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 2025-04-11.

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% 12% 4 9% 5% 5% 4 3 5% 6% 29%	113917
	Night	16% 13% 4 10% 6% 5% 4 3 5% 5% 28%	114302
Transparency	Day	54% 5% 11% 20% 9% 1	117482
	Night	56% 5% 11% 18% 9% 1	118901
Seeing	Day	24% 15% 31% 19% 8% 2	15052
	Night	24% 12% 29% 25% 9% 1	24106

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% 17% 8% 18% 9% 6% 4 3 3 4 15%	3597
	11th to 20th	Day	10% 17% 7% 17% 9% 5% 5% 3 4 4 18%	3570
	21st to end	Day	11% 19% 8% 14% 7% 5% 4 3 4 6% 19%	4282
February	1st to 10th	Day	11% 17% 6% 14% 9% 6% 5% 3 4 4 19%	1800
	11th to 20th	Day	12% 18% 6% 13% 5% 5% 5% 4 4 5% 23%	1753
	21st to end	Day	18% 16% 5% 10% 6% 5% 5% 3 4 4 23%	1564
March	1st to 10th	Day	20% 16% 5% 11% 5% 4 3 3 5% 5% 24%	4696
	11th to 20th	Day	13% 14% 5% 11% 6% 5% 4 3 5% 7% 26%	4980
	21st to end	Day	17% 12% 4 9% 5% 5% 3 3 3 5% 34%	5617
April	1st to 10th	Day	22% 14% 3 8% 4 3 3 3 4 5% 30%	2400
	11th to 20th	Day	22% 11% 3 8% 4 4 3 3 4 6% 33%	2266
	21st to end	Day	22% 10% 3 8% 5% 5% 3 3 4 5% 32%	2470
May	1st to 10th	Day	19% 11% 4 8% 5% 4 4 3 5% 7% 30%	4414
	11th to 20th	Day	17% 8% 3 7% 4 4 4 3 6% 8% 35%	4398
	21st to end	Day	18% 7% 3 6% 5% 5% 4 3 5% 8% 36%	4837
June	1st to 10th	Day	19% 10% 3 8% 6% 5% 4 4 6% 6% 29%	2660
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 4 6% 9% 37%	2677
	21st to end	Day	19% 7% 3 7% 5% 5% 6% 4 6% 7% 31%	2850
July	1st to 10th	Day	14% 7% 3 8% 6% 6% 5% 4 7% 7% 33%	4546
	11th to 20th	Day	14% 6% 3 7% 5% 5% 5% 5% 6% 8% 37%	4440
	21st to end	Day	11% 5% 2 6% 4 4 4 4 7% 8% 45%	4814
August	1st to 10th	Day	13% 6% 3 8% 6% 6% 6% 5% 7% 9% 31%	4216
	11th to 20th	Day	17% 7% 2 6% 5% 5% 4 4 6% 8% 35%	4044
	21st to end	Day	10% 6% 2 7% 4 4 5% 5% 7% 11% 39%	4281
September	1st to 10th	Day	14% 7% 3 7% 4 4 4 4 5% 7% 41%	2280
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 3 5% 7% 44%	2280
	21st to end	Day	21% 8% 3 6% 4 3 5% 3 5% 7% 34%	1991
October	1st to 10th	Day	20% 9% 3 8% 5% 5% 4 3 5% 6% 33%	1900
	11th to 20th	Day	25% 14% 4 8% 5% 4 4 3 5% 5% 24%	1900
	21st to end	Day	29% 13% 4 8% 4 4 4 3 5% 6% 20%	2000
November	1st to 10th	Day	17% 13% 4 9% 5% 4 4 4 6% 5% 29%	1648
	11th to 20th	Day	19% 16% 5% 11% 5% 6% 6% 3 4 4 21%	1600
	21st to end	Day	25% 20% 5% 11% 5% 5% 4 4 3 4 14%	1600
December	1st to 10th	Day	18% 22% 6% 12% 7% 6% 6% 3 4 4 12%	2600
	11th to 20th	Day	16% 20% 7% 13% 7% 4 4 2 3 3 21%	2986
	21st to end	Day	21% 21% 6% 12% 6% 4 4 3 3 4 17%	3960
January	1st to 10th	Night	13% 21% 8% 17% 8% 5% 4 2 3 4 15%	6349
	11th to 20th	Night	11% 15% 7% 17% 8% 6% 5% 4 4 5% 18%	6315
	21st to end	Night	8% 20% 9% 15% 7% 7% 5% 3 4 4 18%	6657
February	1st to 10th	Night	12% 14% 6% 13% 9% 6% 5% 4 4 5% 21%	2600
	11th to 20th	Night	14% 15% 6% 12% 7% 5% 5% 3 4 5% 24%	2533
	21st to end	Night	14% 17% 5% 12% 7% 6% 4 4 4 5% 23%	2065
March	1st to 10th	Night	18% 17% 5% 9% 6% 4 4 4 4 4 26%	5141
	11th to 20th	Night	11% 16% 5% 10% 6% 4 5% 4 6% 7% 25%	4979
	21st to end	Night	17% 12% 4 11% 5% 4 4 3 5% 5% 30%	5314
April	1st to 10th	Night	19% 13% 4 9% 5% 4 4 3 5% 5% 28%	2000
	11th to 20th	Night	20% 11% 3 6% 5% 3 4 3 5% 5% 35%	1882
	21st to end	Night	23% 9% 3 8% 5% 4 4 3 4 5% 31%	1715
May	1st to 10th	Night	22% 9% 2 8% 5% 4 4 3 5% 7% 32%	2524
	11th to 20th	Night	16% 8% 3 10% 4 4 4 3 5% 7% 35%	2495
	21st to end	Night	14% 8% 3 7% 5% 5% 4 3 5% 6% 39%	2738
June	1st to 10th	Night	17% 8% 3 7% 6% 6% 5% 4 6% 7% 34%	1520
	11th to 20th	Night	15% 6% 3 5% 5% 5% 4 4 5% 8% 40%	1493
	21st to end	Night	17% 6% 3 6% 4 5% 5% 4 7% 8% 36%	1330
July	1st to 10th	Night	14% 7% 3 9% 4 6% 6% 4 6% 7% 36%	2396
	11th to 20th	Night	16% 7% 3 7% 3 4 4 4 4 7% 40%	2520
	21st to end	Night	11% 5% 1 5% 4 4 4 3 6% 8% 48%	2739
August	1st to 10th	Night	14% 5% 2 6% 4 4 5% 4 6% 7% 43%	2696
	11th to 20th	Night	16% 7% 2 5% 4 4 5% 4 6% 6% 40%	2785
	21st to end	Night	14% 5% 2 6% 4 4 4 4 7% 8% 42%	3343
September	1st to 10th	Night	13% 6% 3 6% 4 3 4 3 5% 8% 45%	1900
	11th to 20th	Night	16% 5% 2 6% 4 4 3 2 5% 6% 47%	1900
	21st to end	Night	20% 7% 3 7% 4 3 3 3 4 7% 40%	2186
October	1st to 10th	Night	21% 8% 2 6% 4 3 4 3 5% 6% 37%	2280
	11th to 20th	Night	22% 13% 4 8% 5% 4 4 3 5% 4 28%	2280
	21st to end	Night	25% 13% 3 8% 5% 5% 4 3 5% 5% 24%	2597
November	1st to 10th	Night	19% 14% 3 8% 5% 4 4 3 5% 5% 29%	2646
	11th to 20th	Night	19% 15% 5% 10% 6% 5% 5% 3 4 4 24%	2800
	21st to end	Night	24% 18% 4 12% 6% 4 3 3 4 5% 17%	2800
December	1st to 10th	Night	19% 22% 5% 12% 7% 5% 5% 4 5% 4 11%	4580
	11th to 20th	Night	20% 18% 6% 13% 6% 4 3 2 3 4 21%	5208
	21st to end	Night	23% 20% 4 13% 5% 3 3 2 3 4 18%	6996

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	73% 4 8% 10% 5%	3598
	11th to 20th	Day	69% 4 9% 11% 7%	3600
	21st to end	Day	65% 4 8% 13% 7% 1	4282
February	1st to 10th	Day	68% 3 8% 14% 6% 1	1800
	11th to 20th	Day	63% 4 12% 12% 9% 1	1762
	21st to end	Day	64% 3 7% 15% 10% 1	1564
March	1st to 10th	Day	61% 3 9% 12% 12% 2	4699
	11th to 20th	Day	55% 5% 15% 15% 9% 2	4980
	21st to end	Day	53% 3 6% 20% 14% 2	5617
April	1st to 10th	Day	57% 4 7% 19% 11% 3	2400
	11th to 20th	Day	54% 3 6% 22% 13% 2	2266
	21st to end	Day	55% 3 7% 16% 15% 3	2470
May	1st to 10th	Day	51% 6% 8% 23% 10% 2	4428
	11th to 20th	Day	46% 6% 11% 26% 10% 1	4402
	21st to end	Day	46% 5% 11% 19% 16% 3	4837
June	1st to 10th	Day	54% 5% 11% 18% 12% 1	2660
	11th to 20th	Day	43% 5% 12% 25% 13% 3	2677
	21st to end	Day	49% 7% 11% 20% 12% 1	2850
July	1st to 10th	Day	46% 7% 13% 25% 9% 1	4476
	11th to 20th	Day	40% 7% 15% 29% 8%	4365
	21st to end	Day	36% 6% 14% 34% 11%	4661
August	1st to 10th	Day	45% 7% 14% 25% 8%	4202
	11th to 20th	Day	43% 7% 17% 26% 7%	4083
	21st to end	Day	35% 7% 16% 31% 10% 1	4281
September	1st to 10th	Day	40% 6% 14% 27% 12%	2280
	11th to 20th	Day	40% 6% 14% 29% 11% 1	2280
	21st to end	Day	49% 5% 13% 24% 8%	1991
October	1st to 10th	Day	51% 7% 11% 24% 6% 1	3160
	11th to 20th	Day	54% 6% 15% 20% 5%	3140
	21st to end	Day	60% 6% 16% 14% 4 1	3277
November	1st to 10th	Day	54% 6% 14% 20% 6%	1648
	11th to 20th	Day	65% 5% 11% 13% 6% 1	1600
	21st to end	Day	74% 4 10% 8% 5%	1600
December	1st to 10th	Day	73% 5% 9% 10% 2	2600
	11th to 20th	Day	69% 4 5% 15% 7%	2986
	21st to end	Day	72% 4 6% 14% 4	3960
January	1st to 10th	Night	74% 3 10% 10% 3	6349
	11th to 20th	Night	68% 5% 10% 11% 6%	6360
	21st to end	Night	69% 4 6% 9% 10%	6657
February	1st to 10th	Night	63% 5% 10% 15% 7% 1	2600
	11th to 20th	Night	62% 3 10% 17% 6% 1	2535
	21st to end	Night	63% 3 9% 17% 7% 1	2065
March	1st to 10th	Night	61% 4 9% 14% 10% 3	5151
	11th to 20th	Night	55% 7% 14% 15% 8% 1	4980
	21st to end	Night	54% 5% 7% 19% 13% 2	5314
April	1st to 10th	Night	56% 4 7% 18% 12% 2	2000
	11th to 20th	Night	51% 4 8% 22% 13% 2	1882
	21st to end	Night	54% 4 6% 17% 15% 3	1715
May	1st to 10th	Night	50% 6% 9% 21% 10% 2	2530
	11th to 20th	Night	47% 7% 10% 23% 11% 2	2496
	21st to end	Night	45% 6% 10% 22% 14% 3	2739
June	1st to 10th	Night	48% 5% 11% 23% 12% 1	1520
	11th to 20th	Night	40% 6% 11% 26% 15% 2	1493
	21st to end	Night	43% 8% 13% 22% 12% 1	1330
July	1st to 10th	Night	43% 8% 15% 21% 12% 1	2356
	11th to 20th	Night	41% 7% 16% 27% 9% 1	2472
	21st to end	Night	34% 6% 13% 33% 13%	2651
August	1st to 10th	Night	36% 6% 16% 27% 14%	2686
	11th to 20th	Night	40% 7% 18% 26% 9%	2812
	21st to end	Night	36% 8% 17% 26% 11% 2	3343
September	1st to 10th	Night	38% 6% 14% 29% 13%	1900
	11th to 20th	Night	38% 5% 15% 31% 10%	1900
	21st to end	Night	45% 5% 13% 27% 10%	2186
October	1st to 10th	Night	41% 6% 14% 28% 11%	3800
	11th to 20th	Night	51% 7% 15% 20% 7%	3779
	21st to end	Night	54% 7% 17% 15% 7%	4270
November	1st to 10th	Night	55% 5% 14% 18% 8%	2646
	11th to 20th	Night	63% 4 11% 15% 6%	2800
	21st to end	Night	70% 5% 11% 12% 3	2800
December	1st to 10th	Night	73% 6% 12% 7% 2	4580
	11th to 20th	Night	67% 4 7% 12% 10%	5208
	21st to end	Night	72% 4 6% 12% 7%	6996

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% 23% 41% 14% 2	200
	11th to 20th	Day	28% 15% 39% 14% 3 2	200
	21st to end	Day	21% 18% 36% 19% 6%	290
February	1st to 10th	Day	28% 25% 33% 9% 3 1	300
	11th to 20th	Day	24% 30% 38% 7%	300
	21st to end	Day	32% 21% 33% 13%	328
March	1st to 10th	Day	25% 20% 37% 15% 3	500
	11th to 20th	Day	25% 21% 33% 17% 3 1	500
	21st to end	Day	31% 20% 27% 16% 5%	550
April	1st to 10th	Day	31% 21% 27% 14% 6% 1	500
	11th to 20th	Day	33% 18% 24% 16% 7% 3	452
	21st to end	Day	30% 17% 30% 16% 6% 1	460
May	1st to 10th	Day	27% 15% 33% 16% 7% 2	463
	11th to 20th	Day	23% 18% 28% 18% 10% 3	487
	21st to end	Day	21% 15% 32% 23% 8% 2	529
June	1st to 10th	Day	23% 13% 34% 23% 7% 1	490
	11th to 20th	Day	19% 10% 36% 21% 12% 2	507
	21st to end	Day	21% 15% 31% 21% 10% 2	680
July	1st to 10th	Day	14% 9% 32% 34% 9% 2	552
	11th to 20th	Day	13% 10% 37% 25% 13% 3	484
	21st to end	Day	14% 9% 30% 31% 14% 3	532
August	1st to 10th	Day	16% 8% 32% 28% 11% 5%	486
	11th to 20th	Day	18% 8% 22% 29% 16% 7%	479
	21st to end	Day	17% 11% 31% 23% 11% 6%	539
September	1st to 10th	Day	19% 9% 33% 21% 12% 7%	490
	11th to 20th	Day	16% 10% 25% 23% 18% 8%	490
	21st to end	Day	22% 13% 25% 24% 13% 4	490
October	1st to 10th	Day	28% 14% 25% 19% 11% 3	490
	11th to 20th	Day	28% 21% 31% 14% 5% 1	490
	21st to end	Day	34% 16% 28% 18% 4	492
November	1st to 10th	Day	29% 18% 29% 18% 5%	282
	11th to 20th	Day	25% 18% 41% 10% 7% 1	200
	21st to end	Day	34% 20% 35% 8% 3 1	200
December	1st to 10th	Day	31% 12% 40% 15% 3	200
	11th to 20th	Day	33% 23% 31% 10% 3 1	200
	21st to end	Day	32% 19% 33% 12% 5%	220
January	1st to 10th	Night	27% 14% 36% 19% 3	800
	11th to 20th	Night	29% 12% 29% 24% 7%	800
	21st to end	Night	18% 13% 33% 28% 8% 1	880
February	1st to 10th	Night	19% 17% 36% 22% 5% 1	800
	11th to 20th	Night	24% 17% 36% 19% 4	783
	21st to end	Night	25% 17% 29% 25% 4	660
March	1st to 10th	Night	24% 17% 34% 21% 4	800
	11th to 20th	Night	22% 19% 33% 19% 6%	800
	21st to end	Night	22% 16% 33% 22% 7% 1	880
April	1st to 10th	Night	28% 13% 30% 24% 5%	800
	11th to 20th	Night	26% 16% 29% 22% 8%	754
	21st to end	Night	26% 12% 29% 23% 9% 1	575
May	1st to 10th	Night	24% 7% 30% 28% 11%	390
	11th to 20th	Night	22% 9% 31% 29% 9%	374
	21st to end	Night	19% 9% 32% 30% 10%	411
June	1st to 10th	Night	18% 7% 32% 36% 7% 1	380
	11th to 20th	Night	19% 6% 29% 31% 14% 1	380
	21st to end	Night	21% 7% 24% 33% 14% 1	380
July	1st to 10th	Night	11% 5% 32% 38% 14% 1	370
	11th to 20th	Night	14% 5% 22% 41% 17% 1	368
	21st to end	Night	10% 4 27% 41% 18% 1	416
August	1st to 10th	Night	15% 5% 23% 34% 21% 1	490
	11th to 20th	Night	13% 4 20% 39% 23% 2	564
	21st to end	Night	16% 7% 26% 31% 17% 2	755
September	1st to 10th	Night	16% 6% 30% 30% 17% 2	760
	11th to 20th	Night	20% 5% 23% 27% 22% 3	760
	21st to end	Night	23% 9% 21% 29% 16% 1	760
October	1st to 10th	Night	24% 9% 29% 24% 12% 1	760
	11th to 20th	Night	30% 13% 28% 21% 8% 1	760
	21st to end	Night	32% 12% 27% 24% 4	836
November	1st to 10th	Night	28% 13% 27% 25% 6% 1	780
	11th to 20th	Night	27% 16% 32% 17% 8%	800
	21st to end	Night	35% 15% 24% 22% 5%	800
December	1st to 10th	Night	33% 16% 29% 17% 5%	800
	11th to 20th	Night	30% 14% 30% 22% 4 1	800
	21st to end	Night	34% 14% 27% 22% 3	880

Page generated at 2025-04-08 09:17:29. Version ac07

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