Chaco Culture National Historical Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chaco Culture National Historical Park clear sky chart from 2005-11-06 to 2024-11-03.

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 4 4 4 4 4 6% 7% 59%	100821
	Night	3 5% 2 5% 4 4 4 4 5% 7% 57%	98412
Transparency	Day	22% 6% 9% 20% 25% 17%	100586
	Night	24% 6% 9% 20% 25% 16%	98236
Seeing	Day	5% 8% 21% 28% 25% 13%	14892
	Night	5% 5% 24% 40% 23% 3	25153

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 7% 3 5% 3 4 3 4 5% 6% 58%	2858
	11th to 20th	Day	2 4 2 4 3 4 4 3 6% 7% 60%	2860
	21st to end	Day	5% 8% 4 7% 4 4 4 4 5% 5% 50%	3146
February	1st to 10th	Day	2 6% 3 6% 4 3 3 3 4 7% 59%	1710
	11th to 20th	Day	4 7% 3 6% 4 4 4 3 5% 7% 53%	1736
	21st to end	Day	3 8% 3 4 3 4 4 3 5% 7% 54%	1617
March	1st to 10th	Day	3 5% 2 4 3 3 3 3 5% 7% 63%	3444
	11th to 20th	Day	3 7% 3 7% 5% 5% 5% 5% 6% 8% 47%	3490
	21st to end	Day	3 7% 2 5% 5% 4 5% 3 5% 5% 56%	3825
April	1st to 10th	Day	2 5% 2 4 4 4 4 3 5% 6% 62%	2261
	11th to 20th	Day	2 5% 2 4 3 4 4 4 6% 6% 61%	2251
	21st to end	Day	4 4 1 5% 3 3 4 3 5% 6% 62%	2280
May	1st to 10th	Day	3 3 1 4 3 3 3 2 5% 5% 67%	3915
	11th to 20th	Day	3 4 1 4 4 4 4 4 6% 7% 59%	4071
	21st to end	Day	2 2 1 3 2 3 3 3 3 5% 73%	4527
June	1st to 10th	Day	2 2 1 3 3 4 3 4 5% 7% 67%	2660
	11th to 20th	Day	2 2 2 2 2 2 2 4 5% 75%	2660
	21st to end	Day	2 2 1 3 4 4 4 4 6% 6% 63%	2579
July	1st to 10th	Day	3 2 1 4 4 4 3 4 5% 7% 65%	4110
	11th to 20th	Day	2 3 1 3 4 4 6% 5% 8% 12% 51%	4110
	21st to end	Day	2 3 1 5% 4 5% 6% 5% 8% 11% 50%	4454
August	1st to 10th	Day	3 4 2 7% 5% 5% 7% 5% 9% 12% 40%	4092
	11th to 20th	Day	2 2 1 4 5% 5% 5% 5% 8% 11% 52%	3843
	21st to end	Day	3 3 1 5% 6% 6% 6% 6% 8% 9% 46%	4180
September	1st to 10th	Day	5% 3 1 5% 4 4 4 3 6% 8% 56%	2280
	11th to 20th	Day	4 3 1 4 3 4 4 3 6% 5% 62%	2246
	21st to end	Day	5% 2 1 3 2 3 3 3 4 5% 70%	2015
October	1st to 10th	Day	5% 4 1 4 3 3 3 3 5% 6% 63%	1900
	11th to 20th	Day	4 3 1 3 3 2 2 2 3 4 74%	1900
	21st to end	Day	3 2 1 3 2 2 3 2 3 5% 73%	2090
November	1st to 10th	Day	2 3 1 3 2 2 2 2 3 5% 75%	1879
	11th to 20th	Day	2 3 1 3 2 3 3 2 4 5% 70%	1814
	21st to end	Day	5% 6% 3 5% 3 2 3 2 5% 5% 62%	1577
December	1st to 10th	Day	4 7% 2 4 3 4 3 3 4 6% 60%	1520
	11th to 20th	Day	5% 7% 3 6% 4 5% 5% 4 6% 8% 49%	1926
	21st to end	Day	3 7% 2 6% 4 3 4 3 5% 6% 57%	2995
January	1st to 10th	Night	2 10% 4 6% 4 3 4 3 5% 5% 53%	4097
	11th to 20th	Night	3 6% 2 4 3 3 3 3 4 6% 63%	4110
	21st to end	Night	4 10% 2 6% 4 4 4 3 5% 6% 51%	4521
February	1st to 10th	Night	2 6% 2 5% 3 3 2 3 4 5% 63%	2470
	11th to 20th	Night	6% 8% 3 5% 4 3 3 3 4 5% 58%	2330
	21st to end	Night	4 6% 3 4 3 3 3 2 5% 6% 60%	1835
March	1st to 10th	Night	1 4 1 4 2 3 4 3 4 6% 68%	3430
	11th to 20th	Night	6% 8% 3 7% 5% 4 5% 3 6% 7% 47%	3490
	21st to end	Night	3 5% 2 5% 3 3 4 3 5% 7% 60%	3828
April	1st to 10th	Night	3 4 1 4 4 3 4 4 4 6% 61%	1917
	11th to 20th	Night	4 4 1 5% 4 3 4 3 5% 6% 61%	1877
	21st to end	Night	4 4 1 5% 4 3 3 3 5% 5% 63%	1900
May	1st to 10th	Night	3 3 1 3 2 3 3 2 4 6% 69%	3050
	11th to 20th	Night	5% 5% 2 6% 5% 3 4 4 6% 6% 55%	2834
	21st to end	Night	2 1 1 3 2 2 2 2 3 5% 76%	3056
June	1st to 10th	Night	3 2 2 3 3 3 3 3 5% 6% 67%	1520
	11th to 20th	Night	3 2 1 3 2 2 3 3 4 5% 73%	1520
	21st to end	Night	3 3 2 5% 4 5% 4 4 7% 8% 54%	1592
July	1st to 10th	Night	3 3 1 5% 4 4 4 4 5% 6% 60%	2860
	11th to 20th	Night	3 4 2 7% 5% 7% 9% 7% 10% 11% 35%	2860
	21st to end	Night	3 4 2 7% 6% 6% 7% 6% 11% 11% 37%	3109
August	1st to 10th	Night	4 5% 4 11% 8% 8% 9% 7% 8% 9% 27%	2847
	11th to 20th	Night	3 4 2 6% 5% 6% 8% 6% 10% 11% 39%	2993
	21st to end	Night	3 4 2 7% 6% 7% 8% 6% 10% 11% 35%	3487
September	1st to 10th	Night	7% 4 2 6% 5% 4 5% 5% 7% 8% 47%	1900
	11th to 20th	Night	3 4 2 5% 3 3 4 4 5% 7% 60%	1929
	21st to end	Night	4 3 1 4 2 3 3 2 4 6% 68%	2163
October	1st to 10th	Night	4 3 1 4 3 3 3 4 5% 6% 64%	2280
	11th to 20th	Night	3 2 1 3 2 2 2 2 3 5% 73%	2280
	21st to end	Night	3 3 1 3 2 3 3 2 3 4 73%	2508
November	1st to 10th	Night	3 3 1 3 3 2 3 2 4 5% 71%	2244
	11th to 20th	Night	3 2 1 2 2 2 3 3 3 5% 74%	2343
	21st to end	Night	4 6% 1 3 3 3 3 3 4 5% 64%	2602
December	1st to 10th	Night	5% 6% 2 4 3 3 3 2 4 6% 63%	2660
	11th to 20th	Night	4 5% 2 5% 4 5% 5% 4 5% 7% 54%	3271
	21st to end	Night	4 7% 3 6% 4 4 4 3 4 5% 57%	4699

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	26% 5% 10% 33% 23% 3	2859
	11th to 20th	Day	22% 6% 15% 37% 17% 3	2860
	21st to end	Day	33% 7% 9% 26% 21% 4	3146
February	1st to 10th	Day	25% 5% 10% 25% 25% 10%	1710
	11th to 20th	Day	30% 4 8% 22% 27% 9%	1745
	21st to end	Day	27% 4 7% 18% 29% 14%	1617
March	1st to 10th	Day	20% 4 6% 22% 36% 13%	3444
	11th to 20th	Day	28% 10% 10% 24% 21% 7%	3490
	21st to end	Day	25% 6% 8% 23% 30% 8%	3825
April	1st to 10th	Day	23% 3 6% 19% 32% 17%	2261
	11th to 20th	Day	21% 4 6% 18% 32% 19%	2254
	21st to end	Day	21% 4 7% 19% 31% 17%	2280
May	1st to 10th	Day	16% 5% 6% 12% 35% 26%	3915
	11th to 20th	Day	19% 8% 9% 15% 29% 19%	4074
	21st to end	Day	13% 4 6% 9% 28% 40%	4527
June	1st to 10th	Day	15% 5% 6% 14% 29% 32%	2660
	11th to 20th	Day	12% 3 4 11% 21% 49%	2660
	21st to end	Day	19% 4 7% 15% 23% 31%	2579
July	1st to 10th	Day	19% 5% 7% 10% 13% 45%	4046
	11th to 20th	Day	20% 8% 12% 29% 22% 8%	4041
	21st to end	Day	22% 10% 15% 27% 19% 7%	4314
August	1st to 10th	Day	32% 10% 21% 20% 11% 7%	4078
	11th to 20th	Day	23% 8% 14% 22% 16% 16%	3882
	21st to end	Day	29% 8% 15% 20% 19% 9%	4179
September	1st to 10th	Day	25% 7% 10% 16% 22% 20%	2280
	11th to 20th	Day	22% 6% 9% 15% 24% 24%	2246
	21st to end	Day	18% 4 7% 17% 28% 27%	2015
October	1st to 10th	Day	22% 5% 9% 17% 23% 24%	1900
	11th to 20th	Day	16% 3 3 13% 37% 27%	1900
	21st to end	Day	15% 3 7% 20% 38% 17%	2090
November	1st to 10th	Day	14% 3 5% 22% 39% 17%	1879
	11th to 20th	Day	17% 3 6% 23% 40% 10%	1814
	21st to end	Day	25% 3 6% 21% 30% 14%	1577
December	1st to 10th	Day	26% 4 10% 29% 23% 9%	1520
	11th to 20th	Day	31% 7% 10% 23% 25% 3	1924
	21st to end	Day	27% 5% 9% 20% 24% 14%	2995
January	1st to 10th	Night	31% 5% 8% 29% 22% 4	4097
	11th to 20th	Night	22% 5% 13% 35% 21% 4	4110
	21st to end	Night	31% 6% 8% 27% 24% 4	4521
February	1st to 10th	Night	23% 3 11% 24% 27% 11%	2470
	11th to 20th	Night	29% 4 6% 23% 26% 11%	2331
	21st to end	Night	24% 5% 6% 17% 35% 14%	1835
March	1st to 10th	Night	14% 5% 7% 26% 37% 12%	3430
	11th to 20th	Night	30% 10% 10% 20% 22% 8%	3490
	21st to end	Night	20% 6% 9% 28% 31% 8%	3828
April	1st to 10th	Night	22% 4 6% 22% 30% 17%	1917
	11th to 20th	Night	23% 4 5% 16% 31% 21%	1877
	21st to end	Night	21% 4 6% 18% 33% 17%	1900
May	1st to 10th	Night	13% 5% 6% 14% 35% 27%	3050
	11th to 20th	Night	24% 9% 9% 18% 24% 17%	2835
	21st to end	Night	11% 4 6% 9% 29% 42%	3056
June	1st to 10th	Night	16% 5% 6% 14% 24% 35%	1520
	11th to 20th	Night	14% 3 5% 8% 21% 49%	1520
	21st to end	Night	24% 6% 10% 13% 18% 29%	1592
July	1st to 10th	Night	23% 6% 10% 9% 9% 43%	2815
	11th to 20th	Night	31% 11% 14% 25% 11% 8%	2806
	21st to end	Night	32% 11% 17% 25% 12% 3	3011
August	1st to 10th	Night	47% 11% 14% 12% 8% 8%	2838
	11th to 20th	Night	32% 11% 18% 12% 11% 17%	3020
	21st to end	Night	35% 10% 15% 18% 14% 8%	3487
September	1st to 10th	Night	30% 8% 10% 15% 17% 20%	1900
	11th to 20th	Night	22% 6% 9% 16% 19% 28%	1929
	21st to end	Night	18% 4 6% 13% 29% 30%	2163
October	1st to 10th	Night	20% 6% 9% 16% 23% 27%	2280
	11th to 20th	Night	15% 3 5% 13% 32% 32%	2280
	21st to end	Night	15% 3 4 22% 37% 19%	2508
November	1st to 10th	Night	15% 3 5% 20% 39% 17%	2244
	11th to 20th	Night	13% 3 7% 21% 40% 15%	2343
	21st to end	Night	22% 4 6% 19% 34% 14%	2602
December	1st to 10th	Night	23% 3 9% 29% 27% 8%	2660
	11th to 20th	Night	28% 5% 11% 24% 26% 6%	3272
	21st to end	Night	27% 6% 8% 21% 27% 12%	4699

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	7% 4 34% 31% 21% 3	270
	11th to 20th	Day	6% 14% 27% 31% 18% 4	270
	21st to end	Day	4 7% 23% 36% 20% 10%	297
February	1st to 10th	Day	3 11% 30% 35% 16% 6%	270
	11th to 20th	Day	6% 7% 34% 38% 14% 1	270
	21st to end	Day	12% 16% 32% 23% 15% 1	272
March	1st to 10th	Day	6% 18% 30% 26% 18% 2	460
	11th to 20th	Day	8% 16% 28% 26% 17% 5%	460
	21st to end	Day	10% 22% 32% 23% 11% 2	506
April	1st to 10th	Day	8% 14% 32% 25% 16% 5%	460
	11th to 20th	Day	9% 17% 35% 22% 15% 2	452
	21st to end	Day	7% 14% 35% 26% 14% 4	460
May	1st to 10th	Day	7% 11% 34% 27% 17% 3	463
	11th to 20th	Day	8% 7% 31% 25% 19% 10%	488
	21st to end	Day	5% 10% 27% 31% 20% 8%	553
June	1st to 10th	Day	2 5% 16% 36% 30% 10%	680
	11th to 20th	Day	2 3 20% 38% 26% 11%	680
	21st to end	Day	3 2 17% 36% 32% 11%	599
July	1st to 10th	Day	5% 1 10% 26% 36% 21%	486
	11th to 20th	Day	4 4 17% 36% 39%	484
	21st to end	Day	4 1 4 18% 35% 38%	531
August	1st to 10th	Day	5% 7% 22% 38% 27%	487
	11th to 20th	Day	4 1 9% 25% 35% 26%	477
	21st to end	Day	3 1 6% 20% 44% 26%	539
September	1st to 10th	Day	7% 2 9% 24% 34% 25%	490
	11th to 20th	Day	2 3 15% 32% 31% 17%	490
	21st to end	Day	6% 3 19% 27% 30% 16%	415
October	1st to 10th	Day	3 9% 18% 24% 26% 20%	300
	11th to 20th	Day	5% 8% 20% 26% 25% 15%	300
	21st to end	Day	5% 8% 15% 30% 29% 13%	330
November	1st to 10th	Day	5% 5% 21% 34% 29% 6%	276
	11th to 20th	Day	4 6% 17% 34% 29% 11%	270
	21st to end	Day	6% 11% 25% 30% 17% 11%	270
December	1st to 10th	Day	7% 7% 26% 32% 20% 9%	270
	11th to 20th	Day	5% 12% 26% 31% 21% 4	270
	21st to end	Day	10% 13% 26% 33% 14% 5%	297
January	1st to 10th	Night	7% 5% 25% 39% 22% 2	760
	11th to 20th	Night	7% 6% 25% 39% 20% 3	760
	21st to end	Night	7% 7% 23% 40% 19% 4	836
February	1st to 10th	Night	5% 6% 33% 38% 17% 2	760
	11th to 20th	Night	8% 8% 29% 40% 13% 1	744
	21st to end	Night	7% 10% 35% 38% 10%	628
March	1st to 10th	Night	4 8% 33% 37% 16% 1	760
	11th to 20th	Night	6% 8% 28% 41% 17% 1	760
	21st to end	Night	6% 9% 33% 37% 15% 1	836
April	1st to 10th	Night	5% 10% 38% 37% 10%	587
	11th to 20th	Night	6% 12% 34% 38% 10%	563
	21st to end	Night	5% 9% 38% 36% 11% 1	570
May	1st to 10th	Night	5% 7% 31% 45% 13%	570
	11th to 20th	Night	7% 4 28% 42% 17% 2	561
	21st to end	Night	4 6% 31% 41% 18% 1	617
June	1st to 10th	Night	3 4 24% 50% 18% 1	570
	11th to 20th	Night	3 3 26% 48% 19% 1	570
	21st to end	Night	2 1 22% 45% 28% 2	570
July	1st to 10th	Night	3 1 15% 45% 35% 1	555
	11th to 20th	Night	6% 1 8% 34% 47% 4	552
	21st to end	Night	6% 2 7% 30% 49% 6%	624
August	1st to 10th	Night	5% 1 8% 30% 48% 8%	567
	11th to 20th	Night	5% 1 10% 39% 38% 7%	564
	21st to end	Night	4 8% 41% 43% 4	627
September	1st to 10th	Night	6% 2 11% 42% 35% 3	570
	11th to 20th	Night	4 1 16% 46% 29% 4	599
	21st to end	Night	4 1 18% 40% 33% 4	760
October	1st to 10th	Night	4 3 24% 42% 25% 2	760
	11th to 20th	Night	3 3 21% 44% 26% 4	760
	21st to end	Night	4 4 22% 40% 24% 5%	836
November	1st to 10th	Night	4 2 21% 43% 26% 4	748
	11th to 20th	Night	3 3 22% 40% 26% 4	823
	21st to end	Night	7% 9% 21% 36% 23% 4	950
December	1st to 10th	Night	6% 6% 23% 43% 19% 2	950
	11th to 20th	Night	8% 7% 29% 36% 20% 1	950
	21st to end	Night	8% 8% 29% 38% 15% 1	936

Page generated at 2024-10-31 01:39:21. Version ac07

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