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 2026-08-15.

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 8% 5% 5% 5% 4 5% 7% 36%	143574
	Night	14% 10% 3 8% 5% 4 4 3 5% 7% 37%	138385
Transparency	Day	31% 34% 7% 17% 10% 1	147212
	Night	32% 34% 7% 16% 10% 1	142819
Seeing	Day	18% 13% 27% 22% 14% 6%	17743
	Night	19% 9% 26% 29% 15% 2	27379

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	16% 16% 7% 10% 5% 4 4 3 4 6% 26%	4691
	11th to 20th	Day	12% 12% 5% 15% 6% 5% 4 2 3 5% 30%	5082
	21st to end	Day	19% 12% 6% 10% 7% 6% 5% 4 5% 5% 23%	5780
February	1st to 10th	Day	18% 14% 5% 8% 4 4 4 4 4 5% 32%	2025
	11th to 20th	Day	16% 12% 5% 11% 4 4 4 3 4 5% 32%	2048
	21st to end	Day	17% 12% 5% 9% 4 3 4 3 4 5% 32%	1730
March	1st to 10th	Day	19% 13% 5% 8% 4 3 4 3 4 4 32%	4580
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 6% 8% 39%	5090
	21st to end	Day	17% 10% 3 7% 4 4 4 4 6% 6% 34%	5586
April	1st to 10th	Day	16% 9% 3 7% 4 5% 5% 4 5% 8% 35%	2498
	11th to 20th	Day	15% 8% 3 8% 5% 4 4 3 5% 7% 39%	2534
	21st to end	Day	17% 8% 3 7% 5% 5% 4 3 5% 7% 36%	2730
May	1st to 10th	Day	18% 8% 3 8% 6% 5% 5% 4 6% 8% 29%	7616
	11th to 20th	Day	17% 8% 3 7% 4 4 4 3 5% 7% 37%	7626
	21st to end	Day	16% 8% 3 8% 5% 6% 6% 5% 7% 8% 27%	8391
June	1st to 10th	Day	13% 5% 2 6% 5% 5% 5% 4 6% 8% 41%	2745
	11th to 20th	Day	9% 5% 2 6% 5% 6% 5% 5% 7% 8% 42%	2940
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 6% 10% 40%	2940
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 10% 40%	8280
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 4 7% 11% 39%	8041
	21st to end	Day	9% 6% 3 8% 6% 7% 7% 6% 7% 9% 33%	8340
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 44%	4364
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 4 7% 10% 41%	4205
	21st to end	Day	6% 4 1 5% 4 4 4 4 5% 8% 55%	4312
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 5% 6% 48%	2288
	11th to 20th	Day	8% 5% 2 6% 4 3 5% 4 6% 9% 49%	2200
	21st to end	Day	16% 6% 2 5% 4 4 4 2 4 7% 47%	2200
October	1st to 10th	Day	10% 5% 2 7% 4 4 4 3 4 4 52%	2200
	11th to 20th	Day	12% 6% 2 6% 4 4 3 4 6% 7% 47%	2047
	21st to end	Day	19% 8% 3 7% 4 4 3 3 5% 6% 39%	2033
November	1st to 10th	Day	9% 7% 3 6% 4 3 4 2 4 6% 52%	1852
	11th to 20th	Day	14% 11% 4 8% 5% 3 4 3 5% 7% 36%	1890
	21st to end	Day	17% 11% 4 8% 5% 3 3 3 4 5% 36%	1890
December	1st to 10th	Day	17% 11% 4 7% 4 3 3 3 3 5% 39%	3020
	11th to 20th	Day	17% 14% 5% 10% 5% 5% 4 3 4 5% 27%	3463
	21st to end	Day	23% 18% 5% 9% 6% 4 4 3 4 6% 19%	4317
January	1st to 10th	Night	14% 15% 6% 13% 6% 5% 5% 4 4 5% 23%	8232
	11th to 20th	Night	11% 15% 7% 15% 6% 5% 5% 3 4 4 25%	7880
	21st to end	Night	17% 12% 4 9% 5% 4 3 3 4 5% 32%	8401
February	1st to 10th	Night	19% 12% 4 10% 6% 4 4 3 5% 5% 28%	2593
	11th to 20th	Night	17% 11% 3 9% 5% 5% 3 3 5% 6% 31%	2458
	21st to end	Night	20% 13% 4 8% 4 3 4 3 4 6% 31%	2076
March	1st to 10th	Night	20% 13% 3 6% 4 3 4 3 4 5% 36%	5479
	11th to 20th	Night	12% 7% 2 7% 4 4 4 4 6% 7% 43%	5090
	21st to end	Night	16% 9% 3 9% 5% 4 5% 3 5% 6% 34%	5588
April	1st to 10th	Night	14% 9% 3 7% 4 4 4 4 6% 7% 37%	2140
	11th to 20th	Night	13% 8% 3 6% 5% 4 4 4 6% 7% 40%	2034
	21st to end	Night	16% 7% 3 6% 4 4 4 4 7% 8% 37%	1890
May	1st to 10th	Night	20% 8% 3 7% 4 4 5% 4 6% 8% 32%	5237
	11th to 20th	Night	15% 6% 3 7% 4 5% 5% 4 6% 8% 36%	5234
	21st to end	Night	15% 9% 3 9% 5% 5% 6% 4 5% 9% 32%	5761
June	1st to 10th	Night	8% 6% 2 6% 4 4 3 4 6% 9% 48%	1868
	11th to 20th	Night	8% 6% 2 6% 4 4 4 4 6% 11% 45%	1680
	21st to end	Night	7% 5% 2 5% 5% 4 5% 5% 8% 9% 47%	1680
July	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 4 6% 9% 46%	4708
	11th to 20th	Night	9% 6% 2 7% 5% 4 5% 3 7% 8% 43%	4930
	21st to end	Night	8% 6% 2 6% 5% 6% 5% 5% 7% 10% 39%	5736
August	1st to 10th	Night	7% 5% 2 6% 4 4 5% 4 6% 10% 45%	3005
	11th to 20th	Night	7% 6% 3 6% 5% 4 5% 4 6% 8% 46%	2928
	21st to end	Night	4 2 1 4 3 3 4 4 6% 9% 60%	3586
September	1st to 10th	Night	12% 5% 2 4 3 3 4 3 5% 7% 53%	2090
	11th to 20th	Night	8% 4 2 4 3 3 4 4 4 8% 55%	2200
	21st to end	Night	16% 6% 2 5% 4 3 3 2 5% 5% 49%	2200
October	1st to 10th	Night	8% 4 2 5% 3 3 4 3 5% 6% 56%	2200
	11th to 20th	Night	14% 6% 2 6% 4 3 4 3 5% 6% 47%	2351
	21st to end	Night	18% 8% 2 6% 3 3 4 3 5% 5% 41%	2804
November	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 5% 47%	2666
	11th to 20th	Night	15% 9% 3 7% 4 4 3 4 5% 7% 40%	2730
	21st to end	Night	19% 12% 3 7% 5% 4 4 3 5% 6% 33%	2730
December	1st to 10th	Night	17% 10% 4 8% 4 4 4 3 4 4 38%	4380
	11th to 20th	Night	18% 14% 6% 10% 5% 4 4 3 4 5% 27%	4952
	21st to end	Night	22% 19% 6% 11% 5% 5% 3 3 4 5% 18%	6868

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	49% 22% 10% 15% 4	4692
	11th to 20th	Day	47% 21% 6% 14% 11% 1	5082
	21st to end	Day	51% 22% 6% 13% 5% 2	5780
February	1st to 10th	Day	23% 59% 4 8% 5%	2025
	11th to 20th	Day	23% 58% 4 9% 6%	2058
	21st to end	Day	20% 59% 4 10% 5% 1	1730
March	1st to 10th	Day	43% 28% 3 12% 11% 3	4580
	11th to 20th	Day	29% 28% 6% 23% 12% 1	5090
	21st to end	Day	34% 29% 9% 16% 11% 1	5586
April	1st to 10th	Day	22% 60% 5% 9% 4	2498
	11th to 20th	Day	20% 60% 4 11% 5% 1	2534
	21st to end	Day	19% 59% 5% 11% 5% 1	2730
May	1st to 10th	Day	41% 25% 10% 16% 9%	7651
	11th to 20th	Day	36% 23% 9% 21% 11%	7630
	21st to end	Day	43% 24% 7% 15% 9% 2	8405
June	1st to 10th	Day	18% 59% 4 9% 8% 1	2745
	11th to 20th	Day	18% 60% 4 9% 8% 1	2940
	21st to end	Day	18% 60% 7% 9% 7% 1	2940
July	1st to 10th	Day	31% 23% 10% 22% 13% 1	8211
	11th to 20th	Day	31% 24% 10% 25% 10%	7966
	21st to end	Day	37% 23% 9% 17% 12% 1	8156
August	1st to 10th	Day	21% 37% 11% 24% 6%	4351
	11th to 20th	Day	23% 37% 7% 24% 9%	4244
	21st to end	Day	15% 37% 10% 23% 14% 1	4311
September	1st to 10th	Day	13% 57% 5% 13% 10% 2	2288
	11th to 20th	Day	14% 58% 6% 13% 10% 1	2200
	21st to end	Day	17% 57% 5% 12% 9%	2200
October	1st to 10th	Day	12% 36% 4 25% 22% 1	3590
	11th to 20th	Day	16% 36% 5% 20% 21% 1	3313
	21st to end	Day	20% 35% 6% 18% 19% 1	3257
November	1st to 10th	Day	21% 53% 5% 14% 6% 1	1852
	11th to 20th	Day	21% 54% 3 11% 10% 1	1890
	21st to end	Day	26% 55% 5% 10% 4	1890
December	1st to 10th	Day	30% 35% 5% 20% 9%	3020
	11th to 20th	Day	43% 32% 4 15% 6% 1	3460
	21st to end	Day	54% 26% 7% 9% 4	4317
January	1st to 10th	Night	51% 21% 8% 12% 7%	8233
	11th to 20th	Night	52% 20% 5% 10% 9% 3	7880
	21st to end	Night	43% 22% 7% 19% 9% 1	8401
February	1st to 10th	Night	23% 59% 4 9% 5%	2593
	11th to 20th	Night	23% 58% 4 9% 5%	2459
	21st to end	Night	22% 59% 4 9% 6% 1	2076
March	1st to 10th	Night	40% 28% 3 21% 7% 2	5479
	11th to 20th	Night	26% 28% 7% 23% 15% 1	5090
	21st to end	Night	38% 28% 4 20% 9% 1	5588
April	1st to 10th	Night	22% 59% 4 9% 4	2140
	11th to 20th	Night	18% 59% 4 10% 6% 1	2034
	21st to end	Night	18% 59% 5% 11% 6% 1	1890
May	1st to 10th	Night	40% 24% 9% 18% 7% 1	5264
	11th to 20th	Night	34% 24% 11% 20% 10%	5235
	21st to end	Night	41% 24% 10% 15% 7% 3	5771
June	1st to 10th	Night	15% 59% 4 11% 11% 1	1868
	11th to 20th	Night	16% 60% 4 9% 9% 2	1680
	21st to end	Night	15% 59% 8% 10% 7% 1	1680
July	1st to 10th	Night	29% 24% 10% 21% 14% 2	4670
	11th to 20th	Night	31% 24% 10% 25% 10%	4885
	21st to end	Night	30% 24% 11% 20% 12% 2	5606
August	1st to 10th	Night	24% 38% 9% 23% 6% 1	2994
	11th to 20th	Night	23% 38% 6% 21% 11%	2955
	21st to end	Night	12% 37% 10% 25% 15% 1	3586
September	1st to 10th	Night	12% 58% 5% 12% 10% 2	2090
	11th to 20th	Night	11% 57% 4 13% 14% 1	2200
	21st to end	Night	16% 56% 5% 10% 12% 1	2200
October	1st to 10th	Night	12% 35% 3 18% 31% 1	3590
	11th to 20th	Night	13% 35% 6% 16% 27% 1	3824
	21st to end	Night	18% 36% 4 16% 23% 3	4530
November	1st to 10th	Night	22% 53% 5% 11% 8% 1	2666
	11th to 20th	Night	20% 54% 3 12% 9% 2	2730
	21st to end	Night	27% 54% 5% 10% 4	2730
December	1st to 10th	Night	32% 34% 7% 18% 9%	4380
	11th to 20th	Night	42% 31% 7% 13% 6%	4954
	21st to end	Night	56% 26% 5% 10% 3	6868

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% 15% 5% 1	330
	11th to 20th	Day	30% 25% 32% 11% 3	330
	21st to end	Day	30% 22% 31% 14% 4	363
February	1st to 10th	Day	26% 22% 33% 16% 3	330
	11th to 20th	Day	29% 25% 32% 12% 2 1	330
	21st to end	Day	29% 18% 41% 11% 1	273
March	1st to 10th	Day	26% 29% 31% 12% 1	330
	11th to 20th	Day	27% 21% 31% 16% 5%	540
	21st to end	Day	30% 19% 29% 17% 5%	594
April	1st to 10th	Day	23% 20% 30% 19% 8% 1	540
	11th to 20th	Day	23% 21% 26% 18% 9% 3	532
	21st to end	Day	22% 17% 34% 16% 8% 2	540
May	1st to 10th	Day	23% 14% 34% 17% 8% 3	543
	11th to 20th	Day	22% 13% 27% 23% 10% 5%	567
	21st to end	Day	16% 9% 28% 25% 14% 8%	617
June	1st to 10th	Day	14% 7% 25% 28% 18% 7%	585
	11th to 20th	Day	12% 8% 25% 32% 17% 6%	780
	21st to end	Day	10% 7% 27% 30% 18% 8%	780
July	1st to 10th	Day	12% 4 18% 28% 24% 15%	771
	11th to 20th	Day	9% 4 22% 29% 23% 12%	685
	21st to end	Day	12% 4 17% 32% 22% 13%	620
August	1st to 10th	Day	9% 4 18% 28% 25% 15%	566
	11th to 20th	Day	11% 4 20% 32% 20% 14%	535
	21st to end	Day	8% 4 16% 30% 28% 14%	583
September	1st to 10th	Day	11% 5% 17% 28% 30% 9%	530
	11th to 20th	Day	8% 4 14% 25% 32% 17%	530
	21st to end	Day	19% 9% 18% 22% 23% 8%	530
October	1st to 10th	Day	10% 7% 22% 32% 22% 8%	530
	11th to 20th	Day	15% 13% 31% 23% 14% 3	530
	21st to end	Day	23% 14% 38% 19% 5% 1	416
November	1st to 10th	Day	14% 18% 37% 20% 8% 3	330
	11th to 20th	Day	23% 22% 28% 20% 5% 2	330
	21st to end	Day	27% 17% 38% 15% 3	330
December	1st to 10th	Day	21% 22% 38% 12% 6%	330
	11th to 20th	Day	21% 21% 39% 14% 6%	330
	21st to end	Day	32% 18% 33% 13% 3	363
January	1st to 10th	Night	23% 17% 32% 23% 5%	1050
	11th to 20th	Night	28% 17% 33% 19% 3	910
	21st to end	Night	25% 15% 35% 22% 3	924
February	1st to 10th	Night	26% 13% 34% 25% 2	840
	11th to 20th	Night	25% 16% 34% 22% 2	823
	21st to end	Night	29% 14% 32% 23% 2	692
March	1st to 10th	Night	24% 14% 33% 25% 5%	840
	11th to 20th	Night	24% 14% 34% 22% 6% 1	840
	21st to end	Night	24% 14% 30% 26% 6%	924
April	1st to 10th	Night	20% 13% 34% 25% 8%	670
	11th to 20th	Night	19% 11% 33% 26% 9% 1	623
	21st to end	Night	19% 9% 37% 25% 9%	630
May	1st to 10th	Night	20% 10% 31% 27% 12%	630
	11th to 20th	Night	18% 7% 24% 33% 16% 2	621
	21st to end	Night	12% 4 23% 34% 24% 3	683
June	1st to 10th	Night	11% 3 20% 42% 22% 2	630
	11th to 20th	Night	10% 4 18% 41% 24% 3	630
	21st to end	Night	8% 2 22% 39% 26% 3	630
July	1st to 10th	Night	12% 3 12% 32% 33% 8%	615
	11th to 20th	Night	9% 3 15% 36% 33% 4	612
	21st to end	Night	11% 2 12% 39% 31% 4	690
August	1st to 10th	Night	9% 1 12% 37% 38% 3	627
	11th to 20th	Night	8% 2 16% 39% 30% 5%	606
	21st to end	Night	7% 13% 33% 39% 7%	660
September	1st to 10th	Night	13% 3 15% 32% 33% 4	690
	11th to 20th	Night	9% 3 14% 33% 36% 5%	800
	21st to end	Night	17% 5% 21% 31% 24% 3	800
October	1st to 10th	Night	11% 4 21% 36% 24% 5%	800
	11th to 20th	Night	17% 10% 24% 33% 15% 2	800
	21st to end	Night	22% 10% 32% 25% 11% 1	880
November	1st to 10th	Night	17% 9% 30% 28% 16% 1	820
	11th to 20th	Night	21% 15% 28% 25% 10%	840
	21st to end	Night	26% 10% 28% 28% 8%	840
December	1st to 10th	Night	26% 12% 34% 23% 6%	840
	11th to 20th	Night	24% 11% 33% 24% 6% 1	840
	21st to end	Night	30% 15% 29% 22% 3	1029

Page generated at 2026-08-12 03:37:18. Version ac07

Copyright © 2026 Attilla Danko.