Turner Research Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Turner Research Station clear sky chart from 2005-11-06 to 2024-09-14.

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	10% 5% 2 5% 4 4 4 3 5% 7% 52%	100524
	Night	10% 5% 2 4 3 3 3 3 5% 7% 56%	97479
Transparency	Day	32% 5% 10% 23% 22% 8%	100338
	Night	29% 4 10% 23% 22% 11%	97336
Seeing	Day	12% 7% 23% 30% 21% 6%	14867
	Night	12% 7% 29% 35% 15% 2	24708

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	11% 7% 3 4 3 2 2 2 4 4 57%	2847
	11th to 20th	Day	13% 5% 1 3 2 2 3 3 4 5% 59%	2850
	21st to end	Day	19% 8% 3 5% 3 2 3 3 3 4 48%	3181
February	1st to 10th	Day	16% 7% 2 5% 3 3 3 3 3 5% 49%	1900
	11th to 20th	Day	14% 8% 3 6% 3 3 3 2 4 5% 48%	1849
	21st to end	Day	18% 6% 1 4 3 2 3 2 4 5% 52%	1570
March	1st to 10th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 47%	3422
	11th to 20th	Day	18% 7% 2 6% 4 5% 5% 3 5% 6% 39%	3480
	21st to end	Day	10% 6% 2 6% 5% 4 4 4 6% 7% 45%	3814
April	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 47%	2090
	11th to 20th	Day	13% 5% 3 6% 4 4 4 4 4 6% 46%	2090
	21st to end	Day	13% 5% 2 5% 4 4 4 3 5% 5% 50%	2465
May	1st to 10th	Day	17% 7% 2 7% 4 4 4 4 6% 7% 37%	4082
	11th to 20th	Day	14% 7% 2 5% 4 4 4 3 5% 6% 47%	4082
	21st to end	Day	12% 6% 2 7% 5% 5% 6% 4 8% 8% 37%	4477
June	1st to 10th	Day	5% 4 1 4 4 4 5% 4 7% 8% 54%	2470
	11th to 20th	Day	5% 4 2 4 4 4 5% 4 7% 9% 54%	2470
	21st to end	Day	5% 4 1 4 4 5% 5% 4 6% 8% 54%	2470
July	1st to 10th	Day	5% 4 2 5% 4 5% 5% 4 5% 8% 53%	4120
	11th to 20th	Day	4 3 1 3 3 3 4 4 5% 9% 62%	4120
	21st to end	Day	6% 6% 2 6% 4 5% 5% 5% 8% 11% 43%	4465
August	1st to 10th	Day	1 1 1 2 2 3 3 2 5% 7% 73%	4104
	11th to 20th	Day	4 2 1 3 2 3 3 3 5% 8% 66%	3925
	21st to end	Day	3 2 1 4 4 4 5% 4 7% 10% 56%	3998
September	1st to 10th	Day	10% 5% 2 5% 5% 5% 3 3 5% 7% 50%	2090
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 7% 48%	2013
	21st to end	Day	7% 4 1 5% 3 3 4 3 4 7% 58%	1980
October	1st to 10th	Day	5% 2 1 5% 4 3 4 3 5% 6% 60%	1980
	11th to 20th	Day	10% 4 2 4 2 3 3 2 3 5% 60%	1813
	21st to end	Day	13% 4 1 3 3 3 2 2 3 3 62%	1980
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 5% 55%	1858
	11th to 20th	Day	7% 5% 1 4 3 3 3 4 5% 8% 57%	1753
	21st to end	Day	14% 7% 2 5% 4 3 3 2 3 5% 51%	1710
December	1st to 10th	Day	13% 6% 2 4 4 3 4 2 6% 4 52%	1710
	11th to 20th	Day	13% 7% 2 7% 3 3 4 4 4 6% 46%	2161
	21st to end	Day	15% 6% 2 4 3 3 3 2 4 5% 53%	3135
January	1st to 10th	Night	14% 5% 2 3 2 2 2 2 3 5% 60%	4108
	11th to 20th	Night	12% 4 1 3 3 2 2 2 3 3 65%	4120
	21st to end	Night	18% 7% 3 6% 3 3 3 3 4 5% 47%	4500
February	1st to 10th	Night	14% 7% 3 5% 3 3 3 3 3 5% 51%	2280
	11th to 20th	Night	16% 6% 2 5% 3 3 3 2 3 6% 51%	2218
	21st to end	Night	16% 6% 2 4 3 2 2 2 4 6% 52%	1884
March	1st to 10th	Night	13% 7% 3 6% 4 4 4 3 4 6% 45%	3433
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 6% 8% 42%	3480
	21st to end	Night	10% 6% 2 6% 4 4 4 4 5% 6% 48%	3817
April	1st to 10th	Night	8% 5% 2 4 3 3 3 4 6% 8% 54%	2090
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 7% 50%	2039
	21st to end	Night	10% 6% 2 4 5% 2 3 4 6% 6% 51%	1710
May	1st to 10th	Night	20% 8% 2 5% 3 2 3 2 4 8% 42%	2823
	11th to 20th	Night	10% 7% 3 6% 4 3 3 3 6% 7% 48%	2823
	21st to end	Night	11% 4 2 5% 4 4 4 4 6% 9% 46%	3090
June	1st to 10th	Night	3 2 1 4 4 3 3 3 6% 9% 61%	1710
	11th to 20th	Night	3 3 2 3 3 3 3 4 7% 8% 64%	1710
	21st to end	Night	3 4 2 3 3 3 3 5% 6% 9% 60%	1710
July	1st to 10th	Night	4 2 1 4 3 3 4 3 6% 9% 62%	2850
	11th to 20th	Night	2 2 1 3 2 3 3 2 5% 9% 68%	2850
	21st to end	Night	5% 4 2 5% 4 4 5% 4 6% 10% 51%	3098
August	1st to 10th	Night	1 1 1 1 1 2 2 4 7% 80%	2836
	11th to 20th	Night	3 2 1 3 2 2 3 3 5% 11% 65%	2909
	21st to end	Night	3 2 1 3 3 3 4 3 6% 10% 61%	3663
September	1st to 10th	Night	8% 3 1 4 3 4 4 4 5% 8% 55%	2090
	11th to 20th	Night	10% 5% 2 5% 3 3 3 4 6% 7% 52%	2024
	21st to end	Night	7% 3 1 3 2 3 4 3 5% 8% 61%	1980
October	1st to 10th	Night	6% 3 1 3 3 2 3 3 5% 6% 66%	1980
	11th to 20th	Night	11% 3 1 3 3 3 2 2 4 5% 63%	2128
	21st to end	Night	13% 4 1 4 2 2 3 2 3 4 61%	2376
November	1st to 10th	Night	10% 4 1 3 3 3 3 3 4 4 62%	2220
	11th to 20th	Night	6% 5% 2 4 4 3 4 3 5% 6% 58%	2422
	21st to end	Night	15% 5% 2 5% 3 3 3 2 4 6% 52%	2470
December	1st to 10th	Night	11% 4 2 4 3 3 3 4 5% 6% 55%	2470
	11th to 20th	Night	12% 7% 2 6% 4 3 3 2 5% 5% 50%	3036
	21st to end	Night	15% 7% 2 4 2 3 2 2 3 4 56%	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	32% 3 6% 16% 31% 12%	2848
	11th to 20th	Day	28% 3 7% 20% 30% 13%	2850
	21st to end	Day	41% 3 5% 13% 26% 12%	3181
February	1st to 10th	Day	39% 4 6% 15% 22% 15%	1900
	11th to 20th	Day	39% 3 7% 17% 22% 12%	1859
	21st to end	Day	37% 3 6% 14% 24% 18%	1570
March	1st to 10th	Day	39% 5% 7% 13% 24% 13%	3422
	11th to 20th	Day	45% 7% 12% 13% 17% 7%	3480
	21st to end	Day	36% 6% 11% 19% 20% 8%	3814
April	1st to 10th	Day	38% 5% 8% 18% 17% 13%	2090
	11th to 20th	Day	39% 6% 8% 17% 20% 11%	2090
	21st to end	Day	36% 4 7% 19% 25% 8%	2465
May	1st to 10th	Day	45% 6% 10% 19% 15% 5%	4120
	11th to 20th	Day	39% 5% 7% 19% 27% 3	4086
	21st to end	Day	41% 9% 12% 21% 11% 5%	4489
June	1st to 10th	Day	26% 7% 14% 27% 21% 4	2470
	11th to 20th	Day	26% 6% 12% 30% 18% 7%	2470
	21st to end	Day	27% 7% 13% 25% 23% 5%	2470
July	1st to 10th	Day	28% 6% 18% 36% 11% 1	4056
	11th to 20th	Day	19% 4 14% 38% 21% 5%	4051
	21st to end	Day	32% 5% 14% 33% 15%	4325
August	1st to 10th	Day	12% 3 10% 34% 38% 3	4090
	11th to 20th	Day	18% 4 15% 40% 20% 2	3964
	21st to end	Day	23% 6% 19% 30% 19% 2	3997
September	1st to 10th	Day	34% 6% 9% 20% 20% 11%	2090
	11th to 20th	Day	34% 7% 12% 20% 19% 8%	2013
	21st to end	Day	25% 6% 10% 22% 24% 12%	1980
October	1st to 10th	Day	24% 5% 10% 23% 22% 15%	1980
	11th to 20th	Day	28% 4 6% 15% 27% 19%	1813
	21st to end	Day	29% 3 6% 17% 26% 20%	1980
November	1st to 10th	Day	34% 3 7% 20% 24% 11%	1858
	11th to 20th	Day	26% 5% 9% 20% 26% 14%	1753
	21st to end	Day	37% 4 4 18% 23% 14%	1710
December	1st to 10th	Day	34% 4 8% 21% 22% 10%	1710
	11th to 20th	Day	39% 4 7% 13% 25% 12%	2159
	21st to end	Day	35% 2 6% 16% 28% 14%	3135
January	1st to 10th	Night	29% 3 4 17% 31% 16%	4108
	11th to 20th	Night	27% 2 5% 17% 29% 20%	4120
	21st to end	Night	41% 3 5% 15% 24% 13%	4500
February	1st to 10th	Night	37% 4 6% 13% 22% 17%	2280
	11th to 20th	Night	37% 2 6% 16% 24% 14%	2218
	21st to end	Night	35% 3 6% 15% 20% 20%	1884
March	1st to 10th	Night	39% 4 9% 12% 23% 13%	3433
	11th to 20th	Night	40% 5% 11% 18% 17% 8%	3480
	21st to end	Night	36% 6% 10% 18% 23% 8%	3817
April	1st to 10th	Night	29% 5% 10% 21% 18% 16%	2090
	11th to 20th	Night	36% 5% 9% 16% 19% 15%	2039
	21st to end	Night	32% 6% 11% 18% 25% 8%	1710
May	1st to 10th	Night	42% 6% 10% 21% 14% 8%	2850
	11th to 20th	Night	33% 7% 12% 21% 22% 5%	2824
	21st to end	Night	34% 7% 14% 28% 12% 5%	3099
June	1st to 10th	Night	20% 7% 15% 33% 21% 5%	1710
	11th to 20th	Night	18% 6% 14% 33% 22% 7%	1710
	21st to end	Night	21% 8% 12% 28% 25% 6%	1710
July	1st to 10th	Night	20% 5% 18% 45% 11% 1	2805
	11th to 20th	Night	14% 3 15% 44% 21% 3	2796
	21st to end	Night	28% 5% 18% 37% 13% 1	2999
August	1st to 10th	Night	6% 3 11% 36% 39% 5%	2826
	11th to 20th	Night	16% 3 19% 39% 19% 3	2936
	21st to end	Night	19% 7% 21% 32% 18% 3	3663
September	1st to 10th	Night	27% 6% 12% 23% 20% 12%	2090
	11th to 20th	Night	31% 5% 14% 20% 20% 9%	2024
	21st to end	Night	22% 5% 9% 25% 21% 16%	1980
October	1st to 10th	Night	20% 4 11% 27% 19% 19%	1980
	11th to 20th	Night	27% 3 9% 16% 23% 23%	2128
	21st to end	Night	29% 3 5% 16% 24% 23%	2376
November	1st to 10th	Night	28% 4 8% 20% 26% 15%	2220
	11th to 20th	Night	28% 4 7% 20% 24% 17%	2422
	21st to end	Night	36% 3 7% 15% 25% 14%	2470
December	1st to 10th	Night	30% 4 9% 21% 23% 12%	2470
	11th to 20th	Night	37% 3 6% 12% 25% 16%	3037
	21st to end	Night	34% 2 5% 15% 26% 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	16% 16% 39% 22% 6% 1	270
	11th to 20th	Day	22% 12% 39% 18% 7% 2	270
	21st to end	Day	21% 12% 38% 22% 7%	297
February	1st to 10th	Day	25% 17% 34% 21% 3	270
	11th to 20th	Day	21% 17% 44% 15% 3	270
	21st to end	Day	29% 18% 36% 15% 2	225
March	1st to 10th	Day	23% 16% 39% 19% 4	270
	11th to 20th	Day	22% 18% 37% 18% 3 1	270
	21st to end	Day	15% 15% 45% 19% 5%	297
April	1st to 10th	Day	21% 18% 37% 20% 3	270
	11th to 20th	Day	19% 15% 33% 28% 5%	288
	21st to end	Day	17% 13% 40% 22% 7% 1	645
May	1st to 10th	Day	16% 11% 37% 28% 7% 1	653
	11th to 20th	Day	17% 5% 32% 31% 13% 2	675
	21st to end	Day	13% 6% 31% 32% 15% 4	734
June	1st to 10th	Day	6% 1 19% 42% 25% 7%	680
	11th to 20th	Day	6% 1 21% 45% 22% 5%	680
	21st to end	Day	5% 2 12% 41% 31% 10%	680
July	1st to 10th	Day	7% 1 7% 36% 37% 11%	671
	11th to 20th	Day	2 1 5% 37% 43% 12%	668
	21st to end	Day	4 2 5% 37% 37% 15%	739
August	1st to 10th	Day	2 5% 35% 43% 14%	676
	11th to 20th	Day	7% 1 3 38% 39% 12%	601
	21st to end	Day	6% 2 3 31% 37% 22%	435
September	1st to 10th	Day	9% 2 5% 26% 38% 19%	300
	11th to 20th	Day	6% 1 6% 23% 47% 17%	279
	21st to end	Day	12% 1 6% 33% 33% 14%	270
October	1st to 10th	Day	3 1 18% 39% 32% 6%	270
	11th to 20th	Day	11% 4 28% 32% 21% 4	270
	21st to end	Day	24% 8% 25% 24% 16% 2	297
November	1st to 10th	Day	19% 4 34% 27% 13% 3	270
	11th to 20th	Day	14% 11% 29% 29% 16% 2	270
	21st to end	Day	21% 13% 33% 23% 8% 1	270
December	1st to 10th	Day	17% 6% 39% 26% 9% 3	270
	11th to 20th	Day	18% 12% 39% 23% 8% 1	270
	21st to end	Day	22% 9% 38% 22% 9% 1	297
January	1st to 10th	Night	15% 9% 38% 30% 7%	950
	11th to 20th	Night	17% 13% 33% 29% 7%	950
	21st to end	Night	16% 12% 35% 31% 6%	1026
February	1st to 10th	Night	18% 15% 36% 26% 5%	760
	11th to 20th	Night	18% 14% 41% 24% 3	744
	21st to end	Night	22% 14% 44% 17% 3	628
March	1st to 10th	Night	18% 12% 39% 27% 4	584
	11th to 20th	Night	17% 10% 40% 27% 6%	570
	21st to end	Night	11% 14% 45% 26% 3	627
April	1st to 10th	Night	10% 12% 47% 27% 4	570
	11th to 20th	Night	14% 12% 43% 26% 5%	563
	21st to end	Night	13% 9% 46% 24% 8% 1	570
May	1st to 10th	Night	13% 8% 45% 28% 5% 1	570
	11th to 20th	Night	13% 4 39% 29% 13% 2	561
	21st to end	Night	10% 4 34% 37% 13% 1	617
June	1st to 10th	Night	4 2 22% 49% 21% 4	570
	11th to 20th	Night	4 2 29% 49% 15% 1	570
	21st to end	Night	3 2 17% 49% 26% 4	570
July	1st to 10th	Night	6% 1 12% 48% 28% 5%	555
	11th to 20th	Night	3 1 10% 55% 27% 4	552
	21st to end	Night	3 1 8% 51% 34% 3	624
August	1st to 10th	Night	2 5% 53% 36% 4	567
	11th to 20th	Night	7% 1 6% 47% 34% 6%	564
	21st to end	Night	5% 5% 44% 39% 7%	627
September	1st to 10th	Night	10% 1 8% 43% 33% 5%	570
	11th to 20th	Night	12% 1 7% 42% 33% 5%	552
	21st to end	Night	9% 14% 38% 34% 5%	540
October	1st to 10th	Night	7% 1 17% 45% 25% 4	540
	11th to 20th	Night	12% 4 27% 38% 17% 2	688
	21st to end	Night	16% 7% 30% 31% 15% 1	792
November	1st to 10th	Night	12% 4 29% 38% 15% 1	740
	11th to 20th	Night	9% 8% 29% 38% 15% 1	902
	21st to end	Night	17% 9% 34% 28% 11% 1	950
December	1st to 10th	Night	14% 9% 33% 35% 9%	950
	11th to 20th	Night	20% 8% 33% 33% 6%	950
	21st to end	Night	18% 8% 37% 30% 7%	1045

Page generated at 2024-09-11 09:00:01. Version ac07

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