Fort Leaton State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Leaton State Historic Site clear sky chart from 2005-11-06 to 2024-11-11.

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 2 1 3 2 3 3 3 5% 7% 67%	104225
	Night	3 3 1 4 3 3 4 3 6% 8% 63%	103616
Transparency	Day	8% 46% 5% 11% 15% 15%	104011
	Night	9% 47% 5% 10% 14% 15%	103419
Seeing	Day	4 4 13% 32% 31% 17%	14139
	Night	5% 3 21% 49% 20% 1	24545

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 2 1 3 2 2 3 2 5% 6% 68%	3167
	11th to 20th	Day	4 3 1 3 2 1 2 2 3 5% 74%	3170
	21st to end	Day	4 5% 2 5% 4 4 4 3 5% 6% 59%	3487
February	1st to 10th	Day	3 3 1 4 4 3 4 4 5% 6% 63%	1900
	11th to 20th	Day	4 4 1 4 3 3 3 3 5% 6% 63%	1849
	21st to end	Day	3 3 1 2 2 3 3 3 5% 7% 68%	1570
March	1st to 10th	Day	3 3 1 4 3 3 3 4 6% 9% 62%	3130
	11th to 20th	Day	6% 3 1 3 2 3 3 3 5% 7% 63%	3476
	21st to end	Day	1 3 1 3 3 3 3 4 6% 8% 64%	4092
April	1st to 10th	Day	3 2 1 3 3 3 3 3 5% 6% 69%	2280
	11th to 20th	Day	1 3 1 3 2 2 3 3 4 6% 72%	2251
	21st to end	Day	3 2 1 2 2 2 2 2 4 6% 74%	2280
May	1st to 10th	Day	2 2 1 2 2 2 2 2 2 4 81%	3800
	11th to 20th	Day	1 1 1 2 2 2 3 3 5% 6% 75%	3765
	21st to end	Day	1 1 1 1 1 2 3 4 5% 81%	4141
June	1st to 10th	Day	1 1 2 2 2 3 3 5% 9% 72%	2382
	11th to 20th	Day	2 2 1 2 2 2 3 3 6% 7% 70%	2374
	21st to end	Day	2 2 1 3 2 3 4 4 6% 8% 64%	2280
July	1st to 10th	Day	2 2 1 3 3 4 5% 5% 8% 9% 58%	3800
	11th to 20th	Day	2 2 1 2 2 3 4 4 7% 10% 64%	3800
	21st to end	Day	3 2 1 3 3 4 5% 4 7% 10% 57%	4118
August	1st to 10th	Day	1 2 1 2 3 3 4 4 6% 10% 64%	3784
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 10% 61%	3726
	21st to end	Day	2 2 1 3 3 4 5% 5% 6% 10% 58%	4180
September	1st to 10th	Day	6% 5% 2 4 4 4 4 4 6% 10% 51%	2280
	11th to 20th	Day	7% 5% 2 5% 3 3 4 4 5% 8% 54%	2186
	21st to end	Day	5% 3 1 4 3 3 3 4 5% 7% 62%	2090
October	1st to 10th	Day	1 1 1 2 2 2 2 3 4 81%	3480
	11th to 20th	Day	3 2 1 2 2 2 2 3 3 4 75%	3197
	21st to end	Day	2 2 1 1 1 1 1 1 2 3 84%	3438
November	1st to 10th	Day	4 3 2 3 2 3 3 2 3 4 72%	1959
	11th to 20th	Day	4 3 1 3 2 3 3 3 4 6% 68%	1753
	21st to end	Day	6% 4 2 4 3 3 3 3 5% 6% 62%	1710
December	1st to 10th	Day	6% 4 2 4 2 3 4 3 6% 9% 58%	1710
	11th to 20th	Day	2 5% 2 6% 4 4 5% 3 5% 7% 55%	2161
	21st to end	Day	3 2 1 4 3 3 3 3 7% 8% 62%	3459
January	1st to 10th	Night	3 2 1 2 1 2 2 2 4 7% 75%	3788
	11th to 20th	Night	4 1 2 1 2 2 2 4 5% 76%	3800
	21st to end	Night	6% 5% 2 5% 4 3 4 4 6% 7% 55%	4180
February	1st to 10th	Night	4 3 1 4 2 3 3 3 5% 9% 64%	2280
	11th to 20th	Night	4 4 2 4 3 3 4 3 5% 8% 59%	2218
	21st to end	Night	4 3 1 3 3 2 4 3 6% 7% 63%	1884
March	1st to 10th	Night	3 4 1 5% 4 3 4 3 5% 9% 60%	3734
	11th to 20th	Night	7% 4 1 3 3 3 3 2 4 6% 62%	3500
	21st to end	Night	4 4 2 4 3 3 3 3 5% 7% 63%	3551
April	1st to 10th	Night	3 3 1 4 3 3 4 3 5% 5% 66%	1900
	11th to 20th	Night	3 3 1 4 3 2 4 3 5% 7% 65%	1877
	21st to end	Night	3 3 1 3 2 2 3 3 3 6% 72%	1900
May	1st to 10th	Night	2 1 2 1 2 2 3 4 4 78%	3170
	11th to 20th	Night	3 3 1 3 3 2 4 3 4 6% 66%	3140
	21st to end	Night	2 2 1 3 3 3 3 3 5% 8% 68%	3446
June	1st to 10th	Night	2 2 1 4 4 4 5% 5% 10% 11% 53%	1777
	11th to 20th	Night	3 2 2 4 5% 5% 5% 5% 7% 11% 51%	1782
	21st to end	Night	3 3 1 4 4 4 5% 4 8% 10% 54%	1900
July	1st to 10th	Night	2 2 1 5% 4 5% 6% 6% 9% 12% 48%	3170
	11th to 20th	Night	2 1 1 3 2 3 4 4 6% 12% 61%	3170
	21st to end	Night	2 3 1 4 5% 5% 6% 5% 7% 11% 51%	3445
August	1st to 10th	Night	2 1 1 4 4 4 5% 5% 9% 11% 54%	3155
	11th to 20th	Night	3 2 1 3 4 4 5% 6% 8% 13% 52%	3113
	21st to end	Night	2 3 1 5% 3 4 6% 5% 9% 13% 49%	3487
September	1st to 10th	Night	4 5% 2 6% 5% 4 6% 5% 6% 9% 48%	1900
	11th to 20th	Night	5% 4 2 6% 5% 5% 6% 6% 8% 9% 42%	1991
	21st to end	Night	4 3 2 5% 5% 4 5% 5% 7% 9% 51%	2090
October	1st to 10th	Night	1 2 1 3 2 2 3 2 4 5% 74%	3480
	11th to 20th	Night	4 3 1 4 3 3 2 2 4 7% 68%	3711
	21st to end	Night	2 1 1 1 1 1 2 2 3 4 82%	4120
November	1st to 10th	Night	5% 2 1 2 1 2 2 2 3 4 76%	2340
	11th to 20th	Night	3 3 1 3 2 3 3 3 5% 6% 69%	2409
	21st to end	Night	4 3 1 4 3 3 3 3 4 6% 65%	2470
December	1st to 10th	Night	5% 3 1 3 3 3 2 3 5% 8% 63%	2470
	11th to 20th	Night	2 4 1 4 3 3 3 4 6% 8% 62%	3036
	21st to end	Night	3 3 1 4 3 3 4 3 6% 9% 62%	4232

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	8% 37% 2 8% 18% 26%	3168
	11th to 20th	Day	6% 36% 3 9% 29% 17%	3170
	21st to end	Day	15% 40% 4 17% 18% 4	3487
February	1st to 10th	Day	9% 65% 2 5% 9% 10%	1900
	11th to 20th	Day	8% 64% 3 7% 7% 11%	1859
	21st to end	Day	7% 65% 1 4 10% 13%	1570
March	1st to 10th	Day	12% 41% 4 9% 18% 16%	3130
	11th to 20th	Day	11% 41% 4 10% 16% 17%	3476
	21st to end	Day	10% 41% 3 5% 18% 24%	4092
April	1st to 10th	Day	6% 64% 2 4 9% 15%	2280
	11th to 20th	Day	7% 65% 2 5% 8% 13%	2254
	21st to end	Day	5% 65% 1 4 10% 15%	2280
May	1st to 10th	Day	3 39% 1 5% 11% 41%	3800
	11th to 20th	Day	4 40% 3 7% 13% 32%	3768
	21st to end	Day	3 39% 2 7% 12% 38%	4141
June	1st to 10th	Day	5% 65% 4 9% 10% 7%	2382
	11th to 20th	Day	5% 64% 3 7% 10% 11%	2374
	21st to end	Day	5% 63% 5% 9% 10% 8%	2280
July	1st to 10th	Day	10% 37% 12% 21% 16% 5%	3741
	11th to 20th	Day	6% 37% 10% 25% 17% 4	3737
	21st to end	Day	10% 37% 7% 17% 22% 7%	3988
August	1st to 10th	Day	9% 38% 6% 21% 19% 7%	3772
	11th to 20th	Day	7% 39% 10% 23% 16% 5%	3762
	21st to end	Day	9% 39% 9% 22% 16% 5%	4179
September	1st to 10th	Day	10% 60% 6% 9% 8% 7%	2280
	11th to 20th	Day	10% 61% 6% 9% 10% 5%	2186
	21st to end	Day	11% 60% 4 11% 10% 4	2090
October	1st to 10th	Day	4 37% 3 6% 16% 34%	3480
	11th to 20th	Day	6% 37% 5% 13% 12% 26%	3197
	21st to end	Day	5% 35% 1 6% 31% 22%	3438
November	1st to 10th	Day	13% 56% 4 8% 9% 9%	1959
	11th to 20th	Day	10% 60% 5% 11% 8% 5%	1753
	21st to end	Day	10% 60% 3 8% 12% 7%	1710
December	1st to 10th	Day	11% 60% 4 12% 9% 5%	1710
	11th to 20th	Day	14% 49% 5% 9% 17% 5%	2159
	21st to end	Day	11% 38% 4 10% 21% 17%	3459
January	1st to 10th	Night	7% 35% 2 4 27% 26%	3788
	11th to 20th	Night	5% 36% 4 9% 21% 27%	3800
	21st to end	Night	17% 42% 4 13% 18% 7%	4180
February	1st to 10th	Night	6% 64% 2 7% 10% 10%	2280
	11th to 20th	Night	8% 64% 3 5% 9% 11%	2218
	21st to end	Night	8% 65% 2 5% 8% 12%	1884
March	1st to 10th	Night	15% 41% 3 7% 14% 21%	3734
	11th to 20th	Night	12% 43% 5% 12% 14% 14%	3500
	21st to end	Night	13% 42% 3 5% 14% 23%	3551
April	1st to 10th	Night	7% 65% 2 4 8% 16%	1900
	11th to 20th	Night	7% 66% 3 5% 7% 13%	1877
	21st to end	Night	6% 65% 2 5% 9% 13%	1900
May	1st to 10th	Night	3 39% 1 4 10% 43%	3170
	11th to 20th	Night	8% 40% 4 8% 6% 33%	3141
	21st to end	Night	6% 40% 3 9% 11% 31%	3447
June	1st to 10th	Night	8% 67% 4 8% 9% 4	1777
	11th to 20th	Night	10% 65% 3 5% 10% 7%	1782
	21st to end	Night	6% 63% 6% 9% 8% 7%	1900
July	1st to 10th	Night	15% 39% 14% 19% 12% 2	3120
	11th to 20th	Night	8% 37% 8% 29% 15% 3	3110
	21st to end	Night	11% 36% 9% 18% 21% 5%	3336
August	1st to 10th	Night	11% 38% 6% 19% 22% 4	3144
	11th to 20th	Night	10% 39% 9% 24% 14% 4	3143
	21st to end	Night	12% 39% 11% 21% 15% 2	3487
September	1st to 10th	Night	11% 61% 6% 8% 7% 6%	1900
	11th to 20th	Night	14% 63% 4 7% 7% 5%	1991
	21st to end	Night	12% 62% 6% 9% 8% 3	2090
October	1st to 10th	Night	7% 38% 3 4 12% 36%	3480
	11th to 20th	Night	9% 37% 6% 10% 10% 29%	3711
	21st to end	Night	5% 36% 2 8% 28% 21%	4120
November	1st to 10th	Night	11% 56% 5% 8% 10% 11%	2340
	11th to 20th	Night	11% 60% 3 10% 9% 6%	2409
	21st to end	Night	9% 59% 4 7% 11% 10%	2470
December	1st to 10th	Night	10% 60% 3 11% 9% 7%	2470
	11th to 20th	Night	10% 49% 4 10% 18% 9%	3037
	21st to end	Night	11% 38% 4 9% 24% 14%	4232

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	8% 3 19% 41% 26% 4	270
	11th to 20th	Day	3 6% 15% 44% 28% 5%	270
	21st to end	Day	3 7% 23% 39% 25% 4	297
February	1st to 10th	Day	8% 4 16% 36% 30% 6%	270
	11th to 20th	Day	9% 6% 17% 43% 22% 3	270
	21st to end	Day	5% 8% 23% 47% 16% 1	225
March	1st to 10th	Day	8% 4 17% 47% 20% 3	270
	11th to 20th	Day	8% 10% 25% 32% 20% 6%	446
	21st to end	Day	4 14% 22% 38% 20% 2	506
April	1st to 10th	Day	5% 8% 25% 40% 20% 2	460
	11th to 20th	Day	2 12% 29% 37% 17% 3	452
	21st to end	Day	5% 7% 22% 45% 21% 1	460
May	1st to 10th	Day	3 7% 19% 43% 23% 5%	463
	11th to 20th	Day	2 5% 20% 40% 26% 6%	488
	21st to end	Day	3 3 18% 38% 34% 4	529
June	1st to 10th	Day	2 1 10% 35% 40% 12%	592
	11th to 20th	Day	3 1 7% 29% 45% 14%	584
	21st to end	Day	2 1 7% 30% 37% 23%	490
July	1st to 10th	Day	5% 6% 22% 30% 37%	486
	11th to 20th	Day	2 3 22% 34% 39%	484
	21st to end	Day	2 1 3 24% 40% 30%	531
August	1st to 10th	Day	2 1 4 17% 36% 40%	487
	11th to 20th	Day	5% 1 5% 21% 32% 36%	477
	21st to end	Day	4 1 5% 22% 32% 37%	539
September	1st to 10th	Day	6% 2 6% 26% 33% 28%	490
	11th to 20th	Day	7% 1 4 16% 39% 33%	396
	21st to end	Day	7% 5% 16% 38% 33%	300
October	1st to 10th	Day	4 2 5% 22% 34% 33%	300
	11th to 20th	Day	7% 2 9% 25% 33% 24%	300
	21st to end	Day	4 3 9% 26% 33% 25%	330
November	1st to 10th	Day	3 3 9% 30% 42% 13%	300
	11th to 20th	Day	4 6% 10% 30% 33% 17%	270
	21st to end	Day	10% 5% 15% 36% 28% 7%	270
December	1st to 10th	Day	7% 3 8% 33% 38% 12%	270
	11th to 20th	Day	4 3 19% 42% 29% 4	270
	21st to end	Day	6% 3 15% 42% 30% 3	297
January	1st to 10th	Night	6% 2 22% 51% 17%	760
	11th to 20th	Night	8% 3 20% 51% 18%	760
	21st to end	Night	6% 4 27% 49% 13%	836
February	1st to 10th	Night	5% 5% 27% 46% 17%	760
	11th to 20th	Night	7% 6% 27% 50% 10%	744
	21st to end	Night	5% 7% 34% 48% 6%	628
March	1st to 10th	Night	8% 5% 33% 44% 9%	760
	11th to 20th	Night	9% 6% 33% 39% 12%	760
	21st to end	Night	5% 6% 36% 44% 9%	675
April	1st to 10th	Night	4 7% 39% 45% 6%	570
	11th to 20th	Night	4 8% 41% 42% 6%	563
	21st to end	Night	3 7% 39% 45% 5%	570
May	1st to 10th	Night	5% 6% 37% 44% 8%	570
	11th to 20th	Night	5% 5% 35% 47% 8% 1	561
	21st to end	Night	4 5% 31% 50% 10%	617
June	1st to 10th	Night	3 2 24% 56% 15%	570
	11th to 20th	Night	3 1 22% 52% 21%	570
	21st to end	Night	2 1 17% 58% 21% 1	570
July	1st to 10th	Night	3 1 13% 52% 29% 2	555
	11th to 20th	Night	4 2 7% 56% 31% 1	552
	21st to end	Night	3 2 7% 51% 35% 3	624
August	1st to 10th	Night	3 1 6% 43% 44% 3	567
	11th to 20th	Night	5% 1 5% 41% 43% 5%	564
	21st to end	Night	5% 1 6% 48% 37% 3	627
September	1st to 10th	Night	5% 2 10% 48% 34% 2	570
	11th to 20th	Night	6% 1 11% 50% 32% 1	570
	21st to end	Night	4 1 12% 52% 29% 2	570
October	1st to 10th	Night	4 1 12% 58% 25% 1	570
	11th to 20th	Night	7% 2 19% 46% 24% 2	719
	21st to end	Night	4 2 16% 45% 29% 4	836
November	1st to 10th	Night	6% 2 14% 46% 31% 2	780
	11th to 20th	Night	4 4 14% 52% 24% 1	885
	21st to end	Night	6% 2 21% 49% 20% 2	950
December	1st to 10th	Night	7% 2 14% 53% 23% 1	950
	11th to 20th	Night	4 3 22% 53% 19%	950
	21st to end	Night	5% 2 22% 53% 17% 1	862

Page generated at 2024-11-08 05:44:48. Version ac07

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