Tinley Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tinley Park clear sky chart from 2005-11-06 to 2024-11-01.

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	13% 9% 3 7% 5% 4 4 4 6% 7% 37%	101216
	Night	14% 10% 4 8% 4 4 4 3 5% 6% 38%	97792
Transparency	Day	45% 7% 12% 22% 13% 2	101005
	Night	46% 6% 12% 21% 13% 2	97675
Seeing	Day	17% 12% 30% 24% 12% 5%	15773
	Night	18% 11% 30% 29% 11% 1	25602

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	14% 14% 7% 10% 5% 5% 5% 4 5% 6% 25%	2527
	11th to 20th	Day	14% 16% 6% 14% 6% 4 4 7% 7% 5% 18%	2530
	21st to end	Day	19% 26% 6% 9% 4 3 3 2 4 5% 18%	2847
February	1st to 10th	Day	16% 14% 5% 9% 6% 5% 4 4 5% 6% 26%	1778
	11th to 20th	Day	14% 12% 4 9% 6% 5% 3 3 5% 6% 34%	1848
	21st to end	Day	16% 14% 5% 10% 5% 4 4 4 6% 5% 29%	1570
March	1st to 10th	Day	17% 15% 4 6% 5% 4 3 3 5% 5% 34%	3120
	11th to 20th	Day	10% 7% 4 7% 6% 5% 5% 4 6% 8% 39%	3248
	21st to end	Day	18% 12% 7% 12% 6% 5% 5% 4 5% 6% 20%	4165
April	1st to 10th	Day	16% 13% 4 8% 5% 5% 4 3 5% 6% 31%	2280
	11th to 20th	Day	18% 9% 2 6% 5% 5% 4 4 5% 6% 35%	2254
	21st to end	Day	20% 8% 3 7% 5% 4 4 3 5% 6% 34%	2393
May	1st to 10th	Day	17% 8% 2 7% 5% 5% 5% 4 6% 8% 34%	4082
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 40%	4233
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 44%	4824
June	1st to 10th	Day	11% 5% 3 6% 4 4 5% 4 7% 8% 45%	2660
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 5% 6% 8% 46%	2660
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 5% 8% 9% 36%	2660
July	1st to 10th	Day	11% 8% 3 7% 6% 6% 5% 4 7% 9% 33%	4440
	11th to 20th	Day	7% 4 2 5% 5% 4 4 5% 6% 11% 47%	4440
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 7% 8% 41%	4813
August	1st to 10th	Day	7% 6% 2 6% 4 5% 4 4 6% 9% 45%	4277
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 10% 45%	3765
	21st to end	Day	6% 5% 2 5% 4 5% 5% 4 6% 10% 48%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 5% 8% 47%	2280
	11th to 20th	Day	11% 5% 1 4 4 4 4 3 6% 8% 51%	2142
	21st to end	Day	12% 6% 2 7% 4 3 4 4 6% 8% 43%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 4 4 4 4 6% 47%	2066
	11th to 20th	Day	18% 9% 3 6% 6% 5% 4 3 4 7% 37%	1876
	21st to end	Day	19% 10% 3 7% 5% 3 4 4 5% 7% 34%	1881
November	1st to 10th	Day	12% 9% 3 6% 3 3 3 3 6% 7% 46%	1672
	11th to 20th	Day	15% 11% 3 8% 4 4 5% 3 5% 7% 35%	1710
	21st to end	Day	18% 10% 3 9% 4 3 4 3 4 5% 35%	1684
December	1st to 10th	Day	15% 14% 4 9% 6% 4 5% 3 5% 5% 30%	1520
	11th to 20th	Day	12% 15% 5% 10% 5% 4 4 4 6% 5% 28%	1918
	21st to end	Day	21% 23% 7% 13% 6% 4 3 3 3 4 13%	2783
January	1st to 10th	Night	15% 15% 8% 11% 5% 4 3 3 4 4 28%	4428
	11th to 20th	Night	15% 19% 8% 12% 5% 4 5% 5% 6% 4 18%	4440
	21st to end	Night	23% 18% 7% 9% 5% 4 4 3 4 4 22%	4816
February	1st to 10th	Night	16% 15% 5% 8% 6% 5% 4 2 4 5% 31%	2399
	11th to 20th	Night	14% 12% 4 7% 5% 4 4 3 5% 6% 37%	2218
	21st to end	Night	19% 12% 4 8% 4 3 4 2 4 5% 34%	1884
March	1st to 10th	Night	17% 13% 3 6% 4 3 3 3 4 5% 39%	3733
	11th to 20th	Night	10% 7% 2 7% 4 5% 4 3 5% 6% 47%	3722
	21st to end	Night	19% 10% 6% 10% 6% 5% 4 3 4 5% 26%	3471
April	1st to 10th	Night	15% 10% 4 6% 4 4 3 4 4 8% 38%	1900
	11th to 20th	Night	19% 8% 2 6% 4 4 3 3 5% 5% 40%	1875
	21st to end	Night	17% 9% 3 7% 4 4 4 4 5% 6% 36%	1786
May	1st to 10th	Night	17% 7% 2 8% 5% 4 4 4 6% 8% 34%	2813
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 6% 8% 40%	2662
	21st to end	Night	10% 7% 2 7% 5% 4 4 4 6% 6% 44%	2743
June	1st to 10th	Night	9% 5% 2 6% 4 3 4 4 5% 8% 49%	1520
	11th to 20th	Night	8% 7% 2 4 5% 4 4 4 7% 9% 46%	1520
	21st to end	Night	10% 6% 3 5% 5% 5% 5% 4 5% 9% 42%	1520
July	1st to 10th	Night	10% 5% 2 7% 5% 6% 5% 4 6% 9% 40%	2530
	11th to 20th	Night	6% 5% 2 5% 4 4 3 4 6% 7% 54%	2530
	21st to end	Night	4 5% 2 6% 4 5% 5% 5% 8% 10% 45%	2750
August	1st to 10th	Night	6% 5% 2 6% 4 5% 5% 4 6% 9% 47%	2656
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 5% 8% 52%	3061
	21st to end	Night	8% 5% 2 5% 3 4 4 3 5% 10% 52%	3476
September	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 5% 6% 53%	1900
	11th to 20th	Night	8% 5% 1 4 3 4 4 3 5% 7% 55%	2018
	21st to end	Night	10% 5% 2 8% 4 4 4 4 6% 7% 45%	2090
October	1st to 10th	Night	11% 5% 2 5% 3 4 4 3 4 6% 52%	2112
	11th to 20th	Night	17% 7% 2 7% 3 3 3 2 4 6% 46%	2303
	21st to end	Night	20% 8% 3 7% 4 3 4 4 4 7% 37%	2717
November	1st to 10th	Night	12% 8% 2 6% 5% 3 3 3 5% 6% 47%	2413
	11th to 20th	Night	14% 9% 4 9% 5% 4 4 3 5% 7% 36%	2470
	21st to end	Night	18% 10% 3 7% 4 4 4 2 5% 6% 37%	2493
December	1st to 10th	Night	16% 11% 3 10% 6% 4 4 4 5% 7% 31%	2660
	11th to 20th	Night	15% 15% 5% 9% 5% 4 4 3 5% 5% 31%	3279
	21st to end	Night	23% 19% 6% 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% 7% 14% 14% 6%	2528
	11th to 20th	Day	66% 4 10% 12% 8%	2530
	21st to end	Day	71% 4 7% 13% 5%	2847
February	1st to 10th	Day	59% 5% 12% 14% 8% 2	1778
	11th to 20th	Day	52% 4 11% 22% 10% 2	1858
	21st to end	Day	56% 6% 10% 19% 6% 2	1570
March	1st to 10th	Day	52% 5% 10% 20% 10% 2	3120
	11th to 20th	Day	41% 6% 12% 28% 11% 1	3248
	21st to end	Day	63% 8% 13% 13% 3	4165
April	1st to 10th	Day	54% 6% 10% 19% 12%	2280
	11th to 20th	Day	48% 7% 10% 21% 11% 4	2254
	21st to end	Day	50% 6% 13% 18% 11% 2	2393
May	1st to 10th	Day	46% 8% 12% 24% 10%	4120
	11th to 20th	Day	40% 7% 12% 28% 12%	4237
	21st to end	Day	35% 7% 12% 21% 20% 4	4837
June	1st to 10th	Day	35% 7% 13% 24% 18% 2	2660
	11th to 20th	Day	34% 7% 12% 24% 20% 3	2660
	21st to end	Day	40% 10% 14% 20% 14% 2	2660
July	1st to 10th	Day	44% 8% 13% 20% 12% 2	4371
	11th to 20th	Day	29% 8% 17% 29% 16% 1	4365
	21st to end	Day	37% 10% 15% 17% 19% 2	4662
August	1st to 10th	Day	34% 8% 15% 28% 14% 1	4262
	11th to 20th	Day	32% 8% 12% 32% 15% 1	3802
	21st to end	Day	31% 7% 13% 27% 19% 3	4179
September	1st to 10th	Day	35% 6% 13% 24% 17% 4	2280
	11th to 20th	Day	31% 6% 12% 27% 21% 3	2142
	21st to end	Day	37% 8% 9% 25% 20% 1	2090
October	1st to 10th	Day	38% 5% 11% 26% 17% 2	2066
	11th to 20th	Day	47% 6% 10% 22% 14% 1	1876
	21st to end	Day	50% 5% 11% 22% 10% 2	1881
November	1st to 10th	Day	38% 5% 15% 24% 16% 2	1672
	11th to 20th	Day	49% 6% 13% 21% 12% 1	1710
	21st to end	Day	53% 5% 9% 22% 10%	1684
December	1st to 10th	Day	57% 5% 13% 18% 8% 1	1520
	11th to 20th	Day	56% 5% 11% 20% 7% 1	1915
	21st to end	Day	77% 4 7% 9% 3	2783
January	1st to 10th	Night	60% 5% 11% 15% 8% 1	4428
	11th to 20th	Night	68% 4 12% 11% 5%	4440
	21st to end	Night	67% 5% 9% 13% 6%	4816
February	1st to 10th	Night	57% 4 11% 17% 10% 2	2399
	11th to 20th	Night	48% 5% 10% 21% 14% 1	2219
	21st to end	Night	53% 5% 10% 18% 11% 3	1884
March	1st to 10th	Night	48% 5% 12% 23% 9% 3	3733
	11th to 20th	Night	37% 6% 11% 27% 17% 2	3722
	21st to end	Night	59% 6% 10% 18% 6% 1	3471
April	1st to 10th	Night	45% 5% 13% 23% 13% 2	1900
	11th to 20th	Night	45% 6% 8% 21% 16% 4	1875
	21st to end	Night	48% 7% 9% 20% 14% 2	1786
May	1st to 10th	Night	46% 6% 13% 21% 12% 2	2840
	11th to 20th	Night	40% 8% 15% 26% 10% 1	2663
	21st to end	Night	37% 8% 12% 17% 20% 6%	2751
June	1st to 10th	Night	33% 6% 12% 25% 20% 4	1520
	11th to 20th	Night	32% 6% 14% 23% 23% 2	1520
	21st to end	Night	38% 9% 13% 21% 16% 3	1520
July	1st to 10th	Night	40% 8% 15% 22% 11% 5%	2490
	11th to 20th	Night	26% 8% 13% 27% 24% 2	2482
	21st to end	Night	31% 9% 17% 19% 20% 4	2662
August	1st to 10th	Night	31% 9% 16% 27% 16% 1	2647
	11th to 20th	Night	30% 7% 14% 28% 20% 1	3090
	21st to end	Night	29% 6% 12% 32% 17% 3	3476
September	1st to 10th	Night	32% 5% 12% 25% 23% 3	1900
	11th to 20th	Night	28% 5% 9% 28% 27% 3	2018
	21st to end	Night	37% 6% 10% 28% 16% 2	2090
October	1st to 10th	Night	34% 5% 10% 27% 21% 2	2112
	11th to 20th	Night	41% 4 8% 25% 20% 2	2303
	21st to end	Night	47% 5% 11% 22% 14% 1	2717
November	1st to 10th	Night	38% 5% 10% 25% 19% 3	2413
	11th to 20th	Night	48% 5% 12% 22% 12% 2	2470
	21st to end	Night	49% 4 12% 23% 11%	2493
December	1st to 10th	Night	52% 6% 11% 20% 9% 1	2660
	11th to 20th	Night	55% 5% 12% 18% 10% 1	3281
	21st to end	Night	71% 5% 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% 14% 37% 21% 5%	270
	11th to 20th	Day	26% 19% 36% 13% 5% 1	270
	21st to end	Day	23% 19% 36% 18% 3 1	297
February	1st to 10th	Day	26% 19% 40% 13% 2	270
	11th to 20th	Day	29% 17% 35% 16% 3 1	270
	21st to end	Day	23% 24% 39% 12% 2	225
March	1st to 10th	Day	23% 25% 39% 11% 2	270
	11th to 20th	Day	26% 16% 35% 17% 6%	308
	21st to end	Day	30% 17% 28% 18% 6% 1	506
April	1st to 10th	Day	25% 16% 32% 20% 7%	460
	11th to 20th	Day	26% 18% 26% 20% 10% 1	452
	21st to end	Day	23% 18% 35% 15% 8% 2	460
May	1st to 10th	Day	23% 16% 29% 22% 7% 2	463
	11th to 20th	Day	21% 9% 32% 23% 11% 3	574
	21st to end	Day	14% 12% 31% 25% 12% 6%	734
June	1st to 10th	Day	12% 9% 32% 29% 12% 5%	680
	11th to 20th	Day	13% 7% 34% 27% 16% 3	680
	21st to end	Day	11% 12% 34% 26% 12% 4	680
July	1st to 10th	Day	9% 5% 25% 30% 17% 13%	671
	11th to 20th	Day	12% 5% 29% 29% 15% 10%	668
	21st to end	Day	8% 5% 27% 34% 19% 6%	739
August	1st to 10th	Day	7% 4 24% 32% 23% 11%	595
	11th to 20th	Day	9% 7% 19% 31% 23% 11%	479
	21st to end	Day	8% 2 19% 40% 21% 10%	539
September	1st to 10th	Day	14% 6% 23% 30% 21% 6%	490
	11th to 20th	Day	10% 4 19% 31% 25% 11%	490
	21st to end	Day	15% 10% 25% 25% 18% 7%	490
October	1st to 10th	Day	14% 10% 27% 27% 17% 4	466
	11th to 20th	Day	21% 21% 32% 17% 7% 1	300
	21st to end	Day	31% 12% 37% 15% 5%	330
November	1st to 10th	Day	16% 15% 38% 21% 7% 3	270
	11th to 20th	Day	27% 14% 36% 16% 6% 1	270
	21st to end	Day	25% 11% 41% 19% 3	270
December	1st to 10th	Day	19% 24% 37% 15% 5%	270
	11th to 20th	Day	19% 20% 40% 18% 4	270
	21st to end	Day	26% 22% 37% 13% 2	297
January	1st to 10th	Night	21% 18% 34% 24% 3	950
	11th to 20th	Night	23% 18% 34% 21% 4 1	950
	21st to end	Night	22% 15% 34% 25% 4	1045
February	1st to 10th	Night	24% 13% 37% 22% 3	879
	11th to 20th	Night	20% 16% 35% 25% 4	743
	21st to end	Night	26% 17% 34% 19% 4	628
March	1st to 10th	Night	22% 16% 36% 21% 5%	760
	11th to 20th	Night	16% 13% 39% 26% 6% 1	760
	21st to end	Night	25% 14% 30% 24% 7% 1	632
April	1st to 10th	Night	21% 13% 36% 24% 5% 1	570
	11th to 20th	Night	23% 12% 32% 24% 8% 1	563
	21st to end	Night	22% 10% 34% 26% 8%	570
May	1st to 10th	Night	19% 7% 35% 30% 9%	570
	11th to 20th	Night	19% 5% 29% 32% 14% 1	561
	21st to end	Night	13% 6% 26% 36% 18%	617
June	1st to 10th	Night	10% 5% 27% 43% 14% 1	570
	11th to 20th	Night	11% 4 31% 41% 13% 1	570
	21st to end	Night	11% 5% 28% 38% 18% 1	570
July	1st to 10th	Night	8% 3 20% 41% 24% 4	555
	11th to 20th	Night	9% 3 21% 37% 28% 3	552
	21st to end	Night	5% 3 19% 47% 25% 2	624
August	1st to 10th	Night	6% 2 12% 48% 28% 4	567
	11th to 20th	Night	9% 2 15% 38% 32% 4	564
	21st to end	Night	7% 2 20% 38% 30% 3	627
September	1st to 10th	Night	12% 4 18% 35% 27% 4	570
	11th to 20th	Night	9% 5% 18% 37% 27% 5%	688
	21st to end	Night	13% 7% 23% 33% 21% 3	760
October	1st to 10th	Night	13% 6% 26% 35% 18% 2	760
	11th to 20th	Night	20% 14% 30% 26% 9%	760
	21st to end	Night	26% 14% 29% 23% 8%	836
November	1st to 10th	Night	17% 13% 38% 21% 9% 1	743
	11th to 20th	Night	19% 19% 32% 24% 5% 1	760
	21st to end	Night	23% 12% 37% 21% 6%	783
December	1st to 10th	Night	23% 14% 37% 22% 4	950
	11th to 20th	Night	23% 15% 35% 23% 4	950
	21st to end	Night	30% 15% 33% 19% 2	1045

Page generated at 2024-10-29 10:20:48. Version ac07

Copyright © 2024 Attilla Danko.