Truman State University Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Truman State University Observatory clear sky chart from 2005-11-06 to 2024-11-03.

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% 8% 3 7% 4 4 4 4 5% 7% 41%	101342
	Night	12% 8% 3 7% 4 4 4 3 5% 6% 44%	97732
Transparency	Day	41% 6% 12% 25% 14% 2	101144
	Night	41% 5% 12% 24% 16% 2	97601
Seeing	Day	15% 10% 28% 28% 15% 5%	15744
	Night	15% 8% 32% 32% 12% 1	25562

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% 12% 4 14% 5% 4 4 4 4 7% 31%	2537
	11th to 20th	Day	12% 12% 4 10% 5% 6% 8% 3 4 6% 30%	2850
	21st to end	Day	15% 20% 8% 11% 5% 4 3 2 3 5% 24%	3135
February	1st to 10th	Day	15% 11% 3 8% 4 4 4 4 6% 8% 32%	1710
	11th to 20th	Day	12% 11% 4 8% 5% 4 4 3 6% 6% 38%	1671
	21st to end	Day	14% 10% 3 8% 4 4 4 3 5% 5% 41%	1570
March	1st to 10th	Day	16% 11% 2 6% 3 3 3 3 4 6% 43%	3398
	11th to 20th	Day	10% 8% 3 6% 4 4 5% 4 5% 6% 45%	3480
	21st to end	Day	20% 14% 4 8% 5% 4 4 3 4 6% 28%	3863
April	1st to 10th	Day	16% 9% 3 7% 5% 4 4 3 4 6% 39%	2280
	11th to 20th	Day	15% 9% 3 7% 4 4 4 3 5% 5% 41%	2254
	21st to end	Day	21% 8% 2 7% 4 4 5% 4 4 6% 35%	2292
May	1st to 10th	Day	14% 8% 2 8% 5% 5% 5% 4 6% 8% 35%	4082
	11th to 20th	Day	17% 8% 3 7% 4 4 4 4 5% 7% 38%	4328
	21st to end	Day	13% 6% 3 6% 4 4 4 4 4 6% 46%	4824
June	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 4 7% 10% 45%	2660
	11th to 20th	Day	5% 6% 3 5% 5% 5% 5% 5% 6% 9% 47%	2660
	21st to end	Day	9% 6% 2 5% 5% 4 5% 4 6% 9% 44%	2660
July	1st to 10th	Day	10% 7% 3 7% 6% 5% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 6% 9% 48%	4362
	21st to end	Day	7% 4 2 5% 5% 5% 6% 4 8% 11% 43%	4465
August	1st to 10th	Day	5% 3 1 5% 4 5% 5% 5% 8% 12% 45%	4104
	11th to 20th	Day	14% 5% 2 5% 4 4 5% 4 6% 9% 42%	3982
	21st to end	Day	6% 4 2 6% 3 5% 4 4 6% 9% 51%	4180
September	1st to 10th	Day	12% 4 2 5% 3 4 4 3 5% 7% 52%	2280
	11th to 20th	Day	11% 4 2 5% 3 3 4 4 5% 9% 51%	2280
	21st to end	Day	11% 5% 1 5% 3 4 4 3 4 7% 53%	1983
October	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 4 6% 51%	1900
	11th to 20th	Day	14% 7% 3 5% 3 3 3 3 4 5% 50%	1900
	21st to end	Day	16% 8% 2 6% 4 4 3 3 5% 6% 44%	2090
November	1st to 10th	Day	10% 8% 2 5% 4 3 4 2 4 6% 51%	1766
	11th to 20th	Day	14% 8% 3 8% 4 3 3 4 4 6% 44%	1615
	21st to end	Day	17% 11% 3 5% 4 3 3 3 5% 5% 41%	1520
December	1st to 10th	Day	12% 12% 3 7% 5% 4 5% 3 4 6% 39%	1520
	11th to 20th	Day	12% 10% 4 7% 4 4 4 4 5% 7% 39%	1918
	21st to end	Day	20% 12% 9% 11% 5% 4 4 3 5% 4 23%	2783
January	1st to 10th	Night	11% 11% 6% 14% 5% 5% 4 3 4 5% 32%	4414
	11th to 20th	Night	12% 12% 6% 10% 6% 5% 7% 4 6% 5% 28%	4120
	21st to end	Night	17% 15% 8% 11% 5% 4 4 3 4 6% 25%	4532
February	1st to 10th	Night	13% 11% 5% 9% 5% 4 4 3 5% 7% 35%	2470
	11th to 20th	Night	12% 10% 4 7% 4 4 4 3 6% 8% 40%	2394
	21st to end	Night	14% 9% 4 7% 4 4 3 2 4 5% 44%	1884
March	1st to 10th	Night	16% 12% 3 6% 3 3 3 3 4 5% 43%	3484
	11th to 20th	Night	14% 8% 2 5% 3 3 3 2 4 5% 52%	3480
	21st to end	Night	19% 11% 5% 10% 6% 4 5% 3 4 6% 26%	3768
April	1st to 10th	Night	12% 7% 3 5% 4 3 5% 3 4 7% 46%	1900
	11th to 20th	Night	13% 9% 2 6% 4 4 4 3 6% 6% 43%	1875
	21st to end	Night	18% 8% 3 6% 4 4 4 4 5% 5% 40%	1884
May	1st to 10th	Night	16% 8% 3 7% 4 4 5% 4 6% 7% 36%	2823
	11th to 20th	Night	12% 7% 3 6% 5% 4 5% 4 6% 8% 41%	2575
	21st to end	Night	9% 5% 2 5% 4 4 4 4 5% 8% 49%	2743
June	1st to 10th	Night	6% 4 1 4 4 3 5% 4 7% 9% 52%	1520
	11th to 20th	Night	7% 4 2 5% 3 4 5% 3 6% 9% 51%	1520
	21st to end	Night	6% 4 2 4 4 5% 4 3 6% 7% 54%	1520
July	1st to 10th	Night	13% 4 2 5% 4 3 5% 4 5% 9% 45%	2530
	11th to 20th	Night	4 3 1 5% 3 4 3 3 6% 8% 60%	2590
	21st to end	Night	6% 5% 2 5% 4 4 5% 4 7% 9% 50%	3098
August	1st to 10th	Night	4 3 1 4 3 3 4 3 6% 9% 60%	2836
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 6% 54%	2852
	21st to end	Night	4 3 2 4 3 3 4 3 6% 9% 58%	3476
September	1st to 10th	Night	10% 4 1 4 3 3 3 2 5% 6% 58%	1900
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 5% 7% 53%	1900
	21st to end	Night	8% 6% 2 5% 3 4 3 3 5% 6% 57%	2175
October	1st to 10th	Night	11% 6% 2 4 4 3 3 2 4 5% 55%	2280
	11th to 20th	Night	12% 5% 1 5% 3 3 4 3 4 5% 54%	2280
	21st to end	Night	17% 7% 2 6% 3 3 3 3 4 5% 47%	2508
November	1st to 10th	Night	10% 5% 2 4 3 2 3 3 4 6% 58%	2354
	11th to 20th	Night	12% 7% 2 5% 4 4 4 3 5% 6% 49%	2564
	21st to end	Night	18% 9% 3 6% 3 3 3 3 4 6% 43%	2660
December	1st to 10th	Night	13% 10% 3 7% 5% 3 5% 4 6% 5% 40%	2660
	11th to 20th	Night	13% 10% 3 8% 4 4 4 4 4 6% 41%	3279
	21st to end	Night	20% 17% 7% 10% 5% 4 4 2 4 4 23%	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	53% 5% 11% 21% 8% 1	2538
	11th to 20th	Day	55% 5% 11% 20% 8%	2850
	21st to end	Day	64% 4 9% 15% 7% 1	3135
February	1st to 10th	Day	48% 6% 14% 20% 10% 2	1710
	11th to 20th	Day	45% 4 13% 23% 14% 2	1680
	21st to end	Day	45% 5% 10% 25% 13% 2	1570
March	1st to 10th	Day	44% 6% 10% 22% 17% 1	3398
	11th to 20th	Day	38% 6% 12% 24% 19% 2	3480
	21st to end	Day	56% 7% 15% 17% 5% 1	3863
April	1st to 10th	Day	46% 5% 10% 26% 12% 1	2280
	11th to 20th	Day	45% 5% 9% 24% 15% 1	2254
	21st to end	Day	49% 6% 11% 21% 13% 1	2292
May	1st to 10th	Day	44% 8% 11% 19% 16% 1	4120
	11th to 20th	Day	46% 7% 11% 28% 9%	4332
	21st to end	Day	39% 5% 9% 27% 19% 1	4837
June	1st to 10th	Day	33% 9% 16% 28% 13% 2	2660
	11th to 20th	Day	33% 7% 13% 25% 19% 3	2660
	21st to end	Day	34% 8% 15% 25% 15% 3	2660
July	1st to 10th	Day	43% 7% 11% 24% 12% 2	4371
	11th to 20th	Day	30% 7% 13% 30% 18% 2	4287
	21st to end	Day	32% 9% 16% 28% 14% 1	4325
August	1st to 10th	Day	29% 8% 14% 34% 15% 1	4090
	11th to 20th	Day	38% 6% 12% 26% 17% 1	4021
	21st to end	Day	30% 6% 17% 29% 13% 5%	4179
September	1st to 10th	Day	32% 5% 11% 24% 21% 6%	2280
	11th to 20th	Day	30% 5% 11% 30% 21% 3	2280
	21st to end	Day	33% 5% 10% 30% 21% 3	1983
October	1st to 10th	Day	35% 4 10% 24% 25% 2	1900
	11th to 20th	Day	37% 4 7% 25% 23% 4	1900
	21st to end	Day	42% 5% 10% 23% 17% 3	2090
November	1st to 10th	Day	35% 4 13% 25% 20% 3	1766
	11th to 20th	Day	42% 5% 9% 25% 18% 2	1615
	21st to end	Day	46% 3 13% 23% 14%	1520
December	1st to 10th	Day	46% 5% 13% 22% 12% 1	1520
	11th to 20th	Day	44% 5% 14% 27% 9% 1	1915
	21st to end	Day	65% 3 9% 15% 6% 1	2783
January	1st to 10th	Night	54% 4 9% 21% 10% 1	4414
	11th to 20th	Night	57% 4 11% 17% 10% 1	4120
	21st to end	Night	61% 5% 10% 16% 7% 1	4532
February	1st to 10th	Night	50% 4 11% 20% 12% 2	2470
	11th to 20th	Night	43% 4 11% 25% 14% 2	2395
	21st to end	Night	43% 4 9% 23% 18% 4	1884
March	1st to 10th	Night	44% 5% 9% 23% 18% 1	3484
	11th to 20th	Night	36% 5% 9% 29% 16% 5%	3480
	21st to end	Night	59% 7% 14% 15% 4	3768
April	1st to 10th	Night	37% 5% 13% 27% 16% 3	1900
	11th to 20th	Night	42% 4 9% 24% 17% 4	1875
	21st to end	Night	45% 5% 11% 21% 16% 2	1884
May	1st to 10th	Night	45% 7% 13% 21% 13% 1	2850
	11th to 20th	Night	39% 9% 13% 26% 13%	2576
	21st to end	Night	32% 7% 12% 23% 24% 2	2751
June	1st to 10th	Night	27% 8% 17% 30% 16% 3	1520
	11th to 20th	Night	29% 7% 12% 27% 22% 4	1520
	21st to end	Night	28% 8% 15% 26% 20% 4	1520
July	1st to 10th	Night	36% 5% 12% 26% 17% 3	2490
	11th to 20th	Night	22% 6% 15% 32% 24% 2	2542
	21st to end	Night	28% 8% 20% 25% 18% 2	2999
August	1st to 10th	Night	21% 6% 17% 35% 19% 1	2826
	11th to 20th	Night	32% 5% 12% 28% 22% 1	2879
	21st to end	Night	23% 5% 19% 32% 16% 5%	3476
September	1st to 10th	Night	28% 4 10% 26% 25% 8%	1900
	11th to 20th	Night	30% 5% 12% 27% 21% 5%	1900
	21st to end	Night	29% 4 9% 30% 24% 3	2175
October	1st to 10th	Night	31% 4 10% 24% 27% 5%	2280
	11th to 20th	Night	34% 5% 7% 26% 23% 6%	2280
	21st to end	Night	40% 4 9% 23% 21% 2	2508
November	1st to 10th	Night	28% 4 15% 26% 22% 5%	2354
	11th to 20th	Night	37% 4 9% 29% 18% 3	2564
	21st to end	Night	44% 4 9% 27% 15% 1	2660
December	1st to 10th	Night	44% 6% 12% 26% 12% 1	2660
	11th to 20th	Night	44% 4 12% 26% 13% 1	3281
	21st to end	Night	66% 4 8% 14% 7% 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	19% 15% 36% 21% 8%	270
	11th to 20th	Day	26% 14% 43% 16% 1	270
	21st to end	Day	22% 14% 43% 18% 2	297
February	1st to 10th	Day	22% 19% 40% 16% 4	270
	11th to 20th	Day	20% 18% 37% 20% 4 1	270
	21st to end	Day	18% 19% 45% 13% 4	225
March	1st to 10th	Day	17% 17% 46% 18% 2	270
	11th to 20th	Day	25% 14% 36% 22% 4	270
	21st to end	Day	36% 18% 29% 14% 3 1	321
April	1st to 10th	Day	21% 16% 35% 21% 6% 1	460
	11th to 20th	Day	19% 16% 32% 23% 8% 2	452
	21st to end	Day	22% 15% 33% 23% 7% 1	472
May	1st to 10th	Day	19% 13% 36% 23% 8% 2	653
	11th to 20th	Day	20% 10% 28% 27% 13% 2	675
	21st to end	Day	16% 8% 26% 28% 17% 6%	734
June	1st to 10th	Day	6% 4 20% 37% 24% 8%	680
	11th to 20th	Day	8% 5% 25% 37% 20% 5%	680
	21st to end	Day	11% 8% 30% 30% 17% 4	680
July	1st to 10th	Day	9% 4 15% 34% 24% 14%	671
	11th to 20th	Day	7% 4 20% 37% 23% 9%	668
	21st to end	Day	9% 3 17% 38% 28% 6%	739
August	1st to 10th	Day	6% 3 18% 39% 26% 7%	676
	11th to 20th	Day	10% 4 16% 36% 28% 6%	632
	21st to end	Day	8% 3 14% 35% 29% 12%	539
September	1st to 10th	Day	12% 4 18% 33% 26% 8%	490
	11th to 20th	Day	10% 3 20% 32% 24% 11%	490
	21st to end	Day	11% 7% 33% 21% 21% 7%	307
October	1st to 10th	Day	18% 6% 31% 24% 14% 6%	300
	11th to 20th	Day	16% 22% 32% 22% 8% 1	300
	21st to end	Day	23% 18% 32% 20% 6%	330
November	1st to 10th	Day	15% 8% 40% 25% 9% 3	276
	11th to 20th	Day	17% 18% 34% 22% 7% 3	270
	21st to end	Day	21% 16% 34% 24% 4	270
December	1st to 10th	Day	11% 16% 41% 23% 6% 3	270
	11th to 20th	Day	17% 16% 40% 21% 6%	270
	21st to end	Day	24% 19% 41% 14% 3	297
January	1st to 10th	Night	14% 14% 41% 24% 7%	950
	11th to 20th	Night	16% 14% 41% 21% 6% 1	950
	21st to end	Night	16% 12% 41% 28% 3	1045
February	1st to 10th	Night	19% 12% 40% 26% 3	950
	11th to 20th	Night	17% 13% 38% 28% 3	920
	21st to end	Night	20% 13% 42% 21% 4	628
March	1st to 10th	Night	17% 10% 43% 25% 5%	613
	11th to 20th	Night	23% 9% 32% 29% 6% 1	570
	21st to end	Night	27% 11% 36% 21% 5%	627
April	1st to 10th	Night	15% 12% 40% 28% 5%	570
	11th to 20th	Night	18% 11% 35% 28% 7% 1	563
	21st to end	Night	21% 8% 33% 30% 8%	570
May	1st to 10th	Night	17% 5% 34% 35% 7%	570
	11th to 20th	Night	15% 6% 31% 34% 14% 1	561
	21st to end	Night	13% 6% 24% 36% 20% 1	617
June	1st to 10th	Night	7% 3 18% 46% 23% 2	570
	11th to 20th	Night	8% 3 24% 44% 21% 1	570
	21st to end	Night	7% 4 28% 41% 19%	570
July	1st to 10th	Night	8% 2 12% 40% 34% 5%	555
	11th to 20th	Night	6% 1 16% 45% 28% 4	552
	21st to end	Night	8% 15% 42% 33% 1	624
August	1st to 10th	Night	6% 2 14% 48% 28% 3	567
	11th to 20th	Night	10% 2 14% 40% 30% 4	564
	21st to end	Night	7% 2 12% 43% 34% 2	627
September	1st to 10th	Night	12% 2 17% 38% 28% 4	570
	11th to 20th	Night	12% 2 17% 39% 25% 5%	570
	21st to end	Night	9% 5% 25% 37% 20% 4	665
October	1st to 10th	Night	13% 4 29% 33% 18% 2	760
	11th to 20th	Night	15% 10% 35% 30% 10% 1	760
	21st to end	Night	21% 11% 33% 28% 7%	836
November	1st to 10th	Night	11% 9% 38% 32% 10% 1	749
	11th to 20th	Night	15% 11% 40% 26% 7%	854
	21st to end	Night	22% 9% 35% 27% 7%	950
December	1st to 10th	Night	18% 10% 39% 27% 6% 1	950
	11th to 20th	Night	21% 9% 36% 28% 6%	950
	21st to end	Night	22% 14% 37% 26% 2	1045

Page generated at 2024-10-31 02:39:22. Version ac07

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