Shiloh Station Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shiloh Station Road clear sky chart from 2005-11-06 to 2026-06-16.

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% 7% 3 7% 4 4 4 4 6% 8% 42%	137555
	Night	13% 7% 3 7% 4 4 4 3 5% 7% 43%	134723
Transparency	Day	39% 6% 11% 25% 17% 2	141133
	Night	40% 5% 11% 24% 18% 3	139226
Seeing	Day	15% 9% 25% 26% 18% 7%	17771
	Night	16% 8% 29% 31% 14% 2	27615

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% 10% 4 11% 6% 4 4 3 5% 6% 34%	4691
	11th to 20th	Day	8% 7% 3 8% 6% 7% 4 3 5% 7% 42%	4992
	21st to end	Day	16% 14% 4 7% 4 4 4 3 4 5% 35%	5812
February	1st to 10th	Day	15% 11% 5% 7% 4 4 4 4 5% 6% 36%	1914
	11th to 20th	Day	16% 9% 3 8% 6% 3 4 3 5% 6% 37%	2048
	21st to end	Day	14% 9% 3 7% 4 4 5% 4 5% 6% 40%	1730
March	1st to 10th	Day	17% 10% 3 5% 3 3 3 2 3 4 47%	4580
	11th to 20th	Day	10% 8% 2 5% 3 3 4 3 5% 7% 51%	5061
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 6% 8% 38%	5952
April	1st to 10th	Day	13% 7% 2 6% 5% 5% 4 4 6% 6% 42%	2520
	11th to 20th	Day	16% 7% 3 6% 5% 4 4 3 4 6% 42%	2494
	21st to end	Day	16% 8% 2 7% 5% 4 4 4 5% 6% 39%	2520
May	1st to 10th	Day	15% 7% 3 8% 5% 5% 5% 4 7% 10% 32%	7309
	11th to 20th	Day	15% 7% 3 6% 4 4 5% 3 5% 8% 39%	7978
	21st to end	Day	16% 8% 3 8% 5% 5% 5% 5% 6% 7% 33%	9047
June	1st to 10th	Day	9% 4 2 6% 4 4 5% 4 6% 9% 47%	2940
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 6% 10% 50%	2871
	21st to end	Day	5% 4 1 6% 5% 5% 5% 5% 7% 10% 48%	2800
July	1st to 10th	Day	10% 4 2 5% 4 4 5% 4 6% 9% 46%	6360
	11th to 20th	Day	6% 4 2 7% 4 6% 6% 6% 8% 11% 40%	6360
	21st to end	Day	6% 5% 2 7% 5% 5% 6% 5% 7% 11% 40%	6681
August	1st to 10th	Day	4 4 2 5% 4 3 4 4 7% 10% 52%	4145
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 7% 10% 44%	3849
	21st to end	Day	5% 5% 2 5% 4 4 4 4 6% 9% 52%	4312
September	1st to 10th	Day	13% 4 2 5% 4 4 3 4 5% 7% 49%	2400
	11th to 20th	Day	8% 6% 2 5% 4 4 4 4 6% 8% 50%	2346
	21st to end	Day	9% 4 2 5% 3 5% 4 4 5% 8% 51%	2200
October	1st to 10th	Day	9% 4 2 5% 3 4 3 3 5% 6% 57%	2043
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 4 7% 52%	2000
	21st to end	Day	18% 6% 2 6% 3 3 3 2 5% 4 48%	2146
November	1st to 10th	Day	10% 5% 2 4 4 4 3 3 4 6% 55%	1852
	11th to 20th	Day	15% 7% 2 6% 4 3 3 3 5% 6% 46%	1890
	21st to end	Day	16% 10% 3 7% 4 4 3 3 4 6% 41%	1864
December	1st to 10th	Day	9% 10% 3 5% 3 3 3 3 5% 6% 50%	2690
	11th to 20th	Day	14% 8% 4 8% 5% 4 4 4 5% 5% 39%	3088
	21st to end	Day	24% 16% 5% 9% 4 4 4 3 4 4 24%	4070
January	1st to 10th	Night	14% 9% 4 10% 5% 4 4 3 5% 5% 38%	8232
	11th to 20th	Night	10% 9% 3 8% 5% 6% 5% 3 4 5% 42%	7983
	21st to end	Night	17% 11% 4 8% 5% 4 4 3 5% 5% 35%	8402
February	1st to 10th	Night	16% 9% 4 9% 5% 4 4 4 4 5% 36%	2704
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 2 5% 6% 41%	2458
	21st to end	Night	16% 7% 3 7% 5% 4 4 3 5% 5% 41%	2076
March	1st to 10th	Night	18% 10% 3 5% 4 3 3 3 4 5% 41%	5493
	11th to 20th	Night	11% 7% 2 5% 3 3 4 3 5% 6% 50%	5149
	21st to end	Night	17% 8% 3 8% 5% 5% 5% 4 6% 6% 36%	5218
April	1st to 10th	Night	13% 6% 2 6% 5% 4 4 3 5% 6% 46%	2100
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 6% 6% 45%	2075
	21st to end	Night	18% 8% 2 6% 4 4 3 3 5% 6% 41%	2100
May	1st to 10th	Night	16% 7% 2 8% 4 5% 5% 4 6% 9% 34%	5540
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	4898
	21st to end	Night	14% 8% 3 9% 6% 5% 5% 4 7% 7% 33%	5139
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 6% 8% 48%	1680
	11th to 20th	Night	5% 4 2 4 4 5% 4 3 5% 8% 55%	1640
	21st to end	Night	5% 4 1 4 4 4 5% 4 6% 9% 54%	1600
July	1st to 10th	Night	10% 5% 2 6% 3 3 3 3 6% 9% 49%	3618
	11th to 20th	Night	5% 4 2 7% 5% 4 6% 4 6% 9% 47%	3617
	21st to end	Night	7% 5% 2 7% 5% 5% 6% 4 9% 11% 39%	4173
August	1st to 10th	Night	5% 3 2 5% 4 3 4 4 5% 8% 58%	3010
	11th to 20th	Night	9% 5% 2 6% 4 5% 4 4 6% 7% 48%	3200
	21st to end	Night	6% 3 2 4 3 4 4 3 5% 9% 59%	3586
September	1st to 10th	Night	12% 4 2 5% 4 3 4 3 5% 6% 53%	2000
	11th to 20th	Night	8% 4 2 6% 4 4 3 4 6% 8% 51%	2032
	21st to end	Night	10% 4 1 4 4 4 4 4 5% 7% 53%	2200
October	1st to 10th	Night	7% 4 2 5% 3 3 3 2 4 6% 60%	2353
	11th to 20th	Night	13% 5% 2 5% 2 2 3 2 4 7% 56%	2400
	21st to end	Night	18% 7% 2 5% 3 3 3 3 3 5% 47%	2691
November	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 4 6% 55%	2666
	11th to 20th	Night	14% 4 2 5% 4 3 4 3 4 6% 49%	2730
	21st to end	Night	18% 9% 3 6% 3 3 3 3 4 6% 43%	2751
December	1st to 10th	Night	14% 8% 3 6% 4 3 4 3 5% 6% 45%	4720
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 5% 6% 43%	5339
	21st to end	Night	25% 14% 5% 8% 4 4 4 3 4 5% 23%	7150

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	50% 6% 11% 24% 8% 1	4692
	11th to 20th	Day	41% 4 10% 27% 15% 3	4992
	21st to end	Day	52% 3 10% 17% 13% 4	5812
February	1st to 10th	Day	48% 4 13% 24% 10% 1	1914
	11th to 20th	Day	48% 5% 9% 21% 13% 3	2058
	21st to end	Day	45% 5% 9% 22% 15% 3	1730
March	1st to 10th	Day	42% 3 6% 23% 23% 3	4580
	11th to 20th	Day	33% 4 9% 28% 21% 5%	5061
	21st to end	Day	42% 7% 14% 27% 9% 1	5954
April	1st to 10th	Day	40% 5% 13% 25% 16% 1	2520
	11th to 20th	Day	45% 4 11% 24% 14% 3	2494
	21st to end	Day	44% 6% 12% 25% 12% 1	2520
May	1st to 10th	Day	45% 8% 13% 22% 11%	7344
	11th to 20th	Day	43% 7% 10% 23% 16% 1	7982
	21st to end	Day	48% 7% 10% 19% 15% 1	9061
June	1st to 10th	Day	33% 8% 13% 27% 17% 3	2940
	11th to 20th	Day	29% 7% 13% 25% 23% 3	2871
	21st to end	Day	28% 8% 18% 24% 16% 5%	2800
July	1st to 10th	Day	33% 7% 10% 30% 18% 2	6291
	11th to 20th	Day	34% 9% 15% 27% 13% 2	6285
	21st to end	Day	35% 9% 16% 29% 11% 1	6491
August	1st to 10th	Day	25% 7% 14% 38% 15%	4131
	11th to 20th	Day	35% 6% 14% 26% 18% 1	3885
	21st to end	Day	29% 6% 13% 34% 16% 3	4311
September	1st to 10th	Day	33% 6% 11% 26% 20% 5%	2400
	11th to 20th	Day	32% 7% 9% 26% 24% 3	2346
	21st to end	Day	30% 6% 9% 27% 25% 3	2200
October	1st to 10th	Day	18% 3 5% 21% 43% 9%	3329
	11th to 20th	Day	23% 3 8% 21% 37% 8%	3240
	21st to end	Day	32% 3 7% 27% 28% 4	3448
November	1st to 10th	Day	31% 4 12% 29% 20% 5%	1852
	11th to 20th	Day	38% 5% 10% 23% 19% 6%	1890
	21st to end	Day	46% 4 9% 25% 15% 1	1864
December	1st to 10th	Day	36% 4 14% 30% 16%	2690
	11th to 20th	Day	46% 5% 11% 23% 14% 2	3085
	21st to end	Day	65% 4 12% 12% 6% 1	4070
January	1st to 10th	Night	48% 4 14% 25% 8%	8233
	11th to 20th	Night	44% 3 7% 23% 19% 3	7983
	21st to end	Night	51% 3 11% 18% 15% 1	8402
February	1st to 10th	Night	50% 5% 11% 22% 11% 1	2704
	11th to 20th	Night	45% 4 10% 22% 17% 2	2459
	21st to end	Night	44% 4 11% 23% 14% 4	2076
March	1st to 10th	Night	46% 4 7% 21% 21% 2	5493
	11th to 20th	Night	35% 4 10% 23% 22% 5%	5149
	21st to end	Night	47% 7% 10% 24% 11% 1	5218
April	1st to 10th	Night	37% 5% 11% 26% 17% 3	2100
	11th to 20th	Night	38% 6% 11% 23% 18% 4	2075
	21st to end	Night	45% 5% 9% 24% 15% 2	2100
May	1st to 10th	Night	45% 8% 15% 21% 10% 1	5570
	11th to 20th	Night	37% 7% 13% 25% 17% 1	4899
	21st to end	Night	48% 7% 11% 19% 13% 2	5149
June	1st to 10th	Night	32% 7% 13% 25% 18% 4	1680
	11th to 20th	Night	26% 7% 13% 26% 25% 4	1640
	21st to end	Night	25% 7% 17% 27% 18% 7%	1600
July	1st to 10th	Night	33% 6% 10% 28% 21% 3	3580
	11th to 20th	Night	31% 8% 15% 30% 13% 2	3572
	21st to end	Night	35% 9% 18% 26% 11% 1	4053
August	1st to 10th	Night	23% 7% 16% 35% 18% 1	3000
	11th to 20th	Night	34% 6% 14% 23% 21% 2	3230
	21st to end	Night	23% 5% 14% 35% 20% 3	3586
September	1st to 10th	Night	32% 5% 9% 27% 21% 6%	2000
	11th to 20th	Night	30% 6% 8% 27% 24% 5%	2032
	21st to end	Night	30% 6% 9% 22% 28% 6%	2200
October	1st to 10th	Night	17% 3 6% 18% 47% 9%	3847
	11th to 20th	Night	21% 3 8% 22% 40% 6%	3899
	21st to end	Night	32% 3 9% 24% 26% 6%	4339
November	1st to 10th	Night	31% 5% 11% 25% 23% 6%	2666
	11th to 20th	Night	35% 4 10% 24% 23% 4	2730
	21st to end	Night	44% 4 10% 23% 18% 2	2751
December	1st to 10th	Night	40% 4 10% 30% 15% 1	4720
	11th to 20th	Night	42% 4 13% 22% 18%	5341
	21st to end	Night	62% 5% 12% 14% 6% 1	7150

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	20% 18% 33% 21% 7% 1	330
	11th to 20th	Day	24% 20% 36% 17% 2	330
	21st to end	Day	19% 17% 42% 17% 5%	363
February	1st to 10th	Day	24% 14% 40% 18% 4	330
	11th to 20th	Day	27% 18% 33% 16% 4 1	330
	21st to end	Day	23% 19% 36% 19% 3	273
March	1st to 10th	Day	18% 18% 43% 17% 4	330
	11th to 20th	Day	26% 17% 37% 14% 5% 1	330
	21st to end	Day	26% 15% 34% 19% 5% 1	525
April	1st to 10th	Day	18% 16% 34% 24% 8% 1	540
	11th to 20th	Day	20% 18% 30% 20% 11% 1	532
	21st to end	Day	19% 14% 33% 21% 11% 1	540
May	1st to 10th	Day	17% 13% 32% 26% 10% 2	543
	11th to 20th	Day	17% 9% 25% 28% 17% 5%	685
	21st to end	Day	13% 5% 27% 31% 17% 7%	844
June	1st to 10th	Day	10% 5% 22% 27% 26% 10%	780
	11th to 20th	Day	8% 4 18% 36% 25% 9%	756
	21st to end	Day	5% 4 24% 35% 24% 8%	730
July	1st to 10th	Day	10% 2 13% 27% 28% 19%	721
	11th to 20th	Day	6% 3 12% 36% 31% 12%	718
	21st to end	Day	9% 3 12% 32% 33% 12%	794
August	1st to 10th	Day	7% 2 12% 34% 31% 13%	676
	11th to 20th	Day	11% 2 13% 28% 32% 15%	519
	21st to end	Day	10% 1 11% 25% 38% 15%	583
September	1st to 10th	Day	12% 2 15% 28% 29% 14%	530
	11th to 20th	Day	8% 2 10% 28% 36% 16%	530
	21st to end	Day	10% 7% 20% 26% 26% 10%	530
October	1st to 10th	Day	11% 4 22% 36% 20% 7%	373
	11th to 20th	Day	15% 12% 31% 27% 12% 3	330
	21st to end	Day	26% 18% 26% 21% 9%	363
November	1st to 10th	Day	12% 12% 34% 25% 12% 5%	330
	11th to 20th	Day	18% 17% 33% 21% 8% 2	330
	21st to end	Day	25% 15% 29% 21% 9% 2	330
December	1st to 10th	Day	13% 19% 39% 18% 6% 4	330
	11th to 20th	Day	20% 17% 34% 24% 4 1	330
	21st to end	Day	27% 16% 38% 15% 4	363
January	1st to 10th	Night	17% 15% 38% 26% 4	1050
	11th to 20th	Night	21% 16% 37% 22% 5%	1050
	21st to end	Night	19% 13% 41% 26% 2	1155
February	1st to 10th	Night	20% 13% 38% 26% 2	1024
	11th to 20th	Night	20% 17% 38% 24% 1	823
	21st to end	Night	20% 14% 39% 26% 1	692
March	1st to 10th	Night	22% 13% 37% 25% 4	840
	11th to 20th	Night	22% 11% 35% 28% 4	663
	21st to end	Night	20% 13% 33% 28% 7%	693
April	1st to 10th	Night	17% 10% 40% 26% 6%	630
	11th to 20th	Night	16% 11% 34% 28% 10%	623
	21st to end	Night	21% 7% 35% 30% 8% 1	630
May	1st to 10th	Night	18% 5% 31% 35% 10% 1	630
	11th to 20th	Night	15% 6% 28% 32% 19% 1	621
	21st to end	Night	10% 4 22% 40% 20% 4	683
June	1st to 10th	Night	8% 4 20% 39% 28% 1	630
	11th to 20th	Night	6% 2 18% 48% 24% 2	615
	21st to end	Night	7% 2 19% 43% 29% 1	600
July	1st to 10th	Night	10% 2 9% 35% 39% 5%	585
	11th to 20th	Night	4 3 12% 42% 36% 4	582
	21st to end	Night	8% 1 12% 39% 36% 4	657
August	1st to 10th	Night	7% 2 10% 41% 37% 4	597
	11th to 20th	Night	7% 1 10% 42% 36% 4	594
	21st to end	Night	7% 2 9% 36% 42% 5%	660
September	1st to 10th	Night	14% 3 9% 37% 32% 5%	600
	11th to 20th	Night	9% 2 11% 38% 34% 6%	632
	21st to end	Night	11% 5% 20% 33% 26% 6%	800
October	1st to 10th	Night	8% 3 24% 37% 24% 4	800
	11th to 20th	Night	15% 7% 29% 32% 16% 1	800
	21st to end	Night	21% 11% 32% 29% 7%	880
November	1st to 10th	Night	13% 5% 39% 33% 9% 1	820
	11th to 20th	Night	16% 10% 35% 30% 9%	840
	21st to end	Night	25% 10% 33% 25% 7%	861
December	1st to 10th	Night	21% 12% 33% 29% 4 1	1050
	11th to 20th	Night	22% 10% 32% 31% 6%	1050
	21st to end	Night	24% 13% 36% 24% 3	1155

Page generated at 2026-06-13 01:31:39. Version ac07

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