Chi'Cheemaun 1/3rd Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chi'Cheemaun 1/3rd Point clear sky chart from 2005-11-06 to 2026-09-29.

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% 7% 35%	149487
	Night	15% 13% 5% 10% 5% 5% 4 3 5% 6% 29%	142078
Transparency	Day	48% 7% 12% 21% 11% 1	153004
	Night	56% 7% 10% 17% 9% 1	146649
Seeing	Day	18% 8% 23% 31% 18% 3	17811
	Night	21% 10% 26% 27% 13% 3	26964

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	15% 18% 10% 13% 7% 4 5% 3 6% 4 16%	4134
	11th to 20th	Day	12% 21% 9% 22% 11% 5% 4 2 3 3 7%	4679
	21st to end	Day	11% 15% 8% 15% 8% 7% 5% 4 5% 6% 16%	5587
February	1st to 10th	Day	12% 17% 6% 15% 8% 5% 4 3 5% 6% 19%	1890
	11th to 20th	Day	12% 14% 5% 12% 8% 6% 5% 4 5% 5% 23%	1843
	21st to end	Day	13% 14% 5% 12% 6% 5% 4 3 5% 6% 25%	1709
March	1st to 10th	Day	16% 10% 3 7% 5% 5% 5% 4 5% 7% 34%	4809
	11th to 20th	Day	11% 12% 5% 10% 6% 6% 6% 5% 5% 6% 28%	5090
	21st to end	Day	17% 9% 4 8% 5% 4 4 4 5% 6% 34%	5586
April	1st to 10th	Day	18% 9% 3 7% 5% 3 5% 4 5% 6% 35%	2452
	11th to 20th	Day	19% 7% 3 5% 5% 4 4 3 4 5% 41%	2702
	21st to end	Day	17% 9% 3 6% 4 3 3 3 5% 8% 38%	2730
May	1st to 10th	Day	14% 6% 3 7% 4 4 3 3 6% 7% 44%	7642
	11th to 20th	Day	12% 8% 3 8% 5% 5% 5% 3 5% 7% 39%	7923
	21st to end	Day	16% 8% 2 7% 4 4 4 3 4 6% 43%	9239
June	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 6% 7% 40%	3150
	11th to 20th	Day	11% 6% 3 6% 4 3 5% 4 7% 8% 42%	3150
	21st to end	Day	14% 7% 2 7% 4 4 5% 4 5% 7% 40%	3150
July	1st to 10th	Day	11% 7% 4 10% 5% 5% 5% 4 5% 7% 38%	8879
	11th to 20th	Day	7% 4 2 6% 4 4 4 3 5% 9% 51%	8706
	21st to end	Day	7% 5% 2 6% 4 4 4 3 5% 7% 52%	8598
August	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 43%	6014
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 6% 9% 50%	5951
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 6% 7% 39%	6594
September	1st to 10th	Day	11% 6% 3 7% 5% 4 5% 4 5% 8% 44%	2479
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 6% 9% 48%	2310
	21st to end	Day	16% 7% 3 7% 4 4 4 4 5% 7% 40%	2288
October	1st to 10th	Day	17% 9% 3 6% 4 4 5% 3 6% 7% 37%	2050
	11th to 20th	Day	24% 10% 2 8% 5% 5% 5% 4 4 7% 27%	2000
	21st to end	Day	24% 13% 4 8% 5% 4 4 4 5% 6% 22%	2067
November	1st to 10th	Day	18% 16% 3 9% 6% 5% 5% 3 4 6% 25%	1819
	11th to 20th	Day	17% 18% 5% 10% 6% 4 5% 4 6% 7% 19%	1680
	21st to end	Day	23% 23% 4 10% 6% 5% 4 3 5% 4 13%	1680
December	1st to 10th	Day	15% 28% 7% 13% 6% 4 4 3 4 4 12%	2663
	11th to 20th	Day	20% 22% 8% 16% 5% 4 4 3 3 4 11%	2691
	21st to end	Day	27% 24% 8% 15% 6% 3 5% 2 2 2 4	3553
January	1st to 10th	Night	13% 20% 10% 14% 6% 4 5% 3 5% 4 15%	8789
	11th to 20th	Night	12% 22% 8% 20% 7% 5% 4 3 4 4 11%	8236
	21st to end	Night	9% 15% 7% 17% 10% 8% 4 3 4 4 18%	8601
February	1st to 10th	Night	12% 18% 6% 16% 7% 5% 4 3 5% 5% 20%	2730
	11th to 20th	Night	12% 15% 5% 12% 7% 6% 4 4 6% 6% 23%	2663
	21st to end	Night	14% 17% 5% 10% 6% 5% 5% 3 5% 4 27%	2096
March	1st to 10th	Night	15% 9% 3 8% 5% 4 4 3 5% 6% 37%	5250
	11th to 20th	Night	12% 10% 4 8% 5% 5% 5% 4 6% 8% 33%	5089
	21st to end	Night	18% 10% 4 10% 5% 4 4 3 4 5% 32%	5588
April	1st to 10th	Night	20% 9% 3 7% 5% 4 4 3 6% 6% 34%	2184
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 6% 7% 38%	1867
	21st to end	Night	18% 9% 4 8% 5% 5% 3 4 5% 5% 35%	1890
May	1st to 10th	Night	13% 7% 3 8% 5% 5% 5% 4 5% 7% 39%	5257
	11th to 20th	Night	14% 7% 2 8% 5% 3 5% 3 5% 6% 43%	4923
	21st to end	Night	16% 8% 3 7% 5% 4 4 3 4 5% 42%	4928
June	1st to 10th	Night	11% 7% 3 7% 5% 4 4 4 5% 7% 41%	1470
	11th to 20th	Night	10% 6% 2 5% 4 6% 6% 4 7% 8% 43%	1470
	21st to end	Night	12% 6% 3 8% 4 4 5% 4 6% 8% 40%	1470
July	1st to 10th	Night	11% 5% 3 8% 4 4 4 3 5% 8% 44%	4110
	11th to 20th	Night	9% 4 2 6% 4 4 5% 4 6% 8% 49%	4280
	21st to end	Night	9% 6% 3 7% 4 4 4 3 5% 8% 47%	5489
August	1st to 10th	Night	12% 7% 3 6% 4 4 4 4 6% 8% 43%	4135
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 6% 9% 46%	4095
	21st to end	Night	12% 8% 3 8% 4 4 5% 4 5% 6% 42%	4532
September	1st to 10th	Night	12% 4 2 5% 4 4 4 3 5% 7% 47%	2116
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 5% 7% 49%	2310
	21st to end	Night	18% 7% 2 5% 4 5% 4 3 5% 7% 41%	2289
October	1st to 10th	Night	20% 9% 2 7% 5% 4 4 3 5% 6% 35%	2350
	11th to 20th	Night	25% 11% 3 9% 4 5% 4 4 5% 6% 24%	2400
	21st to end	Night	24% 13% 4 9% 5% 4 4 4 5% 6% 22%	2770
November	1st to 10th	Night	19% 17% 3 8% 5% 4 4 3 6% 6% 25%	2698
	11th to 20th	Night	18% 19% 6% 11% 6% 5% 4 4 4 6% 18%	2940
	21st to end	Night	22% 24% 6% 9% 5% 4 4 3 5% 4 14%	2940
December	1st to 10th	Night	19% 23% 6% 11% 6% 4 4 3 4 5% 14%	4720
	11th to 20th	Night	18% 22% 8% 17% 7% 5% 4 3 4 3 10%	5736
	21st to end	Night	25% 23% 7% 14% 5% 6% 3 2 3 4 8%	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	75% 7% 8% 9% 1 1	4135
	11th to 20th	Day	87% 5% 2 4 2	4710
	21st to end	Day	70% 9% 7% 8% 5%	5587
February	1st to 10th	Day	69% 6% 10% 12% 3	1890
	11th to 20th	Day	63% 9% 12% 10% 5%	1852
	21st to end	Day	60% 8% 12% 17% 4	1709
March	1st to 10th	Day	49% 7% 15% 12% 14% 3	4812
	11th to 20th	Day	53% 8% 14% 17% 7% 1	5090
	21st to end	Day	48% 9% 15% 18% 8% 2	5586
April	1st to 10th	Day	49% 6% 13% 21% 11% 1	2452
	11th to 20th	Day	44% 6% 9% 24% 15% 2	2702
	21st to end	Day	44% 6% 14% 21% 12% 3	2730
May	1st to 10th	Day	38% 6% 11% 26% 16% 3	7651
	11th to 20th	Day	41% 8% 10% 23% 18% 1	7927
	21st to end	Day	42% 5% 10% 22% 18% 3	9240
June	1st to 10th	Day	40% 8% 11% 25% 14% 2	3150
	11th to 20th	Day	37% 7% 11% 28% 16% 1	3150
	21st to end	Day	40% 8% 12% 25% 13% 1	3150
July	1st to 10th	Day	43% 7% 13% 23% 12% 2	8806
	11th to 20th	Day	29% 5% 13% 40% 12% 1	8625
	21st to end	Day	30% 6% 12% 31% 19%	8410
August	1st to 10th	Day	38% 6% 15% 26% 14% 2	6001
	11th to 20th	Day	32% 6% 20% 33% 10%	5990
	21st to end	Day	42% 7% 15% 28% 7% 1	6593
September	1st to 10th	Day	38% 8% 15% 27% 11% 1	2479
	11th to 20th	Day	33% 7% 16% 32% 11% 1	2310
	21st to end	Day	44% 8% 14% 22% 11% 1	2288
October	1st to 10th	Day	38% 5% 12% 27% 18%	3336
	11th to 20th	Day	50% 7% 13% 23% 8%	3240
	21st to end	Day	57% 6% 13% 17% 6%	3317
November	1st to 10th	Day	60% 7% 13% 15% 5%	1819
	11th to 20th	Day	65% 10% 11% 11% 4	1680
	21st to end	Day	75% 8% 9% 6% 1	1680
December	1st to 10th	Day	78% 7% 9% 4 1	2663
	11th to 20th	Day	80% 7% 8% 5%	2691
	21st to end	Day	86% 7% 5% 2	3553
January	1st to 10th	Night	75% 9% 6% 7% 2	8789
	11th to 20th	Night	81% 6% 4 7% 3	8280
	21st to end	Night	71% 9% 6% 8% 6% 1	8601
February	1st to 10th	Night	68% 6% 9% 12% 3	2730
	11th to 20th	Night	64% 8% 10% 13% 6%	2665
	21st to end	Night	59% 8% 11% 14% 7%	2096
March	1st to 10th	Night	48% 8% 14% 15% 12% 3	5260
	11th to 20th	Night	47% 8% 16% 19% 8% 1	5090
	21st to end	Night	52% 11% 8% 15% 12% 2	5588
April	1st to 10th	Night	51% 6% 10% 20% 12% 1	2184
	11th to 20th	Night	44% 6% 9% 22% 18% 2	1867
	21st to end	Night	51% 6% 9% 16% 15% 3	1890
May	1st to 10th	Night	43% 6% 9% 22% 17% 4	5264
	11th to 20th	Night	40% 7% 9% 22% 20% 1	4924
	21st to end	Night	44% 5% 8% 23% 17% 4	4929
June	1st to 10th	Night	39% 7% 10% 22% 19% 3	1470
	11th to 20th	Night	35% 7% 15% 22% 19% 1	1470
	21st to end	Night	41% 7% 14% 22% 13% 2	1470
July	1st to 10th	Night	38% 6% 12% 25% 17% 3	4075
	11th to 20th	Night	32% 5% 10% 37% 15% 1	4238
	21st to end	Night	35% 5% 10% 30% 20% 1	5363
August	1st to 10th	Night	39% 5% 12% 25% 18% 1	4124
	11th to 20th	Night	35% 7% 18% 30% 10%	4122
	21st to end	Night	43% 7% 12% 29% 9% 1	4532
September	1st to 10th	Night	35% 8% 14% 28% 13% 2	2116
	11th to 20th	Night	34% 8% 15% 31% 12% 1	2310
	21st to end	Night	44% 7% 13% 23% 12% 1	2289
October	1st to 10th	Night	37% 6% 9% 31% 18%	3844
	11th to 20th	Night	52% 6% 13% 19% 9%	3899
	21st to end	Night	55% 7% 14% 18% 5%	4470
November	1st to 10th	Night	60% 7% 11% 17% 5%	2698
	11th to 20th	Night	68% 8% 11% 8% 4 1	2940
	21st to end	Night	75% 9% 9% 6% 1	2940
December	1st to 10th	Night	76% 7% 10% 6% 2	4720
	11th to 20th	Night	80% 7% 7% 5% 1	5735
	21st to end	Night	82% 8% 7% 3 1	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	21% 17% 34% 21% 7%	228
	11th to 20th	Day	22% 12% 35% 22% 7%	330
	21st to end	Day	22% 12% 28% 28% 10%	363
February	1st to 10th	Day	17% 15% 37% 23% 7% 1	330
	11th to 20th	Day	20% 13% 35% 25% 5% 1	330
	21st to end	Day	21% 19% 34% 21% 5%	273
March	1st to 10th	Day	18% 11% 38% 26% 6% 1	432
	11th to 20th	Day	19% 12% 31% 29% 8% 1	540
	21st to end	Day	24% 8% 28% 30% 8% 1	594
April	1st to 10th	Day	20% 8% 31% 30% 10% 1	540
	11th to 20th	Day	24% 9% 27% 23% 13% 4	532
	21st to end	Day	21% 9% 26% 30% 13% 1	540
May	1st to 10th	Day	20% 3 25% 36% 15% 2	543
	11th to 20th	Day	15% 4 19% 35% 23% 4	567
	21st to end	Day	14% 3 19% 36% 22% 5%	679
June	1st to 10th	Day	13% 3 19% 39% 23% 2	780
	11th to 20th	Day	13% 4 19% 40% 22% 4	780
	21st to end	Day	16% 3 17% 41% 21% 3	780
July	1st to 10th	Day	8% 2 13% 43% 29% 5%	771
	11th to 20th	Day	9% 3 17% 38% 27% 6%	768
	21st to end	Day	10% 3 15% 39% 29% 4	713
August	1st to 10th	Day	13% 3 13% 33% 32% 6%	566
	11th to 20th	Day	10% 3 12% 36% 30% 10%	559
	21st to end	Day	14% 6% 17% 31% 26% 6%	627
September	1st to 10th	Day	12% 6% 21% 27% 27% 6%	570
	11th to 20th	Day	10% 5% 18% 26% 28% 13%	570
	21st to end	Day	18% 7% 17% 24% 26% 7%	562
October	1st to 10th	Day	21% 9% 23% 23% 19% 4	530
	11th to 20th	Day	24% 13% 28% 26% 7% 1	530
	21st to end	Day	30% 14% 26% 24% 5% 1	450
November	1st to 10th	Day	27% 14% 30% 20% 9%	312
	11th to 20th	Day	25% 16% 35% 20% 5%	220
	21st to end	Day	31% 18% 31% 17% 2	220
December	1st to 10th	Day	26% 19% 30% 19% 5% 2	220
	11th to 20th	Day	32% 21% 28% 15% 4	220
	21st to end	Day	35% 19% 31% 12% 2 1	242
January	1st to 10th	Night	24% 17% 31% 22% 5% 1	1050
	11th to 20th	Night	24% 17% 30% 23% 5% 1	1050
	21st to end	Night	19% 11% 35% 25% 8% 1	994
February	1st to 10th	Night	20% 13% 37% 23% 6%	840
	11th to 20th	Night	18% 11% 35% 26% 9% 1	823
	21st to end	Night	21% 10% 37% 25% 5% 1	692
March	1st to 10th	Night	17% 9% 37% 29% 7% 1	840
	11th to 20th	Night	18% 12% 35% 26% 9% 1	840
	21st to end	Night	19% 7% 31% 31% 12% 1	924
April	1st to 10th	Night	24% 9% 32% 27% 7% 1	794
	11th to 20th	Night	22% 9% 24% 30% 12% 4	623
	21st to end	Night	22% 8% 24% 30% 14% 1	630
May	1st to 10th	Night	15% 4 23% 38% 18% 3	630
	11th to 20th	Night	16% 3 20% 37% 21% 3	518
	21st to end	Night	16% 3 16% 38% 22% 4	455
June	1st to 10th	Night	15% 3 22% 38% 19% 3	420
	11th to 20th	Night	11% 4 18% 42% 23% 3	420
	21st to end	Night	13% 2 15% 39% 28% 3	420
July	1st to 10th	Night	7% 3 10% 47% 29% 4	410
	11th to 20th	Night	10% 2 15% 37% 29% 7%	461
	21st to end	Night	9% 2 15% 40% 30% 4	690
August	1st to 10th	Night	10% 3 15% 36% 30% 6%	627
	11th to 20th	Night	12% 3 13% 33% 31% 9%	624
	21st to end	Night	13% 4 18% 32% 27% 5%	693
September	1st to 10th	Night	14% 5% 20% 29% 24% 9%	798
	11th to 20th	Night	13% 5% 19% 28% 22% 12%	840
	21st to end	Night	19% 7% 18% 23% 25% 7%	833
October	1st to 10th	Night	23% 7% 23% 26% 19% 3	800
	11th to 20th	Night	30% 11% 25% 23% 10% 1	800
	21st to end	Night	31% 12% 26% 24% 5% 1	880
November	1st to 10th	Night	27% 13% 26% 25% 7% 1	820
	11th to 20th	Night	26% 18% 32% 17% 8%	840
	21st to end	Night	32% 15% 30% 18% 4	840
December	1st to 10th	Night	33% 19% 28% 14% 6%	840
	11th to 20th	Night	27% 19% 34% 15% 4 1	1050
	21st to end	Night	33% 17% 30% 15% 4 1	1155

Page generated at 2026-09-26 04:18:40. Version ac07

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