Bonaventure
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonaventure clear sky chart from 2005-11-06 to 2025-03-12.

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% 9% 3 7% 5% 5% 5% 4 6% 7% 33%	108480
	Night	17% 10% 4 8% 5% 5% 5% 4 5% 6% 32%	110655
Transparency	Day	47% 6% 15% 21% 10% 1	111998
	Night	52% 5% 13% 20% 9% 1	115303
Seeing	Day	22% 10% 26% 26% 13% 3	16837
	Night	23% 11% 26% 28% 10% 1	24656

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	16% 17% 5% 9% 6% 5% 4 4 3 6% 25%	3157
	11th to 20th	Day	11% 13% 6% 11% 8% 6% 6% 5% 7% 6% 21%	3134
	21st to end	Day	5% 6% 3 7% 5% 5% 7% 7% 9% 9% 37%	4150
February	1st to 10th	Day	10% 12% 4 6% 6% 6% 6% 5% 6% 8% 32%	1800
	11th to 20th	Day	11% 14% 5% 8% 5% 6% 5% 4 5% 6% 30%	1753
	21st to end	Day	9% 13% 3 6% 5% 5% 5% 5% 7% 7% 35%	1510
March	1st to 10th	Day	14% 12% 3 6% 4 5% 5% 4 6% 8% 33%	3432
	11th to 20th	Day	16% 15% 4 10% 6% 6% 5% 3 4 5% 25%	3491
	21st to end	Day	22% 12% 3 6% 5% 5% 5% 3 5% 5% 29%	3816
April	1st to 10th	Day	19% 10% 2 8% 4 5% 6% 3 5% 7% 31%	2265
	11th to 20th	Day	18% 9% 2 6% 4 4 4 4 6% 7% 36%	2442
	21st to end	Day	22% 9% 3 8% 5% 4 5% 4 5% 6% 30%	2470
May	1st to 10th	Day	18% 12% 4 8% 5% 5% 5% 5% 6% 7% 25%	4263
	11th to 20th	Day	17% 7% 3 8% 5% 5% 5% 4 5% 7% 34%	4398
	21st to end	Day	21% 8% 3 8% 5% 5% 5% 4 6% 7% 29%	5109
June	1st to 10th	Day	23% 9% 3 7% 5% 3 4 3 5% 7% 32%	2850
	11th to 20th	Day	17% 7% 2 6% 5% 4 4 4 6% 8% 37%	2850
	21st to end	Day	21% 10% 3 6% 5% 4 4 4 5% 7% 31%	2850
July	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 9% 36%	4760
	11th to 20th	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 37%	4760
	21st to end	Day	13% 5% 2 4 3 4 4 3 6% 9% 46%	4988
August	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 4 5% 8% 39%	4105
	11th to 20th	Day	15% 5% 2 7% 5% 5% 5% 5% 7% 7% 38%	4045
	21st to end	Day	14% 5% 2 5% 4 4 4 4 6% 8% 46%	4532
September	1st to 10th	Day	16% 7% 2 6% 4 5% 4 4 6% 7% 41%	2281
	11th to 20th	Day	17% 6% 2 6% 4 4 3 3 4 6% 46%	2142
	21st to end	Day	17% 8% 3 6% 4 3 4 4 6% 7% 38%	2076
October	1st to 10th	Day	15% 7% 3 7% 5% 5% 4 3 6% 5% 40%	1900
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 5% 7% 31%	1900
	21st to end	Day	23% 8% 2 7% 4 4 4 4 6% 7% 31%	1967
November	1st to 10th	Day	20% 7% 2 6% 5% 5% 6% 4 5% 6% 32%	1567
	11th to 20th	Day	21% 10% 4 8% 4 5% 4 4 7% 6% 27%	1600
	21st to end	Day	20% 15% 4 9% 5% 5% 4 3 5% 7% 24%	1600
December	1st to 10th	Day	16% 12% 5% 9% 6% 6% 5% 5% 7% 6% 22%	2423
	11th to 20th	Day	21% 10% 3 9% 6% 5% 5% 3 5% 6% 27%	2618
	21st to end	Day	14% 14% 4 9% 5% 4 4 3 4 5% 33%	3476
January	1st to 10th	Night	13% 16% 5% 12% 6% 5% 5% 4 6% 7% 20%	6808
	11th to 20th	Night	15% 12% 5% 11% 8% 5% 5% 4 5% 5% 24%	6771
	21st to end	Night	5% 9% 4 9% 5% 5% 6% 6% 7% 9% 36%	6789
February	1st to 10th	Night	9% 13% 4 8% 6% 5% 5% 5% 7% 7% 31%	2600
	11th to 20th	Night	14% 13% 3 8% 6% 6% 4 4 6% 6% 30%	2533
	21st to end	Night	13% 12% 4 7% 5% 5% 5% 4 6% 6% 34%	2118
March	1st to 10th	Night	13% 12% 4 8% 5% 6% 7% 4 5% 7% 31%	3627
	11th to 20th	Night	23% 15% 4 10% 6% 6% 5% 4 4 5% 19%	3497
	21st to end	Night	26% 12% 3 6% 4 3 3 3 4 7% 27%	3816
April	1st to 10th	Night	22% 11% 3 7% 5% 4 4 3 5% 5% 30%	1913
	11th to 20th	Night	20% 9% 3 6% 5% 4 4 3 5% 6% 35%	1688
	21st to end	Night	24% 8% 4 6% 4 4 4 4 4 6% 34%	1710
May	1st to 10th	Night	21% 9% 3 10% 5% 5% 5% 4 4 6% 29%	2680
	11th to 20th	Night	14% 8% 3 7% 5% 4 5% 4 6% 8% 38%	2506
	21st to end	Night	17% 10% 4 8% 6% 5% 5% 4 7% 7% 28%	2505
June	1st to 10th	Night	24% 8% 3 6% 4 3 4 4 5% 7% 31%	1330
	11th to 20th	Night	20% 6% 2 6% 5% 5% 5% 4 6% 7% 35%	1330
	21st to end	Night	25% 6% 3 7% 4 5% 4 4 6% 6% 30%	1330
July	1st to 10th	Night	15% 7% 2 7% 5% 4 4 3 6% 7% 40%	2210
	11th to 20th	Night	15% 7% 3 6% 5% 5% 5% 4 7% 6% 37%	2210
	21st to end	Night	13% 6% 2 5% 3 4 4 4 6% 8% 44%	2541
August	1st to 10th	Night	16% 7% 3 8% 5% 6% 5% 5% 6% 7% 33%	2825
	11th to 20th	Night	15% 6% 2 8% 5% 5% 6% 4 5% 8% 36%	2782
	21st to end	Night	16% 5% 2 4 4 4 4 3 5% 7% 47%	3124
September	1st to 10th	Night	17% 6% 1 5% 3 4 4 4 5% 6% 44%	1898
	11th to 20th	Night	16% 6% 2 5% 2 4 4 3 4 6% 47%	2037
	21st to end	Night	20% 4 2 5% 4 3 3 4 5% 6% 46%	2104
October	1st to 10th	Night	19% 8% 2 7% 3 4 3 3 4 6% 41%	2280
	11th to 20th	Night	21% 8% 3 7% 4 4 5% 4 5% 6% 34%	2280
	21st to end	Night	23% 7% 2 6% 5% 4 5% 4 5% 7% 33%	2628
November	1st to 10th	Night	21% 8% 3 6% 5% 4 6% 4 5% 5% 34%	2729
	11th to 20th	Night	20% 11% 4 8% 5% 5% 5% 4 5% 5% 28%	2800
	21st to end	Night	21% 12% 4 8% 5% 5% 5% 4 5% 6% 24%	2800
December	1st to 10th	Night	13% 12% 5% 10% 6% 6% 5% 4 7% 6% 26%	4763
	11th to 20th	Night	22% 11% 3 8% 5% 4 4 3 5% 6% 27%	5591
	21st to end	Night	16% 15% 5% 9% 4 4 4 3 5% 5% 30%	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	63% 4 12% 13% 8%	3158
	11th to 20th	Day	57% 12% 12% 14% 6%	3160
	21st to end	Day	39% 7% 19% 22% 13%	4150
February	1st to 10th	Day	48% 5% 12% 21% 12% 2	1800
	11th to 20th	Day	53% 5% 11% 20% 11% 1	1761
	21st to end	Day	44% 6% 9% 26% 12% 2	1510
March	1st to 10th	Day	49% 4 17% 20% 10% 1	3436
	11th to 20th	Day	59% 5% 10% 17% 8% 1	3491
	21st to end	Day	54% 5% 7% 20% 12% 2	3816
April	1st to 10th	Day	50% 5% 9% 19% 15% 2	2265
	11th to 20th	Day	44% 6% 10% 25% 14% 1	2442
	21st to end	Day	52% 4 10% 18% 13% 3	2470
May	1st to 10th	Day	53% 6% 12% 20% 8% 1	4277
	11th to 20th	Day	47% 5% 17% 21% 9% 1	4402
	21st to end	Day	49% 8% 12% 20% 10% 1	5109
June	1st to 10th	Day	50% 5% 13% 20% 11% 1	2850
	11th to 20th	Day	44% 6% 14% 23% 12% 2	2850
	21st to end	Day	51% 6% 15% 19% 8%	2850
July	1st to 10th	Day	42% 6% 19% 24% 10%	4685
	11th to 20th	Day	40% 6% 20% 25% 7%	4679
	21st to end	Day	34% 6% 25% 25% 10%	4829
August	1st to 10th	Day	43% 5% 19% 23% 10%	4092
	11th to 20th	Day	43% 7% 21% 23% 6% 1	4084
	21st to end	Day	35% 5% 20% 25% 15%	4532
September	1st to 10th	Day	41% 6% 15% 27% 11%	2281
	11th to 20th	Day	39% 4 16% 27% 13%	2142
	21st to end	Day	43% 6% 12% 27% 11%	2076
October	1st to 10th	Day	42% 6% 17% 27% 8% 1	3160
	11th to 20th	Day	50% 5% 14% 23% 7%	3140
	21st to end	Day	43% 5% 19% 21% 12%	3217
November	1st to 10th	Day	50% 6% 14% 21% 8% 1	1567
	11th to 20th	Day	55% 6% 14% 18% 7% 1	1600
	21st to end	Day	61% 5% 13% 16% 5%	1600
December	1st to 10th	Day	60% 7% 14% 16% 3	2423
	11th to 20th	Day	60% 4 11% 17% 7% 1	2618
	21st to end	Day	55% 4 13% 19% 7% 2	3476
January	1st to 10th	Night	63% 5% 14% 15% 3	6808
	11th to 20th	Night	57% 11% 12% 14% 6%	6820
	21st to end	Night	43% 5% 18% 20% 13% 1	6789
February	1st to 10th	Night	50% 4 11% 19% 13% 3	2600
	11th to 20th	Night	55% 4 9% 20% 11% 1	2536
	21st to end	Night	50% 4 10% 20% 13% 2	2118
March	1st to 10th	Night	54% 3 10% 21% 10% 1	3636
	11th to 20th	Night	65% 7% 6% 14% 8% 1	3498
	21st to end	Night	57% 4 8% 17% 12% 2	3816
April	1st to 10th	Night	56% 4 8% 15% 15% 2	1913
	11th to 20th	Night	49% 4 8% 21% 15% 2	1688
	21st to end	Night	52% 4 9% 17% 16% 2	1710
May	1st to 10th	Night	56% 4 11% 17% 11% 1	2686
	11th to 20th	Night	44% 5% 16% 27% 7% 1	2507
	21st to end	Night	48% 10% 12% 20% 9% 1	2506
June	1st to 10th	Night	52% 5% 11% 21% 12%	1330
	11th to 20th	Night	46% 6% 12% 21% 12% 2	1330
	21st to end	Night	54% 7% 13% 18% 8% 1	1330
July	1st to 10th	Night	44% 5% 17% 22% 10%	2175
	11th to 20th	Night	45% 5% 17% 27% 5%	2168
	21st to end	Night	38% 8% 23% 21% 10%	2461
August	1st to 10th	Night	50% 5% 17% 21% 6%	2813
	11th to 20th	Night	44% 7% 21% 22% 6%	2809
	21st to end	Night	38% 6% 18% 23% 16%	3124
September	1st to 10th	Night	41% 4 15% 30% 10% 1	1898
	11th to 20th	Night	38% 5% 14% 30% 12% 1	2037
	21st to end	Night	40% 5% 12% 29% 14% 1	2104
October	1st to 10th	Night	48% 5% 12% 27% 8% 1	3800
	11th to 20th	Night	44% 5% 14% 29% 8%	3779
	21st to end	Night	44% 4 20% 22% 10%	4328
November	1st to 10th	Night	51% 5% 15% 20% 8% 1	2729
	11th to 20th	Night	58% 5% 13% 17% 6% 1	2800
	21st to end	Night	62% 6% 13% 14% 5%	2800
December	1st to 10th	Night	57% 6% 15% 18% 3	4763
	11th to 20th	Night	58% 5% 11% 20% 6%	5592
	21st to end	Night	57% 5% 12% 18% 7% 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	30% 17% 28% 16% 8% 1	200
	11th to 20th	Day	27% 21% 21% 18% 11% 3	200
	21st to end	Day	14% 15% 34% 26% 11% 1	310
February	1st to 10th	Day	19% 17% 30% 23% 7% 5%	400
	11th to 20th	Day	19% 20% 31% 22% 6% 1	396
	21st to end	Day	16% 16% 32% 25% 9% 2	344
March	1st to 10th	Day	25% 10% 30% 26% 8% 2	500
	11th to 20th	Day	20% 13% 27% 27% 11% 2	464
	21st to end	Day	25% 13% 28% 21% 9% 3	506
April	1st to 10th	Day	27% 15% 28% 23% 6% 2	460
	11th to 20th	Day	25% 9% 28% 26% 10% 3	452
	21st to end	Day	27% 12% 27% 23% 8% 4	460
May	1st to 10th	Day	26% 9% 26% 25% 10% 4	555
	11th to 20th	Day	24% 8% 24% 22% 18% 4	674
	21st to end	Day	23% 9% 29% 25% 10% 3	735
June	1st to 10th	Day	27% 6% 25% 27% 13% 2	680
	11th to 20th	Day	22% 7% 26% 28% 15% 3	680
	21st to end	Day	25% 7% 22% 28% 17% 3	680
July	1st to 10th	Day	17% 7% 26% 30% 16% 4	670
	11th to 20th	Day	15% 5% 23% 35% 21% 2	668
	21st to end	Day	19% 4 18% 32% 22% 5%	721
August	1st to 10th	Day	15% 4 25% 29% 22% 5%	486
	11th to 20th	Day	19% 5% 20% 32% 19% 6%	479
	21st to end	Day	15% 6% 21% 31% 21% 7%	539
September	1st to 10th	Day	17% 7% 29% 26% 16% 5%	490
	11th to 20th	Day	22% 10% 25% 26% 13% 6%	490
	21st to end	Day	20% 12% 23% 25% 14% 5%	483
October	1st to 10th	Day	17% 12% 26% 25% 16% 4	390
	11th to 20th	Day	25% 14% 27% 18% 12% 3	390
	21st to end	Day	27% 16% 26% 19% 9% 2	429
November	1st to 10th	Day	25% 15% 28% 24% 7% 1	395
	11th to 20th	Day	31% 14% 23% 24% 8% 1	400
	21st to end	Day	29% 18% 27% 19% 6% 1	400
December	1st to 10th	Day	29% 9% 27% 25% 8% 1	291
	11th to 20th	Day	24% 22% 31% 19% 4 1	200
	21st to end	Day	25% 18% 27% 23% 6%	220
January	1st to 10th	Night	22% 15% 31% 25% 7% 1	900
	11th to 20th	Night	22% 15% 31% 24% 8%	900
	21st to end	Night	16% 17% 33% 25% 8% 1	881
February	1st to 10th	Night	16% 15% 34% 26% 8% 1	800
	11th to 20th	Night	23% 16% 31% 23% 5% 2	783
	21st to end	Night	20% 11% 31% 28% 9% 1	660
March	1st to 10th	Night	21% 11% 31% 30% 8%	800
	11th to 20th	Night	21% 11% 29% 28% 10% 1	767
	21st to end	Night	23% 11% 26% 31% 9% 1	836
April	1st to 10th	Night	31% 8% 25% 29% 7%	613
	11th to 20th	Night	26% 5% 29% 28% 11% 1	564
	21st to end	Night	30% 8% 22% 31% 8% 2	570
May	1st to 10th	Night	27% 6% 25% 29% 12% 1	570
	11th to 20th	Night	22% 5% 27% 29% 15% 2	562
	21st to end	Night	20% 7% 32% 32% 8% 1	476
June	1st to 10th	Night	27% 4 19% 38% 10% 1	380
	11th to 20th	Night	22% 3 17% 37% 19% 1	380
	21st to end	Night	28% 4 16% 38% 12% 1	380
July	1st to 10th	Night	19% 3 20% 39% 17% 2	370
	11th to 20th	Night	18% 2 17% 47% 13% 2	368
	21st to end	Night	17% 4 17% 38% 23% 2	478
August	1st to 10th	Night	16% 4 18% 43% 19% 1	568
	11th to 20th	Night	17% 4 14% 41% 22% 2	562
	21st to end	Night	15% 5% 19% 36% 22% 3	627
September	1st to 10th	Night	19% 6% 26% 31% 15% 1	570
	11th to 20th	Night	19% 7% 20% 36% 16% 1	707
	21st to end	Night	20% 9% 22% 33% 15% 1	760
October	1st to 10th	Night	24% 7% 28% 27% 13% 1	760
	11th to 20th	Night	26% 10% 26% 25% 12% 1	760
	21st to end	Night	28% 12% 26% 25% 9%	836
November	1st to 10th	Night	26% 13% 28% 26% 6% 1	878
	11th to 20th	Night	27% 16% 27% 21% 7% 2	900
	21st to end	Night	28% 17% 27% 21% 6% 1	900
December	1st to 10th	Night	27% 12% 31% 22% 7% 1	900
	11th to 20th	Night	28% 20% 31% 15% 5% 1	900
	21st to end	Night	28% 15% 28% 23% 4 1	990

Page generated at 2025-03-09 08:08:46. Version ac07

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