Trenton (NJ)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trenton (NJ) clear sky chart from 2005-11-06 to 2024-11-01.

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% 7% 2 6% 4 4 4 4 6% 7% 40%	101270
	Night	17% 7% 2 6% 4 4 4 3 5% 6% 42%	97665
Transparency	Day	23% 49% 6% 12% 8% 1	101025
	Night	23% 49% 6% 12% 8% 1	97530
Seeing	Day	21% 15% 29% 22% 10% 3	15006
	Night	19% 12% 31% 28% 9% 1	24210

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% 3 5% 4 3 4 3 4 5% 47%	2517
	11th to 20th	Day	15% 9% 4 8% 5% 4 4 3 5% 6% 37%	2523
	21st to end	Day	22% 8% 3 6% 5% 4 4 3 4 5% 36%	3124
February	1st to 10th	Day	16% 7% 3 8% 4 4 4 3 5% 7% 40%	1710
	11th to 20th	Day	17% 7% 3 6% 5% 4 4 3 4 6% 42%	1831
	21st to end	Day	19% 8% 3 7% 5% 3 4 4 5% 5% 37%	1570
March	1st to 10th	Day	26% 7% 2 5% 3 4 3 3 3 5% 37%	3116
	11th to 20th	Day	10% 4 2 6% 5% 5% 5% 4 6% 7% 46%	3416
	21st to end	Day	22% 5% 2 5% 4 4 3 3 4 5% 43%	4088
April	1st to 10th	Day	16% 8% 3 6% 4 4 4 3 6% 6% 40%	2280
	11th to 20th	Day	15% 6% 2 5% 4 4 4 4 6% 7% 41%	2254
	21st to end	Day	16% 5% 2 6% 5% 5% 4 4 6% 6% 41%	2280
May	1st to 10th	Day	27% 8% 2 6% 4 4 4 3 5% 7% 29%	4060
	11th to 20th	Day	24% 8% 3 8% 5% 5% 4 4 5% 6% 29%	4398
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 9% 43%	4837
June	1st to 10th	Day	13% 5% 2 5% 5% 5% 5% 5% 8% 9% 38%	2660
	11th to 20th	Day	12% 7% 2 5% 5% 5% 5% 5% 6% 9% 38%	2660
	21st to end	Day	11% 6% 2 5% 4 5% 5% 5% 6% 9% 41%	2660
July	1st to 10th	Day	8% 6% 3 7% 6% 6% 7% 5% 8% 10% 35%	4440
	11th to 20th	Day	10% 7% 2 6% 5% 5% 6% 5% 7% 10% 38%	4440
	21st to end	Day	12% 9% 3 8% 5% 5% 5% 5% 7% 8% 32%	4814
August	1st to 10th	Day	18% 7% 2 8% 5% 5% 5% 4 6% 8% 32%	4061
	11th to 20th	Day	13% 6% 3 6% 4 5% 4 4 6% 9% 41%	3730
	21st to end	Day	11% 5% 2 5% 4 4 4 4 6% 9% 47%	4180
September	1st to 10th	Day	14% 6% 2 7% 4 4 3 3 6% 7% 44%	2280
	11th to 20th	Day	12% 5% 2 4 4 4 4 3 5% 9% 49%	2228
	21st to end	Day	18% 7% 3 6% 4 4 4 4 4 6% 39%	2090
October	1st to 10th	Day	17% 7% 3 5% 3 3 4 3 5% 6% 43%	1939
	11th to 20th	Day	15% 6% 2 5% 3 4 3 3 5% 6% 49%	1900
	21st to end	Day	18% 7% 2 5% 3 3 3 3 5% 6% 46%	1990
November	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 5% 7% 51%	1671
	11th to 20th	Day	17% 6% 3 4 2 3 4 3 4 6% 48%	1710
	21st to end	Day	15% 6% 2 5% 4 3 3 3 5% 7% 46%	1615
December	1st to 10th	Day	18% 7% 3 7% 3 3 3 3 6% 7% 39%	1520
	11th to 20th	Day	20% 7% 3 4 3 4 4 4 4 6% 43%	1906
	21st to end	Day	17% 7% 3 7% 4 5% 5% 5% 6% 7% 36%	2772
January	1st to 10th	Night	17% 7% 2 5% 4 4 3 3 4 6% 46%	4429
	11th to 20th	Night	17% 8% 3 6% 4 3 3 3 4 5% 44%	4436
	21st to end	Night	24% 9% 2 6% 4 3 3 3 4 6% 36%	4532
February	1st to 10th	Night	17% 9% 2 5% 3 4 4 3 6% 6% 41%	2470
	11th to 20th	Night	17% 9% 3 5% 4 3 3 3 5% 5% 42%	2233
	21st to end	Night	19% 7% 2 5% 4 3 3 4 4 5% 43%	1884
March	1st to 10th	Night	23% 10% 3 6% 3 4 3 2 4 5% 38%	3724
	11th to 20th	Night	11% 6% 3 6% 4 4 4 3 4 5% 49%	3525
	21st to end	Night	18% 9% 3 6% 4 3 3 3 3 5% 44%	3544
April	1st to 10th	Night	17% 7% 3 6% 4 5% 4 4 5% 6% 40%	1900
	11th to 20th	Night	16% 6% 2 7% 4 4 4 3 5% 6% 41%	1875
	21st to end	Night	19% 5% 1 5% 3 3 4 3 5% 7% 43%	1900
May	1st to 10th	Night	22% 10% 4 7% 4 3 4 4 5% 7% 30%	2882
	11th to 20th	Night	23% 9% 3 7% 5% 4 3 3 5% 7% 31%	2506
	21st to end	Night	14% 7% 2 5% 3 4 4 4 6% 9% 42%	2738
June	1st to 10th	Night	15% 7% 2 5% 4 4 4 4 6% 7% 43%	1520
	11th to 20th	Night	12% 6% 2 7% 5% 4 4 4 5% 8% 42%	1520
	21st to end	Night	9% 5% 2 6% 6% 4 4 4 8% 11% 41%	1520
July	1st to 10th	Night	7% 6% 3 8% 5% 5% 6% 5% 8% 9% 37%	2520
	11th to 20th	Night	12% 5% 3 6% 5% 5% 5% 5% 7% 10% 37%	2520
	21st to end	Night	15% 7% 3 7% 5% 4 5% 5% 7% 8% 35%	2739
August	1st to 10th	Night	23% 6% 2 7% 4 4 4 4 7% 8% 31%	2831
	11th to 20th	Night	13% 7% 2 6% 4 5% 5% 4 6% 7% 40%	3097
	21st to end	Night	10% 5% 2 5% 4 3 3 3 6% 9% 49%	3476
September	1st to 10th	Night	15% 6% 3 6% 5% 3 4 4 4 5% 45%	1900
	11th to 20th	Night	12% 5% 1 4 3 4 4 3 5% 7% 52%	1952
	21st to end	Night	19% 7% 2 6% 4 3 3 3 5% 7% 41%	2090
October	1st to 10th	Night	18% 6% 2 6% 4 4 3 3 4 6% 44%	2237
	11th to 20th	Night	14% 4 2 5% 3 3 4 3 4 7% 51%	2280
	21st to end	Night	18% 7% 2 4 3 3 3 3 5% 5% 46%	2608
November	1st to 10th	Night	11% 5% 2 5% 4 4 3 3 5% 6% 52%	2414
	11th to 20th	Night	17% 6% 2 6% 4 3 3 3 4 4 48%	2470
	21st to end	Night	13% 7% 2 5% 5% 4 3 3 6% 6% 46%	2561
December	1st to 10th	Night	20% 7% 3 6% 3 3 4 3 5% 6% 40%	2660
	11th to 20th	Night	18% 6% 2 6% 4 4 5% 4 6% 6% 41%	3288
	21st to end	Night	18% 8% 3 7% 4 4 3 3 5% 5% 39%	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	25% 38% 8% 17% 9% 3	2518
	11th to 20th	Day	29% 39% 7% 15% 8% 1	2523
	21st to end	Day	35% 41% 7% 11% 5% 1	3124
February	1st to 10th	Day	17% 66% 6% 7% 3 1	1710
	11th to 20th	Day	16% 63% 2 9% 8% 2	1840
	21st to end	Day	17% 66% 4 7% 4 1	1570
March	1st to 10th	Day	35% 42% 5% 15% 3 1	3119
	11th to 20th	Day	16% 43% 9% 21% 10% 1	3416
	21st to end	Day	27% 40% 5% 10% 15% 3	4088
April	1st to 10th	Day	18% 66% 3 7% 5% 1	2280
	11th to 20th	Day	13% 67% 5% 8% 7%	2254
	21st to end	Day	16% 65% 4 8% 6% 1	2280
May	1st to 10th	Day	36% 42% 8% 9% 4	4074
	11th to 20th	Day	36% 42% 8% 11% 2	4402
	21st to end	Day	21% 43% 7% 18% 11% 1	4837
June	1st to 10th	Day	15% 66% 4 9% 6%	2660
	11th to 20th	Day	14% 66% 4 9% 7%	2660
	21st to end	Day	14% 65% 4 9% 8%	2660
July	1st to 10th	Day	27% 42% 10% 11% 8% 1	4370
	11th to 20th	Day	27% 40% 11% 13% 9%	4365
	21st to end	Day	32% 38% 7% 12% 10% 1	4661
August	1st to 10th	Day	34% 40% 8% 13% 5%	4047
	11th to 20th	Day	23% 39% 8% 20% 8%	3766
	21st to end	Day	17% 38% 7% 21% 17% 1	4180
September	1st to 10th	Day	16% 60% 6% 10% 7% 1	2280
	11th to 20th	Day	15% 61% 5% 9% 9% 2	2228
	21st to end	Day	22% 60% 3 8% 7%	2090
October	1st to 10th	Day	18% 60% 5% 6% 8% 2	1939
	11th to 20th	Day	12% 60% 4 10% 13% 1	1900
	21st to end	Day	14% 59% 4 12% 9% 1	1990
November	1st to 10th	Day	16% 59% 6% 10% 7% 2	1671
	11th to 20th	Day	13% 59% 4 10% 13% 1	1710
	21st to end	Day	14% 60% 6% 14% 5% 2	1615
December	1st to 10th	Day	21% 60% 6% 7% 6%	1520
	11th to 20th	Day	23% 49% 6% 14% 7% 1	1906
	21st to end	Day	29% 41% 7% 17% 6%	2772
January	1st to 10th	Night	25% 38% 6% 20% 7% 3	4429
	11th to 20th	Night	28% 37% 7% 17% 9% 2	4436
	21st to end	Night	35% 40% 5% 13% 6% 1	4532
February	1st to 10th	Night	15% 65% 6% 10% 3 1	2470
	11th to 20th	Night	16% 64% 2 7% 9% 2	2235
	21st to end	Night	16% 65% 4 7% 6% 2	1884
March	1st to 10th	Night	35% 41% 4 13% 6% 1	3734
	11th to 20th	Night	17% 43% 10% 18% 11% 1	3526
	21st to end	Night	28% 40% 4 9% 16% 4	3544
April	1st to 10th	Night	17% 65% 3 8% 6% 1	1900
	11th to 20th	Night	14% 66% 4 8% 7% 1	1875
	21st to end	Night	15% 65% 4 7% 8% 1	1900
May	1st to 10th	Night	34% 43% 6% 13% 3	2888
	11th to 20th	Night	36% 42% 10% 8% 3	2507
	21st to end	Night	22% 43% 10% 14% 9% 2	2739
June	1st to 10th	Night	14% 65% 3 9% 8%	1520
	11th to 20th	Night	13% 66% 4 10% 6%	1520
	21st to end	Night	13% 64% 5% 11% 6% 1	1520
July	1st to 10th	Night	26% 41% 13% 11% 7% 1	2480
	11th to 20th	Night	27% 39% 12% 16% 6%	2472
	21st to end	Night	33% 37% 9% 10% 10% 1	2651
August	1st to 10th	Night	36% 40% 12% 8% 4	2821
	11th to 20th	Night	25% 39% 8% 21% 7%	3127
	21st to end	Night	16% 38% 6% 24% 16%	3476
September	1st to 10th	Night	15% 61% 6% 10% 7% 1	1900
	11th to 20th	Night	14% 61% 4 9% 11% 2	1952
	21st to end	Night	21% 60% 3 8% 6%	2090
October	1st to 10th	Night	18% 61% 6% 8% 7% 1	2237
	11th to 20th	Night	11% 60% 5% 14% 9% 2	2280
	21st to end	Night	15% 59% 4 12% 9% 2	2608
November	1st to 10th	Night	16% 59% 6% 10% 7% 2	2414
	11th to 20th	Night	15% 59% 3 9% 10% 3	2470
	21st to end	Night	13% 60% 6% 13% 6% 1	2561
December	1st to 10th	Night	21% 60% 4 9% 5%	2660
	11th to 20th	Night	20% 50% 7% 9% 11% 3	3288
	21st to end	Night	31% 39% 7% 16% 7%	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	26% 24% 29% 17% 2 1	180
	11th to 20th	Day	37% 26% 27% 9% 1	182
	21st to end	Day	24% 26% 32% 13% 5%	297
February	1st to 10th	Day	29% 24% 34% 10% 2	270
	11th to 20th	Day	29% 24% 34% 12% 2	439
	21st to end	Day	30% 21% 32% 15% 3	382
March	1st to 10th	Day	29% 20% 30% 18% 3	460
	11th to 20th	Day	24% 26% 32% 12% 4 1	460
	21st to end	Day	27% 22% 31% 14% 5% 1	506
April	1st to 10th	Day	27% 23% 32% 11% 6% 1	460
	11th to 20th	Day	23% 21% 32% 13% 8% 2	452
	21st to end	Day	27% 20% 32% 16% 3 2	460
May	1st to 10th	Day	29% 19% 29% 14% 7% 2	463
	11th to 20th	Day	22% 16% 33% 20% 8% 1	487
	21st to end	Day	20% 9% 26% 27% 16% 2	529
June	1st to 10th	Day	17% 11% 31% 26% 12% 3	490
	11th to 20th	Day	18% 13% 28% 27% 12% 3	490
	21st to end	Day	15% 11% 33% 28% 11% 3	490
July	1st to 10th	Day	11% 7% 23% 33% 20% 6%	485
	11th to 20th	Day	9% 4 27% 32% 22% 6%	484
	21st to end	Day	14% 7% 31% 29% 16% 3	532
August	1st to 10th	Day	14% 5% 25% 34% 16% 7%	486
	11th to 20th	Day	13% 6% 22% 33% 21% 6%	479
	21st to end	Day	13% 7% 25% 29% 17% 9%	539
September	1st to 10th	Day	16% 10% 26% 24% 16% 8%	490
	11th to 20th	Day	15% 6% 28% 28% 15% 9%	490
	21st to end	Day	24% 13% 23% 24% 10% 6%	490
October	1st to 10th	Day	24% 8% 26% 22% 13% 7%	490
	11th to 20th	Day	17% 16% 28% 26% 10% 3	490
	21st to end	Day	21% 16% 29% 21% 10% 3	486
November	1st to 10th	Day	20% 10% 32% 22% 12% 3	365
	11th to 20th	Day	24% 17% 31% 20% 7% 1	370
	21st to end	Day	21% 15% 37% 18% 8%	275
December	1st to 10th	Day	26% 26% 31% 9% 8%	180
	11th to 20th	Day	36% 22% 25% 12% 6%	180
	21st to end	Day	29% 17% 31% 16% 6% 1	198
January	1st to 10th	Night	20% 19% 38% 20% 3	760
	11th to 20th	Night	24% 16% 36% 21% 3	760
	21st to end	Night	19% 20% 38% 22% 1	836
February	1st to 10th	Night	22% 15% 38% 24% 2	760
	11th to 20th	Night	24% 22% 36% 16% 1	743
	21st to end	Night	25% 18% 37% 18% 2	628
March	1st to 10th	Night	23% 19% 34% 21% 4	760
	11th to 20th	Night	24% 18% 35% 18% 4	760
	21st to end	Night	21% 14% 41% 19% 5%	836
April	1st to 10th	Night	21% 19% 37% 19% 4	760
	11th to 20th	Night	19% 15% 38% 23% 5%	751
	21st to end	Night	21% 13% 36% 25% 5%	760
May	1st to 10th	Night	23% 17% 31% 24% 5%	605
	11th to 20th	Night	21% 9% 37% 27% 5%	385
	21st to end	Night	16% 6% 26% 39% 12% 1	411
June	1st to 10th	Night	15% 7% 29% 37% 11% 1	380
	11th to 20th	Night	12% 6% 31% 40% 12%	380
	21st to end	Night	11% 3 28% 45% 13%	380
July	1st to 10th	Night	10% 4 25% 42% 18% 1	370
	11th to 20th	Night	9% 3 24% 44% 19% 1	368
	21st to end	Night	12% 3 26% 43% 16%	416
August	1st to 10th	Night	14% 1 19% 45% 19% 2	560
	11th to 20th	Night	14% 3 20% 36% 24% 3	750
	21st to end	Night	14% 5% 17% 41% 21% 2	836
September	1st to 10th	Night	17% 3 26% 34% 18% 2	760
	11th to 20th	Night	15% 4 21% 34% 21% 4	760
	21st to end	Night	22% 6% 22% 33% 17% 1	760
October	1st to 10th	Night	22% 8% 26% 26% 16% 3	760
	11th to 20th	Night	16% 11% 28% 33% 12%	760
	21st to end	Night	21% 11% 32% 27% 8%	836
November	1st to 10th	Night	15% 10% 34% 29% 12% 1	743
	11th to 20th	Night	20% 16% 31% 26% 8%	760
	21st to end	Night	18% 14% 36% 25% 7%	760
December	1st to 10th	Night	26% 17% 31% 19% 6% 1	760
	11th to 20th	Night	20% 15% 37% 24% 4	760
	21st to end	Night	22% 15% 34% 26% 3	836

Page generated at 2024-10-29 11:20:48. Version ac07

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