Cherry Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cherry Mountain Observatory clear sky chart from 2005-11-06 to 2024-08-30.

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	9% 6% 2 6% 4 4 4 4 6% 7% 49%	95581
	Night	9% 6% 2 5% 4 3 3 3 5% 7% 53%	93541
Transparency	Day	34% 5% 9% 21% 20% 10%	95357
	Night	32% 4 10% 21% 20% 13%	93371
Seeing	Day	13% 7% 25% 32% 19% 5%	14650
	Night	13% 8% 31% 35% 13% 1	24543

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	9% 8% 3 5% 2 2 3 2 4 5% 56%	2847
	11th to 20th	Day	11% 7% 2 4 3 2 2 3 4 5% 57%	2850
	21st to end	Day	12% 7% 3 5% 3 3 3 3 4 7% 50%	3455
February	1st to 10th	Day	14% 5% 2 7% 3 3 3 2 5% 6% 50%	1900
	11th to 20th	Day	13% 6% 2 5% 3 4 4 4 5% 6% 48%	1849
	21st to end	Day	14% 6% 2 5% 3 3 3 3 5% 5% 53%	1570
March	1st to 10th	Day	13% 8% 2 6% 5% 3 3 3 5% 6% 47%	3306
	11th to 20th	Day	15% 8% 4 8% 5% 5% 5% 4 5% 6% 36%	3480
	21st to end	Day	9% 6% 2 7% 4 4 4 3 5% 7% 49%	3814
April	1st to 10th	Day	11% 6% 2 6% 5% 4 4 4 5% 7% 47%	2090
	11th to 20th	Day	15% 8% 2 5% 4 3 4 3 4 6% 46%	2165
	21st to end	Day	10% 7% 2 6% 6% 4 4 3 4 6% 49%	2370
May	1st to 10th	Day	14% 8% 3 8% 4 4 5% 4 6% 7% 37%	4082
	11th to 20th	Day	12% 8% 3 6% 5% 3 4 4 5% 6% 45%	4082
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 8% 40%	4477
June	1st to 10th	Day	4 4 2 5% 4 4 5% 4 7% 10% 51%	2470
	11th to 20th	Day	4 4 2 5% 4 4 4 4 7% 10% 51%	2470
	21st to end	Day	5% 5% 2 5% 5% 5% 6% 5% 7% 9% 45%	2470
July	1st to 10th	Day	5% 4 1 5% 5% 5% 6% 4 7% 9% 47%	4120
	11th to 20th	Day	3 3 1 4 4 4 4 4 6% 10% 56%	4120
	21st to end	Day	8% 5% 2 5% 5% 5% 5% 5% 7% 10% 44%	4465
August	1st to 10th	Day	1 2 1 4 3 3 4 4 6% 10% 63%	2370
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 4 7% 9% 50%	2243
	21st to end	Day	5% 4 2 6% 5% 6% 6% 5% 8% 11% 43%	2442
September	1st to 10th	Day	9% 5% 3 6% 5% 5% 4 4 5% 7% 46%	1980
	11th to 20th	Day	10% 7% 2 6% 5% 4 6% 4 6% 7% 42%	1980
	21st to end	Day	9% 3 1 5% 5% 4 4 3 6% 7% 50%	1980
October	1st to 10th	Day	6% 4 2 5% 4 4 4 3 6% 8% 56%	1980
	11th to 20th	Day	11% 5% 1 4 3 4 4 3 5% 5% 54%	1908
	21st to end	Day	11% 5% 1 4 3 3 3 3 4 5% 59%	1980
November	1st to 10th	Day	12% 7% 2 5% 4 3 3 2 5% 6% 50%	1840
	11th to 20th	Day	8% 5% 2 5% 4 3 4 4 6% 6% 54%	1710
	21st to end	Day	13% 7% 3 6% 4 3 3 2 3 7% 50%	1710
December	1st to 10th	Day	12% 8% 2 4 3 2 3 2 6% 6% 51%	1710
	11th to 20th	Day	11% 7% 2 7% 4 3 3 3 5% 6% 48%	2161
	21st to end	Day	12% 6% 2 5% 3 2 3 2 3 4 59%	3135
January	1st to 10th	Night	11% 6% 4 6% 2 2 2 2 3 6% 56%	4108
	11th to 20th	Night	11% 4 1 3 2 1 2 2 3 5% 66%	4120
	21st to end	Night	14% 7% 2 6% 4 4 4 2 4 6% 46%	4240
February	1st to 10th	Night	12% 6% 3 6% 4 3 3 2 4 5% 52%	2280
	11th to 20th	Night	13% 7% 2 5% 3 4 3 2 3 5% 52%	2218
	21st to end	Night	13% 7% 2 5% 3 3 4 3 5% 6% 50%	1884
March	1st to 10th	Night	8% 7% 3 7% 5% 5% 4 4 5% 7% 45%	3549
	11th to 20th	Night	15% 8% 2 7% 5% 5% 4 4 6% 6% 37%	3480
	21st to end	Night	8% 7% 2 7% 4 4 4 3 4 6% 50%	3817
April	1st to 10th	Night	7% 6% 2 6% 5% 3 4 4 6% 6% 51%	2090
	11th to 20th	Night	10% 7% 3 7% 4 4 3 3 4 6% 49%	1960
	21st to end	Night	10% 6% 2 5% 5% 3 3 3 5% 7% 51%	1806
May	1st to 10th	Night	15% 10% 3 7% 4 4 3 3 4 6% 40%	2823
	11th to 20th	Night	8% 7% 3 6% 4 3 4 3 5% 7% 50%	2823
	21st to end	Night	9% 6% 3 6% 4 4 4 4 7% 8% 47%	3090
June	1st to 10th	Night	2 2 1 4 4 3 4 3 6% 10% 61%	1710
	11th to 20th	Night	4 3 1 4 4 3 3 3 6% 8% 62%	1710
	21st to end	Night	4 3 1 4 4 3 4 5% 5% 10% 56%	1710
July	1st to 10th	Night	4 3 2 4 4 4 4 4 6% 10% 56%	2850
	11th to 20th	Night	2 3 1 4 3 3 4 3 6% 9% 63%	2850
	21st to end	Night	6% 8% 2 5% 4 3 4 4 6% 10% 47%	3098
August	1st to 10th	Night	1 1 1 2 2 3 3 4 4 7% 73%	1784
	11th to 20th	Night	4 3 1 5% 4 4 4 5% 6% 10% 54%	1878
	21st to end	Night	4 4 1 5% 5% 4 4 4 7% 11% 50%	2122
September	1st to 10th	Night	6% 4 2 4 4 4 5% 4 6% 9% 52%	1980
	11th to 20th	Night	9% 6% 2 5% 4 4 4 4 7% 8% 46%	1980
	21st to end	Night	8% 4 2 4 3 4 5% 3 7% 7% 54%	1980
October	1st to 10th	Night	4 3 1 4 3 3 3 3 4 7% 63%	1980
	11th to 20th	Night	10% 5% 2 4 3 4 3 3 4 6% 56%	2033
	21st to end	Night	12% 5% 2 4 3 3 2 2 3 3 61%	2376
November	1st to 10th	Night	10% 5% 2 5% 3 3 2 2 4 6% 57%	2234
	11th to 20th	Night	7% 4 2 5% 3 4 4 3 5% 6% 58%	2470
	21st to end	Night	14% 5% 2 5% 4 4 3 3 5% 6% 49%	2470
December	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 5% 6% 54%	2470
	11th to 20th	Night	10% 9% 3 7% 3 4 4 2 4 6% 48%	3036
	21st to end	Night	11% 7% 2 5% 2 2 2 2 3 5% 57%	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	33% 2 3 15% 26% 20%	2848
	11th to 20th	Day	31% 3 5% 13% 32% 16%	2850
	21st to end	Day	36% 3 5% 13% 30% 13%	3455
February	1st to 10th	Day	37% 3 7% 13% 22% 18%	1900
	11th to 20th	Day	37% 3 6% 18% 19% 16%	1859
	21st to end	Day	35% 3 6% 16% 22% 18%	1570
March	1st to 10th	Day	39% 4 7% 13% 20% 17%	3306
	11th to 20th	Day	48% 7% 7% 11% 16% 10%	3480
	21st to end	Day	34% 5% 9% 17% 21% 14%	3814
April	1st to 10th	Day	39% 3 8% 18% 18% 14%	2090
	11th to 20th	Day	40% 4 7% 17% 22% 11%	2165
	21st to end	Day	38% 4 6% 22% 20% 11%	2370
May	1st to 10th	Day	45% 6% 11% 14% 18% 7%	4120
	11th to 20th	Day	39% 6% 7% 17% 21% 10%	4086
	21st to end	Day	38% 8% 10% 27% 13% 4	4489
June	1st to 10th	Day	27% 7% 12% 28% 22% 4	2470
	11th to 20th	Day	29% 5% 12% 26% 22% 6%	2470
	21st to end	Day	33% 7% 13% 24% 18% 5%	2470
July	1st to 10th	Day	31% 6% 16% 38% 8%	4056
	11th to 20th	Day	22% 6% 15% 36% 18% 4	4051
	21st to end	Day	32% 7% 17% 30% 13% 1	4325
August	1st to 10th	Day	17% 5% 12% 41% 22% 2	2356
	11th to 20th	Day	29% 6% 16% 32% 13% 4	2243
	21st to end	Day	32% 9% 15% 27% 13% 4	2442
September	1st to 10th	Day	38% 5% 10% 21% 18% 8%	1980
	11th to 20th	Day	40% 7% 11% 20% 18% 5%	1980
	21st to end	Day	32% 4 10% 22% 20% 12%	1980
October	1st to 10th	Day	27% 4 10% 22% 27% 10%	1980
	11th to 20th	Day	33% 4 6% 15% 24% 17%	1908
	21st to end	Day	29% 4 4 17% 26% 21%	1980
November	1st to 10th	Day	37% 2 8% 20% 21% 11%	1840
	11th to 20th	Day	31% 4 8% 18% 22% 17%	1710
	21st to end	Day	38% 2 6% 16% 22% 15%	1710
December	1st to 10th	Day	35% 2 8% 19% 25% 10%	1710
	11th to 20th	Day	37% 4 8% 12% 23% 17%	2159
	21st to end	Day	32% 2 4 15% 29% 19%	3135
January	1st to 10th	Night	33% 2 3 13% 28% 20%	4108
	11th to 20th	Night	24% 2 4 17% 28% 26%	4120
	21st to end	Night	39% 3 4 13% 27% 14%	4240
February	1st to 10th	Night	37% 2 7% 12% 22% 20%	2280
	11th to 20th	Night	36% 3 5% 17% 21% 18%	2218
	21st to end	Night	37% 3 6% 12% 22% 19%	1884
March	1st to 10th	Night	37% 5% 8% 14% 23% 13%	3549
	11th to 20th	Night	46% 6% 8% 13% 15% 11%	3480
	21st to end	Night	35% 5% 9% 18% 18% 14%	3817
April	1st to 10th	Night	34% 4 9% 20% 17% 17%	2090
	11th to 20th	Night	38% 4 8% 15% 19% 16%	1960
	21st to end	Night	36% 4 9% 20% 22% 10%	1806
May	1st to 10th	Night	46% 4 7% 20% 13% 10%	2850
	11th to 20th	Night	32% 7% 10% 23% 18% 11%	2824
	21st to end	Night	33% 6% 13% 29% 13% 5%	3099
June	1st to 10th	Night	19% 7% 17% 34% 21% 3	1710
	11th to 20th	Night	21% 4 16% 30% 22% 6%	1710
	21st to end	Night	25% 5% 15% 31% 19% 4	1710
July	1st to 10th	Night	22% 8% 24% 39% 7% 1	2805
	11th to 20th	Night	19% 6% 18% 37% 18% 2	2796
	21st to end	Night	31% 7% 22% 30% 10%	2999
August	1st to 10th	Night	11% 6% 18% 42% 22% 1	1774
	11th to 20th	Night	23% 8% 21% 31% 13% 4	1878
	21st to end	Night	27% 7% 22% 27% 14% 3	2122
September	1st to 10th	Night	30% 5% 14% 24% 19% 8%	1980
	11th to 20th	Night	35% 7% 15% 22% 17% 4	1980
	21st to end	Night	29% 5% 12% 21% 20% 12%	1980
October	1st to 10th	Night	22% 3 15% 26% 22% 11%	1980
	11th to 20th	Night	31% 4 8% 17% 23% 18%	2033
	21st to end	Night	31% 2 4 17% 24% 22%	2376
November	1st to 10th	Night	31% 2 7% 21% 24% 15%	2234
	11th to 20th	Night	28% 3 8% 22% 21% 18%	2470
	21st to end	Night	38% 3 7% 16% 21% 16%	2470
December	1st to 10th	Night	32% 3 8% 19% 24% 13%	2470
	11th to 20th	Night	39% 3 5% 12% 20% 21%	3037
	21st to end	Night	33% 3 4 14% 29% 17%	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	19% 16% 40% 21% 3 1	270
	11th to 20th	Day	22% 12% 35% 24% 6% 1	270
	21st to end	Day	16% 15% 40% 24% 4	297
February	1st to 10th	Day	24% 17% 34% 19% 6%	270
	11th to 20th	Day	22% 19% 40% 16% 3	270
	21st to end	Day	24% 18% 40% 16% 2	225
March	1st to 10th	Day	17% 19% 41% 20% 3	270
	11th to 20th	Day	20% 18% 36% 20% 7%	270
	21st to end	Day	18% 19% 45% 14% 4	297
April	1st to 10th	Day	17% 18% 44% 18% 3	270
	11th to 20th	Day	21% 15% 41% 20% 4	363
	21st to end	Day	17% 14% 42% 20% 6%	550
May	1st to 10th	Day	15% 11% 43% 25% 6%	653
	11th to 20th	Day	18% 8% 34% 26% 12% 1	675
	21st to end	Day	18% 5% 30% 33% 13% 1	734
June	1st to 10th	Day	6% 1 23% 43% 23% 4	680
	11th to 20th	Day	6% 2 23% 50% 17% 3	680
	21st to end	Day	7% 1 14% 43% 28% 6%	680
July	1st to 10th	Day	8% 1 9% 42% 29% 10%	671
	11th to 20th	Day	4 1 6% 46% 35% 8%	668
	21st to end	Day	4 1 6% 43% 35% 11%	739
August	1st to 10th	Day	2 4 44% 39% 12%	588
	11th to 20th	Day	9% 1 4 38% 36% 12%	477
	21st to end	Day	5% 1 5% 30% 44% 15%	489
September	1st to 10th	Day	9% 1 2 28% 40% 20%	270
	11th to 20th	Day	8% 6% 29% 41% 17%	270
	21st to end	Day	11% 1 4 34% 38% 11%	270
October	1st to 10th	Day	8% 2 13% 38% 31% 8%	270
	11th to 20th	Day	12% 3 29% 35% 18% 3	270
	21st to end	Day	22% 11% 27% 27% 12% 1	297
November	1st to 10th	Day	20% 6% 30% 34% 9% 2	270
	11th to 20th	Day	19% 10% 29% 27% 10% 5%	270
	21st to end	Day	23% 17% 32% 20% 6% 2	270
December	1st to 10th	Day	16% 8% 35% 30% 8% 3	270
	11th to 20th	Day	19% 17% 37% 21% 7%	270
	21st to end	Day	17% 12% 40% 24% 7%	297
January	1st to 10th	Night	16% 12% 37% 28% 6% 1	950
	11th to 20th	Night	17% 12% 36% 29% 5%	950
	21st to end	Night	18% 11% 39% 25% 7%	870
February	1st to 10th	Night	19% 14% 40% 22% 5%	760
	11th to 20th	Night	18% 15% 42% 22% 2	744
	21st to end	Night	20% 16% 45% 18% 1	628
March	1st to 10th	Night	17% 16% 41% 25% 1	653
	11th to 20th	Night	17% 11% 41% 27% 5%	570
	21st to end	Night	13% 13% 51% 21% 3	627
April	1st to 10th	Night	10% 15% 50% 22% 3	570
	11th to 20th	Night	16% 13% 48% 20% 3	563
	21st to end	Night	15% 9% 51% 19% 6%	570
May	1st to 10th	Night	15% 9% 48% 25% 3	570
	11th to 20th	Night	12% 6% 41% 31% 9% 1	561
	21st to end	Night	14% 4 40% 33% 10%	617
June	1st to 10th	Night	3 1 28% 48% 19% 1	570
	11th to 20th	Night	5% 3 38% 43% 11%	570
	21st to end	Night	6% 1 21% 49% 21% 2	570
July	1st to 10th	Night	8% 13% 52% 26% 2	555
	11th to 20th	Night	3 12% 58% 25% 2	552
	21st to end	Night	4 10% 59% 23% 3	624
August	1st to 10th	Night	1 1 7% 60% 29% 3	567
	11th to 20th	Night	5% 6% 55% 29% 4	564
	21st to end	Night	5% 1 6% 50% 33% 5%	624
September	1st to 10th	Night	9% 10% 43% 32% 5%	540
	11th to 20th	Night	13% 7% 42% 34% 3	540
	21st to end	Night	10% 14% 46% 28% 2	540
October	1st to 10th	Night	6% 1 18% 50% 23% 2	540
	11th to 20th	Night	13% 3 26% 41% 15% 2	593
	21st to end	Night	16% 7% 31% 28% 16% 2	792
November	1st to 10th	Night	13% 5% 31% 36% 14% 1	754
	11th to 20th	Night	11% 8% 33% 34% 13% 1	950
	21st to end	Night	17% 11% 33% 29% 9% 1	950
December	1st to 10th	Night	15% 8% 35% 34% 8% 1	950
	11th to 20th	Night	20% 9% 36% 28% 6%	950
	21st to end	Night	15% 12% 37% 30% 6%	1045

Page generated at 2024-08-27 08:49:42. Version ac07

Copyright © 2024 Attilla Danko.