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 2026-07-16.

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	17% 9% 3 7% 5% 5% 5% 4 6% 7% 33%	138327
	Night	17% 10% 4 8% 5% 5% 5% 4 5% 6% 31%	134574
Transparency	Day	48% 5% 14% 21% 10% 1	141797
	Night	52% 5% 13% 19% 9% 1	139196
Seeing	Day	22% 11% 26% 26% 13% 3	18754
	Night	23% 11% 27% 29% 10% 1	26311

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	15% 16% 5% 9% 6% 6% 6% 4 4 6% 24%	4093
	11th to 20th	Day	13% 14% 6% 11% 7% 6% 7% 5% 7% 6% 18%	4084
	21st to end	Day	4 8% 4 10% 5% 5% 7% 7% 8% 9% 36%	5383
February	1st to 10th	Day	9% 12% 4 7% 6% 6% 6% 5% 6% 8% 32%	1890
	11th to 20th	Day	11% 14% 5% 9% 5% 6% 5% 3 5% 6% 30%	1843
	21st to end	Day	8% 13% 3 7% 6% 5% 5% 4 7% 7% 35%	1583
March	1st to 10th	Day	17% 12% 3 6% 4 5% 5% 3 6% 7% 31%	4889
	11th to 20th	Day	16% 15% 5% 10% 6% 5% 4 3 4 6% 26%	5090
	21st to end	Day	21% 13% 3 7% 5% 5% 5% 3 4 6% 27%	5587
April	1st to 10th	Day	19% 10% 2 8% 4 4 5% 4 5% 7% 32%	2504
	11th to 20th	Day	19% 9% 2 6% 4 4 4 4 6% 7% 35%	2702
	21st to end	Day	22% 9% 3 7% 5% 4 5% 4 5% 6% 31%	2730
May	1st to 10th	Day	25% 11% 3 7% 4 4 4 4 5% 6% 26%	7934
	11th to 20th	Day	20% 8% 3 7% 5% 4 4 3 5% 7% 34%	8220
	21st to end	Day	23% 8% 3 8% 5% 4 4 3 5% 6% 31%	9570
June	1st to 10th	Day	22% 8% 3 7% 5% 4 4 3 4 7% 33%	3150
	11th to 20th	Day	19% 7% 2 6% 5% 4 4 4 6% 8% 35%	3150
	21st to end	Day	21% 10% 3 6% 5% 5% 5% 4 5% 7% 30%	3150
July	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 5% 8% 10% 35%	6970
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 9% 37%	6895
	21st to end	Day	13% 5% 2 5% 4 4 4 3 6% 8% 48%	7170
August	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 4 5% 8% 40%	4235
	11th to 20th	Day	15% 5% 2 6% 5% 5% 5% 5% 7% 7% 39%	4175
	21st to end	Day	14% 5% 2 5% 4 4 4 4 6% 8% 46%	4675
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 6% 7% 42%	2401
	11th to 20th	Day	16% 6% 2 6% 4 4 4 3 4 6% 46%	2254
	21st to end	Day	16% 7% 3 6% 4 3 4 4 6% 7% 39%	2185
October	1st to 10th	Day	15% 7% 3 7% 5% 5% 4 3 6% 6% 40%	2000
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 5% 7% 31%	2000
	21st to end	Day	23% 8% 2 7% 4 4 4 4 6% 7% 30%	2070
November	1st to 10th	Day	20% 7% 2 7% 6% 5% 6% 4 5% 7% 32%	1647
	11th to 20th	Day	20% 10% 4 9% 4 5% 4 4 7% 6% 27%	1680
	21st to end	Day	20% 15% 4 9% 5% 5% 4 3 5% 7% 24%	1680
December	1st to 10th	Day	15% 12% 5% 9% 6% 6% 5% 5% 6% 6% 23%	2497
	11th to 20th	Day	20% 10% 3 9% 6% 5% 5% 3 5% 6% 26%	2688
	21st to end	Day	14% 14% 4 9% 5% 4 4 3 4 5% 33%	3553
January	1st to 10th	Night	13% 16% 5% 11% 7% 5% 5% 4 6% 6% 22%	8831
	11th to 20th	Night	15% 14% 5% 11% 8% 5% 5% 4 5% 5% 23%	8831
	21st to end	Night	4 9% 5% 10% 5% 5% 6% 6% 7% 8% 35%	8781
February	1st to 10th	Night	8% 13% 4 8% 6% 5% 5% 5% 7% 7% 31%	2730
	11th to 20th	Night	14% 14% 4 8% 6% 5% 4 3 6% 6% 30%	2663
	21st to end	Night	12% 12% 4 7% 5% 4 5% 4 5% 6% 34%	2221
March	1st to 10th	Night	18% 12% 4 7% 5% 5% 6% 3 4 6% 29%	5170
	11th to 20th	Night	22% 13% 4 11% 5% 5% 5% 4 4 5% 22%	5089
	21st to end	Night	25% 14% 3 7% 4 3 3 3 4 6% 27%	5587
April	1st to 10th	Night	22% 11% 3 7% 5% 4 4 4 5% 5% 29%	2113
	11th to 20th	Night	21% 9% 3 6% 5% 4 4 3 5% 6% 34%	1868
	21st to end	Night	23% 8% 3 6% 4 4 4 3 4 6% 33%	1890
May	1st to 10th	Night	24% 9% 3 9% 5% 4 5% 3 4 5% 30%	4977
	11th to 20th	Night	22% 7% 2 6% 4 3 4 4 5% 6% 36%	4670
	21st to end	Night	18% 10% 4 8% 5% 4 4 3 5% 6% 33%	4679
June	1st to 10th	Night	24% 8% 3 6% 4 3 4 4 5% 7% 32%	1470
	11th to 20th	Night	21% 6% 2 6% 5% 4 5% 4 6% 7% 34%	1470
	21st to end	Night	25% 7% 3 7% 4 5% 4 4 6% 6% 29%	1470
July	1st to 10th	Night	17% 7% 3 7% 5% 4 5% 4 7% 7% 33%	3230
	11th to 20th	Night	14% 6% 2 6% 4 5% 6% 5% 8% 8% 37%	3195
	21st to end	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 44%	3640
August	1st to 10th	Night	16% 7% 3 7% 5% 5% 5% 5% 6% 7% 34%	2915
	11th to 20th	Night	15% 6% 2 7% 5% 5% 6% 3 5% 8% 37%	2872
	21st to end	Night	15% 5% 2 4 4 4 4 4 4 7% 46%	3223
September	1st to 10th	Night	17% 6% 1 5% 3 4 4 4 5% 6% 45%	1998
	11th to 20th	Night	15% 6% 2 5% 3 4 4 3 4 6% 48%	2144
	21st to end	Night	19% 4 2 5% 3 3 3 3 4 5% 47%	2215
October	1st to 10th	Night	18% 7% 2 7% 3 4 3 3 4 6% 42%	2400
	11th to 20th	Night	20% 8% 3 7% 4 4 5% 4 6% 6% 34%	2400
	21st to end	Night	23% 7% 2 6% 5% 4 4 4 5% 7% 33%	2767
November	1st to 10th	Night	21% 8% 3 7% 5% 4 6% 4 5% 6% 33%	2869
	11th to 20th	Night	20% 11% 4 8% 5% 5% 5% 4 5% 5% 27%	2940
	21st to end	Night	21% 12% 4 8% 5% 5% 6% 4 5% 6% 24%	2940
December	1st to 10th	Night	13% 12% 5% 10% 6% 6% 5% 4 7% 6% 26%	4908
	11th to 20th	Night	22% 11% 4 8% 5% 4 4 3 5% 6% 27%	5741
	21st to end	Night	16% 15% 5% 10% 4 4 4 3 5% 5% 30%	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	63% 4 13% 11% 8%	4094
	11th to 20th	Day	59% 10% 12% 12% 6%	4110
	21st to end	Day	42% 6% 18% 22% 12%	5383
February	1st to 10th	Day	48% 5% 13% 21% 11% 2	1890
	11th to 20th	Day	53% 5% 11% 21% 11% 1	1851
	21st to end	Day	44% 6% 9% 26% 13% 2	1583
March	1st to 10th	Day	51% 4 13% 18% 13% 1	4893
	11th to 20th	Day	58% 5% 11% 15% 9% 2	5090
	21st to end	Day	56% 5% 6% 20% 13% 1	5587
April	1st to 10th	Day	49% 5% 9% 19% 16% 2	2504
	11th to 20th	Day	45% 5% 10% 25% 14% 1	2702
	21st to end	Day	52% 4 10% 17% 13% 3	2730
May	1st to 10th	Day	56% 5% 11% 18% 10% 1	7946
	11th to 20th	Day	48% 5% 14% 22% 10% 1	8224
	21st to end	Day	51% 6% 10% 20% 12% 1	9571
June	1st to 10th	Day	49% 5% 13% 21% 11% 1	3150
	11th to 20th	Day	45% 6% 13% 22% 12% 2	3150
	21st to end	Day	52% 6% 14% 18% 8% 1	3150
July	1st to 10th	Day	41% 6% 19% 24% 10%	6895
	11th to 20th	Day	39% 7% 22% 25% 7%	6814
	21st to end	Day	34% 5% 21% 30% 9%	6964
August	1st to 10th	Day	42% 5% 20% 24% 10%	4222
	11th to 20th	Day	42% 7% 21% 24% 6% 1	4214
	21st to end	Day	35% 5% 20% 25% 15%	4675
September	1st to 10th	Day	40% 5% 16% 28% 11%	2401
	11th to 20th	Day	39% 4 17% 27% 13%	2254
	21st to end	Day	42% 6% 13% 28% 11%	2185
October	1st to 10th	Day	41% 6% 17% 27% 8% 1	3260
	11th to 20th	Day	50% 5% 15% 23% 7%	3240
	21st to end	Day	44% 5% 18% 21% 11%	3320
November	1st to 10th	Day	50% 6% 14% 21% 8% 1	1647
	11th to 20th	Day	55% 7% 14% 17% 6% 1	1680
	21st to end	Day	61% 5% 14% 15% 5%	1680
December	1st to 10th	Day	60% 7% 14% 16% 3	2497
	11th to 20th	Day	60% 4 11% 17% 7% 1	2688
	21st to end	Day	55% 4 13% 19% 7% 2	3553
January	1st to 10th	Night	63% 4 15% 15% 3	8831
	11th to 20th	Night	58% 9% 11% 14% 6%	8880
	21st to end	Night	45% 4 18% 19% 13%	8781
February	1st to 10th	Night	50% 5% 12% 18% 13% 3	2730
	11th to 20th	Night	55% 4 9% 20% 11% 1	2666
	21st to end	Night	49% 4 9% 21% 14% 2	2221
March	1st to 10th	Night	57% 3 9% 16% 14% 1	5179
	11th to 20th	Night	62% 6% 8% 13% 10% 1	5090
	21st to end	Night	59% 4 7% 15% 14% 2	5587
April	1st to 10th	Night	57% 3 8% 15% 14% 2	2113
	11th to 20th	Night	50% 4 8% 22% 14% 2	1868
	21st to end	Night	53% 3 9% 17% 16% 2	1890
May	1st to 10th	Night	57% 4 8% 17% 12% 2	4983
	11th to 20th	Night	49% 4 11% 23% 11% 1	4671
	21st to end	Night	50% 7% 9% 18% 15%	4680
June	1st to 10th	Night	52% 5% 10% 21% 12%	1470
	11th to 20th	Night	48% 6% 11% 21% 12% 2	1470
	21st to end	Night	54% 7% 13% 17% 9% 1	1470
July	1st to 10th	Night	49% 5% 16% 22% 7%	3195
	11th to 20th	Night	41% 6% 21% 27% 4	3153
	21st to end	Night	37% 7% 21% 24% 10%	3534
August	1st to 10th	Night	49% 5% 17% 22% 7%	2903
	11th to 20th	Night	43% 7% 20% 23% 6%	2899
	21st to end	Night	38% 6% 18% 23% 15%	3223
September	1st to 10th	Night	40% 4 15% 30% 10% 1	1998
	11th to 20th	Night	37% 5% 15% 30% 12% 1	2144
	21st to end	Night	39% 4 11% 29% 15% 1	2215
October	1st to 10th	Night	47% 4 12% 27% 8% 1	3920
	11th to 20th	Night	44% 5% 14% 28% 8%	3899
	21st to end	Night	44% 4 19% 22% 10%	4467
November	1st to 10th	Night	52% 5% 15% 20% 8% 1	2869
	11th to 20th	Night	59% 5% 13% 17% 6% 1	2940
	21st to end	Night	62% 6% 13% 14% 5%	2940
December	1st to 10th	Night	57% 6% 15% 18% 3	4908
	11th to 20th	Night	58% 5% 11% 20% 6%	5742
	21st to end	Night	57% 5% 12% 18% 7% 2	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	29% 16% 30% 15% 9% 1	220
	11th to 20th	Day	28% 20% 20% 19% 10% 3	220
	21st to end	Day	13% 17% 33% 26% 10% 1	337
February	1st to 10th	Day	18% 16% 29% 24% 8% 5%	430
	11th to 20th	Day	19% 19% 31% 22% 7% 1	426
	21st to end	Day	15% 16% 33% 25% 9% 2	369
March	1st to 10th	Day	24% 12% 30% 25% 8% 2	540
	11th to 20th	Day	20% 14% 28% 26% 9% 2	540
	21st to end	Day	24% 14% 29% 22% 9% 3	594
April	1st to 10th	Day	26% 16% 29% 22% 6% 1	540
	11th to 20th	Day	26% 10% 28% 24% 8% 3	532
	21st to end	Day	27% 11% 26% 24% 9% 4	540
May	1st to 10th	Day	27% 9% 27% 24% 10% 4	645
	11th to 20th	Day	25% 9% 25% 22% 16% 4	774
	21st to end	Day	24% 9% 28% 26% 11% 2	845
June	1st to 10th	Day	25% 7% 25% 27% 14% 2	780
	11th to 20th	Day	22% 7% 26% 28% 15% 3	780
	21st to end	Day	24% 8% 22% 28% 16% 3	780
July	1st to 10th	Day	16% 7% 26% 30% 16% 4	770
	11th to 20th	Day	14% 5% 23% 35% 21% 2	743
	21st to end	Day	18% 4 20% 32% 21% 5%	775
August	1st to 10th	Day	14% 4 24% 30% 23% 4	526
	11th to 20th	Day	18% 4 20% 32% 20% 6%	519
	21st to end	Day	15% 6% 21% 31% 21% 7%	583
September	1st to 10th	Day	16% 8% 28% 25% 17% 6%	530
	11th to 20th	Day	21% 10% 24% 26% 13% 6%	530
	21st to end	Day	19% 12% 25% 25% 15% 5%	522
October	1st to 10th	Day	17% 12% 26% 25% 16% 4	420
	11th to 20th	Day	24% 14% 26% 20% 13% 4	420
	21st to end	Day	27% 15% 25% 20% 10% 2	462
November	1st to 10th	Day	25% 16% 28% 23% 7% 1	425
	11th to 20th	Day	29% 15% 24% 23% 8% 2	430
	21st to end	Day	28% 19% 27% 19% 6% 1	430
December	1st to 10th	Day	28% 11% 28% 25% 7% 1	315
	11th to 20th	Day	25% 20% 33% 18% 4	220
	21st to end	Day	24% 18% 28% 24% 6% 1	242
January	1st to 10th	Night	22% 15% 32% 24% 6% 1	950
	11th to 20th	Night	22% 15% 31% 25% 7%	950
	21st to end	Night	16% 18% 33% 25% 8% 1	925
February	1st to 10th	Night	15% 14% 34% 27% 9% 1	840
	11th to 20th	Night	23% 15% 30% 24% 6% 2	823
	21st to end	Night	20% 11% 31% 28% 9% 1	692
March	1st to 10th	Night	20% 11% 31% 30% 7%	840
	11th to 20th	Night	21% 11% 29% 28% 10% 1	840
	21st to end	Night	22% 11% 27% 30% 9% 1	924
April	1st to 10th	Night	31% 8% 26% 29% 6%	677
	11th to 20th	Night	27% 5% 28% 29% 10% 1	624
	21st to end	Night	29% 7% 21% 32% 9% 1	630
May	1st to 10th	Night	27% 6% 26% 28% 12% 1	630
	11th to 20th	Night	23% 5% 27% 29% 14% 2	622
	21st to end	Night	21% 7% 30% 32% 10% 1	526
June	1st to 10th	Night	26% 5% 19% 40% 10% 1	420
	11th to 20th	Night	23% 3 18% 36% 19% 1	420
	21st to end	Night	28% 4 16% 38% 11% 1	420
July	1st to 10th	Night	20% 3 20% 39% 17% 2	410
	11th to 20th	Night	17% 2 19% 47% 14% 2	398
	21st to end	Night	17% 4 17% 39% 22% 2	503
August	1st to 10th	Night	15% 4 18% 43% 20% 1	598
	11th to 20th	Night	16% 4 15% 41% 23% 2	592
	21st to end	Night	15% 5% 19% 37% 22% 2	660
September	1st to 10th	Night	19% 6% 26% 32% 16% 1	600
	11th to 20th	Night	18% 8% 19% 36% 17% 1	744
	21st to end	Night	20% 9% 22% 33% 15% 1	800
October	1st to 10th	Night	23% 7% 29% 28% 12% 1	800
	11th to 20th	Night	25% 10% 26% 25% 13% 1	800
	21st to end	Night	28% 13% 25% 25% 9%	880
November	1st to 10th	Night	26% 14% 28% 25% 6% 1	928
	11th to 20th	Night	27% 15% 28% 21% 7% 2	950
	21st to end	Night	27% 17% 28% 20% 6% 1	950
December	1st to 10th	Night	26% 13% 30% 23% 7% 1	950
	11th to 20th	Night	27% 21% 32% 15% 5% 1	950
	21st to end	Night	27% 15% 30% 23% 4 1	1045

Page generated at 2026-07-13 03:14:53. Version ac07

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