Belvidere East KOA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Belvidere East KOA clear sky chart from 2005-11-06 to 2026-01-17.

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 6% 4 4 4 3 5% 7% 50%	136146
	Night	8% 6% 2 6% 4 4 4 4 5% 7% 49%	132944
Transparency	Day	34% 4 13% 28% 18% 3	130884
	Night	35% 4 13% 27% 18% 3	129213
Seeing	Day	12% 9% 30% 31% 15% 3	17542
	Night	11% 8% 34% 36% 10% 1	27583

By Month

Percentage Cloud Cover SW (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	6% 8% 5% 13% 8% 5% 4 3 5% 6% 37%	3718
	11th to 20th	Day	3 9% 4 11% 6% 6% 5% 4 6% 6% 39%	3688
	21st to end	Day	3 6% 4 10% 5% 4 4 3 5% 6% 50%	4004
February	1st to 10th	Day	9% 13% 4 8% 6% 6% 3 4 5% 6% 37%	1766
	11th to 20th	Day	8% 9% 4 9% 5% 5% 4 3 4 8% 43%	1949
	21st to end	Day	6% 9% 3 9% 5% 4 4 3 4 6% 46%	1650
March	1st to 10th	Day	6% 8% 2 7% 4 3 3 3 4 5% 55%	4500
	11th to 20th	Day	6% 6% 2 5% 3 3 3 3 5% 9% 56%	4794
	21st to end	Day	16% 11% 3 7% 4 4 4 4 6% 7% 33%	5729
April	1st to 10th	Day	15% 8% 2 6% 4 3 3 3 5% 8% 43%	2400
	11th to 20th	Day	16% 8% 2 6% 4 3 4 4 5% 7% 41%	2422
	21st to end	Day	16% 8% 2 5% 4 4 4 3 5% 6% 42%	2600
May	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 6% 7% 48%	5900
	11th to 20th	Day	16% 6% 2 5% 3 3 3 3 5% 6% 47%	6072
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 7% 41%	6925
June	1st to 10th	Day	10% 4 1 4 3 3 4 4 6% 8% 53%	2800
	11th to 20th	Day	8% 4 1 5% 4 4 5% 4 6% 9% 51%	2800
	21st to end	Day	5% 4 1 3 3 3 5% 4 6% 7% 58%	2800
July	1st to 10th	Day	7% 4 2 4 4 4 4 4 5% 8% 54%	6339
	11th to 20th	Day	8% 4 1 5% 3 3 4 3 5% 7% 56%	6340
	21st to end	Day	6% 3 1 4 3 4 4 4 6% 9% 55%	6903
August	1st to 10th	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	6018
	11th to 20th	Day	7% 4 1 5% 4 4 5% 3 6% 7% 55%	5821
	21st to end	Day	9% 4 2 4 3 3 3 4 5% 8% 56%	6036
September	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 6% 63%	2400
	11th to 20th	Day	9% 4 2 4 2 3 4 3 4 6% 59%	2216
	21st to end	Day	10% 3 1 3 2 3 3 3 4 6% 62%	2200
October	1st to 10th	Day	7% 4 1 3 2 2 2 2 3 5% 70%	3590
	11th to 20th	Day	8% 5% 2 6% 3 3 3 3 4 7% 57%	3092
	21st to end	Day	10% 7% 2 6% 4 4 4 4 6% 7% 46%	3190
November	1st to 10th	Day	8% 6% 2 6% 4 3 3 3 4 7% 53%	1853
	11th to 20th	Day	6% 7% 2 7% 4 3 4 3 5% 6% 53%	1890
	21st to end	Day	5% 9% 4 6% 4 4 4 4 5% 7% 48%	1843
December	1st to 10th	Day	5% 11% 4 10% 6% 4 4 3 5% 7% 42%	2700
	11th to 20th	Day	4 6% 3 8% 5% 5% 5% 4 5% 7% 49%	3106
	21st to end	Day	9% 11% 3 7% 5% 4 4 3 4 6% 43%	4092
January	1st to 10th	Night	7% 11% 4 13% 7% 5% 4 3 4 5% 36%	6467
	11th to 20th	Night	3 8% 4 10% 8% 7% 6% 4 5% 5% 41%	6425
	21st to end	Night	2 6% 3 9% 5% 4 4 3 5% 5% 54%	6974
February	1st to 10th	Night	9% 12% 4 9% 6% 5% 5% 3 5% 6% 37%	2650
	11th to 20th	Night	5% 9% 4 9% 6% 5% 5% 4 6% 7% 41%	2338
	21st to end	Night	8% 8% 2 7% 4 4 5% 3 5% 6% 48%	1980
March	1st to 10th	Night	9% 7% 3 6% 3 4 4 3 4 6% 49%	5374
	11th to 20th	Night	7% 6% 2 5% 4 4 4 3 6% 9% 51%	5173
	21st to end	Night	14% 11% 4 8% 5% 4 4 4 5% 8% 33%	5212
April	1st to 10th	Night	14% 8% 2 5% 4 4 4 3 5% 7% 44%	2000
	11th to 20th	Night	15% 8% 2 6% 4 3 4 3 5% 6% 44%	1924
	21st to end	Night	15% 7% 2 6% 5% 4 4 4 5% 6% 41%	1800
May	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 6% 8% 50%	4080
	11th to 20th	Night	14% 5% 1 5% 3 3 4 3 5% 8% 48%	3839
	21st to end	Night	20% 6% 2 5% 4 3 4 3 5% 6% 41%	3972
June	1st to 10th	Night	9% 4 2 4 3 3 4 4 6% 8% 53%	1600
	11th to 20th	Night	10% 5% 2 5% 5% 4 5% 4 6% 7% 48%	1600
	21st to end	Night	5% 3 1 4 3 5% 4 4 7% 8% 55%	1600
July	1st to 10th	Night	5% 3 1 4 3 3 5% 4 7% 10% 56%	3640
	11th to 20th	Night	6% 4 1 4 3 3 4 3 5% 8% 58%	3640
	21st to end	Night	6% 4 2 5% 3 4 4 4 7% 8% 52%	3970
August	1st to 10th	Night	6% 5% 1 6% 4 4 5% 4 7% 9% 50%	3794
	11th to 20th	Night	6% 4 2 6% 3 4 4 4 7% 9% 52%	4028
	21st to end	Night	9% 4 2 5% 4 5% 5% 4 6% 7% 50%	4937
September	1st to 10th	Night	7% 3 1 4 3 3 3 3 4 7% 63%	2000
	11th to 20th	Night	8% 4 1 4 3 3 4 3 5% 6% 59%	2182
	21st to end	Night	9% 4 2 4 3 3 3 3 4 6% 61%	2200
October	1st to 10th	Night	9% 3 1 3 2 2 2 2 3 4 70%	3590
	11th to 20th	Night	9% 4 2 4 2 3 4 3 4 7% 59%	4019
	21st to end	Night	9% 6% 2 5% 4 4 3 4 5% 8% 49%	4610
November	1st to 10th	Night	7% 6% 2 6% 4 4 4 5% 6% 7% 48%	2665
	11th to 20th	Night	6% 7% 2 6% 4 4 4 4 6% 6% 50%	2730
	21st to end	Night	5% 7% 3 5% 3 4 4 3 6% 8% 51%	2772
December	1st to 10th	Night	4 7% 3 7% 5% 5% 4 3 5% 6% 51%	4710
	11th to 20th	Night	4 7% 3 7% 5% 4 5% 4 7% 8% 46%	5321
	21st to end	Night	11% 9% 3 7% 5% 4 4 4 5% 7% 41%	7128

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	49% 4 15% 24% 8%	3719
	11th to 20th	Day	44% 5% 14% 20% 15% 2	3688
	21st to end	Day	36% 4 17% 28% 13% 2	4004
February	1st to 10th	Day	47% 5% 12% 21% 13% 2	1766
	11th to 20th	Day	42% 4 16% 20% 15% 4	1959
	21st to end	Day	40% 5% 14% 25% 13% 3	1650
March	1st to 10th	Day	33% 4 9% 29% 23% 3	4500
	11th to 20th	Day	26% 3 14% 35% 20% 1	4794
	21st to end	Day	50% 4 17% 20% 8%	5729
April	1st to 10th	Day	40% 5% 13% 28% 12% 2	2400
	11th to 20th	Day	42% 5% 12% 22% 16% 2	2425
	21st to end	Day	43% 4 13% 30% 10%	2600
May	1st to 10th	Day	33% 5% 10% 32% 18% 2	5900
	11th to 20th	Day	39% 4 13% 26% 16% 2	6076
	21st to end	Day	42% 5% 13% 26% 14% 1	6926
June	1st to 10th	Day	29% 5% 20% 29% 14% 3	2800
	11th to 20th	Day	29% 6% 18% 28% 17% 3	2800
	21st to end	Day	23% 5% 13% 32% 22% 5%	2800
July	1st to 10th	Day	28% 5% 13% 32% 20% 2	6271
	11th to 20th	Day	28% 5% 11% 27% 24% 5%	6265
	21st to end	Day	26% 5% 14% 26% 24% 5%	6705
August	1st to 10th	Day	27% 5% 16% 25% 22% 5%	4377
	11th to 20th	Day	31% 7% 14% 27% 18% 3	4210
	21st to end	Day	21% 4 13% 28% 24% 10%	4350
September	1st to 10th	Day	21% 4 10% 31% 27% 7%	2400
	11th to 20th	Day	27% 5% 11% 29% 24% 5%	2216
	21st to end	Day	26% 3 9% 33% 26% 4	2200
October	1st to 10th	Day	20% 3 8% 23% 33% 13%	3590
	11th to 20th	Day	29% 3 12% 34% 19% 3	3092
	21st to end	Day	37% 4 11% 29% 15% 3	3190
November	1st to 10th	Day	33% 3 13% 28% 18% 5%	1853
	11th to 20th	Day	32% 3 14% 28% 20% 4	1890
	21st to end	Day	36% 3 14% 30% 14% 3	1843
December	1st to 10th	Day	43% 3 14% 26% 13% 1	2700
	11th to 20th	Day	34% 5% 20% 29% 12% 1	3104
	21st to end	Day	43% 3 8% 36% 9% 1	4092
January	1st to 10th	Night	51% 4 11% 24% 10% 1	6467
	11th to 20th	Night	44% 4 15% 21% 14% 1	6425
	21st to end	Night	32% 4 17% 29% 17% 1	6974
February	1st to 10th	Night	48% 4 14% 21% 13% 1	2650
	11th to 20th	Night	41% 6% 12% 24% 14% 3	2338
	21st to end	Night	36% 4 14% 27% 14% 4	1980
March	1st to 10th	Night	36% 3 9% 27% 22% 2	5374
	11th to 20th	Night	30% 3 12% 33% 20% 1	5173
	21st to end	Night	49% 5% 14% 22% 9% 1	5212
April	1st to 10th	Night	40% 5% 15% 24% 14% 3	2000
	11th to 20th	Night	40% 5% 12% 22% 18% 3	1924
	21st to end	Night	43% 4 14% 26% 12% 1	1800
May	1st to 10th	Night	31% 5% 10% 28% 23% 2	4080
	11th to 20th	Night	35% 5% 11% 27% 19% 3	3840
	21st to end	Night	43% 5% 12% 26% 14%	3972
June	1st to 10th	Night	29% 5% 16% 31% 17% 3	1600
	11th to 20th	Night	34% 5% 17% 25% 16% 3	1600
	21st to end	Night	25% 5% 13% 33% 21% 4	1600
July	1st to 10th	Night	22% 5% 19% 31% 21% 2	3600
	11th to 20th	Night	24% 5% 14% 29% 23% 5%	3592
	21st to end	Night	29% 7% 16% 27% 17% 5%	3856
August	1st to 10th	Night	29% 6% 17% 25% 16% 6%	2759
	11th to 20th	Night	32% 5% 18% 24% 17% 3	2915
	21st to end	Night	27% 5% 11% 23% 27% 7%	3554
September	1st to 10th	Night	23% 3 10% 29% 26% 8%	2000
	11th to 20th	Night	26% 4 12% 28% 24% 6%	2182
	21st to end	Night	26% 3 8% 30% 27% 6%	2200
October	1st to 10th	Night	21% 2 7% 19% 36% 15%	3590
	11th to 20th	Night	27% 4 10% 34% 22% 4	4019
	21st to end	Night	34% 4 11% 26% 20% 5%	4610
November	1st to 10th	Night	33% 5% 11% 26% 20% 5%	2665
	11th to 20th	Night	34% 4 12% 26% 20% 5%	2730
	21st to end	Night	31% 5% 15% 30% 17% 2	2772
December	1st to 10th	Night	35% 3 16% 31% 15% 1	4710
	11th to 20th	Night	35% 4 18% 30% 11% 1	5322
	21st to end	Night	43% 4 10% 31% 11% 1	7128

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	9% 10% 32% 27% 17% 5%	330
	11th to 20th	Day	14% 11% 36% 26% 11% 2	318
	21st to end	Day	10% 13% 40% 25% 9% 2	330
February	1st to 10th	Day	13% 13% 43% 26% 5% 1	300
	11th to 20th	Day	13% 8% 42% 27% 8% 1	300
	21st to end	Day	12% 16% 33% 29% 8% 1	249
March	1st to 10th	Day	15% 9% 40% 24% 8% 4	300
	11th to 20th	Day	10% 12% 34% 29% 12% 2	300
	21st to end	Day	23% 14% 27% 23% 10% 3	440
April	1st to 10th	Day	19% 15% 34% 22% 9% 1	500
	11th to 20th	Day	23% 15% 32% 22% 7% 1	543
	21st to end	Day	20% 10% 30% 31% 9% 1	700
May	1st to 10th	Day	16% 10% 30% 28% 14% 3	703
	11th to 20th	Day	22% 8% 23% 29% 14% 4	725
	21st to end	Day	16% 10% 30% 28% 13% 3	789
June	1st to 10th	Day	8% 7% 27% 30% 19% 7%	730
	11th to 20th	Day	10% 9% 32% 31% 15% 2	730
	21st to end	Day	8% 7% 28% 36% 19% 2	730
July	1st to 10th	Day	6% 3 23% 40% 23% 5%	721
	11th to 20th	Day	7% 6% 26% 42% 18% 2	718
	21st to end	Day	5% 4 23% 44% 21% 4	794
August	1st to 10th	Day	7% 5% 23% 42% 22% 3	726
	11th to 20th	Day	7% 4 22% 40% 21% 5%	715
	21st to end	Day	8% 5% 25% 34% 23% 5%	609
September	1st to 10th	Day	8% 6% 26% 34% 22% 4	530
	11th to 20th	Day	11% 7% 23% 31% 21% 7%	346
	21st to end	Day	14% 8% 27% 28% 17% 5%	330
October	1st to 10th	Day	17% 7% 26% 23% 19% 8%	330
	11th to 20th	Day	18% 12% 34% 23% 12% 2	330
	21st to end	Day	15% 19% 29% 23% 11% 3	363
November	1st to 10th	Day	17% 9% 32% 29% 12% 2	330
	11th to 20th	Day	12% 13% 35% 25% 13% 2	330
	21st to end	Day	12% 10% 31% 31% 15% 2	330
December	1st to 10th	Day	15% 13% 39% 24% 8% 2	330
	11th to 20th	Day	11% 12% 44% 24% 10%	330
	21st to end	Day	16% 10% 37% 25% 11% 1	363
January	1st to 10th	Night	8% 10% 38% 33% 10% 2	1050
	11th to 20th	Night	10% 14% 35% 32% 7% 1	1031
	21st to end	Night	11% 10% 36% 34% 8% 1	1100
February	1st to 10th	Night	15% 10% 40% 28% 6%	950
	11th to 20th	Night	9% 8% 41% 34% 8%	784
	21st to end	Night	12% 7% 40% 33% 7% 1	660
March	1st to 10th	Night	13% 9% 35% 35% 8% 1	800
	11th to 20th	Night	11% 9% 36% 35% 7% 1	689
	21st to end	Night	18% 9% 34% 30% 9% 1	660
April	1st to 10th	Night	18% 8% 35% 34% 5%	600
	11th to 20th	Night	19% 12% 35% 31% 3	593
	21st to end	Night	18% 11% 31% 32% 8%	600
May	1st to 10th	Night	14% 5% 34% 32% 14% 1	600
	11th to 20th	Night	18% 5% 30% 34% 12% 1	591
	21st to end	Night	14% 8% 38% 30% 10%	650
June	1st to 10th	Night	9% 7% 29% 38% 17%	600
	11th to 20th	Night	10% 7% 38% 37% 8%	600
	21st to end	Night	7% 4 33% 43% 13%	600
July	1st to 10th	Night	5% 3 28% 44% 19% 1	585
	11th to 20th	Night	6% 3 30% 50% 12%	582
	21st to end	Night	5% 4 29% 49% 13%	657
August	1st to 10th	Night	4 4 28% 50% 14%	597
	11th to 20th	Night	6% 3 28% 48% 14% 1	594
	21st to end	Night	6% 3 29% 45% 17%	660
September	1st to 10th	Night	7% 4 27% 48% 14% 1	600
	11th to 20th	Night	8% 6% 32% 38% 16% 1	600
	21st to end	Night	10% 8% 32% 36% 14% 1	600
October	1st to 10th	Night	18% 6% 26% 38% 12% 1	600
	11th to 20th	Night	14% 7% 33% 34% 12%	870
	21st to end	Night	14% 8% 34% 33% 10% 1	1100
November	1st to 10th	Night	9% 8% 39% 34% 8% 1	1025
	11th to 20th	Night	10% 9% 36% 34% 9%	1050
	21st to end	Night	9% 8% 36% 36% 10%	1050
December	1st to 10th	Night	11% 10% 39% 32% 8%	1050
	11th to 20th	Night	10% 10% 37% 34% 9%	1050
	21st to end	Night	15% 10% 33% 32% 9%	1155

Page generated at 2026-01-13 23:14:31. Version ac07

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