UBar Camp and Retreat Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UBar Camp and Retreat Center clear sky chart from 2005-11-06 to 2024-01-22.

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	11% 5% 2 5% 5% 3 4 4 5% 7% 50%	74941
	Night	11% 5% 2 4 4 2 3 4 5% 7% 54%	75027
Transparency	Day	35% 4 10% 21% 20% 10%	74666
	Night	32% 4 11% 21% 20% 13%	74822
Seeing	Day	13% 8% 24% 31% 19% 4	13724
	Night	13% 8% 29% 35% 14% 1	23818

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	10% 6% 3 4 3 2 2 3 4 6% 56%	1707
	11th to 20th	Day	15% 7% 2 4 3 2 3 3 5% 5% 53%	1729
	21st to end	Day	11% 6% 2 4 3 3 4 3 3 5% 56%	1990
February	1st to 10th	Day	14% 6% 2 4 4 3 3 3 4 6% 51%	1800
	11th to 20th	Day	14% 6% 2 5% 4 2 4 4 5% 6% 48%	1749
	21st to end	Day	13% 6% 2 3 3 2 3 3 4 6% 54%	1480
March	1st to 10th	Day	15% 8% 3 6% 4 2 3 4 4 7% 45%	1880
	11th to 20th	Day	14% 6% 2 5% 4 2 3 4 5% 6% 50%	1980
	21st to end	Day	13% 5% 2 4 4 3 4 4 5% 5% 52%	2178
April	1st to 10th	Day	12% 7% 2 5% 4 3 4 4 5% 7% 46%	1980
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 6% 48%	2084
	21st to end	Day	12% 6% 3 6% 5% 2 3 3 4 5% 51%	2216
May	1st to 10th	Day	14% 7% 3 5% 5% 3 4 4 6% 7% 43%	2340
	11th to 20th	Day	13% 8% 3 6% 5% 3 4 5% 6% 6% 41%	2302
	21st to end	Day	15% 7% 3 5% 5% 3 5% 5% 6% 7% 39%	2531
June	1st to 10th	Day	5% 4 2 5% 5% 3 5% 5% 6% 9% 51%	2340
	11th to 20th	Day	6% 4 2 5% 5% 3 5% 5% 5% 10% 51%	2340
	21st to end	Day	7% 4 2 5% 6% 4 7% 6% 6% 10% 42%	2340
July	1st to 10th	Day	11% 5% 3 5% 6% 4 6% 6% 7% 9% 36%	2340
	11th to 20th	Day	5% 3 2 4 4 3 4 5% 7% 8% 56%	2340
	21st to end	Day	5% 2 1 3 4 3 5% 6% 7% 10% 53%	2546
August	1st to 10th	Day	1 2 1 3 4 3 4 4 5% 9% 64%	2195
	11th to 20th	Day	8% 3 2 4 6% 4 5% 5% 7% 9% 48%	2123
	21st to end	Day	6% 5% 2 4 5% 4 6% 5% 6% 10% 46%	2354
September	1st to 10th	Day	9% 6% 2 6% 6% 4 5% 4 4 7% 44%	1980
	11th to 20th	Day	10% 7% 3 6% 6% 3 6% 5% 6% 8% 40%	1980
	21st to end	Day	10% 4 2 5% 5% 3 4 5% 6% 7% 48%	1980
October	1st to 10th	Day	6% 4 2 3 6% 2 4 5% 5% 8% 54%	1980
	11th to 20th	Day	13% 5% 2 4 4 3 3 3 4 5% 54%	1935
	21st to end	Day	12% 5% 2 4 3 2 3 3 3 5% 58%	1980
November	1st to 10th	Day	13% 6% 2 4 5% 2 3 5% 5% 6% 50%	1816
	11th to 20th	Day	10% 6% 1 5% 4 2 4 4 5% 7% 52%	1710
	21st to end	Day	15% 7% 3 4 3 2 3 3 4 5% 50%	1710
December	1st to 10th	Day	13% 8% 2 4 3 2 2 3 4 6% 52%	1710
	11th to 20th	Day	13% 7% 2 5% 4 3 4 4 4 6% 49%	2161
	21st to end	Day	12% 6% 2 3 3 2 3 3 3 5% 59%	3135
January	1st to 10th	Night	13% 5% 2 3 3 2 3 3 3 6% 56%	2458
	11th to 20th	Night	13% 6% 3 4 3 2 2 3 4 6% 54%	2466
	21st to end	Night	14% 6% 2 4 4 2 3 3 4 6% 52%	2400
February	1st to 10th	Night	13% 6% 2 5% 4 2 3 3 4 5% 53%	2160
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 4 6% 51%	2098
	21st to end	Night	14% 6% 3 4 4 2 3 3 4 6% 50%	1776
March	1st to 10th	Night	13% 8% 2 5% 4 2 3 4 5% 7% 47%	2080
	11th to 20th	Night	14% 7% 3 5% 4 3 4 4 4 5% 48%	1980
	21st to end	Night	10% 6% 2 4 3 2 3 4 4 7% 54%	2178
April	1st to 10th	Night	9% 6% 3 5% 4 3 4 4 5% 6% 51%	1980
	11th to 20th	Night	14% 7% 2 5% 4 2 4 4 4 6% 49%	1822
	21st to end	Night	13% 6% 2 4 4 2 4 3 4 6% 53%	1742
May	1st to 10th	Night	12% 6% 2 4 5% 3 3 4 6% 7% 48%	1620
	11th to 20th	Night	11% 6% 2 5% 5% 2 4 4 5% 8% 46%	1593
	21st to end	Night	12% 7% 2 4 4 3 3 5% 5% 9% 46%	1745
June	1st to 10th	Night	4 3 1 3 2 1 4 4 7% 11% 61%	1620
	11th to 20th	Night	3 3 2 3 3 2 4 3 6% 9% 62%	1620
	21st to end	Night	7% 4 2 3 3 3 4 4 5% 11% 54%	1620
July	1st to 10th	Night	8% 5% 2 5% 4 3 5% 5% 6% 11% 46%	1620
	11th to 20th	Night	2 2 1 3 3 2 4 4 6% 9% 65%	1620
	21st to end	Night	3 3 1 2 3 2 4 5% 5% 10% 62%	1772
August	1st to 10th	Night	2 2 1 2 2 1 2 3 5% 9% 71%	1739
	11th to 20th	Night	5% 3 1 4 4 3 5% 5% 7% 9% 54%	1778
	21st to end	Night	5% 5% 1 4 4 3 5% 5% 7% 10% 50%	2002
September	1st to 10th	Night	8% 6% 2 5% 4 3 4 4 6% 7% 52%	1980
	11th to 20th	Night	9% 6% 2 5% 5% 3 4 4 5% 8% 47%	1980
	21st to end	Night	8% 6% 2 5% 4 3 4 4 6% 7% 53%	1980
October	1st to 10th	Night	6% 4 2 3 3 3 3 3 4 7% 61%	1980
	11th to 20th	Night	12% 4 1 4 4 2 3 3 5% 5% 56%	2006
	21st to end	Night	13% 5% 2 4 3 2 2 2 3 3 62%	2376
November	1st to 10th	Night	12% 6% 2 4 3 2 2 3 4 6% 56%	2258
	11th to 20th	Night	9% 6% 2 3 3 2 3 4 4 6% 58%	2470
	21st to end	Night	16% 7% 2 4 3 2 3 3 4 5% 50%	2470
December	1st to 10th	Night	13% 4 3 4 4 2 3 3 4 7% 55%	2470
	11th to 20th	Night	12% 8% 3 5% 4 3 4 4 3 5% 49%	3036
	21st to end	Night	15% 6% 2 4 3 1 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	31% 2 4 20% 25% 18%	1708
	11th to 20th	Day	36% 2 4 17% 24% 17%	1729
	21st to end	Day	32% 3 6% 14% 27% 19%	1990
February	1st to 10th	Day	36% 3 8% 12% 23% 18%	1800
	11th to 20th	Day	38% 3 6% 18% 19% 16%	1759
	21st to end	Day	34% 3 7% 16% 22% 18%	1480
March	1st to 10th	Day	41% 4 8% 16% 19% 13%	1880
	11th to 20th	Day	37% 4 7% 16% 18% 18%	1980
	21st to end	Day	35% 3 8% 19% 21% 14%	2178
April	1st to 10th	Day	38% 4 8% 18% 19% 13%	1980
	11th to 20th	Day	39% 3 7% 17% 21% 13%	2084
	21st to end	Day	38% 2 7% 21% 20% 12%	2216
May	1st to 10th	Day	42% 4 9% 16% 22% 8%	2340
	11th to 20th	Day	43% 4 9% 21% 19% 4	2306
	21st to end	Day	44% 4 11% 23% 16% 2	2531
June	1st to 10th	Day	30% 5% 12% 29% 21% 4	2340
	11th to 20th	Day	31% 4 12% 28% 19% 6%	2340
	21st to end	Day	37% 7% 12% 23% 17% 5%	2340
July	1st to 10th	Day	42% 7% 16% 25% 10% 1	2276
	11th to 20th	Day	24% 6% 17% 29% 21% 3	2271
	21st to end	Day	21% 6% 23% 35% 14% 1	2405
August	1st to 10th	Day	18% 5% 13% 41% 21% 2	2181
	11th to 20th	Day	32% 5% 17% 29% 13% 4	2123
	21st to end	Day	33% 6% 16% 27% 13% 4	2354
September	1st to 10th	Day	40% 5% 10% 21% 18% 7%	1980
	11th to 20th	Day	41% 6% 11% 20% 18% 5%	1980
	21st to end	Day	35% 4 10% 21% 19% 11%	1980
October	1st to 10th	Day	29% 4 10% 23% 24% 9%	1980
	11th to 20th	Day	34% 3 6% 16% 23% 17%	1935
	21st to end	Day	31% 3 4 16% 26% 20%	1980
November	1st to 10th	Day	37% 3 8% 21% 21% 11%	1816
	11th to 20th	Day	33% 3 7% 18% 22% 17%	1710
	21st to end	Day	39% 2 6% 16% 23% 15%	1710
December	1st to 10th	Day	36% 2 8% 19% 25% 10%	1710
	11th to 20th	Day	37% 4 8% 12% 23% 17%	2159
	21st to end	Day	31% 2 4 16% 28% 18%	3135
January	1st to 10th	Night	32% 2 4 16% 25% 21%	2458
	11th to 20th	Night	34% 2 5% 18% 23% 18%	2466
	21st to end	Night	35% 2 6% 14% 22% 20%	2400
February	1st to 10th	Night	35% 3 7% 12% 22% 20%	2160
	11th to 20th	Night	36% 3 5% 17% 21% 17%	2098
	21st to end	Night	37% 3 7% 13% 22% 19%	1776
March	1st to 10th	Night	39% 3 8% 17% 21% 12%	2080
	11th to 20th	Night	39% 4 7% 14% 18% 18%	1980
	21st to end	Night	32% 4 11% 19% 18% 16%	2178
April	1st to 10th	Night	35% 4 10% 19% 16% 16%	1980
	11th to 20th	Night	38% 4 8% 15% 18% 17%	1822
	21st to end	Night	37% 2 9% 20% 20% 11%	1742
May	1st to 10th	Night	36% 5% 10% 20% 18% 11%	1620
	11th to 20th	Night	38% 4 12% 24% 17% 5%	1594
	21st to end	Night	37% 5% 15% 28% 14% 2	1746
June	1st to 10th	Night	19% 5% 19% 34% 20% 3	1620
	11th to 20th	Night	21% 4 17% 30% 22% 6%	1620
	21st to end	Night	27% 5% 18% 28% 18% 4	1620
July	1st to 10th	Night	31% 8% 22% 29% 9% 1	1575
	11th to 20th	Night	17% 6% 19% 32% 23% 3	1566
	21st to end	Night	17% 6% 26% 36% 14% 1	1673
August	1st to 10th	Night	13% 4 19% 42% 20% 1	1729
	11th to 20th	Night	25% 7% 20% 29% 15% 3	1778
	21st to end	Night	28% 8% 22% 26% 14% 3	2002
September	1st to 10th	Night	31% 5% 14% 23% 19% 7%	1980
	11th to 20th	Night	35% 6% 16% 22% 16% 5%	1980
	21st to end	Night	31% 4 12% 21% 20% 11%	1980
October	1st to 10th	Night	24% 4 14% 26% 21% 11%	1980
	11th to 20th	Night	31% 3 9% 18% 22% 17%	2006
	21st to end	Night	30% 2 5% 18% 23% 22%	2376
November	1st to 10th	Night	32% 2 8% 21% 23% 14%	2258
	11th to 20th	Night	29% 3 8% 23% 20% 17%	2470
	21st to end	Night	38% 2 7% 16% 21% 16%	2470
December	1st to 10th	Night	32% 3 9% 19% 24% 13%	2470
	11th to 20th	Night	40% 2 5% 14% 19% 20%	3037
	21st to end	Night	33% 2 4 15% 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% 19% 4 1	270
	11th to 20th	Day	24% 13% 34% 22% 6%	270
	21st to end	Day	18% 15% 42% 21% 4	267
February	1st to 10th	Day	23% 13% 38% 19% 7%	240
	11th to 20th	Day	26% 15% 39% 17% 3 1	240
	21st to end	Day	21% 21% 37% 18% 3	198
March	1st to 10th	Day	21% 18% 44% 16% 2	240
	11th to 20th	Day	18% 22% 36% 18% 6%	240
	21st to end	Day	17% 19% 44% 16% 3 1	264
April	1st to 10th	Day	19% 19% 42% 18% 3	240
	11th to 20th	Day	18% 21% 38% 17% 6% 1	362
	21st to end	Day	17% 16% 44% 19% 5%	476
May	1st to 10th	Day	16% 10% 42% 27% 5%	603
	11th to 20th	Day	20% 7% 33% 29% 10% 1	625
	21st to end	Day	16% 7% 31% 34% 11%	679
June	1st to 10th	Day	5% 4 21% 45% 22% 3	630
	11th to 20th	Day	7% 3 21% 49% 17% 3	630
	21st to end	Day	7% 2 16% 42% 27% 6%	630
July	1st to 10th	Day	10% 4 8% 39% 31% 8%	621
	11th to 20th	Day	3 1 5% 44% 39% 7%	618
	21st to end	Day	4 1 5% 41% 39% 11%	684
August	1st to 10th	Day	2 4 43% 42% 10%	493
	11th to 20th	Day	9% 1 4 35% 38% 12%	437
	21st to end	Day	6% 2 5% 34% 39% 14%	473
September	1st to 10th	Day	9% 1 6% 32% 37% 16%	270
	11th to 20th	Day	8% 1 4 33% 44% 11%	270
	21st to end	Day	11% 1 5% 35% 39% 9%	270
October	1st to 10th	Day	8% 2 16% 39% 29% 6%	270
	11th to 20th	Day	13% 3 26% 38% 16% 4	270
	21st to end	Day	19% 13% 30% 26% 11% 1	297
November	1st to 10th	Day	20% 5% 33% 31% 9% 3	270
	11th to 20th	Day	21% 10% 30% 24% 10% 5%	270
	21st to end	Day	25% 20% 28% 19% 7% 2	270
December	1st to 10th	Day	16% 10% 34% 30% 8% 2	270
	11th to 20th	Day	20% 16% 37% 19% 8%	270
	21st to end	Day	18% 13% 37% 24% 8%	297
January	1st to 10th	Night	16% 11% 35% 30% 8%	950
	11th to 20th	Night	17% 11% 36% 30% 5%	946
	21st to end	Night	18% 11% 34% 31% 6%	800
February	1st to 10th	Night	19% 13% 34% 28% 6%	720
	11th to 20th	Night	18% 13% 37% 27% 4	704
	21st to end	Night	19% 14% 47% 19% 1	592
March	1st to 10th	Night	18% 13% 40% 26% 3	640
	11th to 20th	Night	17% 11% 38% 30% 4	540
	21st to end	Night	13% 13% 49% 22% 4	594
April	1st to 10th	Night	9% 14% 50% 24% 3	540
	11th to 20th	Night	15% 16% 44% 22% 3	533
	21st to end	Night	16% 11% 46% 23% 5% 1	540
May	1st to 10th	Night	13% 12% 46% 26% 4	540
	11th to 20th	Night	14% 6% 39% 33% 8%	531
	21st to end	Night	13% 6% 38% 33% 10% 1	584
June	1st to 10th	Night	4 2 27% 49% 17% 1	540
	11th to 20th	Night	5% 3 36% 46% 10%	540
	21st to end	Night	7% 3 19% 49% 20% 2	540
July	1st to 10th	Night	9% 3 11% 48% 27% 2	525
	11th to 20th	Night	3 1 11% 57% 27% 2	522
	21st to end	Night	4 1 8% 57% 27% 4	591
August	1st to 10th	Night	2 1 9% 54% 32% 3	537
	11th to 20th	Night	5% 1 8% 50% 33% 3	534
	21st to end	Night	5% 3 6% 44% 37% 5%	594
September	1st to 10th	Night	9% 3 10% 40% 34% 3	540
	11th to 20th	Night	12% 2 6% 41% 36% 2	540
	21st to end	Night	10% 1 11% 44% 31% 2	540
October	1st to 10th	Night	6% 2 15% 47% 27% 2	540
	11th to 20th	Night	13% 4 25% 40% 16% 2	566
	21st to end	Night	16% 8% 27% 29% 18% 2	792
November	1st to 10th	Night	14% 6% 26% 38% 15% 1	778
	11th to 20th	Night	12% 8% 30% 35% 13% 2	950
	21st to end	Night	20% 10% 29% 30% 11% 1	950
December	1st to 10th	Night	16% 8% 30% 36% 9% 1	950
	11th to 20th	Night	19% 10% 33% 31% 7%	950
	21st to end	Night	15% 11% 33% 34% 7%	1045

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