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 2024-11-02.

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 8% 5% 4 4 3 5% 7% 35%	101467
	Night	15% 13% 5% 10% 5% 4 4 3 5% 6% 29%	97545
Transparency	Day	48% 8% 13% 20% 11% 1	101220
	Night	55% 8% 11% 16% 9% 1	97411
Seeing	Day	18% 8% 24% 30% 17% 3	15292
	Night	21% 10% 27% 26% 13% 3	24512

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	18% 22% 13% 13% 4 3 3 3 3 4 13%	2220
	11th to 20th	Day	13% 18% 8% 25% 10% 6% 4 2 4 4 6%	2530
	21st to end	Day	18% 20% 8% 13% 6% 6% 4 4 4 5% 12%	3009
February	1st to 10th	Day	12% 17% 7% 16% 8% 5% 4 3 5% 5% 18%	1710
	11th to 20th	Day	11% 14% 5% 12% 7% 6% 5% 4 6% 5% 24%	1663
	21st to end	Day	13% 15% 5% 11% 6% 4 4 3 5% 7% 27%	1551
March	1st to 10th	Day	16% 12% 3 7% 5% 4 5% 4 5% 6% 34%	3274
	11th to 20th	Day	10% 13% 6% 10% 6% 6% 5% 5% 5% 6% 29%	3480
	21st to end	Day	13% 8% 3 7% 5% 5% 4 4 5% 7% 37%	3815
April	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 4 6% 6% 34%	2218
	11th to 20th	Day	19% 6% 3 5% 5% 3 5% 3 4 6% 41%	2442
	21st to end	Day	18% 9% 3 6% 4 3 3 3 5% 8% 38%	2470
May	1st to 10th	Day	16% 7% 3 7% 4 4 3 3 5% 6% 43%	4108
	11th to 20th	Day	13% 8% 2 7% 5% 4 4 3 5% 8% 41%	4238
	21st to end	Day	14% 6% 2 7% 5% 5% 4 3 4 6% 45%	4932
June	1st to 10th	Day	12% 7% 2 6% 6% 4 5% 4 6% 7% 40%	2850
	11th to 20th	Day	11% 6% 3 6% 4 3 5% 4 7% 8% 43%	2850
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 5% 7% 40%	2850
July	1st to 10th	Day	12% 7% 3 8% 5% 4 5% 4 5% 7% 39%	4760
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 5% 8% 50%	4670
	21st to end	Day	8% 5% 2 5% 4 4 4 3 5% 7% 54%	4602
August	1st to 10th	Day	10% 5% 2 5% 4 4 5% 4 7% 9% 44%	4104
	11th to 20th	Day	14% 6% 2 5% 3 4 3 3 6% 8% 46%	4044
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 6% 8% 47%	4532
September	1st to 10th	Day	11% 6% 3 6% 5% 4 4 4 5% 7% 45%	2243
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 5% 8% 48%	2090
	21st to end	Day	17% 7% 2 6% 4 4 4 4 5% 7% 39%	2090
October	1st to 10th	Day	18% 9% 3 6% 4 4 5% 3 6% 7% 35%	1948
	11th to 20th	Day	23% 10% 2 9% 5% 5% 5% 4 4 7% 26%	1900
	21st to end	Day	25% 14% 4 8% 5% 4 4 3 5% 6% 21%	1964
November	1st to 10th	Day	17% 17% 4 9% 6% 5% 5% 3 5% 6% 24%	1652
	11th to 20th	Day	17% 18% 5% 10% 6% 4 5% 3 6% 6% 18%	1520
	21st to end	Day	24% 22% 4 9% 6% 4 4 4 5% 4 13%	1520
December	1st to 10th	Day	16% 28% 8% 14% 7% 4 3 3 4 4 10%	1516
	11th to 20th	Day	20% 23% 8% 14% 6% 4 3 3 4 3 13%	1671
	21st to end	Day	27% 25% 7% 14% 5% 4 3 2 3 3 5%	2431
January	1st to 10th	Night	17% 24% 11% 15% 6% 4 4 3 4 3 11%	4734
	11th to 20th	Night	14% 17% 8% 24% 8% 5% 5% 3 4 4 9%	4440
	21st to end	Night	16% 19% 7% 14% 7% 6% 5% 3 4 4 16%	4648
February	1st to 10th	Night	12% 19% 6% 16% 7% 5% 4 3 5% 5% 19%	2470
	11th to 20th	Night	11% 16% 5% 12% 7% 6% 4 4 6% 6% 23%	2403
	21st to end	Night	14% 16% 4 10% 6% 5% 5% 3 5% 4 27%	1903
March	1st to 10th	Night	13% 9% 3 7% 5% 4 5% 3 5% 6% 41%	3565
	11th to 20th	Night	9% 12% 4 8% 5% 4 5% 4 6% 7% 37%	3479
	21st to end	Night	12% 9% 5% 10% 6% 5% 4 4 5% 7% 34%	3817
April	1st to 10th	Night	21% 9% 2 6% 5% 4 4 3 6% 6% 34%	1976
	11th to 20th	Night	19% 7% 3 6% 3 4 4 3 6% 8% 37%	1687
	21st to end	Night	19% 9% 4 7% 5% 5% 3 4 5% 5% 35%	1710
May	1st to 10th	Night	15% 7% 3 9% 5% 4 5% 3 5% 6% 39%	2833
	11th to 20th	Night	11% 7% 2 8% 5% 4 5% 3 6% 7% 41%	2641
	21st to end	Night	12% 7% 3 8% 5% 4 4 3 5% 6% 42%	2630
June	1st to 10th	Night	12% 7% 3 8% 6% 4 5% 4 5% 7% 40%	1330
	11th to 20th	Night	9% 6% 2 4 4 5% 6% 4 7% 8% 45%	1330
	21st to end	Night	12% 6% 2 8% 5% 4 5% 4 6% 8% 40%	1330
July	1st to 10th	Night	11% 6% 2 8% 4 4 4 3 4 7% 46%	2210
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 6% 7% 50%	2296
	21st to end	Night	8% 5% 2 6% 4 4 4 3 5% 7% 51%	2952
August	1st to 10th	Night	9% 6% 2 6% 5% 4 5% 4 7% 8% 45%	2825
	11th to 20th	Night	12% 5% 2 7% 4 4 5% 4 6% 9% 43%	2785
	21st to end	Night	8% 5% 2 7% 4 3 5% 4 6% 7% 48%	3124
September	1st to 10th	Night	13% 4 2 5% 4 5% 4 4 5% 7% 47%	1914
	11th to 20th	Night	12% 5% 2 5% 4 3 5% 4 5% 6% 49%	2090
	21st to end	Night	19% 7% 2 5% 4 5% 4 4 6% 7% 38%	2090
October	1st to 10th	Night	21% 9% 3 7% 5% 5% 4 3 5% 6% 34%	2232
	11th to 20th	Night	25% 11% 3 9% 4 5% 4 4 5% 6% 24%	2280
	21st to end	Night	25% 13% 4 9% 5% 4 4 4 5% 6% 20%	2631
November	1st to 10th	Night	19% 18% 4 7% 5% 4 3 3 6% 6% 25%	2448
	11th to 20th	Night	18% 20% 6% 11% 6% 5% 4 4 4 6% 17%	2660
	21st to end	Night	22% 23% 6% 9% 5% 5% 4 3 5% 4 13%	2660
December	1st to 10th	Night	22% 26% 7% 12% 7% 4 3 3 3 4 9%	2660
	11th to 20th	Night	19% 22% 6% 14% 6% 5% 4 2 4 4 14%	3526
	21st to end	Night	26% 22% 7% 15% 5% 4 4 3 3 4 7%	5236

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	78% 10% 9% 3	2221
	11th to 20th	Day	87% 5% 4 2 1	2530
	21st to end	Day	75% 12% 8% 4 1	3009
February	1st to 10th	Day	70% 7% 11% 11% 2	1710
	11th to 20th	Day	62% 9% 12% 11% 5%	1672
	21st to end	Day	58% 8% 13% 17% 4	1551
March	1st to 10th	Day	49% 9% 16% 14% 10% 1	3277
	11th to 20th	Day	51% 10% 13% 19% 5% 1	3480
	21st to end	Day	43% 11% 16% 17% 10% 2	3815
April	1st to 10th	Day	49% 6% 14% 19% 10% 1	2218
	11th to 20th	Day	44% 6% 9% 25% 14% 2	2442
	21st to end	Day	44% 7% 14% 20% 13% 3	2470
May	1st to 10th	Day	39% 8% 12% 20% 19% 2	4120
	11th to 20th	Day	37% 10% 14% 24% 14% 1	4242
	21st to end	Day	37% 8% 13% 16% 22% 3	4932
June	1st to 10th	Day	40% 9% 12% 25% 13% 1	2850
	11th to 20th	Day	36% 7% 11% 28% 17% 1	2850
	21st to end	Day	40% 9% 12% 24% 13% 2	2850
July	1st to 10th	Day	42% 7% 14% 23% 13% 1	4686
	11th to 20th	Day	29% 7% 16% 34% 13% 1	4589
	21st to end	Day	29% 7% 11% 29% 24% 1	4456
August	1st to 10th	Day	33% 7% 16% 29% 14% 1	4091
	11th to 20th	Day	35% 7% 17% 29% 11%	4083
	21st to end	Day	33% 7% 15% 34% 10% 1	4531
September	1st to 10th	Day	38% 8% 14% 27% 12% 1	2243
	11th to 20th	Day	34% 8% 16% 30% 11% 1	2090
	21st to end	Day	45% 9% 14% 23% 9%	2090
October	1st to 10th	Day	49% 7% 13% 18% 13%	1948
	11th to 20th	Day	58% 8% 14% 14% 5%	1900
	21st to end	Day	64% 7% 12% 12% 4	1964
November	1st to 10th	Day	60% 8% 14% 13% 5%	1652
	11th to 20th	Day	66% 10% 10% 9% 4	1520
	21st to end	Day	75% 8% 10% 5% 1	1520
December	1st to 10th	Day	81% 8% 6% 3 2	1516
	11th to 20th	Day	77% 9% 7% 6%	1671
	21st to end	Day	84% 10% 5% 2	2431
January	1st to 10th	Night	78% 10% 7% 4 1	4734
	11th to 20th	Night	83% 8% 4 3 1	4440
	21st to end	Night	73% 12% 7% 6% 2	4648
February	1st to 10th	Night	70% 6% 9% 11% 3	2470
	11th to 20th	Night	64% 9% 10% 13% 5%	2405
	21st to end	Night	59% 9% 12% 12% 7%	1903
March	1st to 10th	Night	43% 10% 17% 19% 11% 1	3575
	11th to 20th	Night	43% 10% 14% 21% 10% 2	3480
	21st to end	Night	45% 15% 10% 18% 10% 2	3817
April	1st to 10th	Night	51% 6% 10% 19% 12% 2	1976
	11th to 20th	Night	43% 6% 9% 22% 17% 2	1687
	21st to end	Night	51% 7% 9% 15% 15% 3	1710
May	1st to 10th	Night	43% 8% 12% 19% 17% 2	2840
	11th to 20th	Night	38% 10% 11% 22% 18% 2	2642
	21st to end	Night	40% 8% 12% 19% 16% 5%	2631
June	1st to 10th	Night	41% 7% 10% 22% 18% 2	1330
	11th to 20th	Night	33% 8% 15% 22% 21% 2	1330
	21st to end	Night	41% 7% 14% 22% 14% 2	1330
July	1st to 10th	Night	37% 6% 12% 24% 16% 5%	2175
	11th to 20th	Night	32% 6% 11% 36% 15% 1	2254
	21st to end	Night	32% 7% 11% 25% 25% 1	2858
August	1st to 10th	Night	35% 7% 13% 30% 14% 1	2814
	11th to 20th	Night	38% 8% 17% 23% 13% 1	2812
	21st to end	Night	34% 8% 13% 32% 13% 1	3124
September	1st to 10th	Night	36% 8% 13% 27% 14% 2	1914
	11th to 20th	Night	34% 9% 15% 30% 12%	2090
	21st to end	Night	46% 8% 14% 23% 10%	2090
October	1st to 10th	Night	51% 6% 10% 21% 12%	2232
	11th to 20th	Night	61% 8% 11% 14% 4	2280
	21st to end	Night	65% 8% 9% 12% 5%	2631
November	1st to 10th	Night	59% 7% 11% 17% 5%	2448
	11th to 20th	Night	69% 9% 11% 8% 3 1	2660
	21st to end	Night	74% 9% 10% 6% 1	2660
December	1st to 10th	Night	82% 7% 7% 4 1	2660
	11th to 20th	Night	76% 8% 9% 6% 1	3525
	21st to end	Night	81% 9% 7% 2	5236

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	23% 17% 32% 22% 8%	186
	11th to 20th	Day	24% 11% 36% 23% 7%	270
	21st to end	Day	26% 10% 26% 28% 9%	297
February	1st to 10th	Day	19% 15% 37% 23% 6%	270
	11th to 20th	Day	19% 15% 36% 26% 4	270
	21st to end	Day	20% 23% 36% 19% 1	225
March	1st to 10th	Day	18% 10% 38% 26% 7% 1	362
	11th to 20th	Day	17% 13% 31% 29% 9% 1	460
	21st to end	Day	23% 9% 29% 30% 8% 1	506
April	1st to 10th	Day	20% 7% 32% 30% 10% 1	460
	11th to 20th	Day	24% 9% 28% 23% 12% 4	452
	21st to end	Day	21% 10% 28% 28% 12% 1	460
May	1st to 10th	Day	21% 3 25% 35% 14% 2	463
	11th to 20th	Day	16% 5% 20% 34% 22% 4	487
	21st to end	Day	12% 3 19% 37% 22% 6%	585
June	1st to 10th	Day	14% 3 21% 39% 21% 2	680
	11th to 20th	Day	12% 4 19% 39% 23% 3	680
	21st to end	Day	17% 3 17% 39% 20% 3	680
July	1st to 10th	Day	8% 2 14% 45% 27% 4	671
	11th to 20th	Day	10% 3 17% 38% 26% 6%	668
	21st to end	Day	11% 3 15% 39% 28% 4	616
August	1st to 10th	Day	14% 4 15% 32% 30% 6%	486
	11th to 20th	Day	11% 3 13% 34% 30% 10%	479
	21st to end	Day	13% 6% 18% 32% 25% 6%	539
September	1st to 10th	Day	14% 5% 22% 27% 27% 6%	490
	11th to 20th	Day	10% 5% 20% 25% 29% 11%	490
	21st to end	Day	19% 8% 19% 25% 23% 6%	490
October	1st to 10th	Day	22% 10% 24% 22% 18% 3	490
	11th to 20th	Day	24% 14% 30% 25% 7% 1	490
	21st to end	Day	31% 14% 28% 21% 4 1	413
November	1st to 10th	Day	25% 13% 34% 20% 8%	259
	11th to 20th	Day	25% 18% 36% 16% 6%	180
	21st to end	Day	32% 17% 32% 17% 1	180
December	1st to 10th	Day	27% 18% 30% 19% 5% 1	180
	11th to 20th	Day	29% 22% 31% 15% 3	180
	21st to end	Day	34% 21% 33% 10% 2 1	198
January	1st to 10th	Night	25% 17% 30% 22% 5% 1	950
	11th to 20th	Night	25% 16% 30% 23% 5% 1	950
	21st to end	Night	21% 9% 35% 26% 9% 2	900
February	1st to 10th	Night	21% 13% 37% 23% 5%	760
	11th to 20th	Night	19% 11% 36% 26% 8%	743
	21st to end	Night	22% 10% 38% 24% 5% 1	628
March	1st to 10th	Night	17% 10% 38% 28% 7% 1	760
	11th to 20th	Night	17% 11% 36% 25% 9% 2	760
	21st to end	Night	18% 7% 31% 31% 12% 1	836
April	1st to 10th	Night	25% 8% 31% 28% 8% 1	718
	11th to 20th	Night	22% 9% 25% 29% 12% 3	563
	21st to end	Night	22% 7% 26% 29% 14% 1	570
May	1st to 10th	Night	15% 4 23% 37% 18% 3	570
	11th to 20th	Night	16% 3 20% 38% 21% 2	468
	21st to end	Night	16% 3 17% 38% 23% 4	411
June	1st to 10th	Night	15% 3 23% 38% 18% 3	380
	11th to 20th	Night	11% 4 18% 41% 24% 4	380
	21st to end	Night	13% 2 16% 37% 28% 3	380
July	1st to 10th	Night	7% 3 11% 47% 28% 4	370
	11th to 20th	Night	10% 2 16% 36% 29% 7%	415
	21st to end	Night	9% 2 15% 41% 30% 4	624
August	1st to 10th	Night	10% 3 16% 35% 29% 7%	567
	11th to 20th	Night	12% 3 14% 31% 32% 9%	564
	21st to end	Night	12% 4 19% 32% 27% 6%	627
September	1st to 10th	Night	14% 4 20% 30% 23% 9%	722
	11th to 20th	Night	14% 5% 20% 29% 22% 11%	760
	21st to end	Night	20% 7% 19% 24% 23% 6%	760
October	1st to 10th	Night	24% 8% 24% 25% 18% 2	760
	11th to 20th	Night	31% 11% 25% 22% 11% 1	760
	21st to end	Night	32% 12% 27% 23% 5% 1	836
November	1st to 10th	Night	28% 14% 26% 24% 8% 1	745
	11th to 20th	Night	26% 18% 31% 16% 7%	760
	21st to end	Night	32% 15% 30% 18% 5%	760
December	1st to 10th	Night	34% 18% 28% 14% 6%	760
	11th to 20th	Night	29% 19% 34% 14% 4 1	950
	21st to end	Night	33% 17% 30% 15% 4	1045

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