East Central Community College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Central Community College clear sky chart from 2005-11-06 to 2024-11-12.

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% 6% 2 6% 5% 5% 5% 4 6% 7% 42%	100842
	Night	12% 7% 2 6% 4 4 4 4 6% 7% 45%	98297
Transparency	Day	40% 4 10% 20% 19% 7%	104625
	Night	37% 4 10% 19% 21% 9%	102654
Seeing	Day	15% 8% 21% 25% 21% 10%	14929
	Night	15% 7% 22% 29% 22% 5%	24584

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	16% 12% 2 6% 3 3 3 3 4 6% 41%	2783
	11th to 20th	Day	16% 7% 2 5% 3 3 3 3 4 5% 49%	2876
	21st to end	Day	23% 9% 2 5% 2 3 3 2 4 5% 42%	3476
February	1st to 10th	Day	17% 10% 4 6% 5% 3 3 4 4 6% 38%	1900
	11th to 20th	Day	20% 9% 3 6% 4 3 2 2 5% 5% 42%	1848
	21st to end	Day	16% 9% 3 8% 4 4 4 4 4 5% 39%	1570
March	1st to 10th	Day	23% 9% 3 7% 5% 5% 4 4 5% 5% 30%	3120
	11th to 20th	Day	16% 7% 2 6% 5% 5% 4 5% 6% 7% 38%	3411
	21st to end	Day	16% 7% 3 7% 5% 4 5% 4 5% 5% 40%	4119
April	1st to 10th	Day	12% 5% 3 6% 5% 5% 5% 3 6% 6% 45%	2280
	11th to 20th	Day	14% 8% 2 6% 4 4 4 3 5% 6% 44%	2254
	21st to end	Day	9% 5% 2 5% 5% 4 4 4 6% 8% 48%	2280
May	1st to 10th	Day	10% 6% 2 6% 5% 4 5% 4 7% 9% 42%	3765
	11th to 20th	Day	13% 6% 2 7% 6% 4 5% 4 5% 8% 40%	3886
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 5% 7% 10% 42%	4476
June	1st to 10th	Day	10% 6% 2 6% 7% 6% 6% 5% 7% 9% 36%	2470
	11th to 20th	Day	5% 5% 2 6% 6% 6% 7% 6% 8% 9% 41%	2651
	21st to end	Day	6% 5% 2 7% 6% 6% 7% 6% 9% 10% 37%	2660
July	1st to 10th	Day	6% 6% 3 9% 7% 8% 8% 7% 8% 10% 28%	4391
	11th to 20th	Day	8% 6% 2 8% 6% 6% 8% 7% 11% 11% 28%	4066
	21st to end	Day	9% 9% 4 11% 8% 8% 8% 6% 7% 9% 22%	4118
August	1st to 10th	Day	3 2 1 4 4 4 4 4 7% 8% 58%	3785
	11th to 20th	Day	4 3 2 6% 5% 6% 6% 5% 8% 10% 45%	3729
	21st to end	Day	8% 4 2 5% 5% 6% 6% 5% 6% 8% 45%	4180
September	1st to 10th	Day	10% 5% 2 8% 6% 5% 5% 5% 6% 7% 39%	2280
	11th to 20th	Day	13% 6% 2 7% 4 4 5% 3 5% 7% 43%	2168
	21st to end	Day	11% 4 2 4 4 4 5% 4 5% 7% 51%	2090
October	1st to 10th	Day	7% 5% 3 5% 3 4 3 3 4 5% 58%	2090
	11th to 20th	Day	9% 5% 2 4 4 4 3 3 6% 6% 55%	1905
	21st to end	Day	12% 5% 2 5% 3 3 3 2 3 6% 57%	2090
November	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 4 6% 53%	1833
	11th to 20th	Day	13% 6% 2 6% 3 2 4 3 4 5% 52%	1719
	21st to end	Day	14% 7% 2 5% 4 4 4 3 5% 6% 46%	1710
December	1st to 10th	Day	16% 8% 2 6% 4 4 3 3 5% 7% 40%	1710
	11th to 20th	Day	14% 10% 3 6% 4 5% 4 3 4 5% 43%	2153
	21st to end	Day	14% 9% 3 7% 5% 4 4 3 4 7% 41%	3000
January	1st to 10th	Night	18% 12% 2 4 4 3 3 3 5% 5% 42%	4168
	11th to 20th	Night	17% 7% 3 6% 3 3 3 3 4 4 48%	4086
	21st to end	Night	24% 12% 2 5% 3 2 2 2 2 3 43%	4180
February	1st to 10th	Night	18% 8% 3 6% 4 4 3 4 5% 5% 41%	2280
	11th to 20th	Night	21% 7% 3 5% 4 3 3 3 4 5% 43%	2218
	21st to end	Night	20% 8% 3 7% 4 4 4 3 4 6% 39%	1884
March	1st to 10th	Night	21% 13% 3 7% 3 3 3 3 4 5% 34%	3733
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 3 5% 7% 42%	3576
	21st to end	Night	17% 7% 3 6% 4 3 4 4 5% 6% 41%	3509
April	1st to 10th	Night	12% 6% 2 7% 5% 4 3 4 5% 6% 47%	1900
	11th to 20th	Night	13% 6% 2 5% 3 4 4 3 6% 6% 47%	1875
	21st to end	Night	8% 4 2 4 4 4 3 3 7% 7% 53%	1900
May	1st to 10th	Night	10% 5% 3 7% 4 4 4 3 5% 9% 47%	3130
	11th to 20th	Night	15% 6% 2 6% 4 4 3 3 6% 7% 43%	3003
	21st to end	Night	7% 5% 2 5% 5% 4 6% 5% 7% 11% 42%	3079
June	1st to 10th	Night	6% 5% 2 7% 5% 6% 6% 4 7% 11% 41%	1710
	11th to 20th	Night	4 4 1 4 5% 4 5% 6% 8% 10% 49%	1521
	21st to end	Night	4 5% 2 5% 6% 4 5% 6% 7% 12% 43%	1520
July	1st to 10th	Night	5% 6% 3 7% 7% 6% 6% 5% 10% 12% 34%	2559
	11th to 20th	Night	7% 6% 2 8% 5% 6% 7% 6% 10% 12% 31%	2898
	21st to end	Night	8% 9% 3 9% 6% 6% 6% 6% 8% 10% 29%	3435
August	1st to 10th	Night	2 2 1 3 3 4 4 4 7% 10% 59%	3144
	11th to 20th	Night	4 3 2 5% 5% 5% 5% 5% 7% 13% 47%	3100
	21st to end	Night	5% 4 2 6% 6% 5% 6% 5% 7% 8% 46%	3476
September	1st to 10th	Night	9% 5% 2 6% 5% 4 5% 4 7% 8% 44%	1900
	11th to 20th	Night	10% 7% 3 5% 4 5% 4 3 6% 6% 47%	1991
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 7% 52%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 4 3 6% 6% 59%	2090
	11th to 20th	Night	10% 4 2 5% 2 3 3 3 4 6% 56%	2270
	21st to end	Night	13% 6% 2 3 2 2 2 2 3 4 58%	2508
November	1st to 10th	Night	11% 4 2 4 3 3 4 3 4 5% 56%	2461
	11th to 20th	Night	12% 6% 2 4 4 3 3 3 4 6% 54%	2484
	21st to end	Night	14% 7% 2 5% 4 3 3 3 5% 6% 47%	2470
December	1st to 10th	Night	17% 7% 2 6% 4 3 3 3 5% 6% 44%	2470
	11th to 20th	Night	15% 8% 3 7% 4 3 3 2 5% 4 45%	3042
	21st to end	Night	17% 10% 2 6% 4 3 3 3 5% 7% 40%	4637

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	47% 1 3 19% 25% 5%	2784
	11th to 20th	Day	40% 1 5% 23% 24% 7%	2876
	21st to end	Day	47% 1 7% 15% 22% 8%	3476
February	1st to 10th	Day	49% 2 7% 17% 17% 9%	1900
	11th to 20th	Day	47% 1 5% 18% 21% 8%	1858
	21st to end	Day	48% 3 7% 16% 18% 9%	1570
March	1st to 10th	Day	57% 2 7% 11% 17% 6%	3120
	11th to 20th	Day	46% 2 6% 21% 17% 7%	3411
	21st to end	Day	47% 1 7% 17% 21% 7%	4119
April	1st to 10th	Day	40% 3 9% 20% 20% 8%	2280
	11th to 20th	Day	42% 2 6% 19% 24% 7%	2254
	21st to end	Day	34% 3 9% 25% 25% 4	2280
May	1st to 10th	Day	39% 2 12% 29% 16% 3	3800
	11th to 20th	Day	43% 3 11% 23% 19% 1	3890
	21st to end	Day	38% 3 14% 32% 13% 1	4489
June	1st to 10th	Day	42% 5% 13% 23% 14% 2	2470
	11th to 20th	Day	36% 6% 15% 24% 16% 3	2651
	21st to end	Day	39% 7% 15% 24% 13% 3	2660
July	1st to 10th	Day	45% 11% 17% 21% 6% 1	4323
	11th to 20th	Day	41% 12% 25% 18% 4 1	3997
	21st to end	Day	55% 9% 13% 17% 6%	3987
August	1st to 10th	Day	22% 5% 13% 30% 28% 2	3773
	11th to 20th	Day	30% 8% 18% 27% 14% 2	3765
	21st to end	Day	34% 9% 14% 20% 20% 3	4179
September	1st to 10th	Day	42% 5% 12% 18% 16% 7%	2280
	11th to 20th	Day	41% 5% 11% 17% 20% 6%	2168
	21st to end	Day	33% 4 10% 23% 22% 9%	2090
October	1st to 10th	Day	22% 3 6% 15% 28% 28%	3480
	11th to 20th	Day	19% 2 3 15% 33% 29%	3145
	21st to end	Day	23% 2 3 17% 37% 17%	3428
November	1st to 10th	Day	34% 2 6% 18% 28% 11%	1833
	11th to 20th	Day	35% 2 6% 16% 27% 14%	1719
	21st to end	Day	40% 3 7% 17% 23% 10%	1710
December	1st to 10th	Day	43% 3 9% 18% 19% 8%	1710
	11th to 20th	Day	47% 2 5% 15% 25% 6%	2150
	21st to end	Day	46% 1 4 22% 23% 3	3000
January	1st to 10th	Night	46% 1 4 14% 28% 7%	4168
	11th to 20th	Night	41% 1 5% 20% 22% 10%	4086
	21st to end	Night	49% 1 2 16% 25% 6%	4180
February	1st to 10th	Night	45% 3 6% 16% 21% 9%	2280
	11th to 20th	Night	45% 3 5% 16% 21% 11%	2219
	21st to end	Night	48% 3 5% 15% 17% 12%	1884
March	1st to 10th	Night	54% 1 6% 15% 15% 7%	3733
	11th to 20th	Night	43% 2 8% 20% 19% 8%	3576
	21st to end	Night	45% 2 8% 19% 20% 6%	3509
April	1st to 10th	Night	38% 4 10% 19% 20% 10%	1900
	11th to 20th	Night	37% 2 8% 20% 22% 10%	1875
	21st to end	Night	29% 3 10% 25% 27% 6%	1900
May	1st to 10th	Night	38% 2 11% 27% 19% 4	3160
	11th to 20th	Night	41% 3 11% 26% 17% 1	3004
	21st to end	Night	35% 4 14% 26% 18% 3	3087
June	1st to 10th	Night	37% 6% 15% 25% 14% 2	1710
	11th to 20th	Night	27% 7% 16% 31% 14% 5%	1521
	21st to end	Night	32% 8% 19% 23% 15% 3	1520
July	1st to 10th	Night	39% 12% 23% 18% 6% 2	2519
	11th to 20th	Night	38% 13% 26% 18% 4 1	2844
	21st to end	Night	47% 10% 18% 18% 5% 1	3325
August	1st to 10th	Night	17% 6% 18% 32% 25% 1	3132
	11th to 20th	Night	26% 9% 21% 28% 14% 2	3130
	21st to end	Night	33% 9% 16% 20% 18% 5%	3476
September	1st to 10th	Night	37% 6% 15% 18% 17% 7%	1900
	11th to 20th	Night	38% 5% 13% 17% 19% 8%	1991
	21st to end	Night	31% 4 8% 26% 22% 9%	2090
October	1st to 10th	Night	20% 3 7% 14% 25% 32%	3480
	11th to 20th	Night	19% 2 3 15% 28% 32%	3769
	21st to end	Night	21% 2 5% 15% 35% 22%	4120
November	1st to 10th	Night	31% 3 7% 17% 28% 14%	2461
	11th to 20th	Night	34% 2 6% 17% 28% 14%	2484
	21st to end	Night	39% 3 6% 21% 20% 12%	2470
December	1st to 10th	Night	41% 3 11% 17% 22% 6%	2470
	11th to 20th	Night	43% 2 6% 14% 29% 7%	3044
	21st to end	Night	46% 1 5% 16% 29% 4	4637

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% 19% 36% 16% 3 1	270
	11th to 20th	Day	25% 17% 34% 16% 7% 1	270
	21st to end	Day	25% 22% 35% 14% 3 1	297
February	1st to 10th	Day	26% 20% 33% 16% 5%	270
	11th to 20th	Day	33% 20% 31% 12% 3 1	270
	21st to end	Day	24% 28% 35% 12% 1	225
March	1st to 10th	Day	25% 20% 36% 14% 5%	270
	11th to 20th	Day	26% 19% 31% 20% 3	270
	21st to end	Day	22% 16% 32% 23% 7%	473
April	1st to 10th	Day	22% 13% 30% 24% 10% 1	460
	11th to 20th	Day	23% 14% 24% 26% 10% 2	452
	21st to end	Day	12% 11% 31% 29% 15% 2	460
May	1st to 10th	Day	15% 9% 24% 30% 16% 5%	463
	11th to 20th	Day	10% 5% 22% 33% 17% 11%	487
	21st to end	Day	9% 5% 22% 29% 21% 14%	529
June	1st to 10th	Day	14% 2 16% 29% 26% 13%	490
	11th to 20th	Day	6% 4 12% 32% 34% 13%	671
	21st to end	Day	8% 2 12% 31% 31% 16%	680
July	1st to 10th	Day	6% 3 8% 27% 38% 17%	671
	11th to 20th	Day	9% 2 6% 21% 38% 25%	640
	21st to end	Day	7% 3 6% 23% 38% 23%	532
August	1st to 10th	Day	7% 1 8% 22% 37% 26%	486
	11th to 20th	Day	8% 2 5% 23% 38% 25%	479
	21st to end	Day	14% 4 8% 22% 30% 22%	539
September	1st to 10th	Day	11% 1 9% 30% 32% 16%	490
	11th to 20th	Day	13% 3 12% 24% 31% 17%	490
	21st to end	Day	14% 3 13% 28% 31% 11%	490
October	1st to 10th	Day	8% 5% 23% 31% 25% 8%	490
	11th to 20th	Day	8% 8% 28% 35% 18% 4	305
	21st to end	Day	18% 10% 21% 33% 13% 5%	330
November	1st to 10th	Day	21% 8% 29% 28% 10% 5%	300
	11th to 20th	Day	20% 11% 36% 21% 12% 1	273
	21st to end	Day	15% 16% 36% 20% 10% 3	270
December	1st to 10th	Day	25% 12% 36% 19% 7% 1	270
	11th to 20th	Day	19% 14% 40% 21% 6%	270
	21st to end	Day	26% 15% 33% 22% 4 1	297
January	1st to 10th	Night	24% 13% 32% 25% 6%	950
	11th to 20th	Night	23% 14% 30% 26% 7%	929
	21st to end	Night	23% 13% 36% 25% 3	836
February	1st to 10th	Night	25% 11% 28% 31% 5%	760
	11th to 20th	Night	26% 14% 29% 26% 5%	743
	21st to end	Night	23% 17% 38% 21% 2	628
March	1st to 10th	Night	20% 14% 32% 27% 8%	760
	11th to 20th	Night	20% 10% 33% 28% 9%	627
	21st to end	Night	17% 10% 36% 25% 11%	627
April	1st to 10th	Night	17% 10% 33% 26% 13% 1	570
	11th to 20th	Night	16% 11% 32% 28% 13% 1	563
	21st to end	Night	11% 6% 32% 37% 13% 1	570
May	1st to 10th	Night	11% 5% 25% 38% 20% 2	570
	11th to 20th	Night	10% 2 20% 41% 24% 4	561
	21st to end	Night	8% 2 14% 35% 33% 8%	617
June	1st to 10th	Night	8% 2 11% 36% 38% 6%	570
	11th to 20th	Night	4 2 9% 27% 46% 11%	570
	21st to end	Night	6% 2 9% 27% 42% 13%	570
July	1st to 10th	Night	5% 2 4 26% 49% 14%	555
	11th to 20th	Night	6% 1 4 23% 48% 19%	552
	21st to end	Night	4 2 5% 26% 49% 14%	624
August	1st to 10th	Night	5% 1 3 22% 50% 20%	567
	11th to 20th	Night	7% 2 4 25% 47% 16%	564
	21st to end	Night	11% 1 7% 22% 43% 17%	627
September	1st to 10th	Night	13% 2 6% 31% 38% 11%	570
	11th to 20th	Night	13% 3 9% 27% 41% 7%	661
	21st to end	Night	10% 3 11% 33% 38% 5%	760
October	1st to 10th	Night	8% 3 18% 33% 33% 6%	760
	11th to 20th	Night	13% 5% 21% 35% 24% 3	760
	21st to end	Night	17% 6% 19% 34% 22% 2	836
November	1st to 10th	Night	13% 6% 20% 37% 20% 4	780
	11th to 20th	Night	16% 7% 28% 34% 15% 1	765
	21st to end	Night	18% 8% 25% 33% 15% 1	760
December	1st to 10th	Night	21% 10% 28% 30% 10%	760
	11th to 20th	Night	22% 8% 32% 28% 10%	760
	21st to end	Night	26% 12% 30% 27% 5%	902

Page generated at 2024-11-08 21:45:38. Version ac07

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