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 2024-11-04.

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	13% 9% 3 8% 5% 4 4 4 5% 7% 38%	101421
	Night	14% 10% 4 7% 4 4 4 3 5% 6% 38%	97683
Transparency	Day	43% 6% 12% 24% 13% 1	104948
	Night	45% 6% 11% 23% 14% 2	102284
Seeing	Day	16% 10% 29% 25% 14% 5%	15897
	Night	18% 8% 31% 31% 12% 1	25740

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% 16% 8% 12% 6% 5% 4 3 4 5% 27%	2527
	11th to 20th	Day	11% 13% 5% 15% 5% 4 6% 8% 6% 7% 20%	2530
	21st to end	Day	17% 19% 10% 12% 4 3 3 2 4 5% 21%	2858
February	1st to 10th	Day	12% 14% 6% 10% 4 5% 4 4 4 6% 31%	1710
	11th to 20th	Day	13% 12% 3 7% 5% 5% 5% 3 5% 6% 36%	1810
	21st to end	Day	12% 14% 4 10% 7% 4 5% 3 4 5% 31%	1570
March	1st to 10th	Day	13% 8% 2 7% 4 4 4 3 5% 6% 44%	3120
	11th to 20th	Day	12% 6% 3 8% 5% 5% 4 4 4 6% 44%	3306
	21st to end	Day	21% 12% 4 10% 5% 4 4 3 4 6% 28%	4155
April	1st to 10th	Day	18% 13% 4 7% 5% 4 4 3 5% 6% 31%	2280
	11th to 20th	Day	17% 9% 4 7% 4 4 5% 4 6% 6% 34%	2254
	21st to end	Day	20% 8% 3 7% 5% 5% 4 3 5% 7% 34%	2370
May	1st to 10th	Day	15% 7% 2 7% 5% 5% 5% 3 6% 7% 37%	4166
	11th to 20th	Day	14% 6% 3 6% 4 4 4 3 5% 7% 44%	4399
	21st to end	Day	13% 7% 2 6% 5% 4 5% 4 6% 8% 39%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 4 7% 8% 44%	2660
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 7% 8% 42%	2660
	21st to end	Day	12% 6% 3 6% 4 4 5% 4 7% 9% 40%	2660
July	1st to 10th	Day	12% 7% 3 8% 5% 5% 5% 4 7% 9% 35%	4440
	11th to 20th	Day	4 4 2 5% 4 5% 5% 4 6% 10% 51%	4440
	21st to end	Day	8% 6% 3 6% 5% 5% 4 4 7% 9% 43%	4813
August	1st to 10th	Day	9% 5% 3 7% 5% 5% 6% 4 7% 8% 41%	4423
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 47%	3771
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 8% 44%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 3 4 5% 2 5% 7% 50%	2195
	21st to end	Day	13% 6% 2 6% 4 4 4 4 5% 8% 43%	2090
October	1st to 10th	Day	14% 5% 2 7% 4 4 4 3 5% 7% 46%	1975
	11th to 20th	Day	19% 9% 3 8% 4 4 4 3 5% 8% 34%	1900
	21st to end	Day	17% 10% 3 7% 5% 3 4 3 4 6% 38%	1886
November	1st to 10th	Day	12% 9% 3 6% 3 4 5% 3 4 6% 46%	1699
	11th to 20th	Day	14% 11% 3 9% 6% 5% 5% 3 5% 6% 32%	1710
	21st to end	Day	17% 12% 4 8% 5% 4 3 2 5% 5% 36%	1539
December	1st to 10th	Day	14% 13% 4 10% 7% 5% 4 3 4 6% 31%	1520
	11th to 20th	Day	13% 14% 5% 9% 5% 5% 4 5% 6% 6% 28%	1918
	21st to end	Day	19% 22% 8% 14% 5% 4 4 3 3 3 15%	2783
January	1st to 10th	Night	12% 15% 8% 10% 5% 4 3 3 4 4 32%	4428
	11th to 20th	Night	12% 15% 6% 15% 6% 4 5% 5% 5% 6% 20%	4440
	21st to end	Night	16% 19% 8% 11% 5% 5% 3 2 4 5% 22%	4806
February	1st to 10th	Night	11% 15% 5% 9% 6% 4 4 3 5% 5% 33%	2470
	11th to 20th	Night	11% 12% 3 8% 5% 4 4 3 4 5% 40%	2255
	21st to end	Night	17% 11% 4 7% 4 4 4 3 5% 5% 36%	1884
March	1st to 10th	Night	17% 9% 3 5% 5% 4 4 3 4 4 43%	3733
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 46%	3682
	21st to end	Night	21% 12% 5% 10% 4 4 4 3 3 4 30%	3475
April	1st to 10th	Night	17% 11% 2 7% 4 4 4 3 5% 6% 36%	1900
	11th to 20th	Night	20% 9% 3 6% 4 4 4 3 5% 5% 38%	1875
	21st to end	Night	18% 8% 3 6% 4 4 4 3 5% 6% 38%	1808
May	1st to 10th	Night	16% 8% 3 7% 4 4 5% 3 6% 7% 37%	2730
	11th to 20th	Night	14% 6% 2 7% 4 4 6% 4 6% 6% 42%	2506
	21st to end	Night	13% 8% 3 7% 4 4 4 3 6% 6% 42%	2743
June	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 7% 8% 47%	1520
	11th to 20th	Night	12% 4 1 5% 4 3 4 4 6% 9% 47%	1520
	21st to end	Night	10% 5% 2 7% 4 3 4 3 5% 8% 49%	1520
July	1st to 10th	Night	14% 8% 2 5% 4 4 5% 4 6% 8% 41%	2530
	11th to 20th	Night	5% 3 2 5% 4 4 5% 3 7% 9% 55%	2530
	21st to end	Night	7% 4 2 6% 5% 5% 5% 5% 6% 8% 48%	2750
August	1st to 10th	Night	10% 5% 2 4 4 4 4 4 7% 8% 48%	2517
	11th to 20th	Night	9% 6% 2 6% 4 3 4 4 5% 8% 49%	3056
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 6% 9% 48%	3476
September	1st to 10th	Night	8% 5% 2 5% 3 3 4 3 6% 7% 55%	1900
	11th to 20th	Night	11% 5% 1 5% 3 4 4 3 5% 7% 51%	1964
	21st to end	Night	10% 6% 3 6% 4 3 4 4 5% 7% 49%	2090
October	1st to 10th	Night	10% 6% 3 6% 4 3 3 3 4 6% 50%	2202
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 4 5% 43%	2280
	21st to end	Night	19% 9% 3 6% 4 4 4 3 5% 7% 36%	2712
November	1st to 10th	Night	12% 8% 3 6% 4 3 4 4 5% 6% 46%	2452
	11th to 20th	Night	13% 11% 4 8% 6% 4 5% 4 4 6% 35%	2470
	21st to end	Night	17% 10% 3 7% 5% 4 4 3 5% 5% 38%	2636
December	1st to 10th	Night	15% 13% 4 9% 5% 5% 5% 3 4 5% 31%	2660
	11th to 20th	Night	16% 14% 5% 10% 5% 4 4 3 4 5% 29%	3279
	21st to end	Night	22% 18% 6% 10% 5% 4 4 3 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	40% 7% 11% 28% 13% 2	3120
	11th to 20th	Day	40% 5% 12% 29% 13% 1	3306
	21st to end	Day	58% 6% 11% 17% 7% 2	4155
April	1st to 10th	Day	54% 6% 11% 19% 10%	2280
	11th to 20th	Day	48% 7% 10% 20% 12% 2	2254
	21st to end	Day	50% 6% 12% 19% 11% 1	2370
May	1st to 10th	Day	43% 7% 11% 23% 15% 1	4204
	11th to 20th	Day	38% 7% 10% 31% 14%	4403
	21st to end	Day	40% 8% 11% 22% 16% 3	4837
June	1st to 10th	Day	36% 7% 13% 25% 17% 1	2660
	11th to 20th	Day	37% 7% 13% 23% 18% 1	2660
	21st to end	Day	39% 7% 15% 23% 15% 2	2660
July	1st to 10th	Day	43% 7% 13% 26% 9% 2	4371
	11th to 20th	Day	27% 7% 17% 31% 17% 1	4365
	21st to end	Day	35% 8% 16% 20% 19% 2	4662
August	1st to 10th	Day	38% 7% 13% 29% 11% 1	4408
	11th to 20th	Day	33% 7% 13% 34% 13% 1	3807
	21st to end	Day	36% 6% 13% 27% 17% 1	4179
September	1st to 10th	Day	36% 7% 12% 25% 18% 1	2280
	11th to 20th	Day	33% 5% 12% 31% 18% 2	2195
	21st to end	Day	40% 5% 11% 30% 14% 1	2090
October	1st to 10th	Day	24% 3 6% 40% 25% 2	3274
	11th to 20th	Day	36% 4 10% 28% 21% 1	3140
	21st to end	Day	42% 4 10% 29% 12% 2	3086
November	1st to 10th	Day	40% 6% 14% 25% 14% 2	1699
	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	45% 5% 12% 24% 9% 4	3733
	11th to 20th	Night	34% 6% 12% 28% 17% 3	3682
	21st to end	Night	58% 5% 8% 17% 10% 1	3475
April	1st to 10th	Night	48% 6% 10% 20% 15% 1	1900
	11th to 20th	Night	48% 4 7% 20% 18% 3	1875
	21st to end	Night	45% 6% 12% 22% 14% 1	1808
May	1st to 10th	Night	44% 7% 13% 18% 17% 2	2757
	11th to 20th	Night	39% 8% 11% 27% 13% 1	2507
	21st to end	Night	39% 8% 11% 18% 17% 6%	2751
June	1st to 10th	Night	31% 8% 14% 27% 19% 1	1520
	11th to 20th	Night	33% 7% 11% 25% 22% 3	1520
	21st to end	Night	35% 6% 15% 23% 19% 2	1520
July	1st to 10th	Night	41% 6% 15% 22% 13% 4	2490
	11th to 20th	Night	25% 6% 15% 34% 18% 2	2482
	21st to end	Night	31% 9% 14% 22% 21% 3	2662
August	1st to 10th	Night	32% 7% 15% 25% 19% 1	2508
	11th to 20th	Night	33% 6% 12% 33% 16% 1	3086
	21st to end	Night	32% 6% 13% 27% 19% 3	3476
September	1st to 10th	Night	28% 6% 13% 27% 23% 2	1900
	11th to 20th	Night	31% 6% 11% 31% 19% 2	1964
	21st to end	Night	35% 5% 11% 30% 18% 1	2090
October	1st to 10th	Night	25% 4 6% 37% 26% 1	3670
	11th to 20th	Night	34% 4 12% 27% 21% 2	3779
	21st to end	Night	43% 4 9% 27% 15% 1	4462
November	1st to 10th	Night	40% 5% 10% 27% 17% 2	2452
	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% 14% 35% 23% 5%	460
	11th to 20th	Day	25% 15% 27% 21% 9% 3	452
	21st to end	Day	25% 12% 25% 23% 13% 2	460
May	1st to 10th	Day	20% 12% 30% 26% 10% 2	508
	11th to 20th	Day	21% 9% 30% 26% 12% 2	675
	21st to end	Day	17% 9% 28% 23% 16% 7%	734
June	1st to 10th	Day	10% 7% 29% 32% 18% 5%	680
	11th to 20th	Day	14% 8% 28% 32% 14% 6%	680
	21st to end	Day	14% 8% 29% 28% 17% 4	680
July	1st to 10th	Day	8% 3 18% 31% 26% 13%	671
	11th to 20th	Day	7% 6% 26% 29% 22% 9%	668
	21st to end	Day	7% 3 25% 35% 22% 9%	739
August	1st to 10th	Day	8% 3 20% 33% 24% 11%	676
	11th to 20th	Day	12% 6% 16% 25% 25% 15%	506
	21st to end	Day	12% 5% 18% 31% 25% 10%	539
September	1st to 10th	Day	14% 6% 22% 26% 23% 8%	490
	11th to 20th	Day	12% 2 21% 29% 24% 12%	490
	21st to end	Day	15% 11% 27% 23% 17% 8%	490
October	1st to 10th	Day	19% 8% 23% 29% 16% 5%	375
	11th to 20th	Day	23% 14% 32% 22% 8% 1	300
	21st to end	Day	26% 13% 34% 21% 5% 2	330
November	1st to 10th	Day	14% 14% 38% 22% 11% 1	279
	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	23% 11% 36% 25% 5%	570
	11th to 20th	Night	24% 11% 30% 28% 7%	563
	21st to end	Night	22% 8% 32% 29% 8%	570
May	1st to 10th	Night	19% 8% 35% 32% 6%	570
	11th to 20th	Night	19% 4 34% 32% 12%	561
	21st to end	Night	14% 5% 27% 37% 17%	617
June	1st to 10th	Night	11% 4 27% 42% 14% 1	570
	11th to 20th	Night	14% 2 32% 39% 12% 1	570
	21st to end	Night	12% 3 27% 43% 15%	570
July	1st to 10th	Night	9% 2 16% 39% 32% 3	555
	11th to 20th	Night	7% 2 19% 45% 23% 3	552
	21st to end	Night	7% 2 17% 51% 22% 2	624
August	1st to 10th	Night	9% 1 15% 48% 25% 3	567
	11th to 20th	Night	10% 2 15% 41% 29% 4	564
	21st to end	Night	11% 2 18% 40% 25% 3	627
September	1st to 10th	Night	8% 3 22% 37% 24% 5%	570
	11th to 20th	Night	12% 4 20% 35% 26% 3	634
	21st to end	Night	13% 6% 27% 31% 21% 2	760
October	1st to 10th	Night	14% 7% 29% 32% 17% 1	760
	11th to 20th	Night	21% 9% 32% 29% 9%	760
	21st to end	Night	24% 9% 31% 27% 7% 1	836
November	1st to 10th	Night	16% 9% 36% 27% 11% 1	755
	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 2024-11-01 21:47:38. Version ac07

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