Huntsville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Huntsville 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	6% 10% 3 6% 4 3 4 3 5% 6% 51%	105152
	Night	6% 10% 3 7% 4 4 4 3 5% 6% 48%	102564
Transparency	Day	34% 4 8% 20% 20% 13%	104917
	Night	36% 5% 9% 20% 19% 11%	102388
Seeing	Day	12% 15% 32% 29% 11% 1	15215
	Night	12% 7% 26% 38% 17% 1	25291

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	6% 20% 7% 13% 4 4 4 3 4 5% 30%	2858
	11th to 20th	Day	6% 22% 8% 13% 5% 4 4 2 4 4 27%	2860
	21st to end	Day	7% 20% 7% 9% 4 4 4 3 3 5% 34%	3146
February	1st to 10th	Day	8% 18% 6% 12% 4 5% 4 4 4 4 31%	1710
	11th to 20th	Day	7% 19% 6% 12% 5% 3 4 3 4 5% 32%	1713
	21st to end	Day	5% 20% 7% 14% 5% 5% 3 4 4 5% 27%	1570
March	1st to 10th	Day	5% 22% 9% 10% 5% 4 4 3 4 5% 30%	3350
	11th to 20th	Day	4 12% 3 7% 4 4 4 4 4 6% 47%	3490
	21st to end	Day	10% 25% 6% 11% 5% 4 5% 3 5% 6% 21%	3825
April	1st to 10th	Day	10% 14% 4 7% 5% 5% 5% 4 5% 7% 35%	2118
	11th to 20th	Day	8% 15% 4 8% 5% 4 4 4 4 6% 39%	2405
	21st to end	Day	9% 11% 3 8% 5% 4 3 3 6% 7% 42%	2470
May	1st to 10th	Day	8% 16% 3 7% 5% 5% 4 4 6% 7% 35%	4110
	11th to 20th	Day	7% 5% 1 5% 3 4 4 4 5% 9% 53%	4071
	21st to end	Day	7% 7% 2 6% 4 4 5% 4 6% 7% 48%	4477
June	1st to 10th	Day	5% 5% 2 5% 3 4 4 4 7% 8% 54%	2655
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 7% 59%	2660
	21st to end	Day	3 2 1 4 3 2 3 2 3 5% 71%	2748
July	1st to 10th	Day	2 1 1 2 2 2 2 2 3 5% 77%	4177
	11th to 20th	Day	2 2 1 3 3 3 3 3 5% 8% 67%	4110
	21st to end	Day	3 3 1 3 3 3 3 3 5% 7% 66%	4454
August	1st to 10th	Day	3 2 1 4 4 3 3 3 4 6% 68%	4092
	11th to 20th	Day	2 2 1 3 3 3 4 3 5% 6% 67%	4028
	21st to end	Day	2 2 1 3 2 2 3 2 4 6% 74%	4495
September	1st to 10th	Day	4 3 1 2 2 2 3 2 4 6% 70%	2161
	11th to 20th	Day	5% 3 1 4 3 3 4 3 5% 6% 64%	2090
	21st to end	Day	6% 4 1 3 2 3 3 2 3 5% 68%	2090
October	1st to 10th	Day	6% 4 1 3 3 2 4 3 4 4 67%	3312
	11th to 20th	Day	8% 5% 2 4 3 4 4 3 6% 5% 57%	3150
	21st to end	Day	7% 8% 2 5% 3 3 3 2 4 6% 56%	3396
November	1st to 10th	Day	9% 11% 3 7% 5% 4 4 3 6% 6% 42%	1701
	11th to 20th	Day	11% 11% 3 6% 4 3 3 3 4 8% 43%	1708
	21st to end	Day	7% 13% 4 8% 5% 5% 3 3 4 5% 42%	1520
December	1st to 10th	Day	8% 14% 5% 10% 6% 4 5% 3 5% 5% 37%	1520
	11th to 20th	Day	10% 15% 6% 11% 5% 5% 4 3 5% 7% 29%	1926
	21st to end	Day	6% 13% 5% 11% 5% 4 5% 3 7% 7% 33%	2986
January	1st to 10th	Night	6% 16% 9% 14% 4 4 3 3 4 5% 32%	4097
	11th to 20th	Night	7% 22% 7% 14% 5% 4 4 3 4 5% 25%	4110
	21st to end	Night	7% 20% 6% 9% 4 4 4 3 5% 6% 32%	4521
February	1st to 10th	Night	9% 16% 5% 8% 5% 5% 5% 5% 5% 6% 32%	2470
	11th to 20th	Night	7% 15% 4 9% 4 3 4 3 4 6% 40%	2350
	21st to end	Night	5% 16% 5% 11% 6% 5% 4 4 6% 5% 33%	1884
March	1st to 10th	Night	9% 17% 5% 9% 5% 5% 5% 4 5% 5% 31%	3523
	11th to 20th	Night	4 9% 2 6% 5% 5% 4 4 6% 7% 48%	3490
	21st to end	Night	8% 18% 5% 10% 5% 4 4 3 5% 5% 33%	3828
April	1st to 10th	Night	9% 14% 3 6% 4 3 4 3 5% 5% 44%	2062
	11th to 20th	Night	6% 11% 4 7% 5% 5% 4 3 4 5% 45%	1720
	21st to end	Night	9% 9% 2 7% 4 3 3 4 6% 6% 48%	1710
May	1st to 10th	Night	10% 12% 2 7% 5% 4 4 4 5% 6% 39%	2860
	11th to 20th	Night	8% 5% 2 4 3 3 4 3 5% 6% 58%	2834
	21st to end	Night	9% 6% 2 6% 4 4 4 3 5% 7% 51%	3110
June	1st to 10th	Night	5% 5% 2 5% 4 3 4 4 5% 7% 56%	1520
	11th to 20th	Night	6% 3 2 3 3 3 3 2 4 7% 64%	1520
	21st to end	Night	3 3 1 4 2 2 2 3 3 6% 71%	1407
July	1st to 10th	Night	2 2 1 3 2 2 2 3 4 5% 74%	2764
	11th to 20th	Night	3 3 1 4 4 4 5% 4 6% 8% 59%	2860
	21st to end	Night	3 3 2 4 4 3 4 4 6% 7% 61%	3109
August	1st to 10th	Night	2 3 1 5% 4 4 4 4 5% 7% 61%	2847
	11th to 20th	Night	2 3 1 5% 4 5% 5% 3 5% 6% 60%	2811
	21st to end	Night	2 2 1 3 2 3 4 3 5% 5% 71%	3172
September	1st to 10th	Night	4 3 1 4 3 3 2 2 5% 5% 67%	2016
	11th to 20th	Night	6% 3 1 4 3 3 3 3 5% 5% 64%	2090
	21st to end	Night	6% 3 1 3 2 2 3 2 3 5% 70%	2090
October	1st to 10th	Night	5% 4 1 3 2 3 2 2 3 5% 70%	3662
	11th to 20th	Night	7% 6% 1 5% 3 3 3 3 5% 6% 58%	3778
	21st to end	Night	7% 7% 2 4 3 4 4 4 5% 7% 55%	4149
November	1st to 10th	Night	9% 9% 3 5% 4 4 3 3 5% 6% 48%	2450
	11th to 20th	Night	8% 8% 2 6% 5% 4 4 4 6% 8% 45%	2470
	21st to end	Night	5% 13% 4 6% 5% 4 5% 4 5% 6% 45%	2640
December	1st to 10th	Night	7% 13% 5% 10% 6% 4 4 3 4 7% 39%	2660
	11th to 20th	Night	10% 13% 4 9% 5% 5% 5% 4 5% 7% 33%	3271
	21st to end	Night	7% 13% 5% 11% 5% 5% 4 4 5% 6% 35%	4709

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	57% 5% 13% 18% 6% 1	2859
	11th to 20th	Day	62% 6% 12% 13% 5% 1	2860
	21st to end	Day	53% 6% 17% 15% 8% 1	3146
February	1st to 10th	Day	56% 6% 14% 14% 9% 1	1710
	11th to 20th	Day	55% 5% 13% 17% 9% 1	1722
	21st to end	Day	58% 5% 11% 16% 9% 1	1570
March	1st to 10th	Day	55% 5% 9% 20% 11% 1	3350
	11th to 20th	Day	38% 5% 9% 36% 10% 1	3490
	21st to end	Day	64% 5% 11% 15% 4 1	3825
April	1st to 10th	Day	48% 6% 12% 18% 13% 3	2118
	11th to 20th	Day	46% 5% 9% 22% 16% 2	2408
	21st to end	Day	41% 5% 10% 25% 18% 1	2470
May	1st to 10th	Day	43% 6% 7% 24% 16% 4	4110
	11th to 20th	Day	26% 5% 6% 33% 24% 5%	4074
	21st to end	Day	32% 6% 7% 29% 24% 2	4477
June	1st to 10th	Day	26% 5% 10% 25% 29% 6%	2655
	11th to 20th	Day	25% 3 7% 19% 28% 18%	2660
	21st to end	Day	16% 3 3 13% 32% 33%	2748
July	1st to 10th	Day	12% 3 3 8% 15% 59%	4113
	11th to 20th	Day	15% 3 4 10% 26% 42%	4041
	21st to end	Day	17% 3 4 10% 31% 34%	4314
August	1st to 10th	Day	19% 3 4 15% 30% 29%	4078
	11th to 20th	Day	17% 3 4 16% 35% 25%	4067
	21st to end	Day	13% 3 4 15% 36% 29%	4494
September	1st to 10th	Day	16% 3 5% 18% 31% 27%	2161
	11th to 20th	Day	20% 4 8% 18% 33% 18%	2090
	21st to end	Day	20% 3 6% 23% 36% 12%	2090
October	1st to 10th	Day	22% 3 5% 17% 33% 20%	3312
	11th to 20th	Day	28% 3 7% 29% 25% 8%	3150
	21st to end	Day	31% 3 10% 33% 20% 3	3396
November	1st to 10th	Day	43% 5% 13% 21% 16% 2	1701
	11th to 20th	Day	40% 5% 15% 25% 15%	1708
	21st to end	Day	44% 5% 13% 23% 14% 1	1520
December	1st to 10th	Day	48% 7% 16% 17% 9% 3	1520
	11th to 20th	Day	55% 5% 13% 19% 8%	1924
	21st to end	Day	48% 6% 13% 18% 13% 1	2986
January	1st to 10th	Night	55% 6% 10% 20% 8% 1	4097
	11th to 20th	Night	61% 6% 13% 13% 5% 2	4110
	21st to end	Night	53% 6% 16% 16% 8% 2	4521
February	1st to 10th	Night	51% 7% 13% 20% 8% 1	2470
	11th to 20th	Night	45% 5% 12% 21% 15% 2	2351
	21st to end	Night	50% 6% 11% 20% 11% 2	1884
March	1st to 10th	Night	50% 9% 7% 21% 12% 1	3523
	11th to 20th	Night	34% 5% 11% 35% 14% 1	3490
	21st to end	Night	53% 6% 10% 24% 6% 1	3828
April	1st to 10th	Night	42% 5% 13% 22% 13% 6%	2062
	11th to 20th	Night	40% 6% 10% 23% 20% 1	1720
	21st to end	Night	35% 6% 11% 27% 20% 1	1710
May	1st to 10th	Night	42% 7% 7% 22% 19% 3	2860
	11th to 20th	Night	25% 5% 7% 32% 25% 6%	2835
	21st to end	Night	32% 6% 7% 27% 27% 1	3110
June	1st to 10th	Night	25% 7% 9% 23% 30% 6%	1520
	11th to 20th	Night	21% 3 7% 20% 30% 19%	1520
	21st to end	Night	16% 3 3 13% 30% 35%	1407
July	1st to 10th	Night	13% 3 3 8% 15% 59%	2719
	11th to 20th	Night	22% 3 2 10% 30% 33%	2806
	21st to end	Night	21% 4 5% 9% 29% 32%	3011
August	1st to 10th	Night	23% 3 4 11% 31% 28%	2838
	11th to 20th	Night	25% 3 5% 13% 27% 26%	2838
	21st to end	Night	15% 3 5% 10% 30% 37%	3172
September	1st to 10th	Night	20% 3 4 15% 26% 31%	2016
	11th to 20th	Night	21% 4 6% 18% 30% 22%	2090
	21st to end	Night	19% 3 6% 19% 36% 17%	2090
October	1st to 10th	Night	19% 3 4 18% 37% 19%	3662
	11th to 20th	Night	29% 2 5% 30% 26% 8%	3778
	21st to end	Night	29% 3 8% 36% 21% 3	4149
November	1st to 10th	Night	37% 5% 11% 23% 20% 4	2450
	11th to 20th	Night	36% 5% 15% 27% 15% 2	2470
	21st to end	Night	40% 5% 12% 26% 14% 3	2640
December	1st to 10th	Night	47% 4 16% 20% 10% 3	2660
	11th to 20th	Night	50% 6% 14% 20% 10%	3272
	21st to end	Night	50% 4 15% 17% 13%	4709

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% 14% 33% 22% 9% 1	270
	11th to 20th	Day	17% 13% 37% 23% 10%	270
	21st to end	Day	12% 15% 35% 30% 7% 1	297
February	1st to 10th	Day	20% 20% 37% 19% 5%	270
	11th to 20th	Day	18% 21% 37% 18% 5% 1	318
	21st to end	Day	16% 23% 40% 16% 4 1	382
March	1st to 10th	Day	19% 24% 34% 19% 4	460
	11th to 20th	Day	17% 20% 36% 21% 6%	460
	21st to end	Day	23% 24% 33% 17% 2	506
April	1st to 10th	Day	20% 23% 28% 23% 7%	460
	11th to 20th	Day	21% 26% 31% 18% 4	452
	21st to end	Day	17% 24% 28% 24% 7% 1	460
May	1st to 10th	Day	19% 23% 32% 21% 5%	463
	11th to 20th	Day	14% 18% 33% 27% 8% 1	488
	21st to end	Day	15% 16% 31% 25% 12% 2	529
June	1st to 10th	Day	5% 15% 29% 35% 14% 2	675
	11th to 20th	Day	11% 13% 34% 32% 10% 1	680
	21st to end	Day	5% 11% 35% 36% 12% 1	625
July	1st to 10th	Day	3 9% 35% 41% 10% 2	486
	11th to 20th	Day	4 8% 37% 37% 12% 3	484
	21st to end	Day	4 3 33% 43% 15% 2	531
August	1st to 10th	Day	4 7% 40% 31% 16% 1	487
	11th to 20th	Day	4 8% 30% 39% 18% 1	477
	21st to end	Day	4 9% 29% 39% 18% 1	539
September	1st to 10th	Day	5% 8% 32% 32% 20% 3	490
	11th to 20th	Day	7% 13% 32% 32% 14% 2	490
	21st to end	Day	7% 13% 29% 32% 16% 3	490
October	1st to 10th	Day	12% 14% 22% 30% 19% 3	390
	11th to 20th	Day	9% 16% 25% 26% 20% 4	300
	21st to end	Day	13% 15% 29% 31% 11% 1	330
November	1st to 10th	Day	19% 15% 24% 29% 8% 4	279
	11th to 20th	Day	14% 11% 33% 29% 10% 2	270
	21st to end	Day	14% 11% 28% 31% 14% 2	270
December	1st to 10th	Day	14% 11% 34% 28% 10% 3	270
	11th to 20th	Day	16% 12% 40% 27% 6% 1	270
	21st to end	Day	22% 14% 32% 24% 6% 1	297
January	1st to 10th	Night	18% 7% 29% 31% 15% 1	760
	11th to 20th	Night	17% 8% 28% 33% 13% 1	760
	21st to end	Night	15% 8% 30% 34% 11% 2	836
February	1st to 10th	Night	18% 7% 34% 32% 9% 1	760
	11th to 20th	Night	14% 7% 33% 35% 11%	744
	21st to end	Night	11% 9% 39% 32% 8%	628
March	1st to 10th	Night	16% 10% 31% 33% 9% 1	760
	11th to 20th	Night	10% 9% 30% 38% 12% 1	760
	21st to end	Night	17% 11% 28% 34% 9% 1	836
April	1st to 10th	Night	17% 11% 27% 36% 9% 1	732
	11th to 20th	Night	12% 12% 33% 31% 11%	563
	21st to end	Night	11% 9% 25% 37% 17% 1	570
May	1st to 10th	Night	13% 7% 31% 35% 13%	570
	11th to 20th	Night	12% 4 25% 34% 23% 2	561
	21st to end	Night	11% 7% 19% 39% 22% 2	617
June	1st to 10th	Night	6% 8% 20% 40% 24% 2	570
	11th to 20th	Night	7% 7% 23% 45% 18%	570
	21st to end	Night	4 3 21% 44% 27% 2	410
July	1st to 10th	Night	4 2 20% 41% 31% 2	498
	11th to 20th	Night	5% 2 16% 47% 28% 1	552
	21st to end	Night	4 1 11% 48% 34% 1	624
August	1st to 10th	Night	4 2 15% 51% 27% 1	567
	11th to 20th	Night	4 1 18% 46% 30% 1	564
	21st to end	Night	5% 3 17% 44% 30% 1	627
September	1st to 10th	Night	5% 4 18% 44% 26% 2	686
	11th to 20th	Night	8% 3 20% 42% 24% 4	760
	21st to end	Night	8% 4 19% 40% 24% 6%	760
October	1st to 10th	Night	11% 6% 20% 41% 22% 1	760
	11th to 20th	Night	11% 5% 22% 38% 22% 1	760
	21st to end	Night	11% 5% 25% 39% 18% 2	836
November	1st to 10th	Night	12% 7% 23% 41% 15% 2	754
	11th to 20th	Night	12% 5% 32% 38% 11% 2	760
	21st to end	Night	12% 10% 27% 36% 14% 2	930
December	1st to 10th	Night	13% 8% 34% 34% 11% 1	950
	11th to 20th	Night	18% 8% 33% 32% 9% 1	950
	21st to end	Night	19% 11% 33% 31% 6% 1	946

Page generated at 2024-11-01 20:47:37. Version ac07

Copyright © 2024 Attilla Danko.