Metuchen
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Metuchen clear sky chart from 2005-11-06 to 2024-02-25.

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% 3 5% 5% 3 4 5% 5% 7% 40%	78366
	Night	17% 7% 3 5% 5% 3 4 4 5% 7% 42%	80923
Transparency	Day	28% 37% 8% 15% 10% 2	78071
	Night	29% 35% 8% 16% 11% 2	80752
Seeing	Day	20% 15% 30% 23% 11% 3	14006
	Night	20% 12% 32% 27% 9% 1	23344

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% 7% 2 4 4 3 4 4 4 5% 47%	2517
	11th to 20th	Day	15% 9% 3 6% 5% 3 5% 5% 5% 7% 36%	2520
	21st to end	Day	23% 10% 5% 6% 5% 3 4 3 4 5% 33%	3064
February	1st to 10th	Day	16% 8% 3 5% 5% 3 4 4 4 6% 41%	1710
	11th to 20th	Day	15% 7% 3 6% 5% 3 4 5% 4 6% 43%	1846
	21st to end	Day	19% 7% 3 6% 5% 3 4 4 6% 5% 38%	1520
March	1st to 10th	Day	14% 8% 2 5% 5% 3 3 4 5% 7% 44%	1797
	11th to 20th	Day	15% 6% 3 5% 5% 3 5% 5% 6% 7% 39%	1916
	21st to end	Day	20% 6% 3 5% 5% 3 4 4 5% 6% 39%	2343
April	1st to 10th	Day	17% 7% 3 6% 4 3 4 4 5% 7% 40%	2160
	11th to 20th	Day	16% 5% 3 5% 5% 2 4 5% 5% 9% 41%	2134
	21st to end	Day	19% 6% 2 4 4 3 5% 4 5% 7% 39%	2160
May	1st to 10th	Day	20% 8% 3 5% 5% 3 5% 4 5% 7% 34%	2335
	11th to 20th	Day	21% 5% 3 5% 5% 3 5% 5% 6% 7% 36%	2468
	21st to end	Day	16% 5% 3 5% 4 3 5% 5% 6% 8% 41%	2725
June	1st to 10th	Day	15% 6% 2 5% 5% 4 5% 6% 7% 10% 37%	2520
	11th to 20th	Day	14% 6% 3 6% 6% 3 4 5% 6% 8% 37%	2520
	21st to end	Day	12% 5% 2 6% 5% 4 6% 5% 7% 8% 40%	2520
July	1st to 10th	Day	10% 5% 3 6% 6% 4 6% 6% 8% 8% 38%	2520
	11th to 20th	Day	9% 5% 2 5% 5% 3 6% 7% 8% 10% 41%	2520
	21st to end	Day	11% 6% 3 7% 7% 4 6% 6% 7% 8% 35%	2744
August	1st to 10th	Day	9% 5% 2 6% 6% 4 6% 6% 7% 10% 37%	2344
	11th to 20th	Day	12% 6% 2 5% 6% 4 6% 7% 6% 8% 38%	2126
	21st to end	Day	15% 5% 3 5% 5% 3 4 5% 6% 9% 41%	2376
September	1st to 10th	Day	14% 5% 3 5% 5% 3 5% 5% 4 7% 44%	2160
	11th to 20th	Day	14% 5% 2 4 4 2 3 3 5% 8% 50%	2095
	21st to end	Day	18% 5% 3 4 5% 3 3 5% 5% 6% 42%	1980
October	1st to 10th	Day	19% 6% 2 5% 5% 3 4 5% 5% 6% 41%	1863
	11th to 20th	Day	16% 5% 2 4 4 2 4 4 5% 7% 46%	1800
	21st to end	Day	19% 5% 2 5% 4 3 4 4 4 6% 43%	1859
November	1st to 10th	Day	14% 6% 3 4 4 2 3 3 4 6% 51%	1671
	11th to 20th	Day	17% 5% 2 4 4 3 3 3 5% 6% 47%	1710
	21st to end	Day	16% 6% 3 3 4 3 4 4 5% 8% 45%	1625
December	1st to 10th	Day	18% 8% 3 5% 5% 2 3 4 5% 9% 38%	1520
	11th to 20th	Day	20% 6% 2 4 3 3 3 5% 4 7% 43%	1906
	21st to end	Day	18% 8% 3 7% 6% 3 5% 5% 5% 7% 33%	2772
January	1st to 10th	Night	16% 7% 2 4 4 2 4 4 5% 6% 46%	4429
	11th to 20th	Night	17% 8% 3 5% 4 3 4 3 4 6% 43%	4440
	21st to end	Night	24% 10% 3 5% 4 3 3 4 4 5% 35%	4591
February	1st to 10th	Night	16% 9% 3 5% 4 3 4 3 5% 6% 42%	2470
	11th to 20th	Night	17% 8% 3 5% 5% 3 4 4 4 5% 42%	2218
	21st to end	Night	19% 7% 3 4 4 2 4 4 4 6% 43%	1831
March	1st to 10th	Night	16% 6% 2 4 4 3 4 4 4 6% 46%	2150
	11th to 20th	Night	18% 7% 3 5% 4 3 4 4 4 6% 43%	2039
	21st to end	Night	18% 7% 3 5% 5% 2 4 5% 3 6% 41%	2012
April	1st to 10th	Night	18% 6% 3 6% 5% 3 5% 5% 5% 6% 39%	1800
	11th to 20th	Night	17% 7% 3 6% 4 3 5% 4 5% 7% 41%	1775
	21st to end	Night	19% 5% 2 5% 4 3 4 4 5% 7% 42%	1800
May	1st to 10th	Night	20% 8% 4 6% 5% 3 4 4 5% 6% 36%	1623
	11th to 20th	Night	19% 5% 3 6% 6% 3 4 5% 5% 6% 39%	1440
	21st to end	Night	16% 7% 2 5% 4 2 4 5% 5% 9% 41%	1550
June	1st to 10th	Night	15% 5% 3 5% 5% 2 5% 5% 7% 9% 40%	1440
	11th to 20th	Night	13% 6% 3 6% 5% 3 5% 4 6% 10% 39%	1440
	21st to end	Night	10% 5% 2 5% 5% 4 5% 4 6% 10% 43%	1440
July	1st to 10th	Night	11% 4 3 6% 6% 3 5% 7% 7% 9% 41%	1440
	11th to 20th	Night	10% 5% 3 5% 7% 3 6% 6% 6% 9% 41%	1440
	21st to end	Night	8% 5% 3 5% 5% 3 5% 5% 7% 10% 44%	1574
August	1st to 10th	Night	9% 6% 2 5% 6% 4 5% 5% 7% 9% 42%	1572
	11th to 20th	Night	11% 5% 3 7% 6% 4 6% 5% 6% 8% 38%	1774
	21st to end	Night	14% 6% 3 5% 5% 3 5% 4 5% 10% 40%	1980
September	1st to 10th	Night	15% 5% 3 6% 5% 3 5% 5% 5% 6% 43%	1800
	11th to 20th	Night	14% 5% 2 4 3 2 3 4 4 7% 52%	1864
	21st to end	Night	17% 7% 2 4 5% 3 3 4 4 6% 45%	1980
October	1st to 10th	Night	19% 5% 2 5% 4 3 4 4 5% 6% 43%	2095
	11th to 20th	Night	15% 4 2 5% 5% 2 3 4 4 6% 50%	2160
	21st to end	Night	19% 8% 2 4 3 2 3 3 5% 5% 44%	2497
November	1st to 10th	Night	12% 5% 2 4 5% 2 4 3 4 5% 53%	2407
	11th to 20th	Night	18% 5% 3 5% 4 2 3 4 4 5% 48%	2470
	21st to end	Night	15% 5% 3 5% 4 3 4 4 5% 8% 46%	2550
December	1st to 10th	Night	20% 7% 3 5% 4 2 4 4 5% 6% 40%	2660
	11th to 20th	Night	19% 6% 2 4 4 3 4 5% 5% 6% 43%	3288
	21st to end	Night	19% 9% 3 6% 5% 3 4 4 5% 5% 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	29% 27% 9% 25% 10% 1	2518
	11th to 20th	Day	36% 27% 9% 16% 11% 1	2520
	21st to end	Day	45% 25% 7% 16% 6% 1	3064
February	1st to 10th	Day	28% 34% 8% 18% 10% 1	1710
	11th to 20th	Day	29% 36% 8% 16% 10% 2	1855
	21st to end	Day	32% 35% 6% 14% 10% 3	1520
March	1st to 10th	Day	26% 37% 8% 19% 9% 1	1800
	11th to 20th	Day	28% 36% 9% 14% 10% 2	1916
	21st to end	Day	29% 37% 6% 14% 12% 3	2343
April	1st to 10th	Day	27% 37% 7% 13% 11% 4	2160
	11th to 20th	Day	28% 37% 8% 14% 10% 3	2134
	21st to end	Day	28% 38% 7% 12% 12% 3	2160
May	1st to 10th	Day	32% 37% 6% 12% 12% 2	2335
	11th to 20th	Day	30% 39% 7% 12% 10% 2	2472
	21st to end	Day	25% 40% 10% 14% 10% 2	2725
June	1st to 10th	Day	26% 40% 10% 14% 9% 1	2520
	11th to 20th	Day	29% 40% 10% 14% 5% 2	2520
	21st to end	Day	27% 40% 9% 15% 8% 1	2520
July	1st to 10th	Day	26% 42% 9% 13% 9% 1	2450
	11th to 20th	Day	22% 41% 10% 15% 10% 2	2445
	21st to end	Day	25% 42% 8% 12% 11% 1	2591
August	1st to 10th	Day	26% 41% 10% 14% 9% 1	2330
	11th to 20th	Day	27% 38% 9% 15% 10% 1	2126
	21st to end	Day	30% 39% 7% 11% 10% 2	2376
September	1st to 10th	Day	25% 39% 7% 12% 14% 3	2160
	11th to 20th	Day	21% 37% 8% 16% 16% 2	2095
	21st to end	Day	28% 38% 6% 12% 13% 3	1980
October	1st to 10th	Day	26% 37% 9% 15% 13%	1863
	11th to 20th	Day	25% 38% 8% 17% 11% 2	1800
	21st to end	Day	28% 38% 7% 14% 11% 1	1859
November	1st to 10th	Day	20% 40% 8% 17% 14% 1	1671
	11th to 20th	Day	26% 40% 7% 15% 11% 2	1710
	21st to end	Day	25% 40% 7% 18% 8% 1	1625
December	1st to 10th	Day	26% 41% 10% 16% 7% 1	1520
	11th to 20th	Day	29% 33% 10% 18% 9% 1	1906
	21st to end	Day	35% 30% 10% 18% 6%	2772
January	1st to 10th	Night	30% 26% 10% 26% 7% 1	4429
	11th to 20th	Night	34% 25% 9% 20% 10% 2	4440
	21st to end	Night	42% 25% 7% 18% 8%	4591
February	1st to 10th	Night	29% 35% 9% 16% 11% 1	2470
	11th to 20th	Night	30% 36% 8% 13% 11% 3	2220
	21st to end	Night	28% 35% 5% 18% 12% 2	1831
March	1st to 10th	Night	25% 37% 9% 18% 10% 2	2160
	11th to 20th	Night	30% 38% 7% 13% 10% 2	2040
	21st to end	Night	27% 38% 6% 13% 12% 4	2012
April	1st to 10th	Night	29% 38% 8% 11% 11% 4	1800
	11th to 20th	Night	31% 37% 5% 11% 13% 2	1775
	21st to end	Night	26% 38% 7% 13% 13% 4	1800
May	1st to 10th	Night	31% 38% 7% 10% 12% 1	1623
	11th to 20th	Night	29% 39% 7% 10% 13% 3	1441
	21st to end	Night	24% 41% 11% 13% 9% 2	1551
June	1st to 10th	Night	27% 39% 9% 14% 11% 1	1440
	11th to 20th	Night	26% 39% 13% 14% 7% 1	1440
	21st to end	Night	24% 41% 11% 15% 8% 1	1440
July	1st to 10th	Night	27% 41% 10% 13% 8% 1	1400
	11th to 20th	Night	24% 41% 9% 15% 10% 1	1392
	21st to end	Night	20% 42% 12% 14% 10% 2	1486
August	1st to 10th	Night	25% 39% 12% 14% 9% 1	1562
	11th to 20th	Night	27% 39% 9% 14% 9% 1	1774
	21st to end	Night	30% 39% 9% 10% 11% 1	1980
September	1st to 10th	Night	28% 38% 7% 13% 14% 1	1800
	11th to 20th	Night	21% 37% 8% 17% 16% 2	1864
	21st to end	Night	26% 38% 5% 15% 15% 1	1980
October	1st to 10th	Night	26% 37% 8% 17% 11% 1	2095
	11th to 20th	Night	26% 37% 9% 17% 10% 1	2160
	21st to end	Night	28% 38% 7% 15% 11% 1	2497
November	1st to 10th	Night	19% 41% 7% 15% 16% 2	2407
	11th to 20th	Night	26% 40% 6% 16% 11% 2	2470
	21st to end	Night	25% 40% 8% 16% 10%	2550
December	1st to 10th	Night	26% 40% 9% 15% 8% 1	2660
	11th to 20th	Night	27% 34% 9% 14% 13% 2	3288
	21st to end	Night	37% 28% 10% 17% 8%	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% 24% 33% 16% 3 1	180
	11th to 20th	Day	26% 34% 26% 12% 1	180
	21st to end	Day	22% 25% 33% 14% 4 1	281
February	1st to 10th	Day	27% 24% 36% 10% 2	270
	11th to 20th	Day	25% 24% 39% 11% 2	454
	21st to end	Day	27% 23% 30% 18% 3	362
March	1st to 10th	Day	20% 27% 32% 17% 3	420
	11th to 20th	Day	22% 25% 34% 13% 4 1	420
	21st to end	Day	27% 22% 32% 14% 5% 1	462
April	1st to 10th	Day	25% 23% 32% 13% 7% 1	420
	11th to 20th	Day	20% 21% 33% 14% 9% 2	412
	21st to end	Day	28% 21% 31% 15% 3 2	420
May	1st to 10th	Day	29% 18% 30% 15% 5% 2	423
	11th to 20th	Day	21% 14% 35% 22% 7% 1	447
	21st to end	Day	21% 8% 23% 28% 17% 3	485
June	1st to 10th	Day	16% 9% 33% 28% 12% 2	450
	11th to 20th	Day	17% 12% 30% 28% 11% 2	450
	21st to end	Day	14% 7% 34% 29% 14% 2	450
July	1st to 10th	Day	12% 5% 25% 31% 22% 6%	445
	11th to 20th	Day	9% 5% 24% 35% 22% 6%	444
	21st to end	Day	12% 7% 27% 34% 17% 3	488
August	1st to 10th	Day	10% 6% 21% 39% 18% 7%	446
	11th to 20th	Day	13% 3 21% 35% 23% 4	439
	21st to end	Day	13% 6% 26% 30% 16% 8%	495
September	1st to 10th	Day	16% 8% 27% 23% 18% 8%	450
	11th to 20th	Day	15% 7% 27% 28% 14% 9%	450
	21st to end	Day	21% 11% 26% 26% 11% 5%	450
October	1st to 10th	Day	26% 6% 24% 23% 15% 6%	450
	11th to 20th	Day	18% 13% 30% 26% 12% 2	450
	21st to end	Day	23% 15% 31% 20% 9% 2	435
November	1st to 10th	Day	15% 16% 32% 22% 13% 2	365
	11th to 20th	Day	23% 19% 31% 20% 6% 1	370
	21st to end	Day	18% 19% 35% 19% 8% 1	285
December	1st to 10th	Day	23% 28% 30% 11% 7% 1	180
	11th to 20th	Day	33% 21% 29% 12% 4	180
	21st to end	Day	25% 19% 34% 15% 6% 1	198
January	1st to 10th	Night	20% 20% 39% 18% 3	760
	11th to 20th	Night	25% 17% 35% 20% 3	760
	21st to end	Night	19% 20% 39% 21% 1	836
February	1st to 10th	Night	22% 17% 36% 23% 1	760
	11th to 20th	Night	25% 22% 38% 14% 1	743
	21st to end	Night	25% 21% 34% 18% 2	611
March	1st to 10th	Night	23% 19% 34% 21% 3	720
	11th to 20th	Night	24% 19% 34% 18% 4	720
	21st to end	Night	22% 14% 41% 19% 5%	792
April	1st to 10th	Night	22% 20% 35% 19% 5%	720
	11th to 20th	Night	20% 14% 38% 23% 5%	711
	21st to end	Night	21% 13% 36% 25% 4 1	720
May	1st to 10th	Night	25% 14% 33% 22% 6%	543
	11th to 20th	Night	21% 9% 35% 28% 6%	379
	21st to end	Night	17% 7% 24% 38% 12% 2	389
June	1st to 10th	Night	17% 6% 29% 36% 11% 1	360
	11th to 20th	Night	14% 6% 29% 39% 13%	360
	21st to end	Night	8% 3 29% 48% 12% 1	360
July	1st to 10th	Night	11% 4 25% 41% 17% 2	350
	11th to 20th	Night	11% 3 21% 43% 20% 1	348
	21st to end	Night	9% 2 28% 44% 17%	394
August	1st to 10th	Night	11% 2 20% 45% 19% 2	498
	11th to 20th	Night	14% 3 19% 39% 23% 2	710
	21st to end	Night	16% 4 17% 41% 20% 2	792
September	1st to 10th	Night	16% 3 26% 35% 18% 2	720
	11th to 20th	Night	15% 5% 23% 32% 20% 4	720
	21st to end	Night	20% 6% 23% 33% 15% 2	720
October	1st to 10th	Night	23% 8% 26% 26% 14% 3	720
	11th to 20th	Night	17% 12% 29% 33% 10%	720
	21st to end	Night	24% 12% 32% 24% 7% 1	792
November	1st to 10th	Night	15% 11% 35% 27% 11% 1	740
	11th to 20th	Night	21% 16% 32% 24% 7%	760
	21st to end	Night	17% 17% 36% 23% 6% 1	760
December	1st to 10th	Night	27% 16% 32% 18% 6% 1	760
	11th to 20th	Night	22% 15% 38% 22% 4	760
	21st to end	Night	24% 15% 36% 23% 2	836

Page generated at 2024-02-22 06:05:47. Version ac07

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