Bethune Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bethune Beach clear sky chart from 2005-11-06 to 2026-01-02.

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	7% 5% 2 6% 5% 5% 6% 5% 8% 10% 40%	126936
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	124440
Transparency	Day	33% 10% 20% 21% 13% 3	130605
	Night	36% 9% 17% 21% 13% 4	128840
Seeing	Day	8% 4 15% 27% 29% 16%	17257
	Night	9% 4 15% 29% 31% 12%	27352

By Month

Percentage Cloud Cover SE (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% 5% 2 5% 4 4 4 4 5% 7% 52%	4065
	11th to 20th	Day	18% 10% 4 8% 5% 5% 5% 4 5% 6% 30%	4060
	21st to end	Day	16% 5% 2 6% 4 4 4 3 5% 8% 43%	4466
February	1st to 10th	Day	11% 6% 3 6% 5% 5% 5% 5% 6% 8% 41%	1970
	11th to 20th	Day	8% 6% 2 5% 4 4 4 4 5% 7% 50%	1952
	21st to end	Day	9% 6% 2 6% 4 5% 4 3 6% 7% 48%	1815
March	1st to 10th	Day	6% 7% 3 8% 5% 5% 5% 4 6% 10% 40%	4935
	11th to 20th	Day	4 3 1 4 3 3 3 3 5% 9% 61%	4980
	21st to end	Day	9% 6% 2 7% 3 4 5% 4 7% 9% 44%	5465
April	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 6% 9% 50%	2200
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	2281
	21st to end	Day	4 4 1 4 4 4 6% 4 6% 10% 51%	2400
May	1st to 10th	Day	3 3 1 4 4 4 5% 5% 8% 13% 50%	5577
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	5861
	21st to end	Day	4 3 1 5% 5% 5% 6% 6% 9% 12% 45%	6433
June	1st to 10th	Day	10% 6% 2 8% 7% 7% 7% 5% 9% 11% 28%	2600
	11th to 20th	Day	5% 4 2 8% 6% 7% 8% 7% 9% 12% 30%	2600
	21st to end	Day	8% 6% 2 8% 7% 6% 7% 6% 9% 10% 30%	2600
July	1st to 10th	Day	6% 5% 2 8% 6% 7% 9% 7% 11% 13% 26%	5900
	11th to 20th	Day	4 4 2 6% 5% 5% 8% 7% 10% 14% 36%	5900
	21st to end	Day	4 3 2 5% 6% 5% 7% 6% 10% 14% 39%	6424
August	1st to 10th	Day	5% 5% 2 8% 7% 7% 7% 6% 10% 13% 29%	4234
	11th to 20th	Day	3 3 2 6% 6% 6% 8% 6% 10% 13% 36%	3987
	21st to end	Day	7% 5% 3 7% 5% 6% 6% 6% 10% 14% 30%	4064
September	1st to 10th	Day	7% 7% 3 8% 8% 8% 9% 7% 9% 10% 23%	2200
	11th to 20th	Day	9% 6% 3 8% 7% 6% 8% 5% 10% 12% 25%	2200
	21st to end	Day	10% 7% 3 9% 6% 6% 6% 6% 9% 10% 28%	2200
October	1st to 10th	Day	13% 7% 3 8% 6% 6% 5% 6% 6% 10% 31%	2115
	11th to 20th	Day	7% 5% 2 6% 5% 6% 5% 5% 7% 9% 43%	2000
	21st to end	Day	8% 5% 1 5% 4 5% 5% 4 7% 10% 46%	2200
November	1st to 10th	Day	7% 6% 2 7% 6% 5% 6% 4 8% 9% 40%	2057
	11th to 20th	Day	8% 6% 2 7% 6% 5% 5% 5% 6% 9% 41%	2100
	21st to end	Day	9% 7% 3 6% 6% 5% 5% 4 6% 7% 41%	2047
December	1st to 10th	Day	6% 3 2 5% 4 3 4 4 5% 9% 55%	3020
	11th to 20th	Day	10% 7% 3 8% 5% 6% 6% 5% 8% 9% 35%	3463
	21st to end	Day	11% 7% 3 8% 5% 5% 5% 4 7% 7% 38%	4565
January	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 5% 8% 52%	5903
	11th to 20th	Night	17% 10% 3 8% 5% 4 5% 4 6% 7% 30%	5900
	21st to end	Night	14% 6% 2 6% 4 4 4 4 6% 8% 41%	6490
February	1st to 10th	Night	11% 7% 2 6% 5% 4 4 4 6% 8% 43%	2425
	11th to 20th	Night	11% 6% 1 5% 5% 3 5% 4 5% 7% 48%	2333
	21st to end	Night	7% 5% 1 5% 5% 3 5% 4 6% 7% 51%	1815
March	1st to 10th	Night	10% 7% 3 7% 5% 4 4 3 6% 7% 44%	4918
	11th to 20th	Night	5% 3 1 3 3 3 4 4 6% 10% 57%	4980
	21st to end	Night	7% 6% 2 7% 4 4 5% 4 6% 7% 46%	5467
April	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 7% 8% 52%	2200
	11th to 20th	Night	6% 6% 2 6% 5% 4 4 4 6% 7% 49%	2065
	21st to end	Night	5% 4 1 5% 4 4 5% 4 5% 9% 53%	2000
May	1st to 10th	Night	4 3 1 5% 4 4 5% 4 6% 10% 53%	4359
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 4 7% 9% 45%	4032
	21st to end	Night	5% 4 2 6% 4 5% 5% 5% 8% 13% 44%	4421
June	1st to 10th	Night	9% 6% 3 8% 5% 5% 7% 5% 8% 11% 33%	1800
	11th to 20th	Night	4 7% 3 7% 6% 7% 7% 5% 8% 12% 34%	1800
	21st to end	Night	6% 8% 2 8% 5% 5% 4 5% 9% 11% 36%	1800
July	1st to 10th	Night	7% 7% 3 9% 6% 6% 7% 5% 8% 11% 30%	4058
	11th to 20th	Night	3 4 2 6% 5% 5% 5% 6% 9% 14% 40%	4057
	21st to end	Night	4 4 2 7% 5% 6% 6% 6% 7% 12% 42%	4427
August	1st to 10th	Night	5% 5% 3 9% 7% 6% 6% 5% 8% 11% 35%	2915
	11th to 20th	Night	3 3 2 6% 5% 6% 6% 5% 9% 13% 41%	3026
	21st to end	Night	7% 6% 3 7% 6% 6% 6% 5% 9% 14% 32%	3814
September	1st to 10th	Night	8% 7% 3 9% 7% 7% 8% 7% 9% 10% 26%	2200
	11th to 20th	Night	8% 9% 3 9% 7% 6% 6% 6% 8% 11% 26%	2200
	21st to end	Night	11% 6% 2 8% 6% 5% 7% 5% 8% 9% 32%	2200
October	1st to 10th	Night	9% 7% 3 9% 6% 5% 5% 5% 8% 9% 33%	2282
	11th to 20th	Night	7% 6% 2 5% 4 4 5% 4 6% 9% 49%	2400
	21st to end	Night	9% 5% 2 6% 4 4 4 4 6% 9% 47%	2640
November	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 5% 6% 8% 41%	2461
	11th to 20th	Night	8% 7% 3 7% 5% 5% 5% 4 5% 8% 43%	2520
	21st to end	Night	9% 6% 3 8% 6% 5% 5% 4 6% 9% 39%	2567
December	1st to 10th	Night	5% 4 2 4 5% 4 4 4 6% 8% 54%	4380
	11th to 20th	Night	11% 8% 2 7% 4 5% 5% 4 6% 8% 39%	4952
	21st to end	Night	11% 8% 3 8% 5% 5% 5% 4 6% 7% 39%	6633

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	32% 4 11% 16% 28% 8%	4066
	11th to 20th	Day	55% 4 6% 15% 17% 3	4060
	21st to end	Day	39% 6% 9% 26% 14% 6%	4466
February	1st to 10th	Day	39% 6% 11% 18% 20% 5%	1970
	11th to 20th	Day	31% 5% 11% 23% 22% 7%	1962
	21st to end	Day	33% 6% 11% 20% 23% 7%	1815
March	1st to 10th	Day	37% 8% 14% 18% 20% 3	4935
	11th to 20th	Day	21% 5% 12% 28% 20% 14%	4980
	21st to end	Day	33% 6% 13% 26% 16% 6%	5465
April	1st to 10th	Day	28% 8% 13% 25% 19% 6%	2200
	11th to 20th	Day	32% 9% 12% 21% 21% 5%	2281
	21st to end	Day	24% 7% 15% 25% 23% 6%	2400
May	1st to 10th	Day	21% 9% 25% 30% 12% 3	5609
	11th to 20th	Day	33% 8% 18% 31% 10% 1	5865
	21st to end	Day	24% 9% 20% 35% 11% 1	6447
June	1st to 10th	Day	41% 12% 21% 21% 5%	2600
	11th to 20th	Day	35% 14% 24% 25% 2	2600
	21st to end	Day	38% 14% 28% 15% 4	2600
July	1st to 10th	Day	37% 16% 33% 12% 2	5835
	11th to 20th	Day	26% 15% 43% 14% 1	5831
	21st to end	Day	25% 15% 35% 24% 2	6240
August	1st to 10th	Day	35% 16% 36% 12% 1	4221
	11th to 20th	Day	26% 15% 33% 20% 7%	4026
	21st to end	Day	36% 16% 32% 15% 2	4064
September	1st to 10th	Day	41% 20% 24% 11% 4	2200
	11th to 20th	Day	42% 15% 25% 14% 4	2200
	21st to end	Day	42% 13% 19% 15% 10% 2	2200
October	1st to 10th	Day	50% 10% 15% 13% 8% 3	3440
	11th to 20th	Day	29% 7% 7% 24% 27% 6%	3240
	21st to end	Day	26% 6% 8% 25% 29% 5%	3538
November	1st to 10th	Day	35% 8% 12% 20% 19% 6%	2057
	11th to 20th	Day	39% 7% 9% 22% 18% 6%	2100
	21st to end	Day	39% 6% 10% 23% 18% 5%	2047
December	1st to 10th	Day	27% 6% 16% 30% 18% 4	3020
	11th to 20th	Day	43% 8% 12% 16% 17% 4	3460
	21st to end	Day	41% 6% 11% 22% 15% 4	4565
January	1st to 10th	Night	31% 4 9% 20% 28% 8%	5903
	11th to 20th	Night	52% 5% 10% 16% 14% 3	5900
	21st to end	Night	40% 6% 9% 23% 16% 6%	6490
February	1st to 10th	Night	37% 6% 12% 18% 18% 10%	2425
	11th to 20th	Night	34% 7% 12% 21% 18% 8%	2334
	21st to end	Night	31% 6% 14% 19% 23% 7%	1815
March	1st to 10th	Night	38% 6% 12% 19% 19% 7%	4918
	11th to 20th	Night	22% 7% 15% 26% 18% 14%	4980
	21st to end	Night	34% 7% 12% 22% 19% 6%	5467
April	1st to 10th	Night	27% 8% 17% 25% 15% 9%	2200
	11th to 20th	Night	32% 8% 10% 25% 19% 5%	2065
	21st to end	Night	28% 6% 14% 27% 20% 5%	2000
May	1st to 10th	Night	23% 10% 22% 29% 13% 3	4389
	11th to 20th	Night	31% 9% 23% 27% 9%	4033
	21st to end	Night	28% 10% 21% 29% 12%	4429
June	1st to 10th	Night	40% 11% 22% 22% 5%	1800
	11th to 20th	Night	38% 12% 23% 24% 3	1800
	21st to end	Night	39% 12% 26% 19% 5% 1	1800
July	1st to 10th	Night	44% 14% 28% 13% 2	4015
	11th to 20th	Night	27% 14% 46% 12% 1	4006
	21st to end	Night	30% 14% 29% 25% 1	4297
August	1st to 10th	Night	39% 13% 36% 11% 1	2904
	11th to 20th	Night	29% 13% 31% 22% 6%	3053
	21st to end	Night	39% 14% 30% 15% 2	3814
September	1st to 10th	Night	46% 17% 20% 12% 5%	2200
	11th to 20th	Night	47% 13% 21% 15% 3	2200
	21st to end	Night	45% 11% 15% 18% 9% 2	2200
October	1st to 10th	Night	56% 8% 12% 14% 7% 3	3737
	11th to 20th	Night	31% 7% 7% 24% 26% 5%	3899
	21st to end	Night	30% 5% 7% 22% 30% 5%	4252
November	1st to 10th	Night	38% 9% 11% 19% 18% 6%	2461
	11th to 20th	Night	40% 7% 10% 20% 17% 7%	2520
	21st to end	Night	40% 6% 12% 20% 17% 5%	2567
December	1st to 10th	Night	29% 6% 15% 32% 13% 6%	4380
	11th to 20th	Night	41% 7% 14% 19% 14% 6%	4954
	21st to end	Night	42% 7% 11% 21% 14% 5%	6633

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	15% 4 38% 30% 11% 2	303
	11th to 20th	Day	8% 6% 36% 32% 14% 4	300
	21st to end	Day	16% 10% 32% 32% 10% 1	330
February	1st to 10th	Day	13% 6% 28% 32% 19% 3	300
	11th to 20th	Day	9% 5% 27% 39% 16% 4	304
	21st to end	Day	8% 4 28% 37% 19% 4	414
March	1st to 10th	Day	5% 7% 35% 37% 14% 1	500
	11th to 20th	Day	8% 6% 28% 35% 20% 4	500
	21st to end	Day	7% 5% 28% 36% 21% 3	550
April	1st to 10th	Day	7% 6% 31% 35% 18% 3	500
	11th to 20th	Day	8% 5% 25% 33% 25% 4	492
	21st to end	Day	5% 2 19% 40% 25% 9%	500
May	1st to 10th	Day	4 3 18% 40% 27% 7%	503
	11th to 20th	Day	9% 2 13% 32% 33% 10%	527
	21st to end	Day	7% 2 6% 28% 38% 19%	573
June	1st to 10th	Day	10% 2 6% 30% 35% 16%	530
	11th to 20th	Day	4 3 5% 20% 38% 29%	530
	21st to end	Day	7% 3 1 12% 43% 34%	530
July	1st to 10th	Day	5% 3 2 8% 37% 45%	525
	11th to 20th	Day	5% 2 1 7% 43% 42%	524
	21st to end	Day	6% 2 2 14% 39% 38%	576
August	1st to 10th	Day	5% 3 2 12% 42% 35%	526
	11th to 20th	Day	3 1 1 9% 38% 49%	519
	21st to end	Day	9% 3 4 9% 38% 36%	583
September	1st to 10th	Day	10% 3 3 14% 37% 32%	530
	11th to 20th	Day	10% 4 4 19% 41% 22%	530
	21st to end	Day	9% 3 5% 21% 38% 24%	530
October	1st to 10th	Day	16% 4 10% 34% 28% 8%	530
	11th to 20th	Day	7% 4 12% 35% 32% 10%	530
	21st to end	Day	7% 3 17% 36% 31% 6%	583
November	1st to 10th	Day	7% 8% 17% 33% 27% 7%	535
	11th to 20th	Day	12% 4 20% 36% 22% 6%	540
	21st to end	Day	11% 5% 22% 34% 24% 4	487
December	1st to 10th	Day	5% 4 28% 40% 19% 5%	330
	11th to 20th	Day	8% 5% 29% 35% 21% 2	330
	21st to end	Day	7% 4 23% 36% 25% 4	363
January	1st to 10th	Night	12% 10% 25% 36% 16% 2	805
	11th to 20th	Night	11% 7% 27% 34% 18% 3	800
	21st to end	Night	14% 11% 30% 34% 12%	880
February	1st to 10th	Night	14% 7% 24% 34% 19% 2	800
	11th to 20th	Night	13% 7% 26% 37% 16% 2	783
	21st to end	Night	9% 5% 29% 40% 17% 1	660
March	1st to 10th	Night	6% 6% 30% 39% 18% 1	800
	11th to 20th	Night	9% 5% 22% 41% 20% 4	800
	21st to end	Night	8% 5% 25% 37% 24% 2	880
April	1st to 10th	Night	7% 4 25% 39% 22% 3	800
	11th to 20th	Night	7% 5% 23% 36% 27% 2	791
	21st to end	Night	6% 2 19% 39% 30% 4	800
May	1st to 10th	Night	7% 1 13% 42% 33% 3	747
	11th to 20th	Night	8% 3 12% 31% 36% 11%	591
	21st to end	Night	7% 2 6% 25% 45% 15%	650
June	1st to 10th	Night	11% 2 6% 25% 44% 13%	600
	11th to 20th	Night	6% 2 4 19% 43% 27%	600
	21st to end	Night	8% 2 2 13% 45% 30%	600
July	1st to 10th	Night	9% 2 2 10% 46% 32%	585
	11th to 20th	Night	5% 2 2 8% 45% 39%	582
	21st to end	Night	5% 2 1 10% 48% 34%	657
August	1st to 10th	Night	5% 2 2 10% 47% 34%	597
	11th to 20th	Night	3 2 1 7% 46% 41%	680
	21st to end	Night	10% 3 3 11% 43% 29%	880
September	1st to 10th	Night	9% 2 3 12% 46% 28%	800
	11th to 20th	Night	12% 3 3 20% 44% 19%	800
	21st to end	Night	14% 3 4 18% 42% 20%	800
October	1st to 10th	Night	13% 4 10% 31% 33% 9%	800
	11th to 20th	Night	8% 5% 10% 31% 38% 9%	800
	21st to end	Night	10% 3 13% 33% 34% 6%	880
November	1st to 10th	Night	12% 3 18% 31% 29% 7%	820
	11th to 20th	Night	10% 7% 18% 37% 24% 4	840
	21st to end	Night	10% 5% 21% 37% 23% 3	840
December	1st to 10th	Night	9% 5% 23% 33% 25% 5%	840
	11th to 20th	Night	13% 5% 20% 33% 25% 4	840
	21st to end	Night	11% 5% 22% 34% 25% 3	924

Page generated at 2025-12-30 01:14:07. Version ac07

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