Munson Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Munson Observing Site clear sky chart from 2005-11-06 to 2024-11-12.

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	10% 6% 2 7% 5% 5% 5% 5% 6% 8% 40%	100766
	Night	10% 6% 2 6% 4 4 4 4 6% 9% 44%	98394
Transparency	Day	38% 7% 12% 18% 17% 8%	104682
	Night	35% 7% 13% 17% 19% 9%	102616
Seeing	Day	13% 10% 22% 24% 19% 11%	14624
	Night	13% 8% 22% 29% 23% 6%	24553

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	14% 7% 2 5% 4 4 4 4 4 8% 45%	2872
	11th to 20th	Day	11% 4 1 4 3 3 4 4 5% 7% 54%	3160
	21st to end	Day	24% 7% 2 5% 3 4 3 3 4 6% 38%	3476
February	1st to 10th	Day	17% 6% 3 7% 5% 4 4 4 4 6% 41%	1900
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 44%	1848
	21st to end	Day	14% 7% 2 7% 5% 5% 6% 4 5% 7% 38%	1570
March	1st to 10th	Day	18% 9% 3 7% 4 4 5% 4 5% 7% 34%	3120
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 6% 8% 43%	3342
	21st to end	Day	13% 6% 2 7% 4 4 5% 3 6% 7% 43%	3995
April	1st to 10th	Day	11% 7% 3 6% 5% 3 4 4 5% 7% 46%	2280
	11th to 20th	Day	12% 5% 2 7% 5% 5% 4 4 4 7% 44%	2254
	21st to end	Day	7% 5% 2 5% 5% 5% 4 4 5% 7% 53%	2280
May	1st to 10th	Day	8% 5% 2 6% 5% 5% 4 5% 6% 9% 45%	3847
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 4 6% 8% 40%	4081
	21st to end	Day	5% 4 2 6% 6% 6% 6% 4 7% 10% 45%	4476
June	1st to 10th	Day	8% 7% 3 8% 7% 7% 7% 6% 8% 10% 29%	2470
	11th to 20th	Day	5% 4 1 7% 7% 6% 7% 6% 10% 11% 35%	2470
	21st to end	Day	6% 5% 2 9% 7% 8% 9% 7% 9% 10% 29%	2470
July	1st to 10th	Day	7% 7% 3 10% 7% 9% 9% 7% 10% 11% 20%	4120
	11th to 20th	Day	4 5% 3 8% 8% 8% 8% 6% 10% 12% 28%	4066
	21st to end	Day	5% 6% 2 10% 8% 9% 9% 7% 10% 13% 20%	4118
August	1st to 10th	Day	4 4 1 6% 5% 7% 7% 6% 10% 13% 38%	3785
	11th to 20th	Day	5% 5% 1 6% 5% 6% 6% 4 7% 10% 44%	3729
	21st to end	Day	7% 5% 2 8% 7% 7% 7% 6% 8% 10% 34%	4180
September	1st to 10th	Day	10% 6% 3 9% 6% 7% 7% 6% 7% 8% 31%	2217
	11th to 20th	Day	12% 7% 3 9% 6% 5% 6% 4 6% 7% 35%	2090
	21st to end	Day	8% 5% 2 5% 5% 5% 6% 4 5% 7% 48%	2090
October	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 5% 6% 53%	2090
	11th to 20th	Day	9% 4 1 4 3 3 3 3 5% 7% 57%	2090
	21st to end	Day	9% 5% 2 6% 4 4 4 3 4 5% 56%	2102
November	1st to 10th	Day	8% 6% 2 3 3 4 4 3 6% 7% 54%	1762
	11th to 20th	Day	9% 4 2 4 4 4 3 3 5% 7% 53%	1719
	21st to end	Day	12% 5% 2 6% 4 4 4 4 5% 7% 47%	1710
December	1st to 10th	Day	13% 6% 3 6% 4 3 4 4 5% 7% 46%	1710
	11th to 20th	Day	14% 10% 3 8% 4 4 4 3 4 5% 42%	2153
	21st to end	Day	19% 8% 3 6% 4 3 4 3 4 5% 41%	3124
January	1st to 10th	Night	17% 5% 2 6% 4 4 5% 3 5% 6% 44%	4068
	11th to 20th	Night	11% 8% 2 6% 4 3 3 3 5% 6% 49%	3800
	21st to end	Night	23% 9% 3 5% 3 3 3 2 4 5% 40%	4180
February	1st to 10th	Night	14% 8% 2 6% 4 4 3 4 5% 6% 44%	2280
	11th to 20th	Night	17% 9% 2 5% 3 3 3 2 4 5% 45%	2218
	21st to end	Night	15% 10% 3 6% 5% 4 4 3 5% 5% 41%	1884
March	1st to 10th	Night	22% 13% 4 7% 4 4 3 3 4 5% 32%	3733
	11th to 20th	Night	10% 8% 2 6% 4 4 5% 4 6% 9% 43%	3618
	21st to end	Night	13% 8% 2 7% 4 3 3 3 4 7% 45%	3663
April	1st to 10th	Night	12% 7% 2 6% 5% 4 4 4 6% 7% 45%	1900
	11th to 20th	Night	13% 5% 3 6% 2 3 4 4 5% 7% 47%	1875
	21st to end	Night	5% 4 1 4 4 3 3 3 5% 7% 60%	1900
May	1st to 10th	Night	9% 7% 2 7% 4 5% 4 4 6% 9% 42%	3044
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 3 6% 8% 42%	2812
	21st to end	Night	4 5% 2 5% 4 3 5% 3 7% 12% 50%	3079
June	1st to 10th	Night	8% 5% 2 7% 4 5% 5% 5% 9% 12% 39%	1710
	11th to 20th	Night	4 4 1 5% 4 4 6% 7% 10% 12% 43%	1710
	21st to end	Night	4 4 2 7% 6% 6% 6% 6% 8% 14% 37%	1710
July	1st to 10th	Night	5% 5% 2 6% 6% 6% 7% 7% 11% 17% 28%	2840
	11th to 20th	Night	3 4 2 5% 4 4 6% 5% 10% 15% 42%	2889
	21st to end	Night	3 3 2 7% 6% 6% 8% 8% 12% 15% 30%	3435
August	1st to 10th	Night	4 3 2 4 4 5% 6% 6% 9% 13% 45%	3144
	11th to 20th	Night	3 3 1 6% 4 5% 5% 5% 7% 13% 48%	3100
	21st to end	Night	4 6% 2 7% 6% 7% 7% 6% 9% 11% 36%	3476
September	1st to 10th	Night	9% 6% 2 7% 5% 5% 6% 5% 8% 11% 36%	1943
	11th to 20th	Night	11% 5% 3 7% 4 4 5% 5% 6% 9% 41%	2090
	21st to end	Night	8% 5% 1 6% 5% 4 4 4 6% 7% 50%	2090
October	1st to 10th	Night	7% 5% 2 5% 3 3 4 4 7% 8% 53%	2090
	11th to 20th	Night	6% 5% 2 4 2 2 3 3 5% 6% 63%	2090
	21st to end	Night	9% 5% 2 4 3 3 3 3 4 6% 57%	2489
November	1st to 10th	Night	9% 4 1 5% 3 2 4 3 5% 7% 57%	2536
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 4 6% 54%	2484
	21st to end	Night	12% 6% 2 5% 3 4 4 4 5% 6% 49%	2470
December	1st to 10th	Night	13% 6% 2 6% 5% 4 3 3 5% 7% 46%	2470
	11th to 20th	Night	15% 8% 2 5% 4 4 3 3 5% 6% 44%	3042
	21st to end	Night	16% 10% 3 7% 4 4 3 3 4 5% 41%	4532

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	38% 4 5% 18% 23% 12%	2873
	11th to 20th	Day	29% 4 7% 18% 30% 11%	3160
	21st to end	Day	47% 4 5% 13% 20% 11%	3476
February	1st to 10th	Day	44% 3 7% 16% 20% 10%	1900
	11th to 20th	Day	40% 4 5% 17% 22% 12%	1858
	21st to end	Day	44% 6% 7% 17% 16% 11%	1570
March	1st to 10th	Day	49% 4 7% 19% 14% 7%	3120
	11th to 20th	Day	38% 5% 11% 20% 18% 8%	3342
	21st to end	Day	40% 5% 11% 17% 18% 10%	3995
April	1st to 10th	Day	38% 5% 9% 16% 20% 12%	2280
	11th to 20th	Day	40% 4 8% 18% 20% 10%	2254
	21st to end	Day	30% 5% 10% 21% 24% 10%	2280
May	1st to 10th	Day	31% 6% 13% 25% 19% 5%	3882
	11th to 20th	Day	41% 6% 12% 22% 17% 2	4085
	21st to end	Day	31% 7% 13% 29% 17% 2	4489
June	1st to 10th	Day	46% 8% 15% 21% 8% 1	2470
	11th to 20th	Day	37% 11% 17% 22% 11% 2	2470
	21st to end	Day	43% 11% 19% 15% 10% 2	2470
July	1st to 10th	Day	48% 16% 24% 10% 2	4055
	11th to 20th	Day	40% 16% 30% 11% 2 1	3997
	21st to end	Day	48% 16% 21% 12% 3	3987
August	1st to 10th	Day	32% 10% 20% 22% 14% 2	3773
	11th to 20th	Day	33% 9% 19% 21% 18% 1	3765
	21st to end	Day	40% 12% 21% 15% 10% 1	4179
September	1st to 10th	Day	47% 9% 16% 13% 11% 5%	2217
	11th to 20th	Day	47% 7% 11% 15% 13% 6%	2090
	21st to end	Day	35% 6% 9% 19% 21% 10%	2090
October	1st to 10th	Day	33% 4 7% 12% 16% 29%	3480
	11th to 20th	Day	17% 3 5% 18% 22% 35%	3458
	21st to end	Day	21% 3 3 13% 38% 21%	3442
November	1st to 10th	Day	29% 4 9% 19% 23% 16%	1762
	11th to 20th	Day	30% 4 8% 17% 27% 15%	1719
	21st to end	Day	35% 4 7% 19% 22% 13%	1710
December	1st to 10th	Day	39% 4 11% 18% 20% 9%	1710
	11th to 20th	Day	45% 4 5% 16% 20% 10%	2150
	21st to end	Day	46% 3 4 19% 21% 7%	3124
January	1st to 10th	Night	41% 4 5% 10% 26% 14%	4068
	11th to 20th	Night	36% 3 5% 14% 29% 12%	3800
	21st to end	Night	48% 3 4 14% 23% 8%	4180
February	1st to 10th	Night	41% 3 6% 17% 21% 11%	2280
	11th to 20th	Night	42% 4 6% 13% 21% 15%	2219
	21st to end	Night	45% 5% 7% 15% 15% 13%	1884
March	1st to 10th	Night	55% 4 7% 14% 13% 7%	3733
	11th to 20th	Night	38% 5% 10% 17% 20% 9%	3618
	21st to end	Night	40% 4 10% 19% 17% 10%	3663
April	1st to 10th	Night	38% 5% 11% 13% 19% 13%	1900
	11th to 20th	Night	35% 5% 9% 20% 21% 10%	1875
	21st to end	Night	24% 4 11% 27% 24% 9%	1900
May	1st to 10th	Night	36% 7% 16% 19% 17% 5%	3074
	11th to 20th	Night	38% 7% 13% 23% 16% 2	2813
	21st to end	Night	25% 8% 17% 31% 16% 3	3087
June	1st to 10th	Night	35% 9% 21% 24% 10% 2	1710
	11th to 20th	Night	26% 12% 24% 23% 12% 2	1710
	21st to end	Night	32% 12% 26% 18% 9% 2	1710
July	1st to 10th	Night	36% 17% 31% 12% 3	2795
	11th to 20th	Night	26% 17% 43% 12% 2	2835
	21st to end	Night	35% 23% 27% 13% 2	3325
August	1st to 10th	Night	27% 12% 26% 23% 12% 1	3132
	11th to 20th	Night	24% 11% 25% 24% 15%	3130
	21st to end	Night	36% 13% 21% 18% 10% 2	3476
September	1st to 10th	Night	37% 11% 21% 15% 11% 4	1943
	11th to 20th	Night	38% 9% 17% 17% 15% 5%	2090
	21st to end	Night	30% 7% 13% 20% 20% 9%	2090
October	1st to 10th	Night	35% 5% 8% 12% 20% 21%	3480
	11th to 20th	Night	14% 2 5% 18% 28% 32%	3461
	21st to end	Night	20% 3 4 14% 41% 19%	4099
November	1st to 10th	Night	27% 4 8% 18% 25% 17%	2536
	11th to 20th	Night	31% 4 5% 17% 28% 14%	2484
	21st to end	Night	35% 4 9% 18% 20% 14%	2470
December	1st to 10th	Night	38% 4 9% 19% 23% 8%	2470
	11th to 20th	Night	41% 3 7% 13% 25% 11%	3044
	21st to end	Night	47% 3 6% 18% 21% 5%	4532

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	20% 21% 39% 16% 3 1	270
	11th to 20th	Day	17% 21% 33% 19% 9% 1	270
	21st to end	Day	25% 27% 37% 8% 3	297
February	1st to 10th	Day	25% 24% 30% 16% 4 1	270
	11th to 20th	Day	25% 23% 33% 17% 1	270
	21st to end	Day	18% 32% 35% 13% 1	225
March	1st to 10th	Day	17% 26% 39% 13% 5%	270
	11th to 20th	Day	20% 21% 32% 19% 7% 1	374
	21st to end	Day	18% 18% 33% 21% 10% 1	506
April	1st to 10th	Day	20% 16% 32% 20% 9% 3	460
	11th to 20th	Day	16% 16% 32% 22% 11% 2	452
	21st to end	Day	10% 14% 29% 28% 16% 4	460
May	1st to 10th	Day	11% 11% 25% 27% 19% 7%	463
	11th to 20th	Day	8% 5% 27% 29% 19% 13%	487
	21st to end	Day	8% 3 22% 32% 19% 17%	529
June	1st to 10th	Day	12% 2 15% 31% 24% 15%	490
	11th to 20th	Day	7% 5% 13% 31% 25% 19%	490
	21st to end	Day	8% 2 13% 26% 28% 24%	490
July	1st to 10th	Day	9% 3 7% 20% 33% 29%	485
	11th to 20th	Day	6% 2 4 20% 36% 31%	484
	21st to end	Day	6% 1 8% 20% 37% 27%	532
August	1st to 10th	Day	8% 5% 23% 31% 33%	486
	11th to 20th	Day	9% 2 4 19% 34% 31%	479
	21st to end	Day	11% 2 10% 27% 32% 18%	539
September	1st to 10th	Day	12% 3 11% 25% 29% 21%	490
	11th to 20th	Day	15% 6% 9% 31% 30% 10%	490
	21st to end	Day	10% 4 16% 29% 29% 12%	490
October	1st to 10th	Day	11% 5% 31% 29% 18% 5%	490
	11th to 20th	Day	10% 7% 23% 31% 22% 8%	490
	21st to end	Day	12% 11% 25% 33% 18% 2	416
November	1st to 10th	Day	14% 9% 28% 32% 14% 2	300
	11th to 20th	Day	12% 15% 36% 28% 8% 1	273
	21st to end	Day	15% 15% 37% 23% 10% 1	270
December	1st to 10th	Day	16% 20% 33% 21% 8% 1	270
	11th to 20th	Day	24% 16% 37% 18% 5%	270
	21st to end	Day	26% 15% 34% 17% 7% 1	297
January	1st to 10th	Night	18% 16% 33% 26% 6%	760
	11th to 20th	Night	17% 16% 27% 31% 9%	760
	21st to end	Night	23% 15% 33% 25% 5%	836
February	1st to 10th	Night	19% 13% 34% 27% 6%	760
	11th to 20th	Night	20% 15% 33% 24% 8%	743
	21st to end	Night	20% 14% 37% 26% 3	628
March	1st to 10th	Night	16% 15% 32% 30% 7%	760
	11th to 20th	Night	14% 15% 33% 28% 11%	760
	21st to end	Night	13% 13% 32% 30% 11% 1	746
April	1st to 10th	Night	16% 11% 27% 34% 12% 1	570
	11th to 20th	Night	14% 9% 29% 28% 18% 1	563
	21st to end	Night	7% 6% 26% 39% 21% 1	570
May	1st to 10th	Night	10% 7% 21% 37% 22% 3	570
	11th to 20th	Night	9% 4 17% 36% 29% 6%	561
	21st to end	Night	7% 1 13% 35% 37% 6%	617
June	1st to 10th	Night	9% 2 11% 32% 36% 10%	570
	11th to 20th	Night	4 3 9% 32% 41% 11%	570
	21st to end	Night	6% 1 9% 24% 46% 14%	570
July	1st to 10th	Night	5% 1 3 23% 47% 21%	555
	11th to 20th	Night	6% 1 3 17% 43% 30%	552
	21st to end	Night	4 3 25% 51% 18%	624
August	1st to 10th	Night	5% 1 4 18% 48% 25%	567
	11th to 20th	Night	5% 2 2 21% 46% 24%	564
	21st to end	Night	8% 2 7% 24% 42% 17%	627
September	1st to 10th	Night	11% 3 7% 24% 40% 15%	613
	11th to 20th	Night	12% 3 12% 28% 38% 7%	760
	21st to end	Night	10% 2 15% 29% 36% 7%	760
October	1st to 10th	Night	9% 3 26% 34% 25% 3	760
	11th to 20th	Night	9% 6% 23% 32% 28% 3	760
	21st to end	Night	13% 6% 23% 34% 22% 2	836
November	1st to 10th	Night	10% 6% 25% 37% 19% 2	780
	11th to 20th	Night	13% 10% 28% 34% 14% 1	765
	21st to end	Night	15% 9% 29% 33% 13% 1	760
December	1st to 10th	Night	16% 11% 29% 28% 14% 1	760
	11th to 20th	Night	19% 10% 29% 30% 12%	760
	21st to end	Night	25% 13% 26% 26% 9%	836

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