5% 4 4 4 5% 8% 44%	2125
	11th to 20th	Day	13% 8% 2 6% 4 4 4 3 6% 7% 42%	1980
	21st to end	Day	19% 10% 2 8% 4 4 4 3 5% 7% 33%	2047
November	1st to 10th	Day	11% 9% 2 5% 4 3 6% 4 5% 7% 45%	1762
	11th to 20th	Day	17% 11% 5% 7% 6% 5% 4 3 5% 5% 33%	1800
	21st to end	Day	17% 15% 5% 9% 5% 5% 3 3 4 6% 28%	1800
December	1st to 10th	Day	18% 13% 5% 15% 6% 5% 4 3 4 5% 22%	2930
	11th to 20th	Day	22% 15% 7% 12% 5% 4 4 3 4 4 20%	3373
	21st to end	Day	23% 22% 6% 11% 5% 5% 4 3 3 4 14%	4466
January	1st to 10th	Night	13% 18% 8% 19% 7% 5% 3 3 3 4 16%	5889
	11th to 20th	Night	12% 16% 8% 16% 8% 7% 6% 4 4 4 14%	5900
	21st to end	Night	19% 14% 7% 11% 6% 5% 4 3 4 5% 23%	6490
February	1st to 10th	Night	18% 13% 4 10% 6% 5% 4 3 6% 5% 26%	2600
	11th to 20th	Night	17% 12% 4 11% 7% 4 6% 3 5% 6% 25%	2385
	21st to end	Night	18% 13% 4 12% 6% 5% 3 3 4 6% 27%	1980
March	1st to 10th	Night	19% 12% 5% 7% 4 4 4 4 4 5% 33%	5127
	11th to 20th	Night	12% 7% 4 6% 4 4 4 4 6% 8% 41%	4980
	21st to end	Night	17% 10% 3 8% 5% 4 4 4 4 6% 36%	5467
April	1st to 10th	Night	16% 10% 3 6% 5% 4 5% 4 5% 7% 35%	2190
	11th to 20th	Night	13% 8% 3 7% 6% 5% 4 4 6% 6% 38%	1802
	21st to end	Night	14% 9% 3 7% 5% 4 4 4 5% 8% 38%	1800
May	1st to 10th	Night	23% 11% 3 8% 5% 5% 5% 4 4 6% 27%	4033
	11th to 20th	Night	16% 9% 3 7% 4 3 3 3 6% 10% 36%	4032
	21st to end	Night	13% 7% 3 6% 4 5% 5% 4 7% 9% 38%	4421
June	1st to 10th	Night	9% 6% 2 6% 5% 4 4 4 6% 8% 46%	1800
	11th to 20th	Night	9% 5% 2 6% 4 5% 5% 4 7% 10% 42%	1800
	21st to end	Night	9% 5% 2 5% 5% 5% 5% 5% 7% 10% 44%	1633
July	1st to 10th	Night	10% 6% 2 7% 4 4 5% 4 6% 8% 44%	3916
	11th to 20th	Night	8% 6% 2 7% 5% 5% 5% 5% 7% 10% 39%	4057
	21st to end	Night	7% 6% 2 8% 5% 5% 5% 4 7% 8% 42%	4427
August	1st to 10th	Night	8% 6% 2 8% 5% 5% 5% 5% 7% 9% 39%	2915
	11th to 20th	Night	8% 8% 3 8% 5% 4 4 3 5% 7% 45%	2875
	21st to end	Night	4 4 2 4 4 5% 6% 5% 8% 8% 50%	3244
September	1st to 10th	Night	10% 5% 2 5% 3 4 4 3 5% 7% 52%	2185
	11th to 20th	Night	8% 5% 2 5% 3 3 3 3 5% 8% 57%	2200
	21st to end	Night	16% 6% 2 6% 4 3 4 4 5% 5% 45%	2200
October	1st to 10th	Night	10% 5% 2 6% 4 4 3 3 6% 7% 50%	2275
	11th to 20th	Night	13% 8% 2 7% 3 5% 4 4 5% 6% 43%	2377
	21st to end	Night	20% 8% 2 7% 4 4 5% 4 4 6% 37%	2549
November	1st to 10th	Night	12% 8% 2 6% 4 3 4 3 5% 6% 46%	2536
	11th to 20th	Night	16% 10% 4 8% 5% 4 4 4 4 7% 34%	2600
	21st to end	Night	18% 14% 4 8% 5% 4 4 4 5% 6% 28%	2600
December	1st to 10th	Night	15% 12% 5% 11% 6% 6% 5% 4 5% 6% 25%	4250
	11th to 20th	Night	18% 16% 7% 12% 5% 4 3 3 5% 5% 21%	4822
	21st to end	Night	23% 20% 6% 11% 5% 4 3 3 4 5% 16%	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	74% 4 7% 11% 3	4057
	11th to 20th	Day	74% 3 8% 8% 7%	4060
	21st to end	Day	75% 4 7% 8% 5%	4466
February	1st to 10th	Day	64% 5% 9% 14% 7% 1	1800
	11th to 20th	Day	62% 5% 8% 16% 8% 1	1908
	21st to end	Day	58% 4 11% 19% 7% 2	1650
March	1st to 10th	Day	60% 4 7% 21% 6% 1	4724
	11th to 20th	Day	44% 5% 11% 28% 10% 2	4980
	21st to end	Day	54% 5% 10% 21% 10% 1	5465
April	1st to 10th	Day	53% 5% 12% 17% 11% 1	2227
	11th to 20th	Day	49% 6% 11% 18% 13% 2	2546
	21st to end	Day	50% 6% 10% 20% 12% 2	2600
May	1st to 10th	Day	56% 7% 10% 16% 10% 2	5897
	11th to 20th	Day	50% 6% 13% 21% 10% 1	5865
	21st to end	Day	43% 9% 12% 23% 11% 3	6447
June	1st to 10th	Day	42% 7% 11% 24% 15% 1	2600
	11th to 20th	Day	42% 9% 14% 21% 13% 1	2600
	21st to end	Day	40% 9% 14% 20% 14% 2	2748
July	1st to 10th	Day	39% 7% 10% 28% 14% 2	5955
	11th to 20th	Day	40% 9% 14% 23% 14% 1	5831
	21st to end	Day	40% 8% 12% 20% 18% 3	6240
August	1st to 10th	Day	38% 9% 15% 25% 13%	4221
	11th to 20th	Day	37% 9% 12% 27% 14% 1	4213
	21st to end	Day	32% 8% 15% 29% 12% 3	4632
September	1st to 10th	Day	35% 6% 11% 23% 21% 4	2200
	11th to 20th	Day	34% 6% 11% 26% 20% 3	2200
	21st to end	Day	44% 4 9% 21% 20% 1	2200
October	1st to 10th	Day	26% 5% 9% 34% 25% 1	3463
	11th to 20th	Day	35% 6% 10% 26% 20% 4	3220
	21st to end	Day	39% 4 12% 25% 18% 2	3349
November	1st to 10th	Day	38% 5% 11% 26% 17% 3	1762
	11th to 20th	Day	53% 5% 9% 20% 11% 3	1800
	21st to end	Day	59% 4 9% 18% 9% 1	1800
December	1st to 10th	Day	64% 5% 14% 15% 3	2930
	11th to 20th	Day	67% 4 11% 14% 4	3370
	21st to end	Day	75% 5% 7% 9% 4	4466
January	1st to 10th	Night	72% 4 7% 13% 4	5889
	11th to 20th	Night	72% 5% 8% 9% 5% 1	5900
	21st to end	Night	65% 3 11% 13% 6% 2	6490
February	1st to 10th	Night	61% 4 11% 16% 8% 1	2600
	11th to 20th	Night	60% 4 10% 16% 9% 1	2386
	21st to end	Night	60% 4 10% 15% 9% 2	1980
March	1st to 10th	Night	52% 5% 8% 23% 10% 2	5127
	11th to 20th	Night	40% 6% 11% 32% 10% 2	4980
	21st to end	Night	50% 4 8% 22% 14% 2	5467
April	1st to 10th	Night	47% 6% 11% 20% 13% 2	2190
	11th to 20th	Night	44% 6% 11% 17% 18% 3	1802
	21st to end	Night	45% 6% 11% 21% 16% 2	1800
May	1st to 10th	Night	57% 7% 9% 15% 9% 3	4060
	11th to 20th	Night	44% 7% 10% 25% 13% 1	4033
	21st to end	Night	40% 8% 14% 27% 10% 2	4429
June	1st to 10th	Night	35% 8% 12% 23% 19% 2	1800
	11th to 20th	Night	35% 8% 14% 24% 17% 2	1800
	21st to end	Night	33% 10% 13% 24% 17% 2	1633
July	1st to 10th	Night	36% 7% 12% 24% 18% 4	3873
	11th to 20th	Night	36% 10% 15% 26% 13% 1	4006
	21st to end	Night	36% 8% 13% 20% 19% 3	4297
August	1st to 10th	Night	38% 8% 15% 24% 13% 1	2904
	11th to 20th	Night	39% 6% 10% 26% 19% 1	2902
	21st to end	Night	27% 9% 16% 30% 17% 2	3244
September	1st to 10th	Night	31% 6% 12% 25% 21% 6%	2185
	11th to 20th	Night	26% 5% 11% 29% 26% 3	2200
	21st to end	Night	40% 5% 10% 21% 24% 1	2200
October	1st to 10th	Night	26% 4 7% 29% 31% 2	3717
	11th to 20th	Night	30% 4 11% 28% 21% 5%	3876
	21st to end	Night	35% 4 8% 27% 22% 4	4197
November	1st to 10th	Night	38% 5% 12% 24% 18% 3	2536
	11th to 20th	Night	50% 4 8% 21% 14% 3	2600
	21st to end	Night	56% 4 12% 19% 7% 1	2600
December	1st to 10th	Night	58% 5% 12% 19% 6%	4250
	11th to 20th	Night	64% 4 13% 14% 4	4824
	21st to end	Night	72% 4 9% 11% 4	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	26% 21% 36% 11% 5% 1	300
	11th to 20th	Day	27% 22% 40% 9% 1 1	300
	21st to end	Day	27% 23% 34% 13% 2	330
February	1st to 10th	Day	28% 24% 33% 13% 1 1	300
	11th to 20th	Day	31% 27% 30% 10% 2	300
	21st to end	Day	29% 28% 33% 10% 1	249
March	1st to 10th	Day	23% 21% 35% 17% 4	401
	11th to 20th	Day	27% 15% 34% 18% 5% 1	500
	21st to end	Day	29% 16% 32% 18% 4 1	550
April	1st to 10th	Day	23% 17% 33% 17% 9% 2	500
	11th to 20th	Day	24% 16% 30% 16% 10% 4	492
	21st to end	Day	23% 15% 31% 22% 7% 2	500
May	1st to 10th	Day	27% 13% 29% 19% 9% 3	503
	11th to 20th	Day	21% 9% 26% 25% 14% 5%	527
	21st to end	Day	14% 9% 23% 27% 18% 9%	573
June	1st to 10th	Day	12% 7% 25% 33% 18% 5%	530
	11th to 20th	Day	13% 8% 21% 30% 22% 6%	530
	21st to end	Day	12% 7% 26% 28% 19% 7%	678
July	1st to 10th	Day	12% 3 18% 25% 24% 18%	580
	11th to 20th	Day	11% 5% 22% 25% 25% 12%	524
	21st to end	Day	11% 3 18% 28% 26% 13%	576
August	1st to 10th	Day	10% 5% 15% 25% 29% 16%	526
	11th to 20th	Day	12% 5% 19% 28% 24% 13%	519
	21st to end	Day	7% 3 17% 30% 28% 15%	583
September	1st to 10th	Day	12% 5% 17% 25% 27% 14%	530
	11th to 20th	Day	10% 2 14% 24% 34% 16%	530
	21st to end	Day	22% 8% 19% 24% 19% 8%	530
October	1st to 10th	Day	12% 8% 24% 28% 21% 8%	530
	11th to 20th	Day	14% 14% 32% 25% 12% 3	522
	21st to end	Day	25% 13% 32% 21% 8% 1	496
November	1st to 10th	Day	16% 14% 37% 19% 12% 2	300
	11th to 20th	Day	23% 18% 32% 16% 9% 2	300
	21st to end	Day	25% 22% 36% 14% 3	300
December	1st to 10th	Day	25% 20% 35% 15% 4 2	300
	11th to 20th	Day	24% 21% 40% 11% 3	300
	21st to end	Day	33% 19% 31% 15% 3	330
January	1st to 10th	Night	24% 18% 37% 18% 3	800
	11th to 20th	Night	27% 17% 35% 18% 3	800
	21st to end	Night	24% 15% 35% 23% 3	880
February	1st to 10th	Night	25% 14% 36% 24% 2	800
	11th to 20th	Night	24% 17% 37% 20% 2	783
	21st to end	Night	26% 14% 38% 20% 2	660
March	1st to 10th	Night	21% 12% 35% 26% 5%	800
	11th to 20th	Night	19% 15% 34% 25% 7%	800
	21st to end	Night	22% 14% 32% 26% 6% 1	880
April	1st to 10th	Night	20% 13% 36% 25% 6% 1	790
	11th to 20th	Night	16% 13% 35% 25% 9% 2	593
	21st to end	Night	19% 7% 39% 27% 8% 1	600
May	1st to 10th	Night	21% 9% 28% 30% 12% 1	600
	11th to 20th	Night	20% 4 26% 35% 13% 2	591
	21st to end	Night	10% 3 23% 37% 25% 2	650
June	1st to 10th	Night	10% 3 23% 41% 22% 1	600
	11th to 20th	Night	10% 4 18% 43% 23% 2	600
	21st to end	Night	10% 2 23% 40% 22% 3	600
July	1st to 10th	Night	10% 2 13% 40% 27% 7%	585
	11th to 20th	Night	8% 1 15% 38% 33% 4	582
	21st to end	Night	9% 2 13% 39% 35% 2	657
August	1st to 10th	Night	8% 2 10% 43% 32% 5%	597
	11th to 20th	Night	10% 2 13% 38% 32% 5%	594
	21st to end	Night	7% 2 12% 37% 34% 8%	660
September	1st to 10th	Night	13% 3 15% 33% 30% 6%	785
	11th to 20th	Night	9% 2 12% 38% 33% 6%	800
	21st to end	Night	18% 5% 22% 31% 23% 3	800
October	1st to 10th	Night	12% 5% 22% 35% 22% 4	800
	11th to 20th	Night	18% 9% 30% 29% 13% 1	793
	21st to end	Night	22% 10% 31% 27% 9%	836
November	1st to 10th	Night	16% 9% 30% 30% 14% 1	780
	11th to 20th	Night	21% 14% 31% 26% 8% 1	800
	21st to end	Night	23% 11% 33% 26% 7% 1	800
December	1st to 10th	Night	27% 12% 34% 22% 4	800
	11th to 20th	Night	25% 13% 35% 23% 4	800
	21st to end	Night	30% 13% 31% 22% 4	880

Page generated at 2025-10-16 01:50:26. Version ac07

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