Springfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Springfield clear sky chart from 2005-11-06 to 2024-03-01.

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%	78320
	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 40%	81077
Transparency	Day	45% 4 11% 23% 15% 2	78025
	Night	46% 4 11% 23% 14% 2	80906
Seeing	Day	22% 13% 29% 22% 10% 3	13998
	Night	21% 10% 31% 29% 8% 1	23160

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 6% 4 3 4 4 5% 6% 44%	2517
	11th to 20th	Day	16% 8% 4 8% 6% 3 4 5% 5% 5% 35%	2520
	21st to end	Day	21% 9% 4 7% 5% 3 4 4 4 6% 31%	2781
February	1st to 10th	Day	18% 8% 2 5% 6% 3 5% 5% 6% 8% 35%	1772
	11th to 20th	Day	14% 8% 4 6% 5% 3 5% 4 5% 7% 40%	1848
	21st to end	Day	20% 8% 3 5% 6% 2 4 5% 4 6% 37%	1570
March	1st to 10th	Day	15% 7% 3 6% 5% 3 4 5% 5% 7% 41%	1797
	11th to 20th	Day	17% 7% 3 6% 5% 3 4 5% 6% 8% 37%	1843
	21st to end	Day	20% 8% 3 6% 4 3 4 4 4 6% 41%	2375
April	1st to 10th	Day	19% 6% 3 5% 6% 3 5% 4 5% 7% 38%	2160
	11th to 20th	Day	17% 6% 2 5% 5% 3 4 4 5% 7% 42%	2134
	21st to end	Day	22% 6% 2 5% 5% 3 4 4 5% 7% 37%	2286
May	1st to 10th	Day	25% 7% 3 6% 5% 2 4 4 5% 6% 33%	2340
	11th to 20th	Day	17% 6% 3 5% 4 3 4 4 6% 7% 41%	2410
	21st to end	Day	15% 5% 3 5% 5% 3 4 5% 6% 7% 42%	2725
June	1st to 10th	Day	17% 6% 3 5% 6% 3 5% 5% 6% 8% 35%	2520
	11th to 20th	Day	17% 5% 2 5% 5% 3 4 6% 6% 9% 37%	2520
	21st to end	Day	15% 5% 3 5% 5% 3 5% 6% 6% 9% 37%	2520
July	1st to 10th	Day	11% 6% 3 5% 6% 4 6% 5% 6% 8% 41%	2520
	11th to 20th	Day	12% 5% 3 5% 6% 3 5% 5% 7% 10% 40%	2520
	21st to end	Day	13% 5% 3 6% 6% 4 5% 5% 6% 9% 39%	2744
August	1st to 10th	Day	10% 6% 2 6% 6% 3 5% 6% 7% 9% 40%	2420
	11th to 20th	Day	13% 5% 2 5% 6% 4 5% 6% 5% 7% 42%	2181
	21st to end	Day	12% 4 2 4 6% 3 4 5% 6% 9% 44%	2376
September	1st to 10th	Day	14% 6% 2 5% 5% 3 5% 5% 6% 7% 43%	2160
	11th to 20th	Day	16% 6% 2 4 4 1 3 4 4 6% 50%	2026
	21st to end	Day	17% 5% 2 4 4 2 4 5% 6% 7% 43%	1980
October	1st to 10th	Day	25% 6% 2 6% 4 3 4 4 4 4 39%	1962
	11th to 20th	Day	14% 7% 2 4 5% 3 3 5% 6% 6% 44%	1761
	21st to end	Day	23% 7% 2 5% 4 3 4 4 5% 5% 37%	1782
November	1st to 10th	Day	14% 7% 3 4 4 2 4 4 4 5% 48%	1671
	11th to 20th	Day	20% 6% 2 4 3 3 3 5% 5% 7% 44%	1710
	21st to end	Day	19% 6% 3 5% 4 2 4 4 4 6% 42%	1671
December	1st to 10th	Day	19% 7% 3 6% 5% 4 5% 5% 5% 5% 36%	1520
	11th to 20th	Day	23% 6% 2 4 4 2 3 3 5% 6% 42%	1906
	21st to end	Day	21% 12% 3 6% 5% 3 3 4 4 7% 32%	2772
January	1st to 10th	Night	17% 7% 3 5% 4 3 4 4 5% 6% 44%	4429
	11th to 20th	Night	16% 9% 3 8% 6% 3 4 3 5% 5% 39%	4440
	21st to end	Night	23% 12% 4 7% 5% 3 3 3 5% 5% 30%	4872
February	1st to 10th	Night	16% 10% 3 5% 4 3 5% 5% 5% 5% 39%	2405
	11th to 20th	Night	14% 8% 3 7% 5% 3 5% 4 5% 7% 40%	2218
	21st to end	Night	19% 7% 4 6% 6% 3 4 3 5% 6% 38%	1884
March	1st to 10th	Night	17% 7% 3 6% 5% 3 4 4 6% 7% 40%	2157
	11th to 20th	Night	17% 8% 3 5% 6% 3 5% 4 4 6% 39%	2114
	21st to end	Night	19% 7% 3 5% 3 2 4 4 4 6% 42%	1980
April	1st to 10th	Night	19% 8% 3 6% 6% 3 4 3 4 7% 37%	1800
	11th to 20th	Night	21% 6% 3 5% 5% 3 4 4 4 6% 40%	1775
	21st to end	Night	23% 7% 3 5% 4 2 4 3 3 6% 40%	1673
May	1st to 10th	Night	23% 8% 3 6% 5% 3 5% 4 5% 5% 32%	1620
	11th to 20th	Night	20% 5% 2 5% 5% 3 5% 5% 7% 7% 39%	1497
	21st to end	Night	16% 5% 3 4 5% 3 4 5% 5% 9% 41%	1550
June	1st to 10th	Night	18% 5% 2 6% 5% 2 4 4 6% 7% 41%	1440
	11th to 20th	Night	19% 7% 3 4 5% 3 4 5% 5% 9% 37%	1440
	21st to end	Night	14% 5% 2 4 6% 3 4 5% 5% 10% 42%	1440
July	1st to 10th	Night	14% 4 1 5% 5% 4 5% 5% 7% 9% 42%	1440
	11th to 20th	Night	14% 4 3 6% 4 4 5% 5% 7% 10% 37%	1440
	21st to end	Night	10% 5% 2 4 5% 3 6% 6% 7% 8% 44%	1574
August	1st to 10th	Night	9% 6% 3 5% 5% 3 5% 5% 7% 9% 44%	1499
	11th to 20th	Night	12% 5% 3 6% 6% 5% 5% 7% 7% 8% 38%	1716
	21st to end	Night	14% 5% 2 5% 4 3 4 4 5% 8% 47%	1980
September	1st to 10th	Night	16% 6% 2 4 6% 3 4 4 4 7% 45%	1800
	11th to 20th	Night	14% 6% 2 4 3 2 4 3 3 5% 53%	1933
	21st to end	Night	17% 6% 2 4 5% 2 3 4 5% 6% 44%	1980
October	1st to 10th	Night	22% 6% 2 4 5% 2 4 4 4 5% 41%	1993
	11th to 20th	Night	17% 6% 2 4 4 3 4 4 5% 7% 46%	2197
	21st to end	Night	24% 6% 2 5% 4 3 4 4 4 5% 38%	2574
November	1st to 10th	Night	15% 6% 2 4 3 3 3 4 4 6% 48%	2407
	11th to 20th	Night	20% 6% 2 4 4 3 4 4 4 5% 45%	2470
	21st to end	Night	17% 7% 2 5% 4 2 4 4 5% 6% 44%	2508
December	1st to 10th	Night	21% 7% 2 6% 5% 3 4 4 4 7% 37%	2660
	11th to 20th	Night	21% 8% 2 4 4 3 4 4 6% 6% 39%	3288
	21st to end	Night	23% 11% 3 6% 5% 3 3 4 4 5% 34%	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	42% 2 12% 33% 9% 1	2518
	11th to 20th	Day	53% 4 10% 24% 9% 1	2520
	21st to end	Day	55% 3 11% 21% 9% 1	2781
February	1st to 10th	Day	48% 3 14% 22% 12% 1	1772
	11th to 20th	Day	46% 4 9% 24% 15% 2	1857
	21st to end	Day	50% 3 11% 21% 14% 2	1570
March	1st to 10th	Day	44% 3 13% 23% 13% 3	1800
	11th to 20th	Day	47% 4 11% 22% 14% 3	1843
	21st to end	Day	47% 3 8% 19% 18% 5%	2375
April	1st to 10th	Day	47% 3 9% 22% 15% 3	2160
	11th to 20th	Day	44% 3 9% 22% 19% 3	2134
	21st to end	Day	49% 3 8% 20% 16% 4	2286
May	1st to 10th	Day	54% 4 8% 20% 14% 2	2340
	11th to 20th	Day	43% 4 9% 23% 18% 3	2414
	21st to end	Day	41% 5% 14% 24% 14% 3	2725
June	1st to 10th	Day	47% 5% 12% 23% 12% 1	2520
	11th to 20th	Day	44% 4 14% 23% 14% 1	2520
	21st to end	Day	44% 5% 12% 23% 15% 1	2520
July	1st to 10th	Day	41% 4 11% 24% 16% 3	2450
	11th to 20th	Day	40% 4 13% 27% 13% 1	2445
	21st to end	Day	42% 5% 12% 23% 16% 3	2591
August	1st to 10th	Day	40% 5% 15% 26% 13% 1	2406
	11th to 20th	Day	41% 5% 12% 26% 14% 1	2181
	21st to end	Day	37% 4 10% 27% 19% 2	2376
September	1st to 10th	Day	41% 4 10% 26% 18% 2	2160
	11th to 20th	Day	37% 2 9% 26% 24% 2	2026
	21st to end	Day	39% 4 9% 25% 20% 3	1980
October	1st to 10th	Day	50% 3 8% 22% 14% 4	1962
	11th to 20th	Day	40% 3 11% 29% 14% 2	1761
	21st to end	Day	49% 4 11% 20% 13% 3	1782
November	1st to 10th	Day	41% 4 12% 25% 16% 3	1671
	11th to 20th	Day	42% 3 11% 23% 18% 3	1710
	21st to end	Day	45% 3 11% 27% 11% 2	1671
December	1st to 10th	Day	50% 4 13% 18% 13% 1	1520
	11th to 20th	Day	45% 2 15% 22% 15% 1	1906
	21st to end	Day	56% 3 10% 21% 10%	2772
January	1st to 10th	Night	44% 2 12% 29% 11% 3	4429
	11th to 20th	Night	49% 3 10% 24% 12% 2	4440
	21st to end	Night	59% 2 9% 19% 10% 1	4872
February	1st to 10th	Night	47% 3 13% 23% 12% 2	2405
	11th to 20th	Night	46% 4 9% 22% 16% 3	2220
	21st to end	Night	50% 3 7% 24% 12% 4	1884
March	1st to 10th	Night	45% 3 9% 25% 15% 3	2167
	11th to 20th	Night	47% 4 11% 21% 15% 3	2115
	21st to end	Night	45% 3 9% 19% 19% 5%	1980
April	1st to 10th	Night	50% 2 9% 21% 16% 3	1800
	11th to 20th	Night	48% 2 9% 20% 20% 1	1775
	21st to end	Night	49% 3 8% 22% 14% 5%	1673
May	1st to 10th	Night	54% 4 8% 18% 13% 3	1620
	11th to 20th	Night	46% 4 10% 22% 14% 4	1498
	21st to end	Night	42% 5% 17% 22% 12% 1	1551
June	1st to 10th	Night	45% 5% 12% 25% 13% 1	1440
	11th to 20th	Night	46% 4 14% 23% 13%	1440
	21st to end	Night	39% 5% 15% 26% 14% 1	1440
July	1st to 10th	Night	38% 6% 15% 24% 16% 1	1400
	11th to 20th	Night	43% 5% 15% 27% 9% 1	1392
	21st to end	Night	37% 5% 15% 25% 15% 2	1486
August	1st to 10th	Night	36% 6% 15% 27% 14% 2	1489
	11th to 20th	Night	42% 7% 13% 25% 13% 1	1716
	21st to end	Night	36% 5% 12% 27% 19% 1	1980
September	1st to 10th	Night	41% 4 11% 25% 18% 1	1800
	11th to 20th	Night	35% 4 9% 25% 25% 2	1933
	21st to end	Night	41% 3 8% 24% 22% 3	1980
October	1st to 10th	Night	47% 4 11% 23% 12% 3	1993
	11th to 20th	Night	40% 4 12% 29% 14% 1	2197
	21st to end	Night	50% 3 11% 22% 13% 1	2574
November	1st to 10th	Night	38% 4 12% 23% 20% 3	2407
	11th to 20th	Night	43% 3 11% 22% 18% 3	2470
	21st to end	Night	42% 3 14% 28% 11% 1	2508
December	1st to 10th	Night	49% 4 13% 22% 13% 1	2660
	11th to 20th	Night	47% 4 14% 19% 16% 2	3288
	21st to end	Night	55% 3 8% 24% 9% 1	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	27% 15% 32% 19% 7% 1	180
	11th to 20th	Day	26% 25% 28% 16% 5%	180
	21st to end	Day	20% 23% 33% 18% 5% 2	202
February	1st to 10th	Day	30% 20% 31% 17% 3	332
	11th to 20th	Day	25% 23% 34% 16% 3	456
	21st to end	Day	30% 17% 32% 18% 4	382
March	1st to 10th	Day	25% 18% 30% 22% 4 1	420
	11th to 20th	Day	28% 21% 29% 17% 4	420
	21st to end	Day	27% 19% 30% 15% 6% 3	462
April	1st to 10th	Day	30% 18% 29% 15% 7% 1	420
	11th to 20th	Day	27% 17% 31% 15% 9% 1	412
	21st to end	Day	33% 15% 28% 18% 5% 2	420
May	1st to 10th	Day	35% 16% 26% 14% 9% 1	423
	11th to 20th	Day	23% 13% 40% 16% 6% 2	447
	21st to end	Day	20% 11% 30% 23% 12% 4	485
June	1st to 10th	Day	18% 14% 30% 22% 12% 3	450
	11th to 20th	Day	19% 12% 34% 24% 9% 3	450
	21st to end	Day	15% 13% 31% 26% 12% 3	450
July	1st to 10th	Day	16% 7% 29% 29% 15% 4	445
	11th to 20th	Day	14% 7% 24% 31% 19% 5%	444
	21st to end	Day	14% 6% 30% 32% 15% 3	488
August	1st to 10th	Day	12% 9% 25% 33% 15% 5%	446
	11th to 20th	Day	15% 6% 29% 28% 15% 7%	439
	21st to end	Day	12% 9% 26% 27% 19% 6%	495
September	1st to 10th	Day	20% 7% 22% 25% 17% 8%	450
	11th to 20th	Day	18% 10% 25% 21% 14% 11%	450
	21st to end	Day	20% 9% 29% 21% 14% 7%	450
October	1st to 10th	Day	30% 9% 24% 18% 11% 8%	450
	11th to 20th	Day	19% 14% 29% 23% 13% 3	430
	21st to end	Day	30% 11% 27% 23% 9% 1	396
November	1st to 10th	Day	21% 12% 29% 24% 11% 3	365
	11th to 20th	Day	29% 14% 29% 20% 7% 1	370
	21st to end	Day	26% 12% 31% 21% 8% 1	331
December	1st to 10th	Day	22% 21% 31% 20% 7% 1	180
	11th to 20th	Day	30% 21% 35% 11% 3	180
	21st to end	Day	25% 18% 35% 18% 3 2	198
January	1st to 10th	Night	21% 13% 38% 25% 4	760
	11th to 20th	Night	27% 13% 31% 25% 3	760
	21st to end	Night	19% 12% 37% 28% 3	836
February	1st to 10th	Night	23% 13% 36% 26% 2	760
	11th to 20th	Night	21% 16% 41% 20% 2	743
	21st to end	Night	25% 15% 34% 23% 3	628
March	1st to 10th	Night	23% 17% 34% 23% 2	723
	11th to 20th	Night	23% 14% 38% 22% 3	720
	21st to end	Night	24% 13% 33% 23% 6%	792
April	1st to 10th	Night	25% 15% 32% 24% 4	720
	11th to 20th	Night	24% 15% 32% 22% 7%	711
	21st to end	Night	27% 16% 30% 23% 4	593
May	1st to 10th	Night	27% 13% 33% 22% 5% 1	540
	11th to 20th	Night	21% 13% 38% 23% 5%	436
	21st to end	Night	20% 7% 30% 35% 6% 1	389
June	1st to 10th	Night	21% 4 29% 38% 8% 1	360
	11th to 20th	Night	20% 8% 31% 32% 9%	360
	21st to end	Night	15% 2 31% 41% 10% 1	360
July	1st to 10th	Night	14% 3 27% 41% 14% 1	350
	11th to 20th	Night	15% 4 19% 46% 16%	348
	21st to end	Night	11% 4 23% 49% 12%	394
August	1st to 10th	Night	11% 3 27% 45% 14%	425
	11th to 20th	Night	13% 3 23% 40% 19% 2	652
	21st to end	Night	15% 5% 19% 41% 19% 2	792
September	1st to 10th	Night	18% 4 26% 36% 14% 1	720
	11th to 20th	Night	16% 6% 22% 34% 20% 2	720
	21st to end	Night	20% 7% 25% 33% 14% 2	720
October	1st to 10th	Night	25% 6% 23% 31% 13% 2	720
	11th to 20th	Night	20% 9% 28% 32% 10% 1	720
	21st to end	Night	28% 10% 30% 25% 7% 1	792
November	1st to 10th	Night	19% 8% 32% 31% 9% 1	740
	11th to 20th	Night	23% 10% 34% 25% 8% 1	760
	21st to end	Night	22% 13% 31% 29% 5% 1	760
December	1st to 10th	Night	24% 12% 36% 22% 5% 1	760
	11th to 20th	Night	24% 12% 33% 28% 3	760
	21st to end	Night	28% 11% 34% 24% 3	836

Page generated at 2024-02-27 06:30:18. Version ac07

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