Canebrake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canebrake clear sky chart from 2005-11-06 to 2025-03-27.

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	2 2 1 3 2 2 3 3 4 6% 73%	113066
	Night	2 2 1 3 2 2 3 3 4 6% 72%	115096
Transparency	Day	12% 3 6% 15% 27% 37%	112818
	Night	12% 3 7% 18% 29% 32%	114933
Seeing	Day	9% 16% 33% 29% 10% 2	15829
	Night	5% 10% 28% 33% 19% 5%	25633

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	2 1 1 4 3 3 2 3 4 7% 70%	3639
	11th to 20th	Day	2 2 1 4 2 3 3 2 5% 7% 68%	3801
	21st to end	Day	4 5% 2 5% 3 3 4 3 6% 9% 55%	4766
February	1st to 10th	Day	4 4 1 4 3 4 4 3 5% 9% 60%	2000
	11th to 20th	Day	3 2 1 4 3 3 4 4 7% 9% 61%	1950
	21st to end	Day	4 4 2 5% 3 3 3 4 6% 6% 61%	1650
March	1st to 10th	Day	2 5% 2 5% 4 4 5% 4 8% 9% 52%	3238
	11th to 20th	Day	4 5% 2 4 4 3 4 4 7% 9% 55%	3378
	21st to end	Day	2 4 1 3 4 4 4 5% 7% 9% 57%	4239
April	1st to 10th	Day	3 3 1 3 3 3 3 3 5% 8% 65%	2280
	11th to 20th	Day	2 2 1 2 3 2 3 3 4 6% 73%	2249
	21st to end	Day	1 1 1 2 2 2 3 3 5% 7% 73%	2280
May	1st to 10th	Day	1 1 1 2 2 2 2 2 4 5% 78%	4007
	11th to 20th	Day	1 2 1 2 1 2 3 3 5% 8% 74%	4071
	21st to end	Day	1 1 1 2 1 2 2 2 3 4 82%	4477
June	1st to 10th	Day	1 2 1 2 1 3 3 2 5% 6% 75%	2627
	11th to 20th	Day	1 2 2 2 2 2 3 4 82%	2660
	21st to end	Day	1 1 1 1 2 1 1 1 3 3 85%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 3 88%	4420
	11th to 20th	Day	1 2 1 2 2 3 2 2 4 5% 77%	4420
	21st to end	Day	1 1 1 2 2 2 2 2 3 5% 79%	4443
August	1st to 10th	Day	2 1 1 1 2 2 2 2 3 3 82%	3783
	11th to 20th	Day	1 1 1 1 1 1 2 2 89%	3724
	21st to end	Day	1 1 1 1 1 1 1 2 2 90%	4180
September	1st to 10th	Day	1 2 1 2 2 2 2 2 4 3 79%	2280
	11th to 20th	Day	1 1 1 1 2 2 2 3 88%	2147
	21st to end	Day	1 1 1 1 1 1 1 1 2 3 86%	2090
October	1st to 10th	Day	1 1 1 1 1 2 2 3 6% 81%	3490
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 3 82%	3224
	21st to end	Day	1 2 2 3 2 2 3 3 3 6% 73%	3303
November	1st to 10th	Day	2 2 1 2 2 2 3 2 4 7% 74%	1764
	11th to 20th	Day	2 2 1 3 2 2 2 4 4 7% 72%	1800
	21st to end	Day	2 3 1 4 2 3 3 3 6% 7% 64%	1800
December	1st to 10th	Day	2 2 1 4 3 3 4 4 6% 6% 66%	2950
	11th to 20th	Day	4 4 2 4 3 3 4 4 7% 8% 57%	3272
	21st to end	Day	5% 6% 2 4 3 3 5% 5% 7% 9% 51%	4004
January	1st to 10th	Night	2 4 1 2 2 2 3 3 4 7% 69%	6306
	11th to 20th	Night	1 3 1 3 3 3 3 3 5% 8% 67%	6161
	21st to end	Night	3 5% 2 5% 4 3 4 3 5% 8% 58%	6207
February	1st to 10th	Night	4 5% 2 4 4 3 4 4 4 8% 60%	2400
	11th to 20th	Night	3 2 1 4 3 3 3 3 6% 9% 63%	2338
	21st to end	Night	4 3 1 3 3 3 3 3 5% 7% 64%	1980
March	1st to 10th	Night	1 6% 2 4 4 3 4 4 6% 11% 55%	3856
	11th to 20th	Night	3 3 1 4 3 3 5% 4 6% 9% 59%	3817
	21st to end	Night	2 4 1 4 3 3 4 4 5% 8% 63%	3552
April	1st to 10th	Night	2 3 1 3 3 3 3 4 5% 7% 66%	1900
	11th to 20th	Night	2 1 3 2 2 3 3 4 6% 73%	1879
	21st to end	Night	1 1 1 2 2 1 2 2 4 7% 77%	1900
May	1st to 10th	Night	1 1 1 1 2 2 4 6% 81%	2966
	11th to 20th	Night	1 1 1 1 1 2 3 6% 83%	2834
	21st to end	Night	1 1 1 1 1 3 3 88%	3110
June	1st to 10th	Night	1 1 1 2 2 2 2 4 6% 77%	1548
	11th to 20th	Night	1 2 1 1 1 1 2 4 86%	1520
	21st to end	Night	1 1 1 1 1 1 3 4 87%	1520
July	1st to 10th	Night	1 1 1 1 1 2 3 90%	2540
	11th to 20th	Night	1 1 1 2 1 1 2 2 3 4 83%	2540
	21st to end	Night	1 1 1 1 1 1 1 3 3 85%	3097
August	1st to 10th	Night	1 1 1 1 1 1 2 2 3 5% 83%	3166
	11th to 20th	Night	1 1 1 1 1 2 2 91%	3126
	21st to end	Night	1 1 1 1 1 1 2 92%	3498
September	1st to 10th	Night	1 2 1 1 1 1 1 2 3 3 85%	1900
	11th to 20th	Night	1 1 2 1 2 2 3 86%	2033
	21st to end	Night	1 1 1 1 1 3 4 87%	2090
October	1st to 10th	Night	1 1 1 1 1 1 1 2 4 87%	3490
	11th to 20th	Night	1 1 1 1 2 2 2 3 5% 84%	3710
	21st to end	Night	2 2 1 2 2 2 2 2 2 5% 78%	4259
November	1st to 10th	Night	1 2 1 2 1 2 2 2 4 7% 75%	2535
	11th to 20th	Night	1 2 1 2 3 3 3 4 4 6% 71%	2600
	21st to end	Night	2 3 2 3 3 3 3 3 5% 9% 65%	2600
December	1st to 10th	Night	2 2 1 3 3 3 3 3 5% 8% 66%	4240
	11th to 20th	Night	3 4 1 4 4 4 5% 4 7% 11% 55%	4926
	21st to end	Night	4 5% 2 5% 4 5% 6% 5% 7% 11% 48%	6952

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	12% 4 9% 32% 30% 14%	3639
	11th to 20th	Day	13% 4 13% 18% 24% 28%	3801
	21st to end	Day	23% 5% 9% 20% 23% 20%	4766
February	1st to 10th	Day	20% 2 9% 22% 28% 20%	2000
	11th to 20th	Day	16% 3 10% 23% 30% 18%	1960
	21st to end	Day	20% 3 10% 24% 31% 12%	1650
March	1st to 10th	Day	17% 5% 13% 25% 25% 15%	3238
	11th to 20th	Day	19% 4 12% 28% 23% 14%	3378
	21st to end	Day	15% 6% 14% 28% 26% 11%	4239
April	1st to 10th	Day	17% 3 9% 24% 30% 17%	2280
	11th to 20th	Day	12% 3 7% 23% 36% 20%	2252
	21st to end	Day	9% 3 9% 22% 38% 19%	2280
May	1st to 10th	Day	8% 2 6% 16% 38% 30%	4007
	11th to 20th	Day	7% 2 4 15% 42% 30%	4074
	21st to end	Day	7% 2 3 11% 40% 37%	4477
June	1st to 10th	Day	9% 2 5% 13% 30% 40%	2627
	11th to 20th	Day	6% 2 4 9% 23% 56%	2660
	21st to end	Day	6% 1 2 4 18% 68%	2660
July	1st to 10th	Day	5% 1 2 3 7% 82%	4351
	11th to 20th	Day	11% 2 3 6% 14% 64%	4345
	21st to end	Day	9% 3 3 11% 22% 51%	4302
August	1st to 10th	Day	9% 2 2 5% 26% 56%	3770
	11th to 20th	Day	4 1 2 3 18% 72%	3760
	21st to end	Day	4 1 2 5% 16% 72%	4179
September	1st to 10th	Day	9% 2 3 5% 19% 61%	2280
	11th to 20th	Day	4 1 3 8% 28% 56%	2147
	21st to end	Day	6% 1 2 8% 35% 48%	2090
October	1st to 10th	Day	7% 1 2 9% 22% 59%	3490
	11th to 20th	Day	10% 2 2 8% 33% 46%	3224
	21st to end	Day	13% 2 2 9% 38% 36%	3303
November	1st to 10th	Day	11% 2 5% 16% 38% 27%	1764
	11th to 20th	Day	12% 2 8% 19% 32% 27%	1800
	21st to end	Day	16% 4 7% 20% 28% 25%	1800
December	1st to 10th	Day	17% 4 6% 21% 27% 25%	2950
	11th to 20th	Day	21% 4 10% 25% 30% 10%	3271
	21st to end	Day	24% 6% 13% 26% 23% 8%	4004
January	1st to 10th	Night	14% 3 7% 29% 34% 14%	6306
	11th to 20th	Night	13% 5% 10% 24% 27% 21%	6161
	21st to end	Night	23% 4 12% 18% 23% 20%	6207
February	1st to 10th	Night	22% 2 10% 20% 26% 20%	2400
	11th to 20th	Night	16% 3 10% 21% 30% 20%	2339
	21st to end	Night	16% 3 11% 25% 29% 17%	1980
March	1st to 10th	Night	15% 5% 17% 23% 25% 16%	3856
	11th to 20th	Night	16% 7% 13% 28% 25% 12%	3817
	21st to end	Night	14% 4 12% 35% 27% 8%	3552
April	1st to 10th	Night	15% 3 10% 27% 29% 15%	1900
	11th to 20th	Night	11% 3 7% 28% 31% 19%	1879
	21st to end	Night	8% 2 7% 29% 41% 12%	1900
May	1st to 10th	Night	5% 2 7% 15% 47% 24%	2966
	11th to 20th	Night	5% 2 4 14% 46% 29%	2835
	21st to end	Night	4 2 4 14% 46% 31%	3110
June	1st to 10th	Night	6% 3 7% 17% 32% 36%	1548
	11th to 20th	Night	5% 2 3 12% 28% 50%	1520
	21st to end	Night	5% 1 2 6% 22% 65%	1520
July	1st to 10th	Night	3 1 2 3 9% 83%	2500
	11th to 20th	Night	8% 2 2 6% 14% 68%	2492
	21st to end	Night	7% 1 2 11% 24% 55%	3000
August	1st to 10th	Night	7% 2 2 7% 30% 52%	3156
	11th to 20th	Night	3 1 2 4 18% 73%	3156
	21st to end	Night	4 1 5% 22% 68%	3498
September	1st to 10th	Night	7% 1 2 6% 21% 63%	1900
	11th to 20th	Night	5% 2 3 8% 31% 52%	2033
	21st to end	Night	4 1 2 8% 33% 51%	2090
October	1st to 10th	Night	5% 1 2 8% 19% 65%	3490
	11th to 20th	Night	7% 1 3 8% 35% 47%	3710
	21st to end	Night	11% 1 2 7% 37% 41%	4259
November	1st to 10th	Night	9% 3 6% 19% 37% 27%	2535
	11th to 20th	Night	12% 2 8% 18% 31% 29%	2600
	21st to end	Night	16% 3 8% 20% 28% 25%	2600
December	1st to 10th	Night	15% 3 6% 19% 34% 23%	4240
	11th to 20th	Night	20% 5% 10% 27% 25% 12%	4926
	21st to end	Night	26% 6% 13% 27% 21% 8%	6952

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% 14% 40% 24% 7% 1	200
	11th to 20th	Day	16% 20% 30% 20% 13% 1	270
	21st to end	Day	14% 19% 33% 24% 8% 1	497
February	1st to 10th	Day	18% 19% 34% 20% 7% 2	500
	11th to 20th	Day	17% 23% 34% 19% 6% 1	495
	21st to end	Day	15% 24% 40% 17% 4	414
March	1st to 10th	Day	19% 25% 33% 18% 4 1	500
	11th to 20th	Day	17% 27% 31% 18% 6%	500
	21st to end	Day	17% 30% 35% 15% 4	531
April	1st to 10th	Day	15% 27% 32% 18% 8% 1	460
	11th to 20th	Day	13% 28% 34% 20% 4 1	452
	21st to end	Day	9% 25% 35% 22% 7% 2	460
May	1st to 10th	Day	10% 27% 35% 20% 6% 2	463
	11th to 20th	Day	6% 23% 32% 28% 8% 2	488
	21st to end	Day	9% 18% 32% 30% 8% 4	529
June	1st to 10th	Day	6% 13% 34% 31% 12% 3	490
	11th to 20th	Day	5% 16% 36% 29% 11% 2	490
	21st to end	Day	1 16% 35% 32% 11% 4	490
July	1st to 10th	Day	2 5% 34% 41% 13% 6%	486
	11th to 20th	Day	2 2 27% 45% 16% 7%	484
	21st to end	Day	2 4 27% 44% 16% 6%	531
August	1st to 10th	Day	4 7% 33% 37% 16% 4	487
	11th to 20th	Day	3 7% 27% 41% 16% 6%	477
	21st to end	Day	1 6% 33% 39% 16% 4	539
September	1st to 10th	Day	2 8% 32% 40% 17% 2	490
	11th to 20th	Day	4 13% 31% 38% 11% 2	490
	21st to end	Day	4 14% 33% 32% 16% 1	490
October	1st to 10th	Day	5% 13% 35% 34% 12% 1	490
	11th to 20th	Day	6% 12% 37% 34% 10% 1	490
	21st to end	Day	7% 12% 37% 30% 11% 2	456
November	1st to 10th	Day	12% 11% 31% 31% 13% 2	300
	11th to 20th	Day	9% 14% 30% 31% 12% 3	300
	21st to end	Day	14% 15% 28% 30% 11% 2	300
December	1st to 10th	Day	7% 13% 35% 32% 12% 1	300
	11th to 20th	Day	9% 14% 37% 23% 15% 1	270
	21st to end	Day	20% 20% 28% 21% 9% 1	220
January	1st to 10th	Night	11% 9% 28% 27% 18% 8%	800
	11th to 20th	Night	7% 9% 28% 35% 16% 5%	800
	21st to end	Night	9% 12% 30% 28% 16% 4	880
February	1st to 10th	Night	9% 14% 29% 28% 16% 5%	800
	11th to 20th	Night	9% 11% 33% 28% 13% 6%	784
	21st to end	Night	8% 15% 34% 30% 10% 3	660
March	1st to 10th	Night	9% 17% 33% 26% 12% 3	800
	11th to 20th	Night	10% 17% 30% 23% 15% 5%	800
	21st to end	Night	8% 19% 35% 26% 11% 2	862
April	1st to 10th	Night	5% 21% 34% 24% 14% 3	760
	11th to 20th	Night	8% 16% 34% 26% 13% 2	751
	21st to end	Night	5% 18% 33% 25% 15% 3	760
May	1st to 10th	Night	5% 19% 37% 26% 10% 3	637
	11th to 20th	Night	4 16% 30% 33% 16% 2	561
	21st to end	Night	5% 17% 32% 33% 13% 1	617
June	1st to 10th	Night	2 7% 34% 43% 13% 1	408
	11th to 20th	Night	1 10% 37% 34% 15% 2	380
	21st to end	Night	2 5% 34% 41% 17% 1	380
July	1st to 10th	Night	1 3 23% 45% 26% 2	370
	11th to 20th	Night	2 1 15% 51% 29% 2	368
	21st to end	Night	2 2 18% 45% 32% 1	615
August	1st to 10th	Night	2 2 25% 40% 28% 3	756
	11th to 20th	Night	1 2 17% 45% 29% 6%	752
	21st to end	Night	2 2 17% 39% 33% 7%	836
September	1st to 10th	Night	1 4 14% 39% 34% 7%	760
	11th to 20th	Night	1 6% 21% 38% 27% 7%	760
	21st to end	Night	1 6% 21% 34% 29% 9%	760
October	1st to 10th	Night	2 7% 23% 45% 18% 4	760
	11th to 20th	Night	3 6% 23% 39% 19% 10%	760
	21st to end	Night	4 9% 23% 30% 23% 11%	836
November	1st to 10th	Night	3 11% 23% 31% 22% 9%	780
	11th to 20th	Night	4 6% 27% 34% 22% 7%	800
	21st to end	Night	7% 8% 28% 34% 18% 6%	800
December	1st to 10th	Night	6% 10% 28% 30% 20% 5%	800
	11th to 20th	Night	9% 7% 32% 32% 15% 5%	800
	21st to end	Night	10% 12% 31% 26% 17% 3	880

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