Chi'Cheemaun 2/3rds Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chi'Cheemaun 2/3rds Point 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	14% 10% 4 9% 5% 4 4 3 5% 6% 36%	143886
	Night	15% 13% 5% 10% 5% 4 4 3 5% 6% 30%	138134
Transparency	Day	47% 6% 12% 22% 11% 1	147388
	Night	53% 6% 11% 19% 10% 1	142707
Seeing	Day	18% 11% 28% 27% 13% 3	17651
	Night	21% 12% 28% 25% 12% 2	26830

By Month

Percentage Cloud Cover NE (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	16% 18% 9% 14% 6% 4 4 3 4 4 20%	4136
	11th to 20th	Day	12% 21% 9% 19% 10% 6% 4 3 3 3 10%	4679
	21st to end	Day	11% 15% 7% 16% 7% 6% 5% 4 4 5% 18%	5533
February	1st to 10th	Day	12% 16% 6% 15% 7% 5% 4 3 4 6% 20%	1890
	11th to 20th	Day	13% 14% 5% 12% 7% 6% 5% 5% 5% 4 25%	1843
	21st to end	Day	13% 14% 5% 11% 6% 4 5% 4 5% 6% 26%	1714
March	1st to 10th	Day	17% 10% 3 7% 4 4 5% 4 5% 6% 35%	4801
	11th to 20th	Day	12% 12% 5% 10% 6% 6% 5% 5% 6% 7% 28%	5090
	21st to end	Day	17% 9% 4 8% 5% 4 4 4 5% 5% 36%	5586
April	1st to 10th	Day	18% 10% 3 7% 4 4 4 3 6% 6% 35%	2456
	11th to 20th	Day	19% 7% 2 6% 5% 4 3 3 4 6% 41%	2702
	21st to end	Day	18% 8% 3 6% 4 4 3 3 5% 8% 38%	2730
May	1st to 10th	Day	14% 5% 2 7% 4 3 4 3 5% 7% 45%	7642
	11th to 20th	Day	14% 7% 3 8% 5% 4 4 3 5% 7% 40%	7919
	21st to end	Day	16% 7% 2 7% 4 4 4 3 4 6% 43%	9298
June	1st to 10th	Day	13% 7% 2 6% 6% 5% 4 4 6% 7% 41%	3150
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 4 6% 8% 42%	3150
	21st to end	Day	15% 6% 2 7% 4 5% 5% 4 6% 7% 39%	3150
July	1st to 10th	Day	12% 6% 4 11% 6% 5% 4 3 5% 8% 37%	8879
	11th to 20th	Day	8% 4 2 6% 4 4 4 3 6% 9% 51%	8701
	21st to end	Day	7% 5% 2 6% 4 3 4 3 5% 7% 52%	8642
August	1st to 10th	Day	10% 4 2 6% 4 5% 5% 4 6% 9% 45%	4364
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 6% 8% 47%	4226
	21st to end	Day	9% 4 2 6% 5% 5% 4 4 6% 8% 47%	4675
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 3 5% 8% 45%	2362
	11th to 20th	Day	12% 4 2 4 4 4 4 3 6% 8% 50%	2200
	21st to end	Day	17% 7% 2 7% 4 4 5% 3 5% 7% 40%	2200
October	1st to 10th	Day	18% 7% 2 7% 5% 5% 4 4 5% 6% 38%	2055
	11th to 20th	Day	24% 9% 3 7% 4 5% 5% 3 5% 6% 28%	2000
	21st to end	Day	24% 13% 4 7% 6% 5% 3 4 5% 6% 23%	2055
November	1st to 10th	Day	18% 15% 4 8% 5% 4 4 4 5% 6% 26%	1824
	11th to 20th	Day	17% 19% 6% 9% 4 5% 5% 3 6% 7% 20%	1680
	21st to end	Day	24% 22% 6% 9% 6% 4 4 4 5% 5% 13%	1680
December	1st to 10th	Day	17% 26% 8% 10% 7% 5% 4 3 4 4 14%	2630
	11th to 20th	Day	21% 21% 8% 15% 5% 3 3 3 4 4 12%	2691
	21st to end	Day	27% 25% 8% 14% 5% 3 5% 2 3 2 5%	3553
January	1st to 10th	Night	13% 19% 10% 14% 6% 4 4 3 4 4 19%	8771
	11th to 20th	Night	11% 22% 8% 19% 7% 5% 4 3 4 4 13%	8236
	21st to end	Night	9% 16% 7% 16% 9% 7% 4 3 4 4 20%	8659
February	1st to 10th	Night	11% 17% 6% 15% 8% 5% 4 3 5% 5% 21%	2730
	11th to 20th	Night	11% 16% 5% 11% 8% 4 5% 4 6% 5% 25%	2663
	21st to end	Night	14% 16% 5% 10% 5% 5% 5% 4 5% 5% 26%	2089
March	1st to 10th	Night	16% 8% 3 8% 4 4 4 3 5% 6% 38%	5259
	11th to 20th	Night	12% 11% 4 8% 5% 5% 5% 4 6% 7% 34%	5089
	21st to end	Night	18% 10% 5% 10% 5% 4 3 3 4 5% 33%	5588
April	1st to 10th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 35%	2178
	11th to 20th	Night	19% 7% 2 6% 4 4 3 3 6% 8% 38%	1867
	21st to end	Night	18% 8% 4 9% 4 4 4 3 6% 5% 34%	1890
May	1st to 10th	Night	14% 6% 3 8% 4 5% 5% 4 5% 6% 40%	5257
	11th to 20th	Night	15% 6% 3 7% 5% 4 4 3 5% 6% 43%	4939
	21st to end	Night	16% 7% 3 8% 4 3 3 3 4 5% 42%	4872
June	1st to 10th	Night	12% 7% 2 6% 5% 4 5% 5% 7% 6% 42%	1470
	11th to 20th	Night	10% 6% 2 5% 4 5% 6% 5% 7% 8% 43%	1470
	21st to end	Night	13% 6% 3 6% 5% 5% 5% 4 6% 6% 40%	1470
July	1st to 10th	Night	12% 5% 3 8% 5% 4 4 3 4 8% 44%	4110
	11th to 20th	Night	10% 4 2 6% 4 4 4 3 6% 8% 50%	4285
	21st to end	Night	10% 6% 2 7% 4 4 3 4 5% 8% 48%	5435
August	1st to 10th	Night	9% 6% 2 6% 4 5% 4 4 6% 8% 46%	3005
	11th to 20th	Night	13% 5% 2 6% 4 4 4 4 6% 9% 44%	2911
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 7% 50%	3223
September	1st to 10th	Night	12% 4 2 7% 4 4 4 3 5% 7% 47%	2014
	11th to 20th	Night	11% 4 2 6% 3 4 4 4 5% 7% 50%	2200
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 5% 7% 40%	2200
October	1st to 10th	Night	20% 8% 3 7% 5% 4 4 3 5% 7% 36%	2345
	11th to 20th	Night	25% 11% 3 8% 5% 5% 4 4 4 7% 25%	2400
	21st to end	Night	24% 13% 4 8% 5% 4 4 3 5% 6% 23%	2780
November	1st to 10th	Night	19% 16% 3 8% 5% 4 4 3 5% 6% 27%	2692
	11th to 20th	Night	18% 20% 5% 10% 6% 5% 4 3 4 6% 19%	2940
	21st to end	Night	23% 23% 6% 9% 5% 4 4 3 5% 4 15%	2940
December	1st to 10th	Night	18% 24% 6% 10% 6% 4 4 3 4 5% 17%	4754
	11th to 20th	Night	19% 21% 7% 16% 6% 5% 4 3 3 4 12%	5736
	21st to end	Night	26% 22% 8% 12% 5% 5% 4 2 3 3 10%	7667

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	63% 10% 9% 12% 4 1	4137
	11th to 20th	Day	80% 4 5% 5% 5%	4710
	21st to end	Day	66% 6% 10% 10% 7%	5533
February	1st to 10th	Day	64% 6% 10% 15% 4	1890
	11th to 20th	Day	59% 7% 13% 13% 6%	1852
	21st to end	Day	58% 7% 11% 19% 5%	1714
March	1st to 10th	Day	49% 6% 14% 13% 16% 3	4804
	11th to 20th	Day	54% 6% 14% 17% 8% 1	5090
	21st to end	Day	49% 6% 15% 16% 11% 2	5586
April	1st to 10th	Day	49% 6% 12% 21% 11% 1	2456
	11th to 20th	Day	45% 5% 8% 26% 15% 1	2702
	21st to end	Day	46% 4 12% 21% 13% 3	2730
May	1st to 10th	Day	39% 5% 11% 27% 15% 3	7651
	11th to 20th	Day	42% 6% 10% 23% 18% 1	7923
	21st to end	Day	42% 5% 10% 23% 17% 3	9299
June	1st to 10th	Day	40% 7% 10% 27% 14% 2	3150
	11th to 20th	Day	37% 6% 12% 28% 16% 2	3150
	21st to end	Day	42% 7% 12% 25% 13% 2	3150
July	1st to 10th	Day	41% 9% 12% 23% 12% 2	8806
	11th to 20th	Day	29% 6% 13% 39% 12% 1	8620
	21st to end	Day	30% 7% 12% 32% 19% 1	8452
August	1st to 10th	Day	33% 8% 15% 29% 13% 1	4351
	11th to 20th	Day	35% 6% 17% 30% 11%	4265
	21st to end	Day	34% 8% 14% 34% 10% 1	4674
September	1st to 10th	Day	38% 6% 15% 30% 10% 1	2362
	11th to 20th	Day	33% 6% 17% 32% 11% 1	2200
	21st to end	Day	44% 8% 14% 23% 10%	2200
October	1st to 10th	Day	38% 5% 10% 29% 18%	3341
	11th to 20th	Day	47% 5% 15% 25% 9%	3240
	21st to end	Day	57% 5% 14% 18% 6%	3292
November	1st to 10th	Day	57% 6% 13% 18% 5%	1824
	11th to 20th	Day	63% 5% 14% 13% 5%	1680
	21st to end	Day	73% 5% 12% 8% 2	1680
December	1st to 10th	Day	73% 5% 13% 7% 2	2630
	11th to 20th	Day	73% 6% 10% 8% 3	2691
	21st to end	Day	83% 8% 5% 4 1	3553
January	1st to 10th	Night	63% 10% 9% 12% 5% 1	8771
	11th to 20th	Night	74% 6% 7% 8% 5%	8280
	21st to end	Night	68% 5% 9% 10% 8% 1	8659
February	1st to 10th	Night	64% 5% 11% 15% 5% 1	2730
	11th to 20th	Night	59% 5% 13% 15% 6% 1	2665
	21st to end	Night	59% 6% 12% 16% 8%	2089
March	1st to 10th	Night	46% 6% 15% 17% 14% 3	5269
	11th to 20th	Night	48% 5% 16% 21% 9% 2	5090
	21st to end	Night	53% 5% 9% 18% 13% 2	5588
April	1st to 10th	Night	50% 4 10% 20% 13% 2	2178
	11th to 20th	Night	45% 4 7% 23% 18% 2	1867
	21st to end	Night	51% 5% 9% 17% 15% 3	1890
May	1st to 10th	Night	43% 5% 7% 24% 16% 4	5264
	11th to 20th	Night	42% 6% 8% 23% 20% 2	4940
	21st to end	Night	43% 5% 7% 23% 17% 4	4873
June	1st to 10th	Night	39% 7% 7% 24% 19% 3	1470
	11th to 20th	Night	36% 6% 12% 24% 20% 2	1470
	21st to end	Night	43% 5% 14% 24% 13% 2	1470
July	1st to 10th	Night	38% 6% 12% 24% 17% 3	4075
	11th to 20th	Night	30% 6% 11% 38% 14%	4243
	21st to end	Night	35% 5% 10% 30% 20% 1	5311
August	1st to 10th	Night	34% 7% 14% 30% 14% 1	2994
	11th to 20th	Night	35% 8% 17% 26% 14%	2938
	21st to end	Night	33% 6% 14% 33% 13% 1	3223
September	1st to 10th	Night	36% 5% 15% 29% 13% 2	2014
	11th to 20th	Night	34% 6% 14% 34% 11% 1	2200
	21st to end	Night	44% 6% 15% 25% 11%	2200
October	1st to 10th	Night	37% 5% 9% 32% 18%	3839
	11th to 20th	Night	48% 5% 15% 22% 10%	3899
	21st to end	Night	53% 6% 16% 19% 6%	4480
November	1st to 10th	Night	56% 6% 12% 20% 6%	2692
	11th to 20th	Night	66% 5% 13% 11% 4 1	2940
	21st to end	Night	71% 6% 11% 10% 2	2940
December	1st to 10th	Night	68% 6% 14% 8% 3	4754
	11th to 20th	Night	74% 6% 8% 8% 4	5735
	21st to end	Night	78% 7% 7% 5% 2	7667

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	26% 16% 33% 20% 5%	228
	11th to 20th	Day	20% 19% 36% 19% 5%	330
	21st to end	Day	26% 11% 31% 23% 9%	363
February	1st to 10th	Day	22% 22% 32% 18% 5% 1	330
	11th to 20th	Day	22% 19% 36% 18% 4 1	330
	21st to end	Day	23% 25% 35% 12% 4	273
March	1st to 10th	Day	22% 16% 37% 20% 5%	424
	11th to 20th	Day	20% 16% 35% 23% 6% 1	540
	21st to end	Day	23% 15% 31% 24% 6% 1	594
April	1st to 10th	Day	23% 13% 31% 24% 9%	540
	11th to 20th	Day	27% 14% 26% 19% 11% 3	532
	21st to end	Day	25% 13% 32% 19% 10% 1	540
May	1st to 10th	Day	20% 7% 35% 28% 9% 2	543
	11th to 20th	Day	17% 7% 30% 30% 14% 3	567
	21st to end	Day	15% 6% 30% 30% 15% 3	699
June	1st to 10th	Day	13% 6% 31% 33% 15% 1	780
	11th to 20th	Day	13% 7% 28% 35% 15% 2	780
	21st to end	Day	17% 7% 26% 36% 13% 2	780
July	1st to 10th	Day	9% 3 23% 41% 21% 3	771
	11th to 20th	Day	9% 5% 25% 37% 19% 4	768
	21st to end	Day	11% 3 24% 39% 19% 4	731
August	1st to 10th	Day	14% 4 19% 36% 23% 4	566
	11th to 20th	Day	11% 5% 18% 36% 21% 9%	535
	21st to end	Day	12% 7% 24% 31% 21% 5%	583
September	1st to 10th	Day	12% 9% 27% 27% 20% 5%	530
	11th to 20th	Day	9% 8% 22% 27% 21% 12%	530
	21st to end	Day	19% 10% 21% 28% 18% 4	530
October	1st to 10th	Day	20% 14% 24% 26% 14% 2	530
	11th to 20th	Day	25% 15% 32% 21% 7% 1	530
	21st to end	Day	27% 19% 32% 18% 4	438
November	1st to 10th	Day	28% 17% 34% 15% 5%	314
	11th to 20th	Day	25% 19% 33% 20% 3	220
	21st to end	Day	33% 23% 31% 13% 1	220
December	1st to 10th	Day	28% 20% 30% 17% 5% 1	220
	11th to 20th	Day	32% 24% 30% 10% 3	220
	21st to end	Day	34% 20% 33% 9% 3	242
January	1st to 10th	Night	23% 20% 29% 23% 4 1	1050
	11th to 20th	Night	25% 17% 30% 22% 4 1	1050
	21st to end	Night	21% 12% 35% 22% 8% 1	1013
February	1st to 10th	Night	20% 18% 35% 22% 6%	840
	11th to 20th	Night	18% 14% 34% 25% 7%	823
	21st to end	Night	21% 15% 36% 23% 5%	692
March	1st to 10th	Night	18% 15% 38% 23% 6% 1	840
	11th to 20th	Night	19% 15% 33% 23% 9% 1	840
	21st to end	Night	20% 11% 30% 29% 9% 1	924
April	1st to 10th	Night	24% 11% 34% 25% 6% 1	783
	11th to 20th	Night	22% 10% 29% 26% 9% 3	623
	21st to end	Night	22% 9% 28% 26% 14% 1	630
May	1st to 10th	Night	15% 6% 26% 36% 14% 3	630
	11th to 20th	Night	16% 6% 25% 34% 18% 1	521
	21st to end	Night	16% 4 24% 34% 20% 3	455
June	1st to 10th	Night	14% 4 29% 35% 16% 2	420
	11th to 20th	Night	12% 7% 21% 39% 20% 2	420
	21st to end	Night	14% 4 18% 39% 24% 2	420
July	1st to 10th	Night	10% 3 17% 43% 23% 4	410
	11th to 20th	Night	9% 3 17% 40% 26% 6%	466
	21st to end	Night	9% 3 21% 35% 29% 4	690
August	1st to 10th	Night	10% 3 18% 37% 27% 5%	627
	11th to 20th	Night	12% 3 15% 32% 31% 7%	606
	21st to end	Night	12% 3 22% 32% 26% 6%	660
September	1st to 10th	Night	13% 7% 25% 27% 20% 8%	751
	11th to 20th	Night	12% 5% 23% 29% 19% 12%	800
	21st to end	Night	18% 8% 21% 26% 21% 5%	800
October	1st to 10th	Night	20% 10% 25% 28% 15% 3	800
	11th to 20th	Night	29% 13% 26% 21% 11% 1	800
	21st to end	Night	28% 14% 29% 22% 6% 1	880
November	1st to 10th	Night	27% 15% 28% 22% 8% 1	820
	11th to 20th	Night	26% 20% 29% 17% 7%	840
	21st to end	Night	32% 17% 30% 17% 4	840
December	1st to 10th	Night	30% 21% 30% 13% 6%	861
	11th to 20th	Night	29% 21% 33% 13% 3 1	1050
	21st to end	Night	35% 15% 30% 15% 5% 1	1155

Page generated at 2026-08-12 03:37:21. Version ac07

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