Raven Run Nature Conservancy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Raven Run Nature Conservancy clear sky chart from 2005-11-06 to 2024-11-08.

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	14% 8% 3 7% 5% 4 4 4 5% 7% 38%	101265
	Night	14% 8% 3 7% 4 4 4 3 5% 7% 39%	97766
Transparency	Day	43% 7% 11% 23% 15% 2	104996
	Night	42% 7% 10% 22% 17% 3	102173
Seeing	Day	18% 9% 24% 24% 17% 9%	14925
	Night	17% 8% 24% 30% 18% 2	24776

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	17% 15% 5% 8% 5% 4 4 4 6% 6% 26%	2836
	11th to 20th	Day	17% 14% 6% 15% 5% 5% 3 3 3 4 25%	2840
	21st to end	Day	27% 14% 8% 7% 3 4 3 3 4 5% 23%	3124
February	1st to 10th	Day	19% 12% 5% 9% 5% 3 4 3 4 5% 30%	1847
	11th to 20th	Day	19% 11% 3 8% 6% 4 3 3 5% 5% 33%	1848
	21st to end	Day	21% 12% 3 7% 5% 4 3 4 5% 5% 31%	1570
March	1st to 10th	Day	25% 13% 3 7% 3 4 4 2 4 5% 31%	3169
	11th to 20th	Day	14% 7% 2 5% 4 3 4 3 5% 6% 46%	3480
	21st to end	Day	15% 9% 3 7% 4 4 4 4 6% 7% 37%	3815
April	1st to 10th	Day	14% 8% 3 6% 5% 4 3 4 6% 7% 39%	2218
	11th to 20th	Day	16% 9% 2 6% 4 4 4 4 5% 6% 41%	2285
	21st to end	Day	16% 8% 2 7% 5% 5% 5% 3 6% 7% 37%	2470
May	1st to 10th	Day	19% 9% 4 8% 5% 5% 5% 4 5% 7% 30%	4082
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 5% 6% 38%	4081
	21st to end	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 9% 37%	4476
June	1st to 10th	Day	11% 5% 2 6% 6% 6% 4 4 6% 7% 41%	2470
	11th to 20th	Day	7% 5% 2 5% 5% 6% 5% 5% 7% 9% 43%	2470
	21st to end	Day	8% 6% 2 6% 5% 5% 5% 5% 7% 10% 41%	2594
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 9% 40%	4221
	11th to 20th	Day	8% 5% 2 6% 4 5% 6% 5% 7% 10% 42%	4120
	21st to end	Day	17% 10% 4 9% 7% 6% 5% 5% 6% 8% 24%	4466
August	1st to 10th	Day	8% 4 2 5% 4 5% 5% 4 7% 10% 45%	4104
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 11% 37%	4012
	21st to end	Day	6% 4 1 4 4 5% 5% 3 6% 9% 54%	4180
September	1st to 10th	Day	14% 6% 2 5% 5% 4 5% 5% 6% 8% 41%	2147
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 6% 8% 46%	2090
	21st to end	Day	15% 6% 2 6% 4 3 4 3 5% 6% 46%	2090
October	1st to 10th	Day	10% 4 2 5% 4 4 3 3 5% 6% 54%	2090
	11th to 20th	Day	13% 6% 1 6% 4 3 4 3 4 6% 49%	1943
	21st to end	Day	18% 8% 2 5% 3 3 4 3 4 6% 44%	1985
November	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 4 6% 53%	1735
	11th to 20th	Day	16% 10% 2 6% 4 3 3 3 4 6% 43%	1710
	21st to end	Day	17% 10% 3 6% 4 3 3 3 4 6% 40%	1710
December	1st to 10th	Day	21% 14% 4 7% 4 4 4 3 4 5% 30%	1710
	11th to 20th	Day	15% 14% 4 8% 5% 5% 4 3 5% 5% 33%	2153
	21st to end	Day	19% 16% 4 9% 5% 5% 5% 4 5% 6% 22%	3124
January	1st to 10th	Night	16% 16% 5% 10% 5% 4 4 3 5% 5% 26%	4109
	11th to 20th	Night	20% 14% 5% 11% 6% 4 3 2 3 4 29%	4120
	21st to end	Night	24% 13% 4 7% 4 4 3 3 4 4 29%	4532
February	1st to 10th	Night	21% 11% 5% 9% 5% 3 4 3 5% 6% 29%	2328
	11th to 20th	Night	21% 11% 3 8% 5% 4 3 3 4 6% 33%	2218
	21st to end	Night	23% 12% 4 8% 5% 4 4 2 5% 4 29%	1884
March	1st to 10th	Night	21% 14% 3 6% 4 4 4 3 4 5% 32%	3683
	11th to 20th	Night	14% 7% 2 5% 3 3 4 3 5% 6% 49%	3480
	21st to end	Night	14% 8% 3 7% 5% 5% 4 4 6% 6% 40%	3817
April	1st to 10th	Night	11% 7% 2 6% 5% 5% 5% 4 6% 6% 43%	1976
	11th to 20th	Night	14% 8% 3 6% 5% 4 4 3 5% 6% 43%	1843
	21st to end	Night	16% 7% 2 6% 6% 5% 5% 4 5% 7% 39%	1710
May	1st to 10th	Night	19% 10% 3 8% 6% 5% 5% 5% 5% 7% 27%	2813
	11th to 20th	Night	19% 7% 2 5% 5% 3 4 4 6% 8% 38%	2812
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	3079
June	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 8% 11% 45%	1710
	11th to 20th	Night	5% 4 2 5% 4 4 5% 5% 8% 11% 48%	1710
	21st to end	Night	7% 4 2 5% 4 5% 5% 4 9% 12% 43%	1567
July	1st to 10th	Night	6% 5% 3 7% 5% 5% 4 5% 6% 10% 45%	2716
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 7% 9% 49%	2840
	21st to end	Night	15% 8% 3 8% 5% 5% 6% 5% 6% 9% 30%	3087
August	1st to 10th	Night	8% 5% 2 6% 4 4 5% 3 6% 9% 47%	2825
	11th to 20th	Night	7% 6% 2 7% 5% 6% 5% 4 7% 8% 44%	2812
	21st to end	Night	4 3 1 4 3 3 4 3 5% 9% 60%	3476
September	1st to 10th	Night	11% 5% 2 6% 4 4 3 5% 5% 7% 48%	2014
	11th to 20th	Night	11% 4 2 5% 3 3 4 4 6% 8% 50%	2090
	21st to end	Night	11% 5% 2 6% 5% 3 4 3 4 6% 50%	2090
October	1st to 10th	Night	10% 4 1 5% 3 3 4 3 4 8% 56%	2090
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 4 8% 48%	2236
	21st to end	Night	17% 8% 2 5% 4 3 4 3 4 6% 45%	2611
November	1st to 10th	Night	12% 6% 3 6% 3 3 3 3 5% 6% 51%	2504
	11th to 20th	Night	15% 8% 3 6% 3 3 4 3 4 7% 44%	2470
	21st to end	Night	17% 9% 3 6% 4 3 3 3 4 6% 40%	2470
December	1st to 10th	Night	21% 12% 3 7% 3 4 4 3 5% 6% 32%	2470
	11th to 20th	Night	18% 10% 4 8% 4 5% 3 2 4 5% 36%	3042
	21st to end	Night	18% 14% 4 10% 7% 6% 6% 4 5% 6% 21%	4532

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	56% 7% 11% 16% 9% 1	2837
	11th to 20th	Day	63% 6% 7% 17% 6% 1	2840
	21st to end	Day	64% 4 7% 20% 5% 1	3124
February	1st to 10th	Day	56% 5% 8% 19% 10% 2	1847
	11th to 20th	Day	54% 5% 8% 19% 11% 3	1858
	21st to end	Day	54% 6% 8% 19% 10% 3	1570
March	1st to 10th	Day	55% 5% 8% 17% 10% 4	3169
	11th to 20th	Day	37% 6% 13% 24% 18% 1	3480
	21st to end	Day	43% 8% 12% 26% 10% 1	3815
April	1st to 10th	Day	44% 6% 11% 23% 13% 3	2218
	11th to 20th	Day	44% 5% 9% 22% 16% 4	2285
	21st to end	Day	45% 7% 11% 23% 11% 2	2470
May	1st to 10th	Day	51% 9% 11% 20% 8% 1	4120
	11th to 20th	Day	47% 7% 11% 22% 12%	4085
	21st to end	Day	38% 10% 14% 20% 16% 2	4489
June	1st to 10th	Day	40% 9% 10% 26% 15% 1	2470
	11th to 20th	Day	34% 10% 14% 23% 17% 2	2470
	21st to end	Day	35% 10% 15% 19% 16% 4	2594
July	1st to 10th	Day	39% 8% 15% 23% 15% 1	4156
	11th to 20th	Day	33% 9% 13% 32% 12% 2	4051
	21st to end	Day	56% 7% 11% 15% 9% 1	4324
August	1st to 10th	Day	31% 9% 14% 34% 12% 1	4091
	11th to 20th	Day	38% 8% 12% 27% 13% 2	4051
	21st to end	Day	27% 8% 12% 33% 18% 3	4179
September	1st to 10th	Day	39% 8% 13% 17% 18% 5%	2147
	11th to 20th	Day	34% 7% 12% 22% 21% 3	2090
	21st to end	Day	39% 6% 8% 24% 21% 3	2090
October	1st to 10th	Day	22% 4 7% 25% 40% 3	3480
	11th to 20th	Day	25% 4 10% 27% 32% 2	3209
	21st to end	Day	30% 4 8% 29% 20% 9%	3248
November	1st to 10th	Day	34% 4 8% 26% 23% 4	1735
	11th to 20th	Day	43% 3 8% 23% 19% 4	1710
	21st to end	Day	46% 5% 9% 21% 18% 2	1710
December	1st to 10th	Day	57% 5% 9% 19% 9% 1	1710
	11th to 20th	Day	52% 6% 9% 17% 14% 1	2150
	21st to end	Day	59% 8% 10% 17% 5% 1	3124
January	1st to 10th	Night	57% 7% 9% 16% 10% 1	4109
	11th to 20th	Night	60% 5% 6% 18% 9% 2	4120
	21st to end	Night	57% 5% 8% 19% 9% 1	4532
February	1st to 10th	Night	55% 5% 10% 18% 10% 1	2328
	11th to 20th	Night	53% 5% 7% 20% 13% 2	2219
	21st to end	Night	58% 5% 9% 14% 11% 3	1884
March	1st to 10th	Night	53% 5% 8% 20% 12% 2	3683
	11th to 20th	Night	35% 7% 10% 28% 16% 4	3480
	21st to end	Night	43% 6% 12% 23% 15% 1	3817
April	1st to 10th	Night	38% 8% 12% 22% 18% 3	1976
	11th to 20th	Night	41% 6% 8% 20% 18% 7%	1843
	21st to end	Night	43% 8% 12% 22% 13% 2	1710
May	1st to 10th	Night	51% 12% 9% 19% 7% 2	2840
	11th to 20th	Night	42% 9% 13% 24% 10% 1	2813
	21st to end	Night	32% 12% 14% 23% 17% 3	3087
June	1st to 10th	Night	29% 9% 16% 26% 16% 4	1710
	11th to 20th	Night	27% 11% 17% 23% 19% 3	1710
	21st to end	Night	30% 10% 17% 22% 15% 6%	1567
July	1st to 10th	Night	33% 10% 13% 24% 17% 2	2671
	11th to 20th	Night	30% 8% 13% 31% 16% 2	2786
	21st to end	Night	48% 8% 11% 20% 12% 1	2988
August	1st to 10th	Night	31% 8% 15% 31% 14% 1	2814
	11th to 20th	Night	35% 7% 12% 29% 16% 1	2839
	21st to end	Night	21% 7% 14% 33% 21% 4	3476
September	1st to 10th	Night	33% 9% 11% 21% 19% 7%	2014
	11th to 20th	Night	30% 6% 13% 24% 24% 3	2090
	21st to end	Night	35% 7% 8% 23% 24% 4	2090
October	1st to 10th	Night	22% 4 8% 23% 40% 3	3480
	11th to 20th	Night	25% 4 7% 26% 34% 5%	3709
	21st to end	Night	30% 3 8% 22% 30% 7%	4298
November	1st to 10th	Night	35% 4 8% 25% 23% 4	2504
	11th to 20th	Night	41% 4 8% 19% 22% 6%	2470
	21st to end	Night	45% 4 8% 24% 16% 2	2470
December	1st to 10th	Night	53% 5% 10% 19% 12% 1	2470
	11th to 20th	Night	50% 5% 9% 21% 13% 2	3044
	21st to end	Night	61% 8% 10% 14% 7%	4532

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	26% 17% 34% 16% 7% 1	270
	11th to 20th	Day	29% 22% 31% 14% 4	270
	21st to end	Day	23% 22% 35% 16% 3	297
February	1st to 10th	Day	27% 17% 35% 16% 5%	270
	11th to 20th	Day	33% 18% 34% 11% 4	270
	21st to end	Day	35% 17% 34% 12% 3	225
March	1st to 10th	Day	28% 18% 37% 12% 5%	293
	11th to 20th	Day	22% 17% 36% 19% 5% 1	460
	21st to end	Day	28% 13% 30% 21% 7% 1	506
April	1st to 10th	Day	18% 18% 28% 23% 10% 2	460
	11th to 20th	Day	21% 15% 26% 23% 12% 4	452
	21st to end	Day	20% 12% 30% 24% 10% 4	460
May	1st to 10th	Day	20% 13% 28% 21% 14% 5%	463
	11th to 20th	Day	16% 9% 23% 27% 17% 8%	487
	21st to end	Day	13% 5% 21% 26% 20% 15%	529
June	1st to 10th	Day	14% 4 20% 24% 26% 12%	490
	11th to 20th	Day	9% 4 20% 28% 27% 13%	490
	21st to end	Day	8% 4 22% 32% 21% 13%	614
July	1st to 10th	Day	13% 3 16% 24% 20% 25%	547
	11th to 20th	Day	10% 2 18% 24% 28% 19%	484
	21st to end	Day	13% 3 14% 27% 27% 16%	532
August	1st to 10th	Day	13% 3 14% 25% 26% 19%	486
	11th to 20th	Day	13% 3 15% 29% 27% 13%	479
	21st to end	Day	10% 2 11% 27% 29% 21%	539
September	1st to 10th	Day	13% 3 13% 26% 26% 19%	490
	11th to 20th	Day	13% 2 10% 25% 32% 18%	490
	21st to end	Day	19% 7% 16% 24% 24% 10%	490
October	1st to 10th	Day	11% 5% 17% 31% 26% 10%	490
	11th to 20th	Day	13% 11% 26% 29% 14% 6%	490
	21st to end	Day	19% 11% 31% 25% 13% 1	434
November	1st to 10th	Day	16% 9% 30% 27% 14% 4	291
	11th to 20th	Day	24% 16% 25% 27% 7% 1	270
	21st to end	Day	24% 13% 30% 25% 7% 1	270
December	1st to 10th	Day	26% 19% 27% 23% 5% 1	270
	11th to 20th	Day	21% 14% 37% 19% 9%	270
	21st to end	Day	28% 18% 33% 17% 4	297
January	1st to 10th	Night	23% 15% 33% 23% 5%	760
	11th to 20th	Night	30% 16% 29% 22% 3	760
	21st to end	Night	24% 14% 35% 25% 2	836
February	1st to 10th	Night	27% 12% 33% 26% 2	760
	11th to 20th	Night	28% 13% 36% 21% 2	743
	21st to end	Night	27% 15% 37% 19% 2	628
March	1st to 10th	Night	21% 16% 30% 27% 6%	760
	11th to 20th	Night	23% 11% 34% 24% 8%	760
	21st to end	Night	20% 12% 31% 28% 8%	836
April	1st to 10th	Night	16% 12% 33% 32% 8%	646
	11th to 20th	Night	16% 10% 30% 30% 13% 1	563
	21st to end	Night	17% 6% 35% 31% 10% 1	570
May	1st to 10th	Night	19% 7% 29% 29% 16% 2	570
	11th to 20th	Night	16% 5% 20% 36% 20% 2	561
	21st to end	Night	9% 3 14% 37% 31% 6%	617
June	1st to 10th	Night	9% 2 17% 44% 25% 4	570
	11th to 20th	Night	7% 2 14% 40% 32% 5%	570
	21st to end	Night	7% 3 15% 39% 31% 5%	570
July	1st to 10th	Night	8% 2 12% 34% 35% 9%	555
	11th to 20th	Night	6% 2 9% 36% 42% 5%	552
	21st to end	Night	11% 3 8% 34% 38% 6%	624
August	1st to 10th	Night	9% 2 8% 32% 43% 5%	567
	11th to 20th	Night	8% 3 10% 36% 37% 6%	564
	21st to end	Night	7% 1 10% 31% 44% 8%	627
September	1st to 10th	Night	13% 1 9% 33% 37% 6%	684
	11th to 20th	Night	11% 3 12% 29% 39% 5%	760
	21st to end	Night	13% 3 18% 34% 30% 3	760
October	1st to 10th	Night	11% 4 16% 35% 30% 4	760
	11th to 20th	Night	16% 6% 25% 33% 18% 2	760
	21st to end	Night	20% 8% 26% 31% 13% 2	836
November	1st to 10th	Night	15% 7% 24% 34% 18% 2	771
	11th to 20th	Night	19% 11% 31% 30% 9% 1	760
	21st to end	Night	20% 11% 25% 32% 10% 1	760
December	1st to 10th	Night	26% 10% 29% 28% 6%	760
	11th to 20th	Night	24% 10% 32% 28% 6% 1	760
	21st to end	Night	25% 15% 28% 28% 4	836

Page generated at 2024-11-05 08:15:51. Version ac07

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