Missouri S&T Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Missouri S&T Observatory clear sky chart from 2005-11-06 to 2024-04-25.

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	13% 7% 3 5% 5% 3 4 4 5% 7% 43%	83478
	Night	13% 8% 3 6% 4 3 4 4 4 6% 44%	85682
Transparency	Day	40% 6% 11% 24% 16% 3	83191
	Night	41% 5% 11% 24% 17% 3	85489
Seeing	Day	18% 11% 28% 25% 14% 4	14764
	Night	18% 12% 31% 27% 12% 1	24769

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	12% 13% 4 8% 6% 3 3 5% 4 5% 37%	2635
	11th to 20th	Day	12% 11% 4 8% 4 3 4 4 5% 6% 39%	2850
	21st to end	Day	21% 11% 5% 6% 4 2 3 4 4 5% 35%	3135
February	1st to 10th	Day	15% 11% 5% 7% 6% 3 5% 4 4 6% 35%	1710
	11th to 20th	Day	16% 9% 3 6% 4 3 4 5% 4 7% 39%	1764
	21st to end	Day	14% 11% 4 5% 6% 3 4 4 5% 6% 38%	1570
March	1st to 10th	Day	19% 10% 3 6% 4 2 3 3 3 4 42%	3358
	11th to 20th	Day	14% 7% 2 4 4 2 3 3 4 6% 51%	3480
	21st to end	Day	15% 9% 3 7% 6% 4 6% 5% 5% 6% 34%	3904
April	1st to 10th	Day	11% 7% 2 6% 5% 3 4 5% 5% 8% 45%	2280
	11th to 20th	Day	17% 8% 2 4 5% 3 4 5% 5% 7% 40%	2254
	21st to end	Day	21% 7% 3 5% 5% 3 5% 5% 5% 6% 35%	2209
May	1st to 10th	Day	18% 6% 3 5% 6% 3 5% 5% 5% 7% 36%	2207
	11th to 20th	Day	16% 6% 2 4 5% 4 4 5% 6% 7% 42%	2397
	21st to end	Day	12% 5% 2 7% 7% 4 7% 6% 7% 9% 35%	2725
June	1st to 10th	Day	9% 5% 2 5% 6% 3 5% 6% 6% 9% 44%	2520
	11th to 20th	Day	8% 4 1 4 4 3 5% 6% 6% 10% 49%	2520
	21st to end	Day	6% 2 2 4 5% 3 5% 6% 7% 10% 51%	2520
July	1st to 10th	Day	10% 5% 2 5% 5% 4 5% 6% 7% 10% 42%	2520
	11th to 20th	Day	4 3 1 4 5% 3 5% 6% 7% 9% 50%	2418
	21st to end	Day	9% 5% 2 6% 7% 4 5% 5% 6% 9% 41%	2546
August	1st to 10th	Day	8% 5% 2 6% 6% 3 6% 6% 8% 11% 41%	2328
	11th to 20th	Day	9% 4 3 5% 6% 3 6% 6% 6% 10% 41%	2176
	21st to end	Day	9% 5% 2 4 4 3 4 5% 6% 9% 49%	2376
September	1st to 10th	Day	13% 5% 1 5% 4 3 4 4 4 8% 48%	2160
	11th to 20th	Day	11% 5% 2 4 5% 3 4 5% 4 6% 51%	2160
	21st to end	Day	8% 5% 2 4 4 2 4 4 5% 7% 53%	1908
October	1st to 10th	Day	11% 5% 2 5% 4 3 3 4 4 6% 55%	1800
	11th to 20th	Day	15% 7% 2 4 4 2 3 3 3 4 53%	1800
	21st to end	Day	18% 9% 3 4 4 2 3 3 4 5% 46%	1980
November	1st to 10th	Day	12% 5% 2 4 3 2 4 4 4 5% 54%	1763
	11th to 20th	Day	15% 7% 2 5% 5% 2 4 3 4 6% 48%	1710
	21st to end	Day	15% 10% 4 4 3 2 3 4 4 6% 45%	1574
December	1st to 10th	Day	14% 10% 3 6% 5% 3 4 3 5% 6% 42%	1520
	11th to 20th	Day	13% 10% 6% 7% 5% 3 3 3 4 6% 40%	1918
	21st to end	Day	15% 16% 5% 8% 6% 3 4 4 4 5% 29%	2783
January	1st to 10th	Night	13% 11% 5% 10% 5% 3 4 4 4 5% 37%	4304
	11th to 20th	Night	13% 9% 4 10% 7% 4 7% 5% 4 4 33%	4120
	21st to end	Night	22% 14% 6% 6% 5% 2 3 3 3 4 33%	4532
February	1st to 10th	Night	16% 10% 5% 7% 5% 3 3 4 5% 5% 37%	2470
	11th to 20th	Night	14% 8% 4 7% 5% 3 4 3 4 6% 43%	2302
	21st to end	Night	15% 10% 3 8% 5% 3 4 4 4 5% 41%	1884
March	1st to 10th	Night	19% 11% 2 5% 3 2 2 3 3 5% 45%	3524
	11th to 20th	Night	14% 6% 3 4 4 2 3 4 5% 6% 49%	3480
	21st to end	Night	17% 11% 4 7% 6% 3 6% 5% 4 6% 32%	3727
April	1st to 10th	Night	11% 5% 2 4 5% 3 4 4 5% 8% 49%	1900
	11th to 20th	Night	15% 7% 3 5% 3 2 4 4 4 6% 47%	1875
	21st to end	Night	19% 6% 3 5% 6% 3 4 4 5% 6% 39%	1850
May	1st to 10th	Night	16% 5% 3 5% 4 2 4 3 5% 8% 44%	1749
	11th to 20th	Night	16% 7% 2 6% 3 2 3 3 4 7% 47%	1495
	21st to end	Night	10% 6% 3 5% 7% 4 5% 6% 6% 7% 40%	1551
June	1st to 10th	Night	8% 4 2 4 4 3 4 5% 5% 8% 52%	1440
	11th to 20th	Night	6% 3 2 3 3 2 4 5% 7% 12% 54%	1440
	21st to end	Night	4 2 2 3 3 3 4 5% 6% 9% 60%	1440
July	1st to 10th	Night	9% 3 1 4 4 3 5% 5% 6% 9% 50%	1440
	11th to 20th	Night	4 3 2 4 3 3 4 4 7% 10% 58%	1538
	21st to end	Night	6% 4 2 4 5% 3 5% 4 7% 9% 51%	1772
August	1st to 10th	Night	6% 4 2 4 4 3 5% 5% 7% 10% 51%	1611
	11th to 20th	Night	6% 4 2 4 3 3 4 4 6% 9% 55%	1725
	21st to end	Night	6% 3 2 4 4 3 3 4 5% 9% 57%	1980
September	1st to 10th	Night	12% 4 3 4 4 2 3 4 5% 7% 53%	1800
	11th to 20th	Night	9% 6% 2 4 4 2 4 5% 4 8% 53%	1800
	21st to end	Night	9% 4 2 3 4 2 4 4 4 6% 58%	2030
October	1st to 10th	Night	8% 4 1 4 3 2 3 4 4 8% 59%	2160
	11th to 20th	Night	15% 6% 2 4 4 2 3 3 4 6% 52%	2160
	21st to end	Night	20% 6% 2 4 4 2 3 3 3 5% 48%	2376
November	1st to 10th	Night	11% 5% 2 4 3 2 3 3 4 6% 56%	2311
	11th to 20th	Night	14% 6% 3 5% 4 2 3 3 4 7% 49%	2470
	21st to end	Night	16% 10% 3 5% 3 3 3 3 4 5% 46%	2603
December	1st to 10th	Night	15% 10% 4 6% 5% 3 4 4 5% 7% 38%	2660
	11th to 20th	Night	14% 10% 5% 7% 4 3 4 3 4 5% 41%	3279
	21st to end	Night	15% 18% 6% 9% 6% 3 5% 5% 4 4 25%	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	48% 5% 8% 24% 13% 1	2636
	11th to 20th	Day	47% 3 10% 24% 15% 1	2850
	21st to end	Day	52% 3 9% 16% 15% 4	3135
February	1st to 10th	Day	52% 4 10% 21% 12% 1	1710
	11th to 20th	Day	46% 4 12% 20% 15% 4	1773
	21st to end	Day	48% 4 6% 23% 14% 5%	1570
March	1st to 10th	Day	48% 3 7% 20% 15% 7%	3358
	11th to 20th	Day	36% 4 10% 28% 15% 7%	3480
	21st to end	Day	48% 8% 15% 20% 9% 1	3904
April	1st to 10th	Day	38% 5% 13% 24% 19% 2	2280
	11th to 20th	Day	44% 4 11% 22% 15% 3	2254
	21st to end	Day	49% 6% 11% 20% 13% 1	2209
May	1st to 10th	Day	47% 7% 12% 22% 11% 1	2207
	11th to 20th	Day	40% 8% 13% 23% 14% 2	2401
	21st to end	Day	43% 9% 13% 21% 13% 1	2725
June	1st to 10th	Day	35% 7% 14% 27% 15% 1	2520
	11th to 20th	Day	29% 8% 13% 29% 18% 4	2520
	21st to end	Day	26% 8% 17% 28% 16% 5%	2520
July	1st to 10th	Day	35% 8% 16% 25% 12% 3	2451
	11th to 20th	Day	27% 9% 16% 26% 18% 4	2344
	21st to end	Day	37% 7% 13% 29% 11% 1	2405
August	1st to 10th	Day	35% 9% 17% 23% 15% 1	2314
	11th to 20th	Day	36% 10% 11% 27% 14% 1	2176
	21st to end	Day	31% 6% 13% 25% 18% 6%	2376
September	1st to 10th	Day	35% 6% 12% 27% 17% 4	2160
	11th to 20th	Day	34% 4 8% 25% 27% 2	2160
	21st to end	Day	30% 5% 9% 28% 25% 3	1908
October	1st to 10th	Day	32% 4 10% 25% 26% 3	1800
	11th to 20th	Day	35% 4 7% 27% 21% 6%	1800
	21st to end	Day	42% 4 8% 25% 18% 4	1980
November	1st to 10th	Day	33% 5% 10% 23% 23% 6%	1763
	11th to 20th	Day	38% 3 8% 23% 21% 5%	1710
	21st to end	Day	43% 4 8% 27% 17% 1	1574
December	1st to 10th	Day	45% 4 10% 27% 13% 2	1520
	11th to 20th	Day	46% 4 9% 19% 20% 1	1915
	21st to end	Day	57% 6% 9% 16% 11% 2	2783
January	1st to 10th	Night	51% 4 10% 21% 13% 1	4304
	11th to 20th	Night	55% 4 8% 21% 10% 2	4120
	21st to end	Night	56% 3 9% 20% 10% 1	4532
February	1st to 10th	Night	50% 4 9% 21% 14% 2	2470
	11th to 20th	Night	43% 3 11% 22% 17% 3	2303
	21st to end	Night	46% 5% 8% 21% 15% 4	1884
March	1st to 10th	Night	45% 3 8% 23% 16% 5%	3524
	11th to 20th	Night	36% 5% 10% 25% 20% 4	3480
	21st to end	Night	52% 7% 11% 22% 8%	3727
April	1st to 10th	Night	33% 5% 12% 27% 20% 3	1900
	11th to 20th	Night	38% 5% 11% 24% 17% 5%	1875
	21st to end	Night	45% 5% 8% 24% 16% 1	1850
May	1st to 10th	Night	39% 7% 13% 23% 18% 1	1749
	11th to 20th	Night	39% 5% 14% 22% 18% 2	1496
	21st to end	Night	41% 7% 15% 21% 14% 2	1552
June	1st to 10th	Night	29% 6% 17% 27% 18% 2	1440
	11th to 20th	Night	23% 7% 13% 31% 22% 4	1440
	21st to end	Night	19% 6% 20% 29% 20% 6%	1440
July	1st to 10th	Night	29% 9% 15% 27% 16% 4	1400
	11th to 20th	Night	21% 6% 16% 30% 23% 4	1489
	21st to end	Night	28% 7% 13% 34% 16% 1	1673
August	1st to 10th	Night	26% 9% 16% 32% 15% 2	1601
	11th to 20th	Night	25% 6% 15% 33% 19% 1	1725
	21st to end	Night	25% 5% 16% 27% 22% 5%	1980
September	1st to 10th	Night	32% 4 11% 27% 22% 6%	1800
	11th to 20th	Night	31% 5% 11% 24% 28% 3	1800
	21st to end	Night	28% 5% 10% 25% 29% 4	2030
October	1st to 10th	Night	24% 5% 11% 28% 27% 5%	2160
	11th to 20th	Night	35% 3 7% 26% 23% 5%	2160
	21st to end	Night	41% 3 7% 22% 22% 5%	2376
November	1st to 10th	Night	30% 4 10% 28% 21% 6%	2311
	11th to 20th	Night	37% 3 7% 24% 24% 5%	2470
	21st to end	Night	42% 4 9% 25% 18% 2	2603
December	1st to 10th	Night	46% 4 10% 23% 15% 2	2660
	11th to 20th	Night	47% 3 9% 25% 16% 1	3281
	21st to end	Night	62% 5% 8% 14% 8% 2	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	25% 22% 38% 13% 2	270
	11th to 20th	Day	33% 22% 34% 11%	270
	21st to end	Day	24% 25% 35% 14% 2	297
February	1st to 10th	Day	28% 21% 36% 14% 2	270
	11th to 20th	Day	29% 28% 29% 11% 3	270
	21st to end	Day	31% 20% 39% 9%	225
March	1st to 10th	Day	25% 22% 43% 9% 1	270
	11th to 20th	Day	32% 20% 35% 10% 2 1	270
	21st to end	Day	36% 19% 33% 11% 1	349
April	1st to 10th	Day	23% 17% 37% 18% 5%	460
	11th to 20th	Day	28% 17% 32% 17% 6%	452
	21st to end	Day	24% 17% 34% 19% 5%	437
May	1st to 10th	Day	23% 14% 37% 20% 6% 1	470
	11th to 20th	Day	20% 14% 27% 24% 12% 2	625
	21st to end	Day	13% 10% 32% 25% 14% 5%	679
June	1st to 10th	Day	10% 5% 23% 32% 24% 6%	630
	11th to 20th	Day	8% 3 26% 37% 22% 3	630
	21st to end	Day	7% 7% 30% 35% 17% 5%	630
July	1st to 10th	Day	12% 3 15% 28% 30% 11%	621
	11th to 20th	Day	5% 3 22% 37% 27% 6%	618
	21st to end	Day	11% 3 16% 36% 26% 8%	684
August	1st to 10th	Day	11% 2 14% 44% 24% 5%	626
	11th to 20th	Day	10% 4 16% 37% 24% 9%	490
	21st to end	Day	13% 1 15% 31% 30% 9%	495
September	1st to 10th	Day	14% 4 14% 35% 27% 6%	450
	11th to 20th	Day	9% 1 22% 33% 24% 11%	450
	21st to end	Day	10% 6% 26% 35% 18% 4	342
October	1st to 10th	Day	18% 10% 31% 28% 11% 2	270
	11th to 20th	Day	24% 13% 39% 18% 6%	270
	21st to end	Day	35% 16% 30% 16% 3	297
November	1st to 10th	Day	17% 15% 40% 19% 7% 3	270
	11th to 20th	Day	24% 18% 36% 17% 5% 1	270
	21st to end	Day	30% 15% 33% 16% 6%	270
December	1st to 10th	Day	18% 27% 32% 14% 7% 2	270
	11th to 20th	Day	25% 19% 37% 16% 2 1	270
	21st to end	Day	26% 27% 34% 11% 2	297
January	1st to 10th	Night	21% 21% 37% 18% 4	950
	11th to 20th	Night	23% 24% 34% 16% 3	950
	21st to end	Night	22% 20% 37% 20% 1	1045
February	1st to 10th	Night	23% 19% 38% 17% 2	950
	11th to 20th	Night	22% 18% 43% 16% 2	827
	21st to end	Night	25% 23% 34% 16% 2	628
March	1st to 10th	Night	24% 15% 40% 19% 2	641
	11th to 20th	Night	24% 13% 37% 23% 4	570
	21st to end	Night	27% 16% 34% 18% 4	627
April	1st to 10th	Night	16% 17% 40% 24% 3	570
	11th to 20th	Night	20% 15% 34% 26% 4 1	563
	21st to end	Night	23% 12% 36% 22% 7%	555
May	1st to 10th	Night	19% 7% 34% 31% 9%	540
	11th to 20th	Night	19% 6% 31% 28% 16% 1	531
	21st to end	Night	12% 6% 30% 31% 18% 3	584
June	1st to 10th	Night	10% 4 18% 38% 29% 2	540
	11th to 20th	Night	7% 2 26% 40% 23% 2	540
	21st to end	Night	4 2 26% 47% 18% 2	540
July	1st to 10th	Night	11% 1 12% 36% 33% 7%	525
	11th to 20th	Night	5% 1 18% 41% 31% 4	522
	21st to end	Night	6% 2 17% 41% 32% 2	591
August	1st to 10th	Night	7% 2 16% 44% 29% 2	537
	11th to 20th	Night	8% 2 14% 42% 31% 2	534
	21st to end	Night	6% 2 15% 36% 36% 5%	594
September	1st to 10th	Night	14% 3 15% 39% 27% 4	540
	11th to 20th	Night	11% 3 14% 40% 26% 5%	540
	21st to end	Night	11% 5% 27% 31% 23% 4	665
October	1st to 10th	Night	10% 6% 30% 29% 23% 3	720
	11th to 20th	Night	18% 12% 35% 25% 9% 1	720
	21st to end	Night	25% 13% 32% 24% 6%	792
November	1st to 10th	Night	14% 12% 39% 27% 8%	740
	11th to 20th	Night	20% 15% 34% 24% 7%	760
	21st to end	Night	23% 16% 34% 22% 5%	893
December	1st to 10th	Night	24% 15% 35% 21% 4	950
	11th to 20th	Night	23% 15% 35% 22% 4	950
	21st to end	Night	26% 18% 36% 18% 2	1045

Page generated at 2024-04-22 08:25:43. Version ac07

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