Poverty Beach Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poverty Beach Observatory clear sky chart from 2005-11-06 to 2026-03-03.

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% 11% 4 10% 6% 5% 5% 4 5% 7% 28%	131774
	Night	18% 12% 4 10% 6% 5% 5% 4 5% 6% 26%	129538
Transparency	Day	54% 6% 13% 19% 8% 1	135295
	Night	58% 6% 12% 17% 7% 1	134109
Seeing	Day	22% 9% 25% 29% 13% 2	19306
	Night	24% 9% 28% 28% 10% 1	26758

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	12% 17% 8% 20% 9% 6% 4 3 3 5% 13%	4690
	11th to 20th	Day	16% 15% 9% 14% 7% 5% 5% 4 5% 5% 15%	4681
	21st to end	Day	10% 10% 5% 12% 5% 6% 6% 4 5% 7% 31%	5553
February	1st to 10th	Day	16% 14% 5% 11% 5% 6% 5% 4 5% 5% 23%	1890
	11th to 20th	Day	14% 15% 5% 12% 7% 6% 5% 4 4 6% 23%	1843
	21st to end	Day	10% 13% 6% 9% 7% 7% 4 4 5% 7% 29%	1641
March	1st to 10th	Day	18% 12% 4 12% 7% 5% 4 3 4 6% 25%	4714
	11th to 20th	Day	12% 14% 5% 12% 7% 5% 6% 4 5% 7% 23%	4980
	21st to end	Day	20% 17% 5% 14% 7% 5% 4 3 4 5% 17%	5618
April	1st to 10th	Day	20% 12% 4 9% 7% 5% 5% 3 4 5% 27%	2400
	11th to 20th	Day	21% 10% 4 6% 5% 5% 4 3 4 7% 32%	2384
	21st to end	Day	20% 12% 4 8% 5% 3 4 4 5% 6% 30%	2600
May	1st to 10th	Day	25% 14% 3 8% 4 4 3 3 4 5% 26%	6317
	11th to 20th	Day	18% 10% 3 8% 4 4 4 3 5% 7% 34%	6318
	21st to end	Day	17% 10% 3 7% 4 4 4 4 6% 7% 34%	6948
June	1st to 10th	Day	23% 11% 3 7% 4 5% 5% 3 6% 8% 25%	2800
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 3 5% 7% 36%	2818
	21st to end	Day	21% 10% 4 8% 6% 4 4 3 5% 7% 29%	3000
July	1st to 10th	Day	17% 9% 3 8% 5% 5% 6% 5% 6% 8% 28%	6418
	11th to 20th	Day	12% 6% 3 7% 5% 4 5% 4 5% 7% 42%	6360
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 5% 6% 10% 37%	6927
August	1st to 10th	Day	14% 8% 4 9% 6% 5% 5% 5% 7% 8% 29%	4351
	11th to 20th	Day	13% 6% 3 7% 5% 5% 4 4 6% 8% 39%	4175
	21st to end	Day	11% 5% 3 7% 5% 5% 5% 4 6% 8% 43%	4415
September	1st to 10th	Day	14% 7% 2 8% 4 4 4 3 5% 9% 39%	2400
	11th to 20th	Day	16% 8% 3 7% 5% 5% 4 3 5% 7% 36%	2400
	21st to end	Day	17% 6% 2 7% 6% 4 4 3 6% 8% 38%	2096
October	1st to 10th	Day	17% 9% 2 7% 5% 5% 5% 3 6% 6% 35%	2000
	11th to 20th	Day	18% 9% 4 8% 7% 6% 6% 4 7% 7% 25%	2000
	21st to end	Day	19% 13% 4 10% 5% 6% 5% 4 6% 6% 22%	2106
November	1st to 10th	Day	20% 14% 5% 8% 6% 6% 4 3 5% 6% 23%	1735
	11th to 20th	Day	22% 18% 5% 11% 6% 5% 4 3 4 5% 17%	1680
	21st to end	Day	18% 17% 6% 11% 6% 6% 6% 4 5% 6% 16%	1680
December	1st to 10th	Day	17% 13% 8% 17% 7% 6% 5% 4 4 4 16%	2690
	11th to 20th	Day	24% 16% 5% 12% 6% 4 4 2 4 5% 21%	3076
	21st to end	Day	17% 13% 10% 17% 6% 5% 5% 3 5% 4 14%	4070
January	1st to 10th	Night	15% 16% 7% 14% 8% 7% 6% 4 5% 5% 15%	8234
	11th to 20th	Night	19% 14% 7% 14% 6% 6% 4 3 4 4 18%	8234
	21st to end	Night	9% 10% 5% 13% 7% 6% 6% 5% 6% 6% 26%	8622
February	1st to 10th	Night	19% 13% 4 11% 6% 5% 4 3 4 5% 25%	2730
	11th to 20th	Night	16% 14% 5% 12% 6% 6% 5% 4 5% 6% 23%	2663
	21st to end	Night	12% 15% 5% 10% 6% 5% 4 3 5% 6% 28%	2165
March	1st to 10th	Night	21% 13% 5% 10% 6% 5% 4 3 4 5% 24%	5171
	11th to 20th	Night	17% 14% 6% 10% 6% 4 4 3 4 5% 26%	4979
	21st to end	Night	25% 17% 4 10% 5% 5% 4 3 3 4 20%	5313
April	1st to 10th	Night	22% 12% 4 8% 5% 4 4 3 5% 6% 26%	2000
	11th to 20th	Night	22% 11% 3 6% 4 4 3 3 5% 6% 32%	1963
	21st to end	Night	25% 11% 4 7% 5% 4 4 3 4 5% 29%	1800
May	1st to 10th	Night	28% 16% 3 8% 5% 4 4 3 5% 5% 21%	3628
	11th to 20th	Night	17% 10% 3 7% 5% 6% 4 5% 6% 7% 30%	3596
	21st to end	Night	15% 10% 3 8% 5% 5% 5% 5% 5% 8% 32%	3948
June	1st to 10th	Night	26% 10% 3 7% 5% 4 4 3 5% 6% 27%	1600
	11th to 20th	Night	19% 9% 2 5% 4 3 3 4 5% 7% 39%	1590
	21st to end	Night	23% 9% 4 8% 6% 4 5% 3 6% 5% 28%	1400
July	1st to 10th	Night	13% 9% 3 10% 6% 7% 7% 5% 8% 8% 25%	3478
	11th to 20th	Night	11% 8% 2 7% 4 5% 4 4 7% 9% 39%	3620
	21st to end	Night	15% 7% 3 6% 4 4 5% 4 7% 7% 38%	3948
August	1st to 10th	Night	16% 8% 3 8% 5% 5% 6% 5% 7% 7% 31%	2786
	11th to 20th	Night	12% 7% 2 7% 5% 5% 6% 4 6% 8% 38%	2872
	21st to end	Night	12% 5% 2 5% 4 4 4 4 7% 9% 43%	3482
September	1st to 10th	Night	14% 7% 2 5% 5% 4 4 3 6% 7% 43%	2000
	11th to 20th	Night	17% 8% 3 5% 4 4 4 4 4 8% 41%	2000
	21st to end	Night	18% 6% 2 6% 4 5% 5% 3 5% 7% 39%	2300
October	1st to 10th	Night	17% 7% 2 7% 5% 4 4 4 6% 6% 38%	2400
	11th to 20th	Night	18% 8% 3 8% 5% 5% 5% 3 6% 7% 32%	2400
	21st to end	Night	23% 11% 4 9% 5% 5% 4 3 4 6% 26%	2732
November	1st to 10th	Night	18% 13% 4 8% 7% 6% 5% 4 5% 7% 25%	2781
	11th to 20th	Night	23% 14% 4 8% 6% 5% 5% 4 5% 6% 20%	2940
	21st to end	Night	23% 16% 4 10% 6% 5% 5% 4 5% 5% 18%	2940
December	1st to 10th	Night	17% 11% 5% 12% 6% 5% 5% 4 5% 7% 23%	4720
	11th to 20th	Night	23% 13% 5% 13% 6% 5% 4 3 4 4 20%	5353
	21st to end	Night	23% 13% 6% 15% 5% 4 4 3 4 5% 18%	7150

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	75% 5% 11% 5% 4	4691
	11th to 20th	Day	71% 5% 9% 9% 5%	4710
	21st to end	Day	51% 5% 11% 20% 11% 2	5553
February	1st to 10th	Day	60% 5% 13% 13% 8%	1890
	11th to 20th	Day	62% 6% 10% 17% 5% 1	1851
	21st to end	Day	54% 4 14% 16% 11% 2	1641
March	1st to 10th	Day	60% 4 9% 15% 10% 1	4718
	11th to 20th	Day	56% 8% 16% 14% 5% 1	4980
	21st to end	Day	68% 4 8% 13% 5% 1	5618
April	1st to 10th	Day	57% 7% 9% 14% 11% 2	2400
	11th to 20th	Day	52% 6% 10% 20% 11% 1	2384
	21st to end	Day	53% 6% 11% 17% 11% 2	2600
May	1st to 10th	Day	59% 6% 11% 17% 6% 1	6329
	11th to 20th	Day	50% 6% 14% 23% 7%	6322
	21st to end	Day	46% 9% 13% 23% 9%	6948
June	1st to 10th	Day	57% 7% 11% 18% 6% 1	2800
	11th to 20th	Day	47% 6% 13% 23% 9% 1	2818
	21st to end	Day	54% 7% 12% 16% 10% 1	3000
July	1st to 10th	Day	52% 5% 17% 17% 9%	6348
	11th to 20th	Day	41% 5% 16% 29% 8%	6284
	21st to end	Day	42% 6% 20% 26% 6%	6730
August	1st to 10th	Day	50% 8% 14% 22% 6%	4337
	11th to 20th	Day	41% 7% 15% 27% 10%	4214
	21st to end	Day	36% 5% 14% 32% 12%	4415
September	1st to 10th	Day	41% 7% 14% 27% 11%	2400
	11th to 20th	Day	47% 7% 12% 22% 12%	2400
	21st to end	Day	43% 6% 12% 26% 12% 1	2096
October	1st to 10th	Day	51% 5% 14% 23% 8%	3260
	11th to 20th	Day	48% 6% 11% 27% 7%	3240
	21st to end	Day	52% 5% 15% 21% 6%	3388
November	1st to 10th	Day	61% 7% 12% 15% 5%	1735
	11th to 20th	Day	68% 7% 13% 9% 3	1680
	21st to end	Day	68% 8% 14% 7% 3	1680
December	1st to 10th	Day	72% 7% 7% 13% 1	2690
	11th to 20th	Day	68% 5% 10% 9% 7%	3075
	21st to end	Day	70% 6% 12% 9% 3	4070
January	1st to 10th	Night	70% 6% 13% 9% 2	8234
	11th to 20th	Night	71% 5% 10% 10% 5%	8280
	21st to end	Night	55% 5% 11% 15% 13% 1	8622
February	1st to 10th	Night	61% 5% 10% 13% 11% 1	2730
	11th to 20th	Night	63% 5% 11% 13% 7% 1	2666
	21st to end	Night	57% 5% 10% 17% 10% 1	2165
March	1st to 10th	Night	62% 4 5% 14% 12% 2	5180
	11th to 20th	Night	61% 5% 13% 14% 7% 2	4980
	21st to end	Night	69% 4 6% 13% 7% 1	5313
April	1st to 10th	Night	59% 5% 11% 13% 10% 2	2000
	11th to 20th	Night	53% 5% 9% 19% 12% 1	1963
	21st to end	Night	57% 5% 9% 17% 11% 1	1800
May	1st to 10th	Night	67% 3 7% 13% 9%	3633
	11th to 20th	Night	51% 8% 13% 20% 7% 1	3597
	21st to end	Night	49% 8% 16% 23% 4	3949
June	1st to 10th	Night	57% 6% 10% 19% 7%	1600
	11th to 20th	Night	45% 7% 12% 21% 14% 1	1590
	21st to end	Night	56% 6% 14% 14% 9% 1	1400
July	1st to 10th	Night	54% 6% 15% 19% 5% 1	3439
	11th to 20th	Night	40% 7% 17% 25% 10% 1	3572
	21st to end	Night	44% 6% 17% 25% 7%	3831
August	1st to 10th	Night	50% 9% 15% 21% 5%	2775
	11th to 20th	Night	43% 8% 17% 26% 7%	2899
	21st to end	Night	37% 7% 17% 28% 10%	3481
September	1st to 10th	Night	39% 8% 14% 28% 12%	2000
	11th to 20th	Night	42% 6% 13% 26% 13%	2000
	21st to end	Night	44% 7% 12% 26% 11%	2300
October	1st to 10th	Night	52% 5% 12% 21% 9%	3920
	11th to 20th	Night	44% 6% 12% 30% 9%	3899
	21st to end	Night	52% 5% 14% 21% 7%	4405
November	1st to 10th	Night	59% 8% 14% 14% 5%	2781
	11th to 20th	Night	64% 8% 14% 9% 4	2940
	21st to end	Night	69% 8% 14% 7% 2	2940
December	1st to 10th	Night	62% 6% 12% 18% 2	4720
	11th to 20th	Night	68% 5% 10% 12% 4 1	5355
	21st to end	Night	69% 5% 12% 11% 3	7150

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	27% 18% 34% 17% 4	430
	11th to 20th	Day	27% 16% 30% 19% 8%	430
	21st to end	Day	16% 12% 40% 26% 5%	473
February	1st to 10th	Day	25% 15% 31% 23% 7% 1	430
	11th to 20th	Day	22% 15% 35% 24% 5%	426
	21st to end	Day	14% 11% 35% 30% 8% 1	355
March	1st to 10th	Day	20% 12% 33% 28% 6% 1	452
	11th to 20th	Day	17% 8% 35% 29% 9% 1	500
	21st to end	Day	25% 11% 30% 23% 9% 1	550
April	1st to 10th	Day	26% 12% 32% 24% 6%	500
	11th to 20th	Day	23% 7% 33% 26% 9% 2	492
	21st to end	Day	24% 8% 21% 34% 12% 2	500
May	1st to 10th	Day	31% 6% 25% 28% 8% 3	688
	11th to 20th	Day	22% 4 21% 31% 18% 3	724
	21st to end	Day	22% 5% 21% 37% 14% 2	790
June	1st to 10th	Day	30% 6% 16% 32% 14% 2	730
	11th to 20th	Day	18% 4 22% 36% 18% 2	730
	21st to end	Day	26% 5% 18% 29% 18% 4	730
July	1st to 10th	Day	18% 2 15% 40% 23% 2	720
	11th to 20th	Day	14% 3 15% 40% 25% 3	718
	21st to end	Day	17% 3 16% 39% 22% 2	795
August	1st to 10th	Day	14% 2 13% 37% 28% 5%	603
	11th to 20th	Day	18% 4 15% 33% 25% 7%	519
	21st to end	Day	15% 4 21% 29% 28% 4	583
September	1st to 10th	Day	14% 5% 24% 36% 20% 3	530
	11th to 20th	Day	19% 6% 22% 33% 18% 3	530
	21st to end	Day	19% 7% 26% 30% 14% 5%	458
October	1st to 10th	Day	19% 8% 25% 30% 16% 3	420
	11th to 20th	Day	21% 10% 30% 24% 13% 2	420
	21st to end	Day	23% 15% 31% 23% 7% 1	462
November	1st to 10th	Day	26% 14% 33% 19% 7% 1	425
	11th to 20th	Day	33% 15% 29% 17% 5% 1	430
	21st to end	Day	28% 18% 30% 20% 3	430
December	1st to 10th	Day	29% 13% 35% 18% 4	430
	11th to 20th	Day	28% 24% 30% 16% 1	430
	21st to end	Day	22% 19% 36% 17% 4 1	473
January	1st to 10th	Night	27% 16% 34% 19% 4	950
	11th to 20th	Night	26% 14% 31% 22% 6%	950
	21st to end	Night	19% 14% 39% 21% 6% 1	965
February	1st to 10th	Night	27% 10% 32% 26% 5%	840
	11th to 20th	Night	22% 13% 38% 23% 4 1	823
	21st to end	Night	20% 9% 34% 28% 9%	692
March	1st to 10th	Night	22% 10% 36% 26% 6%	809
	11th to 20th	Night	22% 7% 31% 27% 12% 1	800
	21st to end	Night	26% 9% 28% 26% 10% 1	817
April	1st to 10th	Night	29% 9% 29% 26% 7%	600
	11th to 20th	Night	26% 6% 29% 28% 10% 1	594
	21st to end	Night	28% 4 26% 30% 10% 1	600
May	1st to 10th	Night	33% 3 23% 28% 10% 4	600
	11th to 20th	Night	23% 3 22% 33% 15% 3	592
	21st to end	Night	21% 3 27% 38% 10% 2	649
June	1st to 10th	Night	30% 3 18% 39% 10% 1	600
	11th to 20th	Night	22% 3 20% 39% 15% 1	590
	21st to end	Night	26% 4 16% 35% 17% 2	400
July	1st to 10th	Night	17% 2 16% 41% 22% 1	522
	11th to 20th	Night	17% 2 16% 44% 20% 2	582
	21st to end	Night	19% 2 16% 39% 21% 2	656
August	1st to 10th	Night	15% 2 16% 43% 22% 2	598
	11th to 20th	Night	18% 2 18% 37% 23% 2	592
	21st to end	Night	14% 3 20% 37% 24% 2	660
September	1st to 10th	Night	17% 4 24% 36% 18% 2	600
	11th to 20th	Night	22% 6% 19% 38% 13% 2	600
	21st to end	Night	21% 8% 26% 34% 9% 2	770
October	1st to 10th	Night	21% 6% 28% 31% 13% 1	800
	11th to 20th	Night	24% 10% 28% 28% 11% 1	800
	21st to end	Night	31% 13% 31% 20% 5%	932
November	1st to 10th	Night	24% 16% 33% 21% 5% 1	930
	11th to 20th	Night	31% 17% 28% 19% 4 1	950
	21st to end	Night	33% 16% 29% 18% 4	950
December	1st to 10th	Night	29% 16% 34% 15% 6%	950
	11th to 20th	Night	29% 22% 31% 15% 2	950
	21st to end	Night	30% 17% 31% 18% 4 1	1045

Page generated at 2026-02-28 02:40:20. Version ac07

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