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 2025-02-21.

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 6% 4 4 4 4 5% 8% 43%	108588
	Night	14% 7% 3 6% 4 4 4 3 5% 6% 43%	110159
Transparency	Day	38% 6% 12% 25% 17% 3	112207
	Night	39% 5% 11% 24% 18% 3	114682
Seeing	Day	14% 9% 24% 26% 19% 7%	15936
	Night	16% 8% 28% 31% 15% 2	25910

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% 10% 5% 12% 6% 4 4 4 5% 6% 31%	3617
	11th to 20th	Day	11% 7% 3 8% 6% 7% 3 3 5% 6% 39%	3832
	21st to end	Day	18% 14% 4 7% 4 3 3 3 4 5% 34%	4488
February	1st to 10th	Day	16% 11% 5% 7% 4 4 3 4 4 6% 36%	1823
	11th to 20th	Day	16% 9% 4 8% 6% 3 4 3 5% 6% 37%	1948
	21st to end	Day	14% 9% 3 7% 4 4 4 4 5% 6% 39%	1570
March	1st to 10th	Day	20% 11% 3 6% 4 4 3 3 4 5% 39%	3120
	11th to 20th	Day	13% 8% 2 5% 3 3 4 3 4 7% 49%	3466
	21st to end	Day	15% 7% 3 7% 5% 4 5% 3 6% 8% 37%	4063
April	1st to 10th	Day	12% 6% 2 6% 5% 5% 4 4 6% 6% 43%	2280
	11th to 20th	Day	16% 7% 3 6% 5% 4 4 3 4 6% 42%	2254
	21st to end	Day	16% 8% 2 7% 5% 4 4 4 5% 6% 39%	2280
May	1st to 10th	Day	14% 6% 3 7% 6% 4 5% 5% 8% 10% 32%	3915
	11th to 20th	Day	17% 7% 2 6% 4 4 5% 3 5% 8% 38%	4265
	21st to end	Day	9% 6% 2 6% 5% 4 4 5% 5% 8% 45%	4824
June	1st to 10th	Day	9% 4 2 6% 4 4 5% 4 6% 9% 47%	2660
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 6% 9% 51%	2660
	21st to end	Day	5% 4 1 6% 5% 5% 5% 5% 7% 10% 47%	2660
July	1st to 10th	Day	13% 4 2 5% 5% 4 5% 4 7% 10% 42%	4440
	11th to 20th	Day	4 4 2 5% 4 5% 6% 5% 7% 12% 47%	4440
	21st to end	Day	6% 5% 3 7% 6% 6% 6% 5% 7% 10% 39%	4640
August	1st to 10th	Day	4 4 2 5% 4 4 4 4 7% 10% 52%	4018
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 7% 10% 43%	3729
	21st to end	Day	6% 5% 2 5% 4 4 4 3 5% 9% 52%	4180
September	1st to 10th	Day	13% 4 2 5% 4 4 3 4 5% 7% 49%	2280
	11th to 20th	Day	8% 6% 2 6% 4 4 4 4 6% 7% 49%	2229
	21st to end	Day	9% 4 2 5% 3 5% 4 4 5% 8% 51%	2090
October	1st to 10th	Day	10% 4 1 5% 3 4 3 3 4 5% 57%	1941
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 4 7% 51%	1900
	21st to end	Day	17% 6% 2 6% 3 3 3 2 5% 4 48%	2039
November	1st to 10th	Day	10% 5% 2 4 4 4 3 3 4 6% 55%	1762
	11th to 20th	Day	15% 7% 2 6% 4 3 3 3 5% 7% 46%	1800
	21st to end	Day	15% 10% 3 7% 4 4 3 3 4 6% 41%	1775
December	1st to 10th	Day	9% 10% 3 5% 3 3 3 3 5% 6% 50%	2610
	11th to 20th	Day	14% 8% 4 8% 5% 4 4 4 5% 6% 38%	3008
	21st to end	Day	25% 16% 5% 9% 4 4 4 3 4 4 24%	3982
January	1st to 10th	Night	16% 10% 5% 11% 5% 4 4 3 5% 5% 33%	6348
	11th to 20th	Night	12% 10% 4 9% 5% 6% 5% 3 4 5% 37%	6133
	21st to end	Night	19% 11% 4 8% 5% 4 3 3 4 5% 35%	6490
February	1st to 10th	Night	17% 10% 4 9% 5% 4 4 4 4 5% 35%	2575
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 2 4 6% 40%	2338
	21st to end	Night	17% 8% 3 7% 5% 4 3 3 6% 5% 39%	1885
March	1st to 10th	Night	21% 10% 2 5% 4 3 3 3 4 4 41%	3733
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 51%	3523
	21st to end	Night	17% 9% 3 7% 5% 4 5% 4 6% 6% 36%	3567
April	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 48%	1900
	11th to 20th	Night	14% 6% 2 4 4 4 4 4 6% 6% 45%	1875
	21st to end	Night	19% 8% 2 7% 4 3 3 3 5% 5% 41%	1900
May	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 6% 8% 38%	2976
	11th to 20th	Night	15% 7% 2 6% 3 4 4 3 5% 7% 45%	2632
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 4 7% 8% 42%	2743
June	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 6% 8% 49%	1520
	11th to 20th	Night	5% 3 2 4 3 5% 4 3 6% 8% 56%	1520
	21st to end	Night	5% 4 1 4 4 4 5% 4 7% 9% 53%	1520
July	1st to 10th	Night	12% 4 2 5% 3 4 3 4 6% 9% 48%	2530
	11th to 20th	Night	5% 4 2 5% 4 3 4 3 5% 9% 56%	2530
	21st to end	Night	8% 6% 3 7% 5% 5% 6% 4 8% 10% 39%	2906
August	1st to 10th	Night	5% 3 2 5% 3 3 4 4 5% 8% 58%	2917
	11th to 20th	Night	10% 5% 2 6% 4 5% 4 4 6% 7% 48%	3100
	21st to end	Night	6% 3 1 4 3 4 4 4 5% 9% 59%	3476
September	1st to 10th	Night	12% 4 2 5% 3 3 4 3 4 6% 54%	1900
	11th to 20th	Night	8% 4 2 6% 4 4 4 4 6% 8% 51%	1930
	21st to end	Night	10% 4 1 4 4 4 4 4 5% 7% 52%	2090
October	1st to 10th	Night	8% 4 2 5% 3 3 3 2 4 6% 60%	2235
	11th to 20th	Night	13% 5% 2 5% 2 2 3 2 4 6% 56%	2280
	21st to end	Night	17% 6% 2 6% 3 3 3 3 3 5% 48%	2556
November	1st to 10th	Night	11% 5% 2 5% 3 3 3 2 4 5% 56%	2536
	11th to 20th	Night	14% 4 2 5% 4 3 4 3 5% 7% 49%	2600
	21st to end	Night	18% 9% 3 5% 3 3 3 3 4 6% 44%	2620
December	1st to 10th	Night	14% 8% 3 5% 4 3 4 3 5% 6% 46%	4580
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 5% 7% 43%	5199
	21st to end	Night	25% 14% 5% 8% 4 4 4 3 4 5% 23%	6996

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	53% 6% 11% 20% 9% 1	3618
	11th to 20th	Day	44% 5% 11% 24% 14% 3	3832
	21st to end	Day	53% 3 8% 17% 15% 5%	4488
February	1st to 10th	Day	49% 4 13% 23% 10% 1	1823
	11th to 20th	Day	49% 5% 9% 20% 13% 3	1958
	21st to end	Day	46% 6% 10% 21% 15% 4	1570
March	1st to 10th	Day	49% 4 8% 21% 15% 4	3120
	11th to 20th	Day	36% 5% 11% 26% 17% 5%	3466
	21st to end	Day	43% 8% 17% 22% 9% 1	4063
April	1st to 10th	Day	39% 5% 13% 26% 16% 1	2280
	11th to 20th	Day	44% 4 10% 24% 14% 3	2254
	21st to end	Day	45% 7% 12% 23% 12% 1	2280
May	1st to 10th	Day	42% 11% 15% 23% 8% 1	3950
	11th to 20th	Day	44% 8% 11% 25% 11% 1	4269
	21st to end	Day	36% 8% 11% 23% 21% 1	4837
June	1st to 10th	Day	32% 9% 13% 27% 17% 3	2660
	11th to 20th	Day	28% 7% 13% 25% 24% 3	2660
	21st to end	Day	29% 8% 17% 24% 16% 5%	2660
July	1st to 10th	Day	37% 8% 11% 30% 13% 3	4371
	11th to 20th	Day	27% 8% 14% 31% 18% 2	4365
	21st to end	Day	36% 9% 16% 26% 12% 1	4494
August	1st to 10th	Day	25% 7% 14% 38% 16%	4004
	11th to 20th	Day	36% 6% 14% 26% 18% 1	3765
	21st to end	Day	29% 6% 13% 34% 15% 3	4179
September	1st to 10th	Day	34% 5% 11% 26% 19% 5%	2280
	11th to 20th	Day	33% 7% 8% 25% 24% 3	2229
	21st to end	Day	30% 6% 9% 27% 24% 3	2090
October	1st to 10th	Day	18% 3 5% 21% 43% 9%	3227
	11th to 20th	Day	23% 3 8% 21% 37% 8%	3140
	21st to end	Day	31% 3 7% 27% 28% 4	3341
November	1st to 10th	Day	31% 4 12% 28% 20% 6%	1762
	11th to 20th	Day	38% 5% 10% 23% 19% 6%	1800
	21st to end	Day	45% 5% 9% 25% 15% 1	1775
December	1st to 10th	Day	35% 4 14% 30% 16%	2610
	11th to 20th	Day	46% 5% 11% 22% 14% 2	3005
	21st to end	Day	65% 4 12% 12% 6% 1	3982
January	1st to 10th	Night	53% 4 11% 23% 8% 1	6348
	11th to 20th	Night	49% 4 8% 21% 14% 3	6133
	21st to end	Night	52% 3 9% 18% 17% 1	6490
February	1st to 10th	Night	52% 5% 10% 21% 12% 1	2575
	11th to 20th	Night	46% 4 10% 20% 17% 2	2339
	21st to end	Night	46% 4 11% 21% 13% 4	1885
March	1st to 10th	Night	46% 5% 8% 23% 15% 2	3733
	11th to 20th	Night	34% 5% 12% 23% 22% 4	3523
	21st to end	Night	47% 8% 11% 25% 8% 1	3567
April	1st to 10th	Night	36% 5% 11% 27% 17% 3	1900
	11th to 20th	Night	38% 6% 10% 23% 19% 4	1875
	21st to end	Night	46% 5% 8% 23% 16% 3	1900
May	1st to 10th	Night	41% 8% 17% 20% 12% 2	3006
	11th to 20th	Night	38% 8% 13% 25% 14% 1	2633
	21st to end	Night	36% 10% 12% 24% 16% 2	2751
June	1st to 10th	Night	31% 7% 14% 25% 19% 4	1520
	11th to 20th	Night	24% 7% 13% 27% 25% 5%	1520
	21st to end	Night	25% 7% 17% 27% 18% 7%	1520
July	1st to 10th	Night	33% 7% 12% 28% 17% 4	2490
	11th to 20th	Night	25% 5% 12% 36% 19% 3	2482
	21st to end	Night	37% 9% 16% 24% 13% 2	2814
August	1st to 10th	Night	23% 7% 16% 35% 19% 1	2907
	11th to 20th	Night	34% 6% 13% 22% 22% 2	3130
	21st to end	Night	23% 6% 14% 35% 19% 3	3476
September	1st to 10th	Night	31% 5% 9% 27% 21% 7%	1900
	11th to 20th	Night	31% 6% 8% 27% 23% 5%	1930
	21st to end	Night	30% 6% 8% 23% 27% 5%	2090
October	1st to 10th	Night	16% 3 6% 18% 47% 9%	3729
	11th to 20th	Night	22% 3 7% 22% 41% 7%	3779
	21st to end	Night	31% 3 9% 24% 26% 6%	4204
November	1st to 10th	Night	31% 5% 11% 25% 23% 6%	2536
	11th to 20th	Night	36% 4 10% 23% 23% 4	2600
	21st to end	Night	43% 4 10% 23% 19% 2	2620
December	1st to 10th	Night	39% 4 10% 30% 15% 1	4580
	11th to 20th	Night	42% 4 13% 22% 18%	5201
	21st to end	Night	63% 5% 12% 13% 6% 1	6996

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	21% 19% 32% 21% 7%	300
	11th to 20th	Day	25% 18% 37% 18% 3	300
	21st to end	Day	18% 17% 42% 18% 5%	330
February	1st to 10th	Day	26% 13% 41% 17% 4	300
	11th to 20th	Day	27% 19% 32% 17% 5% 1	300
	21st to end	Day	23% 20% 34% 20% 3	225
March	1st to 10th	Day	16% 17% 46% 17% 4	270
	11th to 20th	Day	25% 16% 36% 15% 7% 1	270
	21st to end	Day	27% 15% 32% 20% 6% 1	443
April	1st to 10th	Day	15% 15% 36% 25% 9% 1	460
	11th to 20th	Day	20% 15% 30% 22% 12% 1	452
	21st to end	Day	20% 14% 33% 19% 12% 1	460
May	1st to 10th	Day	16% 13% 30% 28% 11% 2	463
	11th to 20th	Day	17% 8% 23% 29% 18% 5%	593
	21st to end	Day	11% 4 27% 31% 19% 8%	734
June	1st to 10th	Day	10% 5% 19% 28% 28% 11%	680
	11th to 20th	Day	7% 3 18% 36% 27% 10%	680
	21st to end	Day	5% 4 26% 34% 23% 8%	680
July	1st to 10th	Day	11% 3 12% 27% 27% 20%	671
	11th to 20th	Day	5% 3 11% 36% 32% 13%	668
	21st to end	Day	9% 3 12% 32% 32% 12%	739
August	1st to 10th	Day	7% 2 12% 33% 32% 14%	629
	11th to 20th	Day	11% 2 14% 28% 32% 13%	479
	21st to end	Day	11% 1 10% 24% 39% 16%	539
September	1st to 10th	Day	13% 2 14% 26% 31% 14%	490
	11th to 20th	Day	8% 2 11% 28% 35% 16%	490
	21st to end	Day	10% 7% 21% 26% 26% 10%	490
October	1st to 10th	Day	12% 4 22% 35% 19% 8%	341
	11th to 20th	Day	15% 12% 33% 26% 11% 3	300
	21st to end	Day	25% 18% 25% 23% 9%	330
November	1st to 10th	Day	12% 10% 33% 26% 13% 5%	300
	11th to 20th	Day	18% 17% 32% 21% 9% 3	300
	21st to end	Day	22% 15% 30% 22% 9% 2	300
December	1st to 10th	Day	12% 19% 38% 19% 7% 5%	300
	11th to 20th	Day	21% 16% 32% 26% 4 1	300
	21st to end	Day	27% 16% 38% 15% 4	330
January	1st to 10th	Night	18% 15% 38% 26% 4	1000
	11th to 20th	Night	21% 15% 37% 22% 5%	1000
	21st to end	Night	19% 12% 40% 27% 2	1100
February	1st to 10th	Night	21% 13% 37% 25% 2	975
	11th to 20th	Night	19% 17% 38% 24% 1	783
	21st to end	Night	21% 13% 39% 25% 1	629
March	1st to 10th	Night	21% 12% 38% 25% 4	760
	11th to 20th	Night	22% 10% 35% 29% 5%	600
	21st to end	Night	21% 11% 32% 28% 7%	627
April	1st to 10th	Night	16% 11% 40% 27% 7%	570
	11th to 20th	Night	16% 10% 32% 29% 12% 1	563
	21st to end	Night	22% 6% 34% 29% 8% 1	570
May	1st to 10th	Night	18% 4 31% 35% 11% 1	570
	11th to 20th	Night	15% 5% 27% 33% 19% 1	561
	21st to end	Night	9% 4 22% 41% 21% 4	617
June	1st to 10th	Night	8% 4 18% 39% 30% 1	570
	11th to 20th	Night	5% 2 17% 49% 25% 2	570
	21st to end	Night	7% 2 19% 42% 29% 1	570
July	1st to 10th	Night	10% 2 9% 35% 38% 6%	555
	11th to 20th	Night	4 3 11% 42% 36% 4	552
	21st to end	Night	8% 1 12% 40% 35% 4	624
August	1st to 10th	Night	7% 2 10% 40% 38% 4	567
	11th to 20th	Night	7% 1 11% 42% 34% 4	564
	21st to end	Night	7% 2 9% 34% 43% 5%	627
September	1st to 10th	Night	14% 2 9% 37% 32% 5%	570
	11th to 20th	Night	9% 2 12% 38% 34% 6%	600
	21st to end	Night	11% 5% 21% 33% 26% 5%	760
October	1st to 10th	Night	8% 3 24% 36% 24% 4	760
	11th to 20th	Night	15% 7% 29% 31% 16% 1	760
	21st to end	Night	21% 10% 33% 30% 7%	836
November	1st to 10th	Night	14% 5% 38% 34% 9% 1	780
	11th to 20th	Night	17% 9% 35% 29% 9% 1	800
	21st to end	Night	24% 9% 33% 26% 7%	820
December	1st to 10th	Night	21% 12% 33% 29% 5% 1	1000
	11th to 20th	Night	22% 9% 31% 32% 6%	1000
	21st to end	Night	25% 13% 36% 24% 3	1100

Page generated at 2025-02-18 02:26:25. Version ac07

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