Tuva Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tuva Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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	12% 6% 2 5% 4 3 4 4 5% 7% 48%	78836
	Night	11% 5% 2 4 4 2 3 4 5% 6% 53%	80412
Transparency	Day	35% 6% 11% 24% 20% 4	78561
	Night	32% 5% 10% 24% 23% 6%	80207
Seeing	Day	13% 8% 23% 28% 21% 6%	14360
	Night	13% 8% 28% 33% 16% 1	24407

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	12% 10% 4 5% 4 3 4 4 4 6% 46%	2847
	11th to 20th	Day	9% 5% 2 4 4 2 3 3 4 5% 58%	2850
	21st to end	Day	21% 10% 3 5% 3 1 2 2 3 4 46%	3135
February	1st to 10th	Day	17% 8% 4 5% 5% 3 3 3 4 5% 43%	1710
	11th to 20th	Day	15% 7% 3 5% 4 2 4 3 4 8% 45%	1778
	21st to end	Day	20% 7% 3 4 5% 3 5% 3 4 5% 42%	1542
March	1st to 10th	Day	17% 7% 2 4 3 2 3 3 4 6% 49%	1980
	11th to 20th	Day	17% 8% 3 5% 5% 2 4 4 5% 5% 42%	1980
	21st to end	Day	16% 11% 4 5% 4 3 4 4 4 7% 39%	2178
April	1st to 10th	Day	12% 5% 2 4 6% 3 5% 5% 5% 7% 47%	1998
	11th to 20th	Day	16% 5% 2 6% 4 3 3 4 4 6% 45%	2134
	21st to end	Day	19% 6% 2 6% 5% 3 3 4 4 6% 41%	2255
May	1st to 10th	Day	15% 7% 3 6% 5% 2 5% 5% 4 6% 43%	2340
	11th to 20th	Day	14% 6% 3 5% 6% 3 4 4 5% 8% 41%	2302
	21st to end	Day	11% 6% 3 6% 6% 4 6% 6% 7% 9% 38%	2531
June	1st to 10th	Day	8% 4 2 5% 4 4 4 4 6% 9% 48%	2340
	11th to 20th	Day	7% 4 2 4 5% 3 5% 6% 6% 10% 49%	2340
	21st to end	Day	4 3 2 3 4 4 3 5% 6% 7% 59%	2340
July	1st to 10th	Day	7% 4 2 4 5% 4 6% 6% 8% 10% 43%	2340
	11th to 20th	Day	4 3 1 3 4 3 4 5% 7% 9% 57%	2340
	21st to end	Day	6% 4 2 5% 5% 3 4 5% 7% 11% 49%	2546
August	1st to 10th	Day	4 4 2 5% 5% 3 5% 6% 6% 8% 52%	2328
	11th to 20th	Day	9% 5% 2 4 5% 2 4 5% 5% 8% 50%	2301
	21st to end	Day	5% 3 2 4 5% 3 5% 5% 6% 8% 53%	2417
September	1st to 10th	Day	10% 4 2 3 4 3 4 4 4 6% 55%	2048
	11th to 20th	Day	12% 3 2 5% 5% 4 4 5% 5% 6% 49%	1980
	21st to end	Day	8% 4 2 4 4 3 5% 5% 5% 5% 57%	1980
October	1st to 10th	Day	9% 4 2 4 4 2 3 3 5% 6% 58%	1848
	11th to 20th	Day	12% 4 2 3 3 2 3 3 4 4 61%	1800
	21st to end	Day	18% 5% 2 4 4 2 3 3 3 5% 53%	1980
November	1st to 10th	Day	12% 5% 2 4 3 1 2 3 5% 6% 58%	1858
	11th to 20th	Day	11% 4 2 3 3 2 3 3 4 5% 60%	1774
	21st to end	Day	15% 6% 2 4 3 2 3 3 4 6% 52%	1710
December	1st to 10th	Day	14% 7% 2 4 4 2 4 4 3 7% 49%	1710
	11th to 20th	Day	16% 8% 3 4 4 2 5% 4 4 5% 45%	2161
	21st to end	Day	18% 10% 3 6% 5% 3 4 4 4 6% 35%	3135
January	1st to 10th	Night	12% 8% 4 6% 5% 3 3 4 4 5% 47%	4108
	11th to 20th	Night	10% 5% 2 4 3 2 4 3 5% 6% 56%	4120
	21st to end	Night	22% 8% 2 3 3 2 2 3 3 4 46%	4532
February	1st to 10th	Night	14% 9% 3 4 4 3 2 3 4 6% 47%	2470
	11th to 20th	Night	15% 7% 3 5% 4 2 2 3 4 5% 50%	2288
	21st to end	Night	16% 8% 3 5% 4 2 2 4 4 4 48%	1712
March	1st to 10th	Night	14% 5% 3 6% 4 2 4 4 4 5% 49%	1980
	11th to 20th	Night	17% 5% 2 4 4 2 3 4 5% 6% 48%	1980
	21st to end	Night	15% 5% 2 4 5% 2 4 3 5% 7% 48%	2178
April	1st to 10th	Night	12% 4 2 4 4 3 4 3 5% 6% 53%	1960
	11th to 20th	Night	14% 4 2 4 4 2 3 3 5% 6% 52%	1775
	21st to end	Night	13% 6% 2 5% 4 3 3 3 4 7% 50%	1702
May	1st to 10th	Night	12% 4 2 5% 5% 2 5% 4 5% 8% 48%	1620
	11th to 20th	Night	11% 5% 3 5% 4 3 4 4 5% 8% 48%	1593
	21st to end	Night	8% 4 3 5% 4 4 4 6% 6% 11% 46%	1745
June	1st to 10th	Night	5% 3 2 3 4 2 4 5% 6% 9% 57%	1620
	11th to 20th	Night	5% 3 2 3 3 2 3 5% 6% 9% 59%	1620
	21st to end	Night	2 2 1 2 3 2 4 4 5% 8% 66%	1620
July	1st to 10th	Night	4 3 1 3 4 3 5% 6% 9% 10% 52%	1620
	11th to 20th	Night	2 1 1 3 3 3 4 5% 5% 9% 64%	1620
	21st to end	Night	4 2 1 3 4 3 4 5% 6% 10% 57%	1772
August	1st to 10th	Night	2 2 2 3 4 3 4 6% 7% 10% 57%	1611
	11th to 20th	Night	5% 3 2 3 4 2 4 6% 7% 9% 56%	1600
	21st to end	Night	3 3 2 3 4 2 4 5% 6% 9% 58%	1939
September	1st to 10th	Night	7% 4 1 4 4 2 4 3 4 6% 61%	1908
	11th to 20th	Night	10% 5% 2 5% 4 2 4 4 6% 7% 51%	1980
	21st to end	Night	7% 4 2 3 4 2 2 4 5% 6% 61%	1980
October	1st to 10th	Night	8% 3 1 3 4 2 4 3 4 6% 63%	2092
	11th to 20th	Night	12% 4 1 3 4 2 2 3 4 4 61%	2160
	21st to end	Night	16% 5% 2 3 3 2 3 2 2 5% 56%	2376
November	1st to 10th	Night	11% 4 2 3 3 1 3 3 3 5% 63%	2220
	11th to 20th	Night	9% 5% 2 3 4 2 3 4 4 5% 59%	2403
	21st to end	Night	15% 4 2 5% 4 1 3 3 3 5% 55%	2470
December	1st to 10th	Night	12% 6% 2 4 4 3 4 3 4 5% 53%	2470
	11th to 20th	Night	14% 6% 3 5% 4 2 3 4 4 5% 50%	3036
	21st to end	Night	16% 8% 2 6% 4 3 4 4 4 6% 44%	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	41% 4 7% 23% 22% 2	2848
	11th to 20th	Day	30% 5% 13% 28% 21% 4	2850
	21st to end	Day	45% 3 7% 20% 23% 3	3135
February	1st to 10th	Day	46% 4 10% 20% 16% 3	1710
	11th to 20th	Day	40% 5% 8% 24% 18% 4	1788
	21st to end	Day	46% 3 7% 17% 19% 7%	1542
March	1st to 10th	Day	38% 4 9% 21% 18% 11%	1980
	11th to 20th	Day	46% 5% 8% 23% 14% 6%	1980
	21st to end	Day	45% 5% 11% 23% 13% 3	2178
April	1st to 10th	Day	36% 6% 11% 23% 18% 5%	1998
	11th to 20th	Day	40% 5% 12% 22% 16% 6%	2134
	21st to end	Day	45% 4 10% 21% 18% 2	2255
May	1st to 10th	Day	42% 7% 9% 22% 18% 2	2340
	11th to 20th	Day	39% 8% 13% 25% 14% 1	2306
	21st to end	Day	40% 9% 14% 23% 13%	2531
June	1st to 10th	Day	32% 8% 16% 27% 15% 3	2340
	11th to 20th	Day	29% 8% 15% 29% 17% 3	2340
	21st to end	Day	24% 7% 12% 31% 21% 5%	2340
July	1st to 10th	Day	31% 10% 17% 26% 15% 1	2276
	11th to 20th	Day	20% 6% 15% 31% 24% 3	2271
	21st to end	Day	27% 9% 15% 33% 16% 1	2405
August	1st to 10th	Day	27% 8% 14% 28% 19% 3	2314
	11th to 20th	Day	32% 7% 13% 25% 20% 3	2301
	21st to end	Day	26% 8% 14% 29% 19% 5%	2417
September	1st to 10th	Day	30% 5% 9% 24% 24% 8%	2048
	11th to 20th	Day	34% 7% 9% 22% 21% 6%	1980
	21st to end	Day	27% 6% 10% 22% 29% 7%	1980
October	1st to 10th	Day	27% 5% 12% 22% 26% 8%	1848
	11th to 20th	Day	28% 3 7% 20% 32% 11%	1800
	21st to end	Day	36% 5% 8% 24% 18% 9%	1980
November	1st to 10th	Day	28% 3 10% 25% 26% 7%	1858
	11th to 20th	Day	28% 3 8% 28% 25% 8%	1774
	21st to end	Day	34% 4 8% 22% 26% 6%	1710
December	1st to 10th	Day	36% 5% 10% 26% 21% 2	1710
	11th to 20th	Day	41% 4 6% 21% 24% 4	2159
	21st to end	Day	49% 5% 9% 20% 14% 3	3135
January	1st to 10th	Night	40% 5% 7% 23% 22% 3	4108
	11th to 20th	Night	30% 7% 14% 20% 26% 3	4120
	21st to end	Night	43% 3 7% 20% 22% 4	4532
February	1st to 10th	Night	40% 5% 10% 23% 17% 6%	2470
	11th to 20th	Night	39% 3 6% 26% 20% 6%	2288
	21st to end	Night	40% 4 7% 19% 21% 9%	1712
March	1st to 10th	Night	38% 5% 8% 18% 20% 12%	1980
	11th to 20th	Night	37% 6% 11% 21% 18% 7%	1980
	21st to end	Night	36% 6% 10% 26% 18% 4	2178
April	1st to 10th	Night	32% 5% 10% 21% 21% 10%	1960
	11th to 20th	Night	32% 5% 10% 25% 19% 9%	1775
	21st to end	Night	36% 5% 9% 25% 23% 2	1702
May	1st to 10th	Night	34% 7% 12% 23% 21% 4	1620
	11th to 20th	Night	34% 6% 13% 27% 18% 2	1594
	21st to end	Night	32% 8% 17% 25% 15% 2	1746
June	1st to 10th	Night	21% 8% 17% 30% 21% 3	1620
	11th to 20th	Night	21% 6% 15% 31% 23% 4	1620
	21st to end	Night	18% 5% 12% 31% 26% 8%	1620
July	1st to 10th	Night	23% 9% 18% 27% 21% 3	1575
	11th to 20th	Night	15% 7% 13% 34% 25% 6%	1566
	21st to end	Night	21% 6% 15% 32% 24% 2	1673
August	1st to 10th	Night	19% 8% 16% 31% 22% 3	1601
	11th to 20th	Night	23% 7% 14% 23% 29% 5%	1600
	21st to end	Night	20% 7% 13% 30% 23% 6%	1939
September	1st to 10th	Night	25% 5% 9% 27% 23% 11%	1908
	11th to 20th	Night	31% 6% 9% 22% 24% 8%	1980
	21st to end	Night	23% 5% 8% 23% 32% 9%	1980
October	1st to 10th	Night	24% 4 12% 22% 27% 10%	2092
	11th to 20th	Night	28% 4 6% 18% 30% 14%	2160
	21st to end	Night	34% 3 6% 21% 24% 11%	2376
November	1st to 10th	Night	25% 3 8% 24% 29% 10%	2220
	11th to 20th	Night	28% 4 7% 24% 27% 10%	2403
	21st to end	Night	34% 3 7% 21% 28% 7%	2470
December	1st to 10th	Night	35% 4 10% 22% 22% 7%	2470
	11th to 20th	Night	38% 4 8% 20% 25% 6%	3037
	21st to end	Night	41% 5% 10% 22% 17% 6%	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% 13% 37% 25% 6%	270
	11th to 20th	Day	20% 19% 37% 20% 3	270
	21st to end	Day	18% 16% 37% 20% 7% 1	297
February	1st to 10th	Day	23% 17% 39% 17% 4	270
	11th to 20th	Day	24% 18% 39% 16% 2	267
	21st to end	Day	35% 16% 33% 13% 2	198
March	1st to 10th	Day	22% 20% 31% 23% 4	240
	11th to 20th	Day	23% 19% 32% 19% 7%	240
	21st to end	Day	19% 22% 40% 15% 4 1	264
April	1st to 10th	Day	12% 21% 34% 23% 8% 2	258
	11th to 20th	Day	21% 16% 33% 23% 7%	412
	21st to end	Day	20% 16% 34% 21% 8% 2	515
May	1st to 10th	Day	15% 11% 33% 31% 10%	603
	11th to 20th	Day	16% 7% 25% 34% 15% 3	625
	21st to end	Day	14% 6% 27% 28% 19% 6%	679
June	1st to 10th	Day	8% 5% 15% 31% 31% 10%	630
	11th to 20th	Day	7% 1 20% 37% 28% 7%	630
	21st to end	Day	3 2 17% 39% 32% 7%	630
July	1st to 10th	Day	8% 1 10% 30% 38% 13%	621
	11th to 20th	Day	4 1 9% 33% 42% 11%	618
	21st to end	Day	6% 1 7% 28% 43% 15%	684
August	1st to 10th	Day	5% 1 10% 36% 39% 8%	626
	11th to 20th	Day	10% 2 10% 33% 34% 10%	615
	21st to end	Day	4 1 7% 29% 43% 16%	536
September	1st to 10th	Day	7% 3 9% 25% 35% 21%	338
	11th to 20th	Day	3 1 9% 36% 37% 14%	270
	21st to end	Day	11% 3 15% 29% 31% 11%	270
October	1st to 10th	Day	6% 4 29% 31% 20% 10%	270
	11th to 20th	Day	13% 10% 32% 33% 12%	270
	21st to end	Day	26% 11% 25% 25% 11% 3	297
November	1st to 10th	Day	17% 7% 38% 27% 10% 1	270
	11th to 20th	Day	16% 9% 37% 26% 10% 1	270
	21st to end	Day	20% 16% 33% 24% 6% 1	270
December	1st to 10th	Day	17% 13% 36% 24% 8% 2	270
	11th to 20th	Day	23% 15% 36% 20% 6%	270
	21st to end	Day	21% 17% 37% 21% 5%	297
January	1st to 10th	Night	15% 14% 37% 28% 7%	950
	11th to 20th	Night	17% 16% 37% 26% 4	950
	21st to end	Night	16% 11% 35% 32% 5%	1045
February	1st to 10th	Night	20% 15% 33% 28% 4	950
	11th to 20th	Night	19% 15% 37% 27% 3	817
	21st to end	Night	21% 14% 40% 22% 3	528
March	1st to 10th	Night	17% 13% 34% 32% 5%	540
	11th to 20th	Night	21% 10% 35% 29% 4	540
	21st to end	Night	16% 11% 42% 24% 7%	594
April	1st to 10th	Night	14% 13% 40% 28% 6%	540
	11th to 20th	Night	15% 10% 38% 29% 8%	533
	21st to end	Night	16% 9% 39% 27% 9% 1	540
May	1st to 10th	Night	13% 6% 36% 37% 9%	540
	11th to 20th	Night	13% 6% 29% 35% 15% 2	531
	21st to end	Night	9% 3 28% 37% 22% 1	584
June	1st to 10th	Night	5% 3 15% 43% 31% 3	540
	11th to 20th	Night	5% 2 20% 52% 20% 1	540
	21st to end	Night	2 1 16% 49% 28% 4	540
July	1st to 10th	Night	5% 8% 41% 42% 4	525
	11th to 20th	Night	2 1 9% 39% 44% 5%	522
	21st to end	Night	5% 5% 40% 44% 5%	591
August	1st to 10th	Night	2 1 10% 43% 41% 4	537
	11th to 20th	Night	6% 1 8% 44% 38% 4	534
	21st to end	Night	4 1 8% 40% 42% 5%	594
September	1st to 10th	Night	10% 2 9% 39% 38% 2	540
	11th to 20th	Night	12% 2 12% 40% 31% 4	540
	21st to end	Night	9% 2 20% 35% 29% 5%	540
October	1st to 10th	Night	8% 2 22% 38% 27% 3	652
	11th to 20th	Night	13% 7% 31% 36% 12% 1	720
	21st to end	Night	19% 7% 28% 32% 13% 1	792
November	1st to 10th	Night	13% 6% 35% 34% 13%	740
	11th to 20th	Night	11% 14% 32% 33% 9% 1	883
	21st to end	Night	18% 11% 34% 29% 8%	950
December	1st to 10th	Night	16% 13% 34% 32% 6%	950
	11th to 20th	Night	21% 11% 35% 29% 5%	950
	21st to end	Night	17% 13% 37% 28% 5%	1045

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