Belleplain State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Belleplain State Forest clear sky chart from 2005-11-06 to 2025-09-04.

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	14% 7% 2 6% 4 4 4 4 6% 8% 42%	126038
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	122663
Transparency	Day	39% 6% 13% 23% 16% 3	129592
	Night	40% 5% 12% 23% 17% 4	127194
Seeing	Day	18% 13% 29% 26% 11% 3	16177
	Night	18% 13% 29% 27% 12% 1	25418

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	13% 7% 2 4 3 3 4 3 4 5% 52%	3597
	11th to 20th	Day	13% 7% 3 8% 5% 4 3 2 4 4 45%	3690
	21st to end	Day	18% 9% 2 6% 4 4 4 3 4 5% 43%	4466
February	1st to 10th	Day	14% 8% 2 7% 4 4 4 4 6% 7% 40%	1803
	11th to 20th	Day	18% 8% 3 6% 3 4 4 3 5% 5% 41%	1948
	21st to end	Day	17% 10% 2 7% 4 4 4 2 5% 5% 40%	1650
March	1st to 10th	Day	20% 6% 2 4 3 3 3 2 4 6% 47%	4476
	11th to 20th	Day	11% 7% 2 5% 4 3 4 4 6% 7% 47%	4929
	21st to end	Day	16% 7% 2 6% 4 4 4 3 5% 6% 43%	5828
April	1st to 10th	Day	15% 8% 3 6% 3 4 4 3 5% 7% 43%	2400
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 5% 7% 46%	2374
	21st to end	Day	14% 6% 2 5% 4 3 4 4 7% 9% 41%	2400
May	1st to 10th	Day	21% 8% 3 6% 5% 4 4 4 6% 8% 31%	5704
	11th to 20th	Day	23% 9% 2 6% 4 3 4 3 5% 8% 33%	6259
	21st to end	Day	16% 7% 3 5% 4 4 5% 4 6% 9% 38%	6949
June	1st to 10th	Day	11% 6% 2 6% 4 4 4 5% 7% 9% 42%	2800
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 5% 7% 9% 41%	2800
	21st to end	Day	9% 5% 2 4 3 5% 5% 5% 8% 11% 44%	2800
July	1st to 10th	Day	8% 5% 2 5% 5% 5% 5% 5% 7% 12% 40%	6360
	11th to 20th	Day	12% 6% 2 7% 5% 5% 6% 6% 9% 12% 31%	6360
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 10% 38%	6794
August	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 6% 11% 36%	4149
	11th to 20th	Day	10% 5% 2 7% 4 5% 6% 4 7% 10% 39%	3850
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 8% 9% 45%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 6% 8% 45%	2316
	11th to 20th	Day	11% 5% 3 6% 4 4 3 3 6% 7% 48%	2230
	21st to end	Day	17% 8% 3 7% 4 4 5% 3 5% 7% 37%	2090
October	1st to 10th	Day	15% 7% 3 5% 3 4 4 2 5% 7% 45%	1938
	11th to 20th	Day	15% 5% 2 5% 3 3 3 2 4 6% 51%	1900
	21st to end	Day	14% 6% 2 6% 4 4 4 2 4 5% 48%	2019
November	1st to 10th	Day	13% 6% 2 4 3 4 4 3 5% 6% 52%	1761
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 6% 8% 48%	1800
	21st to end	Day	14% 5% 2 5% 4 4 4 3 4 7% 48%	1740
December	1st to 10th	Day	12% 6% 2 5% 3 3 5% 4 5% 7% 49%	2600
	11th to 20th	Day	20% 9% 2 5% 3 2 3 2 3 5% 44%	2986
	21st to end	Day	13% 7% 2 4 4 4 4 4 6% 8% 45%	3960
January	1st to 10th	Night	13% 7% 3 5% 3 3 3 3 4 6% 50%	6349
	11th to 20th	Night	14% 7% 2 6% 3 3 3 3 4 5% 51%	6177
	21st to end	Night	16% 7% 3 5% 4 3 4 3 4 6% 45%	6490
February	1st to 10th	Night	17% 6% 3 6% 4 4 4 3 5% 5% 42%	2595
	11th to 20th	Night	19% 7% 2 5% 4 4 3 4 5% 5% 42%	2338
	21st to end	Night	16% 7% 3 6% 4 4 3 3 5% 5% 43%	1980
March	1st to 10th	Night	17% 9% 2 5% 4 3 3 2 4 6% 46%	5364
	11th to 20th	Night	12% 12% 3 5% 3 3 4 3 4 5% 46%	5025
	21st to end	Night	15% 8% 3 6% 4 4 4 3 4 5% 44%	5102
April	1st to 10th	Night	17% 9% 3 6% 4 3 4 4 5% 6% 41%	2000
	11th to 20th	Night	13% 6% 2 7% 5% 4 4 3 5% 6% 44%	1975
	21st to end	Night	16% 6% 2 6% 4 4 5% 3 6% 7% 42%	2000
May	1st to 10th	Night	17% 9% 3 8% 5% 5% 4 4 7% 9% 29%	4223
	11th to 20th	Night	21% 10% 3 6% 5% 4 4 3 5% 7% 31%	3677
	21st to end	Night	20% 8% 3 6% 4 5% 4 3 5% 7% 35%	3926
June	1st to 10th	Night	14% 7% 3 7% 4 3 4 4 5% 8% 41%	1600
	11th to 20th	Night	11% 5% 2 6% 5% 5% 5% 4 6% 10% 41%	1600
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 41%	1600
July	1st to 10th	Night	9% 7% 3 7% 6% 6% 6% 5% 7% 9% 35%	3600
	11th to 20th	Night	12% 8% 3 9% 5% 5% 5% 4 7% 10% 31%	3600
	21st to end	Night	11% 7% 3 6% 5% 4 6% 5% 7% 9% 37%	4053
August	1st to 10th	Night	19% 8% 3 6% 5% 4 5% 4 5% 9% 32%	2966
	11th to 20th	Night	11% 6% 2 7% 4 4 5% 4 7% 8% 43%	3197
	21st to end	Night	9% 4 2 5% 4 3 4 4 5% 8% 52%	3586
September	1st to 10th	Night	13% 7% 3 6% 5% 4 4 3 5% 7% 44%	1931
	11th to 20th	Night	10% 6% 2 5% 3 3 3 4 5% 8% 51%	1949
	21st to end	Night	19% 8% 2 6% 3 4 4 3 4 7% 39%	2090
October	1st to 10th	Night	16% 7% 2 6% 4 4 3 3 5% 6% 44%	2237
	11th to 20th	Night	16% 5% 2 5% 2 2 3 2 5% 6% 52%	2280
	21st to end	Night	14% 7% 2 5% 3 3 4 3 4 6% 48%	2577
November	1st to 10th	Night	11% 6% 2 4 3 3 4 3 5% 6% 52%	2537
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 4 5% 49%	2600
	21st to end	Night	12% 5% 2 5% 4 4 4 4 5% 7% 48%	2655
December	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 5% 7% 50%	4580
	11th to 20th	Night	22% 6% 2 5% 3 3 4 3 5% 7% 40%	5208
	21st to end	Night	15% 8% 3 7% 4 4 4 4 5% 7% 41%	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	34% 2 8% 26% 26% 3	3598
	11th to 20th	Day	41% 4 9% 23% 17% 6%	3720
	21st to end	Day	43% 6% 9% 25% 13% 3	4466
February	1st to 10th	Day	42% 5% 14% 25% 13% 1	1803
	11th to 20th	Day	43% 4 10% 24% 15% 4	1957
	21st to end	Day	44% 5% 10% 21% 14% 5%	1650
March	1st to 10th	Day	38% 3 9% 24% 19% 7%	4479
	11th to 20th	Day	35% 6% 9% 27% 18% 5%	4929
	21st to end	Day	42% 5% 9% 17% 21% 7%	5828
April	1st to 10th	Day	40% 7% 12% 18% 18% 6%	2400
	11th to 20th	Day	36% 6% 13% 23% 18% 4	2374
	21st to end	Day	37% 7% 12% 20% 19% 4	2400
May	1st to 10th	Day	50% 7% 15% 17% 9% 1	5713
	11th to 20th	Day	48% 7% 11% 22% 10% 1	6263
	21st to end	Day	42% 7% 14% 22% 14% 1	6949
June	1st to 10th	Day	36% 10% 14% 23% 15% 2	2800
	11th to 20th	Day	35% 11% 14% 25% 13% 2	2800
	21st to end	Day	31% 10% 16% 24% 18% 1	2800
July	1st to 10th	Day	36% 10% 18% 21% 13% 1	6290
	11th to 20th	Day	42% 9% 20% 21% 6% 1	6285
	21st to end	Day	38% 8% 12% 25% 18% 1	6598
August	1st to 10th	Day	41% 6% 18% 25% 9%	4136
	11th to 20th	Day	38% 7% 14% 30% 10% 1	3886
	21st to end	Day	32% 7% 12% 30% 17% 2	4312
September	1st to 10th	Day	35% 8% 15% 22% 18% 3	2316
	11th to 20th	Day	34% 6% 10% 24% 22% 3	2230
	21st to end	Day	45% 7% 10% 17% 18% 2	2090
October	1st to 10th	Day	33% 4 9% 23% 25% 5%	3224
	11th to 20th	Day	25% 3 8% 27% 29% 9%	3140
	21st to end	Day	26% 3 12% 29% 23% 7%	3309
November	1st to 10th	Day	34% 4 13% 28% 17% 4	1761
	11th to 20th	Day	36% 4 11% 23% 23% 3	1800
	21st to end	Day	37% 5% 11% 29% 15% 2	1740
December	1st to 10th	Day	35% 4 20% 22% 16% 3	2600
	11th to 20th	Day	43% 3 12% 27% 12% 3	2986
	21st to end	Day	36% 6% 14% 23% 20% 1	3960
January	1st to 10th	Night	36% 3 8% 24% 24% 6%	6349
	11th to 20th	Night	37% 3 8% 25% 19% 7%	6222
	21st to end	Night	41% 3 10% 26% 17% 2	6490
February	1st to 10th	Night	43% 5% 13% 23% 14% 2	2595
	11th to 20th	Night	44% 4 9% 20% 19% 5%	2340
	21st to end	Night	42% 5% 9% 22% 17% 5%	1980
March	1st to 10th	Night	41% 4 9% 23% 14% 10%	5374
	11th to 20th	Night	40% 5% 10% 23% 16% 6%	5026
	21st to end	Night	43% 4 9% 16% 24% 5%	5102
April	1st to 10th	Night	44% 5% 10% 18% 18% 5%	2000
	11th to 20th	Night	41% 6% 9% 19% 21% 5%	1975
	21st to end	Night	41% 6% 9% 18% 20% 5%	2000
May	1st to 10th	Night	50% 6% 13% 19% 9% 2	4229
	11th to 20th	Night	54% 5% 9% 20% 11% 1	3678
	21st to end	Night	47% 6% 14% 19% 13% 2	3927
June	1st to 10th	Night	41% 6% 13% 20% 19% 1	1600
	11th to 20th	Night	38% 9% 12% 26% 14% 2	1600
	21st to end	Night	35% 9% 15% 25% 14% 3	1600
July	1st to 10th	Night	44% 9% 14% 20% 12% 1	3560
	11th to 20th	Night	47% 8% 18% 21% 5% 1	3552
	21st to end	Night	41% 6% 15% 21% 16% 1	3934
August	1st to 10th	Night	49% 7% 16% 19% 8%	2955
	11th to 20th	Night	36% 8% 14% 31% 11% 1	3227
	21st to end	Night	30% 6% 11% 28% 22% 2	3586
September	1st to 10th	Night	39% 7% 10% 22% 18% 4	1931
	11th to 20th	Night	31% 7% 12% 25% 22% 3	1949
	21st to end	Night	46% 5% 9% 20% 17% 2	2090
October	1st to 10th	Night	38% 4 10% 24% 21% 3	3731
	11th to 20th	Night	24% 3 12% 24% 29% 8%	3779
	21st to end	Night	24% 3 13% 29% 24% 6%	4237
November	1st to 10th	Night	33% 5% 11% 25% 20% 6%	2537
	11th to 20th	Night	39% 5% 10% 21% 21% 5%	2600
	21st to end	Night	35% 5% 12% 26% 19% 2	2655
December	1st to 10th	Night	34% 4 13% 26% 18% 3	4580
	11th to 20th	Night	44% 4 13% 20% 16% 3	5208
	21st to end	Night	42% 5% 14% 20% 17% 2	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% 28% 32% 15% 5% 1	200
	11th to 20th	Day	23% 30% 31% 14% 3	227
	21st to end	Day	23% 23% 32% 19% 3 1	330
February	1st to 10th	Day	25% 19% 39% 14% 3	303
	11th to 20th	Day	29% 24% 34% 12% 1	496
	21st to end	Day	24% 26% 32% 14% 4	414
March	1st to 10th	Day	21% 24% 34% 18% 3	500
	11th to 20th	Day	20% 23% 35% 17% 3 2	500
	21st to end	Day	21% 19% 38% 19% 2 1	550
April	1st to 10th	Day	22% 20% 37% 15% 5% 1	500
	11th to 20th	Day	17% 20% 34% 24% 5% 1	492
	21st to end	Day	20% 13% 38% 22% 5% 1	500
May	1st to 10th	Day	25% 14% 33% 22% 5% 2	503
	11th to 20th	Day	22% 10% 33% 26% 7% 1	527
	21st to end	Day	20% 6% 22% 33% 16% 3	573
June	1st to 10th	Day	14% 7% 31% 29% 16% 3	530
	11th to 20th	Day	14% 6% 28% 36% 13% 2	530
	21st to end	Day	12% 4 29% 38% 15% 3	530
July	1st to 10th	Day	11% 5% 22% 36% 20% 6%	525
	11th to 20th	Day	7% 3 19% 41% 24% 5%	524
	21st to end	Day	11% 4 23% 39% 21% 3	576
August	1st to 10th	Day	13% 5% 22% 35% 21% 4	526
	11th to 20th	Day	13% 3 17% 37% 24% 6%	519
	21st to end	Day	10% 5% 24% 33% 19% 9%	583
September	1st to 10th	Day	16% 6% 21% 30% 18% 9%	502
	11th to 20th	Day	13% 4 29% 29% 19% 6%	490
	21st to end	Day	22% 10% 26% 29% 11% 2	490
October	1st to 10th	Day	20% 8% 23% 29% 14% 6%	490
	11th to 20th	Day	17% 14% 24% 26% 16% 3	490
	21st to end	Day	17% 16% 30% 25% 11% 2	502
November	1st to 10th	Day	15% 15% 31% 24% 12% 3	395
	11th to 20th	Day	16% 21% 35% 22% 7%	400
	21st to end	Day	19% 21% 30% 21% 9% 1	340
December	1st to 10th	Day	24% 21% 34% 17% 5%	200
	11th to 20th	Day	25% 25% 31% 17% 4	200
	21st to end	Day	23% 18% 32% 19% 7%	220
January	1st to 10th	Night	21% 25% 33% 16% 5%	800
	11th to 20th	Night	23% 22% 29% 24% 3	800
	21st to end	Night	18% 23% 39% 19% 2	880
February	1st to 10th	Night	21% 18% 36% 22% 2	800
	11th to 20th	Night	26% 25% 33% 15% 1	783
	21st to end	Night	21% 22% 35% 20% 3	660
March	1st to 10th	Night	20% 21% 35% 21% 4	800
	11th to 20th	Night	22% 20% 32% 19% 6% 1	800
	21st to end	Night	21% 14% 38% 20% 5% 1	880
April	1st to 10th	Night	21% 20% 35% 20% 5%	800
	11th to 20th	Night	17% 15% 33% 28% 7%	791
	21st to end	Night	20% 10% 35% 29% 6% 1	800
May	1st to 10th	Night	19% 11% 32% 30% 7%	678
	11th to 20th	Night	19% 9% 31% 33% 8%	444
	21st to end	Night	18% 3 23% 34% 20% 2	433
June	1st to 10th	Night	17% 4 26% 39% 14% 1	400
	11th to 20th	Night	14% 3 25% 38% 19% 1	400
	21st to end	Night	8% 2 23% 48% 18% 2	400
July	1st to 10th	Night	10% 4 19% 44% 21% 2	390
	11th to 20th	Night	9% 2 14% 42% 30% 3	388
	21st to end	Night	9% 3 17% 46% 24% 2	490
August	1st to 10th	Night	13% 4 13% 42% 27% 2	622
	11th to 20th	Night	12% 3 19% 37% 26% 3	790
	21st to end	Night	12% 3 15% 39% 27% 4	880
September	1st to 10th	Night	17% 3 18% 34% 23% 4	773
	11th to 20th	Night	13% 3 21% 32% 26% 5%	760
	21st to end	Night	24% 6% 22% 28% 19% 1	760
October	1st to 10th	Night	20% 7% 22% 28% 19% 4	760
	11th to 20th	Night	18% 13% 24% 29% 16% 1	760
	21st to end	Night	19% 13% 32% 23% 12% 1	836
November	1st to 10th	Night	15% 14% 33% 25% 11% 2	780
	11th to 20th	Night	19% 18% 31% 25% 7% 1	800
	21st to end	Night	16% 20% 33% 22% 10% 1	800
December	1st to 10th	Night	23% 19% 32% 16% 8% 2	800
	11th to 20th	Night	19% 21% 37% 19% 5%	800
	21st to end	Night	19% 18% 34% 26% 3	880

Page generated at 2025-09-01 01:51:07. Version ac07

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