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 2025-04-11.

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	15% 10% 4 9% 5% 4 4 3 5% 6% 34%	113033
	Night	16% 13% 5% 10% 5% 5% 4 3 5% 6% 29%	115316
Transparency	Day	48% 6% 12% 21% 11% 1	116579
	Night	54% 6% 11% 18% 10% 1	119920
Seeing	Day	19% 11% 30% 26% 12% 2	15764
	Night	21% 12% 28% 25% 12% 2	25222

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% 9% 13% 6% 4 4 4 4 4 19%	3186
	11th to 20th	Day	12% 19% 9% 20% 11% 6% 4 3 4 3 9%	3589
	21st to end	Day	15% 18% 8% 16% 6% 6% 5% 3 4 5% 15%	4271
February	1st to 10th	Day	12% 16% 6% 16% 8% 5% 4 3 5% 6% 19%	1800
	11th to 20th	Day	12% 14% 5% 12% 7% 6% 5% 5% 6% 4 25%	1753
	21st to end	Day	13% 14% 5% 11% 6% 4 5% 4 5% 6% 27%	1635
March	1st to 10th	Day	17% 10% 3 7% 4 4 5% 4 5% 7% 35%	4697
	11th to 20th	Day	11% 12% 5% 10% 6% 6% 5% 5% 6% 7% 28%	4980
	21st to end	Day	17% 9% 4 8% 5% 4 4 4 5% 5% 36%	5465
April	1st to 10th	Day	18% 10% 3 7% 4 4 4 3 6% 6% 35%	2340
	11th to 20th	Day	19% 7% 2 6% 5% 4 3 3 4 6% 40%	2442
	21st to end	Day	19% 8% 3 6% 4 4 3 3 5% 8% 38%	2470
May	1st to 10th	Day	17% 6% 2 8% 4 3 3 3 5% 6% 44%	4108
	11th to 20th	Day	14% 7% 3 7% 4 4 3 3 5% 7% 42%	4234
	21st to end	Day	14% 5% 2 7% 5% 4 4 3 5% 6% 45%	4963
June	1st to 10th	Day	13% 7% 2 6% 6% 5% 4 4 6% 7% 40%	2850
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	2850
	21st to end	Day	14% 6% 2 6% 4 5% 5% 4 6% 7% 40%	2850
July	1st to 10th	Day	13% 7% 4 9% 5% 5% 4 3 5% 7% 39%	4760
	11th to 20th	Day	9% 4 2 5% 4 4 4 3 6% 8% 51%	4665
	21st to end	Day	9% 5% 2 5% 4 3 4 3 5% 7% 54%	4632
August	1st to 10th	Day	10% 4 2 6% 4 5% 5% 4 6% 9% 45%	4104
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 6% 8% 47%	4044
	21st to end	Day	10% 4 2 6% 5% 5% 4 4 6% 8% 47%	4532
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 4 3 5% 7% 46%	2245
	11th to 20th	Day	12% 4 2 5% 4 4 4 3 5% 8% 50%	2090
	21st to end	Day	17% 7% 2 7% 4 4 5% 3 5% 7% 40%	2090
October	1st to 10th	Day	18% 7% 2 7% 5% 5% 4 4 5% 5% 37%	1952
	11th to 20th	Day	24% 10% 3 8% 5% 6% 5% 3 5% 6% 27%	1900
	21st to end	Day	25% 14% 4 8% 6% 5% 3 4 5% 6% 22%	1952
November	1st to 10th	Day	18% 15% 4 8% 5% 4 4 4 5% 6% 26%	1736
	11th to 20th	Day	17% 19% 6% 9% 4 5% 5% 3 6% 7% 19%	1600
	21st to end	Day	25% 22% 6% 9% 6% 4 4 4 5% 4 13%	1600
December	1st to 10th	Day	17% 26% 8% 10% 7% 5% 4 3 4 4 13%	2551
	11th to 20th	Day	21% 21% 8% 15% 5% 3 3 3 4 4 13%	2621
	21st to end	Day	28% 25% 8% 14% 5% 3 5% 2 3 2 5%	3476
January	1st to 10th	Night	12% 20% 10% 13% 7% 4 4 3 4 4 19%	6762
	11th to 20th	Night	12% 19% 7% 20% 7% 5% 4 3 4 4 14%	6316
	21st to end	Night	12% 19% 8% 15% 7% 7% 4 3 4 4 18%	6692
February	1st to 10th	Night	11% 17% 6% 16% 8% 5% 4 3 5% 5% 20%	2600
	11th to 20th	Night	11% 16% 5% 11% 8% 4 5% 4 6% 5% 25%	2533
	21st to end	Night	14% 15% 5% 10% 5% 5% 5% 4 5% 5% 27%	1993
March	1st to 10th	Night	16% 8% 3 8% 4 4 4 3 5% 6% 38%	5143
	11th to 20th	Night	12% 11% 4 8% 5% 5% 5% 4 6% 7% 34%	4979
	21st to end	Night	18% 10% 5% 10% 5% 4 3 3 4 4 33%	5467
April	1st to 10th	Night	20% 9% 3 7% 4 4 4 3 5% 5% 35%	2075
	11th to 20th	Night	19% 8% 2 5% 4 4 3 3 6% 8% 37%	1693
	21st to end	Night	19% 9% 4 9% 4 4 4 3 6% 5% 34%	1710
May	1st to 10th	Night	16% 6% 2 9% 5% 5% 5% 3 4 5% 40%	2833
	11th to 20th	Night	12% 6% 3 8% 6% 4 5% 3 5% 8% 41%	2657
	21st to end	Night	13% 7% 3 8% 5% 3 4 3 5% 6% 42%	2600
June	1st to 10th	Night	12% 7% 2 7% 5% 4 5% 5% 7% 6% 40%	1330
	11th to 20th	Night	10% 6% 2 4 4 4 6% 5% 7% 8% 44%	1330
	21st to end	Night	13% 6% 2 6% 5% 5% 5% 4 6% 6% 41%	1330
July	1st to 10th	Night	12% 5% 3 7% 5% 4 4 3 4 7% 47%	2210
	11th to 20th	Night	10% 4 2 5% 4 4 3 3 6% 8% 51%	2301
	21st to end	Night	9% 5% 2 6% 4 4 4 3 4 7% 52%	2924
August	1st to 10th	Night	8% 6% 2 6% 4 5% 4 4 7% 8% 46%	2825
	11th to 20th	Night	13% 5% 2 6% 4 4 4 4 6% 9% 44%	2785
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 7% 49%	3124
September	1st to 10th	Night	12% 4 2 6% 4 4 4 3 5% 7% 47%	1913
	11th to 20th	Night	11% 5% 2 6% 3 4 4 4 5% 7% 50%	2090
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 5% 7% 39%	2090
October	1st to 10th	Night	21% 8% 3 7% 5% 4 4 3 4 6% 35%	2228
	11th to 20th	Night	25% 11% 3 8% 5% 4 4 4 4 7% 25%	2280
	21st to end	Night	25% 13% 4 9% 6% 4 4 4 5% 6% 22%	2641
November	1st to 10th	Night	20% 16% 3 8% 4 4 4 3 5% 6% 28%	2561
	11th to 20th	Night	19% 20% 5% 10% 6% 5% 5% 3 4 6% 18%	2800
	21st to end	Night	23% 22% 6% 9% 5% 4 4 3 5% 4 15%	2800
December	1st to 10th	Night	19% 23% 5% 10% 6% 4 4 3 4 5% 17%	4613
	11th to 20th	Night	19% 21% 7% 16% 6% 5% 4 3 3 4 12%	5586
	21st to end	Night	26% 23% 8% 12% 5% 5% 4 2 3 3 10%	7502

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	62% 12% 9% 13% 3 2	3187
	11th to 20th	Day	80% 5% 6% 6% 4	3620
	21st to end	Day	70% 7% 10% 9% 4	4271
February	1st to 10th	Day	65% 6% 11% 15% 3	1800
	11th to 20th	Day	59% 7% 13% 14% 7% 1	1762
	21st to end	Day	57% 6% 11% 19% 5%	1635
March	1st to 10th	Day	49% 6% 14% 13% 16% 3	4700
	11th to 20th	Day	54% 6% 14% 17% 8% 1	4980
	21st to end	Day	49% 6% 15% 16% 11% 2	5465
April	1st to 10th	Day	49% 6% 12% 20% 12% 1	2340
	11th to 20th	Day	45% 5% 8% 26% 14% 1	2442
	21st to end	Day	46% 4 12% 21% 14% 3	2470
May	1st to 10th	Day	41% 5% 10% 23% 18% 2	4120
	11th to 20th	Day	39% 6% 13% 26% 14% 1	4238
	21st to end	Day	39% 5% 13% 18% 22% 3	4963
June	1st to 10th	Day	40% 7% 11% 27% 13% 2	2850
	11th to 20th	Day	36% 5% 12% 27% 17% 2	2850
	21st to end	Day	42% 6% 12% 25% 13% 2	2850
July	1st to 10th	Day	43% 7% 13% 23% 13% 1	4686
	11th to 20th	Day	29% 7% 16% 34% 13% 1	4584
	21st to end	Day	29% 6% 11% 29% 23% 1	4485
August	1st to 10th	Day	33% 8% 15% 29% 13% 1	4091
	11th to 20th	Day	35% 6% 17% 29% 12%	4083
	21st to end	Day	34% 8% 14% 35% 10% 1	4531
September	1st to 10th	Day	38% 6% 14% 30% 11% 1	2245
	11th to 20th	Day	34% 6% 16% 32% 12% 1	2090
	21st to end	Day	44% 8% 15% 23% 10%	2090
October	1st to 10th	Day	38% 5% 10% 28% 19%	3238
	11th to 20th	Day	47% 5% 15% 24% 9%	3140
	21st to end	Day	58% 4 14% 17% 6%	3189
November	1st to 10th	Day	57% 7% 13% 18% 6%	1736
	11th to 20th	Day	64% 5% 13% 12% 5%	1600
	21st to end	Day	73% 5% 12% 8% 2	1600
December	1st to 10th	Day	73% 5% 13% 7% 1	2551
	11th to 20th	Day	73% 6% 10% 8% 3	2621
	21st to end	Day	83% 7% 5% 4 1	3476
January	1st to 10th	Night	63% 10% 9% 13% 5% 1	6762
	11th to 20th	Night	71% 6% 9% 9% 5%	6360
	21st to end	Night	70% 5% 9% 9% 6% 1	6692
February	1st to 10th	Night	65% 5% 10% 15% 4 1	2600
	11th to 20th	Night	59% 5% 13% 16% 6% 1	2535
	21st to end	Night	58% 6% 12% 15% 8%	1993
March	1st to 10th	Night	46% 6% 15% 16% 14% 3	5153
	11th to 20th	Night	48% 5% 16% 21% 9% 2	4980
	21st to end	Night	53% 5% 9% 18% 13% 2	5467
April	1st to 10th	Night	50% 4 10% 21% 14% 2	2075
	11th to 20th	Night	45% 4 8% 23% 18% 2	1693
	21st to end	Night	51% 5% 8% 17% 15% 3	1710
May	1st to 10th	Night	45% 5% 10% 23% 16% 2	2840
	11th to 20th	Night	40% 7% 10% 23% 18% 2	2658
	21st to end	Night	41% 6% 11% 20% 17% 5%	2601
June	1st to 10th	Night	41% 7% 8% 24% 18% 3	1330
	11th to 20th	Night	35% 6% 12% 24% 21% 2	1330
	21st to end	Night	43% 4 13% 24% 13% 2	1330
July	1st to 10th	Night	37% 6% 13% 24% 16% 4	2175
	11th to 20th	Night	30% 6% 10% 39% 14% 1	2259
	21st to end	Night	33% 5% 10% 25% 26% 1	2831
August	1st to 10th	Night	34% 7% 14% 30% 13% 1	2814
	11th to 20th	Night	35% 8% 17% 26% 14%	2812
	21st to end	Night	33% 6% 14% 32% 13% 1	3124
September	1st to 10th	Night	36% 5% 14% 29% 14% 2	1913
	11th to 20th	Night	34% 6% 14% 34% 11% 1	2090
	21st to end	Night	44% 6% 15% 24% 10%	2090
October	1st to 10th	Night	37% 5% 9% 31% 18%	3722
	11th to 20th	Night	48% 5% 15% 23% 10%	3779
	21st to end	Night	53% 6% 16% 18% 6%	4341
November	1st to 10th	Night	56% 6% 11% 20% 6%	2561
	11th to 20th	Night	67% 5% 13% 11% 4 1	2800
	21st to end	Night	71% 6% 12% 10% 2	2800
December	1st to 10th	Night	68% 6% 15% 8% 2	4613
	11th to 20th	Night	75% 6% 8% 8% 3	5585
	21st to end	Night	78% 7% 7% 5% 2	7502

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% 17% 31% 20% 5%	207
	11th to 20th	Day	20% 19% 35% 20% 6%	300
	21st to end	Day	28% 10% 33% 19% 9%	330
February	1st to 10th	Day	22% 24% 33% 17% 4	300
	11th to 20th	Day	20% 21% 38% 17% 3	300
	21st to end	Day	24% 27% 35% 11% 3	249
March	1st to 10th	Day	22% 16% 37% 20% 5% 1	390
	11th to 20th	Day	18% 16% 34% 24% 6% 1	500
	21st to end	Day	23% 16% 31% 23% 6% 1	550
April	1st to 10th	Day	23% 13% 32% 24% 8%	500
	11th to 20th	Day	27% 15% 27% 18% 10% 2	452
	21st to end	Day	25% 13% 34% 17% 8% 1	460
May	1st to 10th	Day	22% 7% 36% 25% 8% 2	463
	11th to 20th	Day	18% 8% 31% 29% 12% 3	487
	21st to end	Day	14% 7% 32% 29% 15% 3	603
June	1st to 10th	Day	14% 7% 34% 31% 13% 1	680
	11th to 20th	Day	13% 7% 29% 34% 15% 2	680
	21st to end	Day	17% 7% 28% 33% 13% 2	680
July	1st to 10th	Day	9% 4 25% 41% 18% 2	671
	11th to 20th	Day	10% 5% 25% 37% 18% 4	668
	21st to end	Day	11% 3 26% 37% 18% 4	633
August	1st to 10th	Day	14% 5% 22% 34% 20% 4	486
	11th to 20th	Day	12% 5% 19% 35% 20% 9%	479
	21st to end	Day	13% 7% 24% 31% 20% 5%	539
September	1st to 10th	Day	12% 9% 28% 27% 20% 5%	490
	11th to 20th	Day	10% 9% 24% 28% 20% 9%	490
	21st to end	Day	19% 10% 22% 27% 17% 4	490
October	1st to 10th	Day	21% 15% 25% 25% 12% 2	490
	11th to 20th	Day	24% 16% 34% 19% 7% 1	490
	21st to end	Day	28% 20% 34% 15% 3	401
November	1st to 10th	Day	28% 17% 37% 14% 5%	286
	11th to 20th	Day	26% 21% 34% 17% 3	200
	21st to end	Day	33% 24% 31% 12% 1	200
December	1st to 10th	Day	27% 21% 31% 16% 5% 1	200
	11th to 20th	Day	33% 23% 33% 10% 2	200
	21st to end	Day	35% 20% 34% 7% 3	220
January	1st to 10th	Night	23% 20% 29% 22% 4 1	1000
	11th to 20th	Night	26% 17% 30% 22% 4 1	1000
	21st to end	Night	22% 12% 35% 22% 8% 1	965
February	1st to 10th	Night	20% 18% 35% 22% 5%	800
	11th to 20th	Night	19% 15% 35% 24% 7% 1	783
	21st to end	Night	21% 15% 37% 22% 5%	660
March	1st to 10th	Night	18% 15% 38% 22% 6% 1	800
	11th to 20th	Night	18% 14% 34% 23% 9% 1	800
	21st to end	Night	20% 12% 30% 29% 9% 1	880
April	1st to 10th	Night	24% 11% 34% 25% 5% 1	746
	11th to 20th	Night	23% 11% 28% 25% 10% 2	565
	21st to end	Night	22% 9% 29% 25% 14% 1	570
May	1st to 10th	Night	16% 6% 27% 35% 13% 4	570
	11th to 20th	Night	16% 6% 26% 34% 17% 1	471
	21st to end	Night	16% 4 25% 33% 20% 3	411
June	1st to 10th	Night	14% 4 32% 34% 14% 2	380
	11th to 20th	Night	11% 8% 21% 38% 20% 2	380
	21st to end	Night	14% 4 19% 36% 24% 2	380
July	1st to 10th	Night	10% 3 19% 41% 23% 4	370
	11th to 20th	Night	9% 3 18% 38% 26% 6%	420
	21st to end	Night	9% 4 22% 34% 28% 4	624
August	1st to 10th	Night	10% 3 19% 37% 25% 5%	567
	11th to 20th	Night	12% 3 16% 31% 32% 7%	564
	21st to end	Night	12% 3 22% 31% 25% 6%	627
September	1st to 10th	Night	13% 6% 25% 27% 21% 8%	713
	11th to 20th	Night	13% 5% 24% 30% 18% 11%	760
	21st to end	Night	18% 9% 22% 26% 20% 5%	760
October	1st to 10th	Night	21% 10% 26% 28% 13% 2	760
	11th to 20th	Night	29% 13% 26% 20% 11% 1	760
	21st to end	Night	29% 15% 29% 20% 5% 1	836
November	1st to 10th	Night	27% 14% 27% 22% 8% 1	780
	11th to 20th	Night	27% 21% 28% 17% 7%	800
	21st to end	Night	31% 17% 30% 17% 4	800
December	1st to 10th	Night	31% 21% 29% 12% 6%	820
	11th to 20th	Night	30% 21% 32% 13% 3 1	1000
	21st to end	Night	35% 15% 30% 15% 5% 1	1100

Page generated at 2025-04-08 09:17:24. Version ac07

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