Hebron
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hebron clear sky chart from 2005-11-06 to 2025-04-11.

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	14% 9% 3 7% 5% 4 4 4 5% 7% 37%	113753
	Night	15% 10% 4 8% 4 4 4 3 5% 6% 37%	114565
Transparency	Day	27% 42% 6% 15% 9% 1	117435
	Night	29% 40% 6% 15% 10% 1	119022
Seeing	Day	18% 12% 27% 23% 14% 6%	15844
	Night	19% 9% 26% 29% 15% 2	25681

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	15% 17% 8% 11% 4 3 3 3 4 5% 27%	3617
	11th to 20th	Day	13% 13% 6% 13% 5% 6% 4 3 3 4 29%	3901
	21st to end	Day	21% 12% 6% 8% 5% 5% 5% 3 4 4 26%	4466
February	1st to 10th	Day	18% 14% 5% 8% 4 4 4 4 4 5% 31%	1928
	11th to 20th	Day	16% 12% 5% 11% 5% 4 4 3 4 5% 32%	1948
	21st to end	Day	18% 13% 5% 9% 4 3 4 3 4 5% 32%	1650
March	1st to 10th	Day	18% 13% 5% 8% 4 3 4 3 4 4 32%	4480
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 5% 8% 40%	4980
	21st to end	Day	17% 10% 3 7% 4 4 4 4 6% 6% 34%	5465
April	1st to 10th	Day	16% 9% 3 7% 4 5% 5% 4 5% 8% 34%	2379
	11th to 20th	Day	16% 8% 2 8% 5% 4 4 3 5% 7% 39%	2290
	21st to end	Day	18% 8% 3 7% 5% 5% 4 3 5% 7% 36%	2470
May	1st to 10th	Day	21% 9% 2 7% 5% 5% 5% 3 5% 8% 29%	4082
	11th to 20th	Day	20% 8% 3 6% 4 3 4 3 5% 7% 37%	4081
	21st to end	Day	10% 6% 3 8% 5% 6% 6% 5% 8% 9% 34%	4476
June	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 8% 40%	2483
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 7% 8% 44%	2660
	21st to end	Day	8% 6% 2 7% 6% 5% 5% 5% 6% 9% 41%	2660
July	1st to 10th	Day	13% 6% 2 7% 5% 4 5% 4 6% 10% 38%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 11% 47%	4313
	21st to end	Day	11% 7% 3 8% 6% 7% 7% 6% 7% 8% 30%	4466
August	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 45%	4104
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 4 7% 10% 41%	4024
	21st to end	Day	6% 4 1 5% 4 4 4 4 5% 8% 55%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 4 4 4 5% 7% 47%	2174
	11th to 20th	Day	8% 5% 2 7% 4 3 5% 4 6% 9% 48%	2090
	21st to end	Day	16% 6% 2 5% 4 4 4 2 4 6% 48%	2090
October	1st to 10th	Day	10% 5% 2 7% 5% 4 4 3 4 5% 51%	2090
	11th to 20th	Day	12% 6% 2 6% 5% 4 3 3 6% 7% 46%	1945
	21st to end	Day	19% 8% 3 7% 4 4 3 3 5% 6% 39%	1932
November	1st to 10th	Day	9% 7% 3 6% 4 3 4 2 4 6% 52%	1762
	11th to 20th	Day	14% 11% 3 8% 5% 3 4 3 5% 7% 36%	1800
	21st to end	Day	17% 11% 3 8% 5% 3 3 3 4 6% 37%	1800
December	1st to 10th	Day	18% 11% 4 7% 4 3 3 3 3 5% 40%	2930
	11th to 20th	Day	17% 14% 5% 10% 5% 5% 4 3 4 5% 27%	3373
	21st to end	Day	23% 18% 5% 9% 6% 4 4 3 4 6% 19%	4224
January	1st to 10th	Night	15% 16% 7% 13% 6% 5% 5% 4 4 5% 20%	6348
	11th to 20th	Night	13% 16% 7% 14% 6% 5% 5% 3 4 4 23%	6058
	21st to end	Night	20% 13% 5% 7% 4 4 3 3 4 5% 32%	6490
February	1st to 10th	Night	20% 12% 4 10% 6% 3 4 3 5% 5% 28%	2470
	11th to 20th	Night	17% 11% 3 9% 5% 5% 3 3 5% 6% 30%	2338
	21st to end	Night	21% 13% 4 8% 4 3 4 3 4 6% 31%	1980
March	1st to 10th	Night	19% 13% 3 6% 4 3 4 3 4 5% 37%	5359
	11th to 20th	Night	12% 7% 2 6% 4 4 4 4 6% 7% 44%	4980
	21st to end	Night	17% 9% 3 9% 5% 4 5% 3 5% 6% 34%	5467
April	1st to 10th	Night	15% 9% 2 7% 4 4 4 4 6% 7% 37%	2038
	11th to 20th	Night	14% 8% 3 6% 5% 4 4 4 6% 7% 40%	1844
	21st to end	Night	17% 7% 3 6% 4 4 4 4 6% 8% 37%	1710
May	1st to 10th	Night	21% 11% 4 9% 5% 4 4 4 5% 7% 27%	2813
	11th to 20th	Night	19% 6% 2 6% 3 4 4 4 6% 8% 38%	2812
	21st to end	Night	8% 7% 2 6% 4 5% 5% 4 6% 9% 46%	3079
June	1st to 10th	Night	8% 6% 2 6% 4 5% 3 4 6% 9% 48%	1690
	11th to 20th	Night	7% 5% 2 6% 4 4 4 3 6% 12% 47%	1520
	21st to end	Night	6% 4 2 5% 5% 4 5% 5% 8% 9% 48%	1520
July	1st to 10th	Night	10% 6% 2 5% 4 4 4 3 6% 8% 48%	2530
	11th to 20th	Night	5% 4 2 5% 4 4 4 3 7% 9% 52%	2649
	21st to end	Night	10% 8% 2 7% 5% 6% 5% 5% 7% 9% 37%	3087
August	1st to 10th	Night	7% 5% 2 6% 4 4 5% 4 6% 10% 45%	2825
	11th to 20th	Night	7% 6% 3 6% 5% 4 5% 4 6% 8% 46%	2802
	21st to end	Night	3 2 1 4 3 3 4 4 6% 10% 60%	3476
September	1st to 10th	Night	13% 5% 2 4 3 3 4 3 5% 7% 52%	1985
	11th to 20th	Night	8% 4 2 4 3 3 4 4 4 8% 54%	2090
	21st to end	Night	15% 6% 2 5% 4 3 3 2 5% 5% 49%	2090
October	1st to 10th	Night	8% 4 2 6% 3 3 4 3 5% 6% 56%	2090
	11th to 20th	Night	14% 6% 2 6% 4 3 4 3 6% 6% 46%	2233
	21st to end	Night	18% 8% 3 6% 3 3 4 3 5% 6% 41%	2664
November	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 5% 47%	2536
	11th to 20th	Night	15% 9% 3 7% 4 4 4 4 4 7% 40%	2600
	21st to end	Night	18% 12% 3 7% 5% 4 4 3 5% 6% 34%	2600
December	1st to 10th	Night	17% 10% 4 8% 4 4 4 3 4 4 38%	4250
	11th to 20th	Night	19% 14% 6% 10% 5% 4 4 3 5% 5% 27%	4822
	21st to end	Night	22% 19% 6% 11% 5% 5% 3 3 4 5% 17%	6720

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	47% 27% 6% 15% 5%	3618
	11th to 20th	Day	44% 27% 5% 13% 10% 2	3901
	21st to end	Day	46% 28% 5% 13% 6% 2	4466
February	1st to 10th	Day	22% 62% 4 7% 5%	1928
	11th to 20th	Day	21% 61% 3 8% 6%	1958
	21st to end	Day	19% 62% 4 9% 5% 1	1650
March	1st to 10th	Day	43% 28% 3 12% 11% 3	4480
	11th to 20th	Day	28% 29% 6% 24% 13% 1	4980
	21st to end	Day	34% 29% 9% 15% 11% 1	5465
April	1st to 10th	Day	22% 62% 4 8% 4	2379
	11th to 20th	Day	16% 65% 3 10% 4 1	2290
	21st to end	Day	17% 65% 5% 8% 5% 1	2470
May	1st to 10th	Day	34% 41% 8% 12% 5%	4120
	11th to 20th	Day	28% 40% 8% 17% 7%	4085
	21st to end	Day	28% 42% 6% 12% 11% 1	4489
June	1st to 10th	Day	16% 65% 4 8% 6% 1	2483
	11th to 20th	Day	15% 66% 3 8% 7%	2660
	21st to end	Day	15% 65% 6% 7% 6% 1	2660
July	1st to 10th	Day	28% 37% 8% 14% 12% 1	4371
	11th to 20th	Day	18% 38% 7% 24% 13%	4238
	21st to end	Day	33% 38% 8% 10% 9% 2	4324
August	1st to 10th	Day	21% 39% 11% 23% 6%	4091
	11th to 20th	Day	22% 38% 7% 23% 9%	4063
	21st to end	Day	15% 38% 10% 22% 14% 1	4179
September	1st to 10th	Day	13% 60% 5% 11% 9% 2	2174
	11th to 20th	Day	13% 60% 6% 11% 8% 1	2090
	21st to end	Day	16% 59% 5% 12% 8%	2090
October	1st to 10th	Day	11% 37% 4 25% 21% 1	3480
	11th to 20th	Day	16% 37% 5% 20% 21% 1	3211
	21st to end	Day	19% 36% 6% 18% 19% 1	3156
November	1st to 10th	Day	20% 56% 5% 13% 6% 1	1762
	11th to 20th	Day	20% 57% 3 10% 10% 1	1800
	21st to end	Day	24% 57% 5% 10% 4	1800
December	1st to 10th	Day	29% 35% 5% 20% 10%	2930
	11th to 20th	Day	43% 33% 4 15% 6%	3370
	21st to end	Day	54% 26% 7% 9% 4	4224
January	1st to 10th	Night	51% 26% 5% 9% 7%	6348
	11th to 20th	Night	52% 26% 5% 8% 6% 3	6058
	21st to end	Night	41% 27% 5% 18% 8% 1	6490
February	1st to 10th	Night	22% 62% 4 8% 4	2470
	11th to 20th	Night	22% 61% 3 7% 5%	2339
	21st to end	Night	20% 61% 3 7% 7% 1	1980
March	1st to 10th	Night	39% 29% 3 21% 7% 2	5359
	11th to 20th	Night	25% 29% 7% 23% 15% 1	4980
	21st to end	Night	38% 28% 4 19% 9% 1	5467
April	1st to 10th	Night	22% 62% 4 8% 4	2038
	11th to 20th	Night	16% 65% 3 8% 7% 1	1844
	21st to end	Night	16% 65% 5% 9% 5% 1	1710
May	1st to 10th	Night	37% 41% 6% 12% 4 1	2840
	11th to 20th	Night	26% 41% 9% 21% 3	2813
	21st to end	Night	20% 41% 8% 20% 9% 2	3087
June	1st to 10th	Night	13% 65% 3 11% 8% 1	1690
	11th to 20th	Night	12% 66% 4 8% 8% 2	1520
	21st to end	Night	12% 65% 7% 9% 6% 1	1520
July	1st to 10th	Night	22% 39% 6% 18% 12% 4	2490
	11th to 20th	Night	17% 37% 8% 24% 13%	2601
	21st to end	Night	30% 37% 9% 13% 8% 4	2988
August	1st to 10th	Night	24% 40% 9% 22% 5%	2814
	11th to 20th	Night	23% 39% 6% 21% 11%	2829
	21st to end	Night	12% 38% 10% 25% 15% 1	3476
September	1st to 10th	Night	12% 61% 5% 11% 9% 2	1985
	11th to 20th	Night	11% 60% 5% 12% 12% 1	2090
	21st to end	Night	15% 59% 5% 10% 10% 1	2090
October	1st to 10th	Night	12% 37% 3 18% 30% 1	3480
	11th to 20th	Night	13% 36% 7% 16% 27% 1	3706
	21st to end	Night	17% 37% 5% 16% 22% 3	4390
November	1st to 10th	Night	22% 56% 5% 10% 7% 1	2536
	11th to 20th	Night	19% 57% 3 10% 9% 2	2600
	21st to end	Night	25% 57% 5% 10% 3	2600
December	1st to 10th	Night	30% 35% 7% 18% 9%	4250
	11th to 20th	Night	42% 32% 7% 13% 6%	4824
	21st to end	Night	56% 26% 5% 10% 3	6720

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	25% 22% 32% 16% 5% 1	300
	11th to 20th	Day	28% 24% 34% 12% 3	300
	21st to end	Day	28% 22% 32% 14% 4	330
February	1st to 10th	Day	27% 23% 32% 15% 2	300
	11th to 20th	Day	30% 25% 31% 11% 2 1	300
	21st to end	Day	29% 18% 41% 10% 2	249
March	1st to 10th	Day	24% 30% 31% 14% 1	300
	11th to 20th	Day	26% 21% 31% 16% 5%	500
	21st to end	Day	31% 18% 29% 16% 5%	550
April	1st to 10th	Day	23% 20% 29% 18% 9% 1	500
	11th to 20th	Day	23% 20% 24% 20% 10% 4	452
	21st to end	Day	23% 18% 34% 15% 8% 3	460
May	1st to 10th	Day	24% 13% 33% 19% 8% 4	463
	11th to 20th	Day	22% 11% 26% 24% 11% 5%	487
	21st to end	Day	13% 8% 28% 27% 16% 9%	529
June	1st to 10th	Day	14% 7% 23% 30% 19% 7%	503
	11th to 20th	Day	12% 6% 24% 33% 18% 6%	680
	21st to end	Day	10% 6% 29% 30% 17% 8%	680
July	1st to 10th	Day	13% 4 19% 27% 21% 16%	671
	11th to 20th	Day	9% 4 25% 28% 22% 12%	593
	21st to end	Day	13% 3 17% 32% 22% 13%	532
August	1st to 10th	Day	10% 4 16% 28% 25% 16%	486
	11th to 20th	Day	11% 4 20% 33% 18% 14%	479
	21st to end	Day	8% 4 15% 29% 29% 15%	539
September	1st to 10th	Day	11% 4 17% 28% 30% 10%	490
	11th to 20th	Day	9% 4 15% 27% 30% 15%	490
	21st to end	Day	20% 8% 20% 22% 22% 7%	490
October	1st to 10th	Day	10% 7% 23% 32% 21% 8%	490
	11th to 20th	Day	16% 13% 31% 22% 14% 3	490
	21st to end	Day	22% 13% 38% 20% 6% 1	381
November	1st to 10th	Day	12% 17% 37% 21% 9% 3	300
	11th to 20th	Day	22% 21% 28% 21% 6% 2	300
	21st to end	Day	25% 17% 38% 16% 4	300
December	1st to 10th	Day	21% 22% 38% 13% 6%	300
	11th to 20th	Day	21% 20% 39% 14% 6%	300
	21st to end	Day	32% 18% 32% 14% 4	330
January	1st to 10th	Night	23% 17% 32% 23% 6%	1000
	11th to 20th	Night	28% 16% 33% 20% 3	867
	21st to end	Night	26% 15% 34% 23% 3	880
February	1st to 10th	Night	27% 13% 34% 24% 2	800
	11th to 20th	Night	25% 16% 34% 22% 2	783
	21st to end	Night	29% 14% 31% 24% 2	660
March	1st to 10th	Night	23% 13% 33% 25% 5%	800
	11th to 20th	Night	24% 14% 34% 22% 6% 1	800
	21st to end	Night	24% 13% 30% 27% 6%	880
April	1st to 10th	Night	20% 12% 34% 26% 8%	638
	11th to 20th	Night	20% 10% 32% 27% 10% 1	565
	21st to end	Night	19% 8% 38% 25% 9% 1	570
May	1st to 10th	Night	21% 8% 31% 27% 13%	570
	11th to 20th	Night	18% 6% 24% 34% 16% 2	561
	21st to end	Night	10% 3 23% 35% 26% 4	617
June	1st to 10th	Night	11% 3 19% 43% 22% 2	570
	11th to 20th	Night	9% 4 17% 41% 24% 4	570
	21st to end	Night	7% 2 23% 39% 26% 3	570
July	1st to 10th	Night	12% 3 12% 32% 31% 8%	555
	11th to 20th	Night	9% 3 14% 37% 34% 4	552
	21st to end	Night	12% 2 12% 40% 30% 4	624
August	1st to 10th	Night	10% 1 12% 36% 38% 3	567
	11th to 20th	Night	8% 1 16% 41% 29% 5%	564
	21st to end	Night	6% 13% 32% 41% 7%	627
September	1st to 10th	Night	14% 3 15% 32% 33% 4	655
	11th to 20th	Night	10% 3 14% 33% 35% 5%	760
	21st to end	Night	17% 5% 21% 32% 23% 3	760
October	1st to 10th	Night	11% 4 22% 36% 23% 5%	760
	11th to 20th	Night	18% 10% 25% 31% 15% 2	760
	21st to end	Night	22% 9% 32% 25% 11% 1	836
November	1st to 10th	Night	17% 9% 28% 28% 16% 1	780
	11th to 20th	Night	21% 14% 28% 26% 10% 1	800
	21st to end	Night	25% 10% 28% 28% 8% 1	800
December	1st to 10th	Night	26% 11% 34% 23% 6%	800
	11th to 20th	Night	24% 11% 33% 24% 6% 1	800
	21st to end	Night	30% 15% 29% 23% 3	980

Page generated at 2025-04-08 09:17:23. Version ac07

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