Slippery Falls Boy Scout Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Slippery Falls Boy Scout Ranch clear sky chart from 2005-11-06 to 2025-01-07.

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% 5% 2 5% 3 3 4 3 5% 6% 52%	105321
	Night	12% 5% 2 4 3 3 3 3 4 6% 56%	103841
Transparency	Day	32% 5% 10% 25% 22% 6%	109051
	Night	29% 4 9% 25% 25% 9%	108238
Seeing	Day	13% 9% 24% 28% 20% 6%	15477
	Night	12% 9% 29% 33% 15% 1	25432

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% 9% 2 5% 3 3 3 3 5% 5% 51%	2901
	11th to 20th	Day	9% 6% 1 4 2 2 2 2 3 5% 64%	2850
	21st to end	Day	19% 10% 2 5% 3 3 2 2 3 4 47%	3135
February	1st to 10th	Day	16% 8% 2 5% 4 3 3 4 3 5% 47%	1767
	11th to 20th	Day	15% 6% 3 6% 3 4 3 3 4 5% 49%	1849
	21st to end	Day	20% 7% 2 5% 3 3 2 3 3 4 49%	1585
March	1st to 10th	Day	15% 6% 3 5% 3 3 3 2 4 5% 51%	3436
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 4 5% 47%	3480
	21st to end	Day	17% 9% 2 6% 5% 4 4 3 4 6% 40%	3814
April	1st to 10th	Day	14% 5% 2 5% 3 3 3 3 5% 6% 50%	2090
	11th to 20th	Day	15% 5% 2 5% 4 3 5% 3 5% 6% 47%	2192
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 6% 45%	2447
May	1st to 10th	Day	20% 7% 2 6% 4 4 3 3 4 5% 42%	4082
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 5% 5% 47%	4082
	21st to end	Day	18% 7% 2 6% 5% 5% 4 4 5% 7% 38%	4477
June	1st to 10th	Day	8% 6% 1 6% 4 4 4 4 6% 9% 47%	2470
	11th to 20th	Day	7% 4 2 5% 5% 4 5% 5% 6% 8% 51%	2470
	21st to end	Day	5% 3 1 4 4 4 4 3 6% 8% 57%	2470
July	1st to 10th	Day	7% 4 2 4 4 4 4 4 6% 9% 52%	4120
	11th to 20th	Day	3 2 2 4 3 4 4 4 6% 9% 60%	4120
	21st to end	Day	5% 4 2 5% 4 4 5% 4 7% 11% 49%	4465
August	1st to 10th	Day	2 2 1 4 3 4 4 3 5% 8% 63%	4104
	11th to 20th	Day	6% 3 1 4 2 4 4 3 6% 9% 58%	4041
	21st to end	Day	2 2 1 4 3 4 5% 4 7% 9% 60%	4193
September	1st to 10th	Day	10% 4 2 5% 3 4 3 3 5% 6% 56%	2090
	11th to 20th	Day	11% 4 2 6% 4 4 5% 4 5% 7% 49%	2090
	21st to end	Day	9% 3 1 4 3 4 3 3 5% 6% 58%	2090
October	1st to 10th	Day	9% 3 1 5% 3 3 4 3 5% 5% 59%	2019
	11th to 20th	Day	10% 5% 2 3 3 2 2 2 3 4 64%	1900
	21st to end	Day	16% 5% 2 4 2 2 3 2 3 4 57%	2090
November	1st to 10th	Day	12% 6% 2 4 3 3 3 2 4 6% 55%	1958
	11th to 20th	Day	8% 4 2 4 3 2 2 2 4 4 64%	1825
	21st to end	Day	16% 5% 1 3 3 2 2 2 4 6% 57%	1800
December	1st to 10th	Day	15% 8% 2 4 3 2 2 2 3 6% 53%	2940
	11th to 20th	Day	19% 7% 2 4 3 3 3 3 4 4 50%	3391
	21st to end	Day	23% 8% 2 5% 3 3 3 2 3 4 45%	4488
January	1st to 10th	Night	14% 7% 2 4 3 3 3 3 4 5% 52%	4187
	11th to 20th	Night	8% 5% 2 3 2 2 2 2 4 5% 64%	4120
	21st to end	Night	20% 7% 2 5% 2 2 3 2 3 4 50%	4532
February	1st to 10th	Night	14% 8% 2 5% 3 3 3 3 4 4 50%	2428
	11th to 20th	Night	15% 6% 2 5% 4 3 2 3 4 6% 50%	2218
	21st to end	Night	15% 6% 2 5% 3 3 3 2 4 5% 51%	1867
March	1st to 10th	Night	15% 7% 2 6% 3 3 3 3 5% 5% 47%	3419
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 4 5% 56%	3480
	21st to end	Night	15% 5% 2 6% 3 4 3 3 5% 7% 47%	3817
April	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 5% 7% 51%	2090
	11th to 20th	Night	13% 5% 2 4 4 3 3 3 5% 6% 52%	1934
	21st to end	Night	14% 5% 2 5% 3 3 3 3 4 7% 51%	1728
May	1st to 10th	Night	24% 6% 1 5% 3 3 3 3 6% 6% 41%	2823
	11th to 20th	Night	16% 5% 1 5% 3 3 3 3 5% 7% 49%	2823
	21st to end	Night	13% 5% 2 5% 3 4 5% 3 5% 8% 46%	3090
June	1st to 10th	Night	5% 3 1 2 3 3 4 4 6% 10% 58%	1710
	11th to 20th	Night	6% 3 1 3 3 2 4 3 6% 11% 59%	1710
	21st to end	Night	3 2 1 3 3 3 3 4 4 8% 65%	1710
July	1st to 10th	Night	5% 4 2 5% 3 3 4 4 6% 9% 56%	2850
	11th to 20th	Night	2 1 1 3 2 3 3 3 5% 8% 69%	2850
	21st to end	Night	4 3 1 4 3 2 4 3 6% 10% 59%	3098
August	1st to 10th	Night	2 2 1 2 2 2 3 4 6% 8% 68%	2836
	11th to 20th	Night	3 2 1 2 2 2 2 3 6% 9% 68%	2798
	21st to end	Night	2 2 1 3 3 3 3 3 5% 9% 65%	3459
September	1st to 10th	Night	7% 4 2 4 3 3 3 3 4 6% 61%	2090
	11th to 20th	Night	9% 5% 2 6% 3 4 4 4 6% 6% 52%	2090
	21st to end	Night	6% 4 1 3 2 2 3 3 5% 6% 64%	2090
October	1st to 10th	Night	9% 4 2 3 2 3 3 3 4 6% 62%	2140
	11th to 20th	Night	11% 3 1 4 3 2 2 3 3 4 64%	2280
	21st to end	Night	16% 3 2 3 2 2 2 2 3 4 60%	2508
November	1st to 10th	Night	12% 3 1 4 2 3 3 2 4 5% 60%	2340
	11th to 20th	Night	8% 5% 1 3 3 3 3 3 4 6% 61%	2570
	21st to end	Night	15% 5% 1 4 3 3 2 2 4 5% 55%	2600
December	1st to 10th	Night	10% 6% 2 3 3 3 2 2 4 5% 59%	4250
	11th to 20th	Night	18% 5% 2 5% 3 3 3 2 3 4 54%	4816
	21st to end	Night	20% 6% 2 4 3 2 2 2 3 4 51%	6490

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	35% 3 7% 25% 25% 4	2902
	11th to 20th	Day	26% 2 11% 23% 33% 4	2850
	21st to end	Day	44% 2 4 20% 23% 6%	3135
February	1st to 10th	Day	41% 4 8% 19% 22% 6%	1767
	11th to 20th	Day	39% 4 6% 24% 20% 7%	1859
	21st to end	Day	41% 2 4 16% 26% 10%	1585
March	1st to 10th	Day	36% 4 7% 16% 25% 12%	3436
	11th to 20th	Day	40% 4 10% 23% 18% 5%	3480
	21st to end	Day	46% 4 8% 22% 17% 3	3814
April	1st to 10th	Day	35% 5% 10% 23% 18% 9%	2090
	11th to 20th	Day	37% 6% 10% 21% 19% 7%	2192
	21st to end	Day	40% 5% 8% 24% 19% 4	2447
May	1st to 10th	Day	43% 5% 8% 21% 16% 6%	4120
	11th to 20th	Day	38% 5% 11% 26% 19% 1	4086
	21st to end	Day	45% 6% 12% 18% 13% 5%	4489
June	1st to 10th	Day	33% 7% 15% 27% 15% 2	2470
	11th to 20th	Day	29% 7% 13% 26% 22% 2	2470
	21st to end	Day	23% 6% 14% 29% 25% 4	2470
July	1st to 10th	Day	26% 7% 14% 36% 15% 1	4056
	11th to 20th	Day	20% 5% 11% 37% 25% 3	4051
	21st to end	Day	26% 8% 15% 32% 18% 1	4325
August	1st to 10th	Day	19% 4 12% 27% 30% 8%	4090
	11th to 20th	Day	22% 5% 15% 37% 19% 2	4080
	21st to end	Day	20% 6% 17% 39% 15% 3	4192
September	1st to 10th	Day	29% 5% 10% 25% 21% 11%	2090
	11th to 20th	Day	34% 7% 10% 21% 21% 8%	2090
	21st to end	Day	25% 5% 8% 23% 28% 11%	2090
October	1st to 10th	Day	17% 3 7% 13% 37% 23%	3357
	11th to 20th	Day	18% 3 5% 19% 35% 20%	3140
	21st to end	Day	27% 3 6% 28% 27% 8%	3428
November	1st to 10th	Day	31% 4 8% 22% 26% 9%	1958
	11th to 20th	Day	25% 4 7% 25% 29% 12%	1825
	21st to end	Day	32% 3 7% 20% 29% 9%	1800
December	1st to 10th	Day	35% 3 7% 31% 21% 3	2940
	11th to 20th	Day	39% 3 4 19% 28% 8%	3389
	21st to end	Day	44% 3 4 23% 21% 5%	4488
January	1st to 10th	Night	35% 4 5% 21% 29% 6%	4187
	11th to 20th	Night	24% 3 13% 24% 29% 7%	4120
	21st to end	Night	41% 2 6% 18% 25% 8%	4532
February	1st to 10th	Night	38% 3 8% 21% 22% 7%	2428
	11th to 20th	Night	37% 4 6% 22% 24% 8%	2218
	21st to end	Night	37% 3 7% 16% 23% 14%	1867
March	1st to 10th	Night	39% 5% 5% 17% 20% 14%	3419
	11th to 20th	Night	31% 5% 8% 29% 18% 8%	3480
	21st to end	Night	36% 5% 9% 21% 24% 3	3817
April	1st to 10th	Night	33% 4 10% 19% 20% 13%	2090
	11th to 20th	Night	34% 5% 8% 21% 20% 12%	1934
	21st to end	Night	34% 5% 8% 25% 23% 4	1728
May	1st to 10th	Night	43% 6% 9% 17% 17% 8%	2850
	11th to 20th	Night	35% 4 14% 26% 18% 2	2824
	21st to end	Night	34% 8% 13% 24% 15% 7%	3099
June	1st to 10th	Night	21% 6% 15% 33% 21% 4	1710
	11th to 20th	Night	20% 6% 14% 30% 25% 5%	1710
	21st to end	Night	18% 6% 13% 29% 28% 7%	1710
July	1st to 10th	Night	25% 7% 15% 35% 15% 4	2805
	11th to 20th	Night	12% 4 10% 42% 27% 4	2796
	21st to end	Night	20% 5% 15% 36% 23% 2	2999
August	1st to 10th	Night	13% 5% 9% 29% 36% 8%	2826
	11th to 20th	Night	14% 4 14% 39% 23% 6%	2825
	21st to end	Night	16% 6% 15% 40% 19% 3	3459
September	1st to 10th	Night	26% 5% 9% 23% 26% 11%	2090
	11th to 20th	Night	31% 5% 9% 21% 23% 10%	2090
	21st to end	Night	21% 4 7% 25% 31% 13%	2090
October	1st to 10th	Night	15% 3 6% 13% 36% 28%	3569
	11th to 20th	Night	17% 3 4 16% 37% 23%	3779
	21st to end	Night	24% 4 6% 29% 25% 12%	4120
November	1st to 10th	Night	28% 3 7% 23% 27% 12%	2340
	11th to 20th	Night	25% 4 7% 23% 27% 14%	2570
	21st to end	Night	33% 3 6% 20% 29% 9%	2600
December	1st to 10th	Night	29% 3 7% 28% 28% 6%	4250
	11th to 20th	Night	36% 3 5% 16% 27% 13%	4817
	21st to end	Night	38% 3 6% 23% 23% 7%	6490

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% 16% 37% 22% 5% 1	288
	11th to 20th	Day	22% 19% 36% 17% 5% 1	270
	21st to end	Day	17% 20% 34% 20% 8% 1	297
February	1st to 10th	Day	24% 19% 33% 17% 6%	270
	11th to 20th	Day	24% 19% 41% 14% 2	270
	21st to end	Day	29% 19% 38% 12% 2	225
March	1st to 10th	Day	20% 21% 37% 16% 6%	270
	11th to 20th	Day	23% 24% 34% 12% 5% 1	270
	21st to end	Day	22% 18% 43% 14% 3	297
April	1st to 10th	Day	21% 22% 29% 23% 4 1	270
	11th to 20th	Day	19% 19% 38% 17% 6%	390
	21st to end	Day	17% 16% 37% 21% 7% 1	627
May	1st to 10th	Day	14% 13% 34% 32% 6% 1	653
	11th to 20th	Day	16% 8% 33% 28% 13% 3	675
	21st to end	Day	14% 8% 31% 28% 15% 4	734
June	1st to 10th	Day	7% 4 19% 37% 26% 7%	680
	11th to 20th	Day	7% 3 20% 40% 26% 4	680
	21st to end	Day	4 2 17% 42% 26% 10%	680
July	1st to 10th	Day	6% 1 11% 34% 34% 14%	671
	11th to 20th	Day	3 1 9% 32% 42% 12%	668
	21st to end	Day	5% 1 5% 33% 41% 15%	739
August	1st to 10th	Day	3 1 10% 36% 41% 9%	676
	11th to 20th	Day	8% 2 10% 35% 38% 7%	665
	21st to end	Day	4 1 6% 32% 42% 16%	552
September	1st to 10th	Day	7% 11% 27% 36% 19%	300
	11th to 20th	Day	4 2 10% 35% 34% 14%	300
	21st to end	Day	14% 4 13% 33% 27% 9%	300
October	1st to 10th	Day	5% 4 24% 37% 23% 7%	300
	11th to 20th	Day	14% 8% 30% 33% 14% 2	300
	21st to end	Day	25% 10% 28% 23% 13% 1	330
November	1st to 10th	Day	14% 11% 38% 24% 10% 3	300
	11th to 20th	Day	16% 13% 34% 23% 12% 2	300
	21st to end	Day	21% 15% 36% 21% 7% 1	300
December	1st to 10th	Day	14% 17% 35% 25% 8% 1	300
	11th to 20th	Day	23% 14% 36% 21% 5%	300
	21st to end	Day	24% 18% 37% 18% 3	330
January	1st to 10th	Night	15% 12% 35% 30% 7%	981
	11th to 20th	Night	15% 17% 34% 28% 6%	950
	21st to end	Night	14% 12% 35% 33% 6%	1045
February	1st to 10th	Night	19% 15% 36% 27% 4	908
	11th to 20th	Night	18% 15% 40% 24% 3	744
	21st to end	Night	20% 17% 38% 22% 3	611
March	1st to 10th	Night	17% 14% 38% 25% 5%	570
	11th to 20th	Night	18% 14% 38% 27% 4	570
	21st to end	Night	15% 14% 41% 26% 5%	627
April	1st to 10th	Night	13% 15% 42% 26% 4	570
	11th to 20th	Night	14% 15% 39% 26% 6%	563
	21st to end	Night	15% 11% 42% 23% 8% 1	570
May	1st to 10th	Night	12% 11% 37% 32% 7% 1	570
	11th to 20th	Night	12% 7% 34% 31% 15% 1	561
	21st to end	Night	8% 4 31% 37% 17% 1	617
June	1st to 10th	Night	5% 3 23% 40% 26% 3	570
	11th to 20th	Night	6% 2 23% 50% 19%	570
	21st to end	Night	2 1 18% 48% 26% 5%	570
July	1st to 10th	Night	3 1 11% 43% 38% 4	555
	11th to 20th	Night	2 1 10% 44% 39% 3	552
	21st to end	Night	3 1 8% 44% 40% 3	624
August	1st to 10th	Night	2 1 9% 48% 38% 2	567
	11th to 20th	Night	5% 9% 44% 37% 4	564
	21st to end	Night	3 1 7% 44% 41% 5%	627
September	1st to 10th	Night	8% 2 9% 44% 35% 3	570
	11th to 20th	Night	9% 1 15% 39% 33% 3	570
	21st to end	Night	7% 2 19% 39% 28% 4	570
October	1st to 10th	Night	9% 3 25% 36% 25% 3	620
	11th to 20th	Night	11% 6% 31% 37% 14% 1	760
	21st to end	Night	17% 10% 29% 31% 13% 1	836
November	1st to 10th	Night	13% 6% 35% 33% 12% 1	780
	11th to 20th	Night	10% 12% 33% 33% 11%	970
	21st to end	Night	18% 10% 36% 27% 9% 1	1000
December	1st to 10th	Night	14% 12% 36% 32% 7%	1000
	11th to 20th	Night	21% 10% 35% 28% 6%	1000
	21st to end	Night	19% 13% 36% 26% 6%	1100

Page generated at 2025-01-04 02:24:02. Version ac07

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