ES Fox Observatory (BAS/BOEC)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ES Fox Observatory (BAS/BOEC) clear sky chart from 2005-11-06 to 2024-10-25.

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	15% 11% 4 9% 5% 4 4 4 5% 7% 33%	101431
	Night	16% 14% 5% 11% 6% 4 4 3 5% 6% 27%	97403
Transparency	Day	51% 7% 12% 19% 10% 1	101188
	Night	58% 7% 11% 15% 9% 1	97266
Seeing	Day	19% 11% 27% 27% 14% 4	15164
	Night	21% 11% 27% 27% 12% 2	24348

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% 24% 15% 17% 7% 4 5% 2 2 3 5%	2222
	11th to 20th	Day	11% 20% 10% 29% 9% 5% 4 3 3 2 5%	2569
	21st to end	Day	19% 21% 10% 16% 6% 5% 4 3 4 3 9%	3124
February	1st to 10th	Day	13% 21% 7% 19% 10% 5% 4 3 3 4 11%	1710
	11th to 20th	Day	12% 16% 7% 14% 8% 6% 6% 4 4 6% 17%	1663
	21st to end	Day	15% 17% 6% 12% 6% 6% 5% 4 5% 5% 20%	1532
March	1st to 10th	Day	16% 14% 4 8% 6% 5% 4 4 4 5% 30%	3327
	11th to 20th	Day	12% 17% 7% 10% 6% 5% 5% 4 5% 5% 24%	3480
	21st to end	Day	15% 12% 4 8% 6% 5% 5% 4 6% 6% 30%	3815
April	1st to 10th	Day	19% 12% 4 8% 4 4 4 3 5% 7% 30%	2191
	11th to 20th	Day	19% 9% 3 7% 4 3 3 3 4 5% 39%	2442
	21st to end	Day	20% 8% 3 7% 4 4 4 3 5% 7% 35%	2470
May	1st to 10th	Day	16% 8% 2 7% 4 4 4 3 5% 7% 40%	4108
	11th to 20th	Day	14% 7% 2 6% 3 4 5% 4 6% 8% 41%	4256
	21st to end	Day	14% 6% 2 5% 4 4 4 3 5% 7% 46%	4837
June	1st to 10th	Day	13% 8% 2 6% 4 4 4 5% 7% 7% 39%	2812
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	2850
	21st to end	Day	15% 7% 2 5% 4 4 4 4 6% 8% 42%	2850
July	1st to 10th	Day	14% 7% 2 6% 4 5% 5% 4 6% 8% 39%	4760
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 6% 8% 50%	4670
	21st to end	Day	9% 5% 2 5% 4 3 3 4 6% 9% 50%	4471
August	1st to 10th	Day	11% 6% 2 5% 4 4 4 4 6% 10% 43%	4104
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 6% 8% 43%	4044
	21st to end	Day	10% 6% 2 6% 3 5% 4 4 6% 9% 46%	4510
September	1st to 10th	Day	13% 6% 3 7% 4 4 4 4 5% 8% 41%	2252
	11th to 20th	Day	12% 6% 2 6% 3 4 4 4 5% 8% 44%	2090
	21st to end	Day	18% 7% 3 8% 4 4 5% 3 6% 6% 36%	2090
October	1st to 10th	Day	20% 9% 3 8% 5% 4 4 3 5% 6% 34%	1929
	11th to 20th	Day	24% 13% 4 9% 5% 4 5% 3 5% 5% 21%	1900
	21st to end	Day	30% 13% 5% 10% 6% 5% 3 2 3 5% 17%	1951
November	1st to 10th	Day	19% 19% 4 8% 6% 5% 4 4 5% 5% 20%	1634
	11th to 20th	Day	18% 22% 7% 10% 5% 4 6% 4 4 7% 16%	1520
	21st to end	Day	23% 26% 7% 11% 6% 4 3 3 4 4 9%	1520
December	1st to 10th	Day	17% 32% 9% 13% 6% 4 4 2 3 3 7%	1520
	11th to 20th	Day	19% 23% 8% 17% 6% 5% 4 2 4 4 9%	1777
	21st to end	Day	27% 24% 7% 14% 5% 3 4 3 3 3 6%	2431
January	1st to 10th	Night	15% 26% 12% 18% 8% 4 4 2 3 3 6%	4719
	11th to 20th	Night	15% 18% 9% 25% 9% 5% 4 3 3 3 6%	4397
	21st to end	Night	17% 20% 10% 15% 7% 6% 4 2 4 4 11%	4532
February	1st to 10th	Night	13% 21% 6% 17% 10% 6% 4 4 4 3 13%	2470
	11th to 20th	Night	13% 16% 7% 17% 7% 5% 4 3 4 5% 19%	2403
	21st to end	Night	15% 15% 5% 11% 7% 5% 4 4 5% 5% 22%	1918
March	1st to 10th	Night	13% 12% 4 9% 5% 4 4 3 5% 7% 35%	3512
	11th to 20th	Night	10% 16% 5% 9% 5% 4 4 3 5% 6% 33%	3479
	21st to end	Night	13% 12% 5% 11% 5% 5% 6% 4 4 5% 30%	3817
April	1st to 10th	Night	20% 12% 3 7% 5% 4 4 3 4 6% 31%	2002
	11th to 20th	Night	19% 9% 3 7% 3 3 4 3 5% 7% 37%	1687
	21st to end	Night	20% 9% 3 8% 5% 4 4 4 5% 5% 33%	1710
May	1st to 10th	Night	15% 6% 3 9% 4 4 4 4 5% 7% 38%	2833
	11th to 20th	Night	13% 8% 3 7% 5% 4 4 4 6% 7% 40%	2637
	21st to end	Night	12% 6% 2 8% 4 4 4 3 6% 7% 46%	2738
June	1st to 10th	Night	13% 8% 2 7% 5% 5% 4 4 6% 6% 39%	1363
	11th to 20th	Night	10% 5% 2 5% 5% 4 4 5% 7% 10% 42%	1330
	21st to end	Night	14% 7% 2 7% 4 3 5% 4 6% 7% 40%	1330
July	1st to 10th	Night	11% 8% 4 7% 4 3 3 3 4 7% 46%	2210
	11th to 20th	Night	12% 4 2 5% 4 4 4 3 6% 6% 50%	2296
	21st to end	Night	7% 7% 2 5% 5% 4 4 4 6% 7% 49%	3077
August	1st to 10th	Night	11% 7% 2 7% 4 4 4 3 6% 7% 43%	2825
	11th to 20th	Night	12% 6% 3 7% 4 4 5% 4 6% 8% 41%	2785
	21st to end	Night	11% 6% 2 6% 4 4 5% 3 5% 9% 45%	3124
September	1st to 10th	Night	11% 5% 2 6% 3 4 5% 5% 7% 8% 45%	1916
	11th to 20th	Night	12% 5% 2 6% 4 4 4 3 5% 7% 47%	2090
	21st to end	Night	16% 8% 3 8% 6% 5% 5% 3 5% 6% 36%	2090
October	1st to 10th	Night	19% 8% 3 7% 5% 4 5% 4 5% 7% 33%	2250
	11th to 20th	Night	25% 12% 3 9% 5% 4 4 4 5% 6% 22%	2280
	21st to end	Night	28% 14% 4 10% 5% 4 5% 4 4 5% 18%	2509
November	1st to 10th	Night	20% 17% 4 8% 5% 4 5% 3 5% 6% 24%	2443
	11th to 20th	Night	19% 20% 5% 11% 6% 5% 4 3 4 6% 16%	2660
	21st to end	Night	24% 24% 6% 9% 5% 4 4 3 4 5% 12%	2660
December	1st to 10th	Night	21% 29% 8% 13% 5% 4 3 2 4 3 7%	2660
	11th to 20th	Night	16% 25% 7% 16% 7% 4 4 3 4 4 10%	3415
	21st to end	Night	25% 22% 9% 15% 6% 4 4 2 3 3 7%	5236

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	84% 7% 6% 3	2223
	11th to 20th	Day	87% 5% 4 2 1	2569
	21st to end	Day	79% 9% 6% 3 1	3124
February	1st to 10th	Day	77% 7% 7% 8% 1	1710
	11th to 20th	Day	67% 10% 11% 8% 4	1672
	21st to end	Day	65% 7% 11% 12% 4	1532
March	1st to 10th	Day	55% 8% 14% 14% 8% 1	3330
	11th to 20th	Day	58% 8% 12% 15% 6% 1	3480
	21st to end	Day	49% 9% 15% 16% 9% 1	3815
April	1st to 10th	Day	54% 6% 12% 17% 10%	2191
	11th to 20th	Day	48% 4 9% 22% 15% 1	2442
	21st to end	Day	48% 7% 13% 19% 11% 3	2470
May	1st to 10th	Day	42% 7% 12% 19% 17% 2	4120
	11th to 20th	Day	38% 10% 16% 23% 12% 1	4260
	21st to end	Day	36% 7% 13% 20% 19% 5%	4837
June	1st to 10th	Day	40% 9% 12% 23% 15% 1	2812
	11th to 20th	Day	37% 6% 12% 25% 18% 1	2850
	21st to end	Day	40% 8% 13% 23% 14% 2	2850
July	1st to 10th	Day	41% 7% 16% 20% 14% 1	4686
	11th to 20th	Day	30% 6% 16% 34% 12% 1	4589
	21st to end	Day	31% 7% 13% 31% 18% 1	4329
August	1st to 10th	Day	35% 7% 15% 27% 14% 1	4091
	11th to 20th	Day	40% 6% 17% 25% 12%	4083
	21st to end	Day	34% 7% 15% 33% 11% 1	4510
September	1st to 10th	Day	40% 8% 14% 25% 12% 1	2252
	11th to 20th	Day	36% 8% 15% 28% 13%	2090
	21st to end	Day	48% 9% 12% 22% 8%	2090
October	1st to 10th	Day	51% 7% 12% 19% 10% 1	1929
	11th to 20th	Day	63% 7% 12% 12% 5% 1	1900
	21st to end	Day	70% 5% 9% 12% 3	1951
November	1st to 10th	Day	65% 5% 12% 13% 5%	1634
	11th to 20th	Day	68% 9% 11% 7% 5%	1520
	21st to end	Day	78% 7% 9% 5%	1520
December	1st to 10th	Day	84% 7% 5% 2 1	1520
	11th to 20th	Day	80% 7% 9% 4	1776
	21st to end	Day	84% 5% 8% 3	2431
January	1st to 10th	Night	84% 7% 6% 3	4719
	11th to 20th	Night	86% 6% 5% 2 1	4397
	21st to end	Night	76% 10% 9% 4 1	4532
February	1st to 10th	Night	75% 7% 8% 8% 2	2470
	11th to 20th	Night	68% 7% 10% 11% 4	2405
	21st to end	Night	63% 7% 13% 11% 6%	1918
March	1st to 10th	Night	48% 8% 16% 18% 9% 1	3522
	11th to 20th	Night	50% 7% 14% 18% 9% 2	3480
	21st to end	Night	51% 9% 11% 18% 10% 1	3817
April	1st to 10th	Night	54% 5% 10% 19% 11% 1	2002
	11th to 20th	Night	47% 5% 9% 20% 18% 1	1687
	21st to end	Night	53% 6% 9% 15% 15% 2	1710
May	1st to 10th	Night	42% 7% 13% 18% 18% 2	2840
	11th to 20th	Night	41% 7% 11% 22% 17% 2	2638
	21st to end	Night	37% 7% 11% 22% 20% 4	2739
June	1st to 10th	Night	42% 7% 10% 21% 18% 2	1363
	11th to 20th	Night	35% 6% 14% 25% 19% 2	1330
	21st to end	Night	40% 7% 12% 25% 14% 2	1330
July	1st to 10th	Night	39% 5% 12% 22% 16% 5%	2175
	11th to 20th	Night	32% 7% 10% 35% 15% 1	2254
	21st to end	Night	33% 7% 12% 24% 23% 1	2979
August	1st to 10th	Night	39% 6% 15% 25% 14% 1	2814
	11th to 20th	Night	40% 8% 17% 20% 14% 1	2812
	21st to end	Night	35% 6% 14% 31% 13% 1	3124
September	1st to 10th	Night	34% 8% 14% 28% 14% 2	1916
	11th to 20th	Night	35% 8% 15% 28% 14%	2090
	21st to end	Night	47% 8% 13% 22% 10%	2090
October	1st to 10th	Night	50% 8% 10% 20% 11% 1	2250
	11th to 20th	Night	61% 8% 11% 15% 5%	2280
	21st to end	Night	69% 7% 9% 11% 4	2509
November	1st to 10th	Night	61% 7% 11% 17% 4	2443
	11th to 20th	Night	68% 7% 13% 8% 3 1	2660
	21st to end	Night	73% 9% 11% 6% 1	2660
December	1st to 10th	Night	83% 7% 6% 3 1	2660
	11th to 20th	Night	78% 9% 9% 4	3415
	21st to end	Night	84% 5% 8% 2	5236

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% 19% 32% 19% 4 2	186
	11th to 20th	Day	20% 16% 39% 19% 6%	270
	21st to end	Day	28% 13% 30% 22% 7%	297
February	1st to 10th	Day	22% 23% 34% 17% 3	270
	11th to 20th	Day	23% 17% 39% 20% 2	270
	21st to end	Day	20% 28% 36% 15% 1	225
March	1st to 10th	Day	21% 14% 35% 22% 7% 1	389
	11th to 20th	Day	20% 15% 32% 26% 6% 1	460
	21st to end	Day	23% 13% 30% 26% 6% 2	506
April	1st to 10th	Day	21% 13% 32% 24% 10%	460
	11th to 20th	Day	26% 13% 29% 17% 10% 5%	452
	21st to end	Day	25% 10% 27% 26% 10% 1	460
May	1st to 10th	Day	20% 8% 27% 30% 13% 2	463
	11th to 20th	Day	16% 7% 24% 32% 17% 3	487
	21st to end	Day	12% 7% 24% 30% 22% 5%	529
June	1st to 10th	Day	13% 6% 27% 35% 16% 3	642
	11th to 20th	Day	12% 7% 26% 35% 17% 4	680
	21st to end	Day	17% 5% 26% 33% 15% 3	680
July	1st to 10th	Day	10% 4 22% 34% 25% 4	671
	11th to 20th	Day	11% 6% 23% 34% 19% 6%	668
	21st to end	Day	11% 4 20% 39% 19% 7%	537
August	1st to 10th	Day	13% 5% 21% 32% 20% 9%	486
	11th to 20th	Day	14% 4 14% 37% 23% 9%	479
	21st to end	Day	15% 6% 22% 29% 21% 7%	539
September	1st to 10th	Day	15% 7% 21% 33% 18% 6%	490
	11th to 20th	Day	10% 6% 21% 26% 26% 11%	490
	21st to end	Day	18% 11% 22% 25% 19% 5%	490
October	1st to 10th	Day	21% 13% 24% 23% 14% 4	490
	11th to 20th	Day	24% 17% 31% 22% 4 1	490
	21st to end	Day	32% 15% 30% 17% 5%	438
November	1st to 10th	Day	30% 16% 27% 19% 8%	252
	11th to 20th	Day	30% 19% 28% 18% 3 2	180
	21st to end	Day	28% 22% 34% 14% 2	180
December	1st to 10th	Day	30% 19% 31% 17% 4	180
	11th to 20th	Day	29% 22% 29% 16% 4	180
	21st to end	Day	34% 21% 35% 8% 2 1	198
January	1st to 10th	Night	24% 18% 31% 21% 5% 1	950
	11th to 20th	Night	28% 15% 31% 20% 6% 1	920
	21st to end	Night	21% 10% 33% 27% 8% 1	836
February	1st to 10th	Night	21% 16% 36% 22% 4	760
	11th to 20th	Night	19% 12% 36% 26% 6% 1	743
	21st to end	Night	22% 15% 35% 23% 4	628
March	1st to 10th	Night	18% 11% 37% 26% 8%	760
	11th to 20th	Night	19% 14% 34% 25% 7% 1	760
	21st to end	Night	20% 8% 31% 29% 11% 1	836
April	1st to 10th	Night	23% 11% 30% 29% 6% 1	760
	11th to 20th	Night	23% 9% 26% 28% 12% 2	563
	21st to end	Night	25% 7% 26% 28% 14% 1	570
May	1st to 10th	Night	16% 4 23% 39% 16% 2	570
	11th to 20th	Night	18% 3 19% 39% 20% 1	464
	21st to end	Night	12% 3 23% 38% 21% 3	411
June	1st to 10th	Night	14% 7% 22% 38% 17% 2	380
	11th to 20th	Night	10% 5% 23% 38% 22% 1	380
	21st to end	Night	16% 3 20% 35% 24% 1	380
July	1st to 10th	Night	10% 4 14% 46% 24% 2	370
	11th to 20th	Night	10% 3 19% 34% 30% 3	415
	21st to end	Night	9% 3 17% 42% 29% 1	624
August	1st to 10th	Night	12% 4 16% 36% 31% 2	567
	11th to 20th	Night	9% 4 16% 33% 31% 6%	564
	21st to end	Night	13% 5% 21% 30% 28% 4	627
September	1st to 10th	Night	11% 6% 21% 34% 22% 7%	750
	11th to 20th	Night	13% 5% 19% 33% 24% 6%	760
	21st to end	Night	18% 8% 21% 27% 20% 6%	760
October	1st to 10th	Night	21% 10% 24% 27% 16% 2	760
	11th to 20th	Night	29% 15% 22% 24% 8% 2	760
	21st to end	Night	33% 13% 27% 22% 4 1	812
November	1st to 10th	Night	30% 13% 27% 21% 8% 1	740
	11th to 20th	Night	27% 19% 29% 17% 8%	760
	21st to end	Night	36% 15% 29% 18% 3	760
December	1st to 10th	Night	33% 20% 30% 12% 4	760
	11th to 20th	Night	25% 20% 35% 16% 3	843
	21st to end	Night	33% 14% 34% 15% 3	1045

Page generated at 2024-10-22 20:21:04. Version ac07

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