Rutland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rutland clear sky chart from 2005-11-06 to 2024-03-23.

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	18% 11% 4 7% 6% 3 5% 4 5% 6% 31%	78537
	Night	18% 12% 5% 8% 6% 3 4 4 5% 5% 30%	81348
Transparency	Day	54% 7% 10% 18% 10% 1	78242
	Night	56% 6% 11% 17% 9% 1	81177
Seeing	Day	27% 21% 28% 16% 6% 2	13907
	Night	25% 19% 25% 22% 8% 1	23053

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	15% 17% 7% 9% 6% 3 5% 4 4 4 25%	2517
	11th to 20th	Day	14% 15% 6% 14% 11% 4 4 4 3 4 21%	2520
	21st to end	Day	17% 19% 8% 10% 7% 3 5% 4 3 5% 19%	2772
February	1st to 10th	Day	14% 15% 5% 10% 7% 4 6% 5% 4 6% 23%	1691
	11th to 20th	Day	12% 15% 6% 13% 8% 4 4 5% 4 5% 23%	1844
	21st to end	Day	17% 12% 7% 11% 7% 4 3 4 4 6% 26%	1570
March	1st to 10th	Day	16% 12% 7% 10% 6% 4 5% 5% 4 5% 27%	1897
	11th to 20th	Day	17% 15% 7% 8% 5% 2 4 4 4 5% 29%	1952
	21st to end	Day	18% 12% 5% 8% 6% 4 4 3 4 5% 33%	2400
April	1st to 10th	Day	21% 14% 4 7% 4 3 3 3 5% 6% 31%	2160
	11th to 20th	Day	18% 11% 4 5% 6% 3 4 4 5% 6% 34%	2134
	21st to end	Day	24% 12% 4 7% 5% 3 3 3 5% 6% 29%	2299
May	1st to 10th	Day	24% 10% 3 6% 5% 2 4 3 5% 5% 30%	2364
	11th to 20th	Day	19% 8% 3 5% 4 3 5% 5% 5% 6% 37%	2478
	21st to end	Day	16% 7% 3 6% 5% 3 5% 5% 5% 8% 36%	2725
June	1st to 10th	Day	22% 7% 3 7% 6% 4 7% 5% 5% 7% 27%	2520
	11th to 20th	Day	21% 6% 3 5% 5% 3 6% 5% 6% 8% 32%	2520
	21st to end	Day	21% 9% 4 6% 6% 4 5% 5% 6% 7% 28%	2520
July	1st to 10th	Day	17% 6% 2 5% 5% 2 6% 6% 6% 8% 37%	2520
	11th to 20th	Day	14% 6% 3 6% 7% 4 5% 6% 7% 9% 33%	2520
	21st to end	Day	17% 5% 2 6% 6% 3 5% 6% 7% 9% 34%	2744
August	1st to 10th	Day	14% 7% 3 6% 6% 4 6% 6% 7% 8% 34%	2487
	11th to 20th	Day	16% 7% 2 5% 5% 4 5% 6% 6% 8% 34%	2206
	21st to end	Day	16% 6% 2 5% 5% 3 5% 5% 7% 9% 37%	2376
September	1st to 10th	Day	17% 6% 2 5% 4 2 5% 5% 6% 7% 41%	2160
	11th to 20th	Day	17% 6% 2 4 3 2 4 4 4 7% 47%	2048
	21st to end	Day	17% 7% 2 5% 4 4 4 5% 5% 8% 41%	1980
October	1st to 10th	Day	24% 9% 3 6% 5% 3 4 4 4 5% 31%	1922
	11th to 20th	Day	17% 10% 4 6% 6% 4 4 4 4 8% 33%	1757
	21st to end	Day	27% 13% 3 6% 5% 3 4 4 4 5% 26%	1782
November	1st to 10th	Day	16% 11% 4 6% 5% 2 5% 5% 5% 6% 36%	1671
	11th to 20th	Day	18% 13% 5% 7% 5% 3 4 4 5% 6% 30%	1710
	21st to end	Day	18% 12% 6% 8% 5% 4 4 5% 4 6% 27%	1573
December	1st to 10th	Day	20% 18% 5% 10% 6% 2 4 4 5% 6% 20%	1520
	11th to 20th	Day	20% 15% 7% 8% 6% 3 5% 3 4 5% 25%	1906
	21st to end	Day	22% 18% 6% 10% 6% 3 4 3 3 4 20%	2772
January	1st to 10th	Night	15% 16% 7% 12% 7% 3 4 3 4 4 26%	4429
	11th to 20th	Night	12% 18% 7% 15% 11% 4 5% 4 4 4 16%	4440
	21st to end	Night	21% 17% 7% 12% 7% 4 4 3 3 3 19%	4884
February	1st to 10th	Night	15% 14% 7% 12% 9% 4 5% 4 5% 5% 20%	2487
	11th to 20th	Night	12% 12% 6% 11% 9% 5% 6% 6% 6% 4 23%	2220
	21st to end	Night	14% 14% 5% 11% 7% 4 4 4 4 5% 29%	1884
March	1st to 10th	Night	16% 13% 6% 9% 8% 4 4 3 5% 4 28%	2270
	11th to 20th	Night	16% 15% 5% 8% 6% 3 5% 4 4 5% 29%	2223
	21st to end	Night	19% 13% 4 6% 5% 3 4 3 4 4 35%	2001
April	1st to 10th	Night	21% 12% 5% 7% 5% 2 4 4 5% 6% 29%	1800
	11th to 20th	Night	20% 12% 4 6% 5% 3 4 4 4 6% 32%	1775
	21st to end	Night	21% 12% 6% 6% 5% 2 4 3 6% 5% 31%	1661
May	1st to 10th	Night	24% 11% 3 6% 5% 3 4 4 5% 5% 29%	1612
	11th to 20th	Night	19% 8% 3 6% 5% 3 3 5% 5% 7% 35%	1415
	21st to end	Night	17% 8% 3 4 5% 3 5% 5% 6% 7% 37%	1550
June	1st to 10th	Night	22% 7% 2 5% 7% 3 5% 6% 5% 7% 32%	1440
	11th to 20th	Night	22% 7% 2 5% 4 3 4 4 5% 6% 37%	1440
	21st to end	Night	19% 7% 3 5% 5% 3 6% 4 6% 7% 35%	1440
July	1st to 10th	Night	17% 5% 2 5% 5% 3 7% 6% 6% 8% 37%	1440
	11th to 20th	Night	15% 5% 2 4 5% 3 5% 6% 7% 8% 39%	1440
	21st to end	Night	13% 6% 2 6% 5% 3 5% 5% 6% 7% 42%	1574
August	1st to 10th	Night	15% 6% 2 5% 6% 3 4 4 6% 8% 43%	1432
	11th to 20th	Night	15% 6% 3 7% 5% 2 4 5% 6% 9% 38%	1692
	21st to end	Night	16% 6% 2 4 4 2 4 4 5% 9% 42%	1980
September	1st to 10th	Night	17% 7% 2 4 4 3 4 5% 4 7% 44%	1800
	11th to 20th	Night	17% 5% 2 4 3 2 3 4 4 5% 51%	1912
	21st to end	Night	18% 6% 2 4 4 3 4 4 4 6% 45%	1980
October	1st to 10th	Night	24% 8% 3 6% 4 3 3 4 4 6% 33%	2036
	11th to 20th	Night	18% 10% 4 7% 6% 4 4 5% 5% 6% 32%	2202
	21st to end	Night	24% 13% 4 6% 6% 3 5% 4 5% 5% 25%	2574
November	1st to 10th	Night	18% 12% 5% 7% 6% 3 4 4 5% 4 33%	2407
	11th to 20th	Night	18% 13% 5% 6% 4 2 5% 4 5% 6% 31%	2470
	21st to end	Night	17% 13% 5% 9% 6% 3 4 4 4 6% 28%	2606
December	1st to 10th	Night	20% 19% 8% 10% 6% 3 4 4 4 4 18%	2660
	11th to 20th	Night	20% 15% 5% 8% 5% 3 4 4 5% 6% 24%	3288
	21st to end	Night	24% 17% 7% 11% 6% 3 3 3 4 4 19%	4884

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	62% 5% 9% 19% 5%	2518
	11th to 20th	Day	67% 7% 8% 13% 4 1	2520
	21st to end	Day	68% 6% 9% 11% 5% 1	2772
February	1st to 10th	Day	61% 7% 10% 14% 7% 1	1691
	11th to 20th	Day	62% 6% 8% 15% 8% 1	1853
	21st to end	Day	62% 4 10% 13% 10% 1	1570
March	1st to 10th	Day	59% 7% 10% 13% 9% 2	1900
	11th to 20th	Day	58% 5% 10% 13% 13% 2	1952
	21st to end	Day	56% 5% 7% 16% 13% 3	2400
April	1st to 10th	Day	56% 4 8% 19% 10% 2	2160
	11th to 20th	Day	51% 6% 9% 19% 13% 1	2134
	21st to end	Day	57% 6% 8% 16% 11% 2	2299
May	1st to 10th	Day	57% 5% 7% 17% 12% 2	2364
	11th to 20th	Day	49% 6% 9% 21% 14% 2	2482
	21st to end	Day	47% 8% 13% 22% 10% 1	2725
June	1st to 10th	Day	55% 8% 13% 16% 8%	2520
	11th to 20th	Day	49% 7% 11% 20% 12% 1	2520
	21st to end	Day	55% 8% 10% 17% 9% 1	2520
July	1st to 10th	Day	43% 8% 12% 23% 13%	2450
	11th to 20th	Day	44% 9% 14% 24% 7%	2445
	21st to end	Day	44% 9% 14% 24% 9%	2591
August	1st to 10th	Day	46% 10% 13% 21% 9%	2473
	11th to 20th	Day	46% 9% 15% 22% 8%	2206
	21st to end	Day	42% 8% 12% 25% 11% 1	2376
September	1st to 10th	Day	41% 7% 12% 27% 12%	2160
	11th to 20th	Day	38% 6% 9% 29% 17% 1	2048
	21st to end	Day	42% 7% 12% 25% 12% 2	1980
October	1st to 10th	Day	55% 5% 9% 18% 12% 1	1922
	11th to 20th	Day	49% 7% 14% 22% 7% 1	1757
	21st to end	Day	61% 5% 10% 14% 8% 1	1782
November	1st to 10th	Day	49% 7% 12% 20% 12%	1671
	11th to 20th	Day	55% 6% 10% 15% 12% 2	1710
	21st to end	Day	59% 6% 14% 15% 5% 1	1573
December	1st to 10th	Day	65% 8% 11% 10% 5% 1	1520
	11th to 20th	Day	63% 4 9% 15% 7% 1	1906
	21st to end	Day	68% 6% 7% 12% 7%	2772
January	1st to 10th	Night	61% 5% 12% 14% 6%	4429
	11th to 20th	Night	69% 7% 9% 9% 5% 1	4440
	21st to end	Night	70% 5% 7% 11% 6% 1	4884
February	1st to 10th	Night	64% 6% 10% 12% 7% 1	2487
	11th to 20th	Night	61% 7% 8% 14% 10% 1	2222
	21st to end	Night	59% 4 12% 16% 7% 2	1884
March	1st to 10th	Night	59% 5% 9% 17% 8% 2	2280
	11th to 20th	Night	57% 6% 9% 15% 10% 2	2224
	21st to end	Night	53% 4 8% 16% 15% 3	2001
April	1st to 10th	Night	56% 5% 9% 18% 10% 1	1800
	11th to 20th	Night	53% 5% 9% 20% 12% 1	1775
	21st to end	Night	55% 6% 8% 17% 10% 3	1661
May	1st to 10th	Night	57% 5% 7% 15% 14% 2	1612
	11th to 20th	Night	50% 5% 11% 20% 12% 2	1416
	21st to end	Night	45% 9% 14% 21% 11% 1	1551
June	1st to 10th	Night	50% 8% 11% 18% 11% 1	1440
	11th to 20th	Night	48% 6% 13% 19% 11% 1	1440
	21st to end	Night	48% 7% 13% 23% 8%	1440
July	1st to 10th	Night	43% 10% 14% 21% 11% 1	1400
	11th to 20th	Night	40% 8% 17% 27% 8%	1392
	21st to end	Night	38% 8% 16% 26% 11% 1	1486
August	1st to 10th	Night	39% 7% 16% 26% 11%	1422
	11th to 20th	Night	42% 8% 16% 24% 10%	1692
	21st to end	Night	39% 7% 15% 26% 13%	1980
September	1st to 10th	Night	40% 7% 14% 28% 12%	1800
	11th to 20th	Night	36% 6% 11% 28% 18% 1	1912
	21st to end	Night	41% 6% 12% 25% 14% 2	1980
October	1st to 10th	Night	51% 8% 9% 21% 9% 2	2036
	11th to 20th	Night	51% 8% 12% 21% 8%	2202
	21st to end	Night	61% 6% 9% 15% 8% 1	2574
November	1st to 10th	Night	54% 6% 10% 17% 11% 2	2407
	11th to 20th	Night	54% 6% 10% 17% 10% 3	2470
	21st to end	Night	56% 6% 13% 17% 7%	2606
December	1st to 10th	Night	69% 6% 9% 12% 3	2660
	11th to 20th	Night	62% 6% 10% 11% 10%	3288
	21st to end	Night	68% 6% 8% 12% 6%	4884

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	34% 28% 24% 12% 2	180
	11th to 20th	Day	35% 23% 31% 9% 2 1	180
	21st to end	Day	22% 30% 35% 10% 3	198
February	1st to 10th	Day	34% 41% 20% 4 1	261
	11th to 20th	Day	31% 31% 26% 10% 2	452
	21st to end	Day	35% 26% 25% 11% 2	382
March	1st to 10th	Day	33% 24% 29% 11% 2	460
	11th to 20th	Day	32% 25% 27% 12% 3 1	460
	21st to end	Day	32% 26% 22% 11% 6% 2	470
April	1st to 10th	Day	39% 18% 25% 12% 5% 1	420
	11th to 20th	Day	35% 25% 20% 13% 5% 2	412
	21st to end	Day	36% 22% 25% 10% 4 2	420
May	1st to 10th	Day	35% 23% 23% 12% 5% 2	423
	11th to 20th	Day	23% 21% 35% 15% 4 2	447
	21st to end	Day	20% 19% 35% 19% 6% 2	485
June	1st to 10th	Day	26% 21% 32% 15% 5% 1	450
	11th to 20th	Day	26% 14% 32% 18% 8%	450
	21st to end	Day	25% 17% 32% 20% 5% 1	450
July	1st to 10th	Day	22% 14% 29% 22% 9% 3	445
	11th to 20th	Day	15% 12% 40% 24% 8% 1	444
	21st to end	Day	16% 13% 40% 23% 6% 2	488
August	1st to 10th	Day	16% 14% 30% 25% 12% 3	446
	11th to 20th	Day	19% 14% 28% 22% 11% 6%	439
	21st to end	Day	19% 15% 27% 23% 12% 5%	495
September	1st to 10th	Day	18% 15% 28% 22% 12% 6%	450
	11th to 20th	Day	20% 16% 23% 16% 17% 8%	450
	21st to end	Day	20% 16% 30% 18% 11% 6%	450
October	1st to 10th	Day	30% 14% 25% 18% 11% 2	450
	11th to 20th	Day	27% 18% 27% 20% 8%	428
	21st to end	Day	37% 20% 24% 15% 4	396
November	1st to 10th	Day	28% 22% 24% 17% 8% 1	365
	11th to 20th	Day	30% 27% 24% 12% 6% 1	370
	21st to end	Day	30% 27% 31% 9% 2 1	233
December	1st to 10th	Day	32% 34% 24% 8% 2 1	180
	11th to 20th	Day	39% 31% 22% 7% 2	180
	21st to end	Day	36% 27% 24% 9% 4 1	198
January	1st to 10th	Night	25% 29% 30% 14% 3	760
	11th to 20th	Night	30% 24% 26% 17% 2 1	760
	21st to end	Night	20% 27% 30% 19% 4	836
February	1st to 10th	Night	24% 28% 33% 13% 2	760
	11th to 20th	Night	23% 31% 27% 17% 2	743
	21st to end	Night	26% 26% 30% 16% 2	628
March	1st to 10th	Night	25% 25% 30% 17% 3	760
	11th to 20th	Night	30% 23% 26% 16% 5%	760
	21st to end	Night	29% 21% 25% 17% 7%	801
April	1st to 10th	Night	29% 21% 25% 20% 4	720
	11th to 20th	Night	28% 23% 24% 17% 8%	711
	21st to end	Night	31% 19% 24% 20% 6% 1	581
May	1st to 10th	Night	32% 15% 26% 19% 8%	532
	11th to 20th	Night	21% 17% 26% 29% 6% 1	354
	21st to end	Night	21% 11% 26% 31% 11% 1	389
June	1st to 10th	Night	24% 8% 29% 26% 12% 1	360
	11th to 20th	Night	26% 8% 20% 33% 13% 1	360
	21st to end	Night	21% 7% 26% 33% 12% 1	360
July	1st to 10th	Night	18% 5% 22% 39% 14% 2	350
	11th to 20th	Night	16% 3 24% 38% 18% 1	348
	21st to end	Night	15% 4 28% 35% 17% 1	394
August	1st to 10th	Night	18% 5% 16% 39% 21% 1	358
	11th to 20th	Night	19% 6% 21% 34% 16% 4	628
	21st to end	Night	20% 6% 20% 31% 21% 2	792
September	1st to 10th	Night	20% 9% 22% 30% 17% 2	720
	11th to 20th	Night	21% 9% 20% 26% 20% 5%	720
	21st to end	Night	22% 11% 23% 26% 16% 3	720
October	1st to 10th	Night	29% 13% 18% 24% 13% 3	720
	11th to 20th	Night	24% 16% 25% 23% 10% 1	720
	21st to end	Night	32% 20% 23% 18% 6%	792
November	1st to 10th	Night	26% 20% 27% 19% 8% 1	740
	11th to 20th	Night	26% 23% 25% 18% 7% 1	760
	21st to end	Night	28% 27% 23% 16% 5% 1	760
December	1st to 10th	Night	33% 26% 23% 14% 3	760
	11th to 20th	Night	29% 28% 22% 17% 4	760
	21st to end	Night	31% 26% 27% 14% 2	836

Page generated at 2024-03-19 23:31:07. Version ac07

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