Starved Rock State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starved Rock State Park clear sky chart from 2005-11-06 to 2024-11-05.

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% 38%	101344
	Night	13% 10% 3 8% 4 4 4 3 5% 6% 39%	97742
Transparency	Day	43% 5% 12% 23% 14% 2	104909
	Night	44% 5% 12% 23% 15% 2	102318
Seeing	Day	17% 10% 28% 25% 15% 5%	15795
	Night	18% 10% 30% 30% 12% 1	25622

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	12% 12% 9% 13% 6% 5% 5% 3 5% 5% 25%	2527
	11th to 20th	Day	12% 12% 6% 14% 8% 6% 5% 6% 8% 4 18%	2530
	21st to end	Day	17% 22% 9% 13% 5% 3 3 3 4 5% 17%	2982
February	1st to 10th	Day	16% 14% 5% 9% 5% 5% 4 3 5% 5% 29%	1710
	11th to 20th	Day	14% 11% 4 8% 6% 5% 4 4 4 6% 34%	1848
	21st to end	Day	14% 14% 6% 10% 5% 4 4 3 4 5% 30%	1570
March	1st to 10th	Day	16% 15% 3 8% 4 3 3 3 4 4 36%	3120
	11th to 20th	Day	10% 7% 3 7% 5% 5% 5% 4 6% 8% 41%	3320
	21st to end	Day	20% 11% 5% 11% 5% 6% 5% 4 6% 6% 22%	4150
April	1st to 10th	Day	16% 13% 4 7% 4 4 4 3 5% 5% 34%	2280
	11th to 20th	Day	16% 10% 4 6% 5% 4 4 4 4 6% 38%	2254
	21st to end	Day	20% 8% 3 6% 4 4 5% 4 4 6% 34%	2321
May	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 8% 35%	4082
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 41%	4364
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 9% 44%	4824
June	1st to 10th	Day	10% 5% 2 5% 5% 4 5% 4 6% 9% 46%	2660
	11th to 20th	Day	8% 4 2 6% 5% 5% 5% 4 7% 9% 45%	2660
	21st to end	Day	10% 6% 2 7% 6% 6% 5% 4 6% 9% 39%	2660
July	1st to 10th	Day	9% 8% 3 7% 5% 5% 6% 5% 8% 10% 33%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 5% 6% 11% 49%	4440
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 9% 41%	4813
August	1st to 10th	Day	6% 5% 2 6% 4 5% 6% 4 7% 10% 44%	4254
	11th to 20th	Day	9% 6% 2 5% 5% 4 4 4 8% 10% 43%	3729
	21st to end	Day	6% 5% 2 6% 4 4 4 4 7% 9% 49%	4180
September	1st to 10th	Day	11% 4 2 6% 4 3 4 4 6% 7% 49%	2280
	11th to 20th	Day	11% 4 2 4 3 3 4 4 6% 7% 53%	2195
	21st to end	Day	9% 7% 3 6% 5% 5% 3 4 6% 7% 46%	2090
October	1st to 10th	Day	11% 7% 2 7% 4 3 3 3 6% 6% 48%	1984
	11th to 20th	Day	17% 7% 3 7% 4 4 4 3 4 5% 42%	1900
	21st to end	Day	19% 10% 2 6% 4 3 5% 3 4 7% 37%	1924
November	1st to 10th	Day	11% 8% 2 6% 3 4 3 3 6% 6% 47%	1708
	11th to 20th	Day	17% 10% 5% 8% 4 4 3 3 4 7% 35%	1710
	21st to end	Day	19% 11% 4 7% 4 4 3 3 4 5% 36%	1614
December	1st to 10th	Day	14% 13% 4 7% 6% 5% 4 3 4 6% 34%	1520
	11th to 20th	Day	13% 15% 3 10% 6% 5% 4 4 5% 5% 29%	1918
	21st to end	Day	24% 18% 9% 13% 5% 4 4 2 3 5% 14%	2783
January	1st to 10th	Night	15% 15% 6% 11% 4 4 3 3 4 5% 30%	4428
	11th to 20th	Night	13% 18% 7% 12% 6% 4 4 4 6% 4 21%	4440
	21st to end	Night	21% 18% 7% 10% 4 4 3 3 4 4 22%	4683
February	1st to 10th	Night	15% 13% 4 9% 6% 4 4 3 5% 6% 31%	2469
	11th to 20th	Night	13% 11% 3 7% 5% 4 4 3 6% 7% 37%	2218
	21st to end	Night	18% 11% 4 10% 4 4 4 2 4 6% 34%	1884
March	1st to 10th	Night	18% 12% 3 5% 4 4 4 2 4 5% 40%	3733
	11th to 20th	Night	11% 6% 3 7% 4 4 4 3 5% 6% 47%	3654
	21st to end	Night	21% 11% 5% 11% 5% 5% 4 4 4 5% 25%	3480
April	1st to 10th	Night	16% 11% 2 5% 5% 3 5% 3 5% 7% 38%	1900
	11th to 20th	Night	18% 8% 2 7% 4 3 3 3 4 6% 43%	1875
	21st to end	Night	18% 7% 2 7% 4 3 4 4 5% 8% 37%	1857
May	1st to 10th	Night	16% 9% 2 7% 5% 5% 5% 4 6% 8% 32%	2813
	11th to 20th	Night	13% 6% 3 6% 4 4 5% 4 7% 10% 39%	2524
	21st to end	Night	9% 7% 2 6% 4 5% 4 4 6% 8% 45%	2743
June	1st to 10th	Night	8% 5% 2 6% 4 3 4 4 6% 7% 50%	1520
	11th to 20th	Night	8% 5% 3 5% 5% 4 4 4 7% 9% 46%	1520
	21st to end	Night	8% 6% 3 7% 4 5% 5% 4 6% 8% 43%	1520
July	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	2530
	11th to 20th	Night	6% 3 2 5% 3 4 4 4 5% 7% 57%	2530
	21st to end	Night	4 5% 2 8% 5% 5% 6% 5% 8% 8% 45%	2750
August	1st to 10th	Night	5% 5% 2 6% 3 4 5% 4 7% 9% 51%	2666
	11th to 20th	Night	7% 4 1 6% 4 4 5% 4 7% 8% 50%	3100
	21st to end	Night	6% 4 2 6% 4 3 4 3 5% 10% 53%	3476
September	1st to 10th	Night	10% 6% 2 5% 4 3 3 2 4 7% 56%	1900
	11th to 20th	Night	9% 5% 2 4 3 3 5% 4 5% 7% 54%	1965
	21st to end	Night	9% 6% 3 6% 4 4 4 4 5% 8% 47%	2090
October	1st to 10th	Night	10% 5% 2 6% 3 4 3 3 5% 5% 54%	2194
	11th to 20th	Night	16% 7% 2 6% 3 3 3 2 4 6% 47%	2280
	21st to end	Night	19% 8% 3 6% 4 3 4 3 5% 6% 38%	2672
November	1st to 10th	Night	11% 7% 2 5% 4 3 4 3 5% 6% 50%	2470
	11th to 20th	Night	14% 10% 3 8% 5% 4 4 3 5% 6% 39%	2470
	21st to end	Night	17% 9% 4 7% 4 4 3 3 5% 6% 39%	2565
December	1st to 10th	Night	16% 11% 4 9% 6% 4 4 3 5% 5% 34%	2660
	11th to 20th	Night	15% 13% 4 10% 5% 3 3 3 4 5% 34%	3279
	21st to end	Night	22% 18% 7% 11% 6% 4 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	62% 4 11% 17% 6%	2528
	11th to 20th	Day	63% 6% 10% 12% 8% 1	2530
	21st to end	Day	70% 4 9% 12% 5%	2982
February	1st to 10th	Day	56% 5% 13% 16% 7% 2	1710
	11th to 20th	Day	50% 5% 11% 22% 10% 1	1858
	21st to end	Day	56% 4 10% 21% 7% 2	1570
March	1st to 10th	Day	50% 5% 11% 20% 12% 2	3120
	11th to 20th	Day	39% 6% 14% 27% 13% 1	3320
	21st to end	Day	61% 7% 15% 14% 3 1	4150
April	1st to 10th	Day	51% 5% 11% 21% 11%	2280
	11th to 20th	Day	47% 4 11% 23% 11% 3	2254
	21st to end	Day	49% 6% 12% 19% 12% 2	2321
May	1st to 10th	Day	44% 8% 13% 24% 12%	4120
	11th to 20th	Day	42% 6% 10% 30% 13%	4368
	21st to end	Day	34% 7% 12% 22% 19% 5%	4837
June	1st to 10th	Day	34% 7% 13% 27% 17% 3	2660
	11th to 20th	Day	33% 7% 11% 23% 22% 3	2660
	21st to end	Day	40% 7% 13% 23% 14% 3	2660
July	1st to 10th	Day	44% 6% 13% 24% 11% 2	4371
	11th to 20th	Day	28% 6% 16% 31% 18% 1	4365
	21st to end	Day	37% 7% 18% 18% 18% 2	4662
August	1st to 10th	Day	32% 6% 18% 30% 13% 1	4239
	11th to 20th	Day	34% 6% 14% 30% 16% 1	3765
	21st to end	Day	31% 6% 12% 31% 17% 3	4179
September	1st to 10th	Day	34% 6% 11% 25% 19% 5%	2280
	11th to 20th	Day	29% 4 12% 29% 22% 4	2195
	21st to end	Day	36% 5% 10% 28% 20% 2	2090
October	1st to 10th	Day	25% 3 7% 29% 35% 2	3296
	11th to 20th	Day	30% 3 10% 26% 29% 2	3140
	21st to end	Day	40% 4 9% 27% 16% 3	3149
November	1st to 10th	Day	36% 4 16% 25% 16% 3	1708
	11th to 20th	Day	50% 4 11% 23% 11% 1	1710
	21st to end	Day	51% 4 11% 23% 9%	1614
December	1st to 10th	Day	53% 4 13% 20% 9% 1	1520
	11th to 20th	Day	55% 5% 11% 20% 8% 1	1915
	21st to end	Day	75% 4 8% 9% 4	2783
January	1st to 10th	Night	56% 5% 12% 17% 9%	4428
	11th to 20th	Night	65% 4 12% 12% 8%	4440
	21st to end	Night	66% 4 10% 14% 6%	4683
February	1st to 10th	Night	54% 5% 10% 19% 11% 1	2469
	11th to 20th	Night	47% 4 12% 24% 13% 1	2219
	21st to end	Night	52% 4 9% 20% 11% 3	1884
March	1st to 10th	Night	47% 4 12% 23% 11% 2	3733
	11th to 20th	Night	37% 5% 11% 28% 18% 2	3654
	21st to end	Night	61% 5% 12% 17% 5% 1	3480
April	1st to 10th	Night	46% 5% 11% 22% 13% 2	1900
	11th to 20th	Night	43% 3 9% 24% 16% 5%	1875
	21st to end	Night	45% 5% 13% 22% 12% 3	1857
May	1st to 10th	Night	46% 6% 13% 19% 12% 2	2840
	11th to 20th	Night	38% 8% 18% 26% 11% 1	2525
	21st to end	Night	34% 8% 13% 21% 20% 4	2751
June	1st to 10th	Night	31% 6% 14% 26% 19% 4	1520
	11th to 20th	Night	33% 6% 12% 24% 23% 3	1520
	21st to end	Night	37% 8% 15% 21% 16% 3	1520
July	1st to 10th	Night	42% 6% 14% 21% 14% 3	2490
	11th to 20th	Night	26% 5% 13% 31% 23% 2	2482
	21st to end	Night	33% 9% 16% 19% 20% 4	2662
August	1st to 10th	Night	28% 6% 19% 27% 18% 1	2657
	11th to 20th	Night	30% 6% 16% 30% 17% 1	3130
	21st to end	Night	28% 5% 12% 34% 18% 3	3476
September	1st to 10th	Night	30% 5% 10% 27% 24% 5%	1900
	11th to 20th	Night	28% 5% 10% 28% 24% 4	1965
	21st to end	Night	33% 5% 12% 27% 19% 3	2090
October	1st to 10th	Night	23% 3 6% 34% 31% 4	3662
	11th to 20th	Night	30% 3 8% 23% 32% 3	3779
	21st to end	Night	40% 3 10% 24% 19% 4	4397
November	1st to 10th	Night	36% 4 10% 28% 18% 4	2470
	11th to 20th	Night	46% 4 11% 23% 14% 2	2470
	21st to end	Night	47% 4 11% 24% 12% 1	2565
December	1st to 10th	Night	53% 4 12% 22% 8% 1	2660
	11th to 20th	Night	53% 4 12% 21% 9% 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% 34% 20% 8% 1	270
	11th to 20th	Day	24% 17% 37% 15% 6% 1	270
	21st to end	Day	23% 17% 34% 19% 6%	297
February	1st to 10th	Day	21% 17% 40% 19% 4	270
	11th to 20th	Day	21% 19% 37% 19% 5%	270
	21st to end	Day	23% 21% 38% 15% 3	225
March	1st to 10th	Day	24% 21% 36% 16% 2 1	270
	11th to 20th	Day	28% 17% 36% 14% 6%	270
	21st to end	Day	29% 16% 32% 16% 5% 2	491
April	1st to 10th	Day	27% 12% 34% 19% 7% 1	460
	11th to 20th	Day	20% 20% 28% 20% 10% 2	452
	21st to end	Day	25% 13% 30% 22% 8% 2	460
May	1st to 10th	Day	20% 13% 34% 22% 9% 2	463
	11th to 20th	Day	21% 12% 27% 26% 11% 3	653
	21st to end	Day	16% 9% 29% 23% 14% 8%	734
June	1st to 10th	Day	10% 8% 28% 29% 19% 6%	680
	11th to 20th	Day	9% 5% 30% 33% 19% 4	680
	21st to end	Day	12% 9% 32% 29% 14% 5%	680
July	1st to 10th	Day	8% 5% 19% 30% 23% 15%	671
	11th to 20th	Day	10% 4 23% 31% 20% 12%	668
	21st to end	Day	7% 2 21% 35% 28% 7%	739
August	1st to 10th	Day	7% 3 19% 34% 26% 11%	661
	11th to 20th	Day	12% 4 16% 30% 27% 13%	479
	21st to end	Day	9% 3 17% 32% 30% 11%	539
September	1st to 10th	Day	14% 6% 17% 31% 27% 6%	490
	11th to 20th	Day	10% 4 17% 28% 28% 13%	490
	21st to end	Day	13% 11% 27% 22% 21% 7%	490
October	1st to 10th	Day	14% 8% 27% 29% 18% 4	384
	11th to 20th	Day	21% 19% 31% 21% 7% 1	300
	21st to end	Day	32% 13% 28% 22% 4 1	330
November	1st to 10th	Day	16% 13% 40% 19% 8% 4	282
	11th to 20th	Day	26% 16% 33% 19% 5% 2	270
	21st to end	Day	27% 7% 39% 22% 5%	270
December	1st to 10th	Day	19% 17% 37% 18% 7% 2	270
	11th to 20th	Day	19% 14% 39% 25% 4	270
	21st to end	Day	29% 20% 36% 13% 2	297
January	1st to 10th	Night	20% 14% 37% 24% 5% 1	950
	11th to 20th	Night	22% 15% 36% 21% 5%	950
	21st to end	Night	22% 12% 34% 27% 5%	1045
February	1st to 10th	Night	23% 12% 36% 24% 4	949
	11th to 20th	Night	18% 15% 37% 25% 4	743
	21st to end	Night	23% 15% 36% 22% 3	628
March	1st to 10th	Night	23% 14% 34% 23% 6%	760
	11th to 20th	Night	18% 12% 35% 30% 5% 1	679
	21st to end	Night	27% 11% 34% 22% 6% 1	627
April	1st to 10th	Night	22% 12% 36% 25% 5%	570
	11th to 20th	Night	23% 12% 31% 28% 6%	563
	21st to end	Night	22% 11% 32% 27% 8%	570
May	1st to 10th	Night	19% 9% 36% 28% 7% 1	570
	11th to 20th	Night	17% 7% 32% 33% 11%	561
	21st to end	Night	13% 6% 28% 36% 16% 1	617
June	1st to 10th	Night	10% 4 26% 45% 14% 1	570
	11th to 20th	Night	10% 5% 26% 42% 16%	570
	21st to end	Night	10% 4 28% 39% 18% 1	570
July	1st to 10th	Night	8% 2 15% 39% 32% 5%	555
	11th to 20th	Night	8% 3 19% 39% 27% 3	552
	21st to end	Night	4 2 15% 49% 28% 2	624
August	1st to 10th	Night	6% 2 14% 43% 30% 4	567
	11th to 20th	Night	9% 2 11% 41% 32% 4	564
	21st to end	Night	8% 2 16% 41% 30% 3	627
September	1st to 10th	Night	13% 4 16% 36% 28% 2	570
	11th to 20th	Night	10% 3 18% 36% 30% 3	635
	21st to end	Night	12% 7% 24% 34% 21% 2	760
October	1st to 10th	Night	11% 7% 26% 35% 18% 2	760
	11th to 20th	Night	21% 12% 29% 26% 11%	760
	21st to end	Night	22% 12% 32% 25% 8%	836
November	1st to 10th	Night	14% 11% 38% 25% 11% 1	760
	11th to 20th	Night	21% 13% 34% 25% 7% 1	760
	21st to end	Night	22% 11% 34% 27% 6%	855
December	1st to 10th	Night	22% 12% 35% 25% 6%	950
	11th to 20th	Night	23% 11% 33% 27% 5% 1	950
	21st to end	Night	29% 15% 32% 21% 3	1045

Page generated at 2024-11-03 01:11:10. Version ac07

Copyright © 2024 Attilla Danko.