Halibut Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halibut Point clear sky chart from 2005-11-06 to 2024-12-06.

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% 7% 2 6% 4 4 4 4 5% 7% 40%	101475
	Night	18% 8% 2 6% 4 4 4 4 5% 7% 38%	98240
Transparency	Day	44% 4 11% 23% 15% 2	105027
	Night	45% 4 11% 22% 16% 2	102777
Seeing	Day	20% 14% 32% 23% 8% 2	15168
	Night	21% 12% 33% 25% 8% 1	24035

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% 7% 3 5% 3 4 3 3 5% 6% 45%	2517
	11th to 20th	Day	17% 8% 3 7% 3 3 3 4 5% 6% 41%	2520
	21st to end	Day	21% 10% 3 6% 5% 4 4 3 4 6% 35%	2772
February	1st to 10th	Day	19% 9% 3 6% 4 4 4 5% 5% 6% 35%	1758
	11th to 20th	Day	14% 7% 3 7% 4 3 5% 4 6% 8% 40%	1848
	21st to end	Day	16% 9% 3 6% 5% 4 5% 3 6% 6% 37%	1570
March	1st to 10th	Day	25% 12% 2 6% 4 4 4 3 4 5% 30%	3116
	11th to 20th	Day	14% 8% 2 6% 4 4 4 3 6% 7% 41%	3382
	21st to end	Day	25% 8% 2 5% 4 3 4 3 5% 5% 35%	3959
April	1st to 10th	Day	18% 8% 3 6% 5% 4 4 3 5% 6% 38%	2280
	11th to 20th	Day	16% 7% 2 6% 4 4 5% 4 5% 7% 40%	2304
	21st to end	Day	19% 5% 2 6% 4 5% 4 5% 5% 7% 38%	2470
May	1st to 10th	Day	21% 11% 3 7% 5% 4 4 3 5% 7% 30%	4106
	11th to 20th	Day	21% 9% 3 8% 5% 4 4 3 5% 6% 33%	4081
	21st to end	Day	15% 5% 2 5% 4 3 4 3 5% 8% 45%	4837
June	1st to 10th	Day	19% 7% 2 6% 4 4 5% 4 6% 7% 37%	2660
	11th to 20th	Day	15% 6% 1 6% 5% 4 4 4 6% 9% 41%	2660
	21st to end	Day	16% 5% 2 6% 5% 4 5% 5% 7% 7% 37%	2660
July	1st to 10th	Day	11% 7% 3 7% 4 5% 5% 4 8% 9% 36%	4440
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 4 7% 10% 42%	4440
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 9% 39%	4797
August	1st to 10th	Day	13% 6% 3 6% 5% 5% 5% 5% 6% 8% 37%	4105
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 6% 7% 40%	4045
	21st to end	Day	7% 3 1 4 3 5% 5% 5% 8% 10% 48%	4222
September	1st to 10th	Day	13% 6% 2 4 4 3 4 4 5% 7% 49%	2247
	11th to 20th	Day	14% 6% 1 4 2 3 3 2 4 6% 54%	2090
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 7% 45%	2090
October	1st to 10th	Day	22% 5% 2 6% 3 3 4 3 4 6% 42%	2090
	11th to 20th	Day	16% 4 2 5% 3 3 4 3 6% 7% 47%	1859
	21st to end	Day	20% 6% 2 5% 4 3 4 4 4 6% 42%	1881
November	1st to 10th	Day	16% 7% 2 5% 4 3 3 3 4 5% 48%	1761
	11th to 20th	Day	17% 7% 2 5% 3 2 3 3 4 6% 47%	1800
	21st to end	Day	20% 6% 2 4 4 3 3 4 5% 7% 42%	1800
December	1st to 10th	Day	19% 8% 3 6% 4 3 5% 3 5% 5% 40%	1630
	11th to 20th	Day	23% 7% 2 5% 4 3 3 3 3 6% 42%	1906
	21st to end	Day	23% 10% 3 6% 4 3 4 3 4 6% 33%	2772
January	1st to 10th	Night	19% 7% 2 4 3 3 3 3 4 7% 45%	4429
	11th to 20th	Night	16% 8% 3 9% 5% 4 4 3 5% 5% 38%	4440
	21st to end	Night	22% 12% 3 8% 5% 4 4 3 4 6% 29%	4884
February	1st to 10th	Night	16% 10% 2 7% 5% 4 4 4 6% 6% 36%	2414
	11th to 20th	Night	15% 10% 3 6% 5% 4 4 3 5% 6% 39%	2218
	21st to end	Night	17% 9% 3 5% 4 3 3 3 4 6% 43%	1884
March	1st to 10th	Night	30% 10% 2 5% 3 3 3 3 4 4 33%	3724
	11th to 20th	Night	13% 9% 3 7% 6% 5% 5% 4 5% 6% 37%	3576
	21st to end	Night	26% 7% 3 6% 4 4 4 3 5% 4 33%	3672
April	1st to 10th	Night	19% 9% 3 6% 4 4 4 4 4 6% 36%	1900
	11th to 20th	Night	19% 9% 2 5% 4 4 3 3 5% 6% 40%	1824
	21st to end	Night	19% 7% 2 7% 5% 5% 4 3 5% 5% 37%	1710
May	1st to 10th	Night	22% 12% 3 8% 5% 4 4 3 5% 7% 27%	2834
	11th to 20th	Night	21% 9% 2 7% 5% 5% 6% 5% 6% 7% 26%	2813
	21st to end	Night	18% 7% 3 6% 4 3 4 4 5% 7% 40%	2751
June	1st to 10th	Night	20% 8% 2 6% 5% 5% 4 3 4 6% 36%	1520
	11th to 20th	Night	18% 8% 3 5% 3 4 4 4 6% 9% 37%	1520
	21st to end	Night	18% 7% 2 6% 4 4 4 4 6% 8% 37%	1520
July	1st to 10th	Night	10% 6% 3 8% 6% 5% 6% 5% 7% 10% 35%	2520
	11th to 20th	Night	8% 6% 3 7% 5% 5% 5% 6% 7% 9% 39%	2520
	21st to end	Night	16% 9% 3 8% 4 5% 4 4 5% 8% 35%	2739
August	1st to 10th	Night	17% 7% 3 9% 5% 5% 5% 5% 6% 8% 32%	2809
	11th to 20th	Night	11% 8% 3 8% 5% 6% 5% 5% 7% 9% 33%	2782
	21st to end	Night	9% 5% 2 5% 3 4 4 4 6% 8% 50%	3430
September	1st to 10th	Night	12% 6% 1 6% 4 4 3 4 5% 7% 48%	1932
	11th to 20th	Night	14% 5% 1 5% 3 3 3 3 3 6% 53%	2090
	21st to end	Night	16% 5% 2 5% 4 4 4 3 6% 7% 43%	2090
October	1st to 10th	Night	20% 5% 2 7% 4 4 4 3 5% 6% 40%	2090
	11th to 20th	Night	15% 5% 2 7% 4 4 4 4 5% 7% 46%	2317
	21st to end	Night	22% 7% 3 6% 3 4 4 3 4 6% 39%	2717
November	1st to 10th	Night	15% 5% 2 6% 4 4 4 3 5% 6% 48%	2537
	11th to 20th	Night	16% 7% 2 5% 4 4 4 2 5% 6% 46%	2600
	21st to end	Night	17% 7% 3 5% 4 3 3 3 5% 6% 43%	2600
December	1st to 10th	Night	19% 9% 3 6% 4 4 4 3 4 5% 38%	2662
	11th to 20th	Night	19% 8% 2 5% 4 3 4 3 6% 7% 39%	3288
	21st to end	Night	22% 9% 3 6% 3 3 3 3 5% 6% 36%	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	42% 3 9% 33% 12% 1	2518
	11th to 20th	Day	45% 3 11% 25% 13% 2	2520
	21st to end	Day	52% 3 10% 23% 10% 1	2772
February	1st to 10th	Day	48% 4 12% 20% 14% 2	1758
	11th to 20th	Day	45% 5% 11% 21% 16% 3	1857
	21st to end	Day	49% 3 11% 20% 14% 3	1570
March	1st to 10th	Day	57% 4 9% 16% 12% 3	3119
	11th to 20th	Day	41% 3 14% 23% 15% 3	3382
	21st to end	Day	52% 3 5% 16% 15% 8%	3959
April	1st to 10th	Day	50% 3 9% 18% 17% 4	2280
	11th to 20th	Day	44% 4 10% 22% 16% 4	2304
	21st to end	Day	48% 5% 7% 20% 18% 3	2470
May	1st to 10th	Day	57% 5% 11% 16% 10% 1	4120
	11th to 20th	Day	53% 4 15% 16% 10% 2	4085
	21st to end	Day	38% 4 13% 24% 19% 2	4837
June	1st to 10th	Day	48% 6% 11% 23% 12% 1	2660
	11th to 20th	Day	43% 4 13% 21% 16% 2	2660
	21st to end	Day	46% 6% 12% 23% 12% 1	2660
July	1st to 10th	Day	44% 5% 12% 22% 16% 1	4370
	11th to 20th	Day	39% 4 15% 27% 14% 1	4365
	21st to end	Day	46% 5% 13% 22% 13% 2	4644
August	1st to 10th	Day	46% 6% 16% 23% 8% 1	4092
	11th to 20th	Day	44% 5% 13% 26% 10% 1	4084
	21st to end	Day	32% 5% 13% 31% 18% 2	4222
September	1st to 10th	Day	36% 4 11% 25% 22% 1	2247
	11th to 20th	Day	36% 2 8% 28% 23% 3	2090
	21st to end	Day	41% 4 8% 23% 21% 2	2090
October	1st to 10th	Day	44% 3 9% 24% 18% 2	3480
	11th to 20th	Day	32% 2 7% 30% 25% 3	3062
	21st to end	Day	34% 3 9% 30% 21% 3	3081
November	1st to 10th	Day	39% 3 11% 27% 16% 2	1761
	11th to 20th	Day	40% 3 8% 22% 24% 3	1800
	21st to end	Day	43% 4 14% 23% 15% 2	1800
December	1st to 10th	Day	47% 3 14% 18% 17% 1	1630
	11th to 20th	Day	45% 3 11% 18% 17% 6%	1906
	21st to end	Day	53% 3 11% 21% 11% 1	2772
January	1st to 10th	Night	40% 3 12% 29% 12% 3	4429
	11th to 20th	Night	47% 4 11% 22% 13% 3	4440
	21st to end	Night	57% 2 9% 18% 11% 2	4884
February	1st to 10th	Night	47% 4 13% 20% 14% 3	2414
	11th to 20th	Night	45% 4 10% 21% 16% 4	2220
	21st to end	Night	44% 3 8% 26% 15% 4	1884
March	1st to 10th	Night	56% 3 9% 18% 12% 3	3734
	11th to 20th	Night	47% 4 11% 18% 17% 3	3577
	21st to end	Night	53% 3 6% 14% 17% 7%	3672
April	1st to 10th	Night	50% 3 10% 17% 17% 3	1900
	11th to 20th	Night	46% 3 8% 21% 19% 3	1824
	21st to end	Night	48% 3 10% 18% 17% 3	1710
May	1st to 10th	Night	58% 4 12% 16% 8% 2	2840
	11th to 20th	Night	55% 5% 16% 14% 9% 2	2814
	21st to end	Night	43% 4 15% 20% 16% 1	2752
June	1st to 10th	Night	49% 4 12% 23% 12%	1520
	11th to 20th	Night	43% 5% 13% 21% 15% 2	1520
	21st to end	Night	43% 7% 13% 22% 14% 1	1520
July	1st to 10th	Night	45% 4 13% 22% 15% 1	2480
	11th to 20th	Night	41% 5% 16% 23% 15% 1	2472
	21st to end	Night	47% 5% 11% 21% 14% 1	2651
August	1st to 10th	Night	50% 6% 13% 20% 11% 1	2798
	11th to 20th	Night	46% 7% 14% 22% 11%	2809
	21st to end	Night	30% 4 15% 27% 23% 1	3430
September	1st to 10th	Night	37% 4 12% 26% 20% 1	1932
	11th to 20th	Night	35% 3 9% 25% 26% 2	2090
	21st to end	Night	41% 5% 8% 25% 20% 2	2090
October	1st to 10th	Night	43% 3 13% 24% 15% 2	3480
	11th to 20th	Night	28% 2 10% 29% 28% 3	3853
	21st to end	Night	35% 3 11% 31% 19% 2	4467
November	1st to 10th	Night	38% 4 11% 24% 20% 4	2537
	11th to 20th	Night	40% 3 9% 22% 21% 4	2600
	21st to end	Night	42% 3 13% 26% 14% 2	2600
December	1st to 10th	Night	48% 3 11% 23% 13% 1	2662
	11th to 20th	Night	44% 4 13% 18% 20% 1	3288
	21st to end	Night	50% 4 8% 25% 11% 1	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	24% 22% 29% 20% 4	180
	11th to 20th	Day	21% 29% 32% 14% 3 1	180
	21st to end	Day	20% 25% 36% 15% 4	198
February	1st to 10th	Day	27% 20% 36% 16% 2	383
	11th to 20th	Day	23% 25% 37% 13% 2	456
	21st to end	Day	22% 20% 36% 17% 5%	382
March	1st to 10th	Day	23% 18% 38% 17% 3	460
	11th to 20th	Day	21% 25% 36% 14% 3 1	460
	21st to end	Day	26% 20% 34% 13% 6% 2	506
April	1st to 10th	Day	25% 24% 27% 18% 6% 1	460
	11th to 20th	Day	22% 19% 37% 17% 4	452
	21st to end	Day	24% 14% 37% 21% 3 1	460
May	1st to 10th	Day	28% 18% 33% 16% 5% 1	463
	11th to 20th	Day	18% 14% 37% 26% 5% 1	487
	21st to end	Day	18% 9% 34% 30% 8% 1	529
June	1st to 10th	Day	20% 9% 33% 26% 11% 1	490
	11th to 20th	Day	14% 11% 38% 28% 7% 2	490
	21st to end	Day	19% 9% 35% 28% 8% 2	490
July	1st to 10th	Day	17% 6% 28% 33% 13% 3	485
	11th to 20th	Day	14% 7% 29% 34% 14% 2	484
	21st to end	Day	12% 5% 31% 41% 11% 1	532
August	1st to 10th	Day	12% 6% 29% 37% 12% 3	486
	11th to 20th	Day	15% 7% 27% 31% 16% 4	479
	21st to end	Day	14% 6% 27% 32% 16% 4	539
September	1st to 10th	Day	17% 7% 28% 29% 15% 4	490
	11th to 20th	Day	19% 10% 27% 22% 13% 9%	490
	21st to end	Day	19% 8% 32% 25% 11% 5%	490
October	1st to 10th	Day	24% 12% 25% 23% 12% 3	490
	11th to 20th	Day	20% 15% 27% 24% 11% 2	415
	21st to end	Day	26% 11% 37% 17% 9% 1	429
November	1st to 10th	Day	17% 14% 36% 22% 9% 2	395
	11th to 20th	Day	25% 21% 31% 19% 4 1	400
	21st to end	Day	27% 19% 30% 17% 7% 1	400
December	1st to 10th	Day	21% 19% 39% 16% 5%	260
	11th to 20th	Day	24% 23% 38% 12% 2	180
	21st to end	Day	22% 24% 32% 16% 5% 2	198
January	1st to 10th	Night	21% 19% 40% 18% 3	760
	11th to 20th	Night	26% 18% 36% 17% 3	760
	21st to end	Night	20% 18% 39% 19% 4	836
February	1st to 10th	Night	23% 17% 36% 22% 2	760
	11th to 20th	Night	22% 18% 42% 15% 3	743
	21st to end	Night	24% 18% 34% 21% 4	628
March	1st to 10th	Night	25% 16% 37% 19% 3	760
	11th to 20th	Night	22% 17% 38% 18% 4	760
	21st to end	Night	25% 15% 34% 20% 5%	836
April	1st to 10th	Night	25% 16% 34% 22% 4	760
	11th to 20th	Night	23% 15% 35% 21% 6%	700
	21st to end	Night	22% 13% 34% 27% 4 1	570
May	1st to 10th	Night	27% 9% 34% 24% 6% 1	570
	11th to 20th	Night	22% 9% 36% 25% 6% 1	562
	21st to end	Night	22% 6% 30% 31% 11%	424
June	1st to 10th	Night	23% 4 31% 30% 9% 2	380
	11th to 20th	Night	20% 6% 29% 35% 9% 1	380
	21st to end	Night	21% 5% 28% 37% 9%	380
July	1st to 10th	Night	17% 2 25% 42% 11% 2	370
	11th to 20th	Night	14% 5% 22% 40% 17% 1	368
	21st to end	Night	15% 3 25% 43% 13%	416
August	1st to 10th	Night	12% 3 24% 44% 16% 1	552
	11th to 20th	Night	14% 4 26% 38% 17% 1	562
	21st to end	Night	15% 3 23% 36% 20% 2	803
September	1st to 10th	Night	14% 4 28% 34% 17% 1	760
	11th to 20th	Night	16% 6% 25% 29% 19% 5%	760
	21st to end	Night	19% 5% 27% 31% 16% 3	760
October	1st to 10th	Night	24% 8% 26% 26% 14% 2	760
	11th to 20th	Night	18% 11% 31% 26% 12% 1	760
	21st to end	Night	25% 12% 33% 23% 7%	836
November	1st to 10th	Night	16% 12% 37% 26% 8% 1	780
	11th to 20th	Night	21% 18% 34% 20% 7% 1	800
	21st to end	Night	22% 20% 34% 18% 6% 1	800
December	1st to 10th	Night	24% 17% 39% 16% 4	783
	11th to 20th	Night	22% 19% 35% 21% 3	760
	21st to end	Night	26% 16% 38% 18% 2	836

Page generated at 2024-12-03 06:45:11. Version ac07

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