Holmdel
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Holmdel clear sky chart from 2005-11-06 to 2024-11-04.

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 5% 7% 40%	101283
	Night	17% 7% 2 6% 4 4 4 3 5% 6% 41%	97729
Transparency	Day	41% 7% 12% 22% 16% 2	104828
	Night	41% 6% 12% 23% 16% 3	102260
Seeing	Day	18% 10% 29% 27% 13% 3	15042
	Night	18% 9% 32% 29% 11% 1	24202

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% 9% 2 5% 4 4 3 3 3 5% 46%	2517
	11th to 20th	Day	16% 9% 3 7% 4 4 4 3 5% 6% 39%	2520
	21st to end	Day	23% 13% 4 7% 4 3 3 2 3 4 33%	3060
February	1st to 10th	Day	16% 10% 3 6% 4 4 4 2 4 6% 41%	1725
	11th to 20th	Day	16% 8% 2 6% 4 4 4 3 4 5% 42%	1848
	21st to end	Day	18% 9% 3 7% 4 4 4 4 5% 6% 38%	1570
March	1st to 10th	Day	28% 8% 2 6% 3 3 3 3 3 5% 37%	3116
	11th to 20th	Day	9% 5% 2 6% 5% 5% 4 4 6% 7% 47%	3349
	21st to end	Day	21% 7% 2 5% 3 3 3 3 4 5% 44%	4126
April	1st to 10th	Day	18% 8% 3 5% 5% 4 3 4 5% 7% 39%	2280
	11th to 20th	Day	15% 7% 3 6% 4 4 4 4 6% 8% 41%	2254
	21st to end	Day	18% 5% 2 5% 4 4 5% 4 6% 7% 40%	2280
May	1st to 10th	Day	25% 10% 3 6% 4 4 5% 3 5% 7% 28%	4106
	11th to 20th	Day	27% 7% 2 6% 4 4 3 4 5% 6% 32%	4352
	21st to end	Day	14% 5% 2 5% 4 4 4 4 6% 9% 43%	4837
June	1st to 10th	Day	14% 6% 2 5% 5% 4 5% 5% 7% 10% 37%	2660
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 4 6% 9% 38%	2660
	21st to end	Day	10% 5% 2 6% 5% 5% 7% 4 7% 9% 40%	2660
July	1st to 10th	Day	8% 5% 2 7% 6% 6% 6% 5% 8% 11% 35%	4440
	11th to 20th	Day	11% 7% 2 6% 5% 6% 6% 5% 7% 9% 36%	4440
	21st to end	Day	12% 8% 3 8% 6% 6% 6% 5% 7% 8% 31%	4814
August	1st to 10th	Day	19% 6% 2 7% 5% 4 5% 4 7% 8% 32%	4097
	11th to 20th	Day	12% 6% 2 7% 4 4 5% 4 6% 9% 40%	3730
	21st to end	Day	10% 5% 2 5% 4 4 5% 3 6% 10% 46%	4180
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 3 4 7% 46%	2280
	11th to 20th	Day	13% 5% 2 4 4 4 4 4 5% 7% 49%	2201
	21st to end	Day	19% 6% 3 7% 4 3 4 3 5% 6% 39%	2090
October	1st to 10th	Day	20% 7% 2 5% 3 3 4 3 5% 7% 43%	1981
	11th to 20th	Day	15% 5% 2 4 4 4 4 2 4 5% 50%	1900
	21st to end	Day	18% 6% 3 5% 3 3 4 4 4 6% 45%	1955
November	1st to 10th	Day	13% 7% 2 5% 3 3 3 2 4 5% 52%	1698
	11th to 20th	Day	16% 5% 3 5% 3 3 2 4 5% 5% 48%	1710
	21st to end	Day	15% 7% 2 5% 4 4 4 3 4 6% 46%	1649
December	1st to 10th	Day	18% 7% 3 7% 4 3 4 3 6% 7% 39%	1520
	11th to 20th	Day	19% 7% 3 4 3 3 3 4 4 5% 45%	1906
	21st to end	Day	18% 7% 2 6% 6% 6% 4 4 5% 7% 35%	2772
January	1st to 10th	Night	17% 7% 2 4 4 3 3 3 4 6% 46%	4429
	11th to 20th	Night	17% 10% 2 6% 4 3 3 3 4 5% 44%	4440
	21st to end	Night	24% 10% 2 6% 4 3 3 3 4 5% 35%	4593
February	1st to 10th	Night	16% 10% 2 5% 4 3 3 3 4 6% 42%	2453
	11th to 20th	Night	18% 8% 3 7% 4 3 3 3 5% 5% 41%	2218
	21st to end	Night	19% 8% 2 4 3 3 3 3 5% 6% 43%	1884
March	1st to 10th	Night	23% 11% 2 6% 4 3 2 2 3 5% 38%	3724
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 47%	3607
	21st to end	Night	20% 9% 3 6% 3 3 3 3 4 4 42%	3505
April	1st to 10th	Night	17% 9% 2 6% 4 4 4 4 5% 5% 40%	1900
	11th to 20th	Night	16% 8% 3 8% 4 4 3 3 5% 7% 41%	1875
	21st to end	Night	18% 7% 2 5% 3 3 4 3 5% 7% 43%	1897
May	1st to 10th	Night	23% 10% 4 8% 4 4 4 3 5% 8% 28%	2834
	11th to 20th	Night	27% 9% 2 6% 4 3 3 3 4 5% 33%	2570
	21st to end	Night	15% 6% 3 6% 4 4 4 4 6% 10% 40%	2738
June	1st to 10th	Night	15% 6% 2 6% 4 3 4 4 5% 8% 41%	1520
	11th to 20th	Night	14% 6% 2 6% 5% 4 4 3 6% 9% 41%	1520
	21st to end	Night	8% 6% 2 5% 6% 5% 5% 6% 8% 9% 40%	1520
July	1st to 10th	Night	7% 6% 3 9% 6% 5% 6% 5% 8% 10% 37%	2520
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 5% 7% 10% 37%	2520
	21st to end	Night	16% 8% 2 7% 4 4 5% 4 7% 9% 34%	2739
August	1st to 10th	Night	22% 7% 2 6% 4 4 5% 4 6% 8% 31%	2785
	11th to 20th	Night	13% 7% 2 7% 5% 4 5% 4 6% 8% 40%	3097
	21st to end	Night	8% 5% 2 5% 4 3 4 3 6% 8% 52%	3476
September	1st to 10th	Night	13% 6% 2 6% 5% 5% 4 3 4 6% 45%	1900
	11th to 20th	Night	12% 5% 2 5% 3 4 3 3 5% 6% 52%	1977
	21st to end	Night	19% 7% 3 7% 4 3 4 2 4 6% 42%	2090
October	1st to 10th	Night	19% 6% 2 6% 3 3 4 4 5% 6% 43%	2195
	11th to 20th	Night	14% 4 1 5% 4 4 5% 2 4 6% 51%	2280
	21st to end	Night	19% 7% 2 5% 3 3 3 3 4 6% 45%	2641
November	1st to 10th	Night	13% 5% 1 5% 4 4 4 3 4 6% 53%	2453
	11th to 20th	Night	17% 7% 2 5% 4 3 3 3 3 5% 47%	2470
	21st to end	Night	14% 5% 1 6% 4 4 4 3 5% 6% 47%	2527
December	1st to 10th	Night	19% 8% 2 6% 4 3 4 3 5% 5% 40%	2660
	11th to 20th	Night	19% 5% 2 5% 4 3 4 4 5% 7% 43%	3288
	21st to end	Night	17% 9% 3 6% 4 4 4 3 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	39% 5% 11% 27% 14% 3	2518
	11th to 20th	Day	45% 5% 12% 22% 14% 2	2520
	21st to end	Day	54% 6% 8% 20% 10% 2	3060
February	1st to 10th	Day	45% 5% 14% 23% 13% 2	1725
	11th to 20th	Day	43% 6% 9% 24% 16% 3	1857
	21st to end	Day	46% 5% 11% 20% 13% 5%	1570
March	1st to 10th	Day	48% 6% 10% 25% 9% 2	3119
	11th to 20th	Day	33% 6% 13% 32% 14% 3	3349
	21st to end	Day	44% 5% 9% 17% 21% 5%	4126
April	1st to 10th	Day	43% 5% 11% 20% 16% 5%	2280
	11th to 20th	Day	39% 7% 12% 22% 16% 3	2254
	21st to end	Day	41% 7% 12% 18% 18% 4	2280
May	1st to 10th	Day	53% 9% 12% 14% 10% 1	4120
	11th to 20th	Day	52% 8% 13% 18% 9% 1	4356
	21st to end	Day	35% 9% 12% 25% 17% 2	4837
June	1st to 10th	Day	39% 10% 14% 21% 15% 2	2660
	11th to 20th	Day	40% 10% 14% 23% 12% 2	2660
	21st to end	Day	37% 10% 15% 22% 16% 1	2660
July	1st to 10th	Day	39% 11% 15% 19% 15% 1	4370
	11th to 20th	Day	41% 8% 17% 20% 12% 1	4365
	21st to end	Day	47% 8% 12% 17% 14% 1	4661
August	1st to 10th	Day	46% 9% 15% 21% 8%	4083
	11th to 20th	Day	39% 8% 13% 27% 12% 1	3766
	21st to end	Day	32% 7% 12% 28% 19% 2	4180
September	1st to 10th	Day	37% 7% 13% 20% 20% 2	2280
	11th to 20th	Day	35% 5% 13% 22% 24% 2	2201
	21st to end	Day	45% 6% 10% 17% 20% 2	2090
October	1st to 10th	Day	36% 5% 12% 19% 23% 5%	3293
	11th to 20th	Day	24% 4 11% 23% 32% 5%	3140
	21st to end	Day	27% 3 15% 25% 26% 4	3193
November	1st to 10th	Day	35% 3 13% 26% 20% 2	1698
	11th to 20th	Day	39% 5% 10% 22% 22% 3	1710
	21st to end	Day	39% 4 13% 29% 12% 2	1649
December	1st to 10th	Day	44% 5% 15% 21% 14% 1	1520
	11th to 20th	Day	41% 5% 13% 25% 14% 2	1906
	21st to end	Day	45% 9% 12% 24% 10% 1	2772
January	1st to 10th	Night	38% 4 10% 31% 12% 4	4429
	11th to 20th	Night	44% 4 12% 25% 13% 3	4440
	21st to end	Night	51% 5% 8% 22% 13% 1	4593
February	1st to 10th	Night	43% 5% 14% 23% 13% 2	2453
	11th to 20th	Night	44% 5% 9% 19% 18% 5%	2220
	21st to end	Night	41% 5% 9% 24% 17% 4	1884
March	1st to 10th	Night	49% 4 8% 24% 11% 3	3734
	11th to 20th	Night	36% 6% 13% 26% 16% 3	3608
	21st to end	Night	46% 4 7% 15% 22% 6%	3505
April	1st to 10th	Night	44% 6% 10% 18% 18% 4	1900
	11th to 20th	Night	43% 6% 10% 18% 21% 2	1875
	21st to end	Night	41% 6% 9% 20% 19% 4	1897
May	1st to 10th	Night	53% 8% 11% 17% 10% 1	2840
	11th to 20th	Night	54% 6% 14% 15% 10% 2	2571
	21st to end	Night	38% 10% 13% 21% 15% 2	2739
June	1st to 10th	Night	40% 8% 11% 21% 18% 1	1520
	11th to 20th	Night	39% 8% 14% 26% 12% 1	1520
	21st to end	Night	36% 10% 16% 22% 15% 2	1520
July	1st to 10th	Night	41% 9% 17% 18% 13% 2	2480
	11th to 20th	Night	40% 8% 16% 24% 11% 1	2472
	21st to end	Night	45% 8% 15% 15% 15% 2	2651
August	1st to 10th	Night	49% 9% 17% 16% 8% 1	2775
	11th to 20th	Night	40% 7% 12% 28% 12% 1	3127
	21st to end	Night	30% 6% 11% 30% 21% 1	3476
September	1st to 10th	Night	40% 7% 11% 22% 19% 2	1900
	11th to 20th	Night	33% 5% 12% 22% 24% 4	1977
	21st to end	Night	44% 6% 7% 22% 19% 2	2090
October	1st to 10th	Night	38% 6% 11% 22% 21% 2	3663
	11th to 20th	Night	24% 4 10% 26% 31% 5%	3779
	21st to end	Night	28% 4 11% 30% 24% 3	4340
November	1st to 10th	Night	34% 4 12% 25% 21% 4	2453
	11th to 20th	Night	40% 5% 8% 23% 19% 5%	2470
	21st to end	Night	37% 5% 13% 27% 16% 1	2527
December	1st to 10th	Night	45% 6% 11% 23% 14% 2	2660
	11th to 20th	Night	40% 5% 13% 20% 17% 4	3288
	21st to end	Night	45% 6% 13% 23% 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	17% 19% 38% 19% 6% 1	180
	11th to 20th	Day	21% 31% 31% 14% 3	180
	21st to end	Day	21% 16% 36% 20% 6% 1	279
February	1st to 10th	Day	24% 16% 38% 18% 3 1	285
	11th to 20th	Day	23% 20% 37% 19% 1	456
	21st to end	Day	22% 20% 34% 21% 4	382
March	1st to 10th	Day	19% 17% 39% 20% 5%	460
	11th to 20th	Day	17% 17% 42% 18% 5% 1	460
	21st to end	Day	25% 16% 34% 19% 5%	506
April	1st to 10th	Day	22% 15% 37% 19% 6% 1	460
	11th to 20th	Day	18% 14% 35% 21% 10% 2	452
	21st to end	Day	24% 12% 35% 23% 6% 1	460
May	1st to 10th	Day	25% 9% 34% 21% 9% 2	463
	11th to 20th	Day	22% 5% 34% 28% 10% 1	487
	21st to end	Day	20% 4 21% 29% 22% 3	529
June	1st to 10th	Day	14% 7% 26% 33% 17% 3	490
	11th to 20th	Day	13% 6% 29% 33% 15% 3	490
	21st to end	Day	12% 4 25% 38% 18% 3	490
July	1st to 10th	Day	10% 4 21% 35% 23% 7%	485
	11th to 20th	Day	10% 2 17% 37% 27% 7%	484
	21st to end	Day	12% 4 24% 37% 20% 3	532
August	1st to 10th	Day	12% 3 17% 38% 23% 7%	486
	11th to 20th	Day	13% 4 16% 34% 27% 6%	479
	21st to end	Day	12% 4 21% 35% 20% 9%	539
September	1st to 10th	Day	16% 6% 21% 29% 19% 9%	490
	11th to 20th	Day	13% 3 23% 34% 18% 9%	490
	21st to end	Day	26% 6% 24% 27% 14% 3	490
October	1st to 10th	Day	24% 6% 23% 23% 18% 6%	490
	11th to 20th	Day	16% 11% 29% 26% 14% 4	490
	21st to end	Day	20% 10% 33% 24% 11% 2	467
November	1st to 10th	Day	17% 9% 34% 24% 14% 2	374
	11th to 20th	Day	19% 18% 33% 22% 9%	370
	21st to end	Day	17% 14% 33% 26% 9% 1	309
December	1st to 10th	Day	18% 21% 39% 13% 8% 1	180
	11th to 20th	Day	28% 18% 29% 18% 7%	180
	21st to end	Day	22% 13% 37% 19% 8%	198
January	1st to 10th	Night	20% 15% 42% 20% 4	760
	11th to 20th	Night	23% 15% 36% 22% 4	760
	21st to end	Night	19% 15% 43% 22% 2	836
February	1st to 10th	Night	21% 13% 40% 24% 2	760
	11th to 20th	Night	22% 19% 42% 15% 1	743
	21st to end	Night	23% 17% 35% 22% 3	628
March	1st to 10th	Night	20% 13% 38% 24% 4	760
	11th to 20th	Night	21% 13% 40% 20% 5% 1	760
	21st to end	Night	20% 10% 40% 24% 6%	836
April	1st to 10th	Night	21% 12% 39% 23% 5%	760
	11th to 20th	Night	19% 10% 34% 31% 6%	751
	21st to end	Night	20% 8% 35% 31% 6% 1	757
May	1st to 10th	Night	23% 10% 31% 27% 9%	570
	11th to 20th	Night	23% 7% 34% 30% 6%	423
	21st to end	Night	16% 4 21% 38% 19% 2	411
June	1st to 10th	Night	17% 6% 22% 38% 17% 1	380
	11th to 20th	Night	14% 3 22% 43% 17%	380
	21st to end	Night	8% 4 19% 49% 18% 1	380
July	1st to 10th	Night	12% 4 20% 41% 22% 2	370
	11th to 20th	Night	10% 3 17% 43% 25% 2	368
	21st to end	Night	12% 2 19% 46% 20%	416
August	1st to 10th	Night	10% 3 16% 45% 22% 3	540
	11th to 20th	Night	12% 3 16% 39% 28% 2	750
	21st to end	Night	13% 3 14% 40% 26% 3	836
September	1st to 10th	Night	15% 3 22% 36% 19% 4	760
	11th to 20th	Night	15% 3 20% 35% 22% 6%	760
	21st to end	Night	21% 5% 23% 32% 16% 2	760
October	1st to 10th	Night	22% 7% 24% 26% 17% 3	760
	11th to 20th	Night	17% 9% 29% 34% 12% 1	760
	21st to end	Night	22% 7% 36% 25% 9% 1	836
November	1st to 10th	Night	15% 8% 37% 27% 12% 1	755
	11th to 20th	Night	19% 14% 33% 25% 9% 1	760
	21st to end	Night	15% 14% 39% 24% 7% 1	760
December	1st to 10th	Night	23% 16% 34% 19% 7% 1	760
	11th to 20th	Night	21% 11% 41% 24% 4	760
	21st to end	Night	21% 11% 41% 24% 3	836

Page generated at 2024-11-01 22:47:30. Version ac07

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