Nealey's Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nealey's Corner clear sky chart from 2005-11-06 to 2024-11-10.

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	18% 8% 3 6% 5% 4 4 4 5% 7% 36%	101235
	Night	18% 9% 3 6% 4 4 4 4 5% 6% 36%	97928
Transparency	Day	48% 4 11% 22% 13% 2	104761
	Night	48% 4 12% 23% 13% 2	102492
Seeing	Day	27% 16% 31% 18% 7% 2	15721
	Night	25% 14% 31% 24% 6%	24058

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% 9% 3 8% 4 4 4 3 5% 5% 40%	2517
	11th to 20th	Day	17% 8% 2 7% 5% 3 3 3 3 6% 42%	2520
	21st to end	Day	16% 11% 4 8% 4 4 4 4 4 6% 36%	2800
February	1st to 10th	Day	17% 11% 3 7% 5% 4 4 3 5% 6% 35%	1710
	11th to 20th	Day	14% 11% 3 7% 7% 5% 5% 3 5% 4 37%	1770
	21st to end	Day	13% 10% 2 10% 7% 5% 4 4 6% 4 36%	1570
March	1st to 10th	Day	25% 13% 3 7% 4 4 4 3 3 4 30%	3134
	11th to 20th	Day	18% 12% 3 7% 5% 5% 4 3 4 6% 33%	3480
	21st to end	Day	26% 9% 3 7% 4 4 4 3 6% 6% 29%	3816
April	1st to 10th	Day	22% 12% 3 7% 5% 3 3 4 4 5% 32%	2270
	11th to 20th	Day	19% 9% 2 5% 4 4 4 3 5% 7% 37%	2413
	21st to end	Day	23% 10% 3 6% 6% 4 3 3 4 6% 34%	2470
May	1st to 10th	Day	21% 9% 2 7% 5% 4 5% 4 6% 7% 31%	4106
	11th to 20th	Day	18% 9% 2 8% 5% 5% 5% 4 6% 7% 32%	4081
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 6% 8% 36%	4955
June	1st to 10th	Day	23% 7% 3 7% 5% 4 5% 3 5% 7% 30%	2850
	11th to 20th	Day	19% 7% 2 6% 5% 4 5% 4 5% 7% 36%	2850
	21st to end	Day	24% 8% 3 6% 5% 4 5% 4 5% 8% 29%	2850
July	1st to 10th	Day	14% 6% 2 6% 5% 5% 6% 5% 7% 10% 35%	4549
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 5% 7% 8% 37%	4440
	21st to end	Day	17% 7% 3 7% 5% 4 4 4 5% 8% 36%	4763
August	1st to 10th	Day	17% 7% 3 8% 5% 5% 5% 4 6% 8% 33%	4105
	11th to 20th	Day	16% 9% 3 7% 5% 5% 4 4 5% 7% 34%	4045
	21st to end	Day	11% 6% 2 5% 3 4 5% 4 7% 8% 43%	4503
September	1st to 10th	Day	11% 5% 2 4 4 3 4 3 6% 7% 49%	2194
	11th to 20th	Day	13% 4 2 5% 4 3 4 3 4 5% 53%	2090
	21st to end	Day	16% 6% 3 6% 3 3 4 4 4 8% 43%	2090
October	1st to 10th	Day	17% 8% 2 6% 5% 4 5% 3 4 7% 39%	2043
	11th to 20th	Day	19% 6% 2 5% 4 5% 5% 3 4 6% 42%	1876
	21st to end	Day	22% 9% 2 6% 4 4 4 3 4 6% 35%	1881
November	1st to 10th	Day	18% 6% 2 6% 4 4 4 4 6% 6% 40%	1752
	11th to 20th	Day	20% 7% 2 5% 3 4 4 4 5% 7% 41%	1686
	21st to end	Day	21% 9% 2 4 4 3 4 4 3 5% 42%	1520
December	1st to 10th	Day	21% 12% 2 7% 4 4 4 2 5% 5% 34%	1397
	11th to 20th	Day	22% 11% 2 6% 4 3 4 2 4 4 38%	1668
	21st to end	Day	25% 10% 2 6% 4 4 4 3 4 5% 33%	2471
January	1st to 10th	Night	15% 10% 3 7% 5% 4 4 3 5% 6% 39%	4429
	11th to 20th	Night	14% 9% 4 8% 6% 5% 4 3 5% 6% 37%	4440
	21st to end	Night	17% 11% 4 9% 5% 4 4 4 5% 6% 32%	4854
February	1st to 10th	Night	15% 10% 4 8% 5% 5% 5% 4 5% 6% 33%	2470
	11th to 20th	Night	13% 9% 3 8% 6% 5% 4 3 5% 5% 38%	2291
	21st to end	Night	15% 12% 3 7% 5% 4 4 4 4 6% 37%	1884
March	1st to 10th	Night	29% 13% 3 6% 3 4 3 3 3 5% 30%	3706
	11th to 20th	Night	15% 11% 3 9% 5% 5% 6% 5% 6% 6% 28%	3479
	21st to end	Night	26% 9% 2 7% 4 4 4 4 7% 5% 26%	3816
April	1st to 10th	Night	22% 11% 3 6% 4 3 4 3 5% 5% 34%	1909
	11th to 20th	Night	20% 7% 2 7% 5% 4 4 4 6% 7% 34%	1716
	21st to end	Night	26% 8% 3 5% 4 3 3 4 5% 5% 34%	1710
May	1st to 10th	Night	24% 9% 2 5% 3 3 3 4 5% 8% 33%	2834
	11th to 20th	Night	18% 7% 3 8% 6% 5% 5% 4 7% 8% 29%	2813
	21st to end	Night	15% 6% 2 7% 4 4 4 4 6% 9% 38%	2640
June	1st to 10th	Night	21% 9% 3 7% 4 4 5% 4 5% 7% 31%	1330
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 4 6% 8% 39%	1330
	21st to end	Night	24% 9% 3 6% 4 5% 3 4 6% 6% 30%	1330
July	1st to 10th	Night	12% 6% 3 7% 6% 6% 6% 6% 8% 9% 33%	2410
	11th to 20th	Night	14% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	2520
	21st to end	Night	14% 7% 2 6% 4 4 4 4 6% 8% 40%	2756
August	1st to 10th	Night	18% 9% 3 8% 5% 5% 6% 4 6% 7% 30%	2825
	11th to 20th	Night	16% 9% 3 7% 6% 4 6% 5% 6% 8% 31%	2782
	21st to end	Night	10% 6% 3 6% 4 5% 5% 3 6% 7% 45%	3149
September	1st to 10th	Night	13% 5% 1 4 3 3 4 4 5% 7% 49%	1985
	11th to 20th	Night	16% 6% 2 4 3 3 3 3 4 6% 52%	2090
	21st to end	Night	16% 7% 2 6% 3 3 4 4 4 7% 44%	2090
October	1st to 10th	Night	18% 5% 2 6% 4 4 4 4 4 7% 40%	2137
	11th to 20th	Night	18% 6% 2 5% 4 4 4 3 5% 7% 43%	2303
	21st to end	Night	23% 9% 2 5% 4 3 4 3 4 5% 37%	2717
November	1st to 10th	Night	17% 7% 2 6% 4 4 3 3 5% 6% 42%	2531
	11th to 20th	Night	18% 6% 2 5% 5% 4 4 3 5% 7% 40%	2493
	21st to end	Night	18% 9% 3 4 3 4 4 4 6% 6% 40%	2660
December	1st to 10th	Night	22% 11% 2 6% 4 3 4 4 5% 5% 33%	2778
	11th to 20th	Night	24% 8% 2 5% 4 4 3 3 4 6% 38%	3531
	21st to end	Night	24% 10% 3 5% 4 3 3 3 4 5% 36%	5190

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	47% 3 14% 25% 10% 1	2518
	11th to 20th	Day	45% 4 10% 27% 12% 2	2520
	21st to end	Day	51% 2 14% 19% 14% 1	2800
February	1st to 10th	Day	50% 3 11% 19% 14% 2	1710
	11th to 20th	Day	50% 4 9% 21% 15% 2	1778
	21st to end	Day	51% 3 10% 21% 10% 5%	1570
March	1st to 10th	Day	60% 2 7% 13% 14% 3	3137
	11th to 20th	Day	53% 3 9% 19% 13% 3	3480
	21st to end	Day	57% 2 4 16% 16% 4	3816
April	1st to 10th	Day	55% 3 7% 16% 14% 4	2270
	11th to 20th	Day	47% 4 9% 23% 15% 2	2413
	21st to end	Day	53% 3 7% 19% 15% 4	2470
May	1st to 10th	Day	53% 4 12% 20% 10% 2	4120
	11th to 20th	Day	52% 4 13% 20% 10% 1	4085
	21st to end	Day	46% 4 15% 20% 15% 1	4955
June	1st to 10th	Day	54% 3 12% 21% 9% 1	2850
	11th to 20th	Day	47% 4 11% 20% 15% 2	2850
	21st to end	Day	53% 5% 11% 19% 9% 2	2850
July	1st to 10th	Day	43% 5% 14% 26% 12%	4479
	11th to 20th	Day	42% 6% 14% 27% 11% 1	4365
	21st to end	Day	47% 5% 11% 24% 13% 1	4611
August	1st to 10th	Day	49% 5% 14% 26% 6%	4092
	11th to 20th	Day	48% 6% 15% 22% 8%	4084
	21st to end	Day	36% 5% 12% 27% 18% 1	4503
September	1st to 10th	Day	33% 4 14% 29% 19% 1	2194
	11th to 20th	Day	35% 3 9% 29% 21% 3	2090
	21st to end	Day	41% 3 10% 28% 18% 1	2090
October	1st to 10th	Day	54% 4 8% 21% 12% 1	3394
	11th to 20th	Day	36% 2 10% 32% 19% 1	3092
	21st to end	Day	37% 3 15% 24% 19% 2	3081
November	1st to 10th	Day	45% 3 13% 23% 14% 2	1752
	11th to 20th	Day	44% 3 9% 23% 17% 3	1686
	21st to end	Day	46% 3 16% 24% 11% 1	1520
December	1st to 10th	Day	54% 3 10% 22% 11% 1	1397
	11th to 20th	Day	52% 3 9% 19% 15% 3	1668
	21st to end	Day	55% 2 11% 21% 8% 3	2471
January	1st to 10th	Night	47% 3 13% 26% 10% 1	4429
	11th to 20th	Night	49% 3 13% 21% 12% 3	4440
	21st to end	Night	54% 3 9% 21% 12% 1	4854
February	1st to 10th	Night	52% 3 11% 19% 12% 2	2470
	11th to 20th	Night	49% 3 9% 21% 16% 2	2294
	21st to end	Night	49% 4 8% 21% 15% 4	1884
March	1st to 10th	Night	60% 2 7% 16% 11% 3	3716
	11th to 20th	Night	55% 3 12% 18% 10% 2	3480
	21st to end	Night	58% 2 5% 17% 16% 2	3816
April	1st to 10th	Night	53% 2 7% 17% 17% 3	1909
	11th to 20th	Night	48% 3 8% 24% 15% 1	1716
	21st to end	Night	51% 3 10% 17% 15% 3	1710
May	1st to 10th	Night	50% 3 17% 21% 8% 1	2840
	11th to 20th	Night	52% 4 15% 21% 7% 1	2814
	21st to end	Night	43% 4 18% 23% 12% 1	2641
June	1st to 10th	Night	53% 3 12% 23% 8% 1	1330
	11th to 20th	Night	44% 4 16% 22% 12% 2	1330
	21st to end	Night	54% 4 12% 19% 8% 3	1330
July	1st to 10th	Night	45% 6% 16% 22% 12%	2370
	11th to 20th	Night	44% 5% 15% 28% 9%	2472
	21st to end	Night	41% 6% 15% 27% 11% 1	2668
August	1st to 10th	Night	53% 6% 14% 21% 7%	2813
	11th to 20th	Night	48% 5% 16% 20% 10%	2809
	21st to end	Night	37% 6% 13% 25% 17% 1	3149
September	1st to 10th	Night	34% 5% 13% 33% 15% 1	1985
	11th to 20th	Night	34% 4 11% 31% 19% 2	2090
	21st to end	Night	40% 5% 9% 30% 15% 1	2090
October	1st to 10th	Night	44% 5% 13% 24% 13% 1	3566
	11th to 20th	Night	34% 3 9% 33% 20% 1	3826
	21st to end	Night	40% 3 11% 29% 15% 2	4467
November	1st to 10th	Night	44% 3 12% 26% 15% 1	2531
	11th to 20th	Night	44% 4 9% 24% 17% 2	2493
	21st to end	Night	44% 4 14% 21% 15% 2	2660
December	1st to 10th	Night	53% 3 9% 22% 12%	2778
	11th to 20th	Night	49% 3 8% 22% 17% 1	3532
	21st to end	Night	52% 2 13% 20% 12% 2	5190

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	34% 13% 33% 17% 3	180
	11th to 20th	Day	38% 18% 28% 12% 2 2	180
	21st to end	Day	28% 21% 32% 16% 3	213
February	1st to 10th	Day	30% 20% 29% 17% 4	370
	11th to 20th	Day	30% 26% 31% 11% 2	417
	21st to end	Day	28% 21% 33% 15% 4	382
March	1st to 10th	Day	33% 20% 31% 13% 2	460
	11th to 20th	Day	29% 22% 33% 13% 3 1	460
	21st to end	Day	34% 21% 27% 11% 4 2	506
April	1st to 10th	Day	40% 18% 27% 10% 5% 1	460
	11th to 20th	Day	33% 23% 27% 10% 6% 1	452
	21st to end	Day	33% 19% 30% 13% 4 1	460
May	1st to 10th	Day	34% 16% 31% 14% 4 1	463
	11th to 20th	Day	25% 18% 34% 18% 5% 1	487
	21st to end	Day	25% 16% 35% 18% 6%	605
June	1st to 10th	Day	28% 13% 30% 20% 8% 1	680
	11th to 20th	Day	24% 14% 28% 23% 11% 1	680
	21st to end	Day	28% 11% 30% 24% 6% 1	680
July	1st to 10th	Day	21% 11% 36% 22% 9% 1	555
	11th to 20th	Day	18% 10% 40% 20% 10% 1	484
	21st to end	Day	15% 11% 38% 25% 9% 2	532
August	1st to 10th	Day	16% 10% 36% 28% 9% 1	486
	11th to 20th	Day	20% 10% 32% 24% 12% 2	479
	21st to end	Day	20% 10% 31% 26% 11% 3	539
September	1st to 10th	Day	14% 12% 35% 25% 11% 3	490
	11th to 20th	Day	22% 11% 28% 19% 12% 8%	490
	21st to end	Day	18% 14% 33% 19% 10% 5%	490
October	1st to 10th	Day	21% 15% 29% 20% 11% 3	465
	11th to 20th	Day	28% 13% 32% 17% 7% 4	390
	21st to end	Day	34% 13% 31% 17% 5% 1	429
November	1st to 10th	Day	29% 15% 27% 21% 6% 2	392
	11th to 20th	Day	31% 16% 32% 15% 6% 1	370
	21st to end	Day	33% 16% 26% 20% 4 1	370
December	1st to 10th	Day	31% 20% 30% 14% 4	247
	11th to 20th	Day	36% 27% 26% 8% 2 1	180
	21st to end	Day	40% 19% 21% 15% 4 1	198
January	1st to 10th	Night	27% 19% 32% 19% 3	760
	11th to 20th	Night	28% 19% 31% 18% 4	760
	21st to end	Night	22% 20% 34% 20% 3 1	836
February	1st to 10th	Night	25% 19% 33% 21% 3	760
	11th to 20th	Night	24% 21% 36% 15% 3	743
	21st to end	Night	26% 18% 34% 19% 3	628
March	1st to 10th	Night	28% 16% 35% 19% 1	760
	11th to 20th	Night	25% 19% 32% 19% 5%	760
	21st to end	Night	28% 18% 28% 21% 5%	836
April	1st to 10th	Night	32% 15% 31% 18% 3	760
	11th to 20th	Night	24% 18% 34% 19% 5%	592
	21st to end	Night	32% 12% 31% 19% 5%	570
May	1st to 10th	Night	27% 11% 32% 24% 5%	570
	11th to 20th	Night	25% 11% 37% 21% 5%	562
	21st to end	Night	22% 10% 33% 29% 6%	437
June	1st to 10th	Night	24% 9% 32% 29% 6%	380
	11th to 20th	Night	21% 7% 31% 31% 10%	380
	21st to end	Night	28% 4 32% 31% 6%	380
July	1st to 10th	Night	18% 3 36% 36% 7%	370
	11th to 20th	Night	15% 3 30% 39% 12% 1	368
	21st to end	Night	20% 3 28% 37% 11% 1	421
August	1st to 10th	Night	16% 4 33% 35% 11%	568
	11th to 20th	Night	16% 5% 29% 36% 12% 1	562
	21st to end	Night	17% 7% 27% 36% 12% 1	639
September	1st to 10th	Night	16% 6% 34% 31% 13% 1	760
	11th to 20th	Night	19% 8% 27% 28% 15% 3	760
	21st to end	Night	19% 9% 31% 28% 12% 2	760
October	1st to 10th	Night	23% 8% 28% 28% 13%	760
	11th to 20th	Night	21% 14% 27% 27% 9% 1	760
	21st to end	Night	29% 15% 31% 20% 5%	836
November	1st to 10th	Night	25% 14% 29% 24% 7% 1	779
	11th to 20th	Night	26% 14% 31% 21% 7% 1	771
	21st to end	Night	28% 18% 29% 20% 4	850
December	1st to 10th	Night	29% 15% 32% 18% 5%	850
	11th to 20th	Night	28% 22% 30% 17% 3	850
	21st to end	Night	31% 21% 28% 16% 3	920

Page generated at 2024-11-07 06:55:47. Version ac07

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