Modine Benstead Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Modine Benstead Observatory clear sky chart from 2005-11-06 to 2026-04-02.

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	12% 9% 3 8% 5% 4 5% 4 6% 8% 37%	131247
	Night	13% 9% 4 8% 5% 4 4 3 5% 6% 38%	130860
Transparency	Day	43% 7% 12% 24% 13% 1	134759
	Night	45% 6% 11% 23% 14% 2	135423
Seeing	Day	15% 10% 30% 27% 14% 4	17710
	Night	17% 9% 31% 29% 13% 1	27719

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	11% 13% 5% 13% 6% 5% 5% 4 6% 6% 26%	4691
	11th to 20th	Day	7% 10% 6% 12% 5% 4 5% 5% 6% 7% 33%	4710
	21st to end	Day	10% 13% 7% 10% 5% 4 5% 3 5% 5% 34%	5198
February	1st to 10th	Day	11% 14% 6% 11% 5% 4 4 5% 5% 7% 29%	1911
	11th to 20th	Day	12% 11% 4 8% 5% 4 5% 4 5% 5% 36%	2048
	21st to end	Day	11% 13% 5% 11% 5% 4 4 4 5% 7% 29%	1730
March	1st to 10th	Day	14% 9% 3 7% 4 4 4 3 4 6% 42%	4580
	11th to 20th	Day	11% 7% 2 8% 5% 5% 5% 4 6% 7% 41%	4785
	21st to end	Day	19% 12% 5% 11% 6% 4 5% 4 5% 5% 25%	6099
April	1st to 10th	Day	17% 13% 4 8% 5% 5% 4 4 5% 6% 29%	2412
	11th to 20th	Day	15% 9% 3 7% 5% 5% 5% 4 6% 6% 34%	2374
	21st to end	Day	17% 9% 3 7% 5% 4 5% 3 6% 6% 34%	2533
May	1st to 10th	Day	14% 9% 3 8% 4 4 5% 3 6% 7% 37%	5862
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 4 6% 8% 40%	6263
	21st to end	Day	15% 6% 2 5% 4 4 4 4 7% 8% 40%	6935
June	1st to 10th	Day	10% 5% 2 6% 5% 5% 4 4 6% 9% 46%	2800
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 6% 10% 44%	2800
	21st to end	Day	10% 6% 2 5% 5% 5% 5% 4 7% 9% 41%	2800
July	1st to 10th	Day	10% 7% 2 7% 5% 5% 5% 4 7% 10% 38%	6360
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 7% 10% 44%	6360
	21st to end	Day	8% 6% 3 7% 4 5% 5% 5% 6% 9% 43%	6924
August	1st to 10th	Day	10% 6% 2 6% 4 4 5% 5% 7% 9% 42%	4507
	11th to 20th	Day	10% 4 2 6% 5% 4 5% 4 7% 8% 45%	3922
	21st to end	Day	7% 5% 3 7% 5% 5% 4 4 6% 8% 47%	4312
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 7% 9% 45%	2400
	11th to 20th	Day	11% 4 2 5% 3 4 4 3 6% 8% 51%	2273
	21st to end	Day	11% 5% 2 7% 5% 4 4 4 6% 9% 43%	2200
October	1st to 10th	Day	12% 7% 2 5% 4 3 4 3 5% 7% 47%	2140
	11th to 20th	Day	17% 8% 3 8% 5% 5% 5% 3 5% 7% 33%	1969
	21st to end	Day	16% 9% 3 9% 4 4 4 4 4 6% 37%	1980
November	1st to 10th	Day	12% 9% 3 7% 4 4 4 3 4 8% 42%	1852
	11th to 20th	Day	13% 10% 4 10% 5% 5% 4 4 5% 8% 31%	1890
	21st to end	Day	18% 11% 3 8% 4 3 4 3 4 6% 35%	1779
December	1st to 10th	Day	8% 8% 3 8% 6% 5% 5% 4 7% 7% 39%	2690
	11th to 20th	Day	12% 14% 5% 11% 5% 5% 5% 4 6% 7% 27%	3088
	21st to end	Day	21% 20% 8% 13% 6% 4 3 3 4 4 15%	4070
January	1st to 10th	Night	11% 12% 7% 12% 5% 4 4 3 4 4 33%	8232
	11th to 20th	Night	10% 13% 6% 14% 7% 6% 6% 5% 6% 5% 23%	8280
	21st to end	Night	11% 13% 6% 9% 5% 5% 4 4 5% 6% 33%	9000
February	1st to 10th	Night	12% 14% 5% 9% 6% 5% 4 3 4 5% 33%	2708
	11th to 20th	Night	13% 10% 3 8% 4 4 4 3 6% 6% 39%	2458
	21st to end	Night	18% 11% 3 8% 4 4 4 3 5% 5% 36%	2076
March	1st to 10th	Night	15% 10% 2 8% 4 4 3 3 4 6% 42%	5493
	11th to 20th	Night	10% 7% 2 5% 4 4 4 3 5% 9% 46%	5436
	21st to end	Night	18% 11% 5% 11% 6% 5% 4 3 4 5% 29%	5072
April	1st to 10th	Night	16% 8% 3 6% 5% 5% 5% 4 6% 5% 37%	2010
	11th to 20th	Night	18% 10% 3 7% 4 4 4 3 5% 5% 37%	1975
	21st to end	Night	17% 8% 2 7% 5% 4 3 4 5% 7% 38%	1865
May	1st to 10th	Night	17% 8% 3 6% 4 4 5% 3 5% 7% 37%	4033
	11th to 20th	Night	12% 6% 3 7% 4 4 5% 4 5% 7% 42%	3645
	21st to end	Night	15% 8% 3 7% 4 4 4 3 5% 6% 41%	3942
June	1st to 10th	Night	9% 4 2 6% 4 4 6% 3 7% 7% 48%	1600
	11th to 20th	Night	10% 7% 2 6% 5% 4 5% 3 6% 10% 43%	1600
	21st to end	Night	9% 5% 2 7% 5% 5% 4 3 7% 8% 44%	1600
July	1st to 10th	Night	10% 5% 2 8% 5% 4 5% 4 7% 7% 42%	3618
	11th to 20th	Night	6% 5% 2 5% 4 3 4 4 7% 8% 51%	3617
	21st to end	Night	7% 5% 3 5% 4 4 4 4 7% 8% 49%	3947
August	1st to 10th	Night	9% 4 2 5% 3 4 4 4 6% 9% 51%	2648
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 6% 9% 49%	3123
	21st to end	Night	7% 4 2 5% 3 4 4 3 6% 10% 52%	3586
September	1st to 10th	Night	8% 5% 2 7% 4 3 4 3 5% 7% 53%	2000
	11th to 20th	Night	9% 4 1 5% 3 3 4 3 6% 7% 54%	2106
	21st to end	Night	12% 6% 2 6% 4 5% 4 4 4 6% 47%	2200
October	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 4 5% 52%	2255
	11th to 20th	Night	16% 8% 2 6% 4 3 5% 3 5% 6% 42%	2430
	21st to end	Night	18% 8% 3 6% 4 4 3 4 6% 7% 37%	2860
November	1st to 10th	Night	12% 9% 3 6% 4 4 3 3 5% 6% 46%	2666
	11th to 20th	Night	13% 10% 3 8% 5% 4 4 4 5% 6% 36%	2730
	21st to end	Night	16% 10% 3 8% 5% 4 4 3 5% 5% 36%	2840
December	1st to 10th	Night	10% 10% 3 8% 5% 5% 5% 4 4 7% 41%	4720
	11th to 20th	Night	15% 15% 4 10% 6% 5% 4 4 5% 5% 28%	5339
	21st to end	Night	21% 18% 6% 10% 5% 4 4 3 5% 5% 19%	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	57% 6% 14% 15% 7%	4692
	11th to 20th	Day	49% 5% 9% 19% 15% 2	4710
	21st to end	Day	52% 4 9% 23% 12%	5198
February	1st to 10th	Day	53% 6% 14% 17% 9% 1	1911
	11th to 20th	Day	48% 6% 11% 24% 10% 2	2058
	21st to end	Day	53% 7% 10% 18% 10% 2	1730
March	1st to 10th	Day	43% 6% 11% 24% 12% 5%	4580
	11th to 20th	Day	41% 6% 14% 26% 12% 1	4785
	21st to end	Day	59% 8% 11% 12% 9% 1	6101
April	1st to 10th	Day	54% 7% 10% 18% 10%	2412
	11th to 20th	Day	47% 7% 11% 20% 12% 3	2374
	21st to end	Day	48% 7% 14% 17% 12% 1	2533
May	1st to 10th	Day	43% 8% 11% 22% 14% 1	5897
	11th to 20th	Day	39% 9% 13% 24% 14%	6267
	21st to end	Day	38% 8% 12% 26% 13% 2	6949
June	1st to 10th	Day	34% 7% 15% 25% 17% 2	2800
	11th to 20th	Day	35% 8% 14% 22% 19% 2	2800
	21st to end	Day	37% 9% 15% 21% 16% 2	2800
July	1st to 10th	Day	39% 7% 12% 28% 12% 2	6291
	11th to 20th	Day	33% 7% 15% 31% 14% 1	6285
	21st to end	Day	36% 8% 15% 23% 17% 2	6728
August	1st to 10th	Day	35% 7% 15% 29% 12% 1	4492
	11th to 20th	Day	34% 8% 13% 33% 12% 1	3960
	21st to end	Day	33% 6% 14% 25% 21% 1	4311
September	1st to 10th	Day	35% 7% 13% 27% 16% 2	2400
	11th to 20th	Day	30% 6% 14% 32% 17% 2	2273
	21st to end	Day	36% 8% 12% 29% 14% 1	2200
October	1st to 10th	Day	24% 4 7% 42% 22% 1	3491
	11th to 20th	Day	36% 5% 9% 29% 20% 1	3185
	21st to end	Day	42% 4 8% 29% 13% 3	3180
November	1st to 10th	Day	41% 6% 13% 24% 15% 1	1852
	11th to 20th	Day	51% 6% 13% 21% 8% 1	1890
	21st to end	Day	51% 5% 12% 25% 7%	1779
December	1st to 10th	Day	43% 6% 20% 23% 7% 1	2690
	11th to 20th	Day	54% 7% 12% 18% 8% 1	3085
	21st to end	Day	73% 4 6% 11% 6%	4070
January	1st to 10th	Night	53% 5% 9% 22% 10%	8233
	11th to 20th	Night	60% 5% 8% 11% 14% 1	8280
	21st to end	Night	52% 4 12% 21% 10%	9000
February	1st to 10th	Night	53% 6% 11% 17% 11% 1	2708
	11th to 20th	Night	44% 6% 12% 22% 13% 1	2459
	21st to end	Night	49% 5% 11% 21% 10% 3	2076
March	1st to 10th	Night	44% 5% 12% 24% 12% 3	5493
	11th to 20th	Night	34% 6% 12% 31% 13% 4	5436
	21st to end	Night	58% 6% 8% 16% 11% 1	5072
April	1st to 10th	Night	45% 8% 10% 21% 14% 1	2010
	11th to 20th	Night	48% 5% 7% 19% 17% 4	1975
	21st to end	Night	44% 5% 14% 20% 15% 2	1865
May	1st to 10th	Night	44% 7% 13% 17% 16% 2	4060
	11th to 20th	Night	39% 9% 13% 21% 14% 3	3646
	21st to end	Night	43% 6% 10% 22% 14% 5%	3950
June	1st to 10th	Night	32% 9% 12% 28% 18% 2	1600
	11th to 20th	Night	35% 7% 12% 23% 20% 3	1600
	21st to end	Night	36% 8% 14% 24% 16% 2	1600
July	1st to 10th	Night	38% 7% 12% 29% 11% 3	3580
	11th to 20th	Night	29% 6% 14% 32% 18% 2	3572
	21st to end	Night	31% 7% 14% 24% 22% 2	3832
August	1st to 10th	Night	30% 7% 15% 28% 19% 1	2639
	11th to 20th	Night	31% 7% 12% 34% 15% 1	3151
	21st to end	Night	28% 6% 12% 29% 21% 3	3586
September	1st to 10th	Night	31% 7% 11% 27% 22% 3	2000
	11th to 20th	Night	29% 6% 10% 33% 20% 2	2106
	21st to end	Night	37% 6% 9% 30% 17% 1	2200
October	1st to 10th	Night	24% 4 7% 39% 25% 1	3684
	11th to 20th	Night	36% 6% 10% 24% 23% 2	3953
	21st to end	Night	41% 5% 9% 26% 17% 2	4610
November	1st to 10th	Night	39% 6% 10% 25% 17% 3	2666
	11th to 20th	Night	48% 6% 13% 21% 11% 2	2730
	21st to end	Night	49% 6% 13% 23% 9% 1	2840
December	1st to 10th	Night	43% 5% 16% 26% 8% 3	4720
	11th to 20th	Night	57% 7% 10% 15% 10% 1	5341
	21st to end	Night	67% 5% 9% 13% 6%	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	17% 15% 37% 25% 6%	330
	11th to 20th	Day	18% 20% 38% 20% 4 1	330
	21st to end	Day	20% 15% 39% 19% 6% 1	363
February	1st to 10th	Day	15% 18% 43% 19% 6%	330
	11th to 20th	Day	17% 25% 35% 18% 5%	330
	21st to end	Day	21% 17% 46% 14% 2	273
March	1st to 10th	Day	17% 20% 43% 17% 2	330
	11th to 20th	Day	23% 16% 36% 20% 5% 1	360
	21st to end	Day	25% 13% 33% 21% 6% 2	594
April	1st to 10th	Day	22% 14% 35% 24% 5%	504
	11th to 20th	Day	19% 17% 32% 20% 10% 2	492
	21st to end	Day	20% 12% 33% 23% 11% 2	500
May	1st to 10th	Day	19% 11% 32% 27% 10% 2	503
	11th to 20th	Day	20% 7% 30% 29% 11% 3	695
	21st to end	Day	15% 7% 31% 26% 16% 6%	789
June	1st to 10th	Day	9% 7% 29% 34% 17% 4	730
	11th to 20th	Day	12% 5% 28% 35% 15% 5%	730
	21st to end	Day	10% 6% 30% 35% 15% 4	730
July	1st to 10th	Day	7% 3 19% 36% 24% 10%	721
	11th to 20th	Day	8% 4 25% 35% 20% 8%	718
	21st to end	Day	8% 2 23% 40% 22% 6%	794
August	1st to 10th	Day	6% 4 19% 37% 24% 10%	696
	11th to 20th	Day	11% 4 19% 27% 27% 12%	519
	21st to end	Day	8% 4 19% 35% 26% 9%	583
September	1st to 10th	Day	12% 6% 21% 29% 24% 8%	530
	11th to 20th	Day	9% 2 16% 35% 25% 12%	530
	21st to end	Day	13% 8% 25% 28% 17% 8%	530
October	1st to 10th	Day	16% 9% 26% 28% 17% 5%	470
	11th to 20th	Day	20% 19% 29% 24% 8% 1	330
	21st to end	Day	23% 13% 35% 24% 5% 1	363
November	1st to 10th	Day	15% 17% 34% 24% 9% 1	330
	11th to 20th	Day	21% 17% 37% 18% 8%	330
	21st to end	Day	24% 11% 43% 19% 3	330
December	1st to 10th	Day	14% 18% 42% 19% 6% 1	330
	11th to 20th	Day	19% 17% 39% 20% 5%	330
	21st to end	Day	26% 19% 36% 16% 3 1	363
January	1st to 10th	Night	18% 15% 38% 23% 5%	1050
	11th to 20th	Night	20% 16% 37% 21% 6% 1	1050
	21st to end	Night	18% 12% 40% 26% 4	1155
February	1st to 10th	Night	18% 13% 39% 24% 6%	1028
	11th to 20th	Night	20% 14% 36% 25% 5%	823
	21st to end	Night	23% 11% 41% 20% 4	692
March	1st to 10th	Night	19% 11% 38% 25% 8%	840
	11th to 20th	Night	16% 12% 37% 27% 7% 1	825
	21st to end	Night	21% 9% 32% 29% 8% 1	693
April	1st to 10th	Night	19% 11% 35% 28% 7%	603
	11th to 20th	Night	22% 11% 30% 26% 9% 2	593
	21st to end	Night	21% 7% 30% 32% 10% 1	600
May	1st to 10th	Night	17% 8% 30% 34% 11% 1	600
	11th to 20th	Night	19% 5% 26% 32% 17% 1	591
	21st to end	Night	15% 4 23% 33% 22% 3	650
June	1st to 10th	Night	10% 3 21% 46% 18% 1	600
	11th to 20th	Night	14% 3 29% 35% 19% 1	600
	21st to end	Night	10% 4 24% 40% 22% 2	600
July	1st to 10th	Night	8% 2 16% 39% 31% 5%	585
	11th to 20th	Night	7% 3 17% 42% 25% 5%	582
	21st to end	Night	6% 2 15% 49% 27% 2	657
August	1st to 10th	Night	7% 3 13% 46% 28% 4	597
	11th to 20th	Night	8% 2 14% 37% 32% 6%	594
	21st to end	Night	8% 2 16% 39% 32% 3	660
September	1st to 10th	Night	10% 3 19% 36% 27% 6%	600
	11th to 20th	Night	9% 5% 17% 31% 31% 6%	706
	21st to end	Night	12% 8% 25% 28% 23% 5%	800
October	1st to 10th	Night	14% 6% 25% 33% 21% 2	800
	11th to 20th	Night	21% 9% 32% 26% 11% 1	800
	21st to end	Night	22% 10% 32% 26% 9% 1	880
November	1st to 10th	Night	17% 12% 36% 24% 11% 1	820
	11th to 20th	Night	19% 16% 37% 22% 6%	840
	21st to end	Night	21% 14% 35% 23% 6%	950
December	1st to 10th	Night	20% 15% 40% 21% 5%	1050
	11th to 20th	Night	22% 15% 36% 22% 5%	1050
	21st to end	Night	29% 12% 37% 19% 2	1155

Page generated at 2026-03-30 01:18:45. Version ac07

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