Yoder Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yoder Observing Site clear sky chart from 2005-11-06 to 2024-11-02.

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	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	100939
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	97981
Transparency	Day	37% 8% 12% 19% 17% 6%	100749
	Night	37% 8% 12% 18% 18% 8%	97841
Seeing	Day	12% 7% 20% 24% 23% 14%	14985
	Night	13% 5% 22% 32% 24% 4	24984

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	16% 5% 3 6% 4 4 4 3 5% 6% 45%	2836
	11th to 20th	Day	12% 6% 2 4 3 3 2 3 4 6% 56%	2840
	21st to end	Day	19% 7% 3 5% 4 3 4 3 4 6% 42%	3317
February	1st to 10th	Day	15% 8% 3 7% 4 4 5% 4 5% 6% 40%	1900
	11th to 20th	Day	18% 6% 2 5% 4 4 3 3 5% 6% 45%	1848
	21st to end	Day	16% 8% 2 5% 4 4 4 3 5% 7% 43%	1570
March	1st to 10th	Day	21% 7% 3 7% 5% 4 4 3 5% 6% 36%	3270
	11th to 20th	Day	9% 4 2 5% 4 4 6% 3 6% 8% 49%	3480
	21st to end	Day	17% 5% 2 6% 4 3 4 4 5% 7% 43%	3815
April	1st to 10th	Day	11% 6% 2 6% 5% 4 4 3 5% 7% 47%	2090
	11th to 20th	Day	12% 5% 2 5% 4 3 4 3 5% 8% 50%	2240
	21st to end	Day	7% 4 1 5% 4 4 4 3 5% 8% 56%	2413
May	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 6% 8% 48%	4082
	11th to 20th	Day	14% 7% 3 7% 4 5% 5% 3 6% 8% 39%	4081
	21st to end	Day	6% 4 1 5% 5% 5% 6% 5% 7% 9% 48%	4476
June	1st to 10th	Day	10% 6% 2 7% 7% 6% 7% 5% 8% 10% 32%	2470
	11th to 20th	Day	5% 4 1 6% 6% 4 6% 5% 8% 11% 43%	2470
	21st to end	Day	6% 5% 2 7% 6% 7% 7% 5% 9% 11% 35%	2470
July	1st to 10th	Day	11% 7% 2 8% 8% 7% 9% 7% 10% 11% 20%	4120
	11th to 20th	Day	5% 5% 2 7% 7% 6% 7% 6% 9% 11% 34%	4120
	21st to end	Day	7% 6% 3 9% 8% 8% 8% 7% 9% 13% 22%	4466
August	1st to 10th	Day	10% 6% 2 7% 5% 6% 7% 5% 10% 12% 31%	4090
	11th to 20th	Day	5% 4 2 6% 5% 5% 5% 4 6% 10% 47%	3729
	21st to end	Day	8% 5% 2 6% 4 5% 6% 4 7% 11% 44%	4121
September	1st to 10th	Day	9% 5% 2 9% 5% 6% 6% 4 7% 10% 36%	2090
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 5% 6% 8% 39%	2090
	21st to end	Day	13% 6% 3 7% 5% 4 4 4 5% 5% 44%	2090
October	1st to 10th	Day	12% 6% 2 4 4 3 4 3 4 6% 51%	2090
	11th to 20th	Day	10% 3 1 3 3 3 4 3 3 7% 58%	1990
	21st to end	Day	10% 3 1 5% 3 3 3 3 4 6% 56%	2090
November	1st to 10th	Day	11% 5% 2 4 3 3 4 3 5% 5% 54%	1778
	11th to 20th	Day	13% 5% 2 4 3 3 4 3 4 5% 54%	1710
	21st to end	Day	15% 5% 2 5% 4 4 4 3 4 6% 47%	1710
December	1st to 10th	Day	16% 6% 2 6% 5% 4 5% 3 5% 6% 42%	1710
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 4 6% 45%	2153
	21st to end	Day	19% 8% 3 7% 3 3 2 3 4 5% 43%	3124
January	1st to 10th	Night	17% 6% 1 4 4 5% 4 4 5% 7% 42%	4109
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 48%	4120
	21st to end	Night	20% 8% 3 6% 4 4 3 2 4 5% 41%	4336
February	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 6% 45%	2280
	11th to 20th	Night	18% 6% 2 5% 4 2 3 3 4 5% 47%	2218
	21st to end	Night	15% 7% 2 6% 3 4 4 3 6% 6% 45%	1884
March	1st to 10th	Night	24% 9% 3 6% 4 3 3 2 4 6% 37%	3583
	11th to 20th	Night	11% 5% 2 4 4 4 4 4 6% 8% 48%	3480
	21st to end	Night	15% 5% 2 6% 4 5% 4 4 5% 6% 43%	3817
April	1st to 10th	Night	11% 5% 2 5% 5% 4 3 4 6% 7% 48%	2090
	11th to 20th	Night	12% 4 2 5% 3 3 4 4 5% 7% 50%	1904
	21st to end	Night	6% 5% 2 4 3 3 4 4 6% 7% 56%	1764
May	1st to 10th	Night	5% 5% 2 6% 5% 4 5% 5% 7% 11% 45%	2813
	11th to 20th	Night	14% 6% 2 6% 4 4 5% 4 6% 7% 43%	2812
	21st to end	Night	6% 4 2 5% 4 4 4 3 7% 11% 52%	3079
June	1st to 10th	Night	8% 7% 2 8% 6% 7% 6% 5% 7% 11% 32%	1710
	11th to 20th	Night	4 3 2 5% 4 6% 6% 5% 8% 13% 43%	1710
	21st to end	Night	4 5% 2 7% 5% 6% 7% 6% 9% 11% 37%	1710
July	1st to 10th	Night	11% 8% 3 9% 6% 7% 7% 6% 9% 11% 23%	2840
	11th to 20th	Night	4 4 2 7% 5% 6% 7% 8% 12% 13% 31%	2840
	21st to end	Night	9% 7% 3 9% 7% 7% 8% 6% 9% 11% 24%	3087
August	1st to 10th	Night	10% 7% 3 8% 5% 6% 6% 5% 8% 12% 30%	2825
	11th to 20th	Night	5% 4 1 5% 5% 4 5% 5% 8% 12% 45%	3096
	21st to end	Night	6% 4 2 5% 4 4 5% 4 7% 11% 48%	3501
September	1st to 10th	Night	11% 6% 2 7% 5% 6% 6% 5% 8% 9% 36%	2090
	11th to 20th	Night	13% 6% 3 7% 5% 5% 5% 3 5% 7% 41%	2090
	21st to end	Night	9% 6% 3 7% 4 4 6% 3 6% 7% 45%	2090
October	1st to 10th	Night	11% 5% 1 5% 3 4 4 3 4 8% 52%	2090
	11th to 20th	Night	10% 5% 2 4 2 2 3 2 4 5% 60%	2190
	21st to end	Night	10% 4 2 5% 4 3 4 3 4 5% 57%	2508
November	1st to 10th	Night	11% 5% 2 4 3 3 4 4 4 5% 56%	2331
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 4 6% 55%	2470
	21st to end	Night	14% 6% 3 6% 3 3 3 3 4 6% 49%	2470
December	1st to 10th	Night	14% 5% 2 6% 4 4 4 4 5% 6% 47%	2470
	11th to 20th	Night	16% 6% 1 6% 3 3 3 2 5% 6% 48%	3042
	21st to end	Night	18% 9% 3 7% 4 4 4 3 5% 6% 36%	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	40% 5% 6% 18% 23% 10%	2837
	11th to 20th	Day	31% 4 6% 16% 31% 13%	2840
	21st to end	Day	44% 5% 5% 13% 22% 12%	3317
February	1st to 10th	Day	44% 5% 8% 15% 19% 9%	1900
	11th to 20th	Day	40% 5% 6% 16% 25% 9%	1858
	21st to end	Day	40% 5% 9% 15% 19% 11%	1570
March	1st to 10th	Day	48% 7% 8% 15% 14% 8%	3270
	11th to 20th	Day	32% 7% 11% 16% 23% 11%	3480
	21st to end	Day	40% 6% 10% 19% 17% 9%	3815
April	1st to 10th	Day	37% 6% 8% 20% 18% 10%	2090
	11th to 20th	Day	33% 5% 9% 19% 22% 12%	2240
	21st to end	Day	26% 6% 10% 26% 25% 7%	2413
May	1st to 10th	Day	31% 10% 12% 24% 19% 4	4120
	11th to 20th	Day	41% 9% 11% 23% 14% 2	4085
	21st to end	Day	28% 10% 16% 25% 19% 2	4489
June	1st to 10th	Day	43% 11% 15% 17% 12% 2	2470
	11th to 20th	Day	30% 12% 16% 24% 17% 1	2470
	21st to end	Day	38% 12% 19% 17% 12% 3	2470
July	1st to 10th	Day	48% 16% 22% 10% 3 1	4055
	11th to 20th	Day	38% 14% 23% 21% 3 1	4051
	21st to end	Day	47% 18% 18% 12% 4	4324
August	1st to 10th	Day	40% 11% 21% 23% 5%	4077
	11th to 20th	Day	30% 8% 16% 31% 14% 1	3765
	21st to end	Day	31% 9% 20% 28% 11% 1	4121
September	1st to 10th	Day	41% 10% 17% 15% 14% 3	2090
	11th to 20th	Day	40% 10% 10% 18% 17% 5%	2090
	21st to end	Day	41% 7% 8% 19% 19% 7%	2090
October	1st to 10th	Day	34% 5% 10% 17% 23% 12%	2090
	11th to 20th	Day	26% 4 8% 24% 25% 13%	1990
	21st to end	Day	29% 5% 6% 13% 30% 17%	2090
November	1st to 10th	Day	32% 4 8% 15% 26% 16%	1778
	11th to 20th	Day	32% 4 7% 16% 26% 15%	1710
	21st to end	Day	37% 6% 8% 16% 23% 10%	1710
December	1st to 10th	Day	42% 6% 10% 13% 19% 9%	1710
	11th to 20th	Day	42% 4 6% 14% 26% 8%	2150
	21st to end	Day	45% 4 6% 16% 24% 5%	3124
January	1st to 10th	Night	38% 6% 7% 15% 22% 10%	4109
	11th to 20th	Night	32% 6% 6% 20% 25% 10%	4120
	21st to end	Night	46% 5% 5% 11% 24% 9%	4336
February	1st to 10th	Night	40% 4 8% 16% 20% 12%	2280
	11th to 20th	Night	40% 4 6% 14% 22% 13%	2219
	21st to end	Night	38% 6% 8% 15% 17% 15%	1884
March	1st to 10th	Night	50% 5% 9% 14% 14% 8%	3583
	11th to 20th	Night	32% 6% 11% 14% 25% 12%	3480
	21st to end	Night	41% 6% 8% 16% 19% 11%	3817
April	1st to 10th	Night	34% 6% 9% 18% 18% 14%	2090
	11th to 20th	Night	32% 5% 8% 21% 22% 12%	1904
	21st to end	Night	25% 6% 11% 25% 24% 9%	1764
May	1st to 10th	Night	27% 13% 15% 23% 18% 5%	2840
	11th to 20th	Night	37% 11% 14% 23% 13% 3	2813
	21st to end	Night	24% 9% 16% 27% 20% 3	3087
June	1st to 10th	Night	41% 12% 16% 18% 12% 1	1710
	11th to 20th	Night	29% 11% 20% 26% 13% 2	1710
	21st to end	Night	35% 14% 21% 15% 12% 4	1710
July	1st to 10th	Night	51% 16% 21% 8% 4 1	2795
	11th to 20th	Night	36% 16% 27% 17% 5%	2786
	21st to end	Night	49% 17% 18% 12% 3 1	2988
August	1st to 10th	Night	43% 11% 21% 23% 3	2814
	11th to 20th	Night	28% 11% 18% 29% 13% 1	3126
	21st to end	Night	28% 9% 21% 31% 11% 1	3501
September	1st to 10th	Night	41% 11% 16% 14% 13% 4	2090
	11th to 20th	Night	42% 9% 13% 16% 17% 4	2090
	21st to end	Night	37% 8% 12% 15% 21% 7%	2090
October	1st to 10th	Night	32% 6% 8% 20% 22% 13%	2090
	11th to 20th	Night	27% 4 8% 19% 29% 14%	2190
	21st to end	Night	28% 4 6% 16% 28% 17%	2508
November	1st to 10th	Night	31% 5% 8% 14% 27% 16%	2331
	11th to 20th	Night	31% 4 6% 15% 27% 16%	2470
	21st to end	Night	37% 5% 6% 19% 22% 11%	2470
December	1st to 10th	Night	38% 5% 10% 18% 22% 7%	2470
	11th to 20th	Night	38% 5% 6% 14% 29% 9%	3044
	21st to end	Night	48% 5% 6% 17% 20% 4	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	13% 18% 45% 20% 4	270
	11th to 20th	Day	11% 20% 35% 20% 11% 2	270
	21st to end	Day	22% 18% 43% 12% 5% 1	297
February	1st to 10th	Day	19% 17% 38% 21% 6%	270
	11th to 20th	Day	26% 15% 33% 22% 4	270
	21st to end	Day	16% 20% 42% 17% 4	225
March	1st to 10th	Day	14% 15% 30% 28% 12% 1	355
	11th to 20th	Day	15% 9% 38% 27% 10% 2	460
	21st to end	Day	16% 11% 35% 28% 9% 1	506
April	1st to 10th	Day	15% 15% 27% 28% 13% 2	460
	11th to 20th	Day	14% 9% 31% 26% 16% 4	452
	21st to end	Day	9% 8% 22% 32% 24% 6%	460
May	1st to 10th	Day	7% 10% 24% 28% 24% 8%	463
	11th to 20th	Day	10% 4 17% 28% 25% 16%	487
	21st to end	Day	10% 2 13% 28% 28% 19%	529
June	1st to 10th	Day	11% 2 10% 27% 32% 17%	490
	11th to 20th	Day	8% 2 13% 20% 28% 29%	490
	21st to end	Day	6% 3 9% 24% 32% 26%	490
July	1st to 10th	Day	5% 2 6% 16% 34% 37%	485
	11th to 20th	Day	6% 1 3 18% 29% 43%	484
	21st to end	Day	6% 4 18% 39% 33%	532
August	1st to 10th	Day	11% 2 6% 19% 33% 29%	486
	11th to 20th	Day	8% 1 5% 16% 40% 31%	479
	21st to end	Day	10% 4 7% 22% 32% 24%	539
September	1st to 10th	Day	11% 2 8% 23% 32% 23%	490
	11th to 20th	Day	15% 4 9% 26% 33% 13%	490
	21st to end	Day	14% 3 12% 24% 29% 18%	490
October	1st to 10th	Day	14% 2 23% 30% 21% 10%	490
	11th to 20th	Day	10% 6% 17% 32% 26% 9%	490
	21st to end	Day	10% 7% 23% 29% 26% 5%	539
November	1st to 10th	Day	16% 5% 22% 31% 23% 5%	370
	11th to 20th	Day	14% 11% 36% 27% 10% 2	270
	21st to end	Day	13% 11% 29% 31% 14% 2	270
December	1st to 10th	Day	21% 11% 34% 23% 10% 2	270
	11th to 20th	Day	22% 13% 33% 21% 10% 1	270
	21st to end	Day	25% 11% 30% 22% 10% 1	297
January	1st to 10th	Night	19% 10% 37% 27% 6% 1	760
	11th to 20th	Night	16% 9% 32% 32% 11%	760
	21st to end	Night	19% 11% 37% 29% 4	836
February	1st to 10th	Night	17% 8% 33% 34% 7%	760
	11th to 20th	Night	22% 9% 33% 31% 6%	743
	21st to end	Night	17% 10% 37% 32% 4	628
March	1st to 10th	Night	14% 9% 33% 37% 7%	760
	11th to 20th	Night	14% 8% 34% 31% 12% 1	760
	21st to end	Night	12% 11% 31% 34% 12%	836
April	1st to 10th	Night	13% 8% 31% 33% 15%	760
	11th to 20th	Night	15% 7% 26% 35% 16% 1	592
	21st to end	Night	6% 4 25% 41% 22% 1	570
May	1st to 10th	Night	6% 4 25% 41% 22% 2	570
	11th to 20th	Night	8% 3 21% 37% 27% 4	561
	21st to end	Night	8% 2 10% 38% 36% 6%	617
June	1st to 10th	Night	9% 2 11% 37% 36% 5%	570
	11th to 20th	Night	3 3 8% 33% 42% 11%	570
	21st to end	Night	6% 1 7% 32% 45% 9%	570
July	1st to 10th	Night	7% 2 5% 25% 45% 16%	555
	11th to 20th	Night	8% 3 19% 50% 19%	552
	21st to end	Night	7% 1 4 24% 52% 12%	624
August	1st to 10th	Night	6% 2 5% 25% 47% 15%	567
	11th to 20th	Night	9% 1 4 21% 51% 13%	564
	21st to end	Night	12% 1 6% 25% 41% 14%	639
September	1st to 10th	Night	11% 2 8% 28% 42% 9%	760
	11th to 20th	Night	14% 2 9% 30% 39% 6%	760
	21st to end	Night	12% 2 12% 31% 40% 3	760
October	1st to 10th	Night	11% 2 18% 36% 28% 5%	760
	11th to 20th	Night	13% 4 19% 35% 26% 3	760
	21st to end	Night	11% 4 22% 36% 25% 2	836
November	1st to 10th	Night	13% 5% 20% 38% 22% 2	748
	11th to 20th	Night	14% 7% 27% 36% 15% 1	760
	21st to end	Night	16% 6% 30% 31% 16% 1	760
December	1st to 10th	Night	16% 7% 29% 33% 14% 1	760
	11th to 20th	Night	18% 6% 30% 32% 12% 1	760
	21st to end	Night	24% 10% 23% 34% 9%	836

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