White Tail Run Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White Tail Run Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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	13% 5% 2 4 4 3 4 4 5% 7% 48%	74970
	Night	11% 5% 2 4 4 2 3 4 5% 7% 54%	75104
Transparency	Day	35% 5% 10% 20% 19% 10%	74699
	Night	31% 5% 11% 20% 20% 13%	74896
Seeing	Day	14% 7% 24% 32% 19% 3	13659
	Night	14% 7% 27% 38% 14% 1	23776

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% 6% 1 3 3 2 2 3 4 5% 57%	1707
	11th to 20th	Day	15% 5% 3 3 4 2 3 2 3 6% 52%	1805
	21st to end	Day	14% 6% 2 4 3 2 3 4 3 6% 53%	2040
February	1st to 10th	Day	14% 6% 2 4 4 2 3 3 4 5% 51%	1800
	11th to 20th	Day	16% 7% 2 5% 4 2 4 4 4 5% 47%	1749
	21st to end	Day	14% 5% 2 3 3 2 3 3 4 6% 55%	1480
March	1st to 10th	Day	19% 7% 2 4 4 2 3 3 4 6% 46%	1847
	11th to 20th	Day	17% 6% 2 5% 4 2 3 4 5% 6% 46%	1980
	21st to end	Day	18% 6% 2 3 3 2 3 3 5% 6% 50%	2178
April	1st to 10th	Day	16% 7% 3 4 3 2 3 4 5% 7% 46%	1986
	11th to 20th	Day	17% 4 2 4 5% 2 3 3 5% 7% 48%	2134
	21st to end	Day	16% 5% 3 4 5% 2 3 3 3 6% 49%	2160
May	1st to 10th	Day	16% 6% 2 4 5% 3 5% 4 6% 8% 43%	2334
	11th to 20th	Day	15% 5% 3 5% 4 3 5% 5% 5% 8% 41%	2302
	21st to end	Day	16% 6% 3 6% 6% 4 5% 5% 5% 7% 37%	2531
June	1st to 10th	Day	7% 3 1 4 4 3 4 5% 6% 10% 51%	2340
	11th to 20th	Day	9% 4 2 4 5% 3 5% 5% 6% 8% 49%	2340
	21st to end	Day	9% 5% 2 5% 7% 4 6% 8% 5% 9% 38%	2340
July	1st to 10th	Day	13% 6% 4 6% 6% 3 5% 6% 6% 8% 38%	2340
	11th to 20th	Day	7% 3 1 4 4 2 4 5% 6% 8% 55%	2340
	21st to end	Day	6% 3 2 3 4 3 5% 5% 6% 11% 52%	2491
August	1st to 10th	Day	3 2 1 3 3 2 5% 4 5% 11% 61%	2149
	11th to 20th	Day	7% 3 2 4 5% 3 5% 6% 5% 9% 50%	2123
	21st to end	Day	8% 4 1 6% 5% 4 6% 6% 6% 8% 47%	2376
September	1st to 10th	Day	11% 6% 3 6% 6% 5% 6% 5% 5% 8% 39%	1985
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 6% 6% 7% 41%	1980
	21st to end	Day	9% 4 2 5% 6% 4 4 5% 7% 7% 46%	1980
October	1st to 10th	Day	8% 5% 2 5% 4 2 4 4 6% 7% 52%	1980
	11th to 20th	Day	16% 4 2 3 4 2 4 3 5% 7% 50%	1980
	21st to end	Day	14% 5% 2 4 3 2 3 3 3 5% 57%	1985
November	1st to 10th	Day	16% 7% 2 4 4 2 3 3 5% 6% 48%	1782
	11th to 20th	Day	14% 5% 3 5% 4 2 3 4 4 5% 51%	1710
	21st to end	Day	17% 7% 3 4 3 3 3 3 3 5% 49%	1710
December	1st to 10th	Day	15% 7% 2 5% 4 1 3 3 4 6% 50%	1710
	11th to 20th	Day	16% 7% 3 5% 5% 2 4 3 4 4 47%	2161
	21st to end	Day	14% 6% 2 3 3 2 3 3 4 5% 57%	3135
January	1st to 10th	Night	13% 6% 1 3 3 2 3 3 3 6% 57%	2458
	11th to 20th	Night	14% 6% 2 4 4 2 3 3 4 5% 54%	2390
	21st to end	Night	16% 6% 3 4 4 2 2 3 4 5% 51%	2460
February	1st to 10th	Night	13% 6% 2 3 3 2 3 3 4 6% 56%	2160
	11th to 20th	Night	16% 6% 2 3 3 2 3 4 3 5% 54%	2098
	21st to end	Night	14% 5% 2 4 4 2 4 3 4 7% 51%	1776
March	1st to 10th	Night	15% 6% 2 5% 4 2 4 3 5% 8% 47%	2111
	11th to 20th	Night	14% 6% 2 4 4 2 4 4 4 5% 49%	1980
	21st to end	Night	13% 5% 2 3 3 3 2 3 4 6% 54%	2178
April	1st to 10th	Night	10% 5% 2 4 5% 3 4 4 5% 8% 52%	1969
	11th to 20th	Night	14% 5% 2 5% 4 3 4 4 4 6% 50%	1777
	21st to end	Night	15% 5% 3 5% 4 2 3 3 4 5% 51%	1800
May	1st to 10th	Night	11% 5% 3 5% 4 2 3 5% 5% 7% 50%	1625
	11th to 20th	Night	12% 6% 2 5% 4 2 4 4 4 7% 48%	1593
	21st to end	Night	13% 5% 2 5% 4 3 4 4 6% 8% 46%	1745
June	1st to 10th	Night	3 3 1 2 2 2 3 4 7% 9% 63%	1620
	11th to 20th	Night	4 3 1 3 4 2 4 5% 6% 9% 59%	1620
	21st to end	Night	7% 3 2 4 4 2 4 5% 6% 10% 53%	1620
July	1st to 10th	Night	8% 6% 2 4 5% 3 5% 5% 6% 10% 45%	1620
	11th to 20th	Night	3 2 1 3 3 2 3 4 6% 9% 63%	1620
	21st to end	Night	5% 2 1 3 3 2 4 5% 6% 11% 60%	1822
August	1st to 10th	Night	2 1 1 2 3 2 3 4 4 8% 71%	1790
	11th to 20th	Night	5% 3 2 3 4 2 4 6% 6% 10% 56%	1778
	21st to end	Night	6% 3 2 4 5% 3 5% 6% 7% 8% 50%	1980
September	1st to 10th	Night	8% 5% 3 4 5% 3 5% 5% 7% 9% 46%	1973
	11th to 20th	Night	10% 6% 3 6% 3 3 3 4 6% 9% 48%	1980
	21st to end	Night	8% 4 2 5% 3 2 4 6% 7% 8% 51%	1980
October	1st to 10th	Night	8% 4 2 3 4 2 3 4 4 8% 60%	1980
	11th to 20th	Night	14% 4 2 4 3 2 3 4 4 6% 55%	1980
	21st to end	Night	13% 4 1 3 3 1 2 2 3 4 65%	2352
November	1st to 10th	Night	13% 6% 1 4 3 2 2 3 4 6% 56%	2291
	11th to 20th	Night	11% 5% 2 4 3 2 3 4 5% 6% 56%	2470
	21st to end	Night	17% 5% 2 3 3 2 3 4 4 6% 50%	2470
December	1st to 10th	Night	15% 5% 1 3 3 2 3 3 5% 6% 53%	2470
	11th to 20th	Night	16% 6% 2 5% 4 2 3 4 3 5% 50%	3036
	21st to end	Night	16% 6% 1 3 3 1 2 3 4 7% 55%	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	31% 3 5% 17% 24% 20%	1708
	11th to 20th	Day	35% 3 6% 16% 22% 18%	1805
	21st to end	Day	34% 4 7% 13% 24% 19%	2040
February	1st to 10th	Day	37% 4 5% 13% 22% 20%	1800
	11th to 20th	Day	40% 3 6% 16% 21% 14%	1759
	21st to end	Day	33% 3 9% 15% 21% 19%	1480
March	1st to 10th	Day	43% 3 7% 16% 18% 14%	1847
	11th to 20th	Day	40% 5% 6% 14% 16% 18%	1980
	21st to end	Day	36% 4 9% 16% 19% 16%	2178
April	1st to 10th	Day	39% 4 8% 16% 19% 14%	1986
	11th to 20th	Day	36% 4 7% 20% 16% 16%	2134
	21st to end	Day	38% 4 7% 18% 18% 14%	2160
May	1st to 10th	Day	39% 5% 10% 18% 20% 9%	2334
	11th to 20th	Day	41% 6% 10% 20% 18% 5%	2306
	21st to end	Day	45% 7% 10% 19% 17% 2	2531
June	1st to 10th	Day	28% 7% 14% 28% 19% 4	2340
	11th to 20th	Day	31% 7% 13% 26% 18% 6%	2340
	21st to end	Day	39% 8% 13% 21% 15% 5%	2340
July	1st to 10th	Day	41% 8% 15% 24% 12% 1	2276
	11th to 20th	Day	24% 7% 18% 29% 20% 2	2271
	21st to end	Day	21% 8% 22% 35% 13% 1	2353
August	1st to 10th	Day	19% 7% 15% 40% 20% 1	2136
	11th to 20th	Day	28% 8% 16% 31% 13% 3	2123
	21st to end	Day	32% 7% 15% 28% 14% 3	2376
September	1st to 10th	Day	42% 8% 10% 19% 16% 6%	1985
	11th to 20th	Day	39% 8% 11% 21% 17% 4	1980
	21st to end	Day	35% 7% 11% 20% 19% 9%	1980
October	1st to 10th	Day	31% 6% 10% 23% 24% 7%	1980
	11th to 20th	Day	35% 5% 9% 16% 21% 15%	1980
	21st to end	Day	32% 4 4 15% 26% 19%	1985
November	1st to 10th	Day	38% 4 9% 18% 19% 11%	1782
	11th to 20th	Day	37% 3 8% 17% 20% 16%	1710
	21st to end	Day	40% 3 5% 17% 19% 15%	1710
December	1st to 10th	Day	37% 3 8% 18% 23% 11%	1710
	11th to 20th	Day	42% 3 5% 11% 21% 18%	2159
	21st to end	Day	33% 2 4 14% 30% 16%	3135
January	1st to 10th	Night	31% 2 5% 15% 23% 22%	2458
	11th to 20th	Night	34% 3 5% 16% 23% 19%	2390
	21st to end	Night	37% 3 5% 14% 20% 22%	2460
February	1st to 10th	Night	31% 4 8% 14% 20% 23%	2160
	11th to 20th	Night	35% 3 6% 16% 21% 18%	2098
	21st to end	Night	34% 3 8% 15% 20% 20%	1776
March	1st to 10th	Night	36% 5% 11% 15% 19% 14%	2111
	11th to 20th	Night	38% 5% 8% 11% 17% 20%	1980
	21st to end	Night	32% 5% 10% 18% 16% 18%	2178
April	1st to 10th	Night	31% 4 13% 18% 17% 17%	1969
	11th to 20th	Night	37% 4 10% 15% 16% 18%	1777
	21st to end	Night	36% 4 10% 19% 16% 15%	1800
May	1st to 10th	Night	34% 5% 12% 20% 17% 12%	1625
	11th to 20th	Night	35% 6% 11% 25% 18% 6%	1594
	21st to end	Night	35% 7% 15% 25% 15% 3	1746
June	1st to 10th	Night	18% 6% 19% 33% 21% 3	1620
	11th to 20th	Night	22% 6% 15% 30% 22% 6%	1620
	21st to end	Night	26% 7% 19% 26% 17% 5%	1620
July	1st to 10th	Night	33% 8% 21% 25% 12% 1	1575
	11th to 20th	Night	18% 8% 16% 32% 23% 3	1566
	21st to end	Night	16% 8% 26% 36% 14% 1	1721
August	1st to 10th	Night	12% 6% 21% 40% 19% 2	1779
	11th to 20th	Night	22% 8% 21% 29% 16% 3	1778
	21st to end	Night	28% 10% 20% 25% 15% 3	1980
September	1st to 10th	Night	33% 8% 14% 21% 17% 7%	1973
	11th to 20th	Night	33% 8% 19% 21% 15% 5%	1980
	21st to end	Night	29% 7% 12% 22% 19% 10%	1980
October	1st to 10th	Night	25% 5% 13% 25% 21% 11%	1980
	11th to 20th	Night	31% 4 10% 18% 22% 15%	1980
	21st to end	Night	26% 2 6% 16% 27% 22%	2352
November	1st to 10th	Night	32% 4 7% 19% 24% 14%	2291
	11th to 20th	Night	29% 5% 8% 20% 20% 18%	2470
	21st to end	Night	36% 4 8% 15% 20% 17%	2470
December	1st to 10th	Night	33% 4 9% 18% 22% 14%	2470
	11th to 20th	Night	38% 3 6% 15% 17% 21%	3037
	21st to end	Night	32% 3 5% 15% 28% 18%	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	20% 13% 34% 28% 6%	270
	11th to 20th	Day	21% 11% 35% 23% 9% 1	270
	21st to end	Day	17% 15% 36% 25% 7%	282
February	1st to 10th	Day	26% 14% 24% 25% 10%	240
	11th to 20th	Day	25% 15% 33% 20% 7% 1	240
	21st to end	Day	21% 18% 42% 16% 4	198
March	1st to 10th	Day	23% 15% 42% 20% 1	240
	11th to 20th	Day	20% 18% 42% 17% 3	240
	21st to end	Day	20% 16% 45% 16% 2	264
April	1st to 10th	Day	19% 17% 40% 22% 1	246
	11th to 20th	Day	15% 18% 42% 22% 3	412
	21st to end	Day	15% 16% 44% 22% 4	420
May	1st to 10th	Day	15% 13% 39% 28% 5%	597
	11th to 20th	Day	21% 6% 35% 29% 8% 1	625
	21st to end	Day	17% 9% 31% 35% 8%	679
June	1st to 10th	Day	7% 2 21% 50% 18% 2	630
	11th to 20th	Day	10% 2 21% 49% 16% 1	630
	21st to end	Day	10% 2 20% 36% 27% 5%	630
July	1st to 10th	Day	13% 4 12% 35% 30% 6%	621
	11th to 20th	Day	6% 1 6% 41% 43% 4	618
	21st to end	Day	5% 1 5% 43% 41% 5%	629
August	1st to 10th	Day	2 6% 44% 40% 8%	447
	11th to 20th	Day	7% 7% 36% 41% 8%	437
	21st to end	Day	7% 1 7% 35% 39% 11%	495
September	1st to 10th	Day	9% 1 8% 30% 41% 11%	275
	11th to 20th	Day	7% 1 5% 27% 48% 12%	270
	21st to end	Day	10% 1 9% 34% 38% 7%	270
October	1st to 10th	Day	8% 6% 13% 41% 27% 5%	270
	11th to 20th	Day	14% 4 19% 44% 17% 2	270
	21st to end	Day	20% 13% 25% 27% 13% 3	297
November	1st to 10th	Day	21% 4 29% 31% 13% 1	270
	11th to 20th	Day	23% 9% 26% 27% 12% 4	270
	21st to end	Day	22% 14% 35% 20% 7% 2	270
December	1st to 10th	Day	19% 9% 28% 31% 11% 2	270
	11th to 20th	Day	22% 17% 27% 25% 8%	270
	21st to end	Day	19% 9% 34% 27% 9% 1	297
January	1st to 10th	Night	17% 8% 30% 36% 9% 1	950
	11th to 20th	Night	18% 9% 29% 37% 8%	870
	21st to end	Night	21% 9% 29% 33% 8%	820
February	1st to 10th	Night	18% 11% 31% 34% 6%	720
	11th to 20th	Night	20% 12% 34% 29% 6%	704
	21st to end	Night	20% 10% 42% 27% 2	592
March	1st to 10th	Night	20% 10% 39% 26% 4 1	671
	11th to 20th	Night	18% 11% 36% 32% 4	540
	21st to end	Night	14% 12% 47% 22% 4	594
April	1st to 10th	Night	10% 11% 48% 30% 2	540
	11th to 20th	Night	16% 14% 48% 20% 2	533
	21st to end	Night	16% 11% 48% 22% 3 1	540
May	1st to 10th	Night	12% 12% 43% 29% 3	540
	11th to 20th	Night	17% 6% 39% 33% 6%	531
	21st to end	Night	12% 8% 38% 35% 8%	584
June	1st to 10th	Night	4 1 30% 52% 11%	540
	11th to 20th	Night	7% 1 39% 46% 7%	540
	21st to end	Night	6% 3 25% 49% 17%	540
July	1st to 10th	Night	10% 2 15% 53% 19% 1	525
	11th to 20th	Night	4 1 15% 55% 25%	522
	21st to end	Night	4 1 10% 58% 26% 1	591
August	1st to 10th	Night	1 8% 58% 31% 1	537
	11th to 20th	Night	5% 1 9% 52% 32% 2	534
	21st to end	Night	5% 2 10% 48% 34% 2	594
September	1st to 10th	Night	8% 1 12% 43% 34% 2	540
	11th to 20th	Night	12% 1 9% 46% 31% 1	540
	21st to end	Night	11% 1 13% 40% 31% 3	540
October	1st to 10th	Night	9% 2 15% 48% 24% 2	540
	11th to 20th	Night	14% 3 23% 39% 19% 1	540
	21st to end	Night	14% 8% 25% 31% 21% 2	768
November	1st to 10th	Night	16% 5% 19% 39% 19% 2	811
	11th to 20th	Night	13% 7% 23% 39% 16% 2	950
	21st to end	Night	20% 9% 24% 35% 12% 1	950
December	1st to 10th	Night	17% 7% 23% 39% 13% 1	950
	11th to 20th	Night	22% 10% 25% 34% 9%	950
	21st to end	Night	18% 9% 26% 38% 8% 1	1045

Page generated at 2024-01-24 08:37:26. Version ac07

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