Barton Warnock Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barton Warnock Visitor Center clear sky chart from 2005-11-06 to 2024-11-05.

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 3 1 3 3 3 3 3 5% 7% 66%	104401
	Night	4 3 1 3 3 3 4 3 5% 8% 64%	103329
Transparency	Day	11% 28% 6% 14% 19% 21%	104187
	Night	12% 29% 6% 14% 18% 21%	103132
Seeing	Day	5% 5% 18% 33% 29% 9%	14333
	Night	5% 3 19% 46% 25% 1	24533

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 4 5% 74%	3167
	11th to 20th	Day	4 3 1 2 2 2 2 2 3 5% 74%	3170
	21st to end	Day	4 5% 2 4 3 3 3 3 4 6% 62%	3487
February	1st to 10th	Day	3 4 1 5% 3 3 4 3 5% 5% 64%	1900
	11th to 20th	Day	4 4 2 5% 3 3 3 3 4 6% 63%	1849
	21st to end	Day	3 4 1 2 2 2 3 3 5% 6% 69%	1570
March	1st to 10th	Day	2 3 2 5% 3 3 4 4 5% 8% 61%	3130
	11th to 20th	Day	9% 3 1 3 3 3 3 3 5% 6% 60%	3356
	21st to end	Day	2 2 1 3 3 3 3 3 5% 7% 67%	4151
April	1st to 10th	Day	2 2 1 3 2 3 4 4 5% 7% 68%	2280
	11th to 20th	Day	2 3 1 2 2 2 3 3 5% 6% 72%	2251
	21st to end	Day	3 3 1 3 3 2 3 2 4 6% 71%	2280
May	1st to 10th	Day	1 1 1 2 2 2 2 2 3 6% 79%	3800
	11th to 20th	Day	2 2 1 2 2 2 2 3 4 6% 73%	3765
	21st to end	Day	1 1 1 1 2 3 3 5% 6% 75%	4259
June	1st to 10th	Day	1 1 1 1 3 3 4 6% 7% 71%	2470
	11th to 20th	Day	2 2 1 3 3 3 4 4 5% 8% 66%	2470
	21st to end	Day	2 2 1 3 3 3 4 4 7% 10% 61%	2345
July	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 9% 62%	3800
	11th to 20th	Day	2 2 1 3 3 3 3 5% 7% 11% 60%	3800
	21st to end	Day	3 2 1 3 3 3 5% 5% 6% 11% 58%	4118
August	1st to 10th	Day	1 1 2 3 2 3 3 6% 11% 66%	3784
	11th to 20th	Day	3 2 1 4 3 3 4 4 6% 10% 60%	3726
	21st to end	Day	3 2 1 3 3 3 5% 4 8% 10% 59%	4180
September	1st to 10th	Day	5% 5% 2 6% 5% 4 5% 4 7% 10% 47%	2280
	11th to 20th	Day	7% 5% 2 5% 4 4 4 4 6% 10% 50%	2151
	21st to end	Day	5% 3 1 4 3 3 4 3 5% 7% 62%	2090
October	1st to 10th	Day	2 1 1 2 2 1 2 2 3 5% 79%	3480
	11th to 20th	Day	4 2 1 2 2 2 3 3 4 7% 72%	3320
	21st to end	Day	3 2 1 1 1 1 1 1 2 3 83%	3438
November	1st to 10th	Day	6% 2 2 2 2 2 2 2 3 5% 71%	1880
	11th to 20th	Day	4 3 1 3 3 2 3 2 5% 5% 70%	1710
	21st to end	Day	6% 3 2 3 3 3 3 3 5% 5% 65%	1710
December	1st to 10th	Day	5% 5% 1 3 4 3 2 3 5% 6% 63%	1710
	11th to 20th	Day	3 5% 2 5% 4 4 4 3 6% 7% 57%	2161
	21st to end	Day	3 3 1 3 2 2 4 4 6% 7% 65%	3363
January	1st to 10th	Night	3 2 1 2 1 2 2 2 3 5% 78%	3788
	11th to 20th	Night	4 1 1 2 1 2 2 2 3 5% 76%	3800
	21st to end	Night	6% 5% 2 5% 3 3 4 3 6% 7% 57%	4180
February	1st to 10th	Night	4 4 1 4 2 3 3 3 5% 5% 65%	2280
	11th to 20th	Night	5% 4 1 4 3 3 4 3 5% 7% 60%	2218
	21st to end	Night	5% 3 1 2 3 3 4 3 4 6% 66%	1884
March	1st to 10th	Night	3 3 2 5% 3 4 4 4 5% 7% 60%	3734
	11th to 20th	Night	11% 4 1 3 3 2 2 3 5% 6% 61%	3614
	21st to end	Night	3 3 1 3 3 3 3 4 5% 6% 65%	3488
April	1st to 10th	Night	3 4 1 4 3 4 4 3 4 6% 65%	1900
	11th to 20th	Night	3 2 1 3 3 2 3 3 6% 7% 68%	1877
	21st to end	Night	3 3 1 2 2 2 4 3 4 5% 71%	1900
May	1st to 10th	Night	2 1 1 3 2 2 2 2 4 5% 76%	3170
	11th to 20th	Night	5% 2 1 3 3 3 4 3 5% 6% 66%	3140
	21st to end	Night	2 2 1 3 3 3 4 3 5% 7% 68%	3318
June	1st to 10th	Night	3 2 1 3 3 3 5% 5% 9% 11% 56%	1710
	11th to 20th	Night	2 2 1 4 4 5% 5% 5% 8% 10% 54%	1710
	21st to end	Night	3 2 1 4 3 3 4 4 8% 11% 56%	1824
July	1st to 10th	Night	2 2 1 4 3 4 5% 5% 9% 13% 51%	3170
	11th to 20th	Night	2 1 1 3 3 3 4 4 8% 12% 58%	3170
	21st to end	Night	2 2 1 3 3 4 5% 5% 8% 11% 57%	3445
August	1st to 10th	Night	1 1 2 3 3 4 5% 9% 14% 57%	3155
	11th to 20th	Night	2 2 1 3 3 4 4 4 8% 12% 57%	3113
	21st to end	Night	1 3 1 3 4 5% 5% 5% 8% 13% 52%	3487
September	1st to 10th	Night	4 3 1 5% 5% 5% 6% 4 7% 10% 49%	1900
	11th to 20th	Night	6% 4 2 7% 4 4 6% 6% 7% 10% 44%	2028
	21st to end	Night	5% 4 2 5% 4 4 4 4 6% 10% 53%	2090
October	1st to 10th	Night	2 1 1 2 2 2 3 3 4 6% 73%	3480
	11th to 20th	Night	5% 2 1 3 2 2 4 2 5% 6% 69%	3584
	21st to end	Night	3 2 2 1 1 1 1 2 4 82%	4120
November	1st to 10th	Night	6% 2 1 2 2 1 2 2 3 4 76%	2280
	11th to 20th	Night	4 2 1 2 2 2 3 3 5% 5% 70%	2465
	21st to end	Night	5% 3 1 3 3 3 4 3 4 6% 66%	2470
December	1st to 10th	Night	6% 3 1 3 2 3 4 4 5% 6% 62%	2470
	11th to 20th	Night	3 4 1 4 3 3 3 4 5% 8% 63%	3036
	21st to end	Night	3 3 1 3 2 2 3 4 5% 8% 64%	4331

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	7% 27% 4 7% 24% 32%	3168
	11th to 20th	Day	8% 27% 3 12% 27% 22%	3170
	21st to end	Day	18% 25% 4 23% 20% 11%	3487
February	1st to 10th	Day	12% 39% 4 7% 15% 23%	1900
	11th to 20th	Day	13% 40% 3 8% 18% 17%	1859
	21st to end	Day	9% 37% 3 8% 19% 23%	1570
March	1st to 10th	Day	12% 23% 6% 8% 24% 27%	3130
	11th to 20th	Day	17% 22% 6% 11% 17% 27%	3356
	21st to end	Day	11% 20% 6% 6% 19% 37%	4151
April	1st to 10th	Day	10% 34% 5% 8% 14% 30%	2280
	11th to 20th	Day	8% 32% 4 8% 16% 31%	2254
	21st to end	Day	10% 33% 4 7% 15% 31%	2280
May	1st to 10th	Day	7% 21% 3 9% 16% 45%	3800
	11th to 20th	Day	9% 23% 6% 9% 17% 36%	3768
	21st to end	Day	6% 22% 5% 13% 15% 39%	4259
June	1st to 10th	Day	6% 34% 5% 15% 20% 19%	2470
	11th to 20th	Day	8% 35% 7% 10% 20% 21%	2470
	21st to end	Day	13% 36% 8% 14% 18% 11%	2345
July	1st to 10th	Day	13% 24% 14% 25% 18% 7%	3741
	11th to 20th	Day	13% 23% 10% 33% 16% 6%	3737
	21st to end	Day	16% 24% 11% 22% 17% 10%	3988
August	1st to 10th	Day	9% 23% 7% 26% 28% 7%	3772
	11th to 20th	Day	13% 23% 10% 30% 20% 4	3762
	21st to end	Day	14% 25% 12% 23% 19% 6%	4179
September	1st to 10th	Day	21% 37% 10% 12% 10% 9%	2280
	11th to 20th	Day	20% 36% 7% 13% 16% 8%	2151
	21st to end	Day	12% 35% 5% 14% 18% 16%	2090
October	1st to 10th	Day	6% 22% 4 9% 22% 38%	3480
	11th to 20th	Day	8% 21% 8% 17% 15% 31%	3320
	21st to end	Day	5% 21% 2 9% 35% 29%	3438
November	1st to 10th	Day	4 41% 3 11% 21% 20%	1880
	11th to 20th	Day	6% 44% 5% 11% 19% 14%	1710
	21st to end	Day	11% 45% 5% 14% 12% 14%	1710
December	1st to 10th	Day	11% 44% 5% 7% 20% 13%	1710
	11th to 20th	Day	16% 36% 4 14% 20% 10%	2159
	21st to end	Day	11% 27% 4 10% 27% 22%	3363
January	1st to 10th	Night	5% 26% 2 7% 28% 32%	3788
	11th to 20th	Night	7% 27% 4 10% 23% 30%	3800
	21st to end	Night	19% 26% 4 18% 21% 11%	4180
February	1st to 10th	Night	12% 38% 4 7% 16% 24%	2280
	11th to 20th	Night	15% 40% 4 7% 15% 19%	2218
	21st to end	Night	9% 38% 2 6% 19% 25%	1884
March	1st to 10th	Night	15% 23% 4 6% 20% 32%	3734
	11th to 20th	Night	19% 22% 6% 11% 17% 25%	3614
	21st to end	Night	14% 21% 6% 8% 18% 33%	3488
April	1st to 10th	Night	13% 34% 4 8% 13% 27%	1900
	11th to 20th	Night	10% 33% 5% 9% 14% 30%	1877
	21st to end	Night	11% 33% 4 9% 14% 28%	1900
May	1st to 10th	Night	9% 21% 3 9% 13% 45%	3170
	11th to 20th	Night	14% 24% 7% 10% 11% 34%	3141
	21st to end	Night	11% 23% 6% 12% 14% 34%	3319
June	1st to 10th	Night	10% 37% 9% 18% 14% 12%	1710
	11th to 20th	Night	14% 36% 7% 11% 16% 16%	1710
	21st to end	Night	15% 37% 8% 14% 16% 10%	1824
July	1st to 10th	Night	16% 24% 16% 24% 15% 4	3120
	11th to 20th	Night	13% 24% 12% 33% 14% 4	3110
	21st to end	Night	17% 25% 11% 23% 18% 6%	3336
August	1st to 10th	Night	10% 24% 7% 30% 26% 3	3144
	11th to 20th	Night	13% 23% 13% 33% 17% 2	3143
	21st to end	Night	16% 26% 14% 24% 18% 3	3487
September	1st to 10th	Night	20% 38% 12% 13% 9% 8%	1900
	11th to 20th	Night	23% 37% 9% 11% 13% 6%	2028
	21st to end	Night	15% 36% 8% 13% 14% 14%	2090
October	1st to 10th	Night	7% 22% 5% 8% 18% 39%	3480
	11th to 20th	Night	13% 22% 7% 15% 12% 31%	3584
	21st to end	Night	6% 21% 2 11% 33% 27%	4120
November	1st to 10th	Night	5% 40% 2 9% 22% 22%	2280
	11th to 20th	Night	7% 44% 5% 9% 16% 19%	2465
	21st to end	Night	10% 44% 6% 11% 13% 16%	2470
December	1st to 10th	Night	11% 45% 5% 9% 16% 14%	2470
	11th to 20th	Night	12% 36% 4 15% 21% 12%	3037
	21st to end	Night	12% 27% 5% 10% 24% 22%	4331

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	11% 4 28% 36% 18% 2	270
	11th to 20th	Day	5% 6% 23% 42% 23% 1	270
	21st to end	Day	4 11% 28% 36% 19% 2	297
February	1st to 10th	Day	7% 10% 24% 30% 27% 3	270
	11th to 20th	Day	10% 11% 23% 36% 18% 2	270
	21st to end	Day	7% 12% 30% 39% 11% 2	225
March	1st to 10th	Day	7% 5% 32% 36% 19% 1	270
	11th to 20th	Day	7% 13% 34% 29% 12% 4	378
	21st to end	Day	8% 15% 33% 32% 11% 1	506
April	1st to 10th	Day	5% 14% 36% 33% 11% 2	460
	11th to 20th	Day	3 15% 40% 29% 10% 2	452
	21st to end	Day	7% 12% 31% 40% 10%	460
May	1st to 10th	Day	3 9% 33% 39% 13% 3	463
	11th to 20th	Day	2 9% 31% 40% 17% 2	488
	21st to end	Day	3 4 25% 44% 22% 2	595
June	1st to 10th	Day	1 3 15% 39% 37% 5%	680
	11th to 20th	Day	2 12% 40% 41% 5%	680
	21st to end	Day	4 1 11% 34% 43% 8%	555
July	1st to 10th	Day	4 1 8% 27% 38% 21%	486
	11th to 20th	Day	2 6% 34% 41% 17%	484
	21st to end	Day	2 1 4 36% 42% 15%	531
August	1st to 10th	Day	2 1 5% 21% 51% 20%	487
	11th to 20th	Day	4 1 7% 27% 40% 22%	477
	21st to end	Day	3 1 7% 26% 40% 22%	539
September	1st to 10th	Day	7% 1 6% 32% 38% 15%	490
	11th to 20th	Day	6% 6% 20% 48% 20%	361
	21st to end	Day	7% 8% 23% 40% 22%	300
October	1st to 10th	Day	4 2 8% 27% 42% 17%	300
	11th to 20th	Day	9% 1 12% 29% 32% 16%	300
	21st to end	Day	8% 3 13% 28% 34% 13%	330
November	1st to 10th	Day	7% 5% 13% 30% 34% 11%	282
	11th to 20th	Day	8% 8% 17% 25% 31% 11%	270
	21st to end	Day	7% 10% 22% 32% 24% 5%	270
December	1st to 10th	Day	9% 5% 14% 32% 35% 6%	270
	11th to 20th	Day	4 9% 24% 39% 21% 1	270
	21st to end	Day	5% 6% 21% 45% 21% 1	297
January	1st to 10th	Night	7% 2 21% 52% 17% 1	760
	11th to 20th	Night	8% 3 19% 51% 19%	760
	21st to end	Night	7% 5% 25% 49% 14% 1	836
February	1st to 10th	Night	6% 5% 26% 44% 19% 1	760
	11th to 20th	Night	6% 5% 24% 53% 11% 1	744
	21st to end	Night	7% 5% 30% 50% 8%	628
March	1st to 10th	Night	6% 6% 33% 44% 10% 1	760
	11th to 20th	Night	9% 6% 26% 44% 14% 1	760
	21st to end	Night	5% 7% 35% 43% 10%	638
April	1st to 10th	Night	4 7% 33% 46% 9%	570
	11th to 20th	Night	3 8% 39% 44% 7%	563
	21st to end	Night	4 7% 36% 47% 7%	570
May	1st to 10th	Night	4 4 31% 52% 9%	570
	11th to 20th	Night	5% 5% 29% 50% 10%	561
	21st to end	Night	3 2 29% 53% 13%	617
June	1st to 10th	Night	2 2 18% 58% 19% 1	570
	11th to 20th	Night	2 1 17% 57% 22%	570
	21st to end	Night	3 1 13% 48% 34%	570
July	1st to 10th	Night	4 1 12% 41% 40% 2	555
	11th to 20th	Night	3 5% 42% 47% 2	552
	21st to end	Night	4 6% 40% 48% 2	624
August	1st to 10th	Night	2 1 4 31% 60% 2	567
	11th to 20th	Night	3 1 5% 32% 54% 4	564
	21st to end	Night	3 1 6% 34% 53% 3	627
September	1st to 10th	Night	5% 1 6% 35% 51% 2	570
	11th to 20th	Night	8% 1 8% 37% 46% 1	570
	21st to end	Night	6% 1 9% 43% 39% 2	570
October	1st to 10th	Night	4 1 10% 47% 37% 1	570
	11th to 20th	Night	8% 1 12% 50% 27% 2	644
	21st to end	Night	5% 3 13% 43% 32% 4	836
November	1st to 10th	Night	7% 2 10% 45% 33% 3	760
	11th to 20th	Night	4 4 14% 49% 29% 1	945
	21st to end	Night	6% 3 22% 46% 20% 2	950
December	1st to 10th	Night	7% 2 14% 51% 24% 1	950
	11th to 20th	Night	5% 3 22% 51% 18% 1	950
	21st to end	Night	5% 4 22% 52% 15% 2	922

Page generated at 2024-11-03 01:11:22. Version ac07

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