Batchawana Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Batchawana Bay 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	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	143988
	Night	14% 13% 5% 10% 6% 4 4 3 5% 6% 29%	138165
Transparency	Day	51% 5% 11% 22% 10% 1	147435
	Night	56% 5% 10% 19% 8% 1	142794
Seeing	Day	22% 14% 31% 22% 9% 2	17972
	Night	22% 11% 29% 27% 10% 1	27280

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	8% 21% 10% 15% 10% 6% 4 3 4 5% 14%	4394
	11th to 20th	Day	8% 18% 7% 18% 7% 5% 5% 3 4 5% 19%	4679
	21st to end	Day	6% 16% 9% 17% 8% 8% 6% 3 4 5% 17%	5156
February	1st to 10th	Day	8% 17% 6% 15% 8% 8% 5% 4 5% 6% 19%	1780
	11th to 20th	Day	11% 16% 7% 13% 8% 6% 5% 3 4 5% 22%	1938
	21st to end	Day	7% 17% 7% 15% 8% 6% 5% 4 4 5% 23%	1730
March	1st to 10th	Day	14% 12% 4 10% 6% 5% 5% 4 5% 6% 30%	4578
	11th to 20th	Day	15% 16% 4 9% 6% 4 4 3 6% 6% 27%	5034
	21st to end	Day	19% 15% 8% 11% 5% 4 3 3 3 4 26%	5695
April	1st to 10th	Day	16% 15% 4 10% 4 4 4 3 5% 6% 29%	2520
	11th to 20th	Day	20% 12% 4 8% 3 4 3 3 5% 6% 33%	2681
	21st to end	Day	17% 11% 4 7% 4 4 5% 4 5% 7% 33%	2730
May	1st to 10th	Day	15% 9% 3 7% 4 4 4 3 5% 6% 41%	7642
	11th to 20th	Day	18% 8% 2 6% 3 4 3 3 4 6% 42%	8020
	21st to end	Day	15% 7% 3 6% 4 4 3 3 4 6% 45%	9710
June	1st to 10th	Day	17% 7% 2 5% 5% 4 5% 4 5% 7% 38%	3150
	11th to 20th	Day	14% 7% 3 7% 4 5% 4 5% 7% 8% 36%	3150
	21st to end	Day	17% 7% 2 5% 4 4 4 4 5% 8% 38%	3150
July	1st to 10th	Day	14% 8% 2 6% 3 4 4 3 6% 8% 43%	8879
	11th to 20th	Day	13% 6% 2 5% 4 4 4 4 5% 8% 44%	8385
	21st to end	Day	15% 7% 2 4 3 3 3 3 5% 8% 47%	8992
August	1st to 10th	Day	9% 6% 2 6% 4 5% 5% 4 7% 10% 43%	4549
	11th to 20th	Day	14% 6% 2 6% 4 3 4 3 5% 8% 44%	4226
	21st to end	Day	18% 6% 2 6% 3 3 3 3 5% 6% 44%	4657
September	1st to 10th	Day	18% 7% 2 7% 4 4 4 4 5% 7% 38%	2350
	11th to 20th	Day	19% 7% 2 6% 3 3 4 3 5% 9% 40%	2200
	21st to end	Day	21% 8% 3 7% 5% 5% 3 3 5% 7% 34%	2200
October	1st to 10th	Day	21% 11% 3 7% 5% 4 4 3 4 5% 33%	2150
	11th to 20th	Day	25% 13% 4 10% 6% 5% 5% 3 4 6% 19%	1898
	21st to end	Day	24% 17% 3 9% 6% 4 5% 2 4 5% 21%	1980
November	1st to 10th	Day	21% 18% 3 8% 5% 5% 5% 3 5% 6% 20%	1852
	11th to 20th	Day	16% 21% 6% 10% 5% 5% 4 4 5% 6% 18%	1761
	21st to end	Day	17% 26% 7% 12% 6% 4 4 3 5% 4 12%	1578
December	1st to 10th	Day	14% 23% 10% 13% 6% 5% 4 3 3 5% 14%	2350
	11th to 20th	Day	16% 18% 8% 16% 7% 5% 4 3 4 5% 13%	2691
	21st to end	Day	24% 24% 6% 11% 4 3 3 2 3 3 17%	3553
January	1st to 10th	Night	11% 17% 8% 16% 9% 5% 4 3 4 5% 19%	8514
	11th to 20th	Night	7% 21% 10% 16% 7% 6% 5% 3 4 5% 15%	8236
	21st to end	Night	6% 13% 9% 19% 9% 7% 7% 4 6% 5% 15%	9058
February	1st to 10th	Night	8% 18% 7% 16% 10% 6% 6% 4 5% 5% 17%	2840
	11th to 20th	Night	10% 14% 7% 15% 8% 5% 6% 4 6% 5% 20%	2566
	21st to end	Night	9% 17% 5% 13% 7% 5% 4 4 5% 6% 23%	2076
March	1st to 10th	Night	15% 12% 4 9% 4 4 3 3 5% 7% 34%	5482
	11th to 20th	Night	15% 14% 6% 9% 5% 4 4 4 5% 6% 28%	5144
	21st to end	Night	18% 13% 5% 10% 6% 4 4 3 4 5% 28%	5510
April	1st to 10th	Night	17% 13% 4 8% 6% 4 5% 3 5% 6% 29%	2100
	11th to 20th	Night	19% 11% 4 7% 4 4 3 3 5% 6% 34%	1888
	21st to end	Night	17% 9% 3 7% 4 4 4 3 6% 7% 35%	1890
May	1st to 10th	Night	14% 8% 3 7% 5% 4 4 3 4 5% 44%	5257
	11th to 20th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	4846
	21st to end	Night	12% 9% 3 7% 4 4 4 3 5% 7% 44%	4496
June	1st to 10th	Night	15% 6% 2 6% 4 4 5% 4 6% 9% 40%	1470
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 6% 7% 39%	1470
	21st to end	Night	15% 7% 3 6% 5% 3 4 4 6% 8% 39%	1470
July	1st to 10th	Night	16% 5% 2 5% 4 5% 5% 4 6% 9% 38%	4110
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 5% 8% 47%	4588
	21st to end	Night	14% 6% 2 6% 4 4 3 3 5% 8% 46%	5118
August	1st to 10th	Night	13% 8% 3 7% 5% 4 4 3 7% 8% 38%	2824
	11th to 20th	Night	12% 7% 2 5% 3 3 4 3 5% 8% 47%	2911
	21st to end	Night	15% 6% 2 5% 3 3 4 3 4 5% 50%	3237
September	1st to 10th	Night	15% 8% 2 5% 4 5% 3 3 4 7% 44%	2030
	11th to 20th	Night	17% 6% 2 5% 3 3 3 4 6% 8% 43%	2200
	21st to end	Night	22% 8% 2 6% 4 3 3 3 4 7% 37%	2200
October	1st to 10th	Night	21% 9% 3 7% 4 3 4 4 4 6% 35%	2249
	11th to 20th	Night	25% 12% 3 7% 5% 5% 4 3 4 6% 24%	2500
	21st to end	Night	23% 15% 3 9% 5% 5% 5% 4 4 5% 22%	2860
November	1st to 10th	Night	20% 16% 4 9% 5% 4 4 3 5% 6% 23%	2666
	11th to 20th	Night	19% 19% 6% 12% 6% 5% 4 3 4 5% 17%	2856
	21st to end	Night	17% 22% 8% 12% 5% 4 4 3 5% 5% 16%	3040
December	1st to 10th	Night	11% 22% 8% 12% 7% 5% 5% 4 5% 5% 16%	5060
	11th to 20th	Night	13% 21% 7% 16% 6% 4 3 2 4 5% 19%	5736
	21st to end	Night	21% 25% 7% 13% 4 3 3 2 3 4 16%	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	73% 5% 5% 11% 3 2	4395
	11th to 20th	Day	67% 5% 6% 12% 9%	4710
	21st to end	Day	69% 6% 5% 12% 8%	5156
February	1st to 10th	Day	66% 6% 10% 11% 7%	1780
	11th to 20th	Day	64% 5% 11% 11% 8% 1	1947
	21st to end	Day	62% 6% 9% 14% 9% 1	1730
March	1st to 10th	Day	53% 6% 12% 12% 14% 3	4580
	11th to 20th	Day	57% 4 13% 15% 9% 1	5034
	21st to end	Day	63% 3 8% 13% 10% 2	5695
April	1st to 10th	Day	55% 5% 9% 18% 11% 1	2520
	11th to 20th	Day	53% 4 10% 21% 11% 1	2681
	21st to end	Day	49% 5% 11% 18% 14% 3	2730
May	1st to 10th	Day	43% 4 8% 27% 16% 2	7651
	11th to 20th	Day	44% 5% 8% 25% 15% 3	8024
	21st to end	Day	41% 4 9% 25% 17% 4	9711
June	1st to 10th	Day	43% 7% 11% 24% 13% 2	3150
	11th to 20th	Day	44% 7% 14% 24% 11% 1	3150
	21st to end	Day	44% 7% 12% 25% 11% 1	3150
July	1st to 10th	Day	41% 3 15% 28% 12% 1	8806
	11th to 20th	Day	39% 3 16% 33% 8%	8308
	21st to end	Day	38% 3 13% 35% 11%	8794
August	1st to 10th	Day	36% 5% 16% 32% 10% 1	4534
	11th to 20th	Day	39% 5% 16% 31% 10%	4265
	21st to end	Day	43% 4 15% 26% 12% 1	4656
September	1st to 10th	Day	44% 8% 14% 23% 11%	2350
	11th to 20th	Day	42% 7% 18% 28% 6%	2200
	21st to end	Day	49% 6% 15% 22% 7% 1	2200
October	1st to 10th	Day	43% 4 15% 25% 13%	3501
	11th to 20th	Day	56% 4 13% 25% 2	3062
	21st to end	Day	66% 4 11% 13% 6%	3180
November	1st to 10th	Day	64% 8% 10% 14% 4	1852
	11th to 20th	Day	66% 7% 13% 10% 4	1761
	21st to end	Day	76% 9% 7% 6% 3	1578
December	1st to 10th	Day	76% 4 9% 9% 3	2350
	11th to 20th	Day	75% 5% 9% 8% 4	2691
	21st to end	Day	74% 3 7% 10% 6%	3553
January	1st to 10th	Night	69% 4 5% 13% 6% 2	8514
	11th to 20th	Night	71% 5% 6% 10% 7%	8280
	21st to end	Night	70% 6% 6% 11% 7% 1	9058
February	1st to 10th	Night	68% 7% 8% 10% 5% 1	2840
	11th to 20th	Night	65% 6% 11% 13% 5% 1	2568
	21st to end	Night	61% 7% 10% 15% 8%	2076
March	1st to 10th	Night	50% 5% 14% 16% 13% 3	5493
	11th to 20th	Night	56% 4 15% 17% 7% 1	5145
	21st to end	Night	59% 4 8% 15% 11% 1	5510
April	1st to 10th	Night	54% 6% 10% 17% 11% 1	2100
	11th to 20th	Night	51% 5% 9% 22% 12% 2	1888
	21st to end	Night	48% 5% 11% 18% 15% 3	1890
May	1st to 10th	Night	42% 4 8% 27% 16% 3	5264
	11th to 20th	Night	43% 6% 9% 28% 11% 3	4847
	21st to end	Night	41% 4 9% 25% 15% 5%	4497
June	1st to 10th	Night	40% 7% 10% 23% 18% 1	1470
	11th to 20th	Night	44% 7% 10% 23% 13% 2	1470
	21st to end	Night	43% 8% 13% 25% 10% 1	1470
July	1st to 10th	Night	44% 4 13% 25% 13% 1	4075
	11th to 20th	Night	37% 3 15% 37% 8%	4543
	21st to end	Night	39% 4 13% 32% 10% 1	5002
August	1st to 10th	Night	43% 5% 13% 27% 11%	2815
	11th to 20th	Night	37% 6% 15% 32% 10%	2938
	21st to end	Night	38% 4 11% 32% 14% 1	3237
September	1st to 10th	Night	41% 7% 14% 27% 10% 1	2030
	11th to 20th	Night	39% 9% 17% 28% 7% 1	2200
	21st to end	Night	48% 7% 14% 23% 8%	2200
October	1st to 10th	Night	42% 5% 12% 30% 11%	3678
	11th to 20th	Night	48% 5% 14% 28% 5%	4062
	21st to end	Night	63% 6% 16% 12% 3	4610
November	1st to 10th	Night	62% 7% 10% 16% 5%	2666
	11th to 20th	Night	70% 7% 10% 10% 4	2856
	21st to end	Night	70% 9% 11% 8% 2	3040
December	1st to 10th	Night	71% 5% 13% 9% 2	5060
	11th to 20th	Night	70% 4 9% 10% 6% 1	5735
	21st to end	Night	75% 4 5% 11% 4	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	22% 18% 39% 14% 7% 1	275
	11th to 20th	Day	19% 18% 35% 21% 6% 1	330
	21st to end	Day	15% 15% 39% 25% 6%	363
February	1st to 10th	Day	22% 21% 37% 14% 5% 1	330
	11th to 20th	Day	20% 24% 36% 15% 4 1	330
	21st to end	Day	24% 27% 36% 10% 3	273
March	1st to 10th	Day	24% 22% 38% 13% 3	330
	11th to 20th	Day	24% 18% 33% 18% 6% 1	510
	21st to end	Day	27% 18% 29% 18% 7% 1	594
April	1st to 10th	Day	24% 16% 33% 20% 5% 1	540
	11th to 20th	Day	27% 15% 28% 19% 9% 2	532
	21st to end	Day	24% 16% 30% 18% 9% 3	540
May	1st to 10th	Day	20% 16% 31% 21% 8% 3	543
	11th to 20th	Day	20% 15% 34% 20% 8% 3	701
	21st to end	Day	18% 13% 35% 23% 9% 2	844
June	1st to 10th	Day	19% 12% 33% 26% 8% 2	780
	11th to 20th	Day	19% 14% 34% 25% 7% 2	780
	21st to end	Day	22% 10% 29% 26% 10% 2	780
July	1st to 10th	Day	13% 9% 36% 27% 13% 2	771
	11th to 20th	Day	15% 10% 31% 27% 13% 4	768
	21st to end	Day	19% 6% 30% 30% 13% 3	849
August	1st to 10th	Day	14% 8% 29% 30% 16% 3	687
	11th to 20th	Day	18% 8% 20% 30% 20% 5%	535
	21st to end	Day	23% 11% 23% 27% 13% 4	583
September	1st to 10th	Day	23% 12% 25% 21% 13% 5%	530
	11th to 20th	Day	20% 10% 22% 28% 16% 3	530
	21st to end	Day	24% 12% 23% 26% 13% 2	530
October	1st to 10th	Day	27% 15% 24% 21% 10% 2	530
	11th to 20th	Day	30% 19% 33% 17% 2	428
	21st to end	Day	33% 17% 33% 13% 4	363
November	1st to 10th	Day	33% 18% 30% 15% 4	330
	11th to 20th	Day	32% 22% 31% 10% 4	261
	21st to end	Day	28% 24% 31% 14% 3	220
December	1st to 10th	Day	25% 21% 31% 14% 8% 1	220
	11th to 20th	Day	27% 25% 32% 12% 4	220
	21st to end	Day	35% 23% 25% 13% 3 1	242
January	1st to 10th	Night	23% 14% 35% 23% 5%	1050
	11th to 20th	Night	21% 14% 34% 24% 6% 1	1050
	21st to end	Night	20% 11% 34% 26% 7% 1	1155
February	1st to 10th	Night	18% 17% 34% 26% 5% 1	950
	11th to 20th	Night	18% 14% 36% 23% 8% 1	823
	21st to end	Night	20% 12% 36% 28% 4	692
March	1st to 10th	Night	18% 11% 37% 25% 8% 1	840
	11th to 20th	Night	20% 13% 36% 23% 7% 1	840
	21st to end	Night	17% 10% 35% 29% 8% 1	897
April	1st to 10th	Night	25% 9% 30% 28% 7% 1	630
	11th to 20th	Night	26% 10% 24% 29% 10% 1	623
	21st to end	Night	20% 8% 29% 30% 13%	630
May	1st to 10th	Night	18% 6% 27% 37% 11% 1	630
	11th to 20th	Night	21% 8% 25% 29% 14% 2	621
	21st to end	Night	15% 8% 27% 39% 12%	460
June	1st to 10th	Night	18% 6% 25% 38% 13%	420
	11th to 20th	Night	18% 8% 23% 37% 13% 1	420
	21st to end	Night	17% 5% 24% 35% 17% 2	420
July	1st to 10th	Night	13% 3 21% 44% 17% 1	410
	11th to 20th	Night	16% 3 18% 40% 21% 2	571
	21st to end	Night	19% 4 19% 36% 20% 2	690
August	1st to 10th	Night	15% 4 23% 32% 24% 2	627
	11th to 20th	Night	13% 4 17% 36% 25% 4	606
	21st to end	Night	20% 5% 21% 32% 20% 2	660
September	1st to 10th	Night	19% 5% 25% 30% 16% 4	630
	11th to 20th	Night	19% 6% 25% 31% 15% 4	800
	21st to end	Night	27% 7% 20% 29% 14% 2	800
October	1st to 10th	Night	26% 10% 28% 25% 12% 1	800
	11th to 20th	Night	34% 11% 28% 21% 6%	800
	21st to end	Night	32% 12% 27% 25% 5%	880
November	1st to 10th	Night	31% 15% 30% 20% 5%	820
	11th to 20th	Night	30% 16% 31% 17% 5%	840
	21st to end	Night	26% 18% 34% 19% 3	940
December	1st to 10th	Night	25% 17% 33% 18% 6%	1050
	11th to 20th	Night	27% 17% 35% 15% 4 2	1050
	21st to end	Night	31% 14% 31% 19% 4	1155

Page generated at 2026-08-12 03:37:20. Version ac07

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