Bonaventure
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonaventure clear sky chart from 2005-11-05 to 2024-10-14.

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% 34%	101563
	Night	17% 10% 3 7% 5% 5% 5% 4 5% 6% 32%	97083
Transparency	Day	47% 6% 15% 22% 10% 1	101307
	Night	51% 6% 13% 20% 9% 1	96966
Seeing	Day	22% 10% 26% 26% 13% 3	16431
	Night	23% 10% 26% 29% 11% 1	23979

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	13% 11% 4 9% 7% 6% 4 4 3 7% 32%	2207
	11th to 20th	Day	13% 12% 4 8% 9% 6% 7% 6% 8% 6% 22%	2210
	21st to end	Day	7% 8% 3 6% 4 4 5% 5% 9% 10% 39%	2892
February	1st to 10th	Day	10% 12% 4 6% 6% 6% 5% 5% 6% 7% 32%	1710
	11th to 20th	Day	11% 14% 5% 9% 5% 6% 5% 4 5% 6% 29%	1663
	21st to end	Day	9% 14% 3 6% 5% 5% 5% 5% 7% 8% 35%	1437
March	1st to 10th	Day	14% 13% 3 6% 4 5% 5% 4 6% 8% 33%	3325
	11th to 20th	Day	16% 15% 4 10% 6% 6% 5% 3 4 5% 25%	3480
	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% 3 5% 7% 31%	1830
	21st to end	Day	23% 9% 3 7% 4 4 5% 3 5% 6% 31%	1864
November	1st to 10th	Day	19% 7% 2 7% 6% 5% 6% 4 5% 6% 33%	1487
	11th to 20th	Day	20% 9% 4 8% 5% 5% 4 4 7% 6% 28%	1520
	21st to end	Day	19% 14% 4 9% 5% 5% 4 3 5% 7% 25%	1520
December	1st to 10th	Day	20% 12% 3 8% 6% 6% 5% 5% 5% 7% 23%	1417
	11th to 20th	Day	18% 14% 4 8% 7% 5% 6% 4 6% 7% 22%	1668
	21st to end	Day	16% 12% 3 9% 5% 4 4 3 4 5% 35%	2431
January	1st to 10th	Night	9% 11% 4 10% 7% 5% 6% 6% 8% 9% 26%	4748
	11th to 20th	Night	17% 11% 4 9% 10% 6% 6% 4 5% 5% 23%	4760
	21st to end	Night	7% 10% 5% 8% 4 4 4 4 7% 8% 37%	4747
February	1st to 10th	Night	9% 14% 4 8% 6% 5% 5% 5% 6% 7% 31%	2470
	11th to 20th	Night	14% 13% 3 9% 7% 6% 4 4 6% 6% 29%	2403
	21st to end	Night	13% 12% 4 7% 5% 5% 5% 4 6% 6% 33%	2016
March	1st to 10th	Night	12% 12% 4 9% 5% 6% 7% 4 5% 7% 31%	3514
	11th to 20th	Night	23% 15% 4 10% 6% 6% 5% 4 4 5% 19%	3479
	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 4 4 6% 6% 34%	2203
	21st to end	Night	23% 7% 3 6% 5% 4 4 4 5% 7% 32%	2489
November	1st to 10th	Night	21% 8% 3 6% 5% 4 6% 4 5% 6% 33%	2589
	11th to 20th	Night	20% 11% 4 8% 5% 4 5% 4 5% 6% 28%	2660
	21st to end	Night	21% 12% 4 8% 5% 5% 6% 4 5% 6% 25%	2660
December	1st to 10th	Night	20% 12% 3 8% 5% 6% 5% 4 7% 5% 24%	2759
	11th to 20th	Night	23% 13% 4 8% 6% 5% 5% 4 6% 5% 22%	3531
	21st to end	Night	16% 14% 4 9% 5% 4 4 4 5% 5% 29%	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	54% 4 12% 18% 11%	2208
	11th to 20th	Day	53% 12% 10% 17% 8%	2210
	21st to end	Day	37% 7% 15% 26% 15% 1	2892
February	1st to 10th	Day	49% 5% 12% 21% 11% 2	1710
	11th to 20th	Day	53% 5% 11% 20% 10% 1	1671
	21st to end	Day	44% 6% 9% 25% 13% 2	1437
March	1st to 10th	Day	48% 4 17% 20% 9% 1	3329
	11th to 20th	Day	59% 5% 10% 17% 8% 1	3480
	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% 16% 25% 10% 1	1900
	11th to 20th	Day	51% 5% 16% 22% 6%	1832
	21st to end	Day	52% 5% 15% 18% 9% 1	1864
November	1st to 10th	Day	50% 6% 14% 20% 9% 1	1487
	11th to 20th	Day	54% 7% 14% 18% 6%	1520
	21st to end	Day	60% 5% 14% 16% 5%	1520
December	1st to 10th	Day	61% 7% 11% 15% 5%	1417
	11th to 20th	Day	64% 4 10% 14% 7%	1668
	21st to end	Day	53% 4 13% 20% 7% 3	2431
January	1st to 10th	Night	54% 5% 17% 20% 4	4748
	11th to 20th	Night	55% 12% 10% 15% 8%	4760
	21st to end	Night	43% 5% 14% 22% 16% 1	4747
February	1st to 10th	Night	51% 4 11% 19% 13% 3	2470
	11th to 20th	Night	55% 4 9% 20% 10% 1	2406
	21st to end	Night	51% 4 10% 20% 14% 2	2016
March	1st to 10th	Night	54% 3 11% 22% 9% 1	3523
	11th to 20th	Night	65% 7% 6% 14% 8% 1	3480
	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	45% 5% 12% 26% 11% 1	2280
	11th to 20th	Night	51% 5% 14% 23% 7%	2206
	21st to end	Night	52% 5% 14% 21% 8%	2489
November	1st to 10th	Night	52% 5% 15% 19% 8% 1	2589
	11th to 20th	Night	57% 5% 13% 18% 6%	2660
	21st to end	Night	61% 6% 14% 14% 5%	2660
December	1st to 10th	Night	62% 5% 11% 17% 5%	2759
	11th to 20th	Night	65% 5% 9% 16% 5%	3532
	21st to end	Night	56% 6% 14% 16% 6% 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	29% 17% 27% 17% 9% 1	180
	11th to 20th	Day	29% 21% 23% 19% 7% 2	180
	21st to end	Day	15% 14% 31% 27% 11% 1	283
February	1st to 10th	Day	20% 16% 29% 23% 7% 5%	370
	11th to 20th	Day	19% 21% 31% 22% 7% 1	366
	21st to end	Day	15% 17% 33% 24% 9% 2	319
March	1st to 10th	Day	23% 10% 30% 26% 8% 2	460
	11th to 20th	Day	20% 12% 27% 28% 11% 2	460
	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% 15% 27% 17% 12% 4	369
	21st to end	Day	29% 17% 24% 18% 9% 3	396
November	1st to 10th	Day	25% 15% 27% 24% 8% 1	365
	11th to 20th	Day	28% 15% 23% 24% 8% 1	370
	21st to end	Day	27% 18% 29% 20% 6% 1	370
December	1st to 10th	Day	30% 9% 27% 26% 7% 1	267
	11th to 20th	Day	24% 22% 29% 19% 4 1	180
	21st to end	Day	25% 20% 28% 22% 5%	198
January	1st to 10th	Night	21% 15% 32% 25% 7% 1	850
	11th to 20th	Night	23% 15% 32% 24% 6%	850
	21st to end	Night	16% 16% 32% 26% 9% 1	837
February	1st to 10th	Night	16% 15% 33% 26% 9% 1	760
	11th to 20th	Night	23% 16% 31% 24% 5% 2	743
	21st to end	Night	21% 11% 31% 28% 9% 1	628
March	1st to 10th	Night	19% 11% 31% 31% 8%	760
	11th to 20th	Night	21% 11% 29% 27% 10% 1	760
	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% 24% 12% 1	735
	21st to end	Night	29% 12% 25% 25% 9%	792
November	1st to 10th	Night	26% 13% 28% 25% 7% 1	828
	11th to 20th	Night	27% 16% 28% 20% 8% 2	850
	21st to end	Night	26% 17% 28% 22% 6% 1	850
December	1st to 10th	Night	28% 12% 30% 22% 8% 1	850
	11th to 20th	Night	28% 20% 31% 15% 5% 1	850
	21st to end	Night	28% 16% 29% 22% 4 1	935

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