Yonderplace Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yonderplace Observatory clear sky chart from 2005-11-06 to 2024-11-28.

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	14% 6% 2 5% 4 4 5% 4 6% 8% 43%	100896
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	98546
Transparency	Day	37% 6% 13% 22% 17% 4	104545
	Night	38% 6% 10% 22% 19% 5%	103036
Seeing	Day	18% 10% 25% 25% 16% 6%	15280
	Night	17% 9% 26% 31% 16% 2	25452

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	18% 5% 2 3 3 3 3 3 4 4 53%	2836
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 4 4 51%	2840
	21st to end	Day	21% 10% 3 5% 3 3 3 3 4 4 40%	3124
February	1st to 10th	Day	13% 6% 2 5% 5% 4 5% 4 5% 7% 43%	1710
	11th to 20th	Day	20% 6% 1 5% 4 4 4 3 4 5% 44%	1663
	21st to end	Day	19% 7% 2 6% 4 4 5% 2 5% 7% 38%	1690
March	1st to 10th	Day	21% 8% 3 6% 4 3 4 3 5% 7% 37%	3435
	11th to 20th	Day	11% 5% 2 4 3 4 4 4 5% 6% 53%	3480
	21st to end	Day	20% 6% 2 5% 4 4 4 3 5% 6% 41%	3815
April	1st to 10th	Day	11% 3 1 4 3 4 4 3 6% 8% 52%	2213
	11th to 20th	Day	11% 5% 2 6% 4 4 3 3 5% 7% 49%	2254
	21st to end	Day	14% 6% 2 6% 5% 4 4 4 6% 6% 44%	2292
May	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 5% 8% 8% 33%	4082
	11th to 20th	Day	18% 7% 3 7% 5% 4 4 5% 6% 8% 33%	4081
	21st to end	Day	9% 4 1 5% 4 5% 5% 4 6% 10% 47%	4476
June	1st to 10th	Day	10% 4 2 5% 4 5% 6% 5% 7% 10% 42%	2512
	11th to 20th	Day	9% 5% 2 5% 4 5% 4 4 8% 10% 44%	2601
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 8% 11% 41%	2470
July	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 6% 8% 12% 38%	4120
	11th to 20th	Day	10% 5% 2 5% 5% 5% 6% 5% 8% 12% 36%	4120
	21st to end	Day	11% 8% 3 7% 6% 6% 7% 5% 8% 9% 29%	4466
August	1st to 10th	Day	17% 7% 3 7% 5% 5% 6% 5% 7% 11% 27%	4104
	11th to 20th	Day	9% 5% 2 7% 4 5% 6% 5% 8% 11% 37%	3953
	21st to end	Day	7% 4 2 5% 4 4 5% 3 6% 10% 51%	4180
September	1st to 10th	Day	11% 4 2 5% 4 5% 5% 4 6% 7% 47%	2280
	11th to 20th	Day	15% 6% 2 6% 5% 4 4 4 6% 7% 42%	2154
	21st to end	Day	21% 7% 2 5% 4 3 4 3 5% 7% 38%	2047
October	1st to 10th	Day	16% 6% 2 5% 3 3 3 2 4 5% 52%	1900
	11th to 20th	Day	15% 4 1 4 3 3 3 3 4 4 56%	1900
	21st to end	Day	12% 4 2 6% 4 3 3 2 4 6% 55%	2090
November	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 4 6% 54%	1957
	11th to 20th	Day	14% 5% 2 4 3 3 3 3 5% 6% 51%	1949
	21st to end	Day	14% 4 2 4 3 3 4 4 5% 7% 50%	1576
December	1st to 10th	Day	18% 6% 2 5% 4 4 5% 4 5% 7% 40%	1520
	11th to 20th	Day	16% 5% 1 4 2 2 3 3 4 5% 55%	1910
	21st to end	Day	18% 6% 2 5% 3 4 4 4 6% 8% 42%	3096
January	1st to 10th	Night	14% 7% 2 6% 3 3 3 3 5% 5% 48%	4109
	11th to 20th	Night	15% 7% 3 5% 3 4 3 3 4 5% 48%	4120
	21st to end	Night	21% 7% 2 5% 3 3 4 2 4 4 44%	4532
February	1st to 10th	Night	16% 6% 2 5% 4 3 4 4 5% 6% 45%	2470
	11th to 20th	Night	19% 8% 2 5% 3 3 3 4 5% 6% 43%	2403
	21st to end	Night	15% 7% 2 5% 3 5% 4 3 5% 5% 46%	1757
March	1st to 10th	Night	21% 8% 3 7% 5% 4 4 4 4 5% 36%	3418
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 6% 53%	3480
	21st to end	Night	17% 5% 2 5% 4 3 3 3 5% 5% 48%	3817
April	1st to 10th	Night	14% 6% 3 6% 4 3 4 3 5% 7% 46%	1967
	11th to 20th	Night	12% 5% 1 4 3 4 4 4 6% 7% 51%	1875
	21st to end	Night	14% 5% 2 4 4 4 4 4 5% 8% 47%	1900
May	1st to 10th	Night	14% 7% 3 7% 5% 4 4 3 6% 7% 38%	2816
	11th to 20th	Night	24% 6% 3 6% 4 3 4 3 4 6% 36%	2812
	21st to end	Night	10% 4 2 5% 3 4 4 4 6% 10% 48%	3079
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 7% 10% 43%	1649
	11th to 20th	Night	9% 4 2 6% 3 5% 5% 5% 9% 11% 42%	1559
	21st to end	Night	7% 4 2 5% 5% 5% 6% 5% 7% 12% 41%	1710
July	1st to 10th	Night	6% 5% 3 8% 6% 6% 6% 6% 9% 9% 36%	2840
	11th to 20th	Night	10% 6% 2 8% 5% 6% 6% 5% 8% 10% 34%	2840
	21st to end	Night	14% 9% 4 8% 6% 6% 6% 4 7% 9% 29%	3087
August	1st to 10th	Night	17% 7% 3 7% 5% 5% 5% 4 8% 10% 28%	2825
	11th to 20th	Night	6% 5% 2 7% 4 5% 5% 5% 8% 10% 42%	2841
	21st to end	Night	8% 4 2 6% 4 5% 4 4 7% 9% 46%	3476
September	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 6% 7% 46%	1900
	11th to 20th	Night	15% 7% 3 5% 5% 4 5% 4 5% 5% 43%	2022
	21st to end	Night	22% 8% 2 5% 5% 4 4 3 5% 4 38%	2132
October	1st to 10th	Night	16% 5% 2 5% 4 4 4 3 5% 6% 47%	2280
	11th to 20th	Night	13% 6% 2 5% 3 3 3 2 4 5% 54%	2280
	21st to end	Night	13% 4 1 4 3 3 4 4 4 6% 55%	2508
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 52%	2341
	11th to 20th	Night	14% 5% 2 4 3 3 4 4 4 6% 50%	2446
	21st to end	Night	13% 4 2 5% 4 3 3 3 4 6% 52%	2755
December	1st to 10th	Night	17% 8% 3 6% 4 4 4 3 5% 5% 42%	2660
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 5% 49%	3285
	21st to end	Night	18% 6% 2 5% 3 3 4 3 6% 6% 43%	4555

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	35% 3 6% 28% 21% 5%	2837
	11th to 20th	Day	35% 5% 6% 22% 27% 6%	2840
	21st to end	Day	48% 4 6% 20% 18% 4	3124
February	1st to 10th	Day	39% 5% 11% 22% 19% 4	1710
	11th to 20th	Day	43% 3 7% 22% 20% 5%	1672
	21st to end	Day	46% 5% 12% 15% 18% 6%	1690
March	1st to 10th	Day	46% 5% 8% 20% 14% 7%	3435
	11th to 20th	Day	30% 6% 9% 21% 23% 11%	3480
	21st to end	Day	44% 5% 10% 20% 18% 3	3815
April	1st to 10th	Day	30% 5% 11% 24% 21% 9%	2213
	11th to 20th	Day	35% 5% 11% 22% 21% 7%	2254
	21st to end	Day	40% 5% 12% 23% 16% 4	2292
May	1st to 10th	Day	44% 8% 15% 20% 11% 2	4120
	11th to 20th	Day	46% 8% 11% 23% 9% 2	4085
	21st to end	Day	31% 7% 17% 24% 19% 3	4489
June	1st to 10th	Day	34% 8% 16% 28% 14% 1	2512
	11th to 20th	Day	33% 7% 19% 23% 16% 2	2601
	21st to end	Day	33% 11% 17% 23% 14% 2	2470
July	1st to 10th	Day	35% 12% 20% 18% 11% 4	4055
	11th to 20th	Day	37% 10% 23% 23% 7% 1	4051
	21st to end	Day	48% 10% 13% 18% 11%	4324
August	1st to 10th	Day	48% 8% 18% 21% 5%	4091
	11th to 20th	Day	36% 9% 23% 22% 9% 1	3992
	21st to end	Day	28% 6% 18% 31% 16% 2	4180
September	1st to 10th	Day	34% 8% 15% 18% 21% 4	2280
	11th to 20th	Day	40% 6% 10% 22% 19% 3	2154
	21st to end	Day	47% 6% 9% 18% 17% 3	2047
October	1st to 10th	Day	34% 4 8% 19% 28% 7%	3160
	11th to 20th	Day	22% 2 5% 23% 30% 17%	3140
	21st to end	Day	24% 3 9% 26% 26% 12%	3428
November	1st to 10th	Day	33% 4 8% 23% 27% 6%	1957
	11th to 20th	Day	34% 3 9% 22% 23% 8%	1949
	21st to end	Day	33% 3 9% 24% 25% 5%	1576
December	1st to 10th	Day	44% 5% 10% 21% 17% 4	1520
	11th to 20th	Day	33% 3 8% 26% 22% 8%	1906
	21st to end	Day	38% 6% 12% 25% 17% 2	3096
January	1st to 10th	Night	37% 4 6% 21% 26% 6%	4109
	11th to 20th	Night	39% 4 7% 19% 26% 5%	4120
	21st to end	Night	45% 3 5% 22% 18% 7%	4532
February	1st to 10th	Night	38% 5% 10% 24% 20% 4	2470
	11th to 20th	Night	42% 3 8% 19% 20% 7%	2405
	21st to end	Night	41% 4 8% 22% 18% 7%	1757
March	1st to 10th	Night	50% 5% 8% 17% 16% 4	3418
	11th to 20th	Night	32% 5% 7% 16% 26% 13%	3480
	21st to end	Night	38% 4 9% 24% 20% 5%	3817
April	1st to 10th	Night	37% 6% 10% 18% 23% 6%	1967
	11th to 20th	Night	32% 5% 10% 24% 22% 7%	1875
	21st to end	Night	36% 6% 12% 24% 19% 4	1900
May	1st to 10th	Night	44% 6% 15% 21% 12% 2	2843
	11th to 20th	Night	48% 7% 10% 21% 13% 2	2813
	21st to end	Night	30% 8% 16% 26% 17% 3	3087
June	1st to 10th	Night	33% 8% 17% 25% 16% 1	1649
	11th to 20th	Night	34% 8% 18% 21% 16% 2	1559
	21st to end	Night	35% 10% 14% 22% 16% 3	1710
July	1st to 10th	Night	40% 12% 15% 18% 12% 3	2795
	11th to 20th	Night	40% 11% 23% 19% 5% 2	2786
	21st to end	Night	51% 8% 13% 19% 9%	2988
August	1st to 10th	Night	49% 9% 18% 17% 7%	2814
	11th to 20th	Night	33% 9% 20% 28% 9% 1	2868
	21st to end	Night	32% 8% 12% 29% 17% 2	3476
September	1st to 10th	Night	36% 7% 12% 21% 18% 6%	1900
	11th to 20th	Night	41% 7% 10% 18% 21% 3	2022
	21st to end	Night	49% 5% 9% 17% 16% 4	2132
October	1st to 10th	Night	38% 5% 9% 18% 24% 6%	3800
	11th to 20th	Night	25% 3 6% 23% 28% 15%	3779
	21st to end	Night	22% 3 6% 29% 26% 14%	4120
November	1st to 10th	Night	34% 4 9% 20% 26% 7%	2341
	11th to 20th	Night	35% 4 8% 18% 25% 11%	2446
	21st to end	Night	33% 4 8% 23% 25% 7%	2755
December	1st to 10th	Night	44% 5% 8% 21% 18% 4	2660
	11th to 20th	Night	38% 4 8% 21% 21% 7%	3288
	21st to end	Night	40% 5% 9% 25% 19% 2	4555

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	30% 21% 30% 13% 5%	270
	11th to 20th	Day	28% 21% 39% 10% 1	270
	21st to end	Day	27% 19% 39% 13% 2	297
February	1st to 10th	Day	23% 18% 40% 16% 3	270
	11th to 20th	Day	37% 24% 29% 7% 3	270
	21st to end	Day	29% 20% 33% 16% 2	374
March	1st to 10th	Day	24% 17% 32% 20% 7%	460
	11th to 20th	Day	22% 21% 34% 17% 5% 1	460
	21st to end	Day	25% 13% 38% 19% 4 1	506
April	1st to 10th	Day	19% 20% 32% 20% 8% 1	460
	11th to 20th	Day	19% 13% 33% 20% 10% 5%	452
	21st to end	Day	21% 12% 33% 22% 10% 2	460
May	1st to 10th	Day	19% 13% 33% 22% 10% 3	463
	11th to 20th	Day	17% 10% 25% 28% 17% 4	487
	21st to end	Day	16% 5% 23% 27% 21% 7%	529
June	1st to 10th	Day	10% 4 26% 30% 22% 8%	490
	11th to 20th	Day	10% 5% 21% 33% 21% 10%	490
	21st to end	Day	11% 3 21% 32% 23% 8%	490
July	1st to 10th	Day	9% 2 12% 33% 31% 13%	485
	11th to 20th	Day	5% 2 12% 35% 33% 13%	484
	21st to end	Day	9% 2 17% 34% 26% 11%	532
August	1st to 10th	Day	15% 4 18% 26% 26% 13%	486
	11th to 20th	Day	12% 3 13% 31% 29% 13%	479
	21st to end	Day	9% 3 13% 27% 31% 17%	539
September	1st to 10th	Day	13% 4 15% 25% 27% 16%	490
	11th to 20th	Day	17% 5% 13% 28% 25% 11%	490
	21st to end	Day	26% 8% 22% 26% 14% 5%	490
October	1st to 10th	Day	21% 6% 19% 26% 21% 7%	490
	11th to 20th	Day	14% 10% 25% 26% 20% 5%	490
	21st to end	Day	15% 11% 26% 30% 13% 5%	539
November	1st to 10th	Day	17% 9% 29% 27% 13% 5%	495
	11th to 20th	Day	19% 13% 29% 24% 14% 2	449
	21st to end	Day	18% 20% 23% 26% 11% 3	194
December	1st to 10th	Day	21% 21% 34% 16% 6% 2	180
	11th to 20th	Day	23% 17% 29% 24% 6% 1	180
	21st to end	Day	26% 15% 35% 12% 9% 3	290
January	1st to 10th	Night	20% 17% 35% 23% 4	760
	11th to 20th	Night	20% 15% 34% 26% 5%	760
	21st to end	Night	19% 16% 35% 26% 3	836
February	1st to 10th	Night	19% 15% 36% 26% 4	760
	11th to 20th	Night	25% 18% 37% 18% 1	743
	21st to end	Night	21% 15% 38% 23% 3	628
March	1st to 10th	Night	19% 16% 33% 28% 5%	760
	11th to 20th	Night	20% 15% 34% 24% 7% 1	760
	21st to end	Night	20% 13% 39% 23% 5%	836
April	1st to 10th	Night	17% 17% 35% 24% 6%	760
	11th to 20th	Night	16% 12% 34% 27% 12%	751
	21st to end	Night	16% 7% 38% 30% 8%	760
May	1st to 10th	Night	16% 9% 33% 29% 13% 1	573
	11th to 20th	Night	19% 6% 24% 32% 18% 1	561
	21st to end	Night	15% 3 13% 36% 30% 3	617
June	1st to 10th	Night	10% 3 19% 40% 27% 1	509
	11th to 20th	Night	10% 2 15% 40% 29% 4	419
	21st to end	Night	9% 3 14% 42% 29% 3	570
July	1st to 10th	Night	9% 1 10% 39% 35% 5%	555
	11th to 20th	Night	5% 2 9% 37% 41% 6%	552
	21st to end	Night	9% 3 13% 39% 32% 5%	624
August	1st to 10th	Night	13% 2 9% 40% 31% 5%	567
	11th to 20th	Night	11% 3 9% 37% 36% 3	594
	21st to end	Night	10% 2 11% 34% 36% 7%	836
September	1st to 10th	Night	15% 2 9% 33% 35% 5%	760
	11th to 20th	Night	18% 3 13% 29% 33% 5%	760
	21st to end	Night	26% 4 17% 31% 21% 2	760
October	1st to 10th	Night	17% 3 19% 29% 26% 6%	760
	11th to 20th	Night	15% 8% 25% 31% 19% 1	760
	21st to end	Night	15% 9% 24% 34% 17% 2	836
November	1st to 10th	Night	15% 7% 27% 34% 15% 2	780
	11th to 20th	Night	17% 11% 29% 32% 11%	800
	21st to end	Night	14% 11% 31% 32% 11% 1	789
December	1st to 10th	Night	21% 13% 33% 27% 7%	760
	11th to 20th	Night	18% 10% 34% 32% 6%	760
	21st to end	Night	23% 12% 27% 33% 5%	836

Page generated at 2024-11-25 00:22:20. Version ac07

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