Constance Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Constance Bay clear sky chart from 2005-11-06 to 2024-11-05.

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 8% 5% 5% 5% 4 5% 7% 33%	101586
	Night	17% 11% 4 9% 5% 4 4 3 5% 6% 31%	97459
Transparency	Day	50% 6% 12% 22% 10% 1	105082
	Night	52% 6% 12% 20% 9% 1	102052
Seeing	Day	22% 15% 30% 20% 9% 3	14459
	Night	22% 12% 29% 26% 10% 1	23535

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% 6% 12% 6% 5% 5% 3 5% 4 21%	2517
	11th to 20th	Day	14% 13% 6% 16% 7% 6% 5% 3 5% 5% 22%	2520
	21st to end	Day	14% 17% 6% 13% 9% 6% 5% 3 4 4 18%	2904
February	1st to 10th	Day	13% 15% 5% 13% 8% 5% 5% 3 5% 5% 24%	1710
	11th to 20th	Day	12% 15% 6% 11% 5% 5% 4 4 4 6% 28%	1663
	21st to end	Day	19% 12% 4 10% 6% 4 4 4 5% 5% 27%	1560
March	1st to 10th	Day	21% 14% 4 8% 6% 4 5% 3 4 4 27%	3139
	11th to 20th	Day	12% 15% 5% 11% 7% 5% 5% 3 5% 6% 27%	3480
	21st to end	Day	13% 8% 3 7% 5% 4 3 3 6% 6% 41%	4006
April	1st to 10th	Day	22% 12% 3 6% 4 4 4 3 4 7% 31%	2280
	11th to 20th	Day	22% 10% 3 7% 4 3 4 3 4 5% 36%	2254
	21st to end	Day	22% 10% 3 7% 5% 4 4 3 4 5% 32%	2423
May	1st to 10th	Day	20% 8% 3 7% 5% 5% 4 4 5% 7% 32%	4426
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 3 5% 8% 33%	4398
	21st to end	Day	16% 7% 2 7% 5% 4 4 4 5% 6% 38%	4837
June	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 4 5% 7% 30%	2660
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	2660
	21st to end	Day	19% 7% 3 6% 5% 5% 5% 4 6% 8% 31%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 10% 35%	4440
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 4 6% 8% 41%	4440
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 45%	4814
August	1st to 10th	Day	14% 6% 3 8% 5% 5% 5% 4 7% 8% 36%	4335
	11th to 20th	Day	16% 7% 3 5% 5% 4 4 4 6% 10% 37%	4017
	21st to end	Day	13% 5% 2 6% 4 4 5% 5% 6% 9% 41%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 4 5% 4 5% 8% 43%	2280
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 6% 8% 46%	2280
	21st to end	Day	17% 6% 2 7% 3 4 4 4 5% 8% 39%	2020
October	1st to 10th	Day	21% 8% 3 7% 4 4 4 3 6% 6% 34%	1900
	11th to 20th	Day	23% 8% 3 7% 5% 5% 5% 3 5% 7% 29%	1900
	21st to end	Day	26% 10% 3 7% 5% 4 4 4 4 6% 28%	1947
November	1st to 10th	Day	15% 10% 3 6% 5% 5% 5% 4 6% 7% 34%	1698
	11th to 20th	Day	19% 13% 3 8% 6% 5% 4 4 5% 6% 26%	1520
	21st to end	Day	21% 15% 3 9% 7% 5% 5% 4 4 6% 20%	1520
December	1st to 10th	Day	22% 19% 5% 10% 5% 5% 4 3 5% 5% 17%	1520
	11th to 20th	Day	21% 14% 4 10% 5% 5% 4 3 5% 5% 24%	1906
	21st to end	Day	28% 17% 5% 11% 5% 3 3 2 2 3 19%	2772
January	1st to 10th	Night	17% 19% 7% 13% 6% 5% 4 3 4 5% 19%	4429
	11th to 20th	Night	12% 15% 5% 14% 7% 6% 6% 3 4 5% 23%	4440
	21st to end	Night	15% 20% 6% 11% 7% 6% 4 3 4 4 21%	4748
February	1st to 10th	Night	13% 14% 5% 12% 7% 5% 5% 4 5% 6% 23%	2470
	11th to 20th	Night	13% 14% 5% 11% 7% 4 4 3 4 5% 29%	2403
	21st to end	Night	16% 13% 4 9% 6% 4 5% 3 5% 6% 28%	1893
March	1st to 10th	Night	21% 13% 4 7% 5% 4 3 3 3 5% 30%	3697
	11th to 20th	Night	15% 16% 5% 11% 5% 4 4 3 5% 6% 25%	3479
	21st to end	Night	15% 9% 3 8% 5% 3 3 3 5% 6% 40%	3626
April	1st to 10th	Night	20% 10% 3 8% 4 4 3 3 5% 5% 33%	1900
	11th to 20th	Night	19% 9% 4 8% 4 4 4 4 4 5% 35%	1875
	21st to end	Night	20% 10% 3 8% 5% 4 4 3 5% 5% 34%	1772
May	1st to 10th	Night	20% 9% 3 7% 5% 4 5% 4 7% 6% 30%	2514
	11th to 20th	Night	19% 9% 3 6% 4 4 5% 4 5% 7% 34%	2495
	21st to end	Night	14% 6% 3 7% 5% 4 5% 4 6% 7% 39%	2738
June	1st to 10th	Night	16% 7% 3 6% 5% 5% 5% 5% 7% 9% 34%	1520
	11th to 20th	Night	13% 5% 3 7% 4 5% 3 4 6% 8% 43%	1520
	21st to end	Night	18% 7% 2 6% 5% 3 5% 4 7% 7% 36%	1520
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 5% 5% 6% 7% 35%	2520
	11th to 20th	Night	13% 6% 2 7% 5% 4 4 4 5% 8% 41%	2520
	21st to end	Night	10% 5% 2 6% 4 5% 4 4 7% 8% 44%	2739
August	1st to 10th	Night	12% 7% 3 7% 5% 4 4 4 6% 9% 39%	2591
	11th to 20th	Night	15% 7% 3 6% 3 4 5% 4 6% 7% 41%	2785
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 7% 8% 41%	3470
September	1st to 10th	Night	12% 5% 3 6% 4 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	14% 4 2 5% 3 4 3 3 5% 7% 49%	1900
	21st to end	Night	19% 6% 2 7% 4 3 4 3 4 6% 43%	2154
October	1st to 10th	Night	18% 8% 2 6% 4 5% 5% 3 5% 7% 38%	2280
	11th to 20th	Night	21% 9% 3 8% 5% 6% 4 4 5% 6% 31%	2280
	21st to end	Night	23% 11% 3 7% 6% 5% 4 3 5% 6% 27%	2650
November	1st to 10th	Night	20% 10% 3 7% 5% 4 4 3 5% 6% 34%	2479
	11th to 20th	Night	20% 11% 4 7% 5% 5% 5% 3 5% 6% 28%	2660
	21st to end	Night	22% 13% 4 10% 5% 4 4 3 5% 6% 23%	2660
December	1st to 10th	Night	22% 17% 5% 11% 6% 4 4 5% 5% 5% 17%	2660
	11th to 20th	Night	22% 15% 4 9% 6% 4 4 3 3 4 26%	3288
	21st to end	Night	29% 18% 4 11% 4 4 3 2 3 4 18%	4884

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	64% 6% 14% 10% 6% 1	2518
	11th to 20th	Day	65% 4 11% 13% 6% 1	2520
	21st to end	Day	69% 6% 9% 10% 5% 1	2904
February	1st to 10th	Day	62% 4 10% 18% 4 1	1710
	11th to 20th	Day	57% 4 13% 16% 9% 1	1672
	21st to end	Day	59% 5% 12% 14% 10% 2	1560
March	1st to 10th	Day	60% 4 9% 17% 9% 1	3142
	11th to 20th	Day	57% 5% 12% 16% 9% 2	3480
	21st to end	Day	42% 4 8% 26% 17% 3	4006
April	1st to 10th	Day	54% 4 8% 19% 12% 3	2280
	11th to 20th	Day	51% 4 7% 22% 15% 2	2254
	21st to end	Day	55% 5% 7% 15% 14% 4	2423
May	1st to 10th	Day	50% 7% 9% 22% 10% 2	4440
	11th to 20th	Day	48% 7% 13% 20% 10% 1	4402
	21st to end	Day	45% 6% 12% 21% 15% 2	4837
June	1st to 10th	Day	52% 6% 11% 20% 11%	2660
	11th to 20th	Day	42% 6% 13% 23% 13% 2	2660
	21st to end	Day	49% 7% 13% 20% 10%	2660
July	1st to 10th	Day	41% 7% 15% 25% 11%	4370
	11th to 20th	Day	38% 6% 15% 31% 9%	4365
	21st to end	Day	35% 7% 14% 33% 11%	4661
August	1st to 10th	Day	45% 6% 15% 23% 9%	4321
	11th to 20th	Day	42% 6% 15% 29% 8%	4056
	21st to end	Day	38% 6% 17% 27% 12% 1	4180
September	1st to 10th	Day	39% 7% 15% 28% 11%	2280
	11th to 20th	Day	36% 6% 15% 31% 12% 1	2280
	21st to end	Day	43% 7% 14% 26% 10%	2020
October	1st to 10th	Day	48% 5% 11% 28% 7%	3160
	11th to 20th	Day	47% 5% 14% 26% 8%	3140
	21st to end	Day	50% 6% 18% 19% 7%	3185
November	1st to 10th	Day	47% 6% 15% 24% 6% 1	1698
	11th to 20th	Day	57% 6% 13% 15% 7% 1	1520
	21st to end	Day	65% 7% 13% 9% 7% 1	1520
December	1st to 10th	Day	69% 5% 12% 10% 3 1	1520
	11th to 20th	Day	61% 7% 13% 14% 5%	1906
	21st to end	Day	73% 3 7% 14% 3	2772
January	1st to 10th	Night	68% 4 14% 11% 3	4429
	11th to 20th	Night	62% 6% 14% 13% 5%	4440
	21st to end	Night	69% 4 10% 11% 6%	4748
February	1st to 10th	Night	61% 5% 11% 16% 6% 1	2470
	11th to 20th	Night	57% 4 11% 19% 8% 1	2405
	21st to end	Night	56% 5% 10% 18% 10% 1	1893
March	1st to 10th	Night	57% 4 9% 19% 9% 2	3707
	11th to 20th	Night	59% 5% 12% 15% 7% 1	3480
	21st to end	Night	43% 6% 8% 23% 16% 4	3626
April	1st to 10th	Night	53% 5% 9% 18% 14% 2	1900
	11th to 20th	Night	50% 5% 8% 21% 15% 2	1875
	21st to end	Night	53% 4 8% 16% 16% 4	1772
May	1st to 10th	Night	51% 7% 10% 20% 9% 3	2520
	11th to 20th	Night	47% 7% 12% 21% 11% 2	2496
	21st to end	Night	42% 7% 13% 19% 17% 2	2739
June	1st to 10th	Night	45% 8% 13% 24% 9% 1	1520
	11th to 20th	Night	39% 6% 13% 24% 16% 2	1520
	21st to end	Night	45% 8% 12% 21% 13% 1	1520
July	1st to 10th	Night	46% 8% 13% 19% 13% 1	2480
	11th to 20th	Night	41% 6% 12% 32% 9%	2472
	21st to end	Night	37% 7% 15% 27% 14%	2651
August	1st to 10th	Night	40% 8% 15% 25% 11% 1	2581
	11th to 20th	Night	41% 6% 16% 29% 8%	2812
	21st to end	Night	39% 7% 14% 26% 11% 2	3470
September	1st to 10th	Night	37% 6% 12% 29% 15% 1	1900
	11th to 20th	Night	35% 6% 14% 33% 10% 1	1900
	21st to end	Night	42% 5% 12% 30% 11%	2154
October	1st to 10th	Night	40% 6% 13% 29% 12%	3800
	11th to 20th	Night	47% 5% 15% 24% 9%	3779
	21st to end	Night	50% 6% 17% 18% 8%	4362
November	1st to 10th	Night	51% 6% 14% 21% 8%	2479
	11th to 20th	Night	56% 5% 12% 17% 8% 1	2660
	21st to end	Night	62% 6% 13% 15% 5%	2660
December	1st to 10th	Night	67% 6% 10% 13% 3	2660
	11th to 20th	Night	63% 4 9% 16% 7% 1	3288
	21st to end	Night	73% 4 7% 12% 4	4884

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	21% 23% 36% 16% 5%	180
	11th to 20th	Day	27% 21% 32% 16% 4	180
	21st to end	Day	21% 17% 36% 22% 4	236
February	1st to 10th	Day	29% 23% 34% 12% 2	270
	11th to 20th	Day	30% 27% 36% 7% 1	270
	21st to end	Day	32% 23% 30% 13% 2	372
March	1st to 10th	Day	28% 18% 32% 17% 4 1	460
	11th to 20th	Day	25% 20% 36% 15% 3 1	460
	21st to end	Day	32% 18% 28% 16% 5% 1	506
April	1st to 10th	Day	34% 19% 27% 14% 5%	460
	11th to 20th	Day	34% 18% 22% 14% 10% 2	452
	21st to end	Day	28% 21% 30% 14% 6% 1	460
May	1st to 10th	Day	27% 14% 31% 19% 7% 2	463
	11th to 20th	Day	20% 17% 30% 21% 9% 3	487
	21st to end	Day	19% 16% 30% 22% 11% 2	529
June	1st to 10th	Day	26% 11% 31% 22% 9% 2	490
	11th to 20th	Day	16% 16% 29% 24% 12% 3	490
	21st to end	Day	22% 13% 30% 22% 10% 3	490
July	1st to 10th	Day	10% 9% 29% 34% 15% 4	485
	11th to 20th	Day	12% 8% 33% 27% 15% 4	484
	21st to end	Day	13% 8% 31% 31% 14% 4	532
August	1st to 10th	Day	13% 7% 29% 32% 16% 4	486
	11th to 20th	Day	14% 8% 23% 29% 19% 8%	479
	21st to end	Day	16% 10% 29% 24% 14% 7%	539
September	1st to 10th	Day	15% 11% 30% 22% 14% 8%	490
	11th to 20th	Day	12% 10% 24% 23% 20% 12%	490
	21st to end	Day	17% 13% 28% 22% 14% 6%	490
October	1st to 10th	Day	24% 14% 24% 21% 12% 4	490
	11th to 20th	Day	26% 18% 29% 18% 8% 1	490
	21st to end	Day	30% 18% 24% 22% 5%	463
November	1st to 10th	Day	25% 18% 29% 20% 8% 1	368
	11th to 20th	Day	28% 22% 33% 11% 5%	180
	21st to end	Day	28% 21% 35% 12% 3 1	180
December	1st to 10th	Day	33% 16% 37% 12% 2	180
	11th to 20th	Day	31% 26% 32% 9% 2	180
	21st to end	Day	28% 22% 34% 13% 2 1	198
January	1st to 10th	Night	28% 14% 34% 20% 3	760
	11th to 20th	Night	28% 17% 28% 21% 7%	760
	21st to end	Night	19% 13% 37% 26% 5%	836
February	1st to 10th	Night	21% 17% 35% 24% 3	760
	11th to 20th	Night	20% 18% 39% 19% 4	743
	21st to end	Night	23% 19% 28% 26% 4	628
March	1st to 10th	Night	24% 16% 34% 23% 4	760
	11th to 20th	Night	24% 18% 31% 21% 5%	760
	21st to end	Night	23% 17% 28% 25% 7%	836
April	1st to 10th	Night	27% 14% 29% 25% 4	760
	11th to 20th	Night	24% 18% 29% 21% 8%	751
	21st to end	Night	25% 13% 30% 23% 8%	632
May	1st to 10th	Night	23% 7% 28% 31% 9% 2	380
	11th to 20th	Night	24% 10% 28% 30% 9%	374
	21st to end	Night	16% 7% 37% 27% 13%	411
June	1st to 10th	Night	18% 5% 32% 34% 11%	380
	11th to 20th	Night	16% 8% 25% 36% 14% 1	380
	21st to end	Night	20% 7% 26% 33% 14%	380
July	1st to 10th	Night	11% 4 27% 40% 18%	370
	11th to 20th	Night	13% 5% 22% 44% 16% 1	368
	21st to end	Night	9% 6% 23% 45% 16% 1	416
August	1st to 10th	Night	10% 6% 20% 43% 21% 1	424
	11th to 20th	Night	12% 4 18% 39% 24% 3	564
	21st to end	Night	13% 7% 24% 35% 19% 2	830
September	1st to 10th	Night	14% 5% 28% 31% 20% 2	760
	11th to 20th	Night	15% 8% 21% 31% 22% 4	760
	21st to end	Night	20% 8% 24% 26% 20% 2	760
October	1st to 10th	Night	23% 10% 25% 25% 15% 1	760
	11th to 20th	Night	25% 13% 28% 24% 8% 1	760
	21st to end	Night	28% 14% 27% 25% 6%	836
November	1st to 10th	Night	26% 14% 26% 26% 7% 1	760
	11th to 20th	Night	25% 16% 32% 17% 9%	760
	21st to end	Night	31% 14% 26% 22% 6%	760
December	1st to 10th	Night	31% 15% 29% 21% 4	760
	11th to 20th	Night	27% 17% 30% 20% 5% 1	760
	21st to end	Night	33% 16% 30% 18% 4	836

Page generated at 2024-11-03 02:11:30. Version ac07

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