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 2024-01-13.

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% 3 4 4 5% 7% 37%	74571
	Night	19% 8% 3 5% 5% 3 4 4 5% 7% 38%	75156
Transparency	Day	47% 4 11% 22% 14% 2	74277
	Night	47% 4 11% 23% 14% 2	74985
Seeing	Day	27% 16% 31% 18% 7% 2	14561
	Night	25% 14% 31% 23% 6%	23059

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	15% 10% 3 8% 5% 2 5% 4 5% 5% 38%	1517
	11th to 20th	Day	20% 10% 2 6% 5% 3 4 4 4 7% 35%	1456
	21st to end	Day	14% 10% 4 6% 6% 3 4 4 4 6% 40%	1598
February	1st to 10th	Day	17% 11% 3 6% 5% 4 4 5% 5% 6% 35%	1620
	11th to 20th	Day	15% 10% 3 6% 8% 3 5% 5% 5% 5% 36%	1675
	21st to end	Day	13% 9% 3 9% 8% 4 5% 5% 5% 4 35%	1480
March	1st to 10th	Day	17% 11% 3 7% 5% 3 5% 4 3 5% 36%	1801
	11th to 20th	Day	17% 8% 4 5% 5% 4 4 4 4 7% 40%	1980
	21st to end	Day	18% 9% 3 6% 6% 3 5% 4 4 5% 37%	2178
April	1st to 10th	Day	22% 10% 4 6% 6% 3 4 4 4 5% 32%	2150
	11th to 20th	Day	19% 9% 3 5% 5% 3 5% 4 5% 7% 37%	2284
	21st to end	Day	24% 10% 3 5% 6% 2 4 3 4 6% 33%	2340
May	1st to 10th	Day	23% 8% 3 6% 5% 3 4 5% 5% 6% 33%	2340
	11th to 20th	Day	22% 7% 3 6% 6% 3 5% 4 5% 5% 36%	2301
	21st to end	Day	18% 7% 3 5% 5% 3 5% 5% 5% 8% 36%	2787
June	1st to 10th	Day	24% 7% 3 6% 5% 3 5% 5% 5% 7% 30%	2700
	11th to 20th	Day	19% 6% 3 5% 5% 3 5% 5% 5% 7% 37%	2700
	21st to end	Day	23% 7% 3 6% 5% 3 4 5% 5% 8% 29%	2700
July	1st to 10th	Day	16% 5% 2 5% 5% 4 5% 5% 5% 10% 38%	2587
	11th to 20th	Day	13% 7% 2 6% 6% 3 5% 6% 6% 8% 37%	2520
	21st to end	Day	14% 5% 3 6% 6% 3 6% 5% 6% 9% 36%	2719
August	1st to 10th	Day	15% 5% 2 5% 6% 3 5% 5% 6% 9% 38%	2327
	11th to 20th	Day	15% 5% 2 6% 6% 4 5% 5% 6% 8% 38%	2304
	21st to end	Day	14% 6% 2 5% 4 3 5% 5% 5% 8% 44%	2559
September	1st to 10th	Day	12% 5% 2 4 5% 3 5% 4 6% 7% 48%	2079
	11th to 20th	Day	14% 4 2 5% 4 3 4 4 3 5% 53%	1980
	21st to end	Day	17% 6% 2 5% 4 2 3 4 4 8% 44%	1980
October	1st to 10th	Day	17% 7% 2 5% 6% 3 4 4 4 7% 40%	1936
	11th to 20th	Day	20% 6% 2 5% 5% 3 5% 4 4 6% 41%	1778
	21st to end	Day	23% 8% 2 5% 5% 3 4 5% 4 6% 34%	1782
November	1st to 10th	Day	19% 6% 2 5% 5% 3 4 5% 6% 6% 40%	1671
	11th to 20th	Day	20% 6% 2 4 4 3 4 5% 4 7% 41%	1686
	21st to end	Day	21% 8% 2 4 4 2 4 5% 4 5% 42%	1520
December	1st to 10th	Day	21% 11% 3 6% 4 3 4 3 4 6% 34%	1397
	11th to 20th	Day	22% 10% 3 6% 4 2 3 3 4 4 38%	1668
	21st to end	Day	25% 10% 2 5% 5% 3 4 4 4 5% 33%	2471
January	1st to 10th	Night	17% 10% 4 5% 5% 3 4 4 4 6% 37%	2649
	11th to 20th	Night	17% 11% 4 6% 7% 3 4 4 5% 6% 32%	2549
	21st to end	Night	12% 8% 4 7% 5% 4 5% 5% 5% 7% 38%	2756
February	1st to 10th	Night	17% 9% 4 7% 5% 4 6% 5% 5% 7% 32%	2340
	11th to 20th	Night	14% 9% 4 7% 6% 4 4 4 5% 5% 38%	2167
	21st to end	Night	15% 10% 4 5% 6% 3 4 5% 4 6% 37%	1776
March	1st to 10th	Night	15% 12% 4 7% 4 3 4 4 3 6% 37%	2146
	11th to 20th	Night	17% 8% 4 6% 5% 3 5% 5% 5% 6% 34%	1979
	21st to end	Night	18% 9% 3 6% 5% 3 5% 4 5% 5% 38%	2178
April	1st to 10th	Night	22% 10% 4 6% 5% 2 4 4 5% 5% 33%	1809
	11th to 20th	Night	20% 5% 3 7% 5% 3 4 5% 5% 7% 35%	1625
	21st to end	Night	27% 8% 3 4 5% 3 4 4 5% 5% 32%	1620
May	1st to 10th	Night	23% 9% 4 5% 5% 2 4 5% 5% 7% 31%	1620
	11th to 20th	Night	22% 6% 2 6% 7% 3 5% 5% 6% 7% 31%	1593
	21st to end	Night	18% 7% 3 5% 5% 4 5% 5% 5% 8% 35%	1503
June	1st to 10th	Night	22% 8% 3 6% 5% 3 6% 4 5% 7% 30%	1260
	11th to 20th	Night	18% 6% 3 5% 5% 3 4 5% 5% 8% 39%	1260
	21st to end	Night	23% 8% 3 6% 5% 4 4 4 5% 7% 31%	1260
July	1st to 10th	Night	15% 5% 3 5% 5% 4 6% 5% 7% 9% 36%	1369
	11th to 20th	Night	14% 7% 3 6% 5% 3 5% 4 6% 9% 38%	1440
	21st to end	Night	16% 7% 2 6% 6% 3 4 6% 6% 7% 37%	1578
August	1st to 10th	Night	12% 5% 3 5% 5% 4 6% 5% 6% 8% 41%	1612
	11th to 20th	Night	14% 6% 2 5% 7% 3 6% 6% 6% 10% 35%	1596
	21st to end	Night	14% 5% 2 4 4 3 4 4 4 7% 48%	1793
September	1st to 10th	Night	14% 5% 2 3 4 2 4 5% 5% 8% 49%	1880
	11th to 20th	Night	16% 5% 2 3 3 2 3 4 3 6% 52%	1980
	21st to end	Night	16% 6% 2 5% 4 3 4 5% 4 7% 45%	1980
October	1st to 10th	Night	19% 5% 2 5% 5% 4 4 5% 4 7% 40%	2024
	11th to 20th	Night	18% 5% 2 4 5% 4 4 4 5% 7% 42%	2181
	21st to end	Night	24% 9% 3 5% 5% 2 4 4 4 6% 35%	2574
November	1st to 10th	Night	18% 7% 2 5% 5% 3 4 4 4 6% 42%	2407
	11th to 20th	Night	18% 6% 2 4 5% 3 5% 4 5% 7% 40%	2493
	21st to end	Night	18% 8% 3 4 4 3 4 4 6% 6% 40%	2660
December	1st to 10th	Night	22% 10% 3 6% 4 3 4 5% 5% 5% 33%	2778
	11th to 20th	Night	24% 8% 2 5% 4 2 4 3 4 6% 38%	3531
	21st to end	Night	25% 9% 3 4 4 2 3 4 4 6% 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	48% 3 11% 21% 15% 1	1518
	11th to 20th	Day	52% 4 11% 20% 11% 3	1456
	21st to end	Day	47% 3 9% 21% 17% 2	1598
February	1st to 10th	Day	51% 3 11% 19% 14% 2	1620
	11th to 20th	Day	51% 4 10% 20% 14% 2	1683
	21st to end	Day	52% 3 10% 20% 11% 5%	1480
March	1st to 10th	Day	52% 3 10% 18% 15% 3	1804
	11th to 20th	Day	46% 3 8% 20% 17% 5%	1980
	21st to end	Day	50% 4 7% 18% 17% 5%	2178
April	1st to 10th	Day	55% 3 7% 16% 14% 4	2150
	11th to 20th	Day	47% 4 9% 22% 15% 2	2284
	21st to end	Day	54% 3 7% 18% 14% 4	2340
May	1st to 10th	Day	52% 3 6% 20% 15% 3	2340
	11th to 20th	Day	50% 3 7% 22% 16% 2	2305
	21st to end	Day	47% 4 14% 21% 12% 2	2787
June	1st to 10th	Day	54% 4 12% 20% 10% 1	2700
	11th to 20th	Day	47% 4 10% 20% 16% 2	2700
	21st to end	Day	53% 5% 12% 19% 9% 2	2700
July	1st to 10th	Day	41% 5% 14% 26% 12% 1	2517
	11th to 20th	Day	43% 5% 13% 27% 11% 1	2445
	21st to end	Day	44% 5% 14% 25% 11% 1	2567
August	1st to 10th	Day	41% 5% 16% 28% 9%	2314
	11th to 20th	Day	43% 5% 13% 26% 12%	2304
	21st to end	Day	38% 4 12% 27% 17% 2	2559
September	1st to 10th	Day	34% 5% 15% 29% 17% 1	2079
	11th to 20th	Day	35% 3 8% 29% 21% 3	1980
	21st to end	Day	40% 3 10% 28% 18% 1	1980
October	1st to 10th	Day	45% 3 10% 24% 16% 1	1936
	11th to 20th	Day	46% 2 14% 28% 10% 1	1778
	21st to end	Day	52% 3 9% 21% 13% 1	1782
November	1st to 10th	Day	45% 3 14% 23% 15% 2	1671
	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	48% 3 11% 24% 13% 1	2649
	11th to 20th	Night	55% 4 12% 18% 9% 2	2549
	21st to end	Night	46% 3 8% 25% 16% 2	2756
February	1st to 10th	Night	53% 3 11% 19% 12% 2	2340
	11th to 20th	Night	50% 3 9% 20% 16% 2	2170
	21st to end	Night	49% 4 8% 21% 16% 4	1776
March	1st to 10th	Night	50% 4 7% 21% 16% 3	2156
	11th to 20th	Night	51% 3 10% 17% 16% 3	1980
	21st to end	Night	48% 3 7% 20% 18% 3	2178
April	1st to 10th	Night	54% 2 7% 17% 17% 3	1809
	11th to 20th	Night	48% 3 8% 23% 16% 1	1625
	21st to end	Night	53% 3 10% 17% 13% 3	1620
May	1st to 10th	Night	53% 3 8% 20% 14% 2	1620
	11th to 20th	Night	52% 4 9% 21% 12% 2	1594
	21st to end	Night	49% 4 12% 22% 12% 1	1504
June	1st to 10th	Night	54% 4 11% 22% 8% 1	1260
	11th to 20th	Night	44% 3 15% 23% 13% 2	1260
	21st to end	Night	53% 4 12% 20% 8% 2	1260
July	1st to 10th	Night	42% 5% 18% 23% 12%	1329
	11th to 20th	Night	42% 4 16% 27% 11%	1392
	21st to end	Night	45% 5% 16% 24% 9% 1	1490
August	1st to 10th	Night	41% 5% 17% 29% 9%	1600
	11th to 20th	Night	44% 5% 16% 23% 12%	1596
	21st to end	Night	36% 5% 12% 28% 18% 1	1793
September	1st to 10th	Night	34% 5% 14% 33% 15% 1	1880
	11th to 20th	Night	35% 4 10% 30% 19% 2	1980
	21st to end	Night	39% 4 9% 31% 15% 2	1980
October	1st to 10th	Night	45% 3 10% 26% 13% 2	2024
	11th to 20th	Night	43% 3 12% 29% 12% 1	2181
	21st to end	Night	52% 3 11% 21% 13% 1	2574
November	1st to 10th	Night	45% 3 11% 25% 15% 1	2407
	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	37% 18% 28% 13% 2 2	164
	21st to end	Day	28% 22% 33% 15% 3	190
February	1st to 10th	Day	31% 20% 29% 16% 3	340
	11th to 20th	Day	31% 26% 30% 11% 2	382
	21st to end	Day	27% 22% 33% 15% 3	346
March	1st to 10th	Day	32% 21% 32% 13% 2	420
	11th to 20th	Day	28% 22% 33% 13% 3 1	420
	21st to end	Day	32% 22% 27% 12% 5% 3	462
April	1st to 10th	Day	40% 18% 26% 10% 5% 1	420
	11th to 20th	Day	33% 23% 27% 10% 6% 1	412
	21st to end	Day	34% 19% 30% 13% 4 1	420
May	1st to 10th	Day	34% 17% 31% 14% 4	423
	11th to 20th	Day	26% 19% 35% 16% 4 1	447
	21st to end	Day	25% 16% 35% 18% 6% 1	557
June	1st to 10th	Day	29% 12% 30% 20% 8% 1	630
	11th to 20th	Day	24% 14% 28% 23% 10% 1	630
	21st to end	Day	27% 11% 29% 25% 7% 1	630
July	1st to 10th	Day	22% 10% 35% 23% 10% 1	512
	11th to 20th	Day	19% 9% 39% 20% 10% 2	444
	21st to end	Day	14% 11% 38% 27% 9% 2	488
August	1st to 10th	Day	16% 10% 35% 28% 9% 2	446
	11th to 20th	Day	19% 10% 32% 24% 13% 3	439
	21st to end	Day	20% 10% 31% 26% 11% 2	495
September	1st to 10th	Day	14% 11% 35% 26% 11% 3	450
	11th to 20th	Day	23% 12% 30% 17% 12% 7%	450
	21st to end	Day	19% 14% 33% 18% 9% 5%	450
October	1st to 10th	Day	21% 15% 29% 21% 11% 4	428
	11th to 20th	Day	28% 13% 33% 16% 8% 4	360
	21st to end	Day	35% 13% 31% 16% 5% 1	396
November	1st to 10th	Day	28% 15% 27% 22% 7% 2	365
	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	729
	21st to end	Night	21% 21% 33% 21% 3	792
February	1st to 10th	Night	25% 19% 33% 20% 3	720
	11th to 20th	Night	26% 19% 36% 16% 3	703
	21st to end	Night	26% 19% 34% 19% 3	592
March	1st to 10th	Night	26% 17% 36% 19% 1	720
	11th to 20th	Night	25% 19% 32% 18% 5%	720
	21st to end	Night	27% 18% 28% 21% 5% 1	792
April	1st to 10th	Night	32% 15% 31% 18% 3	720
	11th to 20th	Night	24% 18% 33% 20% 5%	561
	21st to end	Night	33% 12% 30% 19% 5%	540
May	1st to 10th	Night	27% 12% 32% 24% 5%	540
	11th to 20th	Night	26% 12% 38% 20% 4	532
	21st to end	Night	22% 10% 33% 28% 7%	414
June	1st to 10th	Night	25% 9% 33% 28% 5%	360
	11th to 20th	Night	21% 8% 31% 31% 10%	360
	21st to end	Night	27% 3 32% 32% 6%	360
July	1st to 10th	Night	19% 3 35% 36% 7%	350
	11th to 20th	Night	15% 3 30% 39% 12% 1	348
	21st to end	Night	20% 3 28% 37% 11% 1	398
August	1st to 10th	Night	15% 4 34% 36% 12%	538
	11th to 20th	Night	16% 5% 29% 36% 13% 1	532
	21st to end	Night	17% 7% 27% 36% 11% 1	605
September	1st to 10th	Night	16% 6% 34% 31% 13% 1	720
	11th to 20th	Night	20% 8% 28% 27% 14% 3	720
	21st to end	Night	19% 9% 31% 27% 12% 2	720
October	1st to 10th	Night	23% 8% 28% 28% 12%	720
	11th to 20th	Night	22% 14% 28% 27% 9% 1	720
	21st to end	Night	30% 15% 30% 19% 6%	792
November	1st to 10th	Night	26% 14% 28% 24% 7% 1	740
	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 2024-01-10 01:24:59. Version ac07

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