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 2026-10-14.

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% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	148857
	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	142879
Transparency	Day	36% 8% 14% 19% 17% 7%	152643
	Night	36% 7% 12% 18% 18% 8%	147165
Seeing	Day	12% 7% 20% 24% 23% 13%	17587
	Night	13% 6% 22% 32% 24% 4	27544

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	13% 6% 3 6% 4 4 4 3 4 6% 48%	5258
	11th to 20th	Day	12% 5% 2 4 2 2 2 3 4 7% 56%	5280
	21st to end	Day	17% 7% 3 7% 5% 4 5% 3 5% 6% 39%	6153
February	1st to 10th	Day	14% 8% 3 7% 4 4 5% 4 5% 6% 41%	2100
	11th to 20th	Day	18% 6% 2 5% 4 4 4 3 5% 6% 44%	2048
	21st to end	Day	16% 7% 2 5% 4 4 4 2 5% 7% 44%	1730
March	1st to 10th	Day	19% 6% 3 6% 5% 4 4 3 6% 6% 38%	4804
	11th to 20th	Day	8% 4 2 4 3 4 5% 3 5% 7% 54%	5090
	21st to end	Day	15% 6% 2 6% 4 3 4 3 5% 6% 46%	5586
April	1st to 10th	Day	11% 6% 2 5% 5% 4 4 3 5% 6% 47%	2310
	11th to 20th	Day	11% 4 2 5% 4 3 4 3 5% 7% 52%	2478
	21st to end	Day	7% 4 2 5% 4 4 4 3 5% 8% 54%	2667
May	1st to 10th	Day	14% 7% 3 7% 5% 5% 4 3 5% 8% 40%	7616
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 4 7% 10% 39%	7626
	21st to end	Day	8% 6% 3 8% 6% 5% 6% 5% 7% 9% 37%	8391
June	1st to 10th	Day	10% 6% 3 7% 6% 6% 7% 5% 8% 9% 32%	2730
	11th to 20th	Day	6% 4 2 7% 6% 5% 6% 5% 8% 11% 41%	2730
	21st to end	Day	5% 5% 2 7% 6% 6% 6% 5% 9% 11% 36%	2730
July	1st to 10th	Day	7% 5% 2 7% 6% 6% 8% 7% 10% 13% 29%	7680
	11th to 20th	Day	4 4 2 6% 6% 6% 7% 6% 10% 13% 35%	7680
	21st to end	Day	5% 5% 3 8% 6% 7% 7% 7% 10% 15% 27%	8340
August	1st to 10th	Day	9% 6% 2 8% 5% 6% 6% 5% 9% 13% 29%	6000
	11th to 20th	Day	4 3 1 4 4 5% 5% 4 7% 12% 50%	5486
	21st to end	Day	7% 6% 2 7% 5% 5% 6% 5% 8% 11% 37%	5991
September	1st to 10th	Day	9% 5% 2 8% 5% 5% 6% 4 8% 10% 37%	2310
	11th to 20th	Day	12% 6% 3 6% 5% 4 5% 5% 6% 8% 42%	2310
	21st to end	Day	12% 6% 3 7% 5% 5% 4 4 5% 6% 44%	2310
October	1st to 10th	Day	13% 6% 2 5% 4 3 4 3 4 6% 49%	2310
	11th to 20th	Day	10% 4 1 4 2 3 4 3 3 7% 59%	2128
	21st to end	Day	11% 4 1 5% 3 4 3 3 4 6% 56%	2200
November	1st to 10th	Day	12% 5% 2 4 3 3 4 3 5% 5% 54%	1957
	11th to 20th	Day	12% 5% 2 4 3 2 4 3 4 5% 56%	1890
	21st to end	Day	13% 5% 2 5% 4 4 4 3 5% 6% 47%	1890
December	1st to 10th	Day	14% 7% 2 5% 3 3 3 3 4 5% 50%	3020
	11th to 20th	Day	16% 6% 2 6% 3 3 4 3 4 5% 48%	3463
	21st to end	Day	20% 8% 2 6% 3 3 3 3 4 5% 44%	4565
January	1st to 10th	Night	12% 6% 1 5% 4 5% 5% 4 6% 7% 47%	7635
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 48%	7680
	21st to end	Night	18% 8% 3 6% 4 4 3 3 4 6% 40%	8025
February	1st to 10th	Night	14% 7% 2 6% 4 4 3 3 5% 6% 46%	2520
	11th to 20th	Night	18% 6% 2 5% 4 3 3 3 4 5% 46%	2458
	21st to end	Night	15% 6% 2 6% 3 4 4 3 6% 6% 45%	2076
March	1st to 10th	Night	20% 7% 3 6% 3 3 4 3 5% 7% 39%	5268
	11th to 20th	Night	10% 5% 1 4 4 4 4 4 6% 8% 51%	5090
	21st to end	Night	12% 5% 2 6% 4 4 4 4 5% 6% 48%	5588
April	1st to 10th	Night	10% 6% 2 5% 5% 4 3 4 6% 7% 47%	2310
	11th to 20th	Night	11% 4 2 5% 3 3 4 3 5% 7% 53%	2107
	21st to end	Night	6% 5% 2 5% 3 3 4 4 6% 7% 55%	1950
May	1st to 10th	Night	12% 6% 2 7% 5% 4 4 4 6% 9% 39%	5237
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 4 7% 9% 41%	5234
	21st to end	Night	9% 7% 3 8% 5% 5% 5% 5% 8% 10% 36%	5761
June	1st to 10th	Night	9% 7% 2 8% 5% 7% 6% 5% 7% 11% 33%	1890
	11th to 20th	Night	5% 4 2 5% 4 6% 6% 5% 8% 13% 41%	1890
	21st to end	Night	4 5% 2 7% 5% 6% 7% 6% 9% 11% 39%	1890
July	1st to 10th	Night	8% 6% 2 8% 6% 6% 7% 6% 10% 13% 28%	5278
	11th to 20th	Night	5% 5% 2 8% 6% 7% 7% 7% 10% 14% 28%	5277
	21st to end	Night	6% 6% 3 8% 6% 7% 8% 6% 9% 14% 28%	5736
August	1st to 10th	Night	10% 8% 3 9% 6% 6% 7% 5% 8% 12% 27%	4135
	11th to 20th	Night	4 3 1 4 4 4 6% 5% 9% 15% 45%	4556
	21st to end	Night	7% 5% 2 6% 5% 5% 6% 5% 7% 11% 41%	5086
September	1st to 10th	Night	10% 6% 2 7% 5% 6% 5% 5% 7% 9% 38%	2310
	11th to 20th	Night	12% 6% 3 6% 5% 5% 5% 4 5% 7% 44%	2310
	21st to end	Night	9% 6% 3 6% 4 5% 5% 3 6% 8% 45%	2310
October	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 4 7% 50%	2310
	11th to 20th	Night	10% 4 1 4 2 2 3 2 4 5% 61%	2339
	21st to end	Night	10% 4 2 5% 4 3 3 3 4 5% 57%	2640
November	1st to 10th	Night	12% 5% 2 4 3 3 3 3 4 4 56%	2558
	11th to 20th	Night	13% 5% 2 4 3 2 3 2 4 6% 56%	2730
	21st to end	Night	13% 5% 2 6% 4 3 4 3 5% 6% 49%	2730
December	1st to 10th	Night	14% 5% 2 5% 3 3 3 2 4 5% 55%	4380
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 6% 50%	4952
	21st to end	Night	18% 8% 2 6% 4 3 4 3 4 5% 43%	6633

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 7% 19% 26% 7%	5259
	11th to 20th	Day	30% 3 5% 15% 32% 16%	5280
	21st to end	Day	45% 4 7% 14% 20% 11%	6153
February	1st to 10th	Day	42% 5% 8% 16% 21% 9%	2100
	11th to 20th	Day	41% 5% 6% 16% 24% 8%	2058
	21st to end	Day	40% 5% 8% 16% 20% 11%	1730
March	1st to 10th	Day	45% 6% 8% 14% 19% 9%	4804
	11th to 20th	Day	29% 6% 9% 15% 21% 21%	5090
	21st to end	Day	39% 5% 9% 19% 18% 11%	5586
April	1st to 10th	Day	37% 6% 9% 21% 18% 10%	2310
	11th to 20th	Day	31% 5% 8% 20% 24% 12%	2478
	21st to end	Day	28% 6% 11% 25% 24% 6%	2667
May	1st to 10th	Day	42% 7% 13% 19% 17% 3	7651
	11th to 20th	Day	38% 8% 18% 22% 11% 2	7630
	21st to end	Day	41% 11% 15% 18% 15% 1	8405
June	1st to 10th	Day	42% 11% 15% 17% 12% 2	2730
	11th to 20th	Day	32% 11% 18% 22% 16% 1	2730
	21st to end	Day	37% 12% 19% 19% 11% 2	2730
July	1st to 10th	Day	38% 14% 26% 18% 2	7615
	11th to 20th	Day	33% 15% 31% 18% 2	7611
	21st to end	Day	38% 16% 24% 17% 5%	8156
August	1st to 10th	Day	41% 12% 24% 19% 4	5987
	11th to 20th	Day	24% 9% 23% 33% 11%	5522
	21st to end	Day	35% 9% 20% 24% 10% 1	5991
September	1st to 10th	Day	39% 9% 17% 16% 14% 3	2310
	11th to 20th	Day	38% 9% 10% 21% 18% 4	2310
	21st to end	Day	40% 7% 9% 19% 19% 7%	2310
October	1st to 10th	Day	35% 3 7% 12% 27% 16%	3700
	11th to 20th	Day	16% 2 5% 17% 26% 34%	3420
	21st to end	Day	20% 3 5% 18% 38% 16%	3538
November	1st to 10th	Day	32% 4 8% 15% 26% 15%	1957
	11th to 20th	Day	31% 4 7% 16% 27% 15%	1890
	21st to end	Day	36% 5% 8% 16% 24% 10%	1890
December	1st to 10th	Day	38% 4 6% 15% 27% 10%	3020
	11th to 20th	Day	39% 3 7% 20% 22% 8%	3460
	21st to end	Day	43% 4 5% 19% 24% 4	4565
January	1st to 10th	Night	34% 6% 9% 19% 26% 7%	7636
	11th to 20th	Night	37% 4 5% 16% 26% 12%	7680
	21st to end	Night	46% 4 5% 16% 21% 9%	8025
February	1st to 10th	Night	39% 4 7% 17% 22% 11%	2520
	11th to 20th	Night	41% 4 7% 14% 22% 12%	2459
	21st to end	Night	38% 6% 8% 15% 18% 15%	2076
March	1st to 10th	Night	44% 5% 9% 15% 16% 11%	5268
	11th to 20th	Night	29% 5% 10% 13% 23% 19%	5090
	21st to end	Night	37% 5% 7% 17% 21% 13%	5588
April	1st to 10th	Night	35% 7% 9% 18% 18% 13%	2310
	11th to 20th	Night	30% 4 8% 21% 24% 13%	2107
	21st to end	Night	27% 6% 11% 24% 23% 8%	1950
May	1st to 10th	Night	39% 9% 15% 17% 15% 5%	5264
	11th to 20th	Night	36% 9% 17% 23% 12% 2	5235
	21st to end	Night	39% 10% 15% 20% 14% 2	5771
June	1st to 10th	Night	41% 12% 16% 18% 12% 1	1890
	11th to 20th	Night	31% 11% 20% 25% 12% 1	1890
	21st to end	Night	34% 13% 20% 17% 12% 3	1890
July	1st to 10th	Night	42% 14% 24% 15% 4 1	5235
	11th to 20th	Night	40% 16% 28% 14% 2	5226
	21st to end	Night	42% 14% 25% 15% 4	5606
August	1st to 10th	Night	46% 12% 22% 18% 2	4124
	11th to 20th	Night	24% 11% 25% 29% 9% 1	4586
	21st to end	Night	35% 9% 20% 26% 9% 1	5086
September	1st to 10th	Night	38% 11% 18% 16% 13% 4	2310
	11th to 20th	Night	39% 8% 13% 17% 19% 4	2310
	21st to end	Night	36% 8% 13% 16% 20% 7%	2310
October	1st to 10th	Night	36% 5% 7% 13% 21% 18%	3700
	11th to 20th	Night	16% 3 5% 12% 30% 34%	3786
	21st to end	Night	19% 3 4 19% 34% 20%	4252
November	1st to 10th	Night	32% 4 7% 14% 28% 15%	2558
	11th to 20th	Night	30% 4 6% 16% 28% 16%	2730
	21st to end	Night	37% 5% 6% 18% 22% 12%	2730
December	1st to 10th	Night	34% 3 6% 20% 27% 10%	4380
	11th to 20th	Night	36% 5% 9% 19% 23% 9%	4954
	21st to end	Night	43% 4 5% 20% 23% 3	6633

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	14% 17% 46% 19% 4	330
	11th to 20th	Day	12% 22% 34% 19% 10% 2	330
	21st to end	Day	22% 16% 42% 14% 5% 1	363
February	1st to 10th	Day	16% 16% 40% 22% 6%	330
	11th to 20th	Day	25% 17% 34% 21% 3	330
	21st to end	Day	16% 20% 42% 18% 4	273
March	1st to 10th	Day	14% 15% 29% 30% 11% 1	424
	11th to 20th	Day	15% 10% 36% 26% 11% 2	540
	21st to end	Day	16% 9% 34% 29% 10% 2	594
April	1st to 10th	Day	15% 14% 27% 27% 14% 3	540
	11th to 20th	Day	12% 9% 29% 27% 19% 4	532
	21st to end	Day	8% 7% 23% 31% 24% 7%	540
May	1st to 10th	Day	9% 10% 25% 27% 22% 7%	543
	11th to 20th	Day	10% 4 18% 30% 24% 14%	567
	21st to end	Day	11% 3 13% 28% 27% 17%	617
June	1st to 10th	Day	11% 2 11% 28% 31% 16%	570
	11th to 20th	Day	8% 3 13% 20% 29% 28%	570
	21st to end	Day	6% 3 9% 23% 34% 26%	570
July	1st to 10th	Day	5% 2 6% 16% 35% 37%	565
	11th to 20th	Day	6% 1 2 18% 31% 42%	564
	21st to end	Day	6% 1 4 19% 40% 30%	620
August	1st to 10th	Day	13% 2 6% 18% 33% 27%	566
	11th to 20th	Day	7% 1 4 14% 40% 34%	559
	21st to end	Day	11% 4 8% 23% 31% 23%	627
September	1st to 10th	Day	10% 2 8% 26% 32% 22%	570
	11th to 20th	Day	13% 3 8% 26% 35% 15%	570
	21st to end	Day	14% 4 12% 24% 28% 18%	570
October	1st to 10th	Day	15% 3 23% 29% 20% 10%	570
	11th to 20th	Day	10% 6% 16% 31% 28% 9%	542
	21st to end	Day	11% 7% 23% 30% 24% 5%	583
November	1st to 10th	Day	17% 5% 20% 31% 22% 4	435
	11th to 20th	Day	13% 9% 34% 29% 12% 3	330
	21st to end	Day	11% 15% 30% 29% 14% 2	330
December	1st to 10th	Day	23% 11% 35% 21% 9% 2	330
	11th to 20th	Day	20% 13% 32% 20% 12% 2	330
	21st to end	Day	23% 12% 28% 26% 9% 1	363
January	1st to 10th	Night	18% 10% 37% 28% 5% 1	840
	11th to 20th	Night	16% 10% 33% 31% 10%	840
	21st to end	Night	19% 11% 38% 29% 4	924
February	1st to 10th	Night	16% 9% 33% 34% 7%	840
	11th to 20th	Night	21% 10% 34% 30% 5%	823
	21st to end	Night	17% 11% 36% 32% 4	692
March	1st to 10th	Night	14% 10% 32% 37% 7%	840
	11th to 20th	Night	13% 8% 35% 32% 11%	840
	21st to end	Night	11% 11% 31% 35% 12%	924
April	1st to 10th	Night	13% 8% 30% 34% 15%	840
	11th to 20th	Night	14% 6% 26% 36% 17% 1	655
	21st to end	Night	7% 5% 23% 41% 23% 1	630
May	1st to 10th	Night	8% 5% 24% 41% 21% 2	630
	11th to 20th	Night	9% 3 22% 37% 26% 4	621
	21st to end	Night	8% 3 10% 38% 35% 6%	683
June	1st to 10th	Night	9% 3 11% 37% 36% 4	630
	11th to 20th	Night	5% 3 8% 33% 41% 10%	630
	21st to end	Night	6% 1 7% 31% 47% 9%	630
July	1st to 10th	Night	7% 2 5% 25% 46% 16%	615
	11th to 20th	Night	8% 1 3 19% 51% 18%	612
	21st to end	Night	7% 1 4 24% 53% 12%	690
August	1st to 10th	Night	7% 2 5% 24% 46% 15%	627
	11th to 20th	Night	8% 1 4 20% 52% 13%	624
	21st to end	Night	13% 2 6% 26% 40% 13%	707
September	1st to 10th	Night	10% 2 8% 31% 40% 9%	840
	11th to 20th	Night	13% 2 9% 31% 40% 6%	840
	21st to end	Night	12% 2 12% 31% 40% 3	840
October	1st to 10th	Night	12% 2 19% 35% 26% 5%	840
	11th to 20th	Night	12% 4 19% 35% 27% 3	813
	21st to end	Night	12% 4 23% 36% 24% 2	880
November	1st to 10th	Night	13% 6% 20% 39% 21% 2	820
	11th to 20th	Night	14% 6% 26% 37% 15% 1	840
	21st to end	Night	15% 7% 31% 31% 15% 1	840
December	1st to 10th	Night	17% 7% 30% 32% 13% 1	840
	11th to 20th	Night	17% 6% 30% 33% 12% 1	840
	21st to end	Night	23% 9% 23% 35% 9%	924

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