Port Chester
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Chester 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	16% 6% 2 5% 5% 3 4 5% 5% 7% 41%	74772
	Night	17% 6% 3 5% 4 3 4 4 5% 7% 42%	74950
Transparency	Day	41% 6% 13% 23% 15% 2	74477
	Night	42% 6% 12% 23% 16% 2	74779
Seeing	Day	18% 12% 30% 25% 12% 3	13881
	Night	20% 12% 31% 27% 9% 1	23105

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% 6% 2 4 5% 3 4 5% 5% 6% 43%	1517
	11th to 20th	Day	16% 8% 3 5% 5% 3 5% 5% 7% 6% 37%	1456
	21st to end	Day	14% 7% 3 5% 4 3 4 5% 5% 8% 41%	1692
February	1st to 10th	Day	18% 7% 3 6% 4 3 6% 5% 4 7% 38%	1647
	11th to 20th	Day	15% 6% 2 6% 5% 3 4 4 4 6% 44%	1748
	21st to end	Day	20% 9% 3 5% 4 3 4 4 4 6% 38%	1480
March	1st to 10th	Day	14% 6% 3 4 5% 3 4 5% 5% 7% 44%	1797
	11th to 20th	Day	15% 6% 2 4 6% 4 5% 5% 7% 8% 38%	1868
	21st to end	Day	21% 8% 3 5% 5% 3 3 4 4 6% 40%	2374
April	1st to 10th	Day	18% 8% 3 5% 4 3 4 4 5% 7% 40%	2160
	11th to 20th	Day	17% 6% 3 5% 5% 2 5% 4 5% 7% 41%	2134
	21st to end	Day	20% 6% 2 4 5% 3 4 4 6% 6% 41%	2205
May	1st to 10th	Day	23% 7% 3 5% 4 2 4 4 5% 7% 35%	2340
	11th to 20th	Day	19% 6% 2 5% 4 3 5% 5% 6% 7% 37%	2437
	21st to end	Day	16% 5% 2 4 5% 3 5% 5% 5% 9% 42%	2725
June	1st to 10th	Day	18% 5% 2 5% 5% 3 5% 4 7% 9% 36%	2520
	11th to 20th	Day	16% 6% 3 5% 5% 3 4 5% 6% 9% 38%	2520
	21st to end	Day	12% 6% 2 6% 5% 3 5% 5% 6% 10% 40%	2520
July	1st to 10th	Day	11% 6% 2 5% 5% 3 5% 6% 7% 9% 40%	2520
	11th to 20th	Day	11% 6% 2 6% 4 3 4 5% 7% 10% 42%	2520
	21st to end	Day	13% 6% 2 6% 5% 4 6% 6% 7% 8% 38%	2744
August	1st to 10th	Day	10% 6% 2 6% 6% 3 5% 5% 8% 9% 40%	2389
	11th to 20th	Day	13% 5% 2 5% 6% 4 5% 6% 5% 10% 39%	2126
	21st to end	Day	12% 5% 2 5% 5% 3 4 6% 5% 9% 43%	2376
September	1st to 10th	Day	13% 6% 2 5% 5% 3 4 5% 5% 7% 44%	2160
	11th to 20th	Day	14% 4 2 4 4 2 3 3 5% 7% 51%	2066
	21st to end	Day	17% 5% 2 5% 5% 3 4 4 5% 6% 42%	1980
October	1st to 10th	Day	22% 7% 2 4 3 3 3 4 4 6% 42%	1905
	11th to 20th	Day	16% 5% 2 5% 4 3 4 4 5% 7% 46%	1800
	21st to end	Day	21% 6% 2 4 4 3 4 5% 5% 6% 40%	1814
November	1st to 10th	Day	14% 6% 2 4 4 3 3 4 4 6% 50%	1671
	11th to 20th	Day	19% 6% 2 3 2 2 4 4 4 7% 47%	1710
	21st to end	Day	15% 5% 3 5% 4 2 4 5% 5% 6% 45%	1653
December	1st to 10th	Day	19% 6% 3 5% 6% 4 4 4 6% 7% 37%	1520
	11th to 20th	Day	23% 5% 2 4 3 2 3 3 5% 5% 45%	1906
	21st to end	Day	18% 9% 3 7% 7% 3 5% 5% 5% 6% 33%	2772
January	1st to 10th	Night	16% 6% 2 5% 4 2 4 3 5% 6% 46%	2649
	11th to 20th	Night	20% 7% 3 5% 5% 3 4 4 5% 7% 39%	2549
	21st to end	Night	14% 9% 3 4 3 3 4 4 5% 7% 45%	2663
February	1st to 10th	Night	18% 9% 3 5% 5% 3 4 4 4 5% 41%	2311
	11th to 20th	Night	18% 7% 3 6% 4 3 4 4 4 6% 41%	2098
	21st to end	Night	20% 6% 2 5% 5% 3 4 3 5% 5% 41%	1776
March	1st to 10th	Night	17% 6% 2 5% 3 2 5% 4 4 7% 45%	2150
	11th to 20th	Night	17% 6% 2 5% 5% 3 4 5% 5% 7% 41%	2087
	21st to end	Night	18% 7% 3 5% 4 2 5% 4 5% 6% 41%	1981
April	1st to 10th	Night	18% 8% 3 5% 5% 3 4 4 5% 7% 39%	1800
	11th to 20th	Night	20% 6% 2 6% 5% 2 4 4 5% 7% 41%	1775
	21st to end	Night	20% 6% 3 6% 5% 2 3 4 3 6% 41%	1752
May	1st to 10th	Night	22% 7% 3 5% 6% 3 4 4 4 7% 35%	1620
	11th to 20th	Night	20% 7% 3 4 5% 4 3 5% 5% 6% 37%	1470
	21st to end	Night	18% 6% 2 5% 5% 3 4 4 5% 7% 42%	1550
June	1st to 10th	Night	19% 5% 2 4 5% 2 5% 5% 5% 8% 41%	1440
	11th to 20th	Night	14% 7% 3 4 5% 2 4 5% 6% 9% 40%	1440
	21st to end	Night	12% 4 2 5% 5% 2 5% 5% 7% 9% 44%	1440
July	1st to 10th	Night	12% 5% 3 6% 6% 4 6% 5% 6% 9% 38%	1440
	11th to 20th	Night	13% 5% 3 5% 4 4 6% 5% 6% 9% 40%	1440
	21st to end	Night	13% 4 3 5% 4 3 5% 5% 7% 10% 42%	1574
August	1st to 10th	Night	9% 5% 3 5% 6% 3 5% 5% 6% 8% 44%	1528
	11th to 20th	Night	12% 6% 3 6% 7% 4 5% 6% 6% 9% 37%	1774
	21st to end	Night	14% 5% 2 4 5% 3 4 5% 6% 8% 44%	1980
September	1st to 10th	Night	15% 5% 2 5% 5% 3 6% 4 5% 7% 44%	1800
	11th to 20th	Night	15% 5% 2 4 3 2 3 4 5% 5% 52%	1894
	21st to end	Night	17% 6% 3 5% 3 3 4 3 4 6% 46%	1980
October	1st to 10th	Night	21% 6% 2 6% 4 3 4 3 3 5% 42%	2052
	11th to 20th	Night	16% 5% 3 4 5% 3 3 3 5% 6% 48%	2160
	21st to end	Night	22% 7% 2 5% 4 2 3 3 4 6% 41%	2542
November	1st to 10th	Night	13% 5% 2 4 4 3 4 4 5% 6% 50%	2407
	11th to 20th	Night	21% 5% 2 4 3 2 3 3 4 6% 47%	2470
	21st to end	Night	16% 4 3 4 4 3 4 4 6% 7% 47%	2526
December	1st to 10th	Night	20% 7% 3 5% 4 3 4 3 5% 6% 39%	2660
	11th to 20th	Night	20% 6% 2 4 4 3 4 4 5% 6% 42%	3288
	21st to end	Night	21% 8% 3 5% 4 3 4 4 5% 6% 37%	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	39% 5% 11% 27% 14% 4	1518
	11th to 20th	Day	45% 6% 14% 21% 13% 2	1456
	21st to end	Day	41% 5% 12% 25% 14% 3	1692
February	1st to 10th	Day	46% 6% 12% 22% 13% 2	1647
	11th to 20th	Day	41% 5% 10% 25% 17% 3	1757
	21st to end	Day	46% 4 10% 23% 14% 3	1480
March	1st to 10th	Day	39% 4 15% 24% 15% 3	1800
	11th to 20th	Day	41% 6% 13% 24% 14% 2	1868
	21st to end	Day	46% 4 8% 19% 18% 5%	2374
April	1st to 10th	Day	43% 5% 10% 21% 16% 4	2160
	11th to 20th	Day	40% 6% 12% 21% 18% 3	2134
	21st to end	Day	42% 6% 11% 21% 16% 4	2205
May	1st to 10th	Day	46% 6% 11% 20% 16% 2	2340
	11th to 20th	Day	42% 7% 12% 21% 15% 3	2441
	21st to end	Day	38% 8% 18% 20% 14% 2	2725
June	1st to 10th	Day	41% 8% 14% 22% 14% 1	2520
	11th to 20th	Day	41% 8% 13% 23% 12% 2	2520
	21st to end	Day	38% 8% 15% 23% 15% 1	2520
July	1st to 10th	Day	37% 10% 13% 23% 16% 2	2450
	11th to 20th	Day	34% 9% 17% 25% 14% 2	2445
	21st to end	Day	39% 9% 13% 20% 17% 3	2591
August	1st to 10th	Day	37% 8% 17% 25% 13% 1	2375
	11th to 20th	Day	38% 7% 15% 25% 13% 1	2126
	21st to end	Day	36% 7% 13% 23% 19% 2	2376
September	1st to 10th	Day	38% 6% 15% 22% 17% 2	2160
	11th to 20th	Day	32% 5% 12% 24% 24% 2	2066
	21st to end	Day	42% 5% 11% 20% 19% 3	1980
October	1st to 10th	Day	42% 6% 10% 23% 16% 2	1905
	11th to 20th	Day	38% 5% 13% 25% 17% 2	1800
	21st to end	Day	45% 5% 9% 22% 16% 3	1814
November	1st to 10th	Day	35% 5% 12% 24% 21% 2	1671
	11th to 20th	Day	39% 4 10% 23% 21% 4	1710
	21st to end	Day	39% 4 14% 28% 12% 3	1653
December	1st to 10th	Day	45% 5% 15% 19% 14% 1	1520
	11th to 20th	Day	42% 4 15% 24% 14% 2	1906
	21st to end	Day	51% 7% 10% 23% 9% 1	2772
January	1st to 10th	Night	40% 3 12% 25% 16% 4	2649
	11th to 20th	Night	44% 6% 14% 23% 10% 2	2549
	21st to end	Night	39% 5% 10% 24% 19% 3	2663
February	1st to 10th	Night	46% 4 13% 23% 13% 2	2311
	11th to 20th	Night	45% 5% 10% 20% 16% 5%	2100
	21st to end	Night	44% 4 7% 25% 16% 3	1776
March	1st to 10th	Night	39% 4 13% 24% 16% 4	2160
	11th to 20th	Night	43% 5% 10% 21% 16% 4	2088
	21st to end	Night	44% 5% 9% 19% 18% 5%	1981
April	1st to 10th	Night	46% 4 10% 19% 17% 3	1800
	11th to 20th	Night	43% 5% 10% 19% 21% 2	1775
	21st to end	Night	44% 6% 9% 21% 16% 4	1752
May	1st to 10th	Night	50% 5% 11% 16% 14% 2	1620
	11th to 20th	Night	47% 5% 11% 17% 17% 2	1471
	21st to end	Night	42% 8% 15% 21% 11% 2	1551
June	1st to 10th	Night	43% 7% 10% 20% 18% 2	1440
	11th to 20th	Night	40% 6% 16% 26% 12% 1	1440
	21st to end	Night	35% 8% 16% 25% 15% 1	1440
July	1st to 10th	Night	41% 9% 15% 20% 14% 2	1400
	11th to 20th	Night	39% 8% 15% 26% 11% 1	1392
	21st to end	Night	34% 8% 17% 23% 15% 3	1486
August	1st to 10th	Night	36% 8% 17% 23% 15% 2	1518
	11th to 20th	Night	41% 9% 15% 24% 10% 1	1774
	21st to end	Night	37% 8% 13% 22% 19% 2	1980
September	1st to 10th	Night	40% 7% 11% 25% 16% 1	1800
	11th to 20th	Night	34% 4 11% 24% 23% 3	1894
	21st to end	Night	41% 4 9% 22% 21% 3	1980
October	1st to 10th	Night	45% 6% 11% 22% 13% 3	2052
	11th to 20th	Night	37% 5% 12% 29% 16% 1	2160
	21st to end	Night	45% 4 11% 22% 16% 1	2542
November	1st to 10th	Night	36% 5% 11% 23% 20% 4	2407
	11th to 20th	Night	40% 3 9% 25% 19% 4	2470
	21st to end	Night	37% 4 13% 30% 14% 2	2526
December	1st to 10th	Night	45% 5% 13% 21% 15% 1	2660
	11th to 20th	Night	43% 5% 13% 19% 18% 3	3288
	21st to end	Night	47% 6% 12% 22% 12% 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	22% 28% 27% 19% 4 1	180
	11th to 20th	Day	16% 29% 36% 16% 3	164
	21st to end	Day	17% 18% 43% 15% 5% 1	224
February	1st to 10th	Day	28% 18% 37% 15% 2	267
	11th to 20th	Day	22% 19% 41% 17% 2	416
	21st to end	Day	24% 23% 34% 16% 3	346
March	1st to 10th	Day	15% 25% 36% 20% 5%	420
	11th to 20th	Day	18% 21% 38% 19% 3 1	420
	21st to end	Day	24% 18% 35% 17% 5% 1	462
April	1st to 10th	Day	21% 21% 35% 15% 7% 1	420
	11th to 20th	Day	20% 15% 32% 20% 11% 1	412
	21st to end	Day	26% 16% 34% 18% 5% 1	420
May	1st to 10th	Day	30% 13% 31% 18% 7% 2	423
	11th to 20th	Day	18% 13% 34% 26% 7% 2	447
	21st to end	Day	19% 6% 26% 28% 18% 4	485
June	1st to 10th	Day	17% 8% 27% 30% 16% 2	450
	11th to 20th	Day	16% 9% 29% 32% 12% 2	450
	21st to end	Day	13% 7% 26% 32% 18% 4	450
July	1st to 10th	Day	13% 5% 21% 35% 20% 7%	445
	11th to 20th	Day	10% 3 22% 35% 25% 5%	444
	21st to end	Day	13% 6% 21% 38% 21% 2	488
August	1st to 10th	Day	10% 4 24% 36% 20% 7%	446
	11th to 20th	Day	15% 5% 16% 38% 22% 4	439
	21st to end	Day	11% 4 28% 32% 16% 9%	495
September	1st to 10th	Day	17% 5% 27% 25% 19% 6%	450
	11th to 20th	Day	14% 5% 30% 25% 16% 10%	450
	21st to end	Day	20% 7% 29% 25% 15% 4	450
October	1st to 10th	Day	26% 8% 24% 23% 14% 5%	450
	11th to 20th	Day	16% 14% 28% 27% 14% 1	450
	21st to end	Day	25% 13% 31% 22% 8% 1	412
November	1st to 10th	Day	16% 14% 29% 27% 11% 3	365
	11th to 20th	Day	21% 19% 34% 19% 6% 1	370
	21st to end	Day	18% 17% 35% 23% 7% 1	313
December	1st to 10th	Day	19% 22% 36% 17% 6% 1	180
	11th to 20th	Day	26% 27% 32% 13% 2	180
	21st to end	Day	26% 17% 36% 14% 7% 1	198
January	1st to 10th	Night	20% 18% 39% 20% 3	760
	11th to 20th	Night	23% 16% 35% 22% 4	729
	21st to end	Night	18% 19% 41% 20% 2	792
February	1st to 10th	Night	23% 15% 39% 21% 2	720
	11th to 20th	Night	22% 20% 38% 18% 1	703
	21st to end	Night	23% 19% 35% 20% 3	592
March	1st to 10th	Night	21% 15% 39% 21% 4	720
	11th to 20th	Night	22% 15% 38% 21% 4 1	720
	21st to end	Night	21% 15% 37% 22% 5%	792
April	1st to 10th	Night	22% 15% 35% 22% 6%	720
	11th to 20th	Night	19% 14% 34% 27% 6%	711
	21st to end	Night	23% 11% 33% 25% 6% 1	672
May	1st to 10th	Night	25% 10% 31% 27% 7% 1	540
	11th to 20th	Night	21% 11% 35% 26% 7%	409
	21st to end	Night	21% 4 18% 41% 14% 2	389
June	1st to 10th	Night	19% 5% 28% 34% 13% 1	360
	11th to 20th	Night	16% 3 24% 43% 14%	360
	21st to end	Night	9% 3 22% 54% 12% 1	360
July	1st to 10th	Night	12% 3 21% 42% 21% 1	350
	11th to 20th	Night	13% 3 17% 45% 21% 1	348
	21st to end	Night	13% 5% 17% 47% 17% 1	394
August	1st to 10th	Night	9% 2 22% 45% 20% 2	454
	11th to 20th	Night	13% 4 18% 37% 26% 2	710
	21st to end	Night	14% 5% 18% 35% 25% 3	792
September	1st to 10th	Night	16% 4 25% 34% 18% 3	720
	11th to 20th	Night	17% 4 23% 33% 18% 4	720
	21st to end	Night	20% 6% 23% 32% 16% 2	720
October	1st to 10th	Night	24% 8% 27% 25% 14% 3	720
	11th to 20th	Night	18% 10% 31% 30% 11%	720
	21st to end	Night	26% 11% 33% 22% 6% 1	792
November	1st to 10th	Night	15% 13% 34% 26% 11% 1	740
	11th to 20th	Night	23% 14% 32% 23% 7%	760
	21st to end	Night	18% 17% 34% 25% 6% 1	760
December	1st to 10th	Night	24% 17% 35% 18% 5% 1	760
	11th to 20th	Night	23% 17% 34% 21% 4	760
	21st to end	Night	24% 15% 37% 20% 3	836

Page generated at 2024-01-10 01:25:03. Version ac07

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