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 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	16% 12% 4 9% 5% 4 4 3 5% 6% 32%	112902
	Night	15% 14% 5% 11% 6% 4 4 3 5% 6% 28%	115529
Transparency	Day	52% 6% 11% 20% 10% 1	116396
	Night	57% 6% 11% 17% 8% 1	120186
Seeing	Day	21% 14% 30% 23% 9% 2	16038
	Night	22% 11% 29% 27% 10% 1	25640

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	9% 18% 9% 15% 8% 6% 5% 3 4 6% 18%	3388
	11th to 20th	Day	9% 15% 6% 18% 7% 5% 6% 4 5% 6% 20%	3589
	21st to end	Day	7% 20% 10% 18% 7% 6% 5% 3 5% 5% 14%	3982
February	1st to 10th	Day	8% 17% 6% 15% 9% 8% 5% 4 5% 5% 19%	1695
	11th to 20th	Day	10% 16% 7% 13% 8% 6% 5% 3 4 5% 23%	1843
	21st to end	Day	7% 17% 7% 15% 8% 6% 5% 4 4 5% 22%	1650
March	1st to 10th	Day	14% 12% 4 10% 6% 4 5% 4 5% 6% 30%	4478
	11th to 20th	Day	14% 16% 4 9% 6% 4 4 3 6% 6% 27%	4925
	21st to end	Day	18% 15% 8% 11% 5% 3 3 3 3 4 26%	5572
April	1st to 10th	Day	16% 15% 4 10% 4 4 4 3 5% 6% 30%	2400
	11th to 20th	Day	20% 12% 4 7% 4 4 3 3 5% 6% 33%	2423
	21st to end	Day	17% 11% 4 6% 4 4 4 4 5% 6% 34%	2470
May	1st to 10th	Day	17% 8% 3 7% 4 4 4 3 5% 6% 38%	4108
	11th to 20th	Day	14% 7% 2 7% 4 4 5% 3 6% 7% 42%	4293
	21st to end	Day	20% 7% 2 5% 4 4 3 3 5% 7% 40%	5179
June	1st to 10th	Day	17% 7% 2 5% 5% 4 5% 4 6% 7% 37%	2850
	11th to 20th	Day	14% 7% 3 7% 4 4 4 5% 7% 8% 37%	2850
	21st to end	Day	17% 7% 2 5% 4 4 4 4 5% 8% 39%	2850
July	1st to 10th	Day	18% 9% 3 6% 4 4 3 3 5% 7% 39%	4760
	11th to 20th	Day	12% 7% 2 5% 4 4 5% 4 6% 8% 45%	4489
	21st to end	Day	14% 6% 2 4 4 3 3 3 5% 8% 47%	4814
August	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 4 7% 10% 43%	4277
	11th to 20th	Day	14% 6% 2 6% 4 3 4 3 5% 8% 44%	4044
	21st to end	Day	19% 6% 2 5% 3 3 3 3 4 6% 44%	4514
September	1st to 10th	Day	18% 7% 2 7% 4 4 3 4 5% 7% 39%	2233
	11th to 20th	Day	19% 7% 2 6% 3 3 4 3 5% 9% 39%	2090
	21st to end	Day	21% 8% 3 7% 5% 5% 3 3 5% 7% 34%	2090
October	1st to 10th	Day	22% 11% 3 7% 5% 4 5% 3 4 5% 32%	2043
	11th to 20th	Day	25% 13% 4 11% 6% 5% 4 3 4 6% 19%	1803
	21st to end	Day	25% 17% 3 9% 6% 4 5% 2 5% 6% 19%	1881
November	1st to 10th	Day	22% 18% 3 8% 4 5% 5% 3 5% 6% 20%	1762
	11th to 20th	Day	16% 21% 6% 10% 5% 5% 4 4 5% 6% 18%	1677
	21st to end	Day	17% 26% 7% 12% 6% 4 4 3 5% 5% 13%	1503
December	1st to 10th	Day	14% 24% 10% 12% 6% 5% 4 3 3 5% 14%	2280
	11th to 20th	Day	15% 18% 8% 16% 7% 5% 4 3 4 5% 13%	2621
	21st to end	Day	24% 24% 6% 11% 4 3 3 2 3 3 17%	3476
January	1st to 10th	Night	10% 17% 7% 14% 8% 5% 4 3 4 5% 22%	6561
	11th to 20th	Night	7% 19% 9% 16% 8% 6% 4 3 5% 6% 17%	6316
	21st to end	Night	8% 16% 12% 21% 8% 5% 5% 3 4 4 13%	6996
February	1st to 10th	Night	8% 18% 7% 16% 11% 6% 6% 3 4 5% 16%	2705
	11th to 20th	Night	10% 15% 6% 15% 8% 5% 5% 4 6% 5% 20%	2441
	21st to end	Night	10% 18% 5% 12% 7% 5% 4 4 5% 6% 24%	1980
March	1st to 10th	Night	15% 11% 4 9% 4 4 3 3 5% 7% 34%	5362
	11th to 20th	Night	14% 14% 5% 9% 5% 4 4 4 5% 7% 28%	5033
	21st to end	Night	18% 13% 5% 11% 6% 4 4 3 4 5% 28%	5390
April	1st to 10th	Night	17% 13% 4 8% 6% 4 5% 3 6% 6% 29%	2000
	11th to 20th	Night	18% 11% 4 7% 4 4 3 3 5% 7% 34%	1712
	21st to end	Night	16% 9% 3 7% 4 4 4 3 6% 7% 36%	1710
May	1st to 10th	Night	19% 9% 3 7% 5% 5% 3 3 4 5% 40%	2833
	11th to 20th	Night	14% 8% 2 6% 5% 4 6% 4 6% 6% 38%	2606
	21st to end	Night	17% 9% 3 7% 4 4 4 2 5% 6% 39%	2406
June	1st to 10th	Night	15% 6% 2 6% 4 4 5% 4 6% 9% 39%	1330
	11th to 20th	Night	17% 8% 3 6% 5% 3 4 3 5% 6% 40%	1330
	21st to end	Night	15% 7% 2 6% 5% 3 4 4 6% 7% 39%	1330
July	1st to 10th	Night	17% 6% 2 6% 5% 6% 5% 4 6% 7% 36%	2210
	11th to 20th	Night	11% 6% 3 6% 4 4 4 3 5% 7% 48%	2464
	21st to end	Night	14% 7% 2 7% 4 3 3 3 5% 7% 46%	2750
August	1st to 10th	Night	13% 8% 3 7% 5% 4 4 3 7% 8% 38%	2656
	11th to 20th	Night	12% 7% 2 5% 3 4 4 3 5% 7% 48%	2785
	21st to end	Night	15% 6% 2 5% 3 3 4 3 4 5% 51%	3138
September	1st to 10th	Night	15% 7% 2 5% 4 5% 3 3 5% 7% 44%	1928
	11th to 20th	Night	18% 6% 2 5% 3 3 3 4 6% 8% 42%	2090
	21st to end	Night	22% 8% 2 6% 4 3 3 4 4 7% 37%	2090
October	1st to 10th	Night	22% 10% 3 7% 4 3 4 4 4 6% 34%	2136
	11th to 20th	Night	25% 12% 3 7% 6% 5% 4 3 4 6% 24%	2375
	21st to end	Night	24% 16% 4 9% 5% 5% 4 4 4 5% 22%	2717
November	1st to 10th	Night	20% 16% 4 9% 5% 4 4 3 5% 6% 23%	2536
	11th to 20th	Night	20% 19% 6% 12% 6% 5% 4 3 4 5% 17%	2720
	21st to end	Night	17% 22% 7% 12% 5% 4 4 3 5% 5% 17%	2895
December	1st to 10th	Night	11% 22% 8% 12% 7% 5% 5% 4 5% 5% 16%	4910
	11th to 20th	Night	13% 21% 7% 16% 6% 4 3 2 4 4 19%	5586
	21st to end	Night	21% 25% 7% 13% 4 3 3 2 3 4 16%	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	68% 6% 6% 13% 4 3	3389
	11th to 20th	Day	64% 7% 7% 11% 10%	3620
	21st to end	Day	72% 7% 5% 8% 8%	3982
February	1st to 10th	Day	66% 7% 10% 11% 6%	1695
	11th to 20th	Day	63% 6% 12% 11% 8% 1	1852
	21st to end	Day	62% 6% 10% 13% 8% 1	1650
March	1st to 10th	Day	53% 6% 12% 12% 14% 3	4480
	11th to 20th	Day	57% 5% 13% 15% 9% 1	4925
	21st to end	Day	63% 3 9% 13% 10% 1	5572
April	1st to 10th	Day	54% 6% 10% 18% 11% 1	2400
	11th to 20th	Day	52% 4 9% 21% 11% 1	2423
	21st to end	Day	48% 5% 10% 18% 15% 4	2470
May	1st to 10th	Day	44% 6% 10% 25% 13% 2	4120
	11th to 20th	Day	40% 8% 10% 26% 15% 1	4297
	21st to end	Day	42% 7% 12% 19% 16% 4	5179
June	1st to 10th	Day	43% 8% 12% 23% 12% 2	2850
	11th to 20th	Day	42% 8% 14% 23% 12% 1	2850
	21st to end	Day	43% 8% 13% 24% 12% 1	2850
July	1st to 10th	Day	45% 5% 16% 23% 11% 1	4686
	11th to 20th	Day	37% 5% 15% 32% 11% 1	4412
	21st to end	Day	36% 5% 11% 32% 16%	4662
August	1st to 10th	Day	37% 5% 15% 32% 10%	4262
	11th to 20th	Day	39% 5% 15% 31% 10%	4083
	21st to end	Day	42% 4 15% 26% 12% 1	4513
September	1st to 10th	Day	43% 8% 14% 23% 12%	2233
	11th to 20th	Day	43% 7% 17% 26% 6%	2090
	21st to end	Day	49% 7% 15% 22% 7% 1	2090
October	1st to 10th	Day	43% 4 14% 25% 13%	3394
	11th to 20th	Day	56% 4 13% 25% 2	2967
	21st to end	Day	67% 4 11% 12% 6%	3081
November	1st to 10th	Day	64% 8% 10% 14% 4	1762
	11th to 20th	Day	66% 7% 13% 10% 4	1677
	21st to end	Day	75% 9% 7% 6% 3	1503
December	1st to 10th	Day	76% 4 9% 8% 2	2280
	11th to 20th	Day	75% 5% 9% 8% 3	2621
	21st to end	Day	74% 4 7% 10% 6%	3476
January	1st to 10th	Night	65% 5% 6% 14% 6% 3	6561
	11th to 20th	Night	68% 6% 8% 11% 6%	6360
	21st to end	Night	75% 7% 4 8% 5% 1	6996
February	1st to 10th	Night	69% 7% 8% 10% 5% 1	2705
	11th to 20th	Night	65% 6% 11% 13% 5% 1	2443
	21st to end	Night	60% 7% 10% 15% 8%	1980
March	1st to 10th	Night	50% 5% 14% 16% 13% 2	5373
	11th to 20th	Night	55% 4 16% 17% 7% 1	5034
	21st to end	Night	60% 4 8% 15% 11% 2	5390
April	1st to 10th	Night	54% 6% 11% 17% 12% 1	2000
	11th to 20th	Night	49% 5% 9% 23% 12% 2	1712
	21st to end	Night	47% 6% 11% 18% 15% 3	1710
May	1st to 10th	Night	46% 6% 9% 23% 14% 2	2840
	11th to 20th	Night	42% 10% 11% 26% 10% 1	2607
	21st to end	Night	46% 6% 11% 18% 14% 5%	2407
June	1st to 10th	Night	41% 8% 11% 23% 16% 1	1330
	11th to 20th	Night	43% 8% 10% 22% 14% 2	1330
	21st to end	Night	43% 8% 12% 24% 10% 1	1330
July	1st to 10th	Night	46% 6% 13% 25% 10%	2175
	11th to 20th	Night	36% 4 15% 33% 11% 1	2419
	21st to end	Night	39% 5% 10% 26% 17% 1	2662
August	1st to 10th	Night	44% 5% 12% 27% 11% 1	2647
	11th to 20th	Night	36% 7% 15% 32% 10%	2812
	21st to end	Night	38% 5% 11% 32% 15% 1	3138
September	1st to 10th	Night	40% 7% 13% 27% 11% 1	1928
	11th to 20th	Night	40% 9% 16% 27% 7% 1	2090
	21st to end	Night	48% 7% 14% 22% 8%	2090
October	1st to 10th	Night	43% 5% 12% 29% 11%	3565
	11th to 20th	Night	48% 5% 14% 28% 5%	3937
	21st to end	Night	64% 6% 16% 11% 3	4467
November	1st to 10th	Night	62% 8% 10% 16% 5%	2536
	11th to 20th	Night	70% 7% 10% 10% 4	2720
	21st to end	Night	70% 9% 11% 7% 2	2895
December	1st to 10th	Night	70% 5% 14% 9% 2	4910
	11th to 20th	Night	70% 4 9% 10% 6% 1	5585
	21st to end	Night	75% 4 6% 11% 4	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	20% 17% 40% 15% 7% 1	250
	11th to 20th	Day	19% 17% 36% 21% 7% 1	300
	21st to end	Day	16% 15% 38% 25% 6%	330
February	1st to 10th	Day	22% 21% 37% 14% 5% 1	300
	11th to 20th	Day	19% 25% 36% 16% 3 1	300
	21st to end	Day	24% 27% 37% 9% 3	249
March	1st to 10th	Day	21% 22% 39% 15% 3	300
	11th to 20th	Day	23% 18% 33% 19% 6% 1	471
	21st to end	Day	25% 18% 29% 19% 7% 1	550
April	1st to 10th	Day	23% 16% 34% 22% 5% 1	500
	11th to 20th	Day	26% 16% 27% 20% 10% 2	452
	21st to end	Day	24% 15% 29% 18% 10% 3	460
May	1st to 10th	Day	20% 17% 30% 21% 8% 4	463
	11th to 20th	Day	18% 13% 35% 22% 9% 4	608
	21st to end	Day	18% 13% 33% 25% 9% 3	734
June	1st to 10th	Day	19% 12% 33% 25% 9% 2	680
	11th to 20th	Day	17% 13% 34% 27% 7% 2	680
	21st to end	Day	20% 9% 29% 29% 11% 3	680
July	1st to 10th	Day	13% 9% 34% 28% 13% 2	671
	11th to 20th	Day	15% 9% 29% 29% 14% 4	668
	21st to end	Day	19% 6% 27% 31% 14% 3	739
August	1st to 10th	Day	14% 9% 27% 31% 17% 3	595
	11th to 20th	Day	17% 7% 19% 31% 20% 6%	479
	21st to end	Day	24% 10% 22% 27% 13% 4	539
September	1st to 10th	Day	22% 12% 26% 22% 13% 5%	490
	11th to 20th	Day	20% 11% 23% 29% 14% 3	490
	21st to end	Day	24% 13% 23% 25% 13% 2	490
October	1st to 10th	Day	28% 16% 24% 19% 11% 2	490
	11th to 20th	Day	30% 19% 32% 17% 2	393
	21st to end	Day	34% 18% 33% 12% 3	330
November	1st to 10th	Day	33% 18% 31% 15% 4	300
	11th to 20th	Day	30% 23% 32% 11% 4	237
	21st to end	Day	26% 25% 32% 15% 3	200
December	1st to 10th	Day	27% 19% 31% 14% 9% 1	200
	11th to 20th	Day	26% 25% 32% 13% 4 1	200
	21st to end	Day	35% 23% 24% 14% 3 1	220
January	1st to 10th	Night	23% 14% 35% 23% 5%	1000
	11th to 20th	Night	21% 14% 34% 25% 6% 1	1000
	21st to end	Night	21% 11% 33% 26% 8% 1	1100
February	1st to 10th	Night	18% 17% 34% 26% 5% 1	905
	11th to 20th	Night	18% 14% 37% 22% 8% 1	783
	21st to end	Night	20% 13% 36% 28% 4	660
March	1st to 10th	Night	18% 11% 36% 26% 8% 1	800
	11th to 20th	Night	20% 13% 36% 23% 7% 1	800
	21st to end	Night	17% 10% 34% 30% 8% 1	854
April	1st to 10th	Night	24% 9% 31% 28% 7% 1	600
	11th to 20th	Night	24% 9% 25% 30% 10% 1	565
	21st to end	Night	19% 8% 29% 30% 14%	570
May	1st to 10th	Night	19% 6% 27% 36% 11% 1	570
	11th to 20th	Night	20% 8% 24% 31% 15% 2	561
	21st to end	Night	15% 7% 25% 39% 12%	416
June	1st to 10th	Night	17% 7% 25% 38% 13%	380
	11th to 20th	Night	18% 8% 21% 38% 13% 2	380
	21st to end	Night	17% 5% 23% 35% 18% 2	380
July	1st to 10th	Night	13% 3 22% 44% 16% 2	370
	11th to 20th	Night	16% 3 18% 40% 22% 2	515
	21st to end	Night	19% 3 18% 36% 21% 3	624
August	1st to 10th	Night	14% 4 23% 32% 24% 2	567
	11th to 20th	Night	13% 4 16% 36% 26% 4	564
	21st to end	Night	20% 6% 22% 32% 19% 2	627
September	1st to 10th	Night	18% 5% 26% 31% 16% 4	598
	11th to 20th	Night	20% 7% 26% 30% 14% 3	760
	21st to end	Night	28% 7% 21% 28% 14% 3	760
October	1st to 10th	Night	27% 10% 28% 24% 12% 1	760
	11th to 20th	Night	33% 12% 28% 21% 6%	760
	21st to end	Night	33% 12% 27% 23% 5%	836
November	1st to 10th	Night	31% 14% 30% 20% 6%	780
	11th to 20th	Night	30% 16% 31% 18% 5% 1	800
	21st to end	Night	26% 18% 33% 19% 3	895
December	1st to 10th	Night	25% 16% 33% 19% 7%	1000
	11th to 20th	Night	27% 17% 35% 15% 5% 2	1000
	21st to end	Night	30% 14% 31% 20% 5%	1100

Page generated at 2025-04-08 09:17:26. Version ac07

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