Cloudbait Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cloudbait Observatory clear sky chart from 2005-11-06 to 2026-08-15.

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	3 5% 2 6% 4 4 5% 4 6% 8% 53%	152475
	Night	2 5% 2 5% 3 4 4 3 5% 8% 59%	146924
Transparency	Day	26% 5% 10% 23% 24% 11%	147435
	Night	23% 4 12% 26% 26% 9%	142973
Seeing	Day	10% 18% 32% 25% 13% 3	17948
	Night	5% 12% 36% 35% 12% 1	27920

By Month

Percentage Cloud Cover SW (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	6% 3 6% 3 3 4 3 4 6% 61%	4720
	11th to 20th	Day	1 1 5% 3 3 4 3 5% 8% 67%	5118
	21st to end	Day	5% 2 5% 3 3 4 3 5% 7% 62%	5844
February	1st to 10th	Day	1 4 3 5% 3 2 3 3 6% 8% 61%	1890
	11th to 20th	Day	1 2 1 4 3 3 4 4 6% 10% 63%	2023
	21st to end	Day	4 2 7% 4 3 4 3 5% 7% 62%	1730
March	1st to 10th	Day	5% 2 5% 3 3 3 3 4 7% 64%	4636
	11th to 20th	Day	2 8% 4 9% 6% 5% 5% 4 5% 7% 45%	5110
	21st to end	Day	1 4 2 5% 4 4 4 4 7% 9% 54%	5893
April	1st to 10th	Day	2 6% 1 6% 4 5% 6% 4 6% 8% 52%	2520
	11th to 20th	Day	4 9% 3 7% 5% 4 4 3 6% 7% 48%	2491
	21st to end	Day	4 9% 2 7% 4 5% 5% 4 7% 8% 45%	2520
May	1st to 10th	Day	6% 10% 3 7% 4 4 5% 4 6% 7% 43%	7235
	11th to 20th	Day	4 6% 3 7% 5% 5% 6% 5% 7% 9% 44%	8135
	21st to end	Day	3 5% 2 6% 4 5% 5% 5% 8% 9% 47%	9026
June	1st to 10th	Day	3 5% 2 6% 5% 5% 6% 5% 8% 11% 45%	2940
	11th to 20th	Day	4 5% 2 5% 4 4 5% 4 7% 8% 53%	2940
	21st to end	Day	3 3 2 6% 5% 6% 6% 6% 7% 9% 48%	2940
July	1st to 10th	Day	3 2 2 5% 4 5% 5% 6% 7% 9% 53%	8249
	11th to 20th	Day	3 4 2 6% 5% 6% 6% 5% 8% 10% 46%	8250
	21st to end	Day	6% 5% 2 7% 6% 6% 6% 5% 8% 9% 40%	8522
August	1st to 10th	Day	5% 4 2 6% 6% 6% 8% 6% 9% 11% 38%	5895
	11th to 20th	Day	4 3 2 6% 5% 6% 6% 6% 8% 10% 45%	5415
	21st to end	Day	5% 5% 2 8% 5% 6% 7% 5% 7% 9% 40%	5984
September	1st to 10th	Day	5% 5% 2 6% 4 5% 5% 4 6% 6% 51%	2400
	11th to 20th	Day	4 4 2 6% 4 4 4 4 5% 7% 56%	2395
	21st to end	Day	5% 4 1 4 4 3 4 3 4 5% 62%	2190
October	1st to 10th	Day	3 3 1 3 3 2 3 2 4 5% 71%	3270
	11th to 20th	Day	3 5% 2 5% 4 4 4 3 6% 8% 57%	3250
	21st to end	Day	2 4 1 3 2 2 3 2 4 5% 71%	3502
November	1st to 10th	Day	1 4 1 4 3 1 2 3 4 7% 70%	1853
	11th to 20th	Day	3 2 3 2 3 2 3 5% 8% 70%	1890
	21st to end	Day	3 2 6% 4 3 3 3 4 7% 65%	1801
December	1st to 10th	Day	3 3 4 2 2 2 2 3 5% 73%	2700
	11th to 20th	Day	1 2 1 3 3 3 3 2 5% 8% 69%	3106
	21st to end	Day	3 2 5% 3 3 4 3 7% 9% 63%	4092
January	1st to 10th	Night	4 3 8% 3 3 4 3 5% 8% 60%	8201
	11th to 20th	Night	2 1 3 2 3 4 3 4 6% 71%	7913
	21st to end	Night	4 2 5% 3 4 4 3 5% 6% 66%	8370
February	1st to 10th	Night	3 2 5% 3 2 2 3 5% 7% 66%	2730
	11th to 20th	Night	1 5% 2 6% 3 4 4 3 5% 7% 61%	2484
	21st to end	Night	4 2 5% 3 3 2 3 5% 7% 66%	2076
March	1st to 10th	Night	7% 3 6% 3 3 3 3 5% 7% 60%	5454
	11th to 20th	Night	2 9% 3 6% 4 3 3 3 5% 7% 55%	5110
	21st to end	Night	1 5% 2 5% 4 4 4 3 6% 9% 58%	5297
April	1st to 10th	Night	2 6% 3 5% 2 2 3 3 5% 6% 63%	2100
	11th to 20th	Night	3 7% 3 6% 4 4 3 3 4 8% 53%	2077
	21st to end	Night	4 9% 2 6% 4 4 4 3 5% 7% 51%	2100
May	1st to 10th	Night	5% 12% 3 7% 3 5% 4 3 5% 7% 46%	5712
	11th to 20th	Night	5% 8% 2 5% 3 3 3 4 6% 9% 52%	4741
	21st to end	Night	7% 10% 3 6% 4 4 4 3 4 6% 50%	5181
June	1st to 10th	Night	3 5% 2 4 3 4 4 4 7% 9% 56%	1680
	11th to 20th	Night	3 3 1 3 3 3 4 3 6% 8% 63%	1680
	21st to end	Night	3 4 1 5% 4 4 7% 5% 7% 7% 53%	1680
July	1st to 10th	Night	3 4 1 4 3 4 5% 4 6% 9% 56%	4740
	11th to 20th	Night	2 3 1 5% 4 4 5% 5% 8% 11% 53%	4740
	21st to end	Night	3 4 2 6% 5% 6% 7% 7% 9% 11% 40%	5569
August	1st to 10th	Night	5% 5% 2 7% 4 5% 5% 4 7% 10% 46%	4123
	11th to 20th	Night	3 3 1 5% 4 5% 7% 5% 8% 10% 49%	4523
	21st to end	Night	5% 6% 2 8% 5% 6% 7% 6% 7% 10% 38%	4993
September	1st to 10th	Night	5% 4 3 6% 5% 4 5% 5% 6% 9% 49%	2000
	11th to 20th	Night	5% 4 2 4 3 3 4 3 6% 7% 58%	2005
	21st to end	Night	5% 5% 2 5% 3 3 3 3 4 6% 60%	2207
October	1st to 10th	Night	3 3 2 3 2 2 3 3 4 5% 70%	3920
	11th to 20th	Night	4 5% 2 4 3 2 3 3 5% 6% 63%	3898
	21st to end	Night	2 3 1 3 2 2 2 3 4 6% 73%	4252
November	1st to 10th	Night	1 4 1 4 3 2 2 2 5% 7% 69%	2665
	11th to 20th	Night	2 1 3 3 3 3 3 5% 6% 72%	2730
	21st to end	Night	1 5% 2 4 3 3 3 3 6% 7% 64%	2814
December	1st to 10th	Night	1 1 4 2 3 2 2 4 7% 74%	4710
	11th to 20th	Night	2 1 3 2 2 3 3 5% 8% 71%	5321
	21st to end	Night	4 2 6% 4 3 4 3 5% 8% 60%	7128

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	23% 3 8% 32% 26% 8%	4723
	11th to 20th	Day	16% 2 11% 27% 30% 14%	5118
	21st to end	Day	20% 3 9% 26% 27% 14%	5844
February	1st to 10th	Day	21% 4 11% 30% 22% 11%	1890
	11th to 20th	Day	17% 4 10% 29% 30% 10%	2033
	21st to end	Day	22% 4 7% 21% 29% 16%	1730
March	1st to 10th	Day	19% 3 6% 16% 36% 20%	4636
	11th to 20th	Day	35% 5% 8% 25% 22% 6%	5110
	21st to end	Day	24% 6% 9% 39% 19% 2	5893
April	1st to 10th	Day	26% 6% 11% 24% 23% 10%	2520
	11th to 20th	Day	33% 4 8% 24% 21% 9%	2494
	21st to end	Day	33% 6% 9% 25% 22% 5%	2520
May	1st to 10th	Day	36% 6% 9% 25% 18% 7%	7235
	11th to 20th	Day	32% 7% 11% 20% 22% 8%	8139
	21st to end	Day	28% 8% 12% 21% 21% 10%	9027
June	1st to 10th	Day	29% 7% 15% 20% 21% 8%	2940
	11th to 20th	Day	26% 5% 8% 18% 25% 18%	2940
	21st to end	Day	28% 7% 10% 21% 21% 13%	2940
July	1st to 10th	Day	22% 5% 10% 13% 22% 28%	8181
	11th to 20th	Day	29% 7% 13% 22% 19% 11%	8175
	21st to end	Day	37% 8% 19% 15% 13% 9%	8334
August	1st to 10th	Day	38% 9% 17% 19% 13% 4	4324
	11th to 20th	Day	33% 8% 14% 15% 19% 11%	3931
	21st to end	Day	34% 7% 13% 17% 22% 6%	4311
September	1st to 10th	Day	31% 5% 9% 19% 25% 12%	2400
	11th to 20th	Day	26% 4 9% 19% 29% 12%	2395
	21st to end	Day	24% 4 6% 24% 33% 10%	2190
October	1st to 10th	Day	16% 3 7% 16% 37% 20%	3270
	11th to 20th	Day	24% 4 7% 31% 25% 9%	3250
	21st to end	Day	16% 2 5% 24% 43% 10%	3502
November	1st to 10th	Day	15% 3 9% 23% 36% 13%	1853
	11th to 20th	Day	14% 3 6% 36% 31% 10%	1890
	21st to end	Day	19% 3 8% 29% 29% 12%	1801
December	1st to 10th	Day	15% 3 9% 33% 29% 10%	2700
	11th to 20th	Day	14% 3 10% 34% 31% 8%	3104
	21st to end	Day	17% 4 8% 29% 30% 11%	4092
January	1st to 10th	Night	24% 3 7% 32% 29% 5%	8202
	11th to 20th	Night	14% 3 12% 26% 28% 17%	7913
	21st to end	Night	19% 2 12% 22% 30% 14%	8370
February	1st to 10th	Night	18% 3 11% 32% 25% 10%	2730
	11th to 20th	Night	22% 5% 10% 29% 27% 8%	2484
	21st to end	Night	18% 4 6% 26% 32% 13%	2076
March	1st to 10th	Night	24% 4 6% 16% 37% 13%	5454
	11th to 20th	Night	27% 3 9% 23% 29% 9%	5110
	21st to end	Night	22% 4 14% 39% 19% 2	5297
April	1st to 10th	Night	22% 5% 11% 29% 26% 7%	2100
	11th to 20th	Night	29% 3 10% 28% 23% 6%	2077
	21st to end	Night	30% 5% 15% 28% 19% 4	2100
May	1st to 10th	Night	35% 6% 12% 27% 13% 6%	5710
	11th to 20th	Night	27% 4 13% 27% 21% 7%	4742
	21st to end	Night	34% 6% 13% 18% 22% 8%	5182
June	1st to 10th	Night	23% 5% 20% 25% 15% 11%	1680
	11th to 20th	Night	19% 5% 11% 23% 24% 18%	1680
	21st to end	Night	25% 6% 12% 23% 20% 13%	1680
July	1st to 10th	Night	23% 5% 10% 18% 28% 17%	4700
	11th to 20th	Night	21% 6% 19% 29% 19% 6%	4692
	21st to end	Night	33% 10% 23% 17% 10% 8%	5445
August	1st to 10th	Night	39% 8% 21% 17% 11% 4	3018
	11th to 20th	Night	27% 9% 23% 18% 18% 6%	3283
	21st to end	Night	31% 9% 18% 21% 19% 2	3597
September	1st to 10th	Night	29% 7% 11% 24% 21% 8%	2000
	11th to 20th	Night	23% 4 12% 24% 24% 13%	2005
	21st to end	Night	24% 4 9% 26% 30% 8%	2207
October	1st to 10th	Night	17% 4 8% 24% 33% 14%	3920
	11th to 20th	Night	21% 5% 9% 30% 27% 8%	3898
	21st to end	Night	14% 3 6% 27% 39% 12%	4252
November	1st to 10th	Night	15% 4 10% 28% 31% 12%	2665
	11th to 20th	Night	13% 4 7% 34% 31% 11%	2730
	21st to end	Night	19% 3 9% 28% 30% 11%	2814
December	1st to 10th	Night	13% 3 9% 33% 34% 8%	4710
	11th to 20th	Night	12% 3 10% 31% 37% 7%	5322
	21st to end	Night	22% 3 11% 23% 32% 8%	7128

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	11% 24% 32% 26% 7% 1	330
	11th to 20th	Day	14% 21% 40% 23% 2 1	330
	21st to end	Day	7% 21% 42% 22% 6% 1	363
February	1st to 10th	Day	10% 36% 36% 15% 3 1	330
	11th to 20th	Day	8% 34% 40% 15% 3	330
	21st to end	Day	12% 30% 41% 14% 3	273
March	1st to 10th	Day	8% 28% 38% 20% 6%	340
	11th to 20th	Day	14% 28% 35% 18% 5%	540
	21st to end	Day	13% 32% 36% 16% 3	594
April	1st to 10th	Day	14% 29% 36% 16% 5% 1	540
	11th to 20th	Day	22% 30% 31% 13% 4 1	532
	21st to end	Day	17% 28% 34% 16% 4 1	540
May	1st to 10th	Day	15% 24% 35% 19% 6% 1	606
	11th to 20th	Day	11% 17% 30% 29% 10% 2	775
	21st to end	Day	9% 17% 30% 28% 14% 2	844
June	1st to 10th	Day	5% 14% 29% 29% 19% 3	780
	11th to 20th	Day	8% 14% 31% 29% 14% 3	780
	21st to end	Day	4 14% 34% 26% 18% 4	780
July	1st to 10th	Day	6% 7% 22% 35% 26% 4	771
	11th to 20th	Day	7% 3 20% 35% 28% 7%	768
	21st to end	Day	10% 6% 19% 35% 24% 6%	697
August	1st to 10th	Day	9% 9% 26% 33% 18% 5%	567
	11th to 20th	Day	8% 8% 26% 34% 19% 6%	534
	21st to end	Day	8% 8% 30% 33% 18% 3	583
September	1st to 10th	Day	8% 8% 31% 29% 22% 3	530
	11th to 20th	Day	6% 12% 34% 32% 13% 3	525
	21st to end	Day	7% 13% 22% 31% 23% 5%	330
October	1st to 10th	Day	6% 15% 28% 26% 20% 4	330
	11th to 20th	Day	8% 20% 30% 24% 15% 2	330
	21st to end	Day	11% 18% 38% 24% 9% 1	363
November	1st to 10th	Day	11% 18% 38% 21% 11% 2	330
	11th to 20th	Day	7% 21% 36% 26% 7% 2	330
	21st to end	Day	5% 20% 46% 22% 7%	330
December	1st to 10th	Day	10% 22% 38% 22% 7% 1	330
	11th to 20th	Day	8% 23% 43% 22% 5%	330
	21st to end	Day	12% 23% 43% 18% 4 1	363
January	1st to 10th	Night	3 18% 43% 28% 8% 1	1050
	11th to 20th	Night	3 22% 44% 24% 6% 1	934
	21st to end	Night	2 15% 45% 33% 5% 1	924
February	1st to 10th	Night	2 16% 54% 24% 3	840
	11th to 20th	Night	3 18% 50% 27% 2	824
	21st to end	Night	3 18% 51% 26% 2	692
March	1st to 10th	Night	4 15% 47% 29% 4	840
	11th to 20th	Night	6% 14% 41% 32% 7%	840
	21st to end	Night	5% 16% 47% 29% 4	792
April	1st to 10th	Night	6% 18% 43% 30% 3	630
	11th to 20th	Night	9% 16% 39% 30% 6%	623
	21st to end	Night	10% 14% 39% 30% 7%	630
May	1st to 10th	Night	12% 12% 32% 35% 8%	630
	11th to 20th	Night	11% 9% 31% 36% 12% 2	621
	21st to end	Night	10% 9% 31% 36% 14% 1	683
June	1st to 10th	Night	6% 6% 27% 42% 17% 2	630
	11th to 20th	Night	5% 4 29% 47% 13% 1	630
	21st to end	Night	5% 5% 23% 42% 24% 1	630
July	1st to 10th	Night	6% 3 17% 41% 29% 3	615
	11th to 20th	Night	5% 2 13% 44% 33% 4	612
	21st to end	Night	6% 2 10% 40% 38% 3	690
August	1st to 10th	Night	7% 4 17% 40% 30% 3	627
	11th to 20th	Night	6% 3 15% 46% 28% 3	606
	21st to end	Night	7% 2 14% 47% 28% 2	660
September	1st to 10th	Night	6% 4 17% 47% 22% 5%	600
	11th to 20th	Night	8% 2 23% 47% 18% 2	600
	21st to end	Night	7% 5% 27% 43% 17% 1	607
October	1st to 10th	Night	5% 7% 34% 40% 12% 2	800
	11th to 20th	Night	4 7% 39% 38% 11% 1	800
	21st to end	Night	5% 9% 38% 35% 11% 1	880
November	1st to 10th	Night	4 11% 40% 35% 9% 1	1025
	11th to 20th	Night	3 16% 42% 31% 6% 1	1050
	21st to end	Night	4 14% 40% 35% 7%	1050
December	1st to 10th	Night	3 16% 42% 33% 5%	1050
	11th to 20th	Night	4 18% 44% 29% 5%	1050
	21st to end	Night	3 21% 46% 26% 4	1155

Page generated at 2026-08-12 01:37:18. Version ac07

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