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 2024-01-16.

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% 6% 2 5% 5% 3 4 4 5% 7% 41%	74840
	Night	17% 7% 3 5% 5% 3 4 4 5% 7% 40%	74940
Transparency	Day	44% 4 11% 23% 16% 3	74546
	Night	44% 4 11% 22% 16% 2	74768
Seeing	Day	20% 14% 32% 24% 8% 2	13964
	Night	21% 12% 33% 25% 8% 1	22931

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% 5% 3 3 4 5% 7% 42%	1517
	11th to 20th	Day	20% 8% 3 4 4 3 3 4 6% 7% 37%	1480
	21st to end	Day	14% 7% 3 5% 6% 2 4 4 5% 8% 42%	1584
February	1st to 10th	Day	20% 9% 3 5% 5% 3 4 5% 6% 6% 35%	1666
	11th to 20th	Day	15% 7% 3 6% 5% 3 4 4 6% 8% 39%	1748
	21st to end	Day	16% 8% 3 5% 5% 3 6% 4 6% 6% 37%	1480
March	1st to 10th	Day	19% 7% 2 5% 5% 2 5% 4 6% 8% 37%	1797
	11th to 20th	Day	17% 6% 3 5% 6% 3 3 4 5% 7% 40%	1924
	21st to end	Day	18% 8% 2 5% 5% 3 3 3 5% 6% 42%	2253
April	1st to 10th	Day	18% 7% 3 5% 5% 3 5% 4 5% 6% 39%	2160
	11th to 20th	Day	16% 6% 2 5% 4 3 5% 5% 5% 7% 40%	2181
	21st to end	Day	20% 5% 2 5% 4 4 4 6% 5% 7% 37%	2340
May	1st to 10th	Day	23% 7% 2 6% 5% 3 4 4 4 7% 35%	2340
	11th to 20th	Day	16% 6% 3 5% 5% 4 4 4 5% 6% 41%	2301
	21st to end	Day	15% 5% 2 4 5% 2 5% 4 5% 8% 44%	2725
June	1st to 10th	Day	20% 6% 2 5% 5% 3 5% 5% 6% 7% 36%	2520
	11th to 20th	Day	16% 5% 2 5% 5% 3 4 4 5% 9% 41%	2520
	21st to end	Day	16% 5% 2 5% 5% 3 5% 6% 7% 8% 37%	2520
July	1st to 10th	Day	13% 6% 2 5% 4 3 5% 4 7% 8% 44%	2520
	11th to 20th	Day	10% 6% 2 5% 5% 3 5% 5% 6% 10% 42%	2520
	21st to end	Day	10% 4 2 5% 5% 3 5% 6% 7% 10% 43%	2740
August	1st to 10th	Day	9% 4 2 5% 6% 4 6% 7% 7% 9% 43%	2327
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 6% 6% 8% 42%	2304
	21st to end	Day	13% 3 1 4 3 3 4 6% 7% 9% 48%	2404
September	1st to 10th	Day	13% 6% 2 4 4 2 4 4 5% 8% 48%	2129
	11th to 20th	Day	14% 6% 2 3 3 3 3 3 4 6% 54%	1980
	21st to end	Day	16% 5% 2 4 4 3 4 4 5% 7% 47%	1980
October	1st to 10th	Day	23% 5% 3 5% 4 2 3 4 4 6% 42%	1980
	11th to 20th	Day	16% 4 2 4 4 2 4 4 6% 7% 46%	1762
	21st to end	Day	21% 6% 2 4 5% 2 4 5% 4 6% 41%	1782
November	1st to 10th	Day	16% 6% 3 4 4 2 4 3 4 5% 48%	1671
	11th to 20th	Day	18% 7% 2 4 4 2 3 4 4 7% 45%	1710
	21st to end	Day	19% 6% 2 4 4 3 3 4 5% 7% 43%	1710
December	1st to 10th	Day	20% 7% 3 5% 5% 2 5% 4 5% 5% 40%	1587
	11th to 20th	Day	23% 7% 2 4 4 2 3 4 3 6% 42%	1906
	21st to end	Day	23% 9% 3 5% 5% 3 4 4 4 6% 33%	2772
January	1st to 10th	Night	17% 8% 3 4 4 3 4 4 4 8% 41%	2649
	11th to 20th	Night	20% 9% 3 6% 5% 3 5% 4 6% 6% 33%	2591
	21st to end	Night	15% 8% 3 6% 5% 3 4 4 5% 8% 38%	2772
February	1st to 10th	Night	17% 9% 2 6% 6% 4 4 5% 5% 6% 36%	2286
	11th to 20th	Night	16% 10% 3 6% 6% 3 4 4 5% 6% 39%	2098
	21st to end	Night	18% 8% 3 4 5% 3 3 4 4 6% 43%	1776
March	1st to 10th	Night	16% 9% 3 6% 5% 3 4 4 5% 5% 41%	2150
	11th to 20th	Night	18% 8% 4 6% 6% 3 5% 4 5% 5% 37%	2034
	21st to end	Night	19% 7% 3 5% 5% 3 4 3 4 4 42%	2102
April	1st to 10th	Night	19% 9% 3 5% 4 3 5% 5% 5% 6% 36%	1800
	11th to 20th	Night	19% 7% 3 5% 4 3 4 4 5% 6% 41%	1727
	21st to end	Night	20% 7% 2 6% 5% 4 5% 4 4 6% 35%	1620
May	1st to 10th	Night	23% 8% 3 5% 5% 3 4 4 5% 6% 33%	1620
	11th to 20th	Night	18% 7% 2 5% 4 3 6% 7% 6% 7% 35%	1593
	21st to end	Night	19% 7% 3 5% 5% 3 4 4 4 7% 39%	1563
June	1st to 10th	Night	21% 7% 3 6% 6% 4 4 4 4 6% 37%	1440
	11th to 20th	Night	18% 7% 3 5% 4 3 4 4 6% 8% 37%	1440
	21st to end	Night	17% 6% 2 5% 5% 3 4 5% 6% 8% 38%	1440
July	1st to 10th	Night	15% 6% 3 5% 6% 3 5% 5% 6% 9% 39%	1440
	11th to 20th	Night	11% 6% 4 5% 5% 4 5% 6% 7% 8% 39%	1440
	21st to end	Night	14% 5% 3 5% 4 3 5% 4 5% 8% 43%	1574
August	1st to 10th	Night	9% 5% 2 5% 6% 3 5% 7% 6% 9% 44%	1596
	11th to 20th	Night	12% 7% 2 5% 6% 5% 5% 6% 6% 9% 37%	1596
	21st to end	Night	13% 6% 2 5% 3 3 4 5% 5% 8% 46%	1948
September	1st to 10th	Night	12% 6% 2 6% 4 3 4 4 5% 8% 47%	1830
	11th to 20th	Night	14% 5% 2 4 3 2 3 4 3 6% 53%	1980
	21st to end	Night	15% 5% 2 5% 5% 3 3 4 6% 7% 45%	1980
October	1st to 10th	Night	21% 5% 2 6% 5% 3 4 3 5% 6% 40%	1980
	11th to 20th	Night	15% 5% 2 6% 5% 3 4 5% 5% 7% 44%	2194
	21st to end	Night	23% 7% 3 5% 4 3 3 5% 4 6% 38%	2574
November	1st to 10th	Night	15% 5% 2 5% 5% 3 4 4 5% 6% 47%	2407
	11th to 20th	Night	16% 7% 2 5% 4 3 4 3 4 6% 45%	2470
	21st to end	Night	17% 6% 4 4 4 3 3 4 6% 6% 43%	2470
December	1st to 10th	Night	19% 8% 3 6% 5% 3 4 4 4 5% 38%	2588
	11th to 20th	Night	19% 7% 2 4 4 2 4 4 6% 7% 39%	3288
	21st to end	Night	22% 9% 3 6% 4 2 4 4 4 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	44% 3 10% 26% 15% 2	1518
	11th to 20th	Day	45% 5% 13% 21% 13% 3	1480
	21st to end	Day	42% 3 12% 25% 16% 3	1584
February	1st to 10th	Day	50% 3 12% 18% 14% 2	1666
	11th to 20th	Day	45% 5% 11% 21% 14% 3	1757
	21st to end	Day	50% 4 10% 20% 14% 3	1480
March	1st to 10th	Day	45% 4 12% 21% 14% 5%	1800
	11th to 20th	Day	45% 3 11% 21% 17% 4	1924
	21st to end	Day	47% 4 7% 19% 16% 7%	2253
April	1st to 10th	Day	48% 3 9% 19% 17% 4	2160
	11th to 20th	Day	44% 4 10% 22% 16% 4	2181
	21st to end	Day	49% 5% 8% 19% 17% 3	2340
May	1st to 10th	Day	53% 4 7% 20% 14% 2	2340
	11th to 20th	Day	45% 5% 9% 20% 18% 3	2305
	21st to end	Day	39% 5% 16% 24% 14% 2	2725
June	1st to 10th	Day	49% 6% 11% 22% 12% 1	2520
	11th to 20th	Day	44% 4 12% 21% 17% 2	2520
	21st to end	Day	45% 6% 12% 24% 11% 1	2520
July	1st to 10th	Day	39% 6% 12% 24% 17% 2	2450
	11th to 20th	Day	39% 5% 13% 28% 13% 1	2445
	21st to end	Day	38% 6% 14% 25% 14% 3	2587
August	1st to 10th	Day	39% 7% 14% 25% 13% 1	2314
	11th to 20th	Day	40% 6% 13% 25% 14% 1	2304
	21st to end	Day	36% 5% 11% 26% 19% 2	2404
September	1st to 10th	Day	36% 5% 12% 26% 21% 1	2129
	11th to 20th	Day	36% 3 8% 27% 23% 2	1980
	21st to end	Day	39% 4 9% 24% 22% 2	1980
October	1st to 10th	Day	47% 4 10% 22% 14% 4	1980
	11th to 20th	Day	39% 3 11% 30% 15% 2	1762
	21st to end	Day	47% 4 11% 21% 14% 3	1782
November	1st to 10th	Day	40% 3 11% 27% 16% 3	1671
	11th to 20th	Day	42% 4 9% 23% 21% 3	1710
	21st to end	Day	43% 4 15% 22% 15% 2	1710
December	1st to 10th	Day	48% 3 14% 17% 17% 1	1587
	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	43% 3 11% 25% 16% 2	2649
	11th to 20th	Night	50% 4 14% 20% 9% 3	2591
	21st to end	Night	45% 3 9% 21% 19% 3	2772
February	1st to 10th	Night	48% 4 12% 20% 14% 3	2286
	11th to 20th	Night	47% 4 10% 21% 15% 4	2100
	21st to end	Night	44% 3 8% 25% 16% 4	1776
March	1st to 10th	Night	45% 3 9% 22% 16% 5%	2160
	11th to 20th	Night	49% 3 9% 17% 17% 4	2035
	21st to end	Night	47% 3 8% 17% 20% 5%	2102
April	1st to 10th	Night	49% 3 10% 17% 17% 4	1800
	11th to 20th	Night	45% 3 8% 22% 19% 3	1727
	21st to end	Night	49% 4 10% 18% 16% 3	1620
May	1st to 10th	Night	54% 4 8% 18% 14% 3	1620
	11th to 20th	Night	45% 6% 13% 18% 16% 3	1594
	21st to end	Night	46% 5% 14% 21% 13% 1	1564
June	1st to 10th	Night	50% 4 12% 23% 12%	1440
	11th to 20th	Night	45% 5% 13% 21% 15% 2	1440
	21st to end	Night	41% 7% 14% 23% 14% 1	1440
July	1st to 10th	Night	42% 4 14% 23% 15% 1	1400
	11th to 20th	Night	41% 6% 14% 27% 10% 1	1392
	21st to end	Night	37% 6% 13% 29% 12% 2	1486
August	1st to 10th	Night	35% 7% 16% 26% 15% 2	1585
	11th to 20th	Night	43% 7% 14% 21% 14% 1	1596
	21st to end	Night	36% 4 11% 26% 21% 1	1948
September	1st to 10th	Night	38% 4 12% 26% 19% 1	1830
	11th to 20th	Night	35% 3 9% 25% 26% 2	1980
	21st to end	Night	38% 5% 8% 26% 21% 2	1980
October	1st to 10th	Night	46% 3 11% 23% 13% 4	1980
	11th to 20th	Night	40% 3 13% 29% 14% 1	2194
	21st to end	Night	48% 4 12% 21% 15% 2	2574
November	1st to 10th	Night	39% 4 11% 23% 19% 3	2407
	11th to 20th	Night	41% 3 10% 23% 19% 3	2470
	21st to end	Night	41% 3 13% 26% 14% 2	2470
December	1st to 10th	Night	49% 3 12% 22% 13% 1	2588
	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	22% 29% 31% 15% 4 1	170
	21st to end	Day	19% 27% 36% 14% 5%	176
February	1st to 10th	Day	30% 20% 34% 15% 1	351
	11th to 20th	Day	24% 24% 38% 13% 2	416
	21st to end	Day	22% 20% 37% 17% 4	346
March	1st to 10th	Day	22% 18% 39% 18% 3	420
	11th to 20th	Day	22% 23% 38% 14% 3 1	420
	21st to end	Day	24% 20% 35% 14% 6% 2	462
April	1st to 10th	Day	24% 24% 27% 18% 6% 1	420
	11th to 20th	Day	21% 19% 38% 17% 5%	412
	21st to end	Day	27% 15% 34% 20% 3 1	420
May	1st to 10th	Day	30% 17% 32% 16% 5% 1	423
	11th to 20th	Day	17% 15% 38% 26% 4 1	447
	21st to end	Day	18% 9% 34% 29% 9% 1	485
June	1st to 10th	Day	20% 8% 34% 25% 11% 1	450
	11th to 20th	Day	15% 11% 38% 27% 7% 2	450
	21st to end	Day	18% 7% 34% 30% 8% 2	450
July	1st to 10th	Day	17% 5% 26% 35% 13% 3	445
	11th to 20th	Day	14% 7% 28% 34% 15% 3	444
	21st to end	Day	11% 4 29% 43% 11% 1	488
August	1st to 10th	Day	11% 6% 28% 39% 13% 3	446
	11th to 20th	Day	15% 6% 26% 33% 17% 4	439
	21st to end	Day	15% 6% 26% 33% 15% 4	495
September	1st to 10th	Day	18% 6% 26% 30% 16% 3	450
	11th to 20th	Day	19% 11% 28% 22% 13% 7%	450
	21st to end	Day	18% 9% 31% 26% 11% 5%	450
October	1st to 10th	Day	26% 11% 25% 23% 12% 3	450
	11th to 20th	Day	19% 16% 27% 25% 12% 2	383
	21st to end	Day	26% 12% 36% 17% 9% 1	396
November	1st to 10th	Day	17% 13% 36% 23% 10% 2	365
	11th to 20th	Day	25% 21% 29% 20% 5% 1	370
	21st to end	Day	25% 18% 31% 18% 7% 1	370
December	1st to 10th	Day	22% 19% 40% 14% 5%	247
	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% 37% 17% 3	741
	21st to end	Night	20% 18% 39% 19% 4	792
February	1st to 10th	Night	24% 18% 36% 21% 2	720
	11th to 20th	Night	23% 18% 42% 15% 3	703
	21st to end	Night	25% 17% 35% 20% 3	592
March	1st to 10th	Night	23% 17% 38% 19% 3	720
	11th to 20th	Night	23% 16% 38% 18% 4	720
	21st to end	Night	23% 16% 34% 21% 6%	792
April	1st to 10th	Night	25% 16% 34% 22% 4	720
	11th to 20th	Night	23% 13% 35% 21% 6%	663
	21st to end	Night	24% 12% 33% 27% 4 1	540
May	1st to 10th	Night	27% 9% 34% 23% 6% 1	540
	11th to 20th	Night	22% 10% 37% 24% 6% 1	532
	21st to end	Night	22% 6% 30% 30% 11%	402
June	1st to 10th	Night	23% 4 31% 30% 10% 2	360
	11th to 20th	Night	21% 6% 28% 35% 9% 1	360
	21st to end	Night	19% 5% 28% 38% 10%	360
July	1st to 10th	Night	17% 2 24% 43% 12% 2	350
	11th to 20th	Night	14% 4 22% 41% 18% 1	348
	21st to end	Night	15% 2 25% 44% 13% 1	394
August	1st to 10th	Night	10% 3 24% 45% 16% 1	522
	11th to 20th	Night	14% 4 25% 39% 18% 1	532
	21st to end	Night	16% 3 23% 36% 20% 2	760
September	1st to 10th	Night	15% 4 28% 35% 18% 1	720
	11th to 20th	Night	16% 7% 26% 28% 19% 4	720
	21st to end	Night	19% 5% 27% 31% 16% 3	720
October	1st to 10th	Night	25% 8% 26% 25% 13% 2	720
	11th to 20th	Night	18% 11% 31% 26% 12% 1	720
	21st to end	Night	26% 11% 33% 23% 6% 1	792
November	1st to 10th	Night	16% 11% 36% 26% 9% 1	740
	11th to 20th	Night	22% 17% 34% 21% 7% 1	760
	21st to end	Night	21% 21% 34% 18% 6% 1	760
December	1st to 10th	Night	24% 17% 39% 16% 4	760
	11th to 20th	Night	22% 19% 35% 21% 3	760
	21st to end	Night	26% 16% 38% 18% 2	836

Page generated at 2024-01-13 01:38:14. Version ac07

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