Esparto
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Esparto clear sky chart from 2005-11-06 to 2024-12-24.

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	6% 3 1 3 2 2 3 2 4 5% 68%	105540
	Night	7% 3 1 3 2 3 3 2 4 5% 65%	103323
Transparency	Day	20% 3 8% 19% 25% 25%	105295
	Night	23% 3 9% 19% 23% 24%	103157
Seeing	Day	8% 5% 17% 26% 27% 17%	15389
	Night	8% 4 16% 36% 31% 4	24735

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	16% 8% 3 6% 4 4 4 2 5% 7% 41%	2581
	11th to 20th	Day	18% 9% 3 8% 5% 4 5% 2 4 6% 37%	2860
	21st to end	Day	22% 7% 3 7% 4 4 4 3 5% 7% 33%	3146
February	1st to 10th	Day	14% 5% 1 5% 4 4 4 3 4 6% 50%	1710
	11th to 20th	Day	10% 6% 2 5% 4 4 4 3 5% 7% 49%	1737
	21st to end	Day	11% 4 1 5% 3 4 4 4 5% 7% 51%	1570
March	1st to 10th	Day	11% 7% 3 8% 6% 5% 5% 4 6% 7% 36%	3346
	11th to 20th	Day	8% 5% 1 4 3 3 3 3 4 6% 60%	3490
	21st to end	Day	12% 5% 2 6% 5% 6% 5% 4 6% 7% 42%	3905
April	1st to 10th	Day	9% 6% 3 5% 4 4 4 4 6% 7% 49%	2280
	11th to 20th	Day	7% 3 1 3 3 4 4 3 5% 7% 60%	2249
	21st to end	Day	3 2 1 3 3 3 3 3 5% 7% 66%	2280
May	1st to 10th	Day	5% 2 1 2 2 1 2 2 3 5% 76%	3975
	11th to 20th	Day	2 1 2 1 1 1 2 2 5% 82%	4274
	21st to end	Day	1 1 1 2 2 2 2 3 5% 79%	4813
June	1st to 10th	Day	4 3 1 2 2 2 2 3 4 8% 69%	2660
	11th to 20th	Day	1 1 1 1 2 2 3 4 83%	2660
	21st to end	Day	1 1 1 1 1 2 2 3 3 86%	2660
July	1st to 10th	Day	1 1 1 1 2 93%	4420
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 87%	4277
	21st to end	Day	1 1 1 1 2 3 91%	4455
August	1st to 10th	Day	1 1 1 1 1 2 2 2 5% 5% 78%	4091
	11th to 20th	Day	1 1 1 1 1 2 3 90%	3854
	21st to end	Day	1 1 1 1 1 1 1 2 2 89%	4180
September	1st to 10th	Day	1 1 1 1 1 2 3 90%	2280
	11th to 20th	Day	2 1 1 2 2 1 2 2 3 5% 79%	2280
	21st to end	Day	2 2 1 2 1 1 1 2 2 3 82%	2019
October	1st to 10th	Day	1 1 1 2 2 2 2 2 4 5% 79%	3180
	11th to 20th	Day	3 2 1 2 1 2 2 2 4 5% 75%	3161
	21st to end	Day	4 2 1 3 2 3 3 3 4 6% 68%	3448
November	1st to 10th	Day	7% 3 1 3 3 3 4 3 5% 7% 62%	1870
	11th to 20th	Day	9% 5% 2 4 4 5% 3 3 5% 9% 52%	1800
	21st to end	Day	9% 4 1 4 3 3 3 3 5% 7% 58%	1603
December	1st to 10th	Day	12% 5% 2 6% 4 3 3 3 4 8% 50%	1600
	11th to 20th	Day	23% 9% 3 8% 4 4 4 2 5% 4 34%	2008
	21st to end	Day	18% 9% 2 5% 4 4 3 4 5% 7% 38%	2818
January	1st to 10th	Night	13% 6% 2 6% 3 4 4 3 5% 8% 46%	4361
	11th to 20th	Night	17% 8% 3 7% 5% 4 5% 3 6% 6% 36%	4110
	21st to end	Night	19% 7% 2 7% 4 4 5% 4 5% 6% 36%	4521
February	1st to 10th	Night	14% 4 2 4 4 4 4 4 4 6% 52%	2470
	11th to 20th	Night	9% 3 2 5% 3 3 4 4 6% 7% 52%	2328
	21st to end	Night	11% 5% 1 4 2 3 3 4 4 7% 56%	1884
March	1st to 10th	Night	10% 7% 2 7% 5% 5% 5% 4 5% 8% 43%	3525
	11th to 20th	Night	11% 3 1 3 2 2 3 2 3 4 63%	3490
	21st to end	Night	11% 5% 2 6% 4 4 5% 3 6% 7% 46%	3747
April	1st to 10th	Night	6% 5% 1 4 3 4 5% 4 5% 6% 56%	1900
	11th to 20th	Night	7% 3 1 3 3 3 3 3 4 6% 64%	1879
	21st to end	Night	4 2 1 2 2 2 2 3 4 8% 71%	1900
May	1st to 10th	Night	3 1 2 1 2 2 2 3 5% 80%	2996
	11th to 20th	Night	1 1 1 1 1 2 2 2 4 84%	2622
	21st to end	Night	1 1 1 1 1 1 1 3 4 85%	2762
June	1st to 10th	Night	3 2 1 2 3 2 3 3 4 7% 72%	1520
	11th to 20th	Night	1 1 1 1 2 2 3 4 85%	1520
	21st to end	Night	1 1 1 1 1 1 1 2 2 3 86%	1520
July	1st to 10th	Night	1 1 1 1 1 94%	2540
	11th to 20th	Night	1 1 1 1 1 1 1 1 2 2 87%	2684
	21st to end	Night	1 1 1 1 1 1 2 3 89%	3109
August	1st to 10th	Night	3 2 1 2 1 1 2 2 4 5% 79%	2848
	11th to 20th	Night	1 1 1 1 1 2 2 91%	2990
	21st to end	Night	2 1 1 1 1 1 1 2 2 89%	3498
September	1st to 10th	Night	1 1 1 1 1 2 3 90%	1900
	11th to 20th	Night	2 1 2 2 1 1 1 3 5% 81%	1900
	21st to end	Night	1 1 1 1 1 2 1 3 5% 84%	2156
October	1st to 10th	Night	2 1 1 2 2 2 2 2 3 4 80%	3800
	11th to 20th	Night	2 1 2 1 2 2 3 3 4 79%	3777
	21st to end	Night	4 2 1 3 2 2 3 3 5% 7% 68%	4121
November	1st to 10th	Night	6% 3 1 3 3 3 3 3 5% 7% 61%	2425
	11th to 20th	Night	7% 4 1 3 3 3 3 3 5% 8% 60%	2600
	21st to end	Night	8% 4 2 4 3 3 4 2 4 6% 60%	2794
December	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 4 7% 52%	2800
	11th to 20th	Night	23% 8% 2 5% 4 3 3 3 6% 7% 35%	3416
	21st to end	Night	16% 8% 3 7% 4 5% 4 4 5% 7% 37%	4910

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	45% 4 16% 24% 8% 2	2581
	11th to 20th	Day	51% 3 12% 15% 12% 6%	2860
	21st to end	Day	52% 4 12% 16% 12% 4	3146
February	1st to 10th	Day	37% 4 10% 22% 18% 9%	1710
	11th to 20th	Day	35% 5% 10% 21% 21% 8%	1746
	21st to end	Day	32% 5% 10% 26% 20% 8%	1570
March	1st to 10th	Day	46% 5% 12% 17% 17% 3	3346
	11th to 20th	Day	26% 3 13% 25% 20% 13%	3490
	21st to end	Day	39% 7% 15% 23% 13% 3	3905
April	1st to 10th	Day	34% 5% 12% 22% 19% 7%	2280
	11th to 20th	Day	24% 4 13% 25% 24% 9%	2252
	21st to end	Day	18% 4 13% 29% 28% 8%	2280
May	1st to 10th	Day	13% 3 7% 29% 25% 23%	3975
	11th to 20th	Day	9% 2 5% 26% 38% 20%	4277
	21st to end	Day	9% 3 10% 36% 29% 14%	4814
June	1st to 10th	Day	16% 4 10% 28% 29% 13%	2660
	11th to 20th	Day	7% 3 7% 21% 36% 27%	2660
	21st to end	Day	6% 1 3 13% 37% 40%	2660
July	1st to 10th	Day	2 1 1 6% 16% 73%	4351
	11th to 20th	Day	6% 1 2 8% 18% 66%	4202
	21st to end	Day	3 1 2 7% 26% 61%	4315
August	1st to 10th	Day	9% 2 2 9% 27% 51%	4076
	11th to 20th	Day	3 1 1 10% 43% 42%	3893
	21st to end	Day	5% 1 2 12% 38% 42%	4179
September	1st to 10th	Day	5% 1 2 7% 31% 54%	2280
	11th to 20th	Day	11% 1 5% 24% 40% 19%	2280
	21st to end	Day	9% 2 5% 20% 31% 33%	2019
October	1st to 10th	Day	11% 2 4 12% 26% 45%	3180
	11th to 20th	Day	13% 3 6% 27% 28% 22%	3161
	21st to end	Day	18% 3 7% 24% 32% 15%	3448
November	1st to 10th	Day	23% 4 8% 29% 23% 12%	1870
	11th to 20th	Day	31% 4 13% 25% 20% 7%	1800
	21st to end	Day	27% 4 13% 23% 22% 12%	1603
December	1st to 10th	Day	35% 4 11% 24% 18% 9%	1600
	11th to 20th	Day	55% 4 9% 13% 16% 3	2008
	21st to end	Day	47% 4 15% 19% 12% 3	2818
January	1st to 10th	Night	37% 5% 21% 23% 10% 4	4361
	11th to 20th	Night	49% 5% 14% 13% 11% 7%	4110
	21st to end	Night	49% 4 13% 15% 13% 5%	4521
February	1st to 10th	Night	34% 4 8% 21% 21% 11%	2470
	11th to 20th	Night	30% 4 10% 23% 22% 10%	2330
	21st to end	Night	29% 4 8% 27% 24% 8%	1884
March	1st to 10th	Night	40% 5% 16% 19% 17% 4	3525
	11th to 20th	Night	26% 3 8% 25% 25% 13%	3490
	21st to end	Night	36% 6% 14% 25% 15% 4	3747
April	1st to 10th	Night	28% 5% 13% 23% 22% 9%	1900
	11th to 20th	Night	22% 4 12% 28% 20% 13%	1879
	21st to end	Night	14% 3 13% 31% 30% 9%	1900
May	1st to 10th	Night	9% 3 9% 27% 30% 22%	2996
	11th to 20th	Night	7% 1 5% 20% 36% 30%	2622
	21st to end	Night	7% 1 8% 37% 30% 17%	2762
June	1st to 10th	Night	14% 3 10% 26% 30% 16%	1520
	11th to 20th	Night	7% 2 5% 21% 33% 32%	1520
	21st to end	Night	7% 1 3 11% 31% 47%	1520
July	1st to 10th	Night	3 1 5% 15% 76%	2500
	11th to 20th	Night	7% 1 2 6% 14% 71%	2636
	21st to end	Night	4 1 5% 22% 68%	3011
August	1st to 10th	Night	11% 1 1 8% 22% 58%	2839
	11th to 20th	Night	3 1 1 5% 34% 56%	3017
	21st to end	Night	7% 1 1 8% 34% 50%	3498
September	1st to 10th	Night	4 1 2 6% 28% 59%	1900
	11th to 20th	Night	10% 1 4 20% 37% 27%	1900
	21st to end	Night	7% 2 4 18% 31% 39%	2156
October	1st to 10th	Night	11% 2 3 11% 20% 53%	3800
	11th to 20th	Night	10% 3 7% 28% 28% 24%	3777
	21st to end	Night	18% 2 6% 22% 31% 22%	4121
November	1st to 10th	Night	22% 5% 9% 25% 22% 16%	2425
	11th to 20th	Night	25% 3 12% 28% 23% 10%	2600
	21st to end	Night	27% 3 9% 23% 25% 14%	2794
December	1st to 10th	Night	34% 3 11% 21% 20% 11%	2800
	11th to 20th	Night	48% 5% 10% 15% 17% 4	3416
	21st to end	Night	47% 5% 14% 16% 13% 3	4910

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	32% 3 22% 25% 16% 2	209
	11th to 20th	Day	16% 6% 25% 29% 19% 5%	370
	21st to end	Day	17% 6% 21% 25% 24% 7%	407
February	1st to 10th	Day	18% 8% 21% 25% 21% 7%	370
	11th to 20th	Day	17% 12% 23% 26% 15% 7%	399
	21st to end	Day	14% 10% 25% 31% 17% 4	382
March	1st to 10th	Day	17% 9% 26% 28% 13% 5%	460
	11th to 20th	Day	17% 8% 20% 28% 18% 8%	460
	21st to end	Day	15% 11% 26% 28% 16% 5%	506
April	1st to 10th	Day	11% 8% 22% 28% 22% 8%	460
	11th to 20th	Day	8% 10% 25% 26% 19% 13%	452
	21st to end	Day	5% 8% 22% 25% 25% 15%	460
May	1st to 10th	Day	6% 8% 25% 27% 24% 11%	463
	11th to 20th	Day	6% 3 20% 25% 23% 24%	488
	21st to end	Day	4 5% 15% 28% 24% 24%	529
June	1st to 10th	Day	4 4 18% 24% 30% 21%	490
	11th to 20th	Day	1 6% 18% 27% 34% 14%	490
	21st to end	Day	3 12% 28% 33% 25%	490
July	1st to 10th	Day	1 1 6% 25% 38% 29%	486
	11th to 20th	Day	1 6% 23% 35% 35%	484
	21st to end	Day	1 1 5% 21% 42% 31%	531
August	1st to 10th	Day	3 1 7% 21% 38% 29%	487
	11th to 20th	Day	2 1 8% 25% 32% 31%	477
	21st to end	Day	1 1 5% 22% 38% 34%	539
September	1st to 10th	Day	8% 28% 39% 24%	490
	11th to 20th	Day	3 2 11% 25% 34% 25%	490
	21st to end	Day	2 3 14% 29% 33% 19%	490
October	1st to 10th	Day	3 6% 17% 25% 29% 20%	490
	11th to 20th	Day	6% 5% 16% 25% 32% 17%	490
	21st to end	Day	8% 5% 21% 26% 29% 12%	539
November	1st to 10th	Day	9% 6% 23% 21% 30% 11%	406
	11th to 20th	Day	11% 6% 19% 28% 25% 11%	300
	21st to end	Day	13% 4 23% 32% 21% 6%	201
December	1st to 10th	Day	20% 3 24% 25% 22% 7%	200
	11th to 20th	Day	18% 5% 23% 31% 17% 8%	200
	21st to end	Day	21% 8% 23% 25% 18% 6%	204
January	1st to 10th	Night	16% 5% 18% 36% 20% 5%	760
	11th to 20th	Night	14% 4 19% 39% 19% 4	760
	21st to end	Night	16% 5% 17% 35% 23% 4	836
February	1st to 10th	Night	16% 6% 19% 36% 21% 2	760
	11th to 20th	Night	11% 7% 22% 36% 20% 5%	744
	21st to end	Night	13% 7% 24% 37% 17% 2	628
March	1st to 10th	Night	16% 5% 22% 33% 22% 3	760
	11th to 20th	Night	14% 6% 19% 33% 27% 2	760
	21st to end	Night	14% 6% 25% 36% 19% 1	836
April	1st to 10th	Night	9% 7% 20% 42% 21% 3	760
	11th to 20th	Night	9% 6% 24% 35% 23% 3	751
	21st to end	Night	5% 6% 24% 38% 24% 4	760
May	1st to 10th	Night	5% 4 26% 36% 25% 4	654
	11th to 20th	Night	2 3 16% 37% 37% 5%	441
	21st to end	Night	4 3 17% 36% 36% 3	411
June	1st to 10th	Night	3 2 15% 41% 35% 3	380
	11th to 20th	Night	1 3 18% 44% 33% 2	380
	21st to end	Night	1 1 8% 46% 41% 3	380
July	1st to 10th	Night	1 4 41% 50% 4	370
	11th to 20th	Night	4 34% 57% 5%	447
	21st to end	Night	2 3 32% 56% 8%	624
August	1st to 10th	Night	2 1 5% 32% 54% 7%	567
	11th to 20th	Night	1 1 5% 40% 47% 7%	664
	21st to end	Night	1 4 33% 55% 6%	836
September	1st to 10th	Night	1 1 5% 39% 48% 6%	760
	11th to 20th	Night	3 9% 37% 44% 7%	760
	21st to end	Night	1 2 14% 36% 38% 10%	760
October	1st to 10th	Night	4 3 13% 39% 33% 7%	760
	11th to 20th	Night	5% 3 17% 36% 34% 6%	760
	21st to end	Night	7% 3 16% 34% 30% 9%	836
November	1st to 10th	Night	7% 4 19% 31% 34% 5%	780
	11th to 20th	Night	9% 4 17% 39% 27% 4	800
	21st to end	Night	11% 5% 20% 38% 22% 4	800
December	1st to 10th	Night	16% 5% 20% 33% 22% 5%	800
	11th to 20th	Night	20% 4 18% 33% 22% 3	800
	21st to end	Night	18% 7% 21% 35% 18% 1	850

Page generated at 2024-12-21 01:13:48. Version ac07

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