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 2025-02-06.

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% 6% 2 5% 4 4 4 3 5% 7% 49%	109071
	Night	13% 5% 2 4 3 3 3 3 5% 7% 54%	109417
Transparency	Day	34% 4 9% 21% 20% 12%	112982
	Night	31% 4 10% 20% 20% 14%	113634
Seeing	Day	14% 8% 25% 32% 18% 3	15019
	Night	14% 7% 27% 38% 13% 1	25118

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	14% 6% 1 3 2 2 2 2 3 4 59%	4077
	11th to 20th	Day	10% 6% 2 3 3 2 3 3 4 6% 57%	4310
	21st to end	Day	21% 7% 2 4 2 2 3 3 3 6% 47%	4994
February	1st to 10th	Day	14% 7% 2 5% 4 3 3 3 4 4 51%	1950
	11th to 20th	Day	16% 7% 2 6% 3 3 4 3 4 4 48%	1849
	21st to end	Day	14% 6% 1 4 3 3 3 3 4 6% 54%	1570
March	1st to 10th	Day	17% 8% 2 5% 4 3 3 2 4 5% 47%	3216
	11th to 20th	Day	22% 10% 3 8% 4 3 3 3 4 4 36%	3480
	21st to end	Day	14% 6% 2 4 3 3 4 4 6% 7% 48%	3814
April	1st to 10th	Day	14% 7% 2 5% 3 3 3 4 5% 6% 47%	2097
	11th to 20th	Day	16% 5% 2 5% 4 3 3 3 5% 7% 46%	2254
	21st to end	Day	16% 6% 2 5% 4 3 3 3 3 6% 48%	2280
May	1st to 10th	Day	20% 7% 2 5% 4 4 4 3 5% 7% 38%	4076
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 45%	4082
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	4477
June	1st to 10th	Day	7% 4 1 5% 4 4 5% 4 6% 10% 50%	2470
	11th to 20th	Day	9% 5% 2 4 4 4 4 4 7% 8% 48%	2470
	21st to end	Day	9% 6% 2 6% 5% 7% 6% 6% 6% 9% 39%	2470
July	1st to 10th	Day	8% 4 2 6% 4 4 4 4 5% 8% 50%	4120
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 9% 51%	4120
	21st to end	Day	10% 5% 1 5% 4 4 5% 5% 7% 11% 43%	4357
August	1st to 10th	Day	2 2 1 3 2 3 3 3 5% 8% 68%	3785
	11th to 20th	Day	4 2 1 3 3 3 4 3 5% 9% 62%	3726
	21st to end	Day	6% 4 1 6% 4 5% 5% 4 6% 9% 50%	4180
September	1st to 10th	Day	11% 7% 3 7% 5% 6% 5% 4 5% 8% 40%	2095
	11th to 20th	Day	11% 6% 2 7% 5% 6% 5% 5% 6% 7% 42%	2090
	21st to end	Day	9% 5% 2 6% 5% 5% 4 4 7% 7% 47%	2090
October	1st to 10th	Day	8% 5% 2 5% 4 4 3 3 5% 7% 54%	2090
	11th to 20th	Day	15% 4 2 4 4 3 4 2 5% 7% 51%	2090
	21st to end	Day	14% 5% 2 4 2 2 3 2 3 5% 57%	2095
November	1st to 10th	Day	16% 8% 2 4 3 3 2 3 5% 6% 48%	1878
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 4 6% 52%	1800
	21st to end	Day	16% 8% 3 4 3 3 3 3 3 5% 50%	1800
December	1st to 10th	Day	24% 9% 2 6% 4 2 3 2 3 4 39%	2940
	11th to 20th	Day	17% 9% 2 5% 4 3 3 3 4 5% 45%	3391
	21st to end	Day	13% 6% 2 3 2 2 2 2 3 4 61%	4488
January	1st to 10th	Night	13% 5% 1 3 2 2 3 2 3 7% 58%	5888
	11th to 20th	Night	10% 3 1 3 2 2 2 2 5% 6% 65%	5698
	21st to end	Night	26% 6% 2 5% 3 2 2 2 3 4 45%	5984
February	1st to 10th	Night	12% 7% 2 4 2 3 2 3 4 5% 56%	2340
	11th to 20th	Night	15% 7% 1 4 3 3 3 3 4 4 53%	2218
	21st to end	Night	13% 5% 1 5% 4 3 4 3 5% 7% 51%	1884
March	1st to 10th	Night	12% 8% 2 5% 3 3 4 3 5% 7% 48%	3643
	11th to 20th	Night	17% 9% 3 7% 4 4 4 3 4 5% 40%	3480
	21st to end	Night	14% 8% 3 5% 3 3 3 3 4 6% 50%	3817
April	1st to 10th	Night	10% 6% 2 5% 4 4 3 3 5% 7% 52%	2078
	11th to 20th	Night	14% 6% 2 5% 4 4 3 3 4 5% 49%	1877
	21st to end	Night	15% 7% 2 5% 4 3 3 3 4 5% 50%	1900
May	1st to 10th	Night	19% 9% 2 5% 3 2 3 3 5% 6% 43%	2828
	11th to 20th	Night	11% 5% 2 5% 3 3 4 2 4 6% 55%	2823
	21st to end	Night	11% 5% 2 5% 3 4 4 3 6% 8% 50%	3090
June	1st to 10th	Night	3 3 1 3 2 2 4 3 7% 9% 62%	1710
	11th to 20th	Night	5% 3 1 4 3 3 4 5% 6% 8% 58%	1710
	21st to end	Night	7% 4 2 4 4 3 4 4 6% 10% 53%	1710
July	1st to 10th	Night	5% 4 2 3 3 3 4 3 6% 9% 58%	2850
	11th to 20th	Night	5% 3 1 4 3 3 4 4 7% 9% 57%	2850
	21st to end	Night	11% 6% 2 5% 3 4 4 4 6% 9% 48%	3187
August	1st to 10th	Night	1 1 1 2 2 2 2 3 5% 8% 74%	3155
	11th to 20th	Night	3 2 1 3 3 3 4 4 5% 9% 64%	3113
	21st to end	Night	5% 4 1 4 3 4 4 4 7% 10% 53%	3487
September	1st to 10th	Night	9% 6% 3 5% 4 4 4 4 7% 9% 47%	2083
	11th to 20th	Night	10% 6% 2 6% 3 4 3 4 6% 8% 49%	2090
	21st to end	Night	8% 5% 2 5% 3 3 4 4 7% 7% 52%	2090
October	1st to 10th	Night	8% 4 2 3 3 2 3 3 4 7% 61%	2090
	11th to 20th	Night	13% 4 1 5% 2 3 3 3 4 6% 56%	2090
	21st to end	Night	13% 4 1 3 2 2 2 2 3 4 65%	2483
November	1st to 10th	Night	13% 7% 1 4 3 2 3 2 4 6% 55%	2415
	11th to 20th	Night	11% 5% 2 4 3 2 3 3 5% 6% 57%	2600
	21st to end	Night	16% 5% 2 3 3 3 3 3 5% 6% 51%	2600
December	1st to 10th	Night	25% 7% 2 4 3 4 3 3 5% 5% 40%	4250
	11th to 20th	Night	19% 7% 2 4 3 3 3 2 3 4 50%	4816
	21st to end	Night	15% 6% 1 3 2 2 2 2 3 6% 59%	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	31% 3 3 19% 25% 20%	4078
	11th to 20th	Day	30% 2 4 16% 26% 23%	4310
	21st to end	Day	41% 3 5% 12% 26% 14%	4994
February	1st to 10th	Day	37% 4 5% 13% 21% 20%	1950
	11th to 20th	Day	39% 3 6% 16% 21% 15%	1859
	21st to end	Day	32% 3 9% 16% 22% 18%	1570
March	1st to 10th	Day	43% 3 5% 13% 20% 16%	3216
	11th to 20th	Day	51% 4 5% 11% 16% 12%	3480
	21st to end	Day	34% 4 10% 15% 17% 20%	3814
April	1st to 10th	Day	38% 4 8% 16% 18% 16%	2097
	11th to 20th	Day	37% 4 7% 20% 16% 16%	2254
	21st to end	Day	39% 4 7% 18% 17% 14%	2280
May	1st to 10th	Day	45% 5% 10% 15% 15% 9%	4114
	11th to 20th	Day	38% 5% 8% 20% 19% 9%	4086
	21st to end	Day	38% 7% 12% 25% 15% 3	4489
June	1st to 10th	Day	28% 7% 14% 29% 19% 4	2470
	11th to 20th	Day	31% 7% 12% 25% 19% 6%	2470
	21st to end	Day	39% 7% 13% 21% 15% 5%	2470
July	1st to 10th	Day	31% 5% 17% 35% 11% 1	4056
	11th to 20th	Day	28% 5% 20% 30% 15% 2	4051
	21st to end	Day	31% 7% 18% 28% 15% 1	4220
August	1st to 10th	Day	15% 4 11% 42% 27% 1	3772
	11th to 20th	Day	19% 5% 20% 42% 12% 2	3762
	21st to end	Day	29% 5% 17% 26% 20% 2	4179
September	1st to 10th	Day	41% 8% 9% 18% 16% 7%	2095
	11th to 20th	Day	38% 8% 10% 22% 17% 5%	2090
	21st to end	Day	34% 6% 11% 20% 18% 12%	2090
October	1st to 10th	Day	20% 4 6% 13% 23% 34%	3480
	11th to 20th	Day	32% 3 7% 16% 18% 25%	3458
	21st to end	Day	30% 3 4 15% 36% 12%	3433
November	1st to 10th	Day	39% 4 9% 17% 19% 11%	1878
	11th to 20th	Day	35% 2 7% 18% 20% 18%	1800
	21st to end	Day	40% 3 5% 18% 19% 15%	1800
December	1st to 10th	Day	51% 3 5% 14% 17% 10%	2940
	11th to 20th	Day	43% 2 6% 15% 18% 15%	3389
	21st to end	Day	30% 2 3 15% 29% 21%	4488
January	1st to 10th	Night	29% 2 6% 16% 28% 19%	5888
	11th to 20th	Night	23% 2 4 18% 26% 28%	5698
	21st to end	Night	45% 2 4 11% 21% 18%	5984
February	1st to 10th	Night	31% 4 8% 14% 21% 23%	2340
	11th to 20th	Night	35% 3 6% 16% 21% 18%	2218
	21st to end	Night	34% 3 7% 16% 21% 20%	1884
March	1st to 10th	Night	36% 5% 10% 14% 21% 15%	3643
	11th to 20th	Night	46% 6% 8% 12% 14% 14%	3480
	21st to end	Night	36% 5% 9% 16% 15% 19%	3817
April	1st to 10th	Night	31% 4 12% 17% 17% 18%	2078
	11th to 20th	Night	37% 5% 10% 14% 16% 18%	1877
	21st to end	Night	38% 4 9% 18% 16% 15%	1900
May	1st to 10th	Night	41% 5% 10% 18% 14% 13%	2855
	11th to 20th	Night	31% 5% 10% 23% 21% 10%	2824
	21st to end	Night	32% 7% 13% 28% 14% 8%	3099
June	1st to 10th	Night	18% 6% 18% 34% 21% 3	1710
	11th to 20th	Night	23% 5% 14% 29% 23% 6%	1710
	21st to end	Night	26% 7% 18% 27% 17% 5%	1710
July	1st to 10th	Night	23% 5% 23% 38% 9% 1	2805
	11th to 20th	Night	24% 7% 20% 30% 18% 2	2796
	21st to end	Night	32% 6% 21% 29% 11% 1	3086
August	1st to 10th	Night	10% 4 17% 42% 26% 1	3144
	11th to 20th	Night	18% 5% 27% 38% 10% 2	3143
	21st to end	Night	26% 9% 20% 27% 17% 2	3487
September	1st to 10th	Night	34% 7% 14% 20% 17% 8%	2083
	11th to 20th	Night	32% 7% 18% 21% 16% 6%	2090
	21st to end	Night	29% 7% 12% 22% 18% 12%	2090
October	1st to 10th	Night	17% 3 7% 15% 21% 36%	3480
	11th to 20th	Night	27% 3 7% 13% 25% 24%	3460
	21st to end	Night	24% 2 5% 16% 37% 16%	4083
November	1st to 10th	Night	33% 4 7% 18% 23% 15%	2415
	11th to 20th	Night	29% 4 8% 20% 21% 19%	2600
	21st to end	Night	35% 4 8% 16% 20% 17%	2600
December	1st to 10th	Night	48% 3 8% 14% 13% 14%	4250
	11th to 20th	Night	40% 2 6% 14% 20% 18%	4817
	21st to end	Night	30% 3 4 17% 27% 20%	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	22% 11% 35% 26% 6%	300
	11th to 20th	Day	20% 14% 35% 22% 8% 1	300
	21st to end	Day	18% 17% 34% 23% 8%	330
February	1st to 10th	Day	26% 15% 23% 26% 9% 1	285
	11th to 20th	Day	23% 17% 33% 20% 6% 1	270
	21st to end	Day	20% 16% 43% 17% 4	225
March	1st to 10th	Day	22% 17% 41% 19% 1	270
	11th to 20th	Day	21% 19% 41% 16% 3	270
	21st to end	Day	20% 18% 44% 15% 2	297
April	1st to 10th	Day	18% 20% 39% 22% 1	277
	11th to 20th	Day	15% 19% 42% 21% 3	452
	21st to end	Day	14% 17% 44% 21% 3	460
May	1st to 10th	Day	17% 13% 38% 27% 5%	647
	11th to 20th	Day	20% 7% 36% 28% 7% 1	675
	21st to end	Day	16% 9% 32% 34% 8%	734
June	1st to 10th	Day	7% 3 23% 49% 17% 2	680
	11th to 20th	Day	10% 3 23% 48% 15% 1	680
	21st to end	Day	10% 2 20% 36% 27% 4	680
July	1st to 10th	Day	12% 4 13% 36% 30% 6%	671
	11th to 20th	Day	6% 1 7% 41% 41% 4	668
	21st to end	Day	6% 1 7% 42% 39% 5%	680
August	1st to 10th	Day	2 7% 43% 41% 7%	487
	11th to 20th	Day	6% 8% 38% 40% 8%	477
	21st to end	Day	7% 1 6% 36% 38% 11%	539
September	1st to 10th	Day	9% 2 10% 31% 38% 10%	305
	11th to 20th	Day	7% 2 8% 28% 45% 11%	300
	21st to end	Day	9% 2 9% 36% 37% 7%	300
October	1st to 10th	Day	7% 5% 12% 41% 28% 6%	300
	11th to 20th	Day	13% 4 20% 44% 17% 2	300
	21st to end	Day	18% 12% 26% 28% 13% 3	330
November	1st to 10th	Day	21% 6% 30% 29% 13% 1	300
	11th to 20th	Day	22% 8% 27% 26% 12% 4	300
	21st to end	Day	21% 13% 36% 20% 8% 2	300
December	1st to 10th	Day	20% 11% 29% 28% 10% 2	300
	11th to 20th	Day	23% 16% 27% 24% 9% 1	300
	21st to end	Day	20% 9% 33% 28% 10% 1	330
January	1st to 10th	Night	17% 8% 30% 36% 9% 1	1000
	11th to 20th	Night	18% 10% 30% 35% 7%	915
	21st to end	Night	22% 9% 29% 33% 7%	880
February	1st to 10th	Night	18% 11% 31% 33% 7%	780
	11th to 20th	Night	20% 12% 34% 28% 6%	744
	21st to end	Night	19% 10% 43% 27% 2	628
March	1st to 10th	Night	20% 11% 38% 26% 4 1	708
	11th to 20th	Night	18% 11% 37% 31% 4	570
	21st to end	Night	15% 13% 46% 21% 4	627
April	1st to 10th	Night	11% 12% 46% 29% 2	570
	11th to 20th	Night	17% 14% 48% 19% 2	563
	21st to end	Night	17% 12% 46% 22% 3 1	570
May	1st to 10th	Night	15% 12% 42% 28% 3	570
	11th to 20th	Night	16% 7% 39% 32% 5%	561
	21st to end	Night	12% 9% 38% 34% 7%	617
June	1st to 10th	Night	4 2 32% 51% 11%	570
	11th to 20th	Night	7% 2 39% 46% 7%	570
	21st to end	Night	7% 3 26% 48% 16%	570
July	1st to 10th	Night	9% 2 16% 53% 19% 1	555
	11th to 20th	Night	5% 1 16% 53% 25%	552
	21st to end	Night	6% 1 11% 57% 25% 1	624
August	1st to 10th	Night	1 9% 58% 31% 1	567
	11th to 20th	Night	4 1 10% 53% 30% 2	564
	21st to end	Night	5% 2 10% 47% 34% 2	627
September	1st to 10th	Night	8% 1 12% 43% 33% 2	570
	11th to 20th	Night	12% 1 9% 46% 31% 1	570
	21st to end	Night	11% 1 13% 42% 30% 3	570
October	1st to 10th	Night	9% 2 15% 48% 25% 2	570
	11th to 20th	Night	13% 4 22% 40% 19% 1	570
	21st to end	Night	13% 8% 25% 31% 21% 2	811
November	1st to 10th	Night	17% 5% 20% 38% 18% 2	855
	11th to 20th	Night	13% 7% 25% 39% 15% 2	1000
	21st to end	Night	20% 9% 24% 35% 12% 1	1000
December	1st to 10th	Night	18% 7% 23% 38% 12% 1	1000
	11th to 20th	Night	22% 10% 24% 34% 10%	1000
	21st to end	Night	18% 9% 26% 38% 8% 1	1100

Page generated at 2025-02-03 02:05:53. Version ac07

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