South Park Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Park Observatory clear sky chart from 2005-11-06 to 2024-10-24.

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 5% 2 6% 4 4 5% 4 6% 8% 51%	101197
	Night	2 5% 2 5% 3 3 4 4 5% 8% 59%	97806
Transparency	Day	28% 8% 13% 22% 21% 8%	100946
	Night	22% 6% 15% 27% 23% 7%	97647
Seeing	Day	8% 16% 26% 28% 17% 5%	15479
	Night	4 9% 31% 40% 15% 2	25491

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	2 2 5% 3 3 4 3 7% 11% 60%	2538
	11th to 20th	Day	2 1 6% 4 4 5% 5% 8% 8% 56%	2739
	21st to end	Day	4 3 7% 5% 4 5% 3 7% 10% 53%	3146
February	1st to 10th	Day	3 3 5% 3 4 3 4 7% 7% 61%	1710
	11th to 20th	Day	4 1 4 3 3 4 4 5% 9% 64%	1795
	21st to end	Day	3 2 6% 5% 5% 4 4 6% 8% 58%	1570
March	1st to 10th	Day	5% 3 7% 4 4 4 3 6% 8% 55%	3184
	11th to 20th	Day	1 8% 3 8% 5% 5% 4 4 7% 11% 45%	3490
	21st to end	Day	1 5% 2 7% 5% 5% 5% 5% 7% 11% 47%	4000
April	1st to 10th	Day	1 5% 2 5% 3 4 4 4 8% 9% 55%	2280
	11th to 20th	Day	3 9% 3 6% 6% 5% 5% 3 6% 8% 47%	2251
	21st to end	Day	3 8% 2 6% 4 5% 6% 4 6% 9% 47%	2280
May	1st to 10th	Day	4 9% 3 9% 6% 6% 6% 5% 7% 7% 39%	3934
	11th to 20th	Day	5% 7% 2 7% 5% 5% 6% 6% 8% 9% 41%	4388
	21st to end	Day	3 5% 1 4 4 4 6% 5% 7% 9% 51%	4825
June	1st to 10th	Day	5% 4 2 5% 5% 5% 6% 5% 8% 9% 48%	2660
	11th to 20th	Day	6% 4 1 4 4 4 5% 4 5% 7% 54%	2660
	21st to end	Day	4 4 2 4 5% 5% 6% 6% 8% 8% 49%	2660
July	1st to 10th	Day	5% 4 2 5% 4 4 5% 4 6% 6% 54%	4430
	11th to 20th	Day	6% 5% 2 6% 6% 6% 6% 5% 8% 11% 40%	4430
	21st to end	Day	7% 6% 2 6% 6% 6% 6% 5% 6% 8% 43%	4559
August	1st to 10th	Day	9% 7% 2 9% 7% 7% 6% 5% 8% 9% 31%	4092
	11th to 20th	Day	5% 5% 2 6% 5% 6% 7% 6% 8% 8% 41%	3764
	21st to end	Day	5% 5% 2 7% 6% 6% 6% 5% 7% 9% 42%	4180
September	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 4 5% 6% 52%	2280
	11th to 20th	Day	6% 4 1 6% 4 4 5% 3 5% 6% 57%	2280
	21st to end	Day	6% 4 1 4 3 4 3 3 4 6% 63%	2062
October	1st to 10th	Day	5% 4 2 4 4 4 4 4 5% 6% 59%	1900
	11th to 20th	Day	3 4 1 2 3 3 4 3 4 6% 67%	1900
	21st to end	Day	2 5% 2 4 3 2 3 3 5% 7% 64%	2000
November	1st to 10th	Day	1 2 1 3 2 2 3 2 4 6% 74%	1673
	11th to 20th	Day	3 1 3 2 2 2 3 4 8% 73%	1710
	21st to end	Day	1 3 2 4 2 3 3 3 5% 8% 66%	1587
December	1st to 10th	Day	1 3 2 5% 2 3 4 3 5% 8% 64%	1520
	11th to 20th	Day	1 3 2 4 3 3 3 4 7% 11% 59%	1926
	21st to end	Day	3 2 6% 4 4 4 3 6% 10% 58%	2794
January	1st to 10th	Night	2 2 8% 5% 4 4 3 5% 8% 60%	4417
	11th to 20th	Night	2 1 3 4 3 4 4 6% 7% 66%	4261
	21st to end	Night	1 6% 3 7% 3 3 4 3 4 5% 62%	4521
February	1st to 10th	Night	2 2 5% 3 3 4 3 4 8% 65%	2470
	11th to 20th	Night	3 2 6% 3 2 3 3 5% 6% 66%	2270
	21st to end	Night	4 2 5% 3 2 3 2 5% 6% 65%	1884
March	1st to 10th	Night	6% 3 6% 3 4 3 3 4 8% 61%	3677
	11th to 20th	Night	1 11% 5% 7% 3 3 3 3 5% 7% 53%	3490
	21st to end	Night	1 5% 2 6% 4 4 4 4 6% 9% 55%	3645
April	1st to 10th	Night	1 5% 2 4 2 2 4 4 4 8% 65%	1900
	11th to 20th	Night	3 9% 3 5% 3 3 3 4 5% 7% 55%	1877
	21st to end	Night	4 8% 2 5% 4 4 3 2 5% 7% 56%	1900
May	1st to 10th	Night	4 10% 3 5% 4 4 4 3 5% 7% 52%	3028
	11th to 20th	Night	7% 10% 3 6% 4 3 4 4 5% 7% 47%	2517
	21st to end	Night	5% 7% 2 4 3 3 3 2 5% 7% 59%	2762
June	1st to 10th	Night	3 4 1 3 3 3 3 3 5% 9% 62%	1520
	11th to 20th	Night	5% 2 1 3 2 3 3 4 5% 8% 65%	1520
	21st to end	Night	4 3 1 3 3 3 4 4 6% 10% 59%	1520
July	1st to 10th	Night	4 5% 2 5% 4 3 3 4 6% 7% 58%	2540
	11th to 20th	Night	2 3 1 4 4 4 6% 5% 8% 9% 54%	2540
	21st to end	Night	4 4 1 4 3 5% 5% 5% 7% 10% 51%	3000
August	1st to 10th	Night	7% 6% 2 6% 4 5% 5% 5% 8% 11% 40%	2847
	11th to 20th	Night	4 4 1 4 4 4 6% 6% 9% 11% 47%	3073
	21st to end	Night	4 4 2 7% 6% 6% 6% 5% 8% 9% 44%	3487
September	1st to 10th	Night	5% 4 1 4 3 4 4 5% 6% 8% 55%	1900
	11th to 20th	Night	6% 4 1 4 3 3 4 3 5% 7% 60%	1900
	21st to end	Night	6% 5% 1 4 2 3 3 2 4 6% 64%	2111
October	1st to 10th	Night	6% 4 1 4 3 3 3 3 4 5% 64%	2280
	11th to 20th	Night	2 3 1 2 2 2 2 3 3 5% 74%	2280
	21st to end	Night	3 5% 2 4 2 2 2 3 5% 6% 66%	2412
November	1st to 10th	Night	1 3 1 2 2 2 2 3 4 7% 73%	2395
	11th to 20th	Night	3 1 2 2 2 2 2 4 7% 74%	2470
	21st to end	Night	1 5% 1 4 2 2 2 3 5% 7% 66%	2588
December	1st to 10th	Night	3 1 3 3 3 3 3 5% 8% 69%	2660
	11th to 20th	Night	1 3 2 4 2 3 4 4 7% 10% 61%	3271
	21st to end	Night	4 2 6% 4 4 4 3 5% 8% 60%	4873

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	18% 5% 19% 27% 24% 6%	2539
	11th to 20th	Day	20% 6% 26% 25% 19% 4	2739
	21st to end	Day	25% 6% 13% 31% 19% 6%	3146
February	1st to 10th	Day	23% 5% 19% 27% 19% 8%	1710
	11th to 20th	Day	18% 5% 13% 28% 29% 6%	1805
	21st to end	Day	23% 5% 14% 21% 26% 11%	1570
March	1st to 10th	Day	24% 6% 12% 22% 29% 7%	3184
	11th to 20th	Day	30% 12% 11% 31% 13% 3	3490
	21st to end	Day	25% 11% 16% 28% 18% 2	4000
April	1st to 10th	Day	25% 7% 15% 24% 22% 8%	2280
	11th to 20th	Day	35% 6% 13% 21% 20% 4	2254
	21st to end	Day	33% 9% 12% 27% 18% 2	2280
May	1st to 10th	Day	36% 7% 17% 15% 19% 5%	3934
	11th to 20th	Day	36% 11% 15% 20% 16% 2	4392
	21st to end	Day	25% 7% 15% 18% 29% 6%	4825
June	1st to 10th	Day	30% 10% 14% 19% 20% 7%	2660
	11th to 20th	Day	28% 7% 9% 18% 22% 15%	2660
	21st to end	Day	29% 8% 10% 20% 21% 12%	2660
July	1st to 10th	Day	26% 9% 9% 13% 18% 25%	4361
	11th to 20th	Day	31% 11% 13% 21% 16% 8%	4355
	21st to end	Day	34% 11% 14% 15% 12% 14%	4415
August	1st to 10th	Day	42% 12% 18% 13% 12% 4	4078
	11th to 20th	Day	35% 11% 13% 14% 19% 8%	3800
	21st to end	Day	33% 9% 14% 16% 20% 8%	4179
September	1st to 10th	Day	32% 6% 10% 16% 22% 14%	2280
	11th to 20th	Day	27% 6% 12% 18% 27% 10%	2280
	21st to end	Day	24% 5% 7% 24% 33% 8%	2062
October	1st to 10th	Day	25% 7% 8% 20% 29% 11%	1900
	11th to 20th	Day	19% 5% 7% 25% 34% 10%	1900
	21st to end	Day	22% 4 8% 31% 27% 9%	2000
November	1st to 10th	Day	14% 4 12% 23% 36% 11%	1673
	11th to 20th	Day	12% 4 11% 36% 28% 9%	1710
	21st to end	Day	18% 4 11% 29% 26% 12%	1587
December	1st to 10th	Day	18% 8% 15% 30% 22% 6%	1520
	11th to 20th	Day	20% 5% 16% 32% 24% 3	1924
	21st to end	Day	20% 6% 13% 25% 26% 10%	2794
January	1st to 10th	Night	23% 5% 14% 31% 24% 4	4417
	11th to 20th	Night	13% 6% 20% 31% 21% 8%	4261
	21st to end	Night	24% 6% 15% 28% 23% 4	4521
February	1st to 10th	Night	19% 4 16% 33% 22% 6%	2470
	11th to 20th	Night	19% 5% 13% 30% 27% 6%	2270
	21st to end	Night	20% 3 10% 29% 28% 10%	1884
March	1st to 10th	Night	22% 4 11% 24% 33% 6%	3677
	11th to 20th	Night	31% 7% 12% 29% 18% 3	3490
	21st to end	Night	24% 6% 19% 32% 16% 2	3645
April	1st to 10th	Night	19% 5% 15% 30% 25% 5%	1900
	11th to 20th	Night	29% 5% 12% 30% 20% 4	1877
	21st to end	Night	29% 5% 13% 31% 19% 1	1900
May	1st to 10th	Night	28% 6% 16% 23% 21% 6%	3028
	11th to 20th	Night	35% 8% 17% 25% 15% 1	2518
	21st to end	Night	25% 6% 14% 23% 28% 4	2762
June	1st to 10th	Night	21% 6% 20% 28% 17% 9%	1520
	11th to 20th	Night	18% 6% 14% 22% 25% 16%	1520
	21st to end	Night	20% 7% 14% 24% 23% 12%	1520
July	1st to 10th	Night	24% 8% 11% 20% 17% 19%	2500
	11th to 20th	Night	20% 9% 20% 31% 13% 7%	2492
	21st to end	Night	22% 11% 23% 23% 7% 14%	2906
August	1st to 10th	Night	34% 12% 22% 18% 10% 4	2838
	11th to 20th	Night	25% 12% 22% 16% 19% 7%	3103
	21st to end	Night	31% 11% 17% 19% 19% 3	3487
September	1st to 10th	Night	25% 8% 13% 23% 22% 9%	1900
	11th to 20th	Night	23% 6% 14% 22% 22% 13%	1900
	21st to end	Night	23% 5% 9% 28% 28% 6%	2111
October	1st to 10th	Night	23% 7% 11% 23% 26% 11%	2280
	11th to 20th	Night	13% 4 10% 28% 34% 11%	2280
	21st to end	Night	20% 4 11% 29% 29% 8%	2412
November	1st to 10th	Night	13% 4 12% 27% 33% 11%	2395
	11th to 20th	Night	11% 5% 11% 35% 29% 8%	2470
	21st to end	Night	18% 4 11% 29% 27% 10%	2588
December	1st to 10th	Night	16% 6% 18% 30% 24% 7%	2660
	11th to 20th	Night	18% 5% 17% 29% 28% 3	3272
	21st to end	Night	23% 5% 14% 24% 24% 10%	4873

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	4 20% 29% 31% 10% 5%	270
	11th to 20th	Day	8% 24% 33% 28% 6% 1	270
	21st to end	Day	2 19% 38% 29% 10% 3	297
February	1st to 10th	Day	1 39% 33% 23% 2 1	270
	11th to 20th	Day	3 34% 34% 24% 5% 1	270
	21st to end	Day	7% 32% 35% 22% 4	225
March	1st to 10th	Day	3 27% 33% 24% 12% 1	298
	11th to 20th	Day	6% 21% 35% 27% 12%	460
	21st to end	Day	6% 31% 36% 20% 6% 1	506
April	1st to 10th	Day	7% 29% 33% 24% 6% 1	460
	11th to 20th	Day	12% 36% 28% 16% 6% 2	452
	21st to end	Day	10% 25% 33% 23% 6% 2	460
May	1st to 10th	Day	11% 25% 31% 22% 9% 2	510
	11th to 20th	Day	10% 15% 25% 32% 15% 4	675
	21st to end	Day	9% 16% 21% 30% 19% 4	734
June	1st to 10th	Day	6% 13% 22% 29% 22% 8%	680
	11th to 20th	Day	8% 12% 24% 35% 17% 5%	680
	21st to end	Day	5% 9% 25% 32% 22% 7%	680
July	1st to 10th	Day	8% 4 13% 35% 30% 10%	671
	11th to 20th	Day	7% 3 11% 33% 34% 11%	668
	21st to end	Day	10% 4 16% 27% 33% 10%	597
August	1st to 10th	Day	13% 5% 20% 30% 23% 9%	487
	11th to 20th	Day	10% 6% 20% 34% 20% 10%	477
	21st to end	Day	11% 6% 22% 26% 25% 10%	539
September	1st to 10th	Day	10% 7% 22% 28% 23% 9%	490
	11th to 20th	Day	7% 9% 27% 30% 21% 6%	490
	21st to end	Day	6% 12% 20% 29% 22% 11%	310
October	1st to 10th	Day	7% 16% 22% 21% 24% 10%	300
	11th to 20th	Day	8% 19% 22% 31% 16% 4	300
	21st to end	Day	8% 20% 27% 28% 15% 2	306
November	1st to 10th	Day	6% 19% 33% 26% 11% 5%	270
	11th to 20th	Day	7% 19% 30% 32% 9% 3	270
	21st to end	Day	4 17% 39% 30% 8% 2	270
December	1st to 10th	Day	8% 21% 30% 31% 7% 3	270
	11th to 20th	Day	5% 20% 39% 28% 7% 2	270
	21st to end	Day	8% 24% 35% 22% 8% 2	297
January	1st to 10th	Night	1 15% 37% 35% 10% 2	950
	11th to 20th	Night	2 18% 38% 33% 7% 2	846
	21st to end	Night	2 11% 40% 38% 8% 1	836
February	1st to 10th	Night	13% 50% 31% 6% 1	760
	11th to 20th	Night	2 15% 44% 33% 7%	744
	21st to end	Night	2 10% 47% 39% 2	628
March	1st to 10th	Night	2 11% 39% 40% 7% 1	760
	11th to 20th	Night	3 7% 36% 43% 9% 1	760
	21st to end	Night	4 10% 45% 36% 5%	730
April	1st to 10th	Night	4 13% 43% 36% 4	570
	11th to 20th	Night	6% 12% 38% 35% 8% 1	563
	21st to end	Night	9% 9% 34% 39% 8% 1	570
May	1st to 10th	Night	9% 8% 33% 38% 11% 1	570
	11th to 20th	Night	11% 6% 19% 47% 15% 2	561
	21st to end	Night	10% 6% 24% 40% 18% 2	617
June	1st to 10th	Night	4 4 21% 45% 24% 2	570
	11th to 20th	Night	5% 4 25% 50% 14% 2	570
	21st to end	Night	5% 2 18% 45% 28% 3	570
July	1st to 10th	Night	6% 2 9% 39% 38% 5%	555
	11th to 20th	Night	4 1 4 43% 44% 4	552
	21st to end	Night	6% 1 6% 37% 46% 5%	624
August	1st to 10th	Night	10% 2 7% 39% 38% 4	567
	11th to 20th	Night	7% 2 9% 45% 33% 5%	564
	21st to end	Night	8% 1 9% 41% 35% 5%	627
September	1st to 10th	Night	5% 2 11% 49% 27% 6%	570
	11th to 20th	Night	7% 1 17% 48% 24% 3	570
	21st to end	Night	7% 4 24% 43% 18% 4	603
October	1st to 10th	Night	6% 4 28% 42% 17% 3	760
	11th to 20th	Night	3 6% 33% 43% 13% 2	760
	21st to end	Night	5% 7% 31% 44% 11% 2	804
November	1st to 10th	Night	2 10% 35% 41% 11% 2	915
	11th to 20th	Night	3 13% 38% 39% 6% 1	950
	21st to end	Night	3 12% 36% 40% 9% 1	950
December	1st to 10th	Night	3 14% 40% 37% 6% 1	950
	11th to 20th	Night	2 13% 40% 37% 8% 1	950
	21st to end	Night	3 18% 40% 32% 7% 1	1045

Page generated at 2024-10-21 00:20:04. Version ac07

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