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 2024-11-05.

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% 7% 3 6% 4 4 4 4 5% 7% 43%	101172
	Night	13% 8% 3 6% 4 3 4 3 5% 7% 45%	97945
Transparency	Day	39% 5% 11% 25% 17% 3	104809
	Night	39% 5% 11% 24% 18% 3	102448
Seeing	Day	18% 11% 28% 25% 14% 4	15595
	Night	18% 12% 31% 27% 12% 1	25394

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 10% 4 4 4 3 4 5% 37%	2635
	11th to 20th	Day	12% 12% 4 8% 4 4 4 2 5% 6% 39%	2850
	21st to end	Day	21% 12% 5% 6% 4 3 3 3 4 5% 35%	3135
February	1st to 10th	Day	15% 13% 4 8% 5% 4 4 3 4 6% 34%	1710
	11th to 20th	Day	16% 9% 2 6% 4 4 5% 3 5% 6% 39%	1764
	21st to end	Day	14% 12% 3 7% 4 4 4 3 6% 6% 38%	1570
March	1st to 10th	Day	18% 11% 3 7% 4 3 3 2 3 4 42%	3358
	11th to 20th	Day	14% 7% 2 5% 3 3 3 2 4 6% 51%	3480
	21st to end	Day	15% 10% 3 8% 5% 5% 5% 4 5% 6% 34%	3904
April	1st to 10th	Day	11% 7% 2 7% 4 4 4 3 6% 7% 45%	2280
	11th to 20th	Day	17% 8% 2 5% 4 4 4 4 5% 6% 40%	2254
	21st to end	Day	20% 8% 3 6% 4 4 5% 3 5% 6% 34%	2280
May	1st to 10th	Day	15% 8% 3 7% 5% 6% 6% 4 7% 8% 33%	3854
	11th to 20th	Day	16% 7% 3 6% 4 5% 4 3 5% 7% 39%	4261
	21st to end	Day	12% 6% 2 7% 5% 4 5% 3 6% 7% 42%	4824
June	1st to 10th	Day	9% 5% 2 7% 5% 4 5% 5% 7% 9% 43%	2660
	11th to 20th	Day	7% 4 1 4 4 4 4 5% 7% 10% 50%	2660
	21st to end	Day	6% 3 2 4 4 4 5% 5% 8% 9% 50%	2660
July	1st to 10th	Day	13% 6% 3 6% 4 5% 4 4 6% 9% 40%	4440
	11th to 20th	Day	4 4 2 6% 5% 4 5% 4 7% 11% 48%	4254
	21st to end	Day	7% 5% 3 8% 6% 6% 5% 5% 9% 10% 37%	4465
August	1st to 10th	Day	5% 4 1 5% 4 3 5% 4 7% 11% 51%	4104
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	3819
	21st to end	Day	7% 4 2 5% 4 4 4 3 6% 9% 51%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 4 8% 49%	2280
	11th to 20th	Day	11% 6% 2 5% 4 4 4 3 4 6% 50%	2280
	21st to end	Day	9% 6% 2 5% 4 4 4 3 5% 7% 51%	2013
October	1st to 10th	Day	10% 5% 1 5% 3 3 3 3 4 6% 57%	1900
	11th to 20th	Day	14% 7% 2 4 3 2 3 2 3 4 55%	1900
	21st to end	Day	17% 9% 2 4 3 3 3 2 4 5% 46%	2090
November	1st to 10th	Day	12% 6% 2 5% 3 3 4 3 4 5% 54%	1803
	11th to 20th	Day	14% 7% 2 6% 4 4 3 2 4 6% 48%	1710
	21st to end	Day	14% 11% 3 5% 3 3 3 4 4 5% 45%	1574
December	1st to 10th	Day	14% 11% 2 7% 4 4 4 3 5% 6% 41%	1520
	11th to 20th	Day	13% 10% 6% 7% 4 4 3 3 4 6% 39%	1918
	21st to end	Day	15% 16% 5% 9% 5% 4 4 3 4 5% 28%	2783
January	1st to 10th	Night	13% 11% 5% 10% 4 4 4 3 4 5% 36%	4304
	11th to 20th	Night	13% 9% 4 12% 6% 5% 7% 4 4 4 33%	4120
	21st to end	Night	22% 14% 5% 7% 4 2 3 2 4 4 33%	4532
February	1st to 10th	Night	16% 11% 4 8% 4 3 3 4 5% 5% 37%	2470
	11th to 20th	Night	14% 8% 4 7% 4 3 3 3 5% 6% 43%	2302
	21st to end	Night	15% 10% 3 9% 4 4 3 3 4 5% 40%	1884
March	1st to 10th	Night	19% 11% 2 6% 3 2 2 2 3 5% 45%	3524
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 49%	3480
	21st to end	Night	17% 12% 4 8% 5% 5% 5% 4 5% 6% 32%	3727
April	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 5% 8% 49%	1900
	11th to 20th	Night	15% 8% 2 6% 3 2 4 3 5% 6% 46%	1875
	21st to end	Night	19% 6% 3 6% 5% 3 4 4 5% 6% 39%	1900
May	1st to 10th	Night	17% 7% 3 6% 3 3 3 3 5% 8% 41%	3040
	11th to 20th	Night	13% 9% 2 6% 4 3 4 3 5% 8% 43%	2641
	21st to end	Night	11% 7% 2 7% 5% 5% 5% 4 6% 7% 39%	2743
June	1st to 10th	Night	8% 5% 2 5% 4 4 4 4 5% 8% 51%	1520
	11th to 20th	Night	5% 3 1 4 3 2 5% 4 7% 11% 54%	1520
	21st to end	Night	4 2 1 3 3 4 3 5% 6% 9% 59%	1520
July	1st to 10th	Night	12% 5% 2 6% 3 5% 5% 4 6% 9% 45%	2530
	11th to 20th	Night	4 3 2 4 3 3 4 3 6% 9% 60%	2712
	21st to end	Night	6% 6% 2 6% 5% 4 6% 4 7% 9% 45%	3098
August	1st to 10th	Night	4 3 2 4 3 3 3 3 6% 8% 60%	2836
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 5% 8% 49%	3013
	21st to end	Night	5% 3 1 4 3 3 3 3 5% 9% 59%	3476
September	1st to 10th	Night	12% 4 2 5% 4 2 3 3 5% 7% 54%	1900
	11th to 20th	Night	9% 6% 2 4 4 4 4 4 4 8% 52%	1900
	21st to end	Night	9% 5% 2 4 4 3 4 3 4 6% 56%	2143
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 4 8% 61%	2280
	11th to 20th	Night	14% 6% 2 4 3 3 3 2 4 6% 53%	2280
	21st to end	Night	19% 7% 2 4 3 3 3 2 4 5% 48%	2508
November	1st to 10th	Night	11% 6% 2 5% 2 3 3 3 4 6% 56%	2371
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 5% 7% 49%	2470
	21st to end	Night	16% 11% 2 5% 3 3 2 3 4 5% 46%	2603
December	1st to 10th	Night	15% 11% 3 7% 4 3 4 3 5% 7% 38%	2660
	11th to 20th	Night	14% 11% 5% 8% 4 3 3 3 4 5% 41%	3279
	21st to end	Night	15% 18% 6% 10% 5% 5% 4 4 4 5% 24%	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	50% 6% 11% 20% 13% 1	2280
May	1st to 10th	Day	45% 9% 12% 20% 13% 1	3889
	11th to 20th	Day	44% 7% 10% 24% 13% 1	4265
	21st to end	Day	39% 7% 10% 25% 19% 1	4837
June	1st to 10th	Day	35% 7% 15% 26% 15% 1	2660
	11th to 20th	Day	28% 8% 12% 31% 18% 3	2660
	21st to end	Day	26% 8% 17% 27% 16% 5%	2660
July	1st to 10th	Day	40% 6% 13% 27% 13% 2	4371
	11th to 20th	Day	29% 7% 14% 33% 15% 2	4180
	21st to end	Day	38% 6% 19% 27% 8% 1	4325
August	1st to 10th	Day	26% 6% 18% 33% 17%	4090
	11th to 20th	Day	38% 6% 12% 25% 17% 1	3857
	21st to end	Day	30% 4 15% 36% 12% 3	4179
September	1st to 10th	Day	34% 5% 12% 26% 19% 5%	2280
	11th to 20th	Day	35% 4 8% 25% 26% 2	2280
	21st to end	Day	32% 5% 8% 27% 24% 3	2013
October	1st to 10th	Day	18% 2 6% 20% 42% 12%	3160
	11th to 20th	Day	23% 2 5% 23% 35% 12%	3140
	21st to end	Day	31% 3 7% 30% 26% 3	3428
November	1st to 10th	Day	34% 5% 10% 23% 23% 6%	1803
	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	46% 5% 9% 24% 16% 1	1900
May	1st to 10th	Night	40% 8% 15% 21% 14% 2	3070
	11th to 20th	Night	40% 7% 13% 25% 14% 1	2642
	21st to end	Night	41% 7% 13% 23% 14% 1	2751
June	1st to 10th	Night	30% 6% 17% 26% 18% 3	1520
	11th to 20th	Night	22% 7% 13% 31% 23% 4	1520
	21st to end	Night	19% 6% 20% 29% 19% 7%	1520
July	1st to 10th	Night	36% 7% 12% 26% 16% 3	2490
	11th to 20th	Night	22% 4 11% 41% 19% 2	2663
	21st to end	Night	34% 5% 19% 29% 12% 1	2999
August	1st to 10th	Night	21% 6% 18% 31% 22% 1	2826
	11th to 20th	Night	34% 5% 16% 27% 16% 2	3041
	21st to end	Night	23% 4 16% 38% 16% 3	3476
September	1st to 10th	Night	31% 4 10% 26% 23% 6%	1900
	11th to 20th	Night	32% 4 10% 23% 28% 3	1900
	21st to end	Night	30% 5% 9% 25% 28% 3	2143
October	1st to 10th	Night	14% 3 7% 18% 48% 11%	3800
	11th to 20th	Night	23% 2 6% 21% 32% 15%	3779
	21st to end	Night	33% 3 6% 27% 27% 3	4120
November	1st to 10th	Night	31% 4 10% 28% 21% 6%	2371
	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	25% 18% 34% 18% 5% 1	460
May	1st to 10th	Day	22% 15% 37% 20% 5% 1	513
	11th to 20th	Day	20% 14% 27% 24% 13% 3	675
	21st to end	Day	13% 11% 33% 25% 13% 5%	734
June	1st to 10th	Day	11% 5% 25% 32% 22% 6%	680
	11th to 20th	Day	8% 4 25% 38% 23% 3	680
	21st to end	Day	7% 7% 31% 35% 16% 5%	680
July	1st to 10th	Day	13% 4 17% 28% 28% 10%	671
	11th to 20th	Day	5% 3 23% 37% 26% 6%	668
	21st to end	Day	11% 3 16% 36% 26% 8%	739
August	1st to 10th	Day	11% 2 16% 43% 23% 5%	676
	11th to 20th	Day	11% 5% 18% 36% 22% 8%	533
	21st to end	Day	13% 1 15% 31% 31% 9%	539
September	1st to 10th	Day	13% 3 15% 36% 27% 6%	490
	11th to 20th	Day	11% 1 21% 32% 24% 10%	490
	21st to end	Day	11% 6% 27% 34% 17% 4	375
October	1st to 10th	Day	16% 9% 30% 29% 13% 3	300
	11th to 20th	Day	22% 13% 37% 21% 7%	300
	21st to end	Day	32% 16% 32% 17% 3	330
November	1st to 10th	Day	18% 15% 38% 20% 6% 2	282
	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% 21% 7%	570
May	1st to 10th	Night	19% 7% 34% 31% 8%	570
	11th to 20th	Night	19% 6% 30% 29% 16% 1	561
	21st to end	Night	13% 6% 31% 31% 18% 3	617
June	1st to 10th	Night	11% 4 19% 37% 27% 2	570
	11th to 20th	Night	7% 2 26% 41% 23% 2	570
	21st to end	Night	4 2 26% 48% 18% 2	570
July	1st to 10th	Night	12% 1 13% 36% 32% 6%	555
	11th to 20th	Night	5% 1 18% 42% 31% 3	552
	21st to end	Night	6% 2 17% 42% 31% 2	624
August	1st to 10th	Night	7% 2 16% 44% 30% 2	567
	11th to 20th	Night	8% 2 16% 42% 30% 2	564
	21st to end	Night	7% 2 15% 36% 36% 4	627
September	1st to 10th	Night	13% 2 15% 39% 27% 4	570
	11th to 20th	Night	11% 3 15% 41% 26% 5%	570
	21st to end	Night	12% 5% 27% 31% 22% 4	702
October	1st to 10th	Night	9% 5% 28% 30% 24% 3	760
	11th to 20th	Night	18% 11% 34% 26% 10% 1	760
	21st to end	Night	24% 12% 33% 24% 6%	836
November	1st to 10th	Night	14% 11% 39% 27% 8%	760
	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 2024-11-03 01:11:22. Version ac07

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