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 2024-11-01.

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% 7% 3 6% 4 4 4 4 5% 7% 38%	101226
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 39%	97721
Transparency	Day	46% 4 11% 23% 14% 2	100984
	Night	47% 4 11% 23% 14% 2	97583
Seeing	Day	22% 13% 29% 22% 10% 3	14964
	Night	21% 10% 31% 29% 8% 1	23943

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	14% 7% 3 7% 4 4 4 3 5% 6% 44%	2517
	11th to 20th	Day	16% 8% 4 10% 5% 5% 4 4 5% 5% 35%	2520
	21st to end	Day	21% 9% 4 8% 4 4 4 3 4 6% 31%	2781
February	1st to 10th	Day	18% 8% 2 6% 5% 4 4 4 6% 7% 35%	1772
	11th to 20th	Day	13% 8% 3 7% 5% 4 4 3 5% 7% 40%	1848
	21st to end	Day	19% 9% 3 6% 5% 3 4 4 4 6% 36%	1570
March	1st to 10th	Day	24% 11% 4 8% 5% 3 3 2 3 4 33%	3116
	11th to 20th	Day	12% 8% 3 6% 5% 5% 5% 4 6% 8% 38%	3245
	21st to end	Day	21% 8% 3 6% 4 3 3 3 5% 6% 38%	4165
April	1st to 10th	Day	19% 7% 3 6% 5% 4 4 3 5% 7% 37%	2280
	11th to 20th	Day	18% 6% 2 6% 4 4 4 3 6% 7% 41%	2254
	21st to end	Day	21% 7% 2 6% 4 4 4 3 5% 6% 38%	2413
May	1st to 10th	Day	26% 8% 3 7% 4 5% 4 3 5% 7% 29%	4106
	11th to 20th	Day	21% 9% 3 7% 4 3 4 3 5% 6% 35%	4288
	21st to end	Day	13% 5% 2 5% 4 4 4 4 6% 8% 43%	4837
June	1st to 10th	Day	16% 7% 2 6% 5% 4 5% 4 6% 8% 36%	2660
	11th to 20th	Day	16% 5% 2 6% 4 5% 4 5% 6% 10% 37%	2660
	21st to end	Day	15% 6% 3 6% 4 4 5% 5% 6% 8% 36%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 6% 6% 4 7% 9% 37%	4440
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 7% 10% 38%	4440
	21st to end	Day	17% 8% 3 7% 5% 5% 4 4 5% 7% 36%	4814
August	1st to 10th	Day	16% 6% 3 8% 5% 5% 5% 4 7% 9% 32%	4268
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	3824
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	4180
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 6% 44%	2280
	11th to 20th	Day	14% 7% 2 5% 3 2 3 3 4 6% 50%	2138
	21st to end	Day	17% 5% 2 6% 4 3 4 4 6% 7% 41%	2090
October	1st to 10th	Day	23% 6% 2 6% 4 3 4 3 4 5% 40%	2071
	11th to 20th	Day	14% 7% 2 5% 4 3 4 3 6% 6% 45%	1858
	21st to end	Day	21% 7% 2 6% 3 4 4 3 5% 6% 39%	1881
November	1st to 10th	Day	14% 8% 3 5% 4 3 4 3 4 5% 47%	1671
	11th to 20th	Day	19% 7% 1 4 3 3 2 4 5% 6% 44%	1710
	21st to end	Day	19% 7% 2 5% 5% 3 4 4 4 6% 42%	1671
December	1st to 10th	Day	19% 7% 3 7% 5% 4 4 5% 6% 5% 36%	1520
	11th to 20th	Day	23% 7% 2 5% 3 2 3 3 5% 6% 42%	1906
	21st to end	Day	21% 12% 2 7% 5% 4 3 3 4 7% 32%	2772
January	1st to 10th	Night	17% 7% 2 5% 4 4 3 3 5% 6% 44%	4429
	11th to 20th	Night	16% 9% 3 9% 5% 4 4 2 5% 5% 39%	4440
	21st to end	Night	22% 13% 4 8% 4 3 4 3 5% 5% 30%	4872
February	1st to 10th	Night	16% 10% 3 6% 4 4 4 4 5% 5% 39%	2405
	11th to 20th	Night	13% 8% 3 8% 4 4 4 3 6% 6% 39%	2218
	21st to end	Night	18% 8% 3 7% 5% 4 4 3 4 6% 38%	1884
March	1st to 10th	Night	28% 8% 2 6% 4 3 3 3 5% 6% 31%	3724
	11th to 20th	Night	13% 9% 3 6% 4 5% 5% 3 5% 6% 40%	3698
	21st to end	Night	23% 8% 2 6% 3 3 3 3 5% 5% 37%	3466
April	1st to 10th	Night	19% 8% 3 6% 6% 4 4 3 5% 6% 36%	1900
	11th to 20th	Night	21% 7% 2 5% 5% 4 3 3 4 6% 39%	1875
	21st to end	Night	22% 7% 3 5% 4 3 3 3 3 6% 40%	1765
May	1st to 10th	Night	25% 9% 3 7% 4 4 4 3 5% 6% 29%	2834
	11th to 20th	Night	20% 9% 3 7% 5% 5% 5% 4 6% 6% 29%	2633
	21st to end	Night	16% 5% 2 5% 4 4 4 4 5% 9% 42%	2738
June	1st to 10th	Night	17% 5% 2 6% 5% 3 4 4 6% 6% 41%	1520
	11th to 20th	Night	18% 7% 3 4 4 4 4 4 6% 8% 38%	1520
	21st to end	Night	14% 7% 2 5% 5% 4 4 4 5% 9% 41%	1520
July	1st to 10th	Night	13% 5% 2 6% 4 5% 5% 5% 8% 9% 37%	2520
	11th to 20th	Night	15% 7% 2 7% 4 5% 4 3 6% 9% 37%	2520
	21st to end	Night	16% 9% 3 7% 5% 4 5% 4 6% 6% 36%	2739
August	1st to 10th	Night	21% 6% 3 7% 4 5% 4 4 6% 7% 31%	2629
	11th to 20th	Night	13% 7% 4 8% 5% 5% 5% 4 6% 7% 37%	3000
	21st to end	Night	9% 5% 2 5% 3 4 4 3 5% 8% 53%	3476
September	1st to 10th	Night	15% 6% 2 5% 5% 4 4 3 4 7% 45%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 3 5% 53%	2041
	21st to end	Night	17% 7% 2 6% 4 4 3 3 5% 6% 43%	2090
October	1st to 10th	Night	21% 6% 2 5% 4 4 4 3 4 5% 41%	2104
	11th to 20th	Night	16% 6% 1 6% 3 3 4 3 5% 6% 47%	2320
	21st to end	Night	24% 6% 2 6% 3 4 3 3 5% 5% 39%	2717
November	1st to 10th	Night	15% 6% 2 5% 3 3 3 4 4 6% 48%	2414
	11th to 20th	Night	20% 7% 2 5% 3 4 3 3 4 5% 45%	2470
	21st to end	Night	17% 8% 2 5% 4 3 3 4 4 6% 44%	2508
December	1st to 10th	Night	21% 8% 2 7% 4 4 4 3 5% 7% 37%	2660
	11th to 20th	Night	21% 8% 2 5% 3 4 3 4 6% 6% 39%	3288
	21st to end	Night	23% 11% 3 7% 4 4 3 3 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	57% 2 11% 18% 10% 2	3119
	11th to 20th	Day	45% 3 12% 27% 11% 2	3245
	21st to end	Day	49% 2 5% 19% 21% 5%	4165
April	1st to 10th	Day	49% 3 9% 22% 15% 3	2280
	11th to 20th	Day	44% 3 9% 22% 18% 3	2254
	21st to end	Day	48% 3 8% 20% 17% 4	2413
May	1st to 10th	Day	56% 3 12% 16% 12% 1	4120
	11th to 20th	Day	51% 2 14% 21% 10% 2	4292
	21st to end	Day	39% 3 10% 26% 19% 2	4837
June	1st to 10th	Day	46% 5% 12% 24% 13% 1	2660
	11th to 20th	Day	43% 4 14% 23% 14% 2	2660
	21st to end	Day	44% 5% 12% 22% 15% 1	2660
July	1st to 10th	Day	43% 6% 11% 22% 16% 2	4370
	11th to 20th	Day	41% 5% 15% 24% 13% 2	4365
	21st to end	Day	48% 5% 11% 20% 15% 2	4661
August	1st to 10th	Day	48% 6% 16% 21% 9% 1	4254
	11th to 20th	Day	41% 5% 13% 30% 10% 1	3863
	21st to end	Day	35% 6% 13% 29% 16% 2	4180
September	1st to 10th	Day	40% 4 10% 26% 19% 2	2280
	11th to 20th	Day	36% 3 8% 27% 24% 2	2138
	21st to end	Day	41% 4 9% 24% 19% 2	2090
October	1st to 10th	Day	48% 3 9% 22% 15% 3	2071
	11th to 20th	Day	39% 3 11% 29% 16% 2	1858
	21st to end	Day	47% 4 11% 21% 14% 3	1881
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	56% 2 8% 21% 11% 2	3734
	11th to 20th	Night	45% 3 13% 23% 13% 2	3699
	21st to end	Night	50% 2 6% 15% 22% 5%	3466
April	1st to 10th	Night	50% 2 9% 21% 15% 3	1900
	11th to 20th	Night	49% 2 8% 19% 20% 1	1875
	21st to end	Night	48% 2 8% 22% 14% 5%	1765
May	1st to 10th	Night	57% 3 12% 16% 10% 2	2840
	11th to 20th	Night	56% 4 13% 17% 8% 2	2634
	21st to end	Night	41% 4 16% 24% 14% 1	2739
June	1st to 10th	Night	44% 4 12% 25% 14% 1	1520
	11th to 20th	Night	45% 4 15% 24% 13%	1520
	21st to end	Night	41% 5% 14% 25% 14% 1	1520
July	1st to 10th	Night	41% 8% 16% 20% 15% 1	2480
	11th to 20th	Night	44% 6% 14% 23% 12% 1	2472
	21st to end	Night	48% 5% 11% 19% 15% 1	2651
August	1st to 10th	Night	52% 7% 12% 20% 9% 1	2619
	11th to 20th	Night	44% 6% 14% 26% 9%	3027
	21st to end	Night	28% 6% 16% 33% 16% 1	3476
September	1st to 10th	Night	40% 4 11% 26% 19% 1	1900
	11th to 20th	Night	34% 4 9% 26% 25% 2	2041
	21st to end	Night	42% 3 8% 23% 21% 3	2090
October	1st to 10th	Night	45% 4 12% 23% 13% 3	2104
	11th to 20th	Night	39% 3 12% 29% 16% 1	2320
	21st to end	Night	48% 3 12% 23% 13% 1	2717
November	1st to 10th	Night	38% 4 12% 23% 20% 3	2414
	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	29% 18% 31% 18% 4	382
March	1st to 10th	Day	26% 18% 30% 21% 4 1	460
	11th to 20th	Day	28% 22% 28% 17% 4	460
	21st to end	Day	28% 19% 31% 14% 5% 3	506
April	1st to 10th	Day	30% 18% 28% 15% 7% 1	460
	11th to 20th	Day	29% 17% 30% 15% 8% 1	452
	21st to end	Day	31% 15% 29% 18% 5% 2	460
May	1st to 10th	Day	33% 16% 25% 15% 9% 1	463
	11th to 20th	Day	23% 13% 39% 16% 7% 2	487
	21st to end	Day	19% 11% 31% 24% 11% 4	529
June	1st to 10th	Day	17% 14% 31% 23% 12% 3	490
	11th to 20th	Day	17% 11% 33% 26% 10% 3	490
	21st to end	Day	15% 14% 31% 25% 11% 3	490
July	1st to 10th	Day	16% 7% 29% 29% 15% 4	485
	11th to 20th	Day	13% 6% 27% 31% 18% 5%	484
	21st to end	Day	15% 6% 30% 32% 15% 2	532
August	1st to 10th	Day	13% 9% 25% 33% 15% 5%	486
	11th to 20th	Day	15% 7% 29% 28% 15% 7%	479
	21st to end	Day	11% 8% 26% 28% 20% 7%	539
September	1st to 10th	Day	19% 8% 23% 25% 17% 9%	490
	11th to 20th	Day	17% 9% 24% 21% 16% 13%	490
	21st to end	Day	20% 9% 30% 22% 14% 6%	490
October	1st to 10th	Day	28% 10% 24% 19% 12% 8%	490
	11th to 20th	Day	18% 14% 29% 22% 13% 3	467
	21st to end	Day	28% 11% 26% 24% 9% 2	429
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% 16% 34% 23% 3	628
March	1st to 10th	Night	24% 16% 34% 23% 3	760
	11th to 20th	Night	23% 15% 38% 22% 3	760
	21st to end	Night	25% 14% 33% 22% 6%	836
April	1st to 10th	Night	24% 15% 33% 24% 4	760
	11th to 20th	Night	25% 15% 32% 22% 6%	751
	21st to end	Night	26% 16% 31% 23% 4	625
May	1st to 10th	Night	26% 13% 33% 22% 5% 1	570
	11th to 20th	Night	21% 13% 37% 24% 5%	460
	21st to end	Night	20% 8% 32% 34% 6% 1	411
June	1st to 10th	Night	20% 4 29% 38% 8% 1	380
	11th to 20th	Night	20% 8% 32% 31% 10%	380
	21st to end	Night	16% 3 31% 39% 10% 1	380
July	1st to 10th	Night	14% 4 27% 41% 13% 1	370
	11th to 20th	Night	15% 4 19% 45% 16%	368
	21st to end	Night	11% 5% 24% 47% 13%	416
August	1st to 10th	Night	12% 3 27% 44% 13%	449
	11th to 20th	Night	13% 4 23% 39% 19% 2	689
	21st to end	Night	14% 4 19% 41% 19% 2	836
September	1st to 10th	Night	18% 4 26% 36% 15% 1	760
	11th to 20th	Night	15% 6% 21% 34% 21% 3	760
	21st to end	Night	20% 6% 24% 34% 13% 2	760
October	1st to 10th	Night	24% 6% 23% 32% 13% 2	760
	11th to 20th	Night	19% 9% 29% 32% 11% 1	760
	21st to end	Night	28% 10% 30% 26% 7%	836
November	1st to 10th	Night	19% 8% 32% 31% 9% 1	743
	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 2024-10-29 11:20:51. Version ac07

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