Sky Pony Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sky Pony Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	3 3 1 4 3 4 4 4 6% 7% 60%	133986
	Night	3 3 1 4 3 3 4 3 5% 8% 63%	132421
Transparency	Day	19% 6% 9% 17% 25% 24%	129098
	Night	18% 5% 10% 17% 25% 25%	128312
Seeing	Day	7% 11% 25% 30% 20% 5%	15756
	Night	6% 8% 24% 38% 22% 2	25846

By Month

Percentage Cloud Cover SW (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	3 3 1 3 2 2 4 4 5% 6% 67%	4537
	11th to 20th	Day	1 2 1 2 2 2 2 3 5% 7% 74%	4540
	21st to end	Day	2 3 1 4 3 4 4 4 5% 6% 65%	4994
February	1st to 10th	Day	2 4 1 4 5% 4 4 3 5% 6% 63%	2000
	11th to 20th	Day	3 3 1 4 3 4 4 3 4 7% 63%	1949
	21st to end	Day	2 2 1 4 2 3 3 3 5% 7% 67%	1650
March	1st to 10th	Day	2 3 2 4 3 3 4 3 6% 8% 62%	4500
	11th to 20th	Day	2 4 2 3 3 3 4 3 5% 6% 65%	4880
	21st to end	Day	2 3 2 4 3 3 4 4 6% 8% 61%	5911
April	1st to 10th	Day	3 3 1 4 3 3 4 4 6% 7% 64%	2400
	11th to 20th	Day	3 3 2 4 4 3 4 3 5% 6% 64%	2371
	21st to end	Day	2 3 1 3 2 2 3 2 4 6% 71%	2400
May	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 76%	5440
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 7% 67%	5405
	21st to end	Day	2 2 1 3 3 3 4 4 6% 8% 66%	6305
June	1st to 10th	Day	2 2 1 3 3 4 5% 4 8% 8% 61%	2600
	11th to 20th	Day	3 2 1 4 4 4 5% 5% 8% 8% 57%	2600
	21st to end	Day	6% 4 2 5% 5% 4 5% 5% 8% 9% 47%	2587
July	1st to 10th	Day	7% 4 2 5% 4 5% 5% 5% 7% 9% 47%	5439
	11th to 20th	Day	3 2 1 4 5% 5% 8% 6% 9% 11% 47%	5440
	21st to end	Day	4 4 2 6% 6% 6% 8% 6% 9% 11% 39%	5922
August	1st to 10th	Day	2 2 1 4 3 5% 6% 6% 9% 11% 51%	5348
	11th to 20th	Day	3 3 2 7% 7% 7% 7% 6% 9% 11% 36%	5366
	21st to end	Day	4 3 2 6% 5% 6% 6% 5% 7% 8% 48%	5984
September	1st to 10th	Day	10% 6% 2 7% 6% 5% 6% 5% 6% 8% 40%	2400
	11th to 20th	Day	8% 7% 3 8% 5% 5% 6% 5% 7% 8% 39%	2268
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 51%	2090
October	1st to 10th	Day	3 3 1 3 2 2 4 3 4 5% 70%	3480
	11th to 20th	Day	4 2 1 4 3 3 3 3 4 6% 67%	3215
	21st to end	Day	2 2 1 2 1 1 1 2 4 5% 79%	3438
November	1st to 10th	Day	4 3 1 2 2 2 4 2 4 6% 70%	1910
	11th to 20th	Day	2 3 2 4 3 3 4 3 4 5% 67%	1800
	21st to end	Day	5% 4 2 4 3 3 4 3 5% 5% 63%	1800
December	1st to 10th	Day	4 6% 2 5% 4 3 4 3 5% 6% 58%	2940
	11th to 20th	Day	1 2 2 4 4 4 3 3 5% 6% 67%	3391
	21st to end	Day	2 2 1 2 2 2 2 2 5% 5% 75%	4686
January	1st to 10th	Night	2 3 2 4 3 3 4 3 5% 5% 67%	5428
	11th to 20th	Night	2 2 1 3 3 3 3 2 5% 5% 73%	5440
	21st to end	Night	2 3 1 3 3 4 4 4 5% 8% 62%	5984
February	1st to 10th	Night	3 3 1 4 3 2 4 4 5% 7% 64%	2400
	11th to 20th	Night	3 5% 1 5% 3 4 4 3 4 7% 60%	2338
	21st to end	Night	3 3 1 3 3 3 4 3 5% 7% 64%	1980
March	1st to 10th	Night	2 2 1 3 2 3 5% 3 6% 9% 64%	5374
	11th to 20th	Night	3 6% 2 3 3 3 4 3 4 5% 64%	5098
	21st to end	Night	2 3 1 4 3 3 3 3 5% 6% 66%	5042
April	1st to 10th	Night	4 3 2 4 3 4 4 4 5% 6% 61%	2000
	11th to 20th	Night	3 4 2 3 3 3 4 3 6% 7% 62%	1977
	21st to end	Night	2 2 1 3 3 2 3 3 4 5% 72%	2000
May	1st to 10th	Night	1 3 1 3 2 2 3 2 3 4 75%	4540
	11th to 20th	Night	3 4 1 4 3 4 3 3 5% 6% 63%	4510
	21st to end	Night	3 3 1 4 4 4 4 4 6% 5% 61%	4570
June	1st to 10th	Night	2 2 2 4 3 4 5% 5% 7% 11% 56%	1800
	11th to 20th	Night	4 3 1 4 4 5% 5% 5% 8% 9% 54%	1800
	21st to end	Night	5% 4 2 5% 3 5% 5% 5% 7% 9% 50%	1796
July	1st to 10th	Night	6% 4 2 5% 4 4 4 4 7% 11% 49%	4470
	11th to 20th	Night	2 2 1 2 2 3 4 4 7% 12% 62%	4540
	21st to end	Night	3 4 1 5% 4 5% 5% 5% 8% 14% 46%	4951
August	1st to 10th	Night	1 1 2 3 3 4 4 8% 12% 62%	4464
	11th to 20th	Night	1 2 1 4 4 4 6% 6% 11% 16% 46%	4483
	21st to end	Night	3 3 1 4 3 3 4 4 6% 10% 59%	4993
September	1st to 10th	Night	7% 5% 2 5% 4 4 5% 4 7% 8% 47%	2000
	11th to 20th	Night	6% 5% 1 6% 4 5% 6% 4 8% 9% 45%	2085
	21st to end	Night	5% 5% 2 5% 3 5% 5% 5% 6% 8% 52%	2090
October	1st to 10th	Night	2 2 1 3 3 3 2 2 4 5% 73%	3480
	11th to 20th	Night	4 3 2 4 3 3 3 3 4 6% 66%	3705
	21st to end	Night	2 2 1 2 1 2 2 2 2 4 81%	4120
November	1st to 10th	Night	4 3 1 3 2 2 2 2 4 5% 70%	2365
	11th to 20th	Night	3 3 2 4 3 3 3 2 4 6% 67%	2600
	21st to end	Night	4 4 2 4 3 3 4 3 5% 6% 64%	2600
December	1st to 10th	Night	5% 5% 3 6% 4 4 4 3 5% 6% 56%	4250
	11th to 20th	Night	2 3 2 4 3 3 3 2 4 6% 68%	4816
	21st to end	Night	2 2 1 2 2 2 3 2 3 4 77%	6332

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	13% 4 5% 17% 27% 34%	4538
	11th to 20th	Day	10% 3 4 17% 40% 26%	4540
	21st to end	Day	16% 4 6% 17% 31% 25%	4994
February	1st to 10th	Day	19% 4 7% 14% 23% 33%	2000
	11th to 20th	Day	20% 4 7% 15% 27% 27%	1959
	21st to end	Day	15% 3 5% 13% 30% 33%	1650
March	1st to 10th	Day	16% 4 5% 9% 22% 45%	4500
	11th to 20th	Day	16% 5% 6% 10% 25% 38%	4880
	21st to end	Day	17% 4 6% 9% 29% 34%	5911
April	1st to 10th	Day	18% 3 7% 13% 27% 33%	2400
	11th to 20th	Day	18% 4 7% 11% 27% 33%	2374
	21st to end	Day	13% 3 6% 12% 33% 32%	2400
May	1st to 10th	Day	11% 3 5% 11% 28% 42%	5440
	11th to 20th	Day	15% 4 6% 13% 27% 35%	5408
	21st to end	Day	13% 6% 9% 15% 17% 39%	6306
June	1st to 10th	Day	15% 6% 14% 22% 27% 16%	2600
	11th to 20th	Day	18% 6% 10% 18% 27% 21%	2600
	21st to end	Day	28% 8% 11% 23% 18% 12%	2587
July	1st to 10th	Day	28% 9% 15% 27% 19% 2	5381
	11th to 20th	Day	22% 11% 21% 31% 13% 2	5377
	21st to end	Day	30% 11% 19% 22% 16% 2	5752
August	1st to 10th	Day	21% 10% 16% 28% 23% 2	3892
	11th to 20th	Day	28% 9% 17% 25% 18% 3	3882
	21st to end	Day	29% 11% 15% 29% 15% 2	4311
September	1st to 10th	Day	37% 10% 13% 17% 13% 10%	2400
	11th to 20th	Day	35% 11% 13% 17% 17% 7%	2268
	21st to end	Day	29% 6% 10% 20% 22% 13%	2090
October	1st to 10th	Day	13% 5% 6% 14% 26% 36%	3480
	11th to 20th	Day	17% 5% 7% 19% 23% 29%	3215
	21st to end	Day	9% 1 3 13% 47% 26%	3438
November	1st to 10th	Day	15% 5% 7% 18% 29% 26%	1910
	11th to 20th	Day	17% 5% 8% 20% 29% 23%	1800
	21st to end	Day	21% 4 7% 17% 30% 20%	1800
December	1st to 10th	Day	26% 3 6% 18% 28% 19%	2940
	11th to 20th	Day	17% 4 5% 17% 35% 23%	3389
	21st to end	Day	10% 3 5% 11% 38% 33%	4686
January	1st to 10th	Night	16% 3 4 12% 34% 31%	5428
	11th to 20th	Night	12% 3 5% 16% 31% 33%	5440
	21st to end	Night	18% 5% 6% 16% 32% 23%	5984
February	1st to 10th	Night	17% 3 6% 15% 23% 35%	2400
	11th to 20th	Night	23% 5% 8% 11% 26% 27%	2338
	21st to end	Night	18% 4 5% 10% 26% 36%	1980
March	1st to 10th	Night	14% 3 5% 9% 22% 47%	5374
	11th to 20th	Night	15% 8% 8% 8% 23% 39%	5098
	21st to end	Night	17% 4 5% 10% 27% 36%	5042
April	1st to 10th	Night	21% 5% 7% 11% 27% 29%	2000
	11th to 20th	Night	19% 5% 7% 13% 24% 32%	1977
	21st to end	Night	13% 4 7% 16% 25% 35%	2000
May	1st to 10th	Night	12% 3 5% 14% 24% 42%	4537
	11th to 20th	Night	18% 6% 7% 15% 23% 32%	4511
	21st to end	Night	20% 5% 9% 14% 16% 36%	4571
June	1st to 10th	Night	18% 8% 14% 25% 22% 14%	1800
	11th to 20th	Night	22% 6% 10% 19% 26% 17%	1800
	21st to end	Night	26% 7% 15% 21% 19% 12%	1796
July	1st to 10th	Night	26% 9% 18% 32% 13% 2	4420
	11th to 20th	Night	13% 6% 24% 39% 15% 2	4480
	21st to end	Night	24% 10% 21% 29% 15% 1	4808
August	1st to 10th	Night	15% 8% 17% 33% 25% 3	3244
	11th to 20th	Night	18% 9% 23% 31% 17% 2	3243
	21st to end	Night	21% 8% 21% 33% 14% 3	3597
September	1st to 10th	Night	31% 9% 15% 19% 16% 10%	2000
	11th to 20th	Night	29% 11% 17% 19% 15% 8%	2085
	21st to end	Night	26% 7% 13% 20% 21% 12%	2090
October	1st to 10th	Night	13% 5% 8% 12% 24% 38%	3480
	11th to 20th	Night	18% 5% 11% 16% 19% 31%	3705
	21st to end	Night	10% 2 4 13% 44% 28%	4120
November	1st to 10th	Night	15% 3 6% 14% 35% 26%	2365
	11th to 20th	Night	16% 4 6% 20% 28% 25%	2600
	21st to end	Night	20% 4 7% 16% 31% 22%	2600
December	1st to 10th	Night	28% 4 6% 15% 27% 20%	4250
	11th to 20th	Night	16% 3 5% 13% 34% 29%	4817
	21st to end	Night	12% 2 4 12% 39% 31%	6332

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	11% 21% 32% 27% 8%	300
	11th to 20th	Day	8% 21% 36% 24% 10%	300
	21st to end	Day	6% 29% 31% 25% 7% 2	330
February	1st to 10th	Day	8% 18% 35% 24% 14% 1	300
	11th to 20th	Day	14% 20% 38% 21% 8%	300
	21st to end	Day	8% 29% 41% 18% 5%	249
March	1st to 10th	Day	12% 21% 42% 18% 8%	300
	11th to 20th	Day	12% 24% 39% 18% 5% 2	445
	21st to end	Day	9% 27% 43% 17% 4	550
April	1st to 10th	Day	9% 22% 42% 20% 7% 1	500
	11th to 20th	Day	9% 23% 45% 19% 4	492
	21st to end	Day	7% 21% 42% 26% 3	500
May	1st to 10th	Day	7% 20% 39% 26% 7% 1	503
	11th to 20th	Day	7% 14% 34% 35% 8% 1	528
	21st to end	Day	4 7% 38% 39% 11% 1	726
June	1st to 10th	Day	2 4 22% 46% 23% 4	730
	11th to 20th	Day	2 2 18% 49% 25% 3	730
	21st to end	Day	6% 3 12% 35% 37% 7%	717
July	1st to 10th	Day	10% 1 9% 31% 35% 15%	526
	11th to 20th	Day	4 4 32% 45% 14%	524
	21st to end	Day	4 1 6% 33% 43% 13%	575
August	1st to 10th	Day	3 1 4 28% 44% 19%	527
	11th to 20th	Day	6% 3 9% 31% 38% 13%	517
	21st to end	Day	9% 3 7% 28% 39% 15%	583
September	1st to 10th	Day	10% 3 11% 36% 32% 8%	530
	11th to 20th	Day	9% 3 12% 36% 30% 10%	414
	21st to end	Day	10% 3 13% 36% 30% 10%	300
October	1st to 10th	Day	11% 3 17% 35% 30% 5%	300
	11th to 20th	Day	7% 6% 27% 40% 17% 4	300
	21st to end	Day	7% 14% 27% 27% 19% 7%	330
November	1st to 10th	Day	10% 11% 29% 32% 14% 4	300
	11th to 20th	Day	7% 14% 27% 31% 16% 5%	300
	21st to end	Day	12% 21% 32% 21% 11% 3	300
December	1st to 10th	Day	12% 15% 29% 29% 12% 2	300
	11th to 20th	Day	7% 19% 36% 29% 8% 1	300
	21st to end	Day	8% 22% 36% 27% 7%	330
January	1st to 10th	Night	7% 11% 34% 34% 12% 2	800
	11th to 20th	Night	8% 11% 32% 34% 14% 1	800
	21st to end	Night	6% 13% 34% 34% 12% 1	880
February	1st to 10th	Night	6% 13% 30% 34% 15% 2	800
	11th to 20th	Night	8% 11% 35% 36% 9%	784
	21st to end	Night	7% 15% 40% 34% 4	660
March	1st to 10th	Night	8% 13% 33% 34% 11% 1	800
	11th to 20th	Night	9% 14% 32% 30% 14% 1	800
	21st to end	Night	4 12% 41% 34% 7% 1	692
April	1st to 10th	Night	7% 12% 33% 39% 10%	600
	11th to 20th	Night	6% 13% 40% 35% 6%	593
	21st to end	Night	2 13% 37% 40% 8% 1	600
May	1st to 10th	Night	4 9% 35% 41% 11% 1	600
	11th to 20th	Night	6% 8% 29% 45% 11% 1	591
	21st to end	Night	4 6% 29% 47% 14%	650
June	1st to 10th	Night	2 2 21% 54% 20% 1	600
	11th to 20th	Night	4 2 18% 54% 22% 1	600
	21st to end	Night	5% 3 12% 49% 31% 1	600
July	1st to 10th	Night	5% 1 7% 39% 45% 3	585
	11th to 20th	Night	4 4 44% 44% 4	582
	21st to end	Night	3 5% 43% 46% 4	657
August	1st to 10th	Night	3 1 3 29% 58% 6%	597
	11th to 20th	Night	4 1 4 28% 57% 8%	594
	21st to end	Night	6% 1 5% 32% 52% 5%	660
September	1st to 10th	Night	8% 3 5% 31% 47% 5%	600
	11th to 20th	Night	9% 1 7% 40% 40% 3	594
	21st to end	Night	8% 1 10% 39% 37% 5%	570
October	1st to 10th	Night	6% 2 12% 45% 32% 3	570
	11th to 20th	Night	8% 5% 19% 40% 25% 3	713
	21st to end	Night	4 7% 19% 38% 25% 7%	836
November	1st to 10th	Night	6% 4 23% 37% 25% 5%	805
	11th to 20th	Night	5% 8% 23% 41% 22% 2	1000
	21st to end	Night	8% 11% 27% 35% 17% 3	1000
December	1st to 10th	Night	9% 8% 29% 36% 16% 2	1000
	11th to 20th	Night	5% 11% 35% 36% 12% 1	1000
	21st to end	Night	6% 14% 32% 35% 11% 2	1033

Page generated at 2025-09-16 00:49:13. Version ac07

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