Deep River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deep River clear sky chart from 2005-11-06 to 2026-08-15.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	144923
	Night	16% 13% 4 10% 6% 5% 4 3 5% 6% 28%	136894
Transparency	Day	52% 5% 11% 21% 9% 1	148443
	Night	55% 5% 11% 18% 9% 1	141464
Seeing	Day	24% 15% 32% 19% 8% 2	16843
	Night	24% 12% 29% 25% 9% 1	25634

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	14% 16% 8% 17% 8% 5% 4 3 4 5% 17%	4661
	11th to 20th	Day	9% 23% 8% 17% 8% 4 4 2 4 4 16%	4650
	21st to end	Day	8% 15% 7% 17% 10% 6% 5% 3 4 5% 19%	5541
February	1st to 10th	Day	11% 17% 6% 14% 8% 6% 5% 4 5% 4 20%	1890
	11th to 20th	Day	11% 17% 6% 14% 5% 6% 5% 4 4 5% 23%	1843
	21st to end	Day	17% 16% 6% 11% 7% 5% 5% 3 4 4 23%	1640
March	1st to 10th	Day	20% 16% 5% 11% 5% 4 3 3 5% 5% 25%	4800
	11th to 20th	Day	14% 14% 5% 11% 6% 5% 4 3 5% 7% 26%	5090
	21st to end	Day	17% 12% 4 9% 5% 5% 3 3 3 5% 34%	5741
April	1st to 10th	Day	22% 14% 3 8% 5% 4 3 3 4 5% 29%	2520
	11th to 20th	Day	22% 12% 3 8% 4 4 3 3 4 6% 32%	2508
	21st to end	Day	21% 10% 3 8% 5% 5% 3 3 4 5% 32%	2730
May	1st to 10th	Day	18% 10% 3 8% 5% 5% 5% 4 6% 8% 28%	8211
	11th to 20th	Day	17% 8% 3 8% 4 4 4 3 5% 7% 35%	8221
	21st to end	Day	19% 9% 3 7% 5% 4 4 3 5% 7% 35%	9060
June	1st to 10th	Day	19% 9% 3 8% 6% 5% 4 4 6% 6% 30%	2940
	11th to 20th	Day	15% 6% 2 6% 5% 5% 5% 4 6% 8% 36%	2959
	21st to end	Day	18% 7% 3 7% 5% 5% 6% 4 6% 7% 32%	3150
July	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 8% 36%	8483
	11th to 20th	Day	11% 4 2 6% 4 5% 5% 4 6% 9% 45%	8280
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 10% 41%	8993
August	1st to 10th	Day	13% 6% 3 8% 6% 6% 6% 5% 7% 9% 32%	4484
	11th to 20th	Day	16% 7% 2 7% 5% 5% 4 4 6% 8% 36%	4226
	21st to end	Day	10% 6% 2 7% 4 4 6% 5% 7% 11% 39%	4416
September	1st to 10th	Day	14% 7% 3 7% 4 4 4 4 6% 7% 41%	2400
	11th to 20th	Day	13% 7% 2 6% 5% 4 4 3 5% 8% 44%	2400
	21st to end	Day	21% 8% 2 6% 4 3 5% 3 5% 7% 35%	2095
October	1st to 10th	Day	19% 9% 3 8% 5% 5% 4 3 5% 6% 34%	2000
	11th to 20th	Day	24% 14% 4 8% 5% 5% 4 3 5% 5% 24%	2000
	21st to end	Day	28% 14% 4 8% 4 4 4 3 5% 6% 21%	2105
November	1st to 10th	Day	17% 13% 4 9% 5% 4 5% 4 5% 5% 29%	1732
	11th to 20th	Day	19% 17% 6% 11% 5% 6% 6% 3 4 4 20%	1680
	21st to end	Day	25% 20% 5% 12% 5% 5% 4 3 3 4 14%	1680
December	1st to 10th	Day	17% 22% 6% 12% 7% 6% 6% 3 4 4 12%	2680
	11th to 20th	Day	16% 20% 7% 14% 7% 4 4 2 3 3 21%	3066
	21st to end	Day	20% 21% 6% 13% 6% 4 4 3 3 4 17%	4048
January	1st to 10th	Night	12% 19% 9% 18% 8% 5% 4 3 4 4 15%	8234
	11th to 20th	Night	11% 18% 8% 18% 8% 5% 4 3 4 4 16%	8235
	21st to end	Night	7% 17% 8% 16% 8% 8% 6% 4 4 5% 19%	8623
February	1st to 10th	Night	12% 14% 6% 13% 9% 6% 5% 5% 4 5% 22%	2730
	11th to 20th	Night	14% 15% 6% 12% 7% 5% 5% 3 5% 5% 24%	2663
	21st to end	Night	14% 17% 6% 12% 7% 6% 4 3 4 5% 22%	2165
March	1st to 10th	Night	18% 17% 5% 9% 6% 4 4 4 4 4 26%	5256
	11th to 20th	Night	12% 16% 5% 10% 6% 4 5% 4 6% 7% 25%	5089
	21st to end	Night	17% 12% 4 11% 5% 4 4 3 5% 5% 30%	5432
April	1st to 10th	Night	20% 13% 4 9% 5% 4 4 3 5% 5% 28%	2100
	11th to 20th	Night	19% 11% 4 6% 5% 3 4 3 5% 5% 35%	2075
	21st to end	Night	22% 9% 2 8% 5% 4 5% 3 4 5% 31%	1895
May	1st to 10th	Night	21% 8% 3 8% 5% 4 5% 4 6% 8% 29%	4684
	11th to 20th	Night	16% 8% 3 8% 4 4 4 3 5% 7% 39%	4639
	21st to end	Night	18% 7% 3 6% 5% 5% 5% 4 5% 6% 37%	5114
June	1st to 10th	Night	16% 8% 3 6% 6% 5% 5% 4 6% 7% 35%	1680
	11th to 20th	Night	15% 7% 3 5% 4 5% 4 4 5% 8% 40%	1650
	21st to end	Night	17% 6% 3 6% 4 5% 5% 4 7% 8% 36%	1470
July	1st to 10th	Night	13% 6% 3 8% 4 6% 6% 4 7% 8% 37%	4452
	11th to 20th	Night	12% 6% 2 6% 3 4 3 4 5% 7% 47%	4680
	21st to end	Night	11% 7% 2 7% 4 4 4 3 5% 7% 45%	5084
August	1st to 10th	Night	13% 5% 2 5% 4 4 5% 4 6% 8% 44%	2868
	11th to 20th	Night	16% 7% 2 5% 4 4 5% 4 6% 6% 41%	2911
	21st to end	Night	14% 5% 2 6% 4 4 4 4 7% 8% 42%	3449
September	1st to 10th	Night	12% 6% 3 6% 4 4 4 3 6% 8% 45%	2000
	11th to 20th	Night	15% 5% 2 5% 4 4 3 2 5% 6% 48%	2000
	21st to end	Night	20% 7% 3 7% 4 3 3 3 4 7% 40%	2302
October	1st to 10th	Night	20% 8% 2 6% 4 3 4 3 5% 6% 38%	2400
	11th to 20th	Night	22% 12% 4 8% 5% 4 4 3 5% 4 28%	2400
	21st to end	Night	24% 13% 3 8% 4 5% 4 3 5% 5% 25%	2734
November	1st to 10th	Night	19% 14% 3 9% 5% 4 4 3 5% 5% 29%	2782
	11th to 20th	Night	19% 16% 5% 10% 6% 5% 5% 3 4 4 23%	2940
	21st to end	Night	24% 19% 4 12% 6% 4 3 3 4 5% 16%	2940
December	1st to 10th	Night	19% 22% 5% 12% 7% 5% 5% 4 5% 4 12%	4720
	11th to 20th	Night	19% 18% 6% 14% 6% 4 3 2 3 4 21%	5348
	21st to end	Night	23% 20% 4 13% 6% 3 3 2 3 4 18%	7150

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	69% 5% 9% 12% 5%	4662
	11th to 20th	Day	72% 3 7% 10% 8%	4680
	21st to end	Day	66% 4 8% 13% 8% 1	5541
February	1st to 10th	Day	67% 3 8% 15% 6% 1	1890
	11th to 20th	Day	62% 4 11% 13% 8% 1	1852
	21st to end	Day	64% 3 7% 15% 10% 1	1640
March	1st to 10th	Day	61% 3 9% 12% 12% 2	4803
	11th to 20th	Day	56% 5% 14% 15% 9% 1	5090
	21st to end	Day	53% 3 7% 20% 14% 2	5741
April	1st to 10th	Day	57% 4 7% 19% 11% 3	2520
	11th to 20th	Day	55% 3 6% 21% 13% 2	2508
	21st to end	Day	55% 3 7% 17% 15% 3	2730
May	1st to 10th	Day	49% 7% 9% 22% 9% 4	8223
	11th to 20th	Day	47% 6% 11% 25% 11% 1	8225
	21st to end	Day	48% 5% 10% 21% 14% 2	9061
June	1st to 10th	Day	53% 5% 10% 19% 13% 1	2940
	11th to 20th	Day	44% 5% 12% 25% 13% 2	2959
	21st to end	Day	47% 7% 12% 21% 12% 1	3150
July	1st to 10th	Day	41% 8% 14% 25% 11% 1	8414
	11th to 20th	Day	32% 7% 15% 35% 10% 1	8205
	21st to end	Day	36% 7% 17% 31% 9%	8795
August	1st to 10th	Day	45% 7% 15% 24% 9%	4470
	11th to 20th	Day	42% 7% 17% 26% 8%	4265
	21st to end	Day	35% 7% 16% 31% 10% 1	4416
September	1st to 10th	Day	40% 7% 15% 27% 12%	2400
	11th to 20th	Day	39% 6% 14% 30% 11% 1	2400
	21st to end	Day	49% 5% 12% 24% 9%	2095
October	1st to 10th	Day	50% 7% 11% 25% 6% 1	3260
	11th to 20th	Day	54% 6% 14% 20% 5%	3240
	21st to end	Day	60% 6% 15% 14% 4 1	3382
November	1st to 10th	Day	54% 6% 13% 20% 6%	1732
	11th to 20th	Day	65% 5% 11% 12% 5% 1	1680
	21st to end	Day	74% 4 10% 8% 5%	1680
December	1st to 10th	Day	73% 5% 9% 10% 2	2680
	11th to 20th	Day	70% 4 5% 14% 7%	3066
	21st to end	Day	72% 4 6% 14% 4	4048
January	1st to 10th	Night	73% 4 10% 10% 3	8234
	11th to 20th	Night	71% 4 9% 10% 6%	8280
	21st to end	Night	67% 5% 7% 11% 11%	8623
February	1st to 10th	Night	62% 5% 10% 16% 6% 1	2730
	11th to 20th	Night	62% 3 10% 18% 6% 1	2665
	21st to end	Night	64% 3 8% 17% 7% 1	2165
March	1st to 10th	Night	60% 4 10% 14% 10% 3	5266
	11th to 20th	Night	55% 7% 14% 15% 8% 1	5090
	21st to end	Night	55% 5% 7% 19% 13% 2	5432
April	1st to 10th	Night	56% 5% 7% 18% 12% 2	2100
	11th to 20th	Night	51% 5% 8% 23% 13% 2	2075
	21st to end	Night	53% 4 6% 19% 15% 2	1895
May	1st to 10th	Night	49% 7% 9% 22% 10% 3	4690
	11th to 20th	Night	43% 7% 12% 21% 13% 3	4640
	21st to end	Night	46% 6% 10% 23% 13% 2	5115
June	1st to 10th	Night	47% 5% 10% 22% 14% 1	1680
	11th to 20th	Night	40% 6% 11% 26% 15% 2	1650
	21st to end	Night	43% 8% 14% 23% 12% 1	1470
July	1st to 10th	Night	40% 8% 16% 24% 11% 1	4412
	11th to 20th	Night	34% 7% 16% 30% 13%	4632
	21st to end	Night	38% 6% 12% 31% 12%	4967
August	1st to 10th	Night	36% 6% 17% 27% 14%	2858
	11th to 20th	Night	39% 7% 18% 26% 9%	2938
	21st to end	Night	36% 8% 17% 26% 11% 2	3449
September	1st to 10th	Night	38% 6% 14% 29% 13%	2000
	11th to 20th	Night	37% 5% 15% 33% 11%	2000
	21st to end	Night	44% 5% 13% 27% 11%	2302
October	1st to 10th	Night	40% 6% 14% 28% 11%	3920
	11th to 20th	Night	51% 7% 15% 20% 7%	3899
	21st to end	Night	54% 7% 17% 16% 7%	4407
November	1st to 10th	Night	56% 5% 13% 18% 8%	2782
	11th to 20th	Night	63% 4 11% 15% 6%	2940
	21st to end	Night	71% 5% 10% 11% 3	2940
December	1st to 10th	Night	72% 6% 12% 8% 2	4720
	11th to 20th	Night	67% 4 7% 11% 10%	5348
	21st to end	Night	72% 4 6% 12% 7%	7150

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	21% 22% 40% 15% 2	220
	11th to 20th	Day	30% 15% 38% 14% 3 1	220
	21st to end	Day	20% 18% 36% 20% 5%	319
February	1st to 10th	Day	27% 24% 34% 11% 4 1	330
	11th to 20th	Day	23% 30% 39% 8%	330
	21st to end	Day	31% 20% 34% 14% 1	356
March	1st to 10th	Day	25% 21% 37% 14% 3	540
	11th to 20th	Day	28% 20% 32% 16% 3 1	540
	21st to end	Day	31% 21% 28% 15% 4	594
April	1st to 10th	Day	33% 21% 27% 14% 5% 1	540
	11th to 20th	Day	34% 17% 24% 14% 7% 3	532
	21st to end	Day	30% 18% 31% 15% 5% 1	540
May	1st to 10th	Day	27% 15% 33% 16% 6% 2	543
	11th to 20th	Day	24% 17% 31% 17% 9% 2	567
	21st to end	Day	24% 15% 31% 21% 7% 1	617
June	1st to 10th	Day	24% 13% 34% 22% 7% 1	570
	11th to 20th	Day	21% 12% 35% 20% 10% 2	589
	21st to end	Day	20% 14% 32% 21% 10% 2	780
July	1st to 10th	Day	14% 9% 33% 33% 9% 2	639
	11th to 20th	Day	13% 11% 37% 24% 12% 3	564
	21st to end	Day	13% 10% 32% 30% 13% 2	620
August	1st to 10th	Day	16% 7% 31% 30% 10% 5%	566
	11th to 20th	Day	17% 8% 24% 30% 14% 6%	535
	21st to end	Day	17% 12% 31% 23% 11% 6%	583
September	1st to 10th	Day	19% 9% 32% 21% 12% 6%	530
	11th to 20th	Day	15% 10% 24% 25% 18% 9%	530
	21st to end	Day	22% 13% 26% 23% 12% 4	530
October	1st to 10th	Day	27% 13% 25% 20% 12% 3	530
	11th to 20th	Day	27% 20% 32% 15% 4 1	530
	21st to end	Day	33% 16% 29% 18% 4	531
November	1st to 10th	Day	30% 18% 29% 17% 5%	306
	11th to 20th	Day	26% 16% 40% 10% 6%	220
	21st to end	Day	35% 20% 34% 7% 3 1	220
December	1st to 10th	Day	30% 14% 40% 15% 3	220
	11th to 20th	Day	32% 23% 32% 9% 3 1	220
	21st to end	Day	33% 19% 32% 12% 5%	242
January	1st to 10th	Night	27% 14% 36% 20% 3	840
	11th to 20th	Night	29% 13% 30% 23% 6%	840
	21st to end	Night	18% 13% 33% 27% 7% 1	924
February	1st to 10th	Night	19% 17% 36% 23% 5% 1	840
	11th to 20th	Night	23% 16% 37% 19% 4	823
	21st to end	Night	24% 17% 29% 25% 4	692
March	1st to 10th	Night	24% 17% 35% 20% 3	840
	11th to 20th	Night	23% 20% 32% 19% 6%	840
	21st to end	Night	22% 16% 32% 22% 6% 1	924
April	1st to 10th	Night	29% 13% 30% 23% 5%	840
	11th to 20th	Night	26% 15% 29% 22% 8%	831
	21st to end	Night	26% 13% 29% 23% 9% 1	635
May	1st to 10th	Night	24% 9% 29% 29% 10%	431
	11th to 20th	Night	22% 9% 32% 28% 8%	414
	21st to end	Night	20% 9% 31% 31% 9%	455
June	1st to 10th	Night	18% 7% 32% 35% 7%	420
	11th to 20th	Night	20% 7% 29% 31% 13%	420
	21st to end	Night	21% 6% 24% 35% 14%	420
July	1st to 10th	Night	11% 5% 32% 38% 13% 1	410
	11th to 20th	Night	14% 6% 23% 41% 15%	408
	21st to end	Night	10% 5% 27% 41% 17% 1	460
August	1st to 10th	Night	15% 5% 23% 35% 21% 1	542
	11th to 20th	Night	13% 3 21% 39% 22% 2	606
	21st to end	Night	16% 7% 27% 31% 17% 2	795
September	1st to 10th	Night	15% 6% 31% 29% 18% 2	800
	11th to 20th	Night	19% 5% 24% 28% 22% 3	800
	21st to end	Night	23% 9% 22% 30% 16% 1	800
October	1st to 10th	Night	23% 9% 29% 25% 12% 1	800
	11th to 20th	Night	29% 13% 28% 21% 8% 1	800
	21st to end	Night	31% 12% 28% 25% 4	880
November	1st to 10th	Night	29% 13% 27% 25% 6% 1	820
	11th to 20th	Night	27% 16% 32% 17% 8%	840
	21st to end	Night	35% 15% 25% 21% 5%	840
December	1st to 10th	Night	32% 16% 29% 17% 5%	840
	11th to 20th	Night	29% 14% 31% 22% 4 1	840
	21st to end	Night	34% 15% 27% 22% 3	924

Page generated at 2026-08-12 03:37:18. Version ac07

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