Bath Nature Preseve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bath Nature Preseve clear sky chart from 2005-11-06 to 2024-08-15.

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% 12% 4 8% 5% 4 4 4 5% 7% 30%	95005
	Night	16% 12% 4 9% 5% 4 4 3 5% 6% 31%	93608
Transparency	Day	53% 6% 11% 19% 11% 1	94777
	Night	54% 5% 11% 18% 11% 1	93439
Seeing	Day	22% 16% 28% 20% 11% 4	14292
	Night	22% 12% 27% 26% 12% 1	24163

By Month

Percentage Cloud Cover SE (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	18% 23% 9% 15% 5% 3 3 2 3 4 14%	2836
	11th to 20th	Day	15% 25% 7% 13% 6% 6% 4 3 4 4 13%	2840
	21st to end	Day	26% 21% 11% 12% 6% 4 4 3 3 3 8%	3124
February	1st to 10th	Day	17% 21% 5% 11% 8% 4 3 3 4 5% 20%	1710
	11th to 20th	Day	15% 14% 7% 14% 8% 4 5% 3 4 4 21%	1724
	21st to end	Day	18% 16% 4 12% 7% 4 4 3 5% 5% 23%	1570
March	1st to 10th	Day	22% 13% 7% 9% 5% 4 3 3 5% 6% 25%	3344
	11th to 20th	Day	12% 15% 5% 11% 5% 4 4 3 4 5% 33%	3480
	21st to end	Day	21% 12% 5% 9% 5% 4 4 3 5% 5% 28%	3815
April	1st to 10th	Day	15% 15% 4 7% 5% 4 4 3 5% 7% 30%	2120
	11th to 20th	Day	18% 12% 3 7% 5% 4 5% 3 5% 6% 33%	2417
	21st to end	Day	20% 11% 4 7% 5% 4 3 3 4 6% 32%	2470
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 4 4 5% 7% 29%	4082
	11th to 20th	Day	19% 8% 3 6% 4 4 4 4 5% 8% 33%	4081
	21st to end	Day	11% 6% 3 7% 5% 4 5% 4 7% 9% 39%	4476
June	1st to 10th	Day	14% 8% 2 7% 5% 5% 5% 4 7% 8% 36%	2660
	11th to 20th	Day	12% 7% 3 8% 5% 5% 5% 5% 6% 8% 37%	2660
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 10% 38%	2616
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 6% 9% 38%	4120
	11th to 20th	Day	9% 5% 2 5% 5% 5% 6% 4 7% 10% 42%	4120
	21st to end	Day	11% 6% 3 6% 6% 5% 6% 4 7% 7% 38%	4466
August	1st to 10th	Day	10% 6% 3 7% 5% 6% 6% 5% 7% 8% 37%	2457
	11th to 20th	Day	10% 7% 3 7% 5% 5% 6% 5% 8% 9% 35%	2357
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 6% 7% 9% 37%	2538
September	1st to 10th	Day	14% 6% 2 6% 4 5% 4 4 5% 8% 41%	2056
	11th to 20th	Day	12% 7% 2 6% 6% 5% 5% 3 5% 9% 41%	1980
	21st to end	Day	18% 8% 3 6% 3 4 4 3 4 6% 39%	1980
October	1st to 10th	Day	15% 8% 3 7% 4 4 4 4 6% 7% 38%	1865
	11th to 20th	Day	19% 10% 3 9% 4 4 4 4 5% 5% 33%	1800
	21st to end	Day	23% 11% 3 9% 4 5% 4 3 6% 5% 27%	1972
November	1st to 10th	Day	12% 11% 5% 8% 5% 4 4 3 5% 6% 37%	1672
	11th to 20th	Day	18% 16% 3 9% 6% 3 4 3 5% 6% 28%	1703
	21st to end	Day	19% 17% 6% 9% 5% 4 5% 4 5% 5% 19%	1520
December	1st to 10th	Day	17% 24% 7% 11% 6% 4 4 3 4 3 17%	1520
	11th to 20th	Day	19% 17% 8% 15% 5% 4 4 3 4 6% 15%	1910
	21st to end	Day	25% 25% 8% 11% 5% 4 3 3 3 4 10%	2944
January	1st to 10th	Night	16% 23% 10% 14% 5% 4 3 3 4 4 15%	4109
	11th to 20th	Night	16% 21% 9% 18% 6% 4 6% 4 3 3 10%	4120
	21st to end	Night	27% 20% 7% 14% 5% 3 3 2 2 3 13%	4532
February	1st to 10th	Night	20% 15% 6% 12% 7% 4 4 3 4 5% 20%	2470
	11th to 20th	Night	16% 15% 6% 12% 7% 6% 6% 4 4 4 22%	2339
	21st to end	Night	20% 15% 5% 12% 6% 4 4 3 4 5% 23%	1884
March	1st to 10th	Night	22% 15% 4 7% 3 3 3 2 4 5% 33%	3496
	11th to 20th	Night	15% 11% 3 8% 4 4 5% 4 5% 6% 34%	3480
	21st to end	Night	18% 11% 4 9% 4 4 4 4 5% 5% 33%	3817
April	1st to 10th	Night	16% 13% 3 7% 5% 5% 4 4 5% 7% 30%	2058
	11th to 20th	Night	16% 11% 3 7% 5% 4 6% 4 5% 6% 34%	1727
	21st to end	Night	15% 8% 3 7% 5% 5% 5% 4 6% 6% 36%	1710
May	1st to 10th	Night	24% 9% 3 8% 5% 4 4 4 5% 6% 28%	2813
	11th to 20th	Night	17% 9% 3 6% 4 4 4 3 5% 9% 38%	2812
	21st to end	Night	11% 5% 2 5% 3 3 4 4 7% 11% 45%	3062
June	1st to 10th	Night	9% 7% 2 6% 5% 5% 4 4 6% 8% 43%	1520
	11th to 20th	Night	9% 6% 2 6% 6% 5% 4 5% 8% 8% 41%	1520
	21st to end	Night	11% 5% 2 6% 4 4 6% 5% 6% 10% 41%	1557
July	1st to 10th	Night	10% 5% 2 7% 4 4 4 3 5% 8% 46%	2840
	11th to 20th	Night	9% 5% 1 5% 4 4 4 3 7% 9% 48%	2840
	21st to end	Night	7% 6% 2 7% 5% 5% 5% 4 6% 9% 45%	3087
August	1st to 10th	Night	7% 6% 2 6% 4 5% 5% 4 6% 9% 46%	1701
	11th to 20th	Night	9% 6% 2 6% 5% 5% 4 4 5% 9% 45%	1643
	21st to end	Night	9% 5% 2 5% 5% 4 5% 4 6% 8% 47%	1800
September	1st to 10th	Night	13% 5% 2 6% 4 4 5% 4 5% 7% 45%	1900
	11th to 20th	Night	10% 5% 2 4 4 4 4 3 4 8% 52%	1980
	21st to end	Night	15% 7% 2 8% 5% 4 3 3 5% 7% 41%	1980
October	1st to 10th	Night	14% 6% 2 6% 4 5% 5% 3 6% 7% 43%	2093
	11th to 20th	Night	20% 8% 3 8% 5% 5% 4 4 5% 5% 34%	2160
	21st to end	Night	23% 11% 3 7% 5% 4 4 4 5% 5% 29%	2380
November	1st to 10th	Night	15% 9% 3 7% 4 4 4 4 5% 6% 39%	2406
	11th to 20th	Night	16% 16% 4 9% 5% 4 4 3 5% 6% 28%	2474
	21st to end	Night	21% 16% 5% 7% 5% 4 5% 4 5% 5% 23%	2660
December	1st to 10th	Night	21% 19% 8% 10% 5% 5% 4 2 4 5% 19%	2660
	11th to 20th	Night	16% 19% 6% 12% 5% 4 4 3 4 5% 21%	3285
	21st to end	Night	26% 22% 7% 10% 5% 4 4 3 3 5% 11%	4693

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	76% 3 9% 10% 2	2837
	11th to 20th	Day	77% 3 9% 9% 3	2840
	21st to end	Day	84% 3 6% 5% 2	3124
February	1st to 10th	Day	68% 3 10% 13% 6% 1	1710
	11th to 20th	Day	68% 4 8% 14% 6% 1	1733
	21st to end	Day	63% 4 12% 13% 6% 1	1570
March	1st to 10th	Day	60% 5% 8% 21% 5%	3344
	11th to 20th	Day	54% 4 12% 22% 7% 1	3480
	21st to end	Day	57% 4 10% 17% 11% 1	3815
April	1st to 10th	Day	54% 5% 11% 18% 12% 1	2120
	11th to 20th	Day	52% 5% 11% 17% 13% 2	2417
	21st to end	Day	53% 5% 10% 20% 10% 2	2470
May	1st to 10th	Day	53% 6% 9% 21% 9% 1	4120
	11th to 20th	Day	49% 5% 12% 23% 10% 1	4085
	21st to end	Day	39% 8% 12% 20% 15% 5%	4489
June	1st to 10th	Day	44% 7% 10% 25% 14% 1	2660
	11th to 20th	Day	42% 7% 14% 22% 15% 1	2660
	21st to end	Day	39% 7% 13% 23% 16% 2	2616
July	1st to 10th	Day	41% 6% 11% 23% 16% 2	4055
	11th to 20th	Day	35% 7% 11% 26% 19% 1	4051
	21st to end	Day	41% 7% 13% 17% 19% 2	4324
August	1st to 10th	Day	41% 8% 12% 26% 12% 1	2444
	11th to 20th	Day	40% 9% 14% 24% 12% 2	2357
	21st to end	Day	39% 9% 12% 22% 14% 4	2538
September	1st to 10th	Day	41% 7% 14% 20% 16% 3	2056
	11th to 20th	Day	40% 7% 14% 24% 15% 1	1980
	21st to end	Day	46% 5% 9% 23% 16% 1	1980
October	1st to 10th	Day	44% 7% 11% 23% 14% 1	1865
	11th to 20th	Day	51% 5% 11% 21% 10% 1	1800
	21st to end	Day	59% 4 12% 15% 9% 1	1972
November	1st to 10th	Day	48% 4 11% 21% 14% 1	1672
	11th to 20th	Day	58% 4 9% 18% 8% 2	1703
	21st to end	Day	66% 5% 9% 14% 6%	1520
December	1st to 10th	Day	73% 3 9% 12% 3	1520
	11th to 20th	Day	71% 5% 8% 13% 3	1906
	21st to end	Day	80% 4 9% 6% 2	2944
January	1st to 10th	Night	74% 4 7% 11% 4	4109
	11th to 20th	Night	80% 3 7% 8% 1	4120
	21st to end	Night	78% 3 7% 9% 2	4532
February	1st to 10th	Night	67% 4 9% 14% 5%	2470
	11th to 20th	Night	64% 5% 9% 15% 7%	2341
	21st to end	Night	65% 3 10% 13% 9% 1	1884
March	1st to 10th	Night	55% 4 10% 22% 8%	3496
	11th to 20th	Night	49% 7% 15% 18% 10% 1	3480
	21st to end	Night	52% 4 8% 24% 10% 1	3817
April	1st to 10th	Night	53% 5% 10% 17% 13% 1	2058
	11th to 20th	Night	50% 5% 11% 17% 15% 3	1727
	21st to end	Night	47% 4 11% 20% 15% 3	1710
May	1st to 10th	Night	55% 6% 9% 20% 9% 2	2840
	11th to 20th	Night	44% 6% 13% 23% 12% 2	2813
	21st to end	Night	31% 8% 14% 26% 18% 3	3069
June	1st to 10th	Night	39% 7% 10% 26% 15% 2	1520
	11th to 20th	Night	38% 6% 15% 20% 18% 3	1520
	21st to end	Night	35% 8% 13% 25% 17% 2	1557
July	1st to 10th	Night	37% 5% 11% 24% 18% 5%	2795
	11th to 20th	Night	32% 6% 12% 29% 19% 1	2786
	21st to end	Night	36% 6% 13% 19% 24% 2	2988
August	1st to 10th	Night	33% 8% 13% 27% 19% 1	1690
	11th to 20th	Night	36% 6% 15% 28% 13% 2	1643
	21st to end	Night	35% 6% 13% 25% 18% 3	1800
September	1st to 10th	Night	37% 6% 12% 25% 16% 4	1900
	11th to 20th	Night	31% 5% 14% 26% 22% 1	1980
	21st to end	Night	42% 6% 11% 21% 19% 1	1980
October	1st to 10th	Night	39% 6% 13% 22% 19% 1	2093
	11th to 20th	Night	52% 4 10% 21% 13% 1	2160
	21st to end	Night	57% 4 10% 19% 9% 2	2380
November	1st to 10th	Night	45% 5% 12% 22% 14% 2	2406
	11th to 20th	Night	58% 3 9% 17% 10% 2	2474
	21st to end	Night	63% 4 11% 16% 6%	2660
December	1st to 10th	Night	69% 5% 9% 12% 5%	2660
	11th to 20th	Night	66% 5% 11% 15% 3	3288
	21st to end	Night	77% 4 10% 8% 2	4693

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	31% 23% 30% 10% 4 1	270
	11th to 20th	Day	30% 26% 32% 9% 3	270
	21st to end	Day	30% 31% 27% 9% 2	297
February	1st to 10th	Day	33% 23% 34% 9%	270
	11th to 20th	Day	29% 28% 35% 7% 1	270
	21st to end	Day	31% 32% 32% 5%	225
March	1st to 10th	Day	28% 22% 31% 15% 4	403
	11th to 20th	Day	28% 19% 33% 15% 5% 1	460
	21st to end	Day	32% 21% 26% 15% 5%	506
April	1st to 10th	Day	24% 24% 28% 16% 7% 1	460
	11th to 20th	Day	29% 19% 26% 13% 9% 3	452
	21st to end	Day	26% 19% 32% 16% 6% 2	460
May	1st to 10th	Day	26% 19% 29% 17% 8% 2	463
	11th to 20th	Day	22% 16% 30% 19% 8% 5%	487
	21st to end	Day	15% 12% 26% 26% 17% 5%	529
June	1st to 10th	Day	16% 11% 31% 29% 10% 3	490
	11th to 20th	Day	18% 10% 24% 31% 13% 4	490
	21st to end	Day	14% 12% 33% 25% 11% 5%	490
July	1st to 10th	Day	13% 6% 24% 28% 20% 9%	485
	11th to 20th	Day	12% 7% 26% 28% 20% 7%	484
	21st to end	Day	11% 7% 25% 30% 20% 7%	532
August	1st to 10th	Day	14% 8% 20% 28% 22% 8%	486
	11th to 20th	Day	16% 8% 23% 25% 18% 10%	456
	21st to end	Day	12% 6% 23% 28% 20% 11%	495
September	1st to 10th	Day	18% 7% 20% 28% 17% 10%	450
	11th to 20th	Day	13% 5% 18% 28% 26% 10%	450
	21st to end	Day	24% 10% 22% 22% 15% 6%	450
October	1st to 10th	Day	16% 10% 28% 24% 18% 4	450
	11th to 20th	Day	24% 18% 34% 16% 8%	450
	21st to end	Day	32% 17% 29% 18% 3 1	487
November	1st to 10th	Day	20% 24% 30% 15% 9% 2	270
	11th to 20th	Day	32% 23% 26% 14% 4 1	266
	21st to end	Day	27% 23% 41% 8% 1	180
December	1st to 10th	Day	27% 24% 33% 10% 3 2	180
	11th to 20th	Day	28% 28% 32% 9% 2	180
	21st to end	Day	33% 25% 30% 11% 1	249
January	1st to 10th	Night	29% 21% 32% 14% 4	760
	11th to 20th	Night	33% 20% 28% 15% 4	760
	21st to end	Night	28% 19% 29% 21% 3	836
February	1st to 10th	Night	29% 18% 31% 19% 3	760
	11th to 20th	Night	27% 19% 32% 19% 2	743
	21st to end	Night	29% 20% 35% 15% 2	628
March	1st to 10th	Night	24% 16% 34% 20% 5%	760
	11th to 20th	Night	23% 18% 31% 22% 6% 1	760
	21st to end	Night	25% 13% 31% 23% 7% 1	836
April	1st to 10th	Night	24% 15% 31% 24% 5% 1	760
	11th to 20th	Night	24% 13% 33% 20% 9% 1	603
	21st to end	Night	20% 11% 34% 29% 5% 1	570
May	1st to 10th	Night	20% 10% 29% 31% 9% 1	570
	11th to 20th	Night	18% 8% 26% 35% 10% 2	561
	21st to end	Night	13% 3 25% 37% 20% 2	612
June	1st to 10th	Night	11% 5% 33% 36% 15% 1	380
	11th to 20th	Night	12% 5% 27% 42% 13% 1	380
	21st to end	Night	11% 6% 27% 37% 18%	417
July	1st to 10th	Night	10% 3 15% 41% 28% 3	555
	11th to 20th	Night	9% 4 21% 38% 25% 3	552
	21st to end	Night	8% 5% 15% 43% 26% 2	624
August	1st to 10th	Night	10% 4 14% 42% 26% 3	567
	11th to 20th	Night	12% 2 14% 38% 31% 3	549
	21st to end	Night	11% 3 20% 32% 31% 4	612
September	1st to 10th	Night	14% 6% 17% 32% 27% 5%	720
	11th to 20th	Night	12% 3 17% 34% 30% 4	720
	21st to end	Night	17% 8% 23% 28% 19% 4	720
October	1st to 10th	Night	16% 9% 24% 30% 19% 2	720
	11th to 20th	Night	25% 12% 28% 26% 8% 1	720
	21st to end	Night	29% 14% 27% 24% 5%	792
November	1st to 10th	Night	20% 14% 30% 26% 10% 1	740
	11th to 20th	Night	28% 18% 28% 19% 6% 1	760
	21st to end	Night	31% 18% 29% 16% 6%	760
December	1st to 10th	Night	32% 18% 30% 16% 5%	760
	11th to 20th	Night	27% 20% 32% 17% 3	760
	21st to end	Night	31% 17% 31% 19% 2	836

Page generated at 2024-08-12 09:52:47. Version ac07

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