Litchfield High School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Litchfield High School clear sky chart from 2005-11-06 to 2026-02-01.

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	12% 8% 3 8% 5% 4 5% 4 6% 7% 39%	128390
	Night	11% 9% 3 8% 5% 4 4 4 5% 7% 39%	123860
Transparency	Day	43% 5% 13% 26% 11% 1	131976
	Night	44% 5% 12% 25% 13% 2	128351
Seeing	Day	16% 9% 31% 28% 14% 3	17692
	Night	15% 9% 33% 32% 11% 1	27705

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	7% 14% 3 15% 11% 6% 6% 4 6% 8% 20%	3363
	11th to 20th	Day	6% 8% 4 13% 7% 7% 8% 7% 11% 8% 20%	3903
	21st to end	Day	4 12% 7% 13% 7% 6% 5% 4 5% 7% 30%	4587
February	1st to 10th	Day	8% 12% 4 10% 6% 6% 5% 5% 6% 7% 30%	1800
	11th to 20th	Day	8% 10% 4 10% 7% 5% 5% 5% 6% 6% 34%	1754
	21st to end	Day	10% 11% 4 8% 7% 5% 5% 4 6% 7% 33%	1505
March	1st to 10th	Day	11% 9% 3 7% 4 4 4 3 6% 7% 43%	4936
	11th to 20th	Day	9% 8% 4 8% 4 4 5% 4 5% 7% 42%	4980
	21st to end	Day	21% 11% 3 10% 7% 5% 5% 3 5% 6% 25%	5462
April	1st to 10th	Day	17% 11% 3 7% 4 3 4 4 6% 6% 37%	2370
	11th to 20th	Day	18% 11% 4 8% 5% 4 4 4 5% 6% 31%	2467
	21st to end	Day	23% 11% 2 7% 4 4 4 4 5% 6% 32%	2600
May	1st to 10th	Day	13% 5% 2 5% 4 4 4 3 5% 6% 50%	5954
	11th to 20th	Day	17% 8% 2 6% 4 3 3 3 4 6% 44%	6319
	21st to end	Day	17% 7% 2 6% 4 4 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	11% 5% 2 5% 5% 4 4 5% 7% 8% 45%	2810
	11th to 20th	Day	14% 8% 2 7% 5% 4 5% 5% 6% 8% 37%	3000
	21st to end	Day	10% 5% 2 6% 4 5% 5% 4 7% 9% 44%	3000
July	1st to 10th	Day	7% 4 2 5% 4 5% 5% 5% 7% 11% 45%	6800
	11th to 20th	Day	8% 4 1 4 3 3 3 3 5% 9% 56%	6492
	21st to end	Day	7% 4 2 6% 5% 4 5% 4 7% 10% 46%	6656
August	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 8% 43%	4234
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	4171
	21st to end	Day	9% 6% 2 6% 4 4 4 3 5% 8% 49%	4560
September	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 6% 8% 50%	2400
	11th to 20th	Day	11% 4 2 6% 4 5% 5% 3 6% 8% 45%	2288
	21st to end	Day	15% 6% 2 5% 3 3 3 3 4 8% 48%	2155
October	1st to 10th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 43%	2000
	11th to 20th	Day	15% 8% 3 6% 4 3 4 3 4 8% 40%	2000
	21st to end	Day	17% 11% 4 6% 4 3 3 3 5% 7% 37%	2200
November	1st to 10th	Day	13% 11% 3 8% 5% 4 3 4 5% 6% 37%	1689
	11th to 20th	Day	9% 13% 5% 13% 6% 4 4 4 5% 5% 33%	1680
	21st to end	Day	13% 10% 4 9% 6% 5% 5% 3 7% 8% 32%	1680
December	1st to 10th	Day	7% 9% 4 12% 9% 9% 7% 5% 7% 7% 25%	2690
	11th to 20th	Day	9% 15% 7% 11% 6% 6% 5% 3 5% 6% 28%	3088
	21st to end	Day	19% 17% 5% 20% 5% 4 3 2 3 5% 16%	3862
January	1st to 10th	Night	7% 10% 5% 16% 9% 6% 5% 3 5% 6% 28%	6787
	11th to 20th	Night	6% 11% 4 11% 7% 7% 10% 7% 7% 6% 24%	6294
	21st to end	Night	6% 14% 7% 10% 5% 4 4 4 6% 6% 33%	6633
February	1st to 10th	Night	7% 12% 5% 8% 7% 5% 5% 4 5% 6% 36%	2601
	11th to 20th	Night	6% 9% 4 7% 6% 5% 6% 4 6% 8% 40%	2533
	21st to end	Night	10% 10% 4 7% 5% 5% 4 4 6% 7% 38%	2141
March	1st to 10th	Night	10% 6% 2 6% 4 3 4 3 5% 8% 49%	4919
	11th to 20th	Night	9% 7% 2 7% 5% 4 5% 4 7% 10% 41%	4980
	21st to end	Night	23% 11% 4 9% 5% 4 3 3 4 5% 29%	5467
April	1st to 10th	Night	14% 9% 3 7% 4 4 3 3 5% 6% 39%	2029
	11th to 20th	Night	18% 11% 3 7% 3 3 3 4 6% 5% 37%	1879
	21st to end	Night	20% 10% 3 7% 4 4 3 3 5% 5% 37%	1800
May	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 5% 55%	3961
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 5% 7% 48%	3596
	21st to end	Night	17% 8% 2 7% 4 4 4 4 4 7% 39%	3942
June	1st to 10th	Night	11% 4 2 5% 4 4 4 4 6% 8% 49%	1585
	11th to 20th	Night	9% 5% 2 5% 4 5% 4 3 7% 8% 48%	1400
	21st to end	Night	10% 4 1 4 3 4 4 4 5% 7% 55%	1400
July	1st to 10th	Night	8% 4 2 5% 3 4 4 4 7% 9% 50%	3178
	11th to 20th	Night	5% 3 2 5% 4 3 4 4 6% 8% 57%	3480
	21st to end	Night	8% 5% 2 6% 5% 4 4 4 6% 8% 49%	4210
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 49%	2926
	11th to 20th	Night	13% 5% 2 5% 3 3 5% 3 6% 7% 49%	2888
	21st to end	Night	8% 5% 2 6% 4 3 4 3 5% 8% 52%	3344
September	1st to 10th	Night	8% 3 2 5% 3 3 4 4 6% 8% 56%	2000
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 5% 7% 54%	2110
	21st to end	Night	10% 5% 2 5% 3 3 3 3 4 6% 56%	2225
October	1st to 10th	Night	14% 5% 2 5% 3 3 4 3 4 7% 50%	2400
	11th to 20th	Night	15% 9% 3 5% 3 3 4 3 5% 6% 44%	2400
	21st to end	Night	17% 11% 3 7% 3 3 3 3 5% 6% 39%	2640
November	1st to 10th	Night	11% 8% 3 6% 4 4 5% 4 6% 7% 43%	2826
	11th to 20th	Night	12% 11% 5% 10% 5% 4 4 3 4 6% 37%	2940
	21st to end	Night	12% 10% 4 9% 5% 4 4 3 6% 6% 38%	2940
December	1st to 10th	Night	6% 8% 5% 12% 9% 6% 5% 5% 6% 8% 32%	4720
	11th to 20th	Night	10% 13% 6% 13% 7% 6% 5% 4 5% 5% 26%	5339
	21st to end	Night	19% 16% 5% 16% 6% 4 4 3 3 4 18%	7347

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	63% 5% 9% 15% 8%	3364
	11th to 20th	Day	55% 5% 12% 20% 9%	3903
	21st to end	Day	55% 6% 14% 16% 9%	4587
February	1st to 10th	Day	51% 6% 12% 21% 8% 1	1800
	11th to 20th	Day	50% 5% 14% 22% 8% 1	1763
	21st to end	Day	49% 6% 11% 22% 11%	1505
March	1st to 10th	Day	40% 5% 15% 26% 11% 2	4936
	11th to 20th	Day	41% 4 13% 29% 11% 1	4980
	21st to end	Day	61% 4 10% 20% 6%	5464
April	1st to 10th	Day	48% 6% 11% 23% 12% 1	2370
	11th to 20th	Day	52% 5% 12% 18% 11% 1	2467
	21st to end	Day	52% 6% 11% 21% 9% 1	2600
May	1st to 10th	Day	35% 5% 12% 29% 18% 1	5992
	11th to 20th	Day	41% 4 8% 23% 16% 7%	6323
	21st to end	Day	44% 6% 10% 31% 8% 1	6949
June	1st to 10th	Day	33% 8% 15% 30% 12% 1	2810
	11th to 20th	Day	43% 8% 13% 20% 14% 1	3000
	21st to end	Day	34% 8% 18% 27% 11% 1	3000
July	1st to 10th	Day	33% 5% 20% 32% 10%	6726
	11th to 20th	Day	26% 4 17% 37% 15% 1	6414
	21st to end	Day	33% 5% 17% 31% 13% 1	6467
August	1st to 10th	Day	38% 6% 13% 30% 12% 2	4220
	11th to 20th	Day	40% 5% 14% 32% 8%	4210
	21st to end	Day	33% 5% 19% 29% 12% 1	4559
September	1st to 10th	Day	32% 6% 14% 36% 13%	2400
	11th to 20th	Day	36% 7% 18% 30% 10%	2288
	21st to end	Day	36% 5% 11% 34% 13% 1	2155
October	1st to 10th	Day	32% 3 8% 33% 23% 1	3260
	11th to 20th	Day	38% 4 12% 23% 22% 2	3240
	21st to end	Day	45% 3 15% 27% 9%	3538
November	1st to 10th	Day	46% 6% 13% 21% 12% 2	1689
	11th to 20th	Day	53% 5% 12% 19% 10% 1	1680
	21st to end	Day	50% 5% 15% 22% 7% 1	1680
December	1st to 10th	Day	57% 6% 14% 17% 5%	2690
	11th to 20th	Day	58% 4 15% 18% 6%	3085
	21st to end	Day	73% 3 9% 11% 5%	3862
January	1st to 10th	Night	57% 4 10% 21% 8%	6787
	11th to 20th	Night	57% 6% 9% 16% 11% 1	6294
	21st to end	Night	51% 4 12% 26% 7%	6633
February	1st to 10th	Night	48% 4 14% 20% 12% 1	2601
	11th to 20th	Night	42% 6% 15% 25% 11% 2	2534
	21st to end	Night	45% 6% 13% 21% 14% 2	2141
March	1st to 10th	Night	34% 4 13% 31% 15% 2	4919
	11th to 20th	Night	37% 4 15% 30% 13%	4980
	21st to end	Night	59% 3 9% 19% 9% 1	5467
April	1st to 10th	Night	45% 5% 11% 27% 12% 1	2029
	11th to 20th	Night	47% 4 8% 22% 16% 2	1879
	21st to end	Night	49% 5% 9% 20% 14% 2	1800
May	1st to 10th	Night	32% 5% 12% 30% 19% 3	3988
	11th to 20th	Night	36% 5% 8% 21% 21% 8%	3597
	21st to end	Night	45% 5% 10% 28% 12% 1	3950
June	1st to 10th	Night	30% 6% 15% 31% 15% 2	1585
	11th to 20th	Night	33% 6% 16% 26% 17% 3	1400
	21st to end	Night	27% 7% 15% 30% 18% 3	1400
July	1st to 10th	Night	31% 5% 20% 28% 16% 1	3145
	11th to 20th	Night	25% 3 17% 38% 15% 2	3439
	21st to end	Night	34% 5% 16% 32% 12% 2	4088
August	1st to 10th	Night	36% 5% 13% 27% 14% 5%	2916
	11th to 20th	Night	34% 5% 15% 33% 12%	2915
	21st to end	Night	30% 5% 18% 31% 14% 2	3344
September	1st to 10th	Night	26% 6% 16% 34% 18% 1	2000
	11th to 20th	Night	30% 6% 15% 32% 17%	2110
	21st to end	Night	30% 4 12% 35% 18% 2	2225
October	1st to 10th	Night	23% 3 6% 38% 27% 4	3920
	11th to 20th	Night	32% 3 11% 28% 22% 3	3899
	21st to end	Night	42% 3 11% 30% 13% 1	4252
November	1st to 10th	Night	40% 5% 15% 25% 13% 2	2826
	11th to 20th	Night	49% 5% 12% 20% 13% 1	2940
	21st to end	Night	47% 4 17% 23% 7% 1	2940
December	1st to 10th	Night	50% 5% 18% 21% 6%	4720
	11th to 20th	Night	59% 6% 10% 19% 5% 1	5341
	21st to end	Night	70% 4 8% 14% 4	7347

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	15% 8% 32% 27% 14% 3	330
	11th to 20th	Day	14% 11% 39% 32% 4 1	330
	21st to end	Day	13% 10% 43% 23% 10% 2	363
February	1st to 10th	Day	15% 12% 41% 28% 3	300
	11th to 20th	Day	15% 15% 33% 27% 8% 1	300
	21st to end	Day	16% 9% 43% 27% 5%	249
March	1st to 10th	Day	19% 10% 43% 22% 5% 1	300
	11th to 20th	Day	17% 10% 39% 24% 9% 1	300
	21st to end	Day	25% 13% 26% 25% 10% 2	330
April	1st to 10th	Day	24% 13% 32% 25% 5%	470
	11th to 20th	Day	25% 15% 27% 22% 10% 1	585
	21st to end	Day	26% 9% 33% 20% 9% 2	700
May	1st to 10th	Day	19% 10% 35% 23% 11% 2	703
	11th to 20th	Day	20% 9% 28% 26% 14% 3	725
	21st to end	Day	17% 7% 30% 30% 13% 3	789
June	1st to 10th	Day	10% 9% 26% 31% 20% 5%	730
	11th to 20th	Day	18% 7% 32% 31% 11% 2	730
	21st to end	Day	14% 6% 33% 29% 15% 4	730
July	1st to 10th	Day	8% 3 24% 34% 23% 8%	721
	11th to 20th	Day	9% 5% 27% 31% 22% 6%	718
	21st to end	Day	7% 3 24% 38% 23% 5%	794
August	1st to 10th	Day	13% 3 21% 33% 25% 4	726
	11th to 20th	Day	14% 5% 21% 33% 22% 5%	715
	21st to end	Day	9% 5% 26% 33% 23% 5%	740
September	1st to 10th	Day	12% 8% 28% 32% 15% 5%	530
	11th to 20th	Day	13% 5% 28% 31% 19% 5%	418
	21st to end	Day	19% 10% 27% 22% 18% 5%	330
October	1st to 10th	Day	16% 12% 30% 26% 12% 5%	330
	11th to 20th	Day	16% 17% 39% 19% 8% 1	330
	21st to end	Day	26% 11% 38% 17% 8%	363
November	1st to 10th	Day	21% 12% 35% 23% 7% 2	330
	11th to 20th	Day	15% 16% 44% 21% 4	330
	21st to end	Day	21% 15% 36% 22% 5%	330
December	1st to 10th	Day	14% 10% 40% 26% 8% 1	330
	11th to 20th	Day	17% 15% 37% 28% 5%	330
	21st to end	Day	28% 9% 37% 22% 3	363
January	1st to 10th	Night	11% 11% 38% 30% 9% 1	1050
	11th to 20th	Night	13% 12% 37% 31% 6% 1	1050
	21st to end	Night	15% 11% 37% 29% 7%	1155
February	1st to 10th	Night	12% 11% 38% 30% 8% 1	1001
	11th to 20th	Night	11% 12% 42% 29% 6% 1	979
	21st to end	Night	15% 11% 36% 29% 9% 1	821
March	1st to 10th	Night	16% 9% 39% 26% 10% 1	600
	11th to 20th	Night	17% 11% 38% 28% 6% 1	600
	21st to end	Night	23% 9% 30% 27% 9% 2	660
April	1st to 10th	Night	19% 9% 37% 27% 7%	600
	11th to 20th	Night	21% 13% 29% 27% 8% 1	593
	21st to end	Night	25% 8% 31% 26% 9% 1	600
May	1st to 10th	Night	18% 8% 34% 30% 9% 1	600
	11th to 20th	Night	17% 8% 33% 30% 10% 1	591
	21st to end	Night	18% 7% 26% 36% 12% 1	650
June	1st to 10th	Night	12% 6% 29% 38% 14% 1	600
	11th to 20th	Night	11% 4 36% 40% 10%	600
	21st to end	Night	10% 4 26% 44% 15% 1	600
July	1st to 10th	Night	6% 2 23% 41% 26% 2	585
	11th to 20th	Night	5% 3 24% 48% 18% 1	582
	21st to end	Night	7% 1 23% 47% 20% 2	657
August	1st to 10th	Night	10% 3 18% 46% 21% 2	597
	11th to 20th	Night	11% 4 18% 41% 23% 3	594
	21st to end	Night	8% 3 25% 38% 23% 2	660
September	1st to 10th	Night	9% 5% 26% 40% 18% 3	600
	11th to 20th	Night	11% 5% 30% 34% 18% 2	600
	21st to end	Night	11% 9% 32% 31% 16% 1	625
October	1st to 10th	Night	17% 7% 33% 30% 12% 1	800
	11th to 20th	Night	20% 10% 36% 27% 7% 1	800
	21st to end	Night	23% 11% 32% 27% 7%	880
November	1st to 10th	Night	15% 10% 35% 31% 8%	1020
	11th to 20th	Night	17% 13% 36% 26% 6% 1	1050
	21st to end	Night	17% 14% 36% 26% 7%	1050
December	1st to 10th	Night	14% 10% 39% 29% 8% 1	1050
	11th to 20th	Night	19% 11% 37% 26% 6% 1	1050
	21st to end	Night	24% 10% 33% 27% 5% 1	1155

Page generated at 2026-01-29 00:21:44. Version ac07

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