Inukshuk Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Inukshuk Observatory clear sky chart from 2005-11-06 to 2026-05-02.

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	13% 11% 4 10% 6% 5% 5% 4 5% 7% 32%	131967
	Night	12% 11% 5% 11% 6% 5% 4 4 5% 6% 31%	130825
Transparency	Day	51% 5% 11% 21% 11% 1	135407
	Night	53% 5% 11% 20% 10% 1	135459
Seeing	Day	20% 16% 32% 20% 9% 3	18036
	Night	19% 12% 32% 26% 9% 1	28050

By Month

Percentage Cloud Cover SE (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	8% 14% 6% 19% 12% 7% 5% 3 5% 5% 17%	4691
	11th to 20th	Day	5% 18% 7% 15% 11% 7% 10% 6% 4 6% 11%	4710
	21st to end	Day	7% 11% 7% 16% 6% 7% 7% 4 6% 8% 23%	5156
February	1st to 10th	Day	8% 13% 5% 12% 6% 6% 6% 5% 6% 7% 26%	1864
	11th to 20th	Day	8% 12% 5% 13% 7% 5% 6% 4 6% 7% 27%	1918
	21st to end	Day	11% 14% 7% 11% 8% 6% 5% 4 5% 6% 24%	1730
March	1st to 10th	Day	13% 9% 3 8% 5% 5% 4 3 5% 6% 39%	4580
	11th to 20th	Day	11% 11% 4 12% 7% 5% 6% 4 5% 7% 28%	4873
	21st to end	Day	22% 13% 5% 12% 4 4 4 3 3 4 26%	6047
April	1st to 10th	Day	16% 14% 5% 9% 5% 5% 5% 4 5% 7% 26%	2520
	11th to 20th	Day	19% 12% 5% 10% 4 5% 4 3 4 5% 29%	2494
	21st to end	Day	18% 12% 3 8% 4 5% 4 4 5% 6% 30%	2670
May	1st to 10th	Day	15% 8% 2 6% 4 4 3 3 4 5% 46%	6323
	11th to 20th	Day	12% 9% 3 7% 5% 4 5% 4 5% 6% 39%	6319
	21st to end	Day	13% 10% 3 8% 5% 5% 5% 3 6% 7% 34%	6935
June	1st to 10th	Day	14% 8% 2 7% 4 4 4 4 6% 9% 39%	2800
	11th to 20th	Day	15% 7% 3 7% 5% 5% 5% 4 7% 7% 35%	2800
	21st to end	Day	13% 7% 3 6% 5% 4 6% 5% 7% 10% 36%	2800
July	1st to 10th	Day	12% 5% 2 6% 4 5% 5% 4 6% 10% 40%	6360
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 9% 49%	6360
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 8% 43%	6924
August	1st to 10th	Day	12% 6% 3 8% 5% 5% 6% 5% 6% 7% 38%	4563
	11th to 20th	Day	14% 5% 2 5% 4 3 4 3 5% 8% 47%	4162
	21st to end	Day	14% 8% 3 7% 5% 4 4 3 5% 7% 40%	4312
September	1st to 10th	Day	15% 7% 3 6% 4 4 4 3 6% 7% 42%	2400
	11th to 20th	Day	14% 7% 3 6% 5% 4 4 5% 5% 7% 39%	2340
	21st to end	Day	15% 10% 3 7% 4 4 5% 3 5% 7% 36%	2200
October	1st to 10th	Day	16% 9% 3 7% 4 4 5% 4 6% 8% 35%	2025
	11th to 20th	Day	20% 14% 4 9% 5% 5% 5% 3 4 6% 24%	1975
	21st to end	Day	21% 15% 4 8% 5% 4 4 3 5% 6% 26%	1980
November	1st to 10th	Day	15% 15% 5% 8% 5% 4 5% 3 6% 5% 30%	1852
	11th to 20th	Day	15% 17% 5% 14% 6% 5% 4 4 4 4 22%	1756
	21st to end	Day	15% 14% 7% 15% 8% 5% 5% 4 5% 5% 17%	1680
December	1st to 10th	Day	8% 15% 8% 28% 9% 6% 4 3 3 3 12%	2690
	11th to 20th	Day	9% 20% 7% 18% 9% 5% 4 3 4 4 17%	3088
	21st to end	Day	19% 23% 6% 12% 6% 4 3 3 3 5% 16%	4070
January	1st to 10th	Night	10% 13% 6% 19% 12% 8% 4 2 4 4 16%	8232
	11th to 20th	Night	6% 17% 7% 18% 10% 8% 7% 5% 6% 5% 12%	8280
	21st to end	Night	5% 12% 7% 16% 8% 7% 5% 4 6% 6% 23%	9058
February	1st to 10th	Night	8% 12% 6% 13% 7% 7% 5% 4 5% 6% 26%	2751
	11th to 20th	Night	9% 11% 4 12% 7% 7% 6% 4 6% 6% 28%	2589
	21st to end	Night	11% 15% 6% 11% 7% 6% 5% 3 5% 5% 26%	2076
March	1st to 10th	Night	10% 7% 3 9% 5% 4 4 4 6% 9% 39%	5493
	11th to 20th	Night	10% 12% 5% 13% 5% 5% 4 4 6% 7% 28%	5337
	21st to end	Night	19% 12% 5% 10% 5% 4 4 3 5% 5% 27%	5124
April	1st to 10th	Night	19% 13% 5% 10% 4 3 3 3 5% 5% 30%	2100
	11th to 20th	Night	22% 11% 4 7% 4 3 3 3 5% 6% 34%	2075
	21st to end	Night	17% 9% 3 8% 5% 4 5% 3 5% 6% 35%	1948
May	1st to 10th	Night	14% 9% 3 6% 4 4 3 3 5% 7% 45%	3612
	11th to 20th	Night	10% 8% 3 8% 5% 4 4 4 5% 6% 44%	3596
	21st to end	Night	14% 8% 3 8% 5% 4 5% 4 4 6% 40%	3942
June	1st to 10th	Night	11% 8% 3 5% 5% 4 4 4 5% 7% 45%	1600
	11th to 20th	Night	14% 8% 3 7% 5% 5% 4 3 5% 7% 38%	1600
	21st to end	Night	14% 6% 2 4 5% 5% 5% 4 6% 10% 40%	1600
July	1st to 10th	Night	13% 5% 2 5% 4 4 4 3 6% 9% 47%	3618
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 8% 52%	3617
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 5% 7% 50%	3947
August	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 42%	2597
	11th to 20th	Night	13% 6% 2 5% 3 3 4 2 5% 6% 50%	2877
	21st to end	Night	15% 9% 3 6% 3 3 3 3 4 6% 45%	3586
September	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 5% 7% 49%	2000
	11th to 20th	Night	11% 7% 2 5% 4 5% 4 4 5% 7% 47%	2040
	21st to end	Night	15% 10% 3 7% 4 4 5% 3 5% 7% 39%	2200
October	1st to 10th	Night	15% 7% 3 6% 5% 3 4 4 5% 6% 42%	2370
	11th to 20th	Night	17% 13% 5% 7% 5% 4 5% 4 5% 6% 30%	2424
	21st to end	Night	18% 14% 3 9% 5% 5% 4 3 6% 6% 25%	2860
November	1st to 10th	Night	16% 13% 4 7% 4 4 4 3 6% 7% 32%	2666
	11th to 20th	Night	14% 16% 6% 12% 6% 4 4 3 4 5% 25%	2861
	21st to end	Night	14% 15% 7% 15% 7% 5% 4 4 5% 5% 20%	2940
December	1st to 10th	Night	11% 14% 8% 19% 11% 6% 4 4 5% 5% 14%	4720
	11th to 20th	Night	9% 18% 9% 16% 8% 5% 5% 3 4 4 17%	5339
	21st to end	Night	22% 19% 5% 12% 6% 5% 4 3 4 5% 15%	7150

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	70% 3 9% 13% 5%	4692
	11th to 20th	Day	74% 4 7% 10% 5%	4710
	21st to end	Day	60% 3 8% 18% 10%	5156
February	1st to 10th	Day	56% 5% 10% 18% 10%	1864
	11th to 20th	Day	56% 4 11% 21% 7%	1927
	21st to end	Day	61% 5% 10% 15% 9% 1	1730
March	1st to 10th	Day	47% 3 14% 19% 15% 2	4580
	11th to 20th	Day	55% 4 12% 17% 10% 1	4873
	21st to end	Day	64% 3 9% 13% 11%	6049
April	1st to 10th	Day	58% 6% 10% 17% 10% 1	2520
	11th to 20th	Day	58% 4 8% 21% 8% 1	2494
	21st to end	Day	54% 5% 10% 18% 12% 1	2670
May	1st to 10th	Day	41% 4 9% 27% 17% 2	6361
	11th to 20th	Day	45% 5% 10% 26% 11% 3	6323
	21st to end	Day	49% 6% 9% 20% 16% 1	6949
June	1st to 10th	Day	41% 6% 14% 26% 12% 1	2800
	11th to 20th	Day	47% 6% 13% 21% 13% 1	2800
	21st to end	Day	42% 8% 16% 24% 10% 1	2800
July	1st to 10th	Day	39% 6% 14% 32% 8% 1	6291
	11th to 20th	Day	31% 6% 18% 32% 12% 1	6285
	21st to end	Day	36% 6% 13% 29% 16%	6728
August	1st to 10th	Day	43% 6% 15% 23% 12% 1	4548
	11th to 20th	Day	36% 6% 14% 32% 11%	4204
	21st to end	Day	43% 6% 15% 25% 10% 1	4311
September	1st to 10th	Day	42% 5% 14% 28% 12%	2400
	11th to 20th	Day	43% 6% 19% 25% 7%	2340
	21st to end	Day	48% 5% 12% 26% 10%	2200
October	1st to 10th	Day	36% 4 13% 30% 18%	3298
	11th to 20th	Day	55% 4 10% 18% 13%	3191
	21st to end	Day	56% 4 16% 20% 4	3180
November	1st to 10th	Day	55% 5% 12% 19% 9% 1	1852
	11th to 20th	Day	66% 4 10% 13% 7%	1756
	21st to end	Day	69% 6% 13% 10% 2 1	1680
December	1st to 10th	Day	77% 4 6% 10% 3	2690
	11th to 20th	Day	72% 4 7% 10% 6%	3085
	21st to end	Day	73% 3 4 12% 7%	4070
January	1st to 10th	Night	72% 3 7% 13% 3	8233
	11th to 20th	Night	73% 4 7% 11% 5%	8280
	21st to end	Night	61% 3 8% 18% 10%	9058
February	1st to 10th	Night	57% 4 8% 19% 10% 1	2751
	11th to 20th	Night	55% 5% 11% 19% 8% 1	2590
	21st to end	Night	59% 4 11% 18% 7% 1	2076
March	1st to 10th	Night	43% 3 17% 20% 15% 2	5493
	11th to 20th	Night	55% 4 14% 19% 8% 1	5337
	21st to end	Night	59% 4 10% 15% 11% 1	5124
April	1st to 10th	Night	56% 5% 8% 16% 14% 1	2100
	11th to 20th	Night	53% 4 9% 20% 12% 2	2075
	21st to end	Night	50% 6% 10% 18% 15% 1	1948
May	1st to 10th	Night	39% 5% 14% 24% 14% 3	3636
	11th to 20th	Night	41% 7% 11% 22% 18% 2	3597
	21st to end	Night	45% 5% 12% 21% 16% 1	3950
June	1st to 10th	Night	38% 8% 14% 27% 13% 1	1600
	11th to 20th	Night	45% 5% 13% 21% 15% 1	1600
	21st to end	Night	38% 7% 16% 28% 10% 1	1600
July	1st to 10th	Night	35% 5% 19% 30% 10% 2	3580
	11th to 20th	Night	30% 5% 17% 34% 12% 1	3572
	21st to end	Night	33% 6% 15% 28% 17% 1	3832
August	1st to 10th	Night	38% 7% 15% 23% 16% 1	2588
	11th to 20th	Night	35% 6% 17% 28% 12% 2	2901
	21st to end	Night	41% 5% 13% 27% 13% 1	3586
September	1st to 10th	Night	35% 6% 14% 32% 13% 1	2000
	11th to 20th	Night	36% 6% 16% 33% 8%	2040
	21st to end	Night	44% 5% 15% 26% 10% 1	2200
October	1st to 10th	Night	34% 4 9% 35% 17% 1	3877
	11th to 20th	Night	44% 4 12% 28% 12%	3947
	21st to end	Night	57% 4 11% 20% 8%	4610
November	1st to 10th	Night	52% 5% 13% 20% 10%	2666
	11th to 20th	Night	61% 5% 12% 14% 7% 1	2861
	21st to end	Night	66% 5% 13% 12% 4 1	2940
December	1st to 10th	Night	71% 5% 11% 11% 2	4720
	11th to 20th	Night	70% 4 7% 12% 6%	5341
	21st to end	Night	72% 4 5% 12% 7%	7150

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% 18% 34% 22% 4 1	330
	11th to 20th	Day	22% 18% 38% 19% 3	330
	21st to end	Day	21% 18% 42% 16% 3	363
February	1st to 10th	Day	18% 27% 39% 12% 3 1	330
	11th to 20th	Day	20% 25% 39% 13% 3	330
	21st to end	Day	25% 23% 44% 7% 1	273
March	1st to 10th	Day	21% 25% 38% 14% 2	330
	11th to 20th	Day	25% 22% 35% 13% 5% 1	330
	21st to end	Day	27% 19% 32% 14% 6% 2	568
April	1st to 10th	Day	30% 17% 31% 17% 4 1	540
	11th to 20th	Day	30% 20% 26% 18% 5% 1	532
	21st to end	Day	28% 17% 28% 19% 6% 1	540
May	1st to 10th	Day	21% 21% 30% 20% 6% 1	698
	11th to 20th	Day	21% 18% 31% 19% 8% 2	725
	21st to end	Day	20% 15% 33% 20% 10% 2	789
June	1st to 10th	Day	16% 17% 33% 23% 8% 4	730
	11th to 20th	Day	18% 14% 35% 22% 7% 2	730
	21st to end	Day	17% 14% 34% 21% 12% 3	730
July	1st to 10th	Day	8% 8% 33% 29% 15% 7%	721
	11th to 20th	Day	12% 12% 31% 25% 15% 5%	718
	21st to end	Day	10% 8% 33% 29% 14% 6%	794
August	1st to 10th	Day	14% 9% 26% 28% 18% 5%	726
	11th to 20th	Day	17% 7% 23% 27% 21% 4	645
	21st to end	Day	18% 10% 27% 23% 16% 6%	583
September	1st to 10th	Day	20% 13% 24% 24% 14% 5%	530
	11th to 20th	Day	15% 9% 30% 32% 12% 3	530
	21st to end	Day	21% 16% 26% 22% 12% 4	530
October	1st to 10th	Day	20% 17% 32% 19% 9% 2	355
	11th to 20th	Day	26% 24% 32% 14% 4	330
	21st to end	Day	33% 22% 32% 11% 2 1	363
November	1st to 10th	Day	26% 18% 37% 15% 3 1	330
	11th to 20th	Day	29% 23% 35% 9% 4 1	330
	21st to end	Day	25% 23% 40% 8% 3	330
December	1st to 10th	Day	19% 20% 44% 12% 5%	330
	11th to 20th	Day	27% 26% 34% 11% 2	330
	21st to end	Day	29% 24% 34% 10% 2 1	363
January	1st to 10th	Night	18% 17% 39% 22% 5%	1050
	11th to 20th	Night	20% 14% 40% 19% 6% 1	1050
	21st to end	Night	18% 12% 40% 23% 6%	1155
February	1st to 10th	Night	15% 17% 38% 23% 6%	1050
	11th to 20th	Night	16% 18% 36% 22% 6%	955
	21st to end	Night	20% 15% 40% 23% 3	692
March	1st to 10th	Night	17% 16% 36% 23% 7% 1	840
	11th to 20th	Night	20% 16% 35% 23% 5%	747
	21st to end	Night	20% 13% 32% 25% 9% 1	693
April	1st to 10th	Night	25% 13% 34% 22% 5% 1	630
	11th to 20th	Night	28% 12% 27% 26% 6%	623
	21st to end	Night	23% 11% 30% 27% 8% 1	630
May	1st to 10th	Night	21% 12% 32% 27% 7% 1	603
	11th to 20th	Night	19% 9% 34% 30% 7% 1	591
	21st to end	Night	16% 7% 29% 36% 12%	650
June	1st to 10th	Night	14% 10% 30% 35% 10% 1	600
	11th to 20th	Night	20% 6% 32% 33% 10%	600
	21st to end	Night	17% 6% 25% 37% 13% 2	600
July	1st to 10th	Night	9% 4 24% 39% 24% 1	585
	11th to 20th	Night	12% 7% 28% 32% 21% 1	582
	21st to end	Night	9% 3 26% 39% 20% 3	657
August	1st to 10th	Night	10% 4 22% 42% 20% 2	597
	11th to 20th	Night	14% 3 20% 35% 26% 3	594
	21st to end	Night	16% 6% 23% 33% 19% 2	660
September	1st to 10th	Night	17% 6% 25% 31% 18% 3	600
	11th to 20th	Night	14% 7% 28% 33% 16% 2	640
	21st to end	Night	19% 10% 27% 30% 13% 1	800
October	1st to 10th	Night	21% 11% 29% 26% 12% 1	800
	11th to 20th	Night	24% 15% 30% 24% 6%	800
	21st to end	Night	26% 11% 31% 24% 8%	880
November	1st to 10th	Night	25% 12% 35% 22% 5%	820
	11th to 20th	Night	21% 19% 34% 20% 5% 1	971
	21st to end	Night	23% 19% 34% 20% 4	1050
December	1st to 10th	Night	22% 15% 38% 19% 6%	1050
	11th to 20th	Night	21% 18% 36% 19% 6% 1	1050
	21st to end	Night	28% 17% 33% 19% 3	1155

Page generated at 2026-04-29 01:21:41. Version ac07

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