Southington Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Southington Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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	17% 6% 3 5% 5% 3 4 5% 5% 7% 40%	78298
	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 41%	80997
Transparency	Day	43% 6% 12% 22% 15% 2	78003
	Night	44% 6% 12% 22% 15% 2	80826
Seeing	Day	23% 17% 31% 19% 7% 2	14009
	Night	22% 15% 33% 24% 7% 1	23203

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% 7% 2 5% 5% 2 4 5% 5% 5% 45%	2517
	11th to 20th	Day	16% 8% 4 8% 5% 3 5% 5% 5% 5% 36%	2520
	21st to end	Day	22% 12% 3 6% 5% 3 4 4 5% 5% 33%	2840
February	1st to 10th	Day	17% 7% 3 6% 4 4 5% 5% 6% 6% 36%	1771
	11th to 20th	Day	13% 6% 3 6% 5% 4 6% 4 6% 7% 41%	1848
	21st to end	Day	22% 8% 3 5% 5% 3 4 4 4 5% 38%	1520
March	1st to 10th	Day	14% 7% 3 6% 5% 4 5% 4 5% 7% 41%	1797
	11th to 20th	Day	17% 6% 2 5% 5% 4 6% 5% 5% 7% 38%	1849
	21st to end	Day	19% 8% 4 6% 5% 3 3 3 4 5% 41%	2376
April	1st to 10th	Day	17% 8% 3 5% 5% 3 3 4 6% 7% 38%	2160
	11th to 20th	Day	18% 5% 2 5% 5% 2 4 5% 5% 7% 42%	2134
	21st to end	Day	22% 5% 2 5% 5% 3 4 4 5% 6% 39%	2262
May	1st to 10th	Day	24% 8% 2 5% 5% 2 4 4 6% 7% 33%	2340
	11th to 20th	Day	19% 6% 3 4 5% 2 4 4 5% 8% 39%	2408
	21st to end	Day	16% 5% 2 5% 5% 3 4 5% 5% 7% 43%	2725
June	1st to 10th	Day	17% 6% 2 5% 6% 4 5% 5% 7% 9% 34%	2520
	11th to 20th	Day	16% 6% 3 5% 5% 3 5% 6% 6% 9% 36%	2520
	21st to end	Day	14% 6% 2 6% 5% 3 5% 5% 7% 8% 39%	2520
July	1st to 10th	Day	13% 5% 3 5% 6% 4 5% 6% 5% 8% 40%	2520
	11th to 20th	Day	13% 4 2 5% 6% 3 5% 6% 6% 10% 40%	2520
	21st to end	Day	13% 5% 3 6% 6% 4 5% 6% 7% 8% 38%	2744
August	1st to 10th	Day	11% 6% 3 6% 6% 5% 5% 6% 7% 9% 37%	2422
	11th to 20th	Day	12% 5% 2 6% 5% 3 5% 5% 6% 8% 41%	2144
	21st to end	Day	13% 5% 3 5% 4 3 5% 5% 6% 9% 42%	2376
September	1st to 10th	Day	13% 6% 3 5% 5% 3 5% 5% 5% 6% 43%	2160
	11th to 20th	Day	13% 6% 2 4 3 3 4 4 5% 6% 50%	2035
	21st to end	Day	19% 4 2 5% 4 3 3 4 5% 6% 44%	1980
October	1st to 10th	Day	22% 7% 2 4 5% 2 3 4 4 5% 41%	1951
	11th to 20th	Day	15% 6% 2 5% 5% 2 3 4 6% 7% 45%	1782
	21st to end	Day	22% 6% 2 5% 4 4 4 4 4 6% 39%	1782
November	1st to 10th	Day	13% 6% 3 4 6% 3 4 4 4 5% 49%	1671
	11th to 20th	Day	20% 5% 1 4 4 2 5% 3 4 7% 46%	1710
	21st to end	Day	16% 7% 3 5% 4 2 4 4 5% 7% 43%	1676
December	1st to 10th	Day	18% 6% 4 5% 6% 3 5% 5% 5% 5% 38%	1520
	11th to 20th	Day	23% 5% 2 4 4 2 4 3 4 6% 44%	1906
	21st to end	Day	19% 11% 4 6% 6% 4 4 4 4 6% 33%	2772
January	1st to 10th	Night	17% 7% 2 4 4 3 3 4 5% 6% 46%	4429
	11th to 20th	Night	17% 8% 4 6% 4 2 3 3 4 4 43%	4440
	21st to end	Night	24% 11% 4 6% 5% 3 3 3 3 5% 32%	4812
February	1st to 10th	Night	17% 9% 3 5% 5% 2 4 3 4 6% 41%	2409
	11th to 20th	Night	15% 8% 3 5% 4 4 5% 4 5% 6% 41%	2218
	21st to end	Night	20% 6% 2 5% 6% 2 4 5% 4 5% 41%	1831
March	1st to 10th	Night	17% 6% 2 5% 4 3 3 5% 5% 6% 43%	2150
	11th to 20th	Night	16% 7% 3 5% 6% 3 5% 4 5% 8% 39%	2109
	21st to end	Night	18% 7% 3 4 4 2 4 4 4 7% 42%	1980
April	1st to 10th	Night	18% 8% 2 6% 5% 3 4 5% 5% 7% 38%	1800
	11th to 20th	Night	18% 5% 2 5% 4 2 4 5% 5% 7% 41%	1775
	21st to end	Night	21% 6% 3 6% 5% 3 3 3 4 5% 40%	1697
May	1st to 10th	Night	23% 7% 4 6% 5% 3 4 5% 5% 7% 32%	1620
	11th to 20th	Night	19% 7% 4 5% 4 3 4 4 5% 7% 38%	1500
	21st to end	Night	18% 6% 3 4 5% 2 5% 3 6% 7% 41%	1550
June	1st to 10th	Night	18% 6% 3 5% 5% 3 5% 5% 5% 6% 39%	1440
	11th to 20th	Night	17% 6% 2 5% 5% 3 5% 5% 5% 8% 40%	1440
	21st to end	Night	13% 5% 3 5% 6% 3 4 4 5% 9% 43%	1440
July	1st to 10th	Night	14% 4 2 4 6% 3 5% 5% 9% 8% 40%	1440
	11th to 20th	Night	14% 4 2 6% 5% 3 5% 5% 8% 10% 37%	1440
	21st to end	Night	12% 4 2 5% 5% 3 7% 5% 7% 7% 42%	1574
August	1st to 10th	Night	8% 6% 3 5% 5% 4 5% 6% 7% 8% 43%	1499
	11th to 20th	Night	11% 6% 2 7% 7% 4 5% 5% 6% 8% 39%	1752
	21st to end	Night	14% 5% 2 4 5% 3 4 5% 6% 8% 45%	1980
September	1st to 10th	Night	14% 6% 3 5% 6% 3 5% 4 4 7% 43%	1800
	11th to 20th	Night	14% 6% 2 4 4 2 3 3 4 6% 52%	1924
	21st to end	Night	16% 6% 3 4 4 2 5% 4 5% 6% 45%	1980
October	1st to 10th	Night	20% 7% 2 5% 5% 3 3 4 5% 5% 42%	2006
	11th to 20th	Night	16% 5% 2 4 4 3 4 5% 4 6% 47%	2177
	21st to end	Night	24% 6% 2 5% 4 3 4 4 4 5% 39%	2574
November	1st to 10th	Night	13% 5% 2 4 5% 3 4 4 5% 6% 48%	2407
	11th to 20th	Night	19% 6% 2 4 4 2 4 3 4 6% 45%	2470
	21st to end	Night	16% 7% 2 3 4 3 4 4 4 6% 46%	2502
December	1st to 10th	Night	20% 6% 3 5% 5% 3 4 4 5% 6% 39%	2660
	11th to 20th	Night	21% 6% 3 4 4 3 4 4 4 6% 41%	3288
	21st to end	Night	23% 11% 3 5% 5% 3 3 4 4 5% 35%	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	39% 5% 11% 32% 10% 2	2518
	11th to 20th	Day	49% 6% 11% 23% 10% 1	2520
	21st to end	Day	54% 5% 8% 21% 10% 2	2840
February	1st to 10th	Day	47% 6% 13% 19% 13% 2	1771
	11th to 20th	Day	42% 5% 10% 24% 16% 3	1857
	21st to end	Day	48% 5% 11% 19% 13% 3	1520
March	1st to 10th	Day	42% 5% 13% 22% 14% 4	1800
	11th to 20th	Day	43% 7% 11% 23% 14% 2	1849
	21st to end	Day	49% 4 8% 17% 18% 5%	2376
April	1st to 10th	Day	45% 5% 12% 19% 15% 4	2160
	11th to 20th	Day	41% 6% 10% 22% 18% 3	2134
	21st to end	Day	46% 5% 10% 20% 16% 4	2262
May	1st to 10th	Day	50% 6% 8% 20% 13% 2	2340
	11th to 20th	Day	43% 6% 10% 21% 16% 3	2412
	21st to end	Day	39% 9% 15% 20% 14% 2	2725
June	1st to 10th	Day	46% 8% 12% 22% 11% 1	2520
	11th to 20th	Day	44% 8% 13% 20% 13% 1	2520
	21st to end	Day	42% 8% 13% 23% 13% 1	2520
July	1st to 10th	Day	42% 9% 11% 19% 17% 2	2450
	11th to 20th	Day	39% 9% 14% 24% 13% 2	2445
	21st to end	Day	40% 9% 14% 18% 17% 2	2591
August	1st to 10th	Day	42% 9% 13% 22% 13%	2408
	11th to 20th	Day	39% 9% 15% 22% 14% 1	2144
	21st to end	Day	38% 8% 12% 22% 18% 2	2376
September	1st to 10th	Day	41% 8% 10% 21% 18% 2	2160
	11th to 20th	Day	34% 6% 11% 23% 23% 3	2035
	21st to end	Day	41% 6% 9% 22% 19% 3	1980
October	1st to 10th	Day	46% 6% 9% 22% 15% 3	1951
	11th to 20th	Day	37% 6% 13% 27% 16% 2	1782
	21st to end	Day	47% 5% 10% 20% 15% 3	1782
November	1st to 10th	Day	38% 5% 12% 23% 19% 3	1671
	11th to 20th	Day	40% 4 11% 23% 20% 3	1710
	21st to end	Day	42% 4 12% 25% 13% 3	1676
December	1st to 10th	Day	47% 5% 14% 17% 15% 1	1520
	11th to 20th	Day	43% 4 16% 18% 17% 2	1906
	21st to end	Day	53% 5% 10% 21% 9% 1	2772
January	1st to 10th	Night	40% 4 12% 30% 11% 4	4429
	11th to 20th	Night	45% 5% 12% 23% 12% 3	4440
	21st to end	Night	55% 5% 9% 19% 11% 2	4812
February	1st to 10th	Night	45% 5% 13% 22% 12% 2	2409
	11th to 20th	Night	44% 5% 10% 19% 17% 4	2220
	21st to end	Night	45% 6% 9% 22% 14% 5%	1831
March	1st to 10th	Night	41% 6% 12% 23% 15% 4	2160
	11th to 20th	Night	44% 6% 11% 21% 16% 3	2110
	21st to end	Night	43% 5% 10% 18% 19% 5%	1980
April	1st to 10th	Night	46% 6% 10% 20% 15% 3	1800
	11th to 20th	Night	42% 7% 10% 20% 20% 1	1775
	21st to end	Night	47% 5% 9% 21% 14% 4	1697
May	1st to 10th	Night	51% 7% 9% 17% 13% 2	1620
	11th to 20th	Night	46% 6% 11% 18% 16% 3	1501
	21st to end	Night	43% 8% 15% 20% 13% 1	1551
June	1st to 10th	Night	45% 7% 12% 19% 16% 1	1440
	11th to 20th	Night	43% 8% 13% 25% 10% 1	1440
	21st to end	Night	38% 8% 14% 25% 14%	1440
July	1st to 10th	Night	38% 11% 14% 20% 15% 2	1400
	11th to 20th	Night	41% 8% 16% 27% 8% 1	1392
	21st to end	Night	37% 10% 14% 22% 14% 3	1486
August	1st to 10th	Night	34% 10% 16% 23% 15% 2	1489
	11th to 20th	Night	43% 9% 13% 23% 11% 1	1752
	21st to end	Night	36% 7% 13% 23% 19% 1	1980
September	1st to 10th	Night	41% 7% 10% 25% 16% 1	1800
	11th to 20th	Night	35% 5% 11% 22% 26% 2	1924
	21st to end	Night	41% 7% 7% 22% 21% 3	1980
October	1st to 10th	Night	46% 6% 11% 21% 14% 3	2006
	11th to 20th	Night	39% 6% 12% 28% 15% 1	2177
	21st to end	Night	47% 5% 12% 20% 15% 1	2574
November	1st to 10th	Night	37% 6% 12% 21% 21% 4	2407
	11th to 20th	Night	41% 4 11% 22% 18% 3	2470
	21st to end	Night	40% 4 13% 29% 12% 2	2502
December	1st to 10th	Night	46% 6% 12% 21% 14% 1	2660
	11th to 20th	Night	44% 6% 14% 17% 17% 2	3288
	21st to end	Night	52% 4 11% 22% 12%	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	29% 26% 29% 14% 2	180
	11th to 20th	Day	31% 28% 27% 11% 3	180
	21st to end	Day	24% 30% 32% 9% 5% 1	218
February	1st to 10th	Day	34% 24% 30% 11% 1	331
	11th to 20th	Day	29% 27% 33% 10% 1	456
	21st to end	Day	33% 21% 31% 11% 3	362
March	1st to 10th	Day	25% 25% 34% 13% 3	420
	11th to 20th	Day	28% 26% 32% 10% 3 1	420
	21st to end	Day	32% 22% 31% 10% 4 1	462
April	1st to 10th	Day	29% 26% 28% 11% 5% 1	420
	11th to 20th	Day	29% 19% 32% 14% 6% 1	412
	21st to end	Day	31% 20% 33% 11% 4 1	420
May	1st to 10th	Day	35% 20% 26% 13% 6% 1	423
	11th to 20th	Day	24% 19% 37% 14% 5% 1	447
	21st to end	Day	21% 14% 29% 24% 9% 2	485
June	1st to 10th	Day	20% 16% 31% 23% 9% 2	450
	11th to 20th	Day	17% 18% 37% 19% 7% 2	450
	21st to end	Day	16% 15% 33% 26% 9% 1	450
July	1st to 10th	Day	17% 9% 31% 27% 14% 2	445
	11th to 20th	Day	14% 8% 33% 30% 14% 2	444
	21st to end	Day	14% 10% 39% 28% 8% 1	488
August	1st to 10th	Day	11% 10% 29% 37% 9% 4	446
	11th to 20th	Day	13% 7% 34% 28% 13% 5%	439
	21st to end	Day	13% 11% 34% 23% 14% 6%	495
September	1st to 10th	Day	20% 12% 26% 21% 17% 4	450
	11th to 20th	Day	17% 12% 29% 23% 11% 8%	450
	21st to end	Day	22% 13% 34% 18% 9% 5%	450
October	1st to 10th	Day	30% 12% 26% 17% 12% 4	450
	11th to 20th	Day	16% 19% 32% 23% 7% 2	441
	21st to end	Day	28% 17% 29% 19% 7% 1	396
November	1st to 10th	Day	19% 16% 31% 24% 8% 2	365
	11th to 20th	Day	30% 21% 24% 20% 5%	370
	21st to end	Day	26% 19% 28% 21% 5%	336
December	1st to 10th	Day	24% 24% 32% 14% 6%	180
	11th to 20th	Day	34% 24% 30% 11% 1	180
	21st to end	Day	31% 21% 28% 17% 2 1	198
January	1st to 10th	Night	23% 19% 38% 17% 3	760
	11th to 20th	Night	28% 20% 32% 19% 2	760
	21st to end	Night	22% 22% 35% 19% 2	836
February	1st to 10th	Night	24% 19% 35% 21% 2	760
	11th to 20th	Night	24% 23% 37% 14% 2	743
	21st to end	Night	27% 19% 35% 16% 3	611
March	1st to 10th	Night	24% 22% 35% 17% 2	720
	11th to 20th	Night	23% 21% 35% 19% 3 1	720
	21st to end	Night	24% 21% 34% 17% 3	792
April	1st to 10th	Night	25% 21% 35% 17% 3	720
	11th to 20th	Night	23% 18% 35% 21% 3	711
	21st to end	Night	24% 20% 33% 18% 4	617
May	1st to 10th	Night	27% 15% 34% 19% 5%	540
	11th to 20th	Night	22% 15% 39% 21% 3	439
	21st to end	Night	21% 8% 29% 33% 7% 1	389
June	1st to 10th	Night	21% 8% 33% 29% 9%	360
	11th to 20th	Night	20% 6% 32% 33% 9%	360
	21st to end	Night	15% 6% 35% 37% 8%	360
July	1st to 10th	Night	14% 5% 29% 38% 15%	350
	11th to 20th	Night	14% 4 25% 44% 12% 1	348
	21st to end	Night	12% 7% 30% 41% 9% 1	394
August	1st to 10th	Night	11% 4 33% 42% 9% 1	425
	11th to 20th	Night	14% 5% 26% 38% 15% 2	688
	21st to end	Night	15% 5% 26% 36% 17% 2	792
September	1st to 10th	Night	17% 6% 31% 33% 12% 2	720
	11th to 20th	Night	18% 6% 27% 31% 16% 2	720
	21st to end	Night	20% 8% 29% 28% 15% 1	720
October	1st to 10th	Night	25% 10% 28% 24% 11% 2	720
	11th to 20th	Night	20% 13% 30% 28% 8%	720
	21st to end	Night	29% 13% 32% 20% 6%	792
November	1st to 10th	Night	17% 14% 34% 25% 9% 1	740
	11th to 20th	Night	24% 16% 34% 19% 6% 1	760
	21st to end	Night	24% 16% 32% 23% 5% 1	760
December	1st to 10th	Night	26% 17% 32% 20% 5% 1	760
	11th to 20th	Night	24% 21% 31% 21% 3	760
	21st to end	Night	29% 16% 36% 17% 2	836

Page generated at 2024-02-22 06:05:46. Version ac07

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