NAA Minooka
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the NAA Minooka clear sky chart from 2005-11-06 to 2024-05-13.

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% 9% 3 8% 5% 4 4 4 6% 7% 36%	83481
	Night	15% 10% 4 7% 4 4 4 3 5% 6% 38%	86081
Transparency	Day	46% 7% 12% 21% 12% 2	83182
	Night	46% 6% 12% 21% 13% 2	85901
Seeing	Day	16% 9% 27% 26% 16% 6%	15035
	Night	17% 9% 29% 31% 12% 1	25048

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	13% 13% 6% 13% 6% 5% 5% 4 4 5% 27%	2527
	11th to 20th	Day	13% 12% 4 15% 6% 6% 6% 6% 9% 5% 19%	2530
	21st to end	Day	19% 19% 9% 13% 6% 3 3 2 4 4 18%	2925
February	1st to 10th	Day	17% 14% 5% 7% 5% 5% 5% 4 5% 6% 27%	1733
	11th to 20th	Day	15% 10% 4 7% 7% 5% 4 3 4 6% 35%	1848
	21st to end	Day	15% 12% 6% 11% 4 4 3 3 5% 6% 30%	1570
March	1st to 10th	Day	17% 14% 3 7% 4 4 4 3 3 5% 35%	3120
	11th to 20th	Day	10% 7% 3 7% 4 4 5% 4 7% 8% 40%	3295
	21st to end	Day	20% 11% 5% 12% 6% 5% 5% 4 6% 6% 20%	4165
April	1st to 10th	Day	16% 13% 3 8% 5% 4 4 3 5% 7% 31%	2280
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 4 6% 6% 36%	2254
	21st to end	Day	21% 7% 3 8% 5% 5% 4 4 5% 6% 33%	2347
May	1st to 10th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	2470
	11th to 20th	Day	19% 9% 3 6% 5% 4 4 4 5% 7% 35%	2462
	21st to end	Day	14% 6% 3 8% 5% 4 5% 4 7% 8% 36%	2725
June	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 4 7% 7% 46%	2520
	11th to 20th	Day	8% 6% 2 6% 5% 4 5% 4 5% 7% 46%	2520
	21st to end	Day	10% 7% 2 7% 5% 6% 6% 5% 6% 8% 38%	2520
July	1st to 10th	Day	8% 4 2 5% 4 4 4 5% 7% 9% 46%	2520
	11th to 20th	Day	9% 4 2 4 4 4 5% 5% 6% 10% 47%	2520
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 5% 7% 10% 44%	2743
August	1st to 10th	Day	6% 6% 2 5% 5% 5% 5% 4 7% 11% 44%	2436
	11th to 20th	Day	8% 5% 2 7% 5% 6% 5% 5% 6% 10% 43%	2125
	21st to end	Day	9% 4 2 5% 4 4 5% 4 7% 9% 48%	2376
September	1st to 10th	Day	11% 6% 2 5% 4 4 4 4 6% 7% 47%	2160
	11th to 20th	Day	11% 5% 2 4 3 4 4 3 5% 7% 53%	2062
	21st to end	Day	9% 6% 3 7% 3 4 4 4 6% 8% 47%	1980
October	1st to 10th	Day	12% 6% 3 6% 4 4 5% 4 5% 7% 45%	1908
	11th to 20th	Day	17% 9% 3 6% 4 5% 5% 3 5% 7% 37%	1800
	21st to end	Day	18% 9% 3 7% 5% 3 4 3 5% 6% 37%	1800
November	1st to 10th	Day	11% 8% 2 6% 4 4 4 3 6% 6% 47%	1672
	11th to 20th	Day	16% 10% 3 9% 5% 4 4 3 5% 7% 33%	1710
	21st to end	Day	19% 10% 3 9% 4 4 3 3 5% 4 36%	1637
December	1st to 10th	Day	14% 12% 4 9% 6% 5% 5% 3 5% 7% 32%	1520
	11th to 20th	Day	14% 13% 4 9% 5% 5% 6% 4 5% 6% 29%	1918
	21st to end	Day	24% 19% 9% 13% 5% 4 3 2 3 4 14%	2783
January	1st to 10th	Night	15% 14% 7% 12% 5% 4 3 3 4 5% 29%	4428
	11th to 20th	Night	14% 18% 7% 12% 6% 4 4 4 6% 4 21%	4440
	21st to end	Night	22% 18% 7% 9% 5% 4 3 3 4 5% 21%	4726
February	1st to 10th	Night	16% 15% 5% 8% 5% 4 4 2 4 5% 32%	2446
	11th to 20th	Night	14% 10% 3 7% 6% 4 5% 4 4 6% 38%	2218
	21st to end	Night	18% 11% 4 9% 4 3 4 2 4 5% 36%	1884
March	1st to 10th	Night	18% 12% 3 5% 4 3 3 3 4 5% 40%	3733
	11th to 20th	Night	10% 6% 2 7% 5% 4 4 3 4 6% 48%	3695
	21st to end	Night	21% 11% 5% 10% 5% 5% 4 3 5% 5% 27%	3466
April	1st to 10th	Night	15% 11% 3 6% 5% 4 3 3 4 7% 39%	1900
	11th to 20th	Night	19% 8% 2 5% 4 4 3 3 4 6% 41%	1875
	21st to end	Night	18% 7% 3 7% 4 4 5% 4 6% 7% 35%	1831
May	1st to 10th	Night	16% 8% 3 6% 4 5% 4 3 7% 8% 35%	1710
	11th to 20th	Night	16% 5% 2 7% 4 4 5% 3 6% 9% 40%	1486
	21st to end	Night	12% 6% 3 5% 5% 5% 6% 4 6% 10% 39%	1551
June	1st to 10th	Night	9% 5% 2 6% 3 3 4 4 6% 7% 51%	1440
	11th to 20th	Night	8% 5% 2 6% 4 4 5% 4 7% 9% 46%	1440
	21st to end	Night	9% 6% 2 7% 4 5% 5% 5% 7% 7% 43%	1440
July	1st to 10th	Night	7% 4 2 6% 5% 4 4 4 7% 9% 49%	1440
	11th to 20th	Night	6% 3 2 4 5% 4 4 3 6% 8% 55%	1440
	21st to end	Night	4 3 2 5% 4 4 6% 5% 7% 9% 52%	1575
August	1st to 10th	Night	4 5% 2 5% 4 5% 4 4 8% 9% 50%	1497
	11th to 20th	Night	7% 4 2 4 3 3 4 4 5% 9% 53%	1776
	21st to end	Night	8% 3 2 5% 3 4 3 3 5% 8% 55%	1980
September	1st to 10th	Night	11% 6% 2 5% 3 3 2 2 4 7% 54%	1800
	11th to 20th	Night	9% 5% 2 5% 3 4 4 4 5% 7% 54%	1879
	21st to end	Night	9% 5% 3 5% 4 5% 4 4 6% 7% 48%	1980
October	1st to 10th	Night	10% 5% 3 6% 4 3 4 3 5% 7% 51%	2049
	11th to 20th	Night	18% 7% 2 5% 3 3 3 2 4 6% 47%	2160
	21st to end	Night	20% 8% 3 7% 4 3 3 2 4 6% 39%	2556
November	1st to 10th	Night	12% 8% 2 5% 3 3 3 3 5% 6% 50%	2406
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 3 6% 6% 38%	2470
	21st to end	Night	18% 9% 3 7% 4 4 4 3 4 5% 39%	2541
December	1st to 10th	Night	16% 11% 4 8% 5% 5% 4 3 5% 5% 33%	2660
	11th to 20th	Night	15% 13% 4 10% 5% 4 4 3 4 5% 33%	3279
	21st to end	Night	24% 17% 7% 10% 6% 5% 4 3 4 5% 16%	4884

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	59% 6% 12% 16% 6%	2528
	11th to 20th	Day	63% 7% 9% 12% 9% 1	2530
	21st to end	Day	69% 5% 8% 12% 5%	2925
February	1st to 10th	Day	57% 6% 12% 15% 8% 2	1733
	11th to 20th	Day	50% 5% 11% 23% 9% 2	1858
	21st to end	Day	55% 5% 11% 19% 7% 2	1570
March	1st to 10th	Day	50% 6% 11% 20% 11% 2	3120
	11th to 20th	Day	38% 8% 14% 28% 11% 1	3295
	21st to end	Day	61% 10% 13% 13% 2	4165
April	1st to 10th	Day	51% 7% 10% 21% 10%	2280
	11th to 20th	Day	46% 6% 11% 21% 12% 3	2254
	21st to end	Day	50% 7% 12% 16% 12% 2	2347
May	1st to 10th	Day	49% 8% 13% 22% 8%	2470
	11th to 20th	Day	48% 6% 10% 23% 11%	2466
	21st to end	Day	43% 8% 13% 19% 16% 2	2725
June	1st to 10th	Day	34% 7% 12% 27% 17% 2	2520
	11th to 20th	Day	35% 7% 12% 23% 21% 3	2520
	21st to end	Day	41% 9% 13% 21% 14% 2	2520
July	1st to 10th	Day	31% 8% 16% 27% 15% 3	2451
	11th to 20th	Day	31% 8% 17% 27% 15% 2	2445
	21st to end	Day	33% 9% 18% 24% 15% 2	2591
August	1st to 10th	Day	32% 8% 17% 29% 12% 2	2421
	11th to 20th	Day	35% 8% 15% 26% 16% 1	2125
	21st to end	Day	29% 9% 13% 26% 19% 3	2376
September	1st to 10th	Day	35% 8% 14% 22% 17% 5%	2160
	11th to 20th	Day	30% 5% 13% 28% 20% 4	2062
	21st to end	Day	34% 7% 11% 26% 20% 2	1980
October	1st to 10th	Day	37% 6% 12% 24% 19% 2	1908
	11th to 20th	Day	46% 6% 11% 22% 14% 2	1800
	21st to end	Day	47% 6% 12% 22% 10% 2	1800
November	1st to 10th	Day	37% 6% 15% 24% 17% 2	1672
	11th to 20th	Day	50% 5% 11% 22% 11% 1	1710
	21st to end	Day	52% 4 12% 23% 9%	1637
December	1st to 10th	Day	53% 5% 13% 19% 8% 1	1520
	11th to 20th	Day	54% 6% 12% 19% 8% 1	1915
	21st to end	Day	75% 5% 8% 9% 3	2783
January	1st to 10th	Night	56% 7% 11% 17% 9%	4428
	11th to 20th	Night	65% 5% 11% 12% 7%	4440
	21st to end	Night	66% 5% 10% 13% 6%	4726
February	1st to 10th	Night	55% 4 11% 18% 11% 2	2446
	11th to 20th	Night	47% 5% 10% 24% 12% 1	2219
	21st to end	Night	50% 6% 11% 19% 11% 3	1884
March	1st to 10th	Night	46% 6% 13% 22% 10% 3	3733
	11th to 20th	Night	36% 6% 11% 27% 17% 2	3695
	21st to end	Night	58% 7% 12% 18% 5% 1	3466
April	1st to 10th	Night	46% 5% 12% 22% 13% 2	1900
	11th to 20th	Night	44% 5% 9% 22% 16% 4	1875
	21st to end	Night	45% 8% 11% 21% 12% 3	1831
May	1st to 10th	Night	45% 7% 14% 23% 11% 1	1710
	11th to 20th	Night	40% 8% 13% 24% 14% 1	1487
	21st to end	Night	39% 9% 13% 20% 17% 2	1552
June	1st to 10th	Night	31% 7% 14% 25% 19% 4	1440
	11th to 20th	Night	33% 7% 12% 24% 22% 3	1440
	21st to end	Night	37% 9% 14% 21% 15% 3	1440
July	1st to 10th	Night	30% 8% 14% 26% 17% 5%	1400
	11th to 20th	Night	27% 7% 15% 27% 21% 3	1392
	21st to end	Night	25% 7% 17% 28% 19% 5%	1487
August	1st to 10th	Night	28% 8% 19% 27% 16% 2	1488
	11th to 20th	Night	27% 7% 17% 27% 21% 2	1776
	21st to end	Night	27% 7% 12% 29% 21% 5%	1980
September	1st to 10th	Night	31% 6% 11% 26% 22% 4	1800
	11th to 20th	Night	29% 5% 10% 29% 24% 3	1879
	21st to end	Night	33% 8% 12% 26% 18% 3	1980
October	1st to 10th	Night	34% 5% 10% 26% 22% 3	2049
	11th to 20th	Night	40% 4 10% 24% 20% 2	2160
	21st to end	Night	47% 4 10% 24% 14% 1	2556
November	1st to 10th	Night	36% 5% 10% 27% 18% 4	2406
	11th to 20th	Night	45% 6% 12% 22% 13% 2	2470
	21st to end	Night	48% 4 12% 24% 12% 1	2541
December	1st to 10th	Night	52% 5% 12% 21% 8% 1	2660
	11th to 20th	Night	53% 5% 12% 19% 10% 1	3281
	21st to end	Night	70% 6% 9% 11% 4	4884

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	23% 10% 31% 27% 9%	270
	11th to 20th	Day	22% 14% 36% 20% 6% 1	270
	21st to end	Day	25% 14% 27% 27% 7%	297
February	1st to 10th	Day	21% 17% 35% 21% 5%	270
	11th to 20th	Day	22% 15% 36% 22% 6%	270
	21st to end	Day	22% 14% 42% 17% 4	225
March	1st to 10th	Day	24% 20% 33% 21% 3	270
	11th to 20th	Day	24% 16% 32% 19% 7% 1	275
	21st to end	Day	28% 12% 33% 18% 7% 2	506
April	1st to 10th	Day	23% 13% 33% 24% 7% 1	460
	11th to 20th	Day	19% 19% 28% 19% 12% 2	452
	21st to end	Day	23% 12% 30% 23% 10% 2	460
May	1st to 10th	Day	21% 11% 29% 26% 10% 2	463
	11th to 20th	Day	21% 8% 29% 25% 12% 4	589
	21st to end	Day	15% 7% 29% 23% 18% 10%	679
June	1st to 10th	Day	10% 7% 27% 28% 22% 7%	630
	11th to 20th	Day	10% 6% 28% 30% 20% 6%	630
	21st to end	Day	13% 7% 30% 28% 17% 5%	630
July	1st to 10th	Day	10% 3 15% 27% 26% 18%	621
	11th to 20th	Day	12% 4 21% 31% 22% 10%	618
	21st to end	Day	7% 2 21% 35% 27% 8%	684
August	1st to 10th	Day	6% 3 14% 36% 27% 14%	590
	11th to 20th	Day	11% 5% 15% 27% 28% 15%	439
	21st to end	Day	7% 2 17% 32% 27% 15%	495
September	1st to 10th	Day	14% 5% 19% 26% 28% 7%	450
	11th to 20th	Day	10% 2 16% 31% 28% 13%	450
	21st to end	Day	11% 10% 24% 26% 22% 8%	450
October	1st to 10th	Day	14% 6% 28% 29% 18% 6%	378
	11th to 20th	Day	19% 20% 31% 23% 7% 1	270
	21st to end	Day	29% 12% 30% 22% 5% 1	297
November	1st to 10th	Day	12% 14% 36% 23% 10% 5%	270
	11th to 20th	Day	22% 17% 31% 20% 7% 3	270
	21st to end	Day	25% 11% 31% 24% 8%	270
December	1st to 10th	Day	19% 15% 37% 20% 8% 1	270
	11th to 20th	Day	17% 12% 38% 25% 8%	270
	21st to end	Day	27% 18% 35% 17% 3	297
January	1st to 10th	Night	20% 14% 36% 24% 6%	950
	11th to 20th	Night	22% 13% 36% 24% 5% 1	950
	21st to end	Night	22% 12% 33% 29% 4	1045
February	1st to 10th	Night	23% 11% 35% 26% 5% 1	926
	11th to 20th	Night	20% 12% 35% 28% 5%	743
	21st to end	Night	23% 12% 38% 24% 3	628
March	1st to 10th	Night	21% 15% 34% 25% 6%	760
	11th to 20th	Night	17% 11% 35% 30% 6% 1	712
	21st to end	Night	25% 10% 34% 24% 5% 1	627
April	1st to 10th	Night	19% 13% 36% 26% 6%	570
	11th to 20th	Night	21% 12% 33% 27% 7%	563
	21st to end	Night	20% 10% 34% 29% 7% 1	570
May	1st to 10th	Night	19% 7% 35% 31% 8% 1	570
	11th to 20th	Night	19% 5% 29% 35% 10% 1	540
	21st to end	Night	13% 5% 26% 37% 18% 1	584
June	1st to 10th	Night	11% 4 23% 45% 16% 1	540
	11th to 20th	Night	10% 4 25% 45% 14% 1	540
	21st to end	Night	10% 4 25% 41% 20% 1	540
July	1st to 10th	Night	8% 2 12% 42% 32% 4	525
	11th to 20th	Night	7% 2 19% 40% 28% 3	522
	21st to end	Night	4 3 14% 49% 29% 2	591
August	1st to 10th	Night	6% 1 11% 46% 31% 4	537
	11th to 20th	Night	6% 4 9% 42% 35% 3	534
	21st to end	Night	9% 1 15% 39% 33% 3	594
September	1st to 10th	Night	13% 3 16% 36% 29% 3	540
	11th to 20th	Night	9% 3 18% 37% 28% 5%	619
	21st to end	Night	12% 5% 23% 35% 22% 3	720
October	1st to 10th	Night	13% 6% 25% 36% 19% 1	720
	11th to 20th	Night	20% 12% 29% 28% 11%	720
	21st to end	Night	25% 11% 30% 26% 8%	792
November	1st to 10th	Night	16% 9% 38% 25% 11% 1	740
	11th to 20th	Night	20% 12% 33% 27% 7%	760
	21st to end	Night	22% 10% 34% 27% 7%	831
December	1st to 10th	Night	22% 9% 36% 26% 6%	950
	11th to 20th	Night	23% 10% 33% 28% 6%	950
	21st to end	Night	27% 14% 32% 24% 3	1045

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