Aztalan State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aztalan State Park clear sky chart from 2005-11-06 to 2024-04-03.

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	14% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	78734
	Night	14% 10% 4 7% 5% 3 4 4 5% 6% 37%	81448
Transparency	Day	47% 6% 13% 22% 11% 1	78435
	Night	47% 6% 12% 22% 13% 1	81268
Seeing	Day	17% 10% 29% 25% 14% 5%	14972
	Night	18% 8% 31% 31% 11% 1	25044

By Month

Percentage Cloud Cover SE (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	11% 14% 9% 11% 7% 4 3 4 4 5% 28%	2527
	11th to 20th	Day	11% 13% 6% 13% 6% 3 4 10% 6% 7% 20%	2530
	21st to end	Day	17% 18% 10% 11% 5% 2 3 3 4 5% 21%	2858
February	1st to 10th	Day	13% 12% 6% 9% 6% 4 5% 5% 4 6% 31%	1710
	11th to 20th	Day	13% 11% 4 6% 5% 4 6% 4 5% 6% 36%	1810
	21st to end	Day	13% 13% 4 9% 7% 3 4 4 4 6% 31%	1570
March	1st to 10th	Day	14% 9% 4 8% 4 3 5% 5% 5% 6% 36%	1900
	11th to 20th	Day	13% 8% 4 6% 6% 4 4 3 4 7% 41%	1981
	21st to end	Day	19% 10% 4 7% 6% 4 5% 4 4 7% 29%	2498
April	1st to 10th	Day	18% 12% 5% 7% 5% 3 5% 4 5% 6% 30%	2184
	11th to 20th	Day	18% 9% 4 6% 5% 3 4 6% 5% 7% 33%	2134
	21st to end	Day	20% 8% 4 7% 6% 3 4 4 5% 7% 33%	2245
May	1st to 10th	Day	16% 8% 3 7% 6% 4 5% 5% 6% 9% 30%	2382
	11th to 20th	Day	19% 7% 3 6% 6% 3 4 5% 5% 8% 35%	2479
	21st to end	Day	14% 6% 3 6% 6% 3 5% 5% 6% 7% 38%	2725
June	1st to 10th	Day	10% 4 2 5% 6% 3 5% 5% 6% 8% 44%	2520
	11th to 20th	Day	13% 5% 3 5% 5% 3 5% 5% 6% 8% 43%	2520
	21st to end	Day	12% 5% 3 5% 5% 3 5% 5% 6% 10% 41%	2520
July	1st to 10th	Day	8% 5% 2 5% 5% 4 4 5% 6% 10% 48%	2520
	11th to 20th	Day	7% 5% 2 5% 5% 4 5% 6% 7% 10% 45%	2520
	21st to end	Day	7% 4 3 4 5% 3 5% 5% 7% 10% 47%	2743
August	1st to 10th	Day	7% 4 3 5% 5% 4 6% 5% 7% 9% 44%	2507
	11th to 20th	Day	10% 5% 3 6% 5% 3 5% 5% 6% 9% 43%	2154
	21st to end	Day	10% 5% 2 5% 5% 3 5% 5% 5% 8% 46%	2376
September	1st to 10th	Day	14% 5% 2 5% 5% 3 5% 5% 6% 8% 43%	2160
	11th to 20th	Day	13% 5% 2 4 4 3 5% 3 5% 7% 50%	2080
	21st to end	Day	13% 6% 3 6% 5% 3 4 5% 5% 8% 43%	1980
October	1st to 10th	Day	15% 6% 2 6% 4 3 4 4 5% 7% 44%	1872
	11th to 20th	Day	20% 9% 3 7% 6% 3 3 4 6% 8% 32%	1800
	21st to end	Day	18% 10% 3 7% 5% 2 4 4 4 6% 37%	1787
November	1st to 10th	Day	12% 8% 3 6% 4 3 5% 4 4 6% 46%	1672
	11th to 20th	Day	15% 10% 4 9% 7% 4 5% 4 5% 6% 32%	1710
	21st to end	Day	17% 11% 4 7% 5% 3 3 3 4 5% 37%	1539
December	1st to 10th	Day	14% 13% 4 9% 8% 4 4 4 4 6% 31%	1520
	11th to 20th	Day	14% 13% 5% 8% 6% 3 5% 5% 5% 6% 28%	1918
	21st to end	Day	19% 21% 9% 12% 6% 3 4 4 3 3 15%	2783
January	1st to 10th	Night	12% 14% 8% 9% 6% 3 4 4 4 4 32%	4428
	11th to 20th	Night	12% 15% 6% 13% 8% 3 5% 6% 5% 6% 20%	4440
	21st to end	Night	17% 18% 9% 10% 6% 3 4 3 4 5% 22%	4806
February	1st to 10th	Night	11% 14% 6% 8% 6% 3 5% 4 5% 5% 33%	2470
	11th to 20th	Night	11% 11% 4 7% 6% 3 4 4 4 5% 40%	2255
	21st to end	Night	18% 11% 4 6% 5% 3 4 4 5% 6% 36%	1884
March	1st to 10th	Night	17% 9% 4 5% 6% 3 4 4 5% 6% 37%	2280
	11th to 20th	Night	13% 7% 3 3 5% 3 5% 5% 6% 9% 41%	2214
	21st to end	Night	19% 10% 4 7% 5% 4 5% 4 4 5% 33%	2099
April	1st to 10th	Night	17% 10% 3 6% 6% 3 4 5% 5% 6% 35%	1820
	11th to 20th	Night	21% 9% 3 5% 4 3 4 4 4 6% 37%	1775
	21st to end	Night	19% 8% 3 5% 5% 3 4 4 5% 6% 38%	1713
May	1st to 10th	Night	16% 7% 3 7% 4 3 6% 5% 6% 7% 34%	1576
	11th to 20th	Night	17% 6% 3 6% 5% 3 6% 4 6% 6% 38%	1416
	21st to end	Night	12% 6% 3 6% 5% 3 4 4 6% 10% 41%	1551
June	1st to 10th	Night	10% 3 2 4 5% 3 5% 5% 7% 9% 48%	1440
	11th to 20th	Night	13% 4 1 5% 5% 2 4 5% 5% 8% 47%	1440
	21st to end	Night	10% 4 2 6% 4 2 3 4 5% 8% 50%	1440
July	1st to 10th	Night	7% 3 1 3 4 2 4 5% 7% 11% 53%	1440
	11th to 20th	Night	7% 3 2 5% 4 2 4 4 5% 9% 55%	1440
	21st to end	Night	6% 3 1 5% 4 3 5% 5% 7% 8% 52%	1575
August	1st to 10th	Night	5% 5% 2 4 5% 4 5% 6% 7% 10% 48%	1432
	11th to 20th	Night	9% 4 2 4 4 3 3 5% 5% 8% 53%	1744
	21st to end	Night	9% 5% 2 4 4 3 5% 5% 5% 8% 51%	1980
September	1st to 10th	Night	9% 4 2 5% 4 2 4 4 5% 7% 53%	1800
	11th to 20th	Night	12% 5% 1 4 4 3 4 4 5% 6% 52%	1860
	21st to end	Night	11% 6% 3 5% 5% 2 3 4 5% 7% 49%	1980
October	1st to 10th	Night	11% 6% 3 5% 5% 3 3 4 4 6% 49%	2086
	11th to 20th	Night	17% 8% 2 6% 5% 3 5% 4 4 5% 42%	2160
	21st to end	Night	20% 9% 3 6% 4 3 4 4 5% 7% 36%	2569
November	1st to 10th	Night	12% 7% 3 5% 5% 2 4 4 5% 6% 47%	2406
	11th to 20th	Night	14% 10% 4 7% 6% 3 5% 5% 4 6% 35%	2470
	21st to end	Night	17% 9% 4 7% 5% 3 4 4 5% 5% 38%	2636
December	1st to 10th	Night	16% 13% 4 8% 6% 4 5% 4 4 5% 31%	2660
	11th to 20th	Night	16% 14% 5% 9% 6% 3 5% 4 4 5% 29%	3279
	21st to end	Night	22% 17% 6% 9% 6% 3 4 4 4 5% 20%	4884

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	60% 5% 14% 15% 5%	2528
	11th to 20th	Day	60% 7% 12% 15% 5%	2530
	21st to end	Day	67% 4 10% 15% 5%	2858
February	1st to 10th	Day	54% 5% 12% 18% 10% 1	1710
	11th to 20th	Day	49% 5% 11% 24% 9% 2	1820
	21st to end	Day	55% 5% 10% 18% 10% 2	1570
March	1st to 10th	Day	48% 7% 13% 22% 9% 1	1900
	11th to 20th	Day	44% 5% 13% 24% 13% 1	1981
	21st to end	Day	55% 7% 11% 19% 7% 1	2498
April	1st to 10th	Day	54% 6% 11% 18% 10%	2184
	11th to 20th	Day	49% 7% 11% 20% 12% 2	2134
	21st to end	Day	50% 7% 12% 19% 11% 1	2245
May	1st to 10th	Day	49% 7% 13% 22% 8% 1	2382
	11th to 20th	Day	47% 7% 12% 22% 12% 1	2483
	21st to end	Day	44% 7% 12% 21% 13% 2	2725
June	1st to 10th	Day	36% 7% 14% 26% 16% 1	2520
	11th to 20th	Day	37% 7% 13% 23% 18% 1	2520
	21st to end	Day	38% 8% 15% 23% 15% 2	2520
July	1st to 10th	Day	31% 8% 15% 31% 14% 2	2451
	11th to 20th	Day	33% 9% 16% 24% 17% 2	2445
	21st to end	Day	30% 8% 17% 27% 16% 3	2591
August	1st to 10th	Day	35% 8% 15% 29% 12% 2	2492
	11th to 20th	Day	37% 8% 15% 26% 13% 1	2154
	21st to end	Day	35% 7% 12% 25% 18% 2	2376
September	1st to 10th	Day	37% 7% 12% 24% 17% 1	2160
	11th to 20th	Day	34% 5% 13% 31% 16% 2	2080
	21st to end	Day	40% 5% 12% 30% 13% 1	1980
October	1st to 10th	Day	41% 5% 9% 29% 15% 1	1872
	11th to 20th	Day	50% 6% 12% 22% 10% 1	1800
	21st to end	Day	49% 5% 11% 23% 12% 1	1787
November	1st to 10th	Day	40% 6% 14% 25% 14% 2	1672
	11th to 20th	Day	52% 6% 13% 20% 9% 1	1710
	21st to end	Day	51% 4 15% 23% 6%	1539
December	1st to 10th	Day	56% 5% 14% 17% 7% 1	1520
	11th to 20th	Day	55% 6% 14% 16% 6% 2	1915
	21st to end	Day	75% 5% 7% 8% 5%	2783
January	1st to 10th	Night	56% 6% 10% 20% 8%	4428
	11th to 20th	Night	63% 6% 10% 13% 8%	4440
	21st to end	Night	66% 5% 10% 14% 5%	4806
February	1st to 10th	Night	52% 6% 11% 19% 11% 2	2470
	11th to 20th	Night	47% 5% 11% 22% 14% 1	2256
	21st to end	Night	49% 5% 12% 20% 11% 3	1884
March	1st to 10th	Night	48% 6% 13% 21% 10% 2	2280
	11th to 20th	Night	39% 6% 14% 23% 16% 2	2214
	21st to end	Night	54% 5% 9% 20% 10% 2	2099
April	1st to 10th	Night	49% 6% 10% 19% 15% 1	1820
	11th to 20th	Night	49% 4 7% 20% 17% 3	1775
	21st to end	Night	45% 6% 12% 20% 14% 1	1713
May	1st to 10th	Night	47% 7% 12% 21% 12% 1	1576
	11th to 20th	Night	44% 7% 12% 23% 12% 2	1417
	21st to end	Night	38% 8% 14% 23% 14% 3	1552
June	1st to 10th	Night	31% 8% 14% 27% 19% 1	1440
	11th to 20th	Night	33% 7% 11% 24% 22% 2	1440
	21st to end	Night	33% 6% 15% 24% 19% 2	1440
July	1st to 10th	Night	25% 7% 17% 30% 18% 3	1400
	11th to 20th	Night	28% 6% 13% 30% 21% 3	1392
	21st to end	Night	26% 9% 14% 30% 16% 5%	1487
August	1st to 10th	Night	29% 10% 16% 27% 16% 3	1423
	11th to 20th	Night	30% 6% 15% 30% 18% 1	1744
	21st to end	Night	31% 6% 13% 27% 20% 3	1980
September	1st to 10th	Night	29% 7% 13% 26% 23% 2	1800
	11th to 20th	Night	32% 6% 11% 31% 18% 2	1860
	21st to end	Night	36% 5% 11% 30% 17% 1	1980
October	1st to 10th	Night	36% 6% 8% 30% 18% 1	2086
	11th to 20th	Night	44% 5% 12% 22% 17% 1	2160
	21st to end	Night	48% 5% 12% 23% 11% 1	2569
November	1st to 10th	Night	39% 5% 10% 27% 17% 2	2406
	11th to 20th	Night	50% 6% 13% 20% 11% 1	2470
	21st to end	Night	49% 5% 15% 22% 9% 1	2636
December	1st to 10th	Night	55% 6% 12% 19% 8% 1	2660
	11th to 20th	Night	58% 5% 11% 17% 8% 1	3281
	21st to end	Night	67% 5% 9% 14% 4	4884

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% 10% 34% 26% 7% 2	270
	11th to 20th	Day	18% 13% 39% 23% 6% 1	270
	21st to end	Day	23% 11% 34% 25% 5% 1	297
February	1st to 10th	Day	14% 17% 42% 19% 6% 1	270
	11th to 20th	Day	19% 22% 36% 17% 7%	270
	21st to end	Day	21% 17% 43% 16% 2	225
March	1st to 10th	Day	17% 19% 45% 15% 4	270
	11th to 20th	Day	20% 22% 31% 16% 10% 1	270
	21st to end	Day	27% 12% 30% 23% 6% 2	496
April	1st to 10th	Day	22% 15% 34% 24% 5%	428
	11th to 20th	Day	25% 15% 27% 21% 9% 3	412
	21st to end	Day	25% 11% 25% 24% 13% 2	420
May	1st to 10th	Day	21% 12% 30% 26% 9% 2	465
	11th to 20th	Day	22% 9% 29% 26% 11% 2	625
	21st to end	Day	17% 9% 28% 23% 16% 7%	679
June	1st to 10th	Day	10% 6% 28% 32% 19% 5%	630
	11th to 20th	Day	14% 7% 26% 32% 14% 6%	630
	21st to end	Day	13% 7% 29% 29% 17% 5%	630
July	1st to 10th	Day	8% 3 17% 31% 27% 14%	621
	11th to 20th	Day	8% 6% 26% 31% 22% 8%	618
	21st to end	Day	7% 3 26% 35% 21% 8%	684
August	1st to 10th	Day	8% 2 19% 33% 25% 12%	626
	11th to 20th	Day	12% 6% 14% 25% 26% 16%	465
	21st to end	Day	11% 5% 19% 31% 24% 10%	495
September	1st to 10th	Day	16% 6% 21% 26% 24% 8%	450
	11th to 20th	Day	13% 3 20% 29% 23% 11%	450
	21st to end	Day	15% 11% 27% 21% 18% 8%	450
October	1st to 10th	Day	20% 8% 22% 27% 17% 6%	342
	11th to 20th	Day	26% 14% 33% 20% 7% 1	270
	21st to end	Day	27% 12% 34% 21% 5% 2	297
November	1st to 10th	Day	14% 15% 39% 21% 11% 1	270
	11th to 20th	Day	19% 14% 41% 17% 9%	270
	21st to end	Day	25% 12% 38% 20% 6%	270
December	1st to 10th	Day	19% 15% 43% 17% 6% 1	270
	11th to 20th	Day	20% 13% 39% 18% 10% 1	270
	21st to end	Day	22% 18% 40% 17% 3	297
January	1st to 10th	Night	17% 14% 36% 25% 8% 1	950
	11th to 20th	Night	20% 12% 36% 26% 6% 1	950
	21st to end	Night	20% 10% 36% 28% 6%	1045
February	1st to 10th	Night	19% 9% 38% 26% 6% 1	950
	11th to 20th	Night	18% 14% 35% 29% 4	780
	21st to end	Night	23% 12% 38% 22% 4	628
March	1st to 10th	Night	21% 10% 34% 27% 7% 1	760
	11th to 20th	Night	17% 11% 34% 31% 7%	694
	21st to end	Night	22% 11% 29% 31% 7% 1	627
April	1st to 10th	Night	24% 10% 36% 25% 5%	546
	11th to 20th	Night	25% 10% 29% 29% 7%	533
	21st to end	Night	23% 7% 32% 29% 9%	540
May	1st to 10th	Night	19% 7% 36% 31% 6%	540
	11th to 20th	Night	19% 5% 34% 31% 12%	531
	21st to end	Night	14% 5% 28% 37% 17%	584
June	1st to 10th	Night	11% 4 26% 43% 15% 1	540
	11th to 20th	Night	14% 3 31% 39% 13% 1	540
	21st to end	Night	11% 3 26% 44% 16%	540
July	1st to 10th	Night	7% 2 15% 39% 33% 3	525
	11th to 20th	Night	7% 2 20% 46% 24% 2	522
	21st to end	Night	7% 2 17% 51% 21% 2	591
August	1st to 10th	Night	9% 1 15% 48% 25% 3	537
	11th to 20th	Night	9% 2 15% 40% 30% 5%	534
	21st to end	Night	11% 2 18% 41% 25% 3	594
September	1st to 10th	Night	9% 3 22% 37% 23% 5%	540
	11th to 20th	Night	13% 4 21% 34% 25% 4	600
	21st to end	Night	13% 6% 27% 30% 21% 2	720
October	1st to 10th	Night	14% 7% 29% 32% 17% 2	720
	11th to 20th	Night	22% 9% 32% 29% 8%	720
	21st to end	Night	24% 9% 31% 27% 7% 1	792
November	1st to 10th	Night	16% 9% 36% 27% 11% 1	740
	11th to 20th	Night	19% 12% 39% 23% 6%	760
	21st to end	Night	22% 12% 34% 25% 7%	926
December	1st to 10th	Night	22% 12% 39% 21% 6% 1	950
	11th to 20th	Night	24% 11% 34% 25% 5%	950
	21st to end	Night	29% 11% 34% 22% 4	1045

Page generated at 2024-03-31 05:08:56. Version ac07

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