Hutchinson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hutchinson clear sky chart from 2005-11-06 to 2024-07-02.

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	9% 6% 2 5% 4 3 4 3 5% 7% 51%	89679
	Night	9% 6% 2 5% 3 3 3 3 5% 7% 54%	89550
Transparency	Day	32% 4 12% 27% 20% 5%	89454
	Night	30% 4 12% 27% 22% 5%	89380
Seeing	Day	11% 7% 29% 31% 18% 4	15090
	Night	10% 7% 34% 36% 11% 1	25032

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	9% 7% 2 10% 5% 4 4 3 5% 6% 45%	2847
	11th to 20th	Day	7% 8% 4 7% 5% 5% 4 3 5% 7% 44%	2850
	21st to end	Day	10% 11% 3 7% 4 3 3 2 3 5% 48%	3135
February	1st to 10th	Day	8% 10% 3 7% 4 5% 3 3 4 7% 46%	1745
	11th to 20th	Day	6% 7% 3 7% 4 4 4 4 4 6% 51%	1849
	21st to end	Day	7% 6% 2 6% 3 3 4 4 5% 7% 52%	1570
March	1st to 10th	Day	9% 7% 1 4 2 2 3 3 5% 7% 57%	3301
	11th to 20th	Day	9% 5% 1 3 2 2 3 2 5% 8% 59%	3480
	21st to end	Day	11% 7% 2 6% 4 4 4 3 6% 8% 46%	3814
April	1st to 10th	Day	10% 6% 3 4 2 2 3 4 5% 7% 52%	2090
	11th to 20th	Day	11% 8% 2 6% 4 4 4 4 4 7% 46%	2360
	21st to end	Day	15% 6% 2 6% 5% 4 3 4 5% 7% 44%	2470
May	1st to 10th	Day	17% 8% 3 6% 5% 4 4 3 4 6% 40%	4082
	11th to 20th	Day	12% 5% 2 6% 4 3 4 4 5% 7% 49%	4082
	21st to end	Day	11% 6% 2 6% 5% 4 4 4 6% 8% 45%	4477
June	1st to 10th	Day	5% 4 2 5% 3 3 4 4 7% 8% 55%	2470
	11th to 20th	Day	5% 4 1 5% 4 4 4 4 6% 8% 55%	2470
	21st to end	Day	5% 3 2 3 4 4 4 4 6% 9% 56%	2470
July	1st to 10th	Day	7% 4 2 5% 5% 4 5% 4 6% 9% 49%	2354
	11th to 20th	Day	3 2 1 4 3 4 4 4 7% 10% 57%	2340
	21st to end	Day	6% 5% 2 5% 4 4 5% 5% 8% 8% 48%	2546
August	1st to 10th	Day	7% 4 1 5% 4 5% 4 5% 7% 10% 48%	2328
	11th to 20th	Day	7% 4 2 5% 3 3 5% 4 5% 9% 54%	2301
	21st to end	Day	4 3 2 4 2 3 4 4 5% 8% 60%	2486
September	1st to 10th	Day	10% 4 2 4 4 3 4 3 5% 5% 56%	1982
	11th to 20th	Day	9% 5% 2 5% 3 4 4 3 5% 6% 54%	1980
	21st to end	Day	7% 4 2 5% 4 4 3 4 5% 6% 57%	1980
October	1st to 10th	Day	12% 5% 1 3 2 3 3 3 4 5% 57%	1945
	11th to 20th	Day	10% 4 1 3 3 2 2 3 3 6% 63%	1800
	21st to end	Day	11% 6% 2 5% 3 3 3 2 4 5% 58%	1976
November	1st to 10th	Day	6% 3 1 5% 3 3 3 3 4 6% 62%	1673
	11th to 20th	Day	7% 6% 1 5% 3 3 2 2 4 5% 61%	1710
	21st to end	Day	11% 5% 1 4 3 3 3 2 3 5% 61%	1710
December	1st to 10th	Day	8% 6% 2 5% 4 2 4 3 6% 6% 53%	1710
	11th to 20th	Day	9% 7% 2 7% 4 2 3 3 4 7% 52%	2161
	21st to end	Day	9% 11% 5% 9% 5% 4 4 4 5% 6% 38%	3135
January	1st to 10th	Night	8% 8% 3 10% 5% 4 4 3 4 5% 45%	4108
	11th to 20th	Night	5% 6% 2 5% 5% 4 5% 3 4 5% 55%	4120
	21st to end	Night	14% 10% 3 5% 3 3 3 2 3 5% 50%	4532
February	1st to 10th	Night	10% 9% 2 6% 4 3 4 3 5% 6% 48%	2451
	11th to 20th	Night	9% 7% 2 5% 4 3 4 4 5% 7% 50%	2218
	21st to end	Night	7% 6% 2 6% 4 3 3 3 5% 6% 56%	1884
March	1st to 10th	Night	7% 6% 1 3 3 3 3 3 4 6% 60%	3556
	11th to 20th	Night	7% 6% 2 5% 3 4 4 3 5% 7% 55%	3480
	21st to end	Night	11% 9% 3 5% 3 3 3 3 4 6% 51%	3817
April	1st to 10th	Night	9% 5% 1 5% 3 2 3 4 5% 9% 53%	2090
	11th to 20th	Night	11% 6% 2 5% 3 3 5% 3 5% 6% 50%	1765
	21st to end	Night	13% 7% 2 5% 3 4 3 3 5% 6% 48%	1710
May	1st to 10th	Night	18% 7% 2 4 3 3 3 3 4 6% 48%	2823
	11th to 20th	Night	12% 4 1 4 3 3 4 4 6% 10% 49%	2823
	21st to end	Night	9% 4 2 4 3 3 3 3 7% 9% 55%	3090
June	1st to 10th	Night	6% 3 1 3 3 3 3 4 6% 12% 56%	1710
	11th to 20th	Night	4 3 1 4 4 4 5% 5% 7% 9% 55%	1710
	21st to end	Night	4 2 1 5% 3 4 3 3 6% 9% 59%	1710
July	1st to 10th	Night	7% 3 1 4 4 3 4 4 6% 9% 55%	1634
	11th to 20th	Night	2 2 1 3 3 3 3 4 8% 10% 61%	1620
	21st to end	Night	6% 4 2 5% 4 4 4 5% 8% 11% 48%	1772
August	1st to 10th	Night	4 3 1 4 4 5% 5% 4 5% 11% 54%	1611
	11th to 20th	Night	7% 4 1 5% 4 3 4 4 6% 7% 53%	1600
	21st to end	Night	3 4 2 4 3 3 3 4 5% 7% 62%	1865
September	1st to 10th	Night	8% 3 2 5% 4 3 4 4 4 6% 59%	1976
	11th to 20th	Night	8% 4 1 6% 3 3 4 3 5% 6% 57%	1980
	21st to end	Night	6% 3 2 3 3 3 4 4 5% 6% 61%	1980
October	1st to 10th	Night	11% 4 2 5% 3 3 3 2 5% 6% 56%	1996
	11th to 20th	Night	10% 3 1 4 2 2 3 2 3 5% 66%	2160
	21st to end	Night	10% 5% 1 5% 2 2 3 2 4 5% 61%	2376
November	1st to 10th	Night	7% 3 2 4 2 2 2 2 3 5% 67%	2405
	11th to 20th	Night	7% 5% 1 4 3 2 3 3 4 6% 63%	2470
	21st to end	Night	12% 5% 2 3 3 2 3 2 4 5% 59%	2470
December	1st to 10th	Night	7% 6% 2 4 4 3 4 3 5% 6% 56%	2470
	11th to 20th	Night	9% 5% 2 4 3 3 3 3 5% 6% 55%	3036
	21st to end	Night	13% 9% 3 7% 4 4 4 3 5% 7% 42%	4532

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	40% 4 11% 27% 17% 2	2848
	11th to 20th	Day	40% 3 16% 25% 12% 5%	2850
	21st to end	Day	40% 3 11% 26% 17% 2	3135
February	1st to 10th	Day	40% 4 12% 26% 14% 5%	1745
	11th to 20th	Day	34% 4 13% 27% 16% 6%	1859
	21st to end	Day	31% 4 9% 26% 24% 6%	1570
March	1st to 10th	Day	29% 3 9% 22% 28% 9%	3301
	11th to 20th	Day	25% 3 14% 25% 29% 3	3480
	21st to end	Day	36% 5% 13% 33% 10% 2	3814
April	1st to 10th	Day	31% 4 13% 26% 22% 5%	2090
	11th to 20th	Day	38% 4 11% 26% 17% 5%	2360
	21st to end	Day	39% 4 11% 29% 15% 1	2470
May	1st to 10th	Day	44% 5% 10% 20% 14% 6%	4120
	11th to 20th	Day	35% 5% 13% 27% 20%	4086
	21st to end	Day	36% 5% 13% 24% 17% 4	4489
June	1st to 10th	Day	25% 5% 19% 31% 16% 4	2470
	11th to 20th	Day	27% 5% 14% 29% 21% 5%	2470
	21st to end	Day	23% 5% 14% 25% 24% 7%	2470
July	1st to 10th	Day	29% 6% 15% 28% 18% 5%	2290
	11th to 20th	Day	19% 6% 15% 29% 24% 6%	2271
	21st to end	Day	29% 5% 15% 30% 20% 2	2405
August	1st to 10th	Day	30% 6% 17% 28% 15% 4	2314
	11th to 20th	Day	26% 5% 13% 32% 18% 5%	2301
	21st to end	Day	23% 5% 13% 28% 23% 9%	2486
September	1st to 10th	Day	30% 4 10% 25% 21% 9%	1982
	11th to 20th	Day	31% 5% 8% 27% 24% 5%	1980
	21st to end	Day	28% 4 10% 25% 25% 7%	1980
October	1st to 10th	Day	29% 3 10% 26% 26% 5%	1945
	11th to 20th	Day	25% 2 8% 27% 30% 9%	1800
	21st to end	Day	30% 3 9% 27% 23% 9%	1976
November	1st to 10th	Day	24% 3 10% 29% 27% 8%	1673
	11th to 20th	Day	27% 2 9% 27% 28% 6%	1710
	21st to end	Day	28% 3 8% 28% 27% 5%	1710
December	1st to 10th	Day	31% 3 12% 32% 21% 2	1710
	11th to 20th	Day	33% 3 8% 31% 22% 3	2159
	21st to end	Day	46% 4 8% 27% 13% 2	3135
January	1st to 10th	Night	41% 3 10% 28% 16% 3	4108
	11th to 20th	Night	31% 4 14% 28% 21% 3	4120
	21st to end	Night	40% 2 11% 25% 20% 2	4532
February	1st to 10th	Night	38% 4 12% 24% 17% 5%	2451
	11th to 20th	Night	34% 3 12% 27% 19% 5%	2218
	21st to end	Night	30% 3 9% 23% 25% 11%	1884
March	1st to 10th	Night	25% 3 7% 25% 30% 8%	3556
	11th to 20th	Night	29% 4 9% 24% 31% 4	3480
	21st to end	Night	36% 4 14% 33% 11% 3	3817
April	1st to 10th	Night	29% 4 12% 23% 24% 7%	2090
	11th to 20th	Night	34% 4 13% 24% 21% 4	1765
	21st to end	Night	37% 4 12% 23% 20% 4	1710
May	1st to 10th	Night	39% 4 11% 21% 18% 8%	2850
	11th to 20th	Night	30% 5% 17% 32% 15% 1	2824
	21st to end	Night	25% 6% 19% 29% 20% 2	3099
June	1st to 10th	Night	22% 6% 21% 31% 17% 3	1710
	11th to 20th	Night	23% 5% 16% 31% 20% 4	1710
	21st to end	Night	23% 3 14% 29% 23% 7%	1710
July	1st to 10th	Night	25% 6% 15% 27% 23% 4	1589
	11th to 20th	Night	17% 5% 16% 30% 26% 7%	1566
	21st to end	Night	28% 6% 15% 30% 20% 2	1673
August	1st to 10th	Night	24% 6% 17% 34% 15% 4	1601
	11th to 20th	Night	28% 6% 12% 31% 19% 4	1600
	21st to end	Night	22% 5% 12% 26% 25% 9%	1865
September	1st to 10th	Night	27% 4 11% 24% 23% 11%	1976
	11th to 20th	Night	28% 4 10% 24% 28% 6%	1980
	21st to end	Night	23% 4 11% 24% 30% 9%	1980
October	1st to 10th	Night	29% 4 9% 22% 29% 7%	1996
	11th to 20th	Night	24% 3 6% 26% 31% 10%	2160
	21st to end	Night	27% 3 9% 23% 27% 10%	2376
November	1st to 10th	Night	22% 2 9% 28% 29% 10%	2405
	11th to 20th	Night	24% 2 8% 30% 30% 6%	2470
	21st to end	Night	29% 3 10% 26% 24% 9%	2470
December	1st to 10th	Night	29% 4 13% 27% 22% 4	2470
	11th to 20th	Night	31% 3 8% 33% 21% 4	3037
	21st to end	Night	41% 4 11% 28% 13% 3	4532

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	11% 9% 41% 24% 13% 2	270
	11th to 20th	Day	15% 12% 40% 26% 6%	270
	21st to end	Day	9% 11% 43% 30% 6%	297
February	1st to 10th	Day	13% 14% 44% 24% 4 1	270
	11th to 20th	Day	10% 12% 46% 24% 7% 1	270
	21st to end	Day	10% 15% 52% 20% 3 1	225
March	1st to 10th	Day	11% 11% 43% 29% 6%	270
	11th to 20th	Day	18% 12% 36% 27% 6% 1	270
	21st to end	Day	19% 16% 39% 21% 4 1	297
April	1st to 10th	Day	11% 16% 39% 27% 6% 1	270
	11th to 20th	Day	13% 16% 39% 28% 5%	558
	21st to end	Day	18% 14% 37% 20% 9% 2	650
May	1st to 10th	Day	15% 10% 35% 28% 10% 2	653
	11th to 20th	Day	16% 8% 27% 27% 17% 4	675
	21st to end	Day	14% 8% 31% 27% 17% 4	734
June	1st to 10th	Day	5% 3 24% 37% 23% 8%	680
	11th to 20th	Day	6% 4 31% 38% 19% 3	680
	21st to end	Day	5% 5% 30% 42% 18% 1	680
July	1st to 10th	Day	8% 1 12% 38% 31% 9%	627
	11th to 20th	Day	4 2 13% 43% 31% 8%	618
	21st to end	Day	6% 1 12% 39% 32% 9%	684
August	1st to 10th	Day	9% 1 13% 38% 33% 5%	626
	11th to 20th	Day	7% 1 15% 38% 33% 6%	615
	21st to end	Day	6% 14% 37% 35% 7%	605
September	1st to 10th	Day	11% 2 11% 33% 35% 8%	272
	11th to 20th	Day	5% 1 17% 41% 29% 7%	270
	21st to end	Day	14% 3 28% 26% 22% 7%	270
October	1st to 10th	Day	14% 7% 28% 21% 19% 10%	270
	11th to 20th	Day	8% 9% 38% 30% 14% 1	270
	21st to end	Day	19% 12% 30% 24% 12% 3	297
November	1st to 10th	Day	9% 11% 30% 34% 14% 2	270
	11th to 20th	Day	12% 13% 38% 22% 13% 1	270
	21st to end	Day	18% 10% 30% 28% 11% 2	270
December	1st to 10th	Day	6% 9% 37% 31% 14% 3	270
	11th to 20th	Day	11% 10% 37% 31% 10%	270
	21st to end	Day	17% 15% 42% 22% 3	297
January	1st to 10th	Night	9% 9% 38% 36% 7%	950
	11th to 20th	Night	9% 11% 39% 32% 8% 1	950
	21st to end	Night	10% 9% 41% 34% 6%	1045
February	1st to 10th	Night	14% 9% 41% 31% 4	931
	11th to 20th	Night	12% 10% 41% 33% 4	744
	21st to end	Night	10% 14% 43% 30% 4	628
March	1st to 10th	Night	10% 12% 41% 33% 4	660
	11th to 20th	Night	15% 9% 38% 30% 7%	570
	21st to end	Night	17% 10% 42% 26% 5%	627
April	1st to 10th	Night	12% 12% 44% 26% 7%	570
	11th to 20th	Night	15% 12% 39% 29% 5%	563
	21st to end	Night	15% 11% 36% 31% 6%	570
May	1st to 10th	Night	16% 10% 33% 33% 8%	570
	11th to 20th	Night	13% 6% 31% 36% 13% 1	561
	21st to end	Night	12% 8% 29% 35% 15% 2	617
June	1st to 10th	Night	6% 3 26% 44% 20% 2	570
	11th to 20th	Night	6% 4 35% 42% 14%	570
	21st to end	Night	4 3 35% 43% 14%	570
July	1st to 10th	Night	7% 1 14% 51% 25% 1	530
	11th to 20th	Night	4 1 17% 54% 23% 2	522
	21st to end	Night	7% 1 16% 46% 28% 2	591
August	1st to 10th	Night	4 1 18% 50% 26% 1	537
	11th to 20th	Night	8% 2 14% 51% 23% 2	534
	21st to end	Night	5% 1 17% 44% 31% 2	594
September	1st to 10th	Night	9% 1 23% 44% 21% 2	540
	11th to 20th	Night	7% 2 29% 41% 19% 1	540
	21st to end	Night	8% 5% 28% 40% 18% 1	540
October	1st to 10th	Night	12% 4 30% 35% 18% 2	556
	11th to 20th	Night	11% 7% 41% 32% 9%	720
	21st to end	Night	14% 8% 32% 35% 11% 1	792
November	1st to 10th	Night	8% 6% 34% 38% 12% 1	925
	11th to 20th	Night	9% 9% 40% 32% 9%	950
	21st to end	Night	14% 9% 29% 38% 9% 1	950
December	1st to 10th	Night	10% 8% 37% 36% 7% 1	950
	11th to 20th	Night	13% 9% 40% 34% 4	950
	21st to end	Night	13% 10% 39% 32% 6%	1045

Page generated at 2024-06-29 06:12:28. Version ac07

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