Climax Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Climax Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	4 8% 4 11% 6% 5% 4 3 5% 6% 43%	105622
	Night	2 5% 3 9% 6% 5% 4 4 5% 7% 50%	103225
Transparency	Day	38% 6% 10% 20% 19% 7%	105373
	Night	29% 6% 14% 25% 20% 6%	103064
Seeing	Day	16% 24% 29% 19% 10% 2	15665
	Night	8% 17% 29% 30% 14% 1	25805

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	4 4 12% 12% 11% 5% 3 4 7% 38%	2538
	11th to 20th	Day	5% 5% 19% 8% 8% 6% 3 3 4 38%	2773
	21st to end	Day	7% 5% 16% 7% 5% 3 3 4 6% 44%	3146
February	1st to 10th	Day	5% 6% 19% 8% 6% 4 4 4 4 39%	1710
	11th to 20th	Day	5% 5% 15% 10% 6% 4 3 4 6% 43%	1767
	21st to end	Day	5% 5% 19% 7% 7% 4 3 4 5% 41%	1570
March	1st to 10th	Day	7% 7% 19% 7% 3 3 2 4 4 43%	3226
	11th to 20th	Day	1 8% 8% 17% 6% 5% 4 3 5% 6% 36%	3490
	21st to end	Day	1 12% 8% 19% 8% 6% 4 2 4 5% 30%	3969
April	1st to 10th	Day	2 11% 5% 12% 6% 4 4 3 5% 6% 43%	2280
	11th to 20th	Day	1 15% 8% 15% 7% 4 4 3 4 6% 34%	2251
	21st to end	Day	2 17% 6% 13% 7% 4 5% 3 4 5% 33%	2280
May	1st to 10th	Day	3 15% 10% 13% 6% 6% 5% 4 5% 5% 28%	3967
	11th to 20th	Day	3 13% 4 9% 5% 5% 6% 5% 6% 7% 38%	4388
	21st to end	Day	3 8% 3 8% 4 4 5% 4 7% 8% 46%	4825
June	1st to 10th	Day	6% 7% 2 6% 5% 4 5% 4 7% 8% 45%	2660
	11th to 20th	Day	7% 8% 2 5% 4 4 5% 3 5% 6% 50%	2660
	21st to end	Day	6% 5% 3 7% 5% 5% 5% 4 6% 7% 47%	2660
July	1st to 10th	Day	7% 6% 3 6% 4 4 4 3 5% 5% 54%	4430
	11th to 20th	Day	7% 6% 2 7% 7% 6% 7% 7% 9% 8% 35%	4430
	21st to end	Day	10% 7% 3 8% 6% 5% 5% 4 5% 6% 41%	4520
August	1st to 10th	Day	13% 9% 4 9% 6% 6% 6% 5% 7% 8% 28%	4092
	11th to 20th	Day	9% 8% 3 9% 7% 5% 6% 4 6% 6% 37%	3816
	21st to end	Day	8% 7% 4 9% 6% 6% 5% 4 6% 6% 37%	4180
September	1st to 10th	Day	10% 7% 2 6% 4 5% 3 3 4 5% 50%	2280
	11th to 20th	Day	9% 8% 3 6% 4 5% 4 3 4 5% 50%	2280
	21st to end	Day	6% 9% 3 6% 4 3 2 2 4 6% 55%	2049
October	1st to 10th	Day	4 6% 2 4 4 3 3 2 3 5% 64%	3170
	11th to 20th	Day	3 11% 2 8% 5% 5% 4 3 6% 8% 46%	3150
	21st to end	Day	2 9% 3 10% 2 2 3 2 4 5% 59%	3438
November	1st to 10th	Day	1 6% 3 9% 3 4 3 3 4 5% 59%	1773
	11th to 20th	Day	8% 3 7% 4 3 2 3 4 8% 58%	1800
	21st to end	Day	1 6% 3 9% 8% 3 2 2 4 6% 56%	1630
December	1st to 10th	Day	4 3 14% 9% 6% 5% 3 4 7% 45%	1600
	11th to 20th	Day	6% 4 12% 6% 5% 4 4 5% 9% 46%	2006
	21st to end	Day	5% 4 14% 9% 6% 5% 3 5% 7% 41%	2818
January	1st to 10th	Night	2 3 16% 12% 7% 5% 3 4 7% 42%	4417
	11th to 20th	Night	3 5% 17% 11% 6% 7% 3 3 5% 41%	4226
	21st to end	Night	4 5% 16% 9% 6% 5% 3 5% 5% 42%	4521
February	1st to 10th	Night	3 4 16% 9% 6% 4 3 5% 6% 43%	2470
	11th to 20th	Night	4 4 13% 9% 6% 5% 4 5% 6% 44%	2298
	21st to end	Night	4 4 13% 8% 8% 5% 4 5% 6% 43%	1884
March	1st to 10th	Night	4 7% 13% 7% 4 4 4 6% 7% 44%	3624
	11th to 20th	Night	7% 6% 15% 6% 4 3 3 5% 6% 45%	3490
	21st to end	Night	1 8% 6% 13% 7% 6% 5% 5% 5% 6% 37%	3678
April	1st to 10th	Night	1 5% 3 10% 6% 5% 5% 3 5% 7% 50%	1900
	11th to 20th	Night	1 10% 3 11% 7% 5% 5% 3 6% 5% 44%	1877
	21st to end	Night	2 10% 4 9% 5% 4 4 4 5% 7% 46%	1900
May	1st to 10th	Night	3 10% 5% 10% 4 4 4 4 6% 7% 43%	2999
	11th to 20th	Night	3 9% 3 8% 6% 5% 6% 5% 7% 8% 41%	2517
	21st to end	Night	2 8% 3 5% 4 4 4 4 6% 7% 55%	2762
June	1st to 10th	Night	2 3 2 4 4 3 4 4 6% 10% 59%	1520
	11th to 20th	Night	4 5% 1 4 3 3 4 3 4 7% 62%	1520
	21st to end	Night	3 3 2 4 3 4 3 4 6% 9% 59%	1520
July	1st to 10th	Night	4 5% 2 5% 3 3 4 4 5% 7% 58%	2540
	11th to 20th	Night	2 2 1 4 4 4 6% 6% 9% 12% 50%	2540
	21st to end	Night	4 3 1 5% 4 5% 5% 5% 7% 9% 52%	3039
August	1st to 10th	Night	5% 5% 2 6% 4 4 6% 6% 9% 11% 42%	2847
	11th to 20th	Night	4 4 1 4 4 4 4 5% 8% 10% 51%	3021
	21st to end	Night	4 4 2 6% 5% 6% 5% 5% 8% 9% 46%	3487
September	1st to 10th	Night	4 4 2 6% 3 3 5% 4 6% 8% 55%	1900
	11th to 20th	Night	4 4 2 6% 3 3 4 3 5% 6% 60%	1900
	21st to end	Night	3 5% 2 5% 3 3 3 3 4 7% 61%	2126
October	1st to 10th	Night	2 3 1 3 2 2 2 2 3 5% 73%	3800
	11th to 20th	Night	1 5% 2 5% 4 3 4 4 5% 7% 58%	3778
	21st to end	Night	1 6% 2 6% 3 3 3 2 3 5% 65%	4120
November	1st to 10th	Night	4 3 7% 3 3 3 3 4 6% 63%	2506
	11th to 20th	Night	4 3 9% 5% 4 3 3 4 6% 60%	2600
	21st to end	Night	5% 3 9% 7% 4 3 3 5% 7% 54%	2765
December	1st to 10th	Night	3 3 11% 8% 5% 4 3 4 6% 54%	2800
	11th to 20th	Night	5% 3 9% 7% 6% 4 4 6% 7% 47%	3411
	21st to end	Night	4 3 12% 9% 7% 4 4 5% 7% 45%	4922

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	36% 7% 14% 20% 18% 5%	2539
	11th to 20th	Day	46% 6% 15% 20% 10% 3	2773
	21st to end	Day	39% 5% 12% 24% 14% 6%	3146
February	1st to 10th	Day	45% 5% 15% 17% 13% 5%	1710
	11th to 20th	Day	39% 3 12% 22% 18% 7%	1776
	21st to end	Day	42% 3 10% 19% 18% 7%	1570
March	1st to 10th	Day	41% 4 7% 22% 19% 7%	3226
	11th to 20th	Day	43% 8% 10% 26% 10% 2	3490
	21st to end	Day	51% 4 10% 22% 11% 2	3969
April	1st to 10th	Day	40% 5% 12% 20% 17% 6%	2280
	11th to 20th	Day	50% 3 12% 17% 15% 3	2254
	21st to end	Day	50% 4 9% 25% 11% 1	2280
May	1st to 10th	Day	52% 5% 9% 17% 16% 2	3967
	11th to 20th	Day	38% 7% 10% 26% 17% 1	4392
	21st to end	Day	31% 7% 8% 23% 27% 5%	4825
June	1st to 10th	Day	33% 6% 12% 24% 18% 5%	2660
	11th to 20th	Day	33% 5% 8% 18% 23% 13%	2660
	21st to end	Day	33% 7% 7% 19% 24% 11%	2660
July	1st to 10th	Day	30% 6% 6% 11% 22% 25%	4361
	11th to 20th	Day	37% 10% 11% 18% 15% 8%	4355
	21st to end	Day	39% 7% 10% 13% 15% 16%	4377
August	1st to 10th	Day	48% 10% 13% 12% 13% 4	4078
	11th to 20th	Day	45% 7% 9% 13% 19% 7%	3854
	21st to end	Day	42% 8% 8% 15% 19% 7%	4179
September	1st to 10th	Day	37% 5% 6% 15% 26% 11%	2280
	11th to 20th	Day	35% 5% 9% 18% 25% 8%	2280
	21st to end	Day	31% 3 6% 26% 28% 5%	2049
October	1st to 10th	Day	22% 5% 6% 24% 35% 9%	3170
	11th to 20th	Day	33% 7% 9% 28% 19% 5%	3150
	21st to end	Day	27% 3 8% 30% 28% 4	3438
November	1st to 10th	Day	25% 5% 12% 23% 30% 5%	1773
	11th to 20th	Day	23% 3 16% 29% 22% 8%	1800
	21st to end	Day	30% 3 10% 28% 19% 10%	1630
December	1st to 10th	Day	36% 6% 15% 24% 16% 4	1600
	11th to 20th	Day	31% 7% 13% 28% 19% 2	2004
	21st to end	Day	35% 6% 12% 16% 22% 8%	2818
January	1st to 10th	Night	36% 5% 15% 25% 14% 5%	4417
	11th to 20th	Night	39% 6% 16% 23% 13% 4	4226
	21st to end	Night	35% 6% 14% 25% 15% 5%	4521
February	1st to 10th	Night	37% 4 16% 22% 16% 4	2470
	11th to 20th	Night	35% 4 14% 23% 19% 5%	2299
	21st to end	Night	34% 4 13% 22% 20% 7%	1884
March	1st to 10th	Night	34% 4 11% 24% 21% 7%	3624
	11th to 20th	Night	36% 4 13% 30% 13% 3	3490
	21st to end	Night	38% 7% 17% 26% 11% 1	3678
April	1st to 10th	Night	29% 5% 17% 24% 20% 4	1900
	11th to 20th	Night	36% 5% 14% 27% 16% 2	1877
	21st to end	Night	34% 5% 17% 29% 15% 1	1900
May	1st to 10th	Night	35% 7% 11% 26% 18% 3	2999
	11th to 20th	Night	35% 7% 13% 29% 15%	2518
	21st to end	Night	24% 5% 11% 30% 26% 3	2762
June	1st to 10th	Night	20% 6% 16% 30% 21% 6%	1520
	11th to 20th	Night	21% 5% 12% 22% 28% 13%	1520
	21st to end	Night	20% 6% 13% 23% 28% 11%	1520
July	1st to 10th	Night	25% 6% 10% 18% 21% 20%	2500
	11th to 20th	Night	21% 8% 18% 29% 15% 8%	2492
	21st to end	Night	22% 9% 20% 24% 11% 14%	2944
August	1st to 10th	Night	32% 10% 23% 18% 13% 4	2838
	11th to 20th	Night	26% 8% 22% 17% 18% 9%	3049
	21st to end	Night	31% 9% 15% 19% 22% 4	3487
September	1st to 10th	Night	24% 7% 12% 21% 26% 8%	1900
	11th to 20th	Night	23% 5% 13% 24% 25% 10%	1900
	21st to end	Night	22% 5% 10% 33% 25% 4	2126
October	1st to 10th	Night	14% 3 8% 31% 36% 8%	3800
	11th to 20th	Night	21% 6% 13% 37% 19% 5%	3778
	21st to end	Night	20% 3 9% 31% 31% 6%	4120
November	1st to 10th	Night	21% 5% 13% 27% 27% 7%	2506
	11th to 20th	Night	22% 4 14% 30% 24% 7%	2600
	21st to end	Night	28% 4 10% 28% 21% 9%	2765
December	1st to 10th	Night	28% 6% 19% 25% 17% 6%	2800
	11th to 20th	Night	30% 6% 14% 23% 23% 4	3412
	21st to end	Night	33% 6% 12% 19% 20% 10%	4922

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	21% 27% 24% 19% 8% 2	270
	11th to 20th	Day	23% 30% 27% 16% 4	270
	21st to end	Day	14% 33% 31% 16% 6%	297
February	1st to 10th	Day	24% 41% 23% 10% 1 1	270
	11th to 20th	Day	29% 34% 24% 11% 1 1	270
	21st to end	Day	33% 33% 25% 8%	225
March	1st to 10th	Day	24% 32% 24% 17% 3	327
	11th to 20th	Day	19% 32% 31% 14% 4	460
	21st to end	Day	19% 41% 29% 8% 2	506
April	1st to 10th	Day	22% 37% 29% 9% 2 1	460
	11th to 20th	Day	28% 33% 26% 10% 2	452
	21st to end	Day	19% 39% 30% 9% 3 1	460
May	1st to 10th	Day	21% 36% 24% 14% 4 1	490
	11th to 20th	Day	15% 20% 34% 20% 10% 1	675
	21st to end	Day	15% 21% 30% 22% 10% 2	734
June	1st to 10th	Day	9% 20% 28% 24% 17% 2	680
	11th to 20th	Day	11% 21% 33% 21% 11% 1	680
	21st to end	Day	7% 21% 30% 24% 16% 2	680
July	1st to 10th	Day	10% 10% 26% 29% 22% 3	671
	11th to 20th	Day	8% 9% 25% 30% 23% 6%	668
	21st to end	Day	14% 12% 27% 28% 16% 4	571
August	1st to 10th	Day	16% 14% 31% 25% 11% 3	487
	11th to 20th	Day	7% 14% 35% 26% 13% 4	477
	21st to end	Day	10% 14% 32% 28% 13% 3	539
September	1st to 10th	Day	14% 16% 29% 24% 11% 6%	490
	11th to 20th	Day	12% 17% 37% 22% 10% 2	490
	21st to end	Day	12% 19% 29% 21% 14% 4	330
October	1st to 10th	Day	15% 18% 26% 20% 17% 3	300
	11th to 20th	Day	15% 30% 27% 17% 8% 2	300
	21st to end	Day	22% 28% 26% 15% 7% 2	330
November	1st to 10th	Day	22% 33% 24% 13% 7% 1	300
	11th to 20th	Day	18% 31% 30% 13% 6% 2	300
	21st to end	Day	14% 29% 34% 19% 4	300
December	1st to 10th	Day	21% 31% 25% 14% 9% 1	300
	11th to 20th	Day	20% 35% 27% 13% 5%	300
	21st to end	Day	22% 34% 26% 11% 7%	306
January	1st to 10th	Night	13% 23% 30% 22% 10% 2	950
	11th to 20th	Night	15% 23% 30% 23% 7% 1	824
	21st to end	Night	7% 22% 38% 25% 6% 1	836
February	1st to 10th	Night	10% 30% 35% 20% 5%	760
	11th to 20th	Night	9% 31% 33% 23% 4	744
	21st to end	Night	12% 27% 39% 19% 2	628
March	1st to 10th	Night	10% 24% 33% 26% 6% 1	760
	11th to 20th	Night	5% 18% 38% 29% 9% 1	760
	21st to end	Night	7% 26% 40% 23% 4	750
April	1st to 10th	Night	9% 25% 37% 24% 5%	570
	11th to 20th	Night	9% 25% 32% 26% 8%	563
	21st to end	Night	11% 18% 35% 28% 7% 1	570
May	1st to 10th	Night	10% 12% 40% 27% 10% 1	570
	11th to 20th	Night	8% 9% 31% 36% 15% 1	561
	21st to end	Night	8% 13% 27% 34% 16% 1	617
June	1st to 10th	Night	5% 7% 25% 40% 22% 1	570
	11th to 20th	Night	6% 11% 29% 40% 14% 1	570
	21st to end	Night	3 4 24% 42% 27% 1	570
July	1st to 10th	Night	6% 2 15% 41% 33% 3	555
	11th to 20th	Night	3 2 10% 40% 41% 4	552
	21st to end	Night	6% 3 10% 37% 41% 3	624
August	1st to 10th	Night	8% 1 12% 41% 35% 3	567
	11th to 20th	Night	6% 2 15% 41% 32% 4	564
	21st to end	Night	6% 1 14% 41% 35% 2	627
September	1st to 10th	Night	5% 3 15% 45% 28% 4	570
	11th to 20th	Night	5% 4 21% 44% 24% 3	570
	21st to end	Night	4 10% 22% 37% 23% 4	638
October	1st to 10th	Night	5% 15% 28% 31% 17% 4	760
	11th to 20th	Night	7% 19% 28% 30% 13% 2	760
	21st to end	Night	9% 18% 32% 29% 11% 2	836
November	1st to 10th	Night	7% 22% 33% 28% 10% 1	946
	11th to 20th	Night	11% 25% 34% 24% 6% 2	1000
	21st to end	Night	8% 21% 34% 29% 8%	1000
December	1st to 10th	Night	9% 27% 34% 22% 7%	1000
	11th to 20th	Night	11% 27% 36% 20% 7% 1	1000
	21st to end	Night	14% 25% 35% 21% 5% 1	1063

Page generated at 2024-12-21 02:13:52. Version ac07

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