Cameron County Dark Skies
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cameron County Dark Skies clear sky chart from 2005-11-06 to 2024-11-25.

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	17% 11% 4 8% 5% 5% 5% 4 5% 7% 30%	101565
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 30%	97910
Transparency	Day	52% 6% 11% 20% 10% 1	105171
	Night	53% 6% 11% 19% 10% 1	102392
Seeing	Day	27% 16% 26% 17% 10% 4	14740
	Night	25% 15% 24% 24% 11% 1	24190

By Month

Percentage Cloud Cover NE (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	16% 22% 11% 10% 5% 3 3 2 3 4 20%	2517
	11th to 20th	Day	11% 19% 10% 18% 6% 4 4 3 3 4 18%	2812
	21st to end	Day	23% 19% 9% 12% 5% 4 3 2 3 4 15%	3124
February	1st to 10th	Day	16% 17% 5% 13% 8% 6% 4 3 4 4 20%	1710
	11th to 20th	Day	14% 14% 8% 12% 6% 4 5% 4 4 6% 23%	1663
	21st to end	Day	21% 14% 3 11% 5% 3 3 2 4 5% 28%	1521
March	1st to 10th	Day	21% 12% 5% 9% 4 3 3 3 5% 6% 29%	3427
	11th to 20th	Day	12% 16% 6% 10% 5% 5% 3 2 3 5% 32%	3480
	21st to end	Day	15% 11% 3 11% 6% 5% 5% 3 4 5% 31%	3829
April	1st to 10th	Day	18% 15% 3 8% 4 4 4 3 4 6% 30%	2280
	11th to 20th	Day	18% 12% 3 8% 4 3 4 4 5% 6% 32%	2254
	21st to end	Day	21% 9% 3 8% 5% 5% 4 4 4 5% 34%	2400
May	1st to 10th	Day	27% 8% 2 7% 4 4 4 4 4 6% 29%	4108
	11th to 20th	Day	23% 10% 3 8% 5% 5% 4 4 6% 7% 25%	4352
	21st to end	Day	13% 7% 2 6% 4 5% 5% 4 6% 8% 39%	4837
June	1st to 10th	Day	16% 8% 3 8% 6% 5% 4 4 6% 8% 33%	2660
	11th to 20th	Day	14% 7% 3 7% 5% 6% 5% 4 6% 8% 33%	2660
	21st to end	Day	14% 6% 2 7% 5% 5% 6% 4 7% 9% 36%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 5% 4 6% 10% 37%	4440
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 5% 7% 8% 36%	4418
	21st to end	Day	10% 7% 3 7% 5% 6% 6% 4 6% 9% 37%	4466
August	1st to 10th	Day	20% 8% 3 7% 4 5% 5% 4 6% 8% 29%	4104
	11th to 20th	Day	15% 7% 3 8% 6% 6% 6% 5% 7% 9% 29%	4044
	21st to end	Day	15% 6% 2 6% 4 5% 6% 4 6% 10% 36%	4190
September	1st to 10th	Day	19% 7% 2 6% 4 5% 4 3 4 7% 39%	2280
	11th to 20th	Day	14% 7% 2 6% 4 3 4 3 5% 7% 43%	2242
	21st to end	Day	24% 7% 2 7% 4 4 4 3 4 7% 33%	2005
October	1st to 10th	Day	18% 8% 3 8% 4 4 4 4 5% 8% 34%	1900
	11th to 20th	Day	19% 10% 3 7% 5% 4 3 4 6% 6% 33%	1900
	21st to end	Day	22% 12% 3 7% 5% 4 4 4 5% 7% 28%	2090
November	1st to 10th	Day	14% 10% 3 6% 4 5% 4 4 5% 7% 38%	1837
	11th to 20th	Day	18% 15% 5% 10% 5% 4 4 3 5% 5% 26%	1605
	21st to end	Day	20% 18% 5% 8% 6% 5% 3 4 4 6% 22%	1552
December	1st to 10th	Day	19% 21% 8% 10% 6% 5% 5% 3 4 4 16%	1520
	11th to 20th	Day	19% 18% 6% 11% 4 4 5% 3 6% 6% 19%	1906
	21st to end	Day	25% 20% 7% 11% 5% 3 3 3 4 4 14%	2772
January	1st to 10th	Night	17% 19% 8% 12% 6% 5% 4 3 4 5% 17%	4429
	11th to 20th	Night	15% 18% 8% 16% 7% 5% 4 3 5% 5% 15%	4144
	21st to end	Night	24% 18% 7% 15% 5% 4 3 2 3 3 15%	4532
February	1st to 10th	Night	15% 17% 5% 11% 6% 5% 5% 4 5% 5% 23%	2470
	11th to 20th	Night	16% 12% 6% 12% 7% 5% 6% 4 5% 6% 22%	2403
	21st to end	Night	18% 13% 4 13% 6% 4 4 4 5% 5% 25%	1932
March	1st to 10th	Night	21% 14% 3 9% 5% 4 4 3 4 4 28%	3408
	11th to 20th	Night	15% 17% 7% 9% 4 3 4 3 5% 6% 26%	3479
	21st to end	Night	16% 10% 3 8% 4 4 3 3 4 5% 39%	3802
April	1st to 10th	Night	19% 13% 4 8% 5% 4 4 3 5% 5% 30%	1900
	11th to 20th	Night	18% 10% 2 7% 4 4 4 4 5% 6% 35%	1875
	21st to end	Night	16% 10% 4 7% 4 4 4 4 5% 7% 35%	1796
May	1st to 10th	Night	27% 10% 3 7% 4 4 3 3 4 5% 31%	2833
	11th to 20th	Night	24% 10% 3 7% 5% 4 3 4 6% 7% 29%	2538
	21st to end	Night	13% 7% 3 6% 5% 4 5% 5% 7% 9% 37%	2738
June	1st to 10th	Night	13% 6% 2 7% 4 5% 4 4 7% 8% 40%	1520
	11th to 20th	Night	11% 5% 2 7% 5% 4 6% 5% 6% 9% 40%	1520
	21st to end	Night	14% 5% 2 7% 4 4 4 3 7% 8% 41%	1520
July	1st to 10th	Night	12% 8% 3 7% 5% 5% 5% 4 6% 7% 39%	2520
	11th to 20th	Night	11% 6% 3 6% 4 4 4 4 7% 9% 43%	2538
	21st to end	Night	13% 6% 2 6% 5% 4 4 4 6% 7% 42%	3087
August	1st to 10th	Night	19% 6% 3 7% 5% 4 4 4 6% 7% 36%	2825
	11th to 20th	Night	18% 6% 2 6% 4 4 5% 3 5% 7% 39%	2785
	21st to end	Night	13% 5% 2 5% 4 3 5% 4 6% 8% 45%	3433
September	1st to 10th	Night	16% 6% 2 6% 5% 3 3 3 4 7% 45%	1900
	11th to 20th	Night	13% 6% 2 6% 3 3 3 4 5% 6% 48%	1933
	21st to end	Night	20% 9% 3 6% 5% 4 4 3 5% 6% 35%	2175
October	1st to 10th	Night	18% 7% 2 5% 4 3 4 3 5% 7% 41%	2280
	11th to 20th	Night	20% 10% 2 5% 4 4 4 4 5% 6% 35%	2280
	21st to end	Night	22% 11% 2 6% 4 4 4 4 5% 7% 30%	2508
November	1st to 10th	Night	12% 10% 2 6% 4 4 4 4 5% 7% 41%	2459
	11th to 20th	Night	17% 15% 3 9% 6% 4 4 4 6% 6% 27%	2793
	21st to end	Night	17% 17% 5% 9% 5% 5% 5% 3 5% 6% 23%	2723
December	1st to 10th	Night	21% 17% 7% 9% 6% 4 5% 3 6% 6% 17%	2660
	11th to 20th	Night	18% 16% 5% 12% 6% 5% 5% 3 4 5% 22%	3288
	21st to end	Night	25% 18% 7% 10% 5% 4 4 3 5% 5% 14%	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	69% 4 9% 12% 4 1	2518
	11th to 20th	Day	71% 4 8% 12% 5%	2812
	21st to end	Day	76% 4 6% 9% 4 1	3124
February	1st to 10th	Day	68% 5% 9% 12% 6%	1710
	11th to 20th	Day	63% 4 9% 17% 7%	1672
	21st to end	Day	61% 3 9% 18% 7% 2	1521
March	1st to 10th	Day	56% 4 10% 23% 6%	3430
	11th to 20th	Day	55% 4 15% 17% 7% 2	3480
	21st to end	Day	54% 4 10% 19% 11% 2	3829
April	1st to 10th	Day	55% 4 9% 18% 12% 1	2280
	11th to 20th	Day	52% 5% 11% 17% 13% 2	2254
	21st to end	Day	53% 5% 8% 19% 13% 2	2400
May	1st to 10th	Day	55% 6% 8% 22% 8% 1	4120
	11th to 20th	Day	56% 8% 10% 19% 7% 1	4356
	21st to end	Day	40% 7% 13% 25% 14% 1	4837
June	1st to 10th	Day	47% 8% 11% 19% 13% 1	2660
	11th to 20th	Day	47% 8% 14% 19% 12% 1	2660
	21st to end	Day	42% 8% 14% 24% 11% 1	2660
July	1st to 10th	Day	42% 7% 13% 24% 12% 1	4370
	11th to 20th	Day	42% 8% 13% 23% 14%	4343
	21st to end	Day	42% 7% 13% 25% 12% 1	4324
August	1st to 10th	Day	51% 8% 12% 20% 9%	4091
	11th to 20th	Day	48% 8% 15% 22% 7%	4083
	21st to end	Day	42% 7% 13% 27% 10% 1	4190
September	1st to 10th	Day	46% 4 10% 22% 16% 2	2280
	11th to 20th	Day	40% 6% 11% 24% 18% 1	2242
	21st to end	Day	52% 5% 11% 19% 14%	2005
October	1st to 10th	Day	44% 5% 12% 21% 17% 1	3160
	11th to 20th	Day	45% 4 14% 19% 16% 3	3140
	21st to end	Day	41% 5% 15% 26% 12% 1	3428
November	1st to 10th	Day	46% 5% 12% 20% 14% 3	1837
	11th to 20th	Day	60% 4 10% 17% 7% 2	1605
	21st to end	Day	64% 5% 10% 14% 6% 1	1552
December	1st to 10th	Day	73% 5% 9% 10% 3	1520
	11th to 20th	Day	66% 5% 11% 13% 4	1906
	21st to end	Day	74% 5% 10% 10% 2	2772
January	1st to 10th	Night	69% 4 9% 13% 5%	4429
	11th to 20th	Night	72% 5% 10% 10% 3 1	4144
	21st to end	Night	76% 3 6% 10% 4 1	4532
February	1st to 10th	Night	63% 5% 10% 15% 7%	2470
	11th to 20th	Night	62% 5% 11% 15% 7%	2405
	21st to end	Night	61% 4 10% 15% 9% 1	1932
March	1st to 10th	Night	60% 5% 9% 20% 6% 1	3418
	11th to 20th	Night	57% 6% 13% 16% 7% 1	3480
	21st to end	Night	47% 4 9% 21% 16% 3	3802
April	1st to 10th	Night	57% 5% 9% 17% 12% 1	1900
	11th to 20th	Night	49% 6% 11% 19% 12% 2	1875
	21st to end	Night	48% 5% 11% 20% 14% 2	1796
May	1st to 10th	Night	56% 5% 10% 19% 8% 2	2840
	11th to 20th	Night	52% 9% 12% 18% 8% 1	2539
	21st to end	Night	40% 9% 14% 19% 13% 5%	2739
June	1st to 10th	Night	40% 8% 13% 23% 15% 1	1520
	11th to 20th	Night	39% 10% 13% 24% 13% 2	1520
	21st to end	Night	40% 7% 12% 26% 13% 1	1520
July	1st to 10th	Night	44% 6% 11% 20% 17% 1	2480
	11th to 20th	Night	36% 8% 15% 24% 15% 1	2490
	21st to end	Night	39% 7% 12% 23% 18% 1	2988
August	1st to 10th	Night	46% 8% 13% 24% 8% 1	2814
	11th to 20th	Night	43% 7% 13% 28% 9%	2812
	21st to end	Night	36% 7% 14% 31% 10% 2	3433
September	1st to 10th	Night	40% 6% 10% 25% 16% 3	1900
	11th to 20th	Night	35% 6% 13% 27% 19% 2	1933
	21st to end	Night	49% 5% 12% 20% 13% 1	2175
October	1st to 10th	Night	43% 5% 11% 22% 18% 1	3800
	11th to 20th	Night	41% 5% 13% 20% 16% 4	3779
	21st to end	Night	40% 4 16% 25% 14% 1	4120
November	1st to 10th	Night	42% 6% 12% 22% 15% 2	2459
	11th to 20th	Night	57% 6% 11% 16% 8% 2	2793
	21st to end	Night	61% 6% 11% 17% 5% 1	2723
December	1st to 10th	Night	68% 6% 10% 12% 4	2660
	11th to 20th	Night	67% 5% 10% 15% 3	3288
	21st to end	Night	71% 5% 10% 11% 2	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	34% 25% 28% 6% 6% 1	180
	11th to 20th	Day	41% 25% 25% 7% 2	263
	21st to end	Day	34% 24% 31% 9% 1	297
February	1st to 10th	Day	37% 28% 26% 9% 1	270
	11th to 20th	Day	40% 28% 27% 4	270
	21st to end	Day	44% 20% 26% 9% 1	333
March	1st to 10th	Day	34% 23% 25% 13% 5%	460
	11th to 20th	Day	32% 25% 26% 12% 3 1	460
	21st to end	Day	36% 21% 25% 12% 4 1	506
April	1st to 10th	Day	33% 22% 25% 14% 4 2	460
	11th to 20th	Day	31% 22% 23% 13% 7% 4	452
	21st to end	Day	31% 20% 28% 13% 7% 1	460
May	1st to 10th	Day	32% 17% 26% 11% 9% 4	463
	11th to 20th	Day	27% 16% 31% 14% 8% 4	487
	21st to end	Day	19% 13% 30% 18% 13% 7%	529
June	1st to 10th	Day	22% 15% 29% 21% 11% 2	490
	11th to 20th	Day	20% 13% 27% 23% 13% 4	490
	21st to end	Day	20% 14% 30% 23% 10% 3	490
July	1st to 10th	Day	14% 10% 28% 24% 18% 7%	485
	11th to 20th	Day	11% 10% 30% 24% 18% 8%	484
	21st to end	Day	15% 10% 30% 23% 16% 5%	532
August	1st to 10th	Day	14% 9% 25% 27% 17% 8%	486
	11th to 20th	Day	16% 8% 29% 23% 15% 9%	479
	21st to end	Day	16% 8% 28% 23% 16% 9%	539
September	1st to 10th	Day	24% 12% 17% 22% 16% 9%	490
	11th to 20th	Day	15% 6% 22% 25% 21% 11%	490
	21st to end	Day	31% 11% 19% 20% 13% 4	490
October	1st to 10th	Day	22% 13% 23% 21% 17% 4	490
	11th to 20th	Day	29% 17% 27% 17% 9% 2	490
	21st to end	Day	33% 19% 24% 16% 7% 1	539
November	1st to 10th	Day	25% 19% 24% 17% 14% 1	435
	11th to 20th	Day	36% 25% 22% 12% 5%	205
	21st to end	Day	35% 23% 32% 7% 3	188
December	1st to 10th	Day	42% 23% 22% 9% 2 2	180
	11th to 20th	Day	45% 17% 27% 8% 2	180
	21st to end	Day	41% 20% 30% 6% 3	198
January	1st to 10th	Night	34% 23% 27% 13% 3	760
	11th to 20th	Night	32% 23% 25% 17% 3	760
	21st to end	Night	31% 23% 28% 16% 2	836
February	1st to 10th	Night	33% 19% 29% 18% 2	760
	11th to 20th	Night	32% 26% 29% 11% 1	743
	21st to end	Night	35% 20% 26% 17% 2	628
March	1st to 10th	Night	29% 20% 29% 19% 3	760
	11th to 20th	Night	31% 22% 23% 19% 5% 1	760
	21st to end	Night	25% 21% 30% 17% 6%	836
April	1st to 10th	Night	29% 19% 27% 21% 4	760
	11th to 20th	Night	27% 16% 27% 21% 8% 1	751
	21st to end	Night	24% 13% 27% 30% 7%	656
May	1st to 10th	Night	25% 11% 19% 30% 15% 1	570
	11th to 20th	Night	19% 12% 24% 37% 8%	404
	21st to end	Night	15% 7% 21% 31% 24% 1	411
June	1st to 10th	Night	14% 6% 25% 38% 16% 1	380
	11th to 20th	Night	13% 11% 18% 38% 20%	380
	21st to end	Night	13% 5% 25% 38% 18% 1	380
July	1st to 10th	Night	14% 3 21% 36% 23% 3	370
	11th to 20th	Night	9% 3 18% 41% 28% 1	373
	21st to end	Night	13% 4 17% 40% 24% 2	624
August	1st to 10th	Night	10% 3 16% 39% 29% 2	567
	11th to 20th	Night	16% 5% 13% 34% 28% 4	564
	21st to end	Night	13% 4 18% 32% 29% 3	806
September	1st to 10th	Night	19% 7% 18% 29% 23% 4	760
	11th to 20th	Night	15% 5% 18% 27% 29% 5%	760
	21st to end	Night	23% 11% 19% 25% 19% 4	760
October	1st to 10th	Night	21% 9% 22% 25% 20% 2	760
	11th to 20th	Night	28% 13% 23% 24% 10% 1	760
	21st to end	Night	31% 12% 25% 24% 6%	836
November	1st to 10th	Night	21% 15% 26% 28% 10%	780
	11th to 20th	Night	30% 17% 25% 21% 6% 1	800
	21st to end	Night	31% 17% 28% 19% 5% 1	779
December	1st to 10th	Night	34% 24% 24% 14% 4	760
	11th to 20th	Night	30% 22% 26% 18% 4	760
	21st to end	Night	33% 21% 25% 19% 2	836

Page generated at 2024-11-22 08:02:25. Version ac07

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