SGPalisadeCO Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SGPalisadeCO Observatory clear sky chart from 2005-11-06 to 2026-10-29.

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 4 2 5% 4 4 4 4 6% 8% 57%	158218
	Night	4 6% 2 6% 4 4 4 4 6% 7% 55%	151482
Transparency	Day	22% 7% 11% 23% 23% 14%	153081
	Night	26% 7% 11% 23% 22% 11%	147627
Seeing	Day	7% 12% 28% 32% 18% 3	18052
	Night	7% 6% 23% 39% 22% 3	28153

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 8% 3 8% 6% 5% 5% 5% 6% 8% 44%	5140
	11th to 20th	Day	2 6% 2 6% 4 3 3 3 5% 5% 60%	5340
	21st to end	Day	3 7% 2 7% 4 3 3 3 4 5% 59%	5844
February	1st to 10th	Day	3 8% 2 8% 4 4 4 4 7% 8% 48%	1890
	11th to 20th	Day	5% 11% 3 7% 5% 4 5% 3 7% 7% 42%	1845
	21st to end	Day	5% 9% 3 8% 5% 4 4 3 4 6% 49%	1740
March	1st to 10th	Day	3 8% 3 8% 5% 4 5% 4 5% 6% 49%	5064
	11th to 20th	Day	2 10% 3 10% 5% 5% 4 5% 6% 7% 42%	5110
	21st to end	Day	4 10% 4 9% 7% 5% 5% 4 5% 7% 41%	5607
April	1st to 10th	Day	6% 6% 2 5% 4 5% 4 4 5% 7% 51%	2499
	11th to 20th	Day	5% 7% 3 7% 4 3 5% 4 6% 6% 50%	2491
	21st to end	Day	4 5% 2 5% 4 4 6% 4 7% 8% 52%	2557
May	1st to 10th	Day	3 5% 2 6% 4 5% 5% 4 7% 8% 51%	7626
	11th to 20th	Day	3 4 2 5% 3 4 5% 4 6% 8% 56%	7673
	21st to end	Day	3 3 1 4 3 3 4 4 6% 9% 59%	9026
June	1st to 10th	Day	2 3 1 4 2 3 4 3 6% 8% 63%	2940
	11th to 20th	Day	2 2 1 3 3 3 4 3 4 6% 70%	2940
	21st to end	Day	2 2 1 3 3 2 3 3 6% 7% 69%	2940
July	1st to 10th	Day	1 1 1 2 2 3 3 3 4 5% 75%	8217
	11th to 20th	Day	1 1 1 2 2 3 5% 5% 9% 14% 58%	7650
	21st to end	Day	1 2 1 3 2 4 5% 5% 9% 11% 57%	8304
August	1st to 10th	Day	1 1 1 3 3 3 5% 4 7% 10% 62%	7549
	11th to 20th	Day	1 1 1 3 3 4 5% 4 7% 10% 61%	7513
	21st to end	Day	3 3 2 5% 4 5% 6% 6% 8% 11% 48%	7751
September	1st to 10th	Day	4 2 1 3 3 3 4 3 5% 6% 65%	2520
	11th to 20th	Day	3 3 1 4 4 4 5% 4 5% 6% 62%	2454
	21st to end	Day	5% 2 1 3 2 3 3 3 4 6% 67%	2245
October	1st to 10th	Day	4 2 1 2 2 2 2 2 3 4 77%	3370
	11th to 20th	Day	4 3 1 5% 3 4 5% 5% 7% 10% 55%	3350
	21st to end	Day	5% 4 2 4 3 2 3 3 5% 6% 64%	3628
November	1st to 10th	Day	4 3 1 4 4 3 3 3 5% 7% 64%	2043
	11th to 20th	Day	5% 5% 2 5% 3 3 3 3 4 6% 61%	1774
	21st to end	Day	4 7% 2 5% 3 3 2 3 5% 6% 60%	1680
December	1st to 10th	Day	3 6% 2 5% 2 3 3 2 4 6% 64%	2700
	11th to 20th	Day	4 6% 3 6% 3 3 3 3 6% 9% 54%	3106
	21st to end	Day	4 10% 3 7% 4 4 5% 4 6% 7% 46%	4092
January	1st to 10th	Night	2 10% 4 10% 6% 5% 5% 4 6% 7% 42%	7823
	11th to 20th	Night	2 8% 3 6% 3 3 2 3 5% 5% 59%	7650
	21st to end	Night	4 9% 3 6% 3 3 3 2 4 5% 58%	8370
February	1st to 10th	Night	3 7% 3 6% 4 4 5% 4 6% 7% 50%	2730
	11th to 20th	Night	5% 10% 4 7% 6% 5% 4 3 6% 6% 44%	2662
	21st to end	Night	4 9% 3 7% 4 4 4 4 5% 7% 48%	2059
March	1st to 10th	Night	3 11% 3 8% 4 5% 4 3 4 5% 49%	5050
	11th to 20th	Night	4 9% 3 6% 4 4 4 3 5% 8% 48%	5110
	21st to end	Night	5% 11% 5% 9% 6% 4 5% 4 5% 6% 40%	5610
April	1st to 10th	Night	6% 9% 2 8% 5% 3 4 4 5% 6% 48%	2119
	11th to 20th	Night	6% 7% 3 8% 4 5% 5% 4 5% 7% 46%	2077
	21st to end	Night	7% 7% 3 7% 4 4 4 4 6% 7% 48%	2058
May	1st to 10th	Night	6% 6% 3 6% 4 5% 5% 4 7% 7% 48%	5321
	11th to 20th	Night	5% 5% 3 6% 4 4 5% 4 7% 7% 52%	5219
	21st to end	Night	5% 4 2 5% 4 3 4 4 6% 8% 57%	5181
June	1st to 10th	Night	2 3 1 3 3 3 4 3 5% 8% 64%	1680
	11th to 20th	Night	4 4 1 4 3 3 4 3 4 6% 64%	1680
	21st to end	Night	2 2 1 3 2 3 4 4 5% 7% 67%	1680
July	1st to 10th	Night	1 2 1 3 3 3 4 4 5% 6% 66%	4740
	11th to 20th	Night	1 2 1 5% 4 5% 6% 5% 9% 10% 50%	5340
	21st to end	Night	1 3 1 5% 4 4 5% 5% 8% 11% 53%	5805
August	1st to 10th	Night	2 2 1 4 3 4 5% 5% 7% 9% 58%	5273
	11th to 20th	Night	2 2 1 4 4 4 5% 4 6% 9% 58%	5343
	21st to end	Night	2 2 1 4 4 6% 7% 6% 9% 12% 46%	6465
September	1st to 10th	Night	4 3 1 3 3 3 3 4 5% 7% 65%	2100
	11th to 20th	Night	3 2 1 4 3 3 4 3 6% 6% 64%	2162
	21st to end	Night	5% 3 1 3 3 3 3 2 4 5% 68%	2373
October	1st to 10th	Night	4 2 1 2 2 2 2 2 3 4 76%	4040
	11th to 20th	Night	4 3 2 5% 3 3 4 4 6% 8% 58%	4018
	21st to end	Night	6% 6% 2 4 3 3 2 2 3 5% 64%	4348
November	1st to 10th	Night	4 5% 2 5% 2 3 3 3 4 6% 64%	2460
	11th to 20th	Night	5% 4 2 5% 3 3 3 3 5% 6% 62%	2837
	21st to end	Night	6% 8% 3 5% 3 3 3 2 4 6% 57%	2940
December	1st to 10th	Night	4 6% 2 4 2 2 3 3 3 5% 67%	4710
	11th to 20th	Night	4 7% 2 6% 4 4 4 3 5% 8% 53%	5321
	21st to end	Night	5% 10% 3 8% 4 4 4 3 5% 7% 46%	7128

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	33% 10% 23% 24% 10% 1	5143
	11th to 20th	Day	23% 8% 17% 31% 16% 5%	5340
	21st to end	Day	26% 6% 14% 28% 22% 4	5844
February	1st to 10th	Day	33% 8% 16% 25% 15% 3	1890
	11th to 20th	Day	38% 9% 12% 24% 16% 2	1854
	21st to end	Day	35% 6% 8% 26% 19% 5%	1740
March	1st to 10th	Day	28% 10% 10% 23% 23% 6%	5064
	11th to 20th	Day	34% 10% 14% 25% 15% 3	5110
	21st to end	Day	37% 11% 10% 26% 14% 2	5607
April	1st to 10th	Day	30% 6% 9% 23% 24% 8%	2499
	11th to 20th	Day	31% 8% 9% 22% 25% 6%	2494
	21st to end	Day	26% 7% 10% 23% 27% 6%	2557
May	1st to 10th	Day	23% 11% 10% 22% 29% 6%	7626
	11th to 20th	Day	20% 9% 9% 21% 29% 12%	7676
	21st to end	Day	16% 8% 8% 20% 41% 7%	9027
June	1st to 10th	Day	18% 5% 6% 19% 31% 20%	2940
	11th to 20th	Day	16% 4 5% 10% 24% 40%	2940
	21st to end	Day	14% 4 4 13% 26% 39%	2940
July	1st to 10th	Day	12% 3 4 7% 16% 58%	8149
	11th to 20th	Day	12% 7% 11% 22% 25% 23%	7581
	21st to end	Day	14% 8% 13% 22% 20% 22%	8120
August	1st to 10th	Day	17% 7% 10% 18% 19% 28%	5978
	11th to 20th	Day	19% 9% 12% 26% 21% 13%	5924
	21st to end	Day	21% 11% 13% 24% 18% 13%	6078
September	1st to 10th	Day	19% 5% 8% 16% 25% 27%	2520
	11th to 20th	Day	19% 7% 9% 20% 26% 19%	2454
	21st to end	Day	19% 4 6% 18% 37% 15%	2245
October	1st to 10th	Day	14% 3 5% 17% 35% 27%	3370
	11th to 20th	Day	20% 8% 9% 27% 30% 7%	3350
	21st to end	Day	20% 6% 10% 32% 28% 4	3628
November	1st to 10th	Day	21% 4 10% 29% 31% 5%	2043
	11th to 20th	Day	24% 5% 10% 34% 23% 2	1774
	21st to end	Day	26% 6% 13% 31% 22% 3	1680
December	1st to 10th	Day	21% 5% 16% 42% 15% 1	2700
	11th to 20th	Day	27% 6% 21% 30% 15%	3104
	21st to end	Day	33% 9% 17% 18% 21% 2	4092
January	1st to 10th	Night	37% 10% 18% 23% 11% 1	7824
	11th to 20th	Night	24% 6% 16% 32% 21% 2	7650
	21st to end	Night	28% 5% 14% 24% 24% 4	8370
February	1st to 10th	Night	31% 8% 17% 27% 14% 3	2730
	11th to 20th	Night	37% 8% 12% 24% 17% 3	2663
	21st to end	Night	33% 7% 10% 27% 19% 5%	2059
March	1st to 10th	Night	32% 7% 8% 24% 24% 5%	5050
	11th to 20th	Night	30% 9% 10% 27% 20% 4	5110
	21st to end	Night	37% 11% 10% 26% 14% 2	5610
April	1st to 10th	Night	35% 6% 7% 20% 23% 9%	2119
	11th to 20th	Night	33% 8% 9% 21% 21% 10%	2077
	21st to end	Night	31% 7% 10% 20% 26% 7%	2058
May	1st to 10th	Night	28% 10% 9% 18% 28% 7%	5319
	11th to 20th	Night	24% 10% 10% 22% 25% 11%	5220
	21st to end	Night	21% 8% 8% 20% 35% 9%	5182
June	1st to 10th	Night	16% 6% 8% 17% 30% 23%	1680
	11th to 20th	Night	19% 6% 7% 11% 19% 38%	1680
	21st to end	Night	14% 4 6% 12% 23% 41%	1680
July	1st to 10th	Night	16% 5% 6% 7% 13% 53%	4700
	11th to 20th	Night	21% 8% 11% 19% 21% 21%	5286
	21st to end	Night	20% 7% 12% 18% 20% 22%	5677
August	1st to 10th	Night	20% 8% 11% 13% 16% 33%	4168
	11th to 20th	Night	23% 9% 13% 20% 20% 15%	4208
	21st to end	Night	22% 9% 11% 24% 17% 16%	5069
September	1st to 10th	Night	19% 4 8% 15% 21% 32%	2100
	11th to 20th	Night	18% 5% 10% 19% 23% 24%	2162
	21st to end	Night	19% 5% 6% 16% 32% 21%	2373
October	1st to 10th	Night	14% 3 5% 14% 37% 28%	4040
	11th to 20th	Night	20% 6% 10% 25% 30% 8%	4018
	21st to end	Night	23% 4 6% 34% 29% 4	4348
November	1st to 10th	Night	22% 4 9% 27% 30% 7%	2460
	11th to 20th	Night	22% 6% 9% 32% 27% 3	2837
	21st to end	Night	29% 4 9% 29% 25% 4	2940
December	1st to 10th	Night	20% 4 15% 41% 18% 1	4710
	11th to 20th	Night	28% 7% 15% 38% 12% 1	5322
	21st to end	Night	36% 9% 15% 22% 17% 2	7128

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% 11% 27% 30% 13% 5%	330
	11th to 20th	Day	9% 12% 31% 31% 16% 1	330
	21st to end	Day	8% 6% 31% 40% 12% 3	363
February	1st to 10th	Day	8% 13% 38% 30% 10% 1	330
	11th to 20th	Day	10% 15% 43% 24% 7% 1	330
	21st to end	Day	11% 17% 33% 31% 6% 1	299
March	1st to 10th	Day	11% 23% 29% 22% 12% 1	540
	11th to 20th	Day	9% 19% 34% 24% 12% 2	540
	21st to end	Day	12% 23% 38% 20% 7% 1	594
April	1st to 10th	Day	12% 20% 33% 22% 11% 2	540
	11th to 20th	Day	16% 25% 34% 19% 6% 1	532
	21st to end	Day	11% 19% 37% 21% 11% 1	540
May	1st to 10th	Day	10% 18% 35% 27% 10% 1	543
	11th to 20th	Day	8% 12% 32% 31% 15% 2	593
	21st to end	Day	6% 14% 28% 29% 20% 3	844
June	1st to 10th	Day	3 10% 24% 35% 24% 3	780
	11th to 20th	Day	4 13% 29% 33% 17% 3	780
	21st to end	Day	6% 9% 24% 38% 21% 3	780
July	1st to 10th	Day	2 3 21% 39% 30% 6%	765
	11th to 20th	Day	2 2 18% 40% 34% 4	564
	21st to end	Day	4 3 16% 43% 31% 4	619
August	1st to 10th	Day	4 4 22% 40% 26% 4	567
	11th to 20th	Day	3 5% 16% 43% 28% 6%	557
	21st to end	Day	4 3 22% 38% 26% 6%	627
September	1st to 10th	Day	5% 5% 23% 31% 28% 8%	570
	11th to 20th	Day	4 9% 29% 36% 16% 6%	570
	21st to end	Day	7% 9% 20% 34% 24% 6%	505
October	1st to 10th	Day	8% 11% 19% 23% 27% 13%	360
	11th to 20th	Day	6% 13% 24% 30% 20% 6%	360
	21st to end	Day	8% 9% 30% 30% 20% 3	387
November	1st to 10th	Day	6% 16% 26% 32% 18% 1	330
	11th to 20th	Day	3 13% 33% 33% 14% 4	330
	21st to end	Day	10% 10% 28% 34% 17% 1	330
December	1st to 10th	Day	9% 9% 32% 31% 16% 3	330
	11th to 20th	Day	8% 8% 32% 35% 14% 4	330
	21st to end	Day	12% 12% 32% 33% 10% 2	363
January	1st to 10th	Night	8% 6% 23% 40% 20% 3	919
	11th to 20th	Night	8% 7% 23% 40% 19% 3	840
	21st to end	Night	10% 6% 24% 43% 15% 3	924
February	1st to 10th	Night	8% 7% 29% 42% 13% 2	840
	11th to 20th	Night	11% 7% 33% 36% 12% 2	824
	21st to end	Night	7% 10% 32% 41% 9% 1	692
March	1st to 10th	Night	8% 13% 27% 37% 14% 1	840
	11th to 20th	Night	7% 7% 27% 41% 17% 1	840
	21st to end	Night	8% 10% 30% 36% 14% 2	924
April	1st to 10th	Night	9% 11% 31% 38% 10% 1	649
	11th to 20th	Night	10% 12% 29% 36% 11% 2	623
	21st to end	Night	9% 11% 29% 34% 13% 4	630
May	1st to 10th	Night	10% 7% 28% 40% 13% 2	630
	11th to 20th	Night	9% 7% 21% 38% 22% 4	621
	21st to end	Night	8% 10% 22% 35% 22% 4	683
June	1st to 10th	Night	2 6% 21% 42% 25% 3	630
	11th to 20th	Night	5% 6% 24% 43% 20% 3	630
	21st to end	Night	3 4 20% 41% 29% 3	630
July	1st to 10th	Night	3 1 16% 36% 39% 5%	615
	11th to 20th	Night	2 1 8% 41% 43% 5%	612
	21st to end	Night	2 1 8% 37% 46% 5%	690
August	1st to 10th	Night	5% 3 12% 36% 41% 4	627
	11th to 20th	Night	4 2 11% 42% 37% 5%	624
	21st to end	Night	3 2 12% 40% 37% 7%	693
September	1st to 10th	Night	4 1 17% 41% 32% 5%	630
	11th to 20th	Night	3 3 22% 38% 30% 4	692
	21st to end	Night	6% 5% 18% 33% 31% 7%	840
October	1st to 10th	Night	8% 4 20% 40% 24% 4	840
	11th to 20th	Night	8% 6% 22% 38% 23% 4	840
	21st to end	Night	8% 7% 24% 35% 21% 4	912
November	1st to 10th	Night	6% 7% 24% 38% 23% 2	820
	11th to 20th	Night	6% 7% 25% 42% 17% 3	1044
	21st to end	Night	9% 8% 22% 39% 18% 3	1050
December	1st to 10th	Night	8% 6% 24% 44% 17% 1	1050
	11th to 20th	Night	10% 6% 27% 38% 17% 2	1050
	21st to end	Night	12% 9% 25% 42% 11% 1	1155

Page generated at 2026-10-26 02:37:49. Version ac07

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