EverStaR Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the EverStaR Observatory clear sky chart from 2005-11-06 to 2024-10-24.

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	11% 7% 3 6% 4 4 4 3 5% 7% 45%	100873
	Night	11% 7% 3 6% 4 3 4 3 5% 6% 48%	97975
Transparency	Day	38% 6% 12% 26% 16% 2	100686
	Night	36% 5% 12% 26% 18% 3	97833
Seeing	Day	14% 9% 29% 28% 16% 4	15629
	Night	13% 9% 33% 33% 11% 1	25438

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	14% 11% 3 9% 4 4 3 4 5% 6% 37%	2847
	11th to 20th	Day	9% 12% 4 9% 6% 7% 5% 2 3 4 38%	2850
	21st to end	Day	14% 16% 6% 8% 4 3 3 2 4 5% 35%	3135
February	1st to 10th	Day	15% 11% 4 7% 5% 4 3 2 4 5% 39%	1710
	11th to 20th	Day	11% 11% 3 7% 3 4 5% 3 6% 6% 41%	1664
	21st to end	Day	11% 9% 3 6% 4 4 4 4 5% 6% 44%	1625
March	1st to 10th	Day	13% 10% 2 6% 4 3 3 3 4 6% 47%	3436
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 5% 6% 53%	3480
	21st to end	Day	15% 12% 5% 7% 4 4 4 3 4 6% 36%	3814
April	1st to 10th	Day	14% 8% 2 6% 4 4 3 3 5% 6% 45%	2186
	11th to 20th	Day	14% 9% 3 6% 4 5% 4 3 5% 7% 41%	2254
	21st to end	Day	19% 8% 3 7% 5% 5% 4 3 4 6% 37%	2422
May	1st to 10th	Day	15% 9% 3 6% 5% 4 5% 3 6% 6% 39%	4082
	11th to 20th	Day	16% 7% 3 7% 4 4 4 4 5% 7% 39%	4082
	21st to end	Day	12% 6% 3 5% 5% 4 4 4 5% 8% 44%	4529
June	1st to 10th	Day	7% 4 2 5% 4 4 6% 4 7% 10% 48%	2660
	11th to 20th	Day	7% 5% 2 5% 4 5% 5% 4 7% 9% 47%	2660
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 9% 52%	2617
July	1st to 10th	Day	10% 7% 2 7% 5% 4 4 5% 6% 9% 41%	4120
	11th to 20th	Day	5% 3 2 5% 3 3 4 4 7% 10% 53%	4120
	21st to end	Day	6% 3 2 5% 5% 5% 6% 5% 8% 10% 45%	4465
August	1st to 10th	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	4104
	11th to 20th	Day	10% 6% 2 5% 4 4 4 4 5% 8% 47%	4041
	21st to end	Day	6% 4 2 5% 3 4 4 3 6% 8% 56%	4281
September	1st to 10th	Day	13% 5% 2 4 3 3 3 3 4 7% 53%	2280
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 5% 7% 49%	2095
	21st to end	Day	9% 5% 2 6% 3 4 4 3 5% 7% 54%	2085
October	1st to 10th	Day	11% 5% 2 5% 3 2 4 3 5% 7% 53%	1900
	11th to 20th	Day	11% 7% 2 4 3 3 2 2 4 6% 57%	1900
	21st to end	Day	15% 7% 3 5% 4 3 3 3 4 6% 48%	2010
November	1st to 10th	Day	9% 6% 1 5% 3 4 4 3 4 7% 55%	1851
	11th to 20th	Day	13% 7% 2 5% 3 3 3 3 4 7% 51%	1658
	21st to end	Day	14% 8% 2 6% 4 3 2 2 4 5% 48%	1520
December	1st to 10th	Day	9% 9% 4 6% 5% 4 4 3 5% 8% 46%	1520
	11th to 20th	Day	11% 10% 3 8% 5% 4 3 4 5% 5% 41%	1918
	21st to end	Day	15% 16% 7% 13% 4 3 4 3 5% 5% 25%	2952
January	1st to 10th	Night	9% 10% 3 14% 6% 4 4 2 3 5% 40%	4108
	11th to 20th	Night	10% 9% 3 9% 5% 7% 6% 3 4 5% 38%	4120
	21st to end	Night	16% 13% 4 11% 4 3 3 3 4 5% 35%	4532
February	1st to 10th	Night	11% 11% 3 7% 6% 4 4 3 5% 6% 39%	2470
	11th to 20th	Night	12% 10% 3 6% 4 4 4 3 4 7% 43%	2403
	21st to end	Night	13% 8% 3 6% 5% 4 3 3 4 5% 47%	1843
March	1st to 10th	Night	12% 9% 3 5% 3 3 3 3 4 5% 50%	3419
	11th to 20th	Night	10% 7% 2 5% 3 2 3 3 5% 7% 55%	3480
	21st to end	Night	15% 9% 4 8% 4 4 4 3 5% 6% 38%	3817
April	1st to 10th	Night	10% 7% 3 5% 4 4 3 3 5% 6% 50%	1992
	11th to 20th	Night	13% 8% 3 6% 4 3 3 3 5% 5% 48%	1875
	21st to end	Night	17% 7% 3 6% 4 4 3 3 5% 6% 43%	1753
May	1st to 10th	Night	15% 7% 3 6% 5% 4 4 4 7% 7% 40%	2823
	11th to 20th	Night	15% 7% 2 5% 4 3 4 3 6% 7% 44%	2823
	21st to end	Night	11% 5% 1 5% 4 3 3 3 5% 7% 53%	3032
June	1st to 10th	Night	5% 3 1 4 4 5% 4 5% 6% 9% 55%	1520
	11th to 20th	Night	5% 3 2 5% 4 5% 4 4 7% 11% 51%	1520
	21st to end	Night	4 3 1 4 3 2 3 4 6% 8% 61%	1555
July	1st to 10th	Night	10% 7% 3 7% 3 4 4 3 6% 7% 47%	2850
	11th to 20th	Night	2 3 1 4 3 3 4 3 6% 10% 60%	2850
	21st to end	Night	5% 3 2 4 4 4 5% 5% 8% 12% 48%	3098
August	1st to 10th	Night	2 2 1 3 3 3 6% 4 6% 10% 60%	2836
	11th to 20th	Night	10% 6% 2 5% 4 3 4 3 5% 6% 52%	2798
	21st to end	Night	3 3 2 5% 4 4 4 3 5% 7% 60%	3377
September	1st to 10th	Night	9% 5% 2 4 4 3 3 3 5% 4 58%	1900
	11th to 20th	Night	9% 4 1 4 4 3 4 4 6% 7% 54%	2081
	21st to end	Night	6% 4 2 5% 4 4 4 3 4 6% 58%	2090
October	1st to 10th	Night	10% 5% 1 4 3 4 3 3 4 5% 58%	2266
	11th to 20th	Night	12% 5% 2 4 3 2 3 2 3 5% 58%	2280
	21st to end	Night	15% 8% 2 5% 3 2 3 2 4 4 52%	2413
November	1st to 10th	Night	9% 4 1 4 3 3 3 2 4 5% 61%	2224
	11th to 20th	Night	10% 7% 2 4 3 3 3 3 5% 7% 54%	2518
	21st to end	Night	14% 7% 2 4 3 3 3 3 3 5% 52%	2660
December	1st to 10th	Night	11% 8% 3 6% 5% 3 4 4 5% 6% 46%	2660
	11th to 20th	Night	11% 9% 3 8% 4 4 4 3 5% 7% 45%	3279
	21st to end	Night	17% 17% 6% 10% 4 4 3 2 3 4 30%	4710

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	48% 4 11% 24% 13% 1	2848
	11th to 20th	Day	51% 3 12% 22% 11% 1	2850
	21st to end	Day	53% 4 11% 17% 15% 1	3135
February	1st to 10th	Day	49% 4 12% 22% 10% 3	1710
	11th to 20th	Day	43% 6% 12% 22% 14% 2	1673
	21st to end	Day	40% 5% 11% 24% 16% 4	1625
March	1st to 10th	Day	39% 5% 9% 22% 22% 3	3436
	11th to 20th	Day	32% 5% 13% 28% 19% 3	3480
	21st to end	Day	49% 6% 15% 24% 6% 1	3814
April	1st to 10th	Day	40% 5% 12% 24% 18% 2	2186
	11th to 20th	Day	43% 5% 12% 22% 16% 1	2254
	21st to end	Day	49% 6% 11% 23% 11% 1	2422
May	1st to 10th	Day	45% 8% 10% 22% 13% 2	4120
	11th to 20th	Day	42% 8% 13% 22% 14%	4086
	21st to end	Day	37% 8% 11% 30% 12% 2	4542
June	1st to 10th	Day	29% 9% 16% 29% 15% 2	2660
	11th to 20th	Day	31% 8% 15% 29% 16% 2	2660
	21st to end	Day	28% 7% 15% 29% 17% 4	2617
July	1st to 10th	Day	39% 7% 13% 20% 18% 3	4056
	11th to 20th	Day	24% 7% 13% 36% 18% 2	4051
	21st to end	Day	28% 8% 17% 32% 13% 2	4325
August	1st to 10th	Day	27% 7% 14% 29% 22% 2	4090
	11th to 20th	Day	36% 6% 17% 25% 15% 1	4080
	21st to end	Day	25% 6% 14% 35% 15% 5%	4280
September	1st to 10th	Day	31% 5% 12% 25% 20% 7%	2280
	11th to 20th	Day	32% 7% 10% 25% 22% 2	2095
	21st to end	Day	30% 5% 10% 28% 24% 3	2085
October	1st to 10th	Day	31% 5% 11% 28% 23% 3	1900
	11th to 20th	Day	31% 3 7% 27% 26% 6%	1900
	21st to end	Day	39% 4 11% 21% 20% 5%	2010
November	1st to 10th	Day	31% 4 12% 29% 19% 5%	1851
	11th to 20th	Day	35% 4 10% 27% 21% 3	1658
	21st to end	Day	40% 4 9% 26% 20% 1	1520
December	1st to 10th	Day	37% 5% 13% 30% 13% 1	1520
	11th to 20th	Day	44% 5% 12% 25% 11% 2	1915
	21st to end	Day	60% 5% 10% 16% 7% 2	2952
January	1st to 10th	Night	47% 4 14% 21% 12% 1	4108
	11th to 20th	Night	50% 4 11% 22% 13% 1	4120
	21st to end	Night	52% 4 12% 20% 11% 1	4532
February	1st to 10th	Night	45% 5% 11% 21% 14% 3	2470
	11th to 20th	Night	41% 4 12% 23% 17% 3	2404
	21st to end	Night	40% 4 9% 22% 19% 7%	1843
March	1st to 10th	Night	36% 5% 10% 24% 21% 3	3419
	11th to 20th	Night	30% 4 9% 26% 26% 4	3480
	21st to end	Night	46% 7% 16% 22% 8% 1	3817
April	1st to 10th	Night	34% 6% 10% 24% 21% 4	1992
	11th to 20th	Night	38% 4 9% 28% 17% 3	1875
	21st to end	Night	42% 6% 12% 24% 15% 1	1753
May	1st to 10th	Night	42% 8% 15% 19% 15% 1	2850
	11th to 20th	Night	39% 7% 12% 27% 14% 1	2824
	21st to end	Night	30% 6% 12% 30% 21% 1	3040
June	1st to 10th	Night	23% 9% 17% 32% 16% 3	1520
	11th to 20th	Night	25% 8% 14% 32% 19% 2	1520
	21st to end	Night	19% 6% 14% 34% 22% 4	1555
July	1st to 10th	Night	35% 5% 12% 24% 19% 4	2805
	11th to 20th	Night	19% 6% 14% 37% 22% 3	2796
	21st to end	Night	26% 7% 20% 31% 15% 1	2999
August	1st to 10th	Night	18% 7% 19% 28% 22% 6%	2826
	11th to 20th	Night	34% 5% 12% 29% 19% 2	2825
	21st to end	Night	24% 4 12% 38% 17% 4	3377
September	1st to 10th	Night	29% 5% 9% 27% 21% 9%	1900
	11th to 20th	Night	28% 6% 11% 26% 25% 4	2081
	21st to end	Night	27% 5% 8% 26% 29% 5%	2090
October	1st to 10th	Night	28% 5% 8% 25% 27% 6%	2266
	11th to 20th	Night	30% 4 7% 27% 24% 9%	2280
	21st to end	Night	37% 4 8% 22% 25% 4	2413
November	1st to 10th	Night	27% 3 12% 27% 24% 6%	2224
	11th to 20th	Night	30% 4 10% 27% 24% 4	2518
	21st to end	Night	36% 3 10% 29% 19% 3	2660
December	1st to 10th	Night	38% 6% 12% 27% 16% 1	2660
	11th to 20th	Night	39% 4 11% 27% 17% 1	3281
	21st to end	Night	60% 4 7% 18% 9% 2	4710

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	22% 14% 35% 24% 5%	270
	11th to 20th	Day	24% 18% 37% 19% 3	270
	21st to end	Day	15% 13% 45% 25% 3	297
February	1st to 10th	Day	24% 18% 38% 17% 3 1	270
	11th to 20th	Day	19% 17% 42% 16% 5%	270
	21st to end	Day	16% 24% 44% 14% 3	225
March	1st to 10th	Day	15% 17% 47% 19% 3	270
	11th to 20th	Day	26% 15% 32% 23% 3 1	270
	21st to end	Day	29% 23% 30% 15% 3 1	297
April	1st to 10th	Day	20% 16% 38% 19% 7%	366
	11th to 20th	Day	17% 17% 38% 22% 5% 1	452
	21st to end	Day	22% 16% 33% 20% 8%	602
May	1st to 10th	Day	18% 14% 38% 20% 9% 1	653
	11th to 20th	Day	19% 9% 29% 27% 13% 2	675
	21st to end	Day	17% 9% 28% 26% 16% 4	734
June	1st to 10th	Day	6% 4 21% 35% 27% 7%	680
	11th to 20th	Day	8% 4 28% 36% 20% 5%	680
	21st to end	Day	6% 6% 34% 35% 17% 2	680
July	1st to 10th	Day	10% 3 16% 31% 30% 11%	671
	11th to 20th	Day	4 3 19% 39% 28% 7%	668
	21st to end	Day	8% 2 17% 37% 29% 8%	739
August	1st to 10th	Day	7% 2 17% 39% 30% 5%	676
	11th to 20th	Day	9% 3 16% 40% 25% 6%	665
	21st to end	Day	8% 2 15% 30% 35% 10%	601
September	1st to 10th	Day	14% 1 16% 34% 29% 6%	490
	11th to 20th	Day	5% 3 21% 38% 27% 6%	305
	21st to end	Day	11% 7% 26% 36% 15% 4	300
October	1st to 10th	Day	13% 5% 30% 26% 19% 7%	300
	11th to 20th	Day	10% 17% 41% 22% 9% 1	300
	21st to end	Day	22% 14% 37% 20% 6% 1	306
November	1st to 10th	Day	16% 10% 36% 29% 7% 3	270
	11th to 20th	Day	15% 15% 35% 25% 9% 1	270
	21st to end	Day	21% 11% 39% 20% 8%	270
December	1st to 10th	Day	9% 16% 41% 27% 5% 3	270
	11th to 20th	Day	20% 14% 37% 21% 7% 1	270
	21st to end	Day	19% 24% 38% 18% 1	297
January	1st to 10th	Night	13% 13% 39% 29% 6%	950
	11th to 20th	Night	15% 13% 41% 26% 4 1	950
	21st to end	Night	14% 12% 42% 28% 3	1045
February	1st to 10th	Night	17% 13% 43% 25% 3	950
	11th to 20th	Night	17% 14% 39% 28% 3	929
	21st to end	Night	18% 13% 45% 20% 4 1	587
March	1st to 10th	Night	14% 13% 45% 23% 5%	570
	11th to 20th	Night	20% 11% 36% 28% 5%	570
	21st to end	Night	25% 11% 37% 22% 4	627
April	1st to 10th	Night	13% 14% 42% 26% 5%	570
	11th to 20th	Night	19% 13% 34% 29% 5%	563
	21st to end	Night	18% 10% 39% 26% 6% 1	570
May	1st to 10th	Night	17% 8% 36% 31% 7% 1	570
	11th to 20th	Night	15% 6% 30% 36% 13%	561
	21st to end	Night	11% 6% 31% 34% 16% 2	617
June	1st to 10th	Night	5% 4 22% 46% 21% 2	570
	11th to 20th	Night	5% 4 28% 46% 18% 1	570
	21st to end	Night	5% 3 33% 46% 13% 1	570
July	1st to 10th	Night	7% 2 14% 45% 29% 3	555
	11th to 20th	Night	3 1 18% 47% 29% 2	552
	21st to end	Night	7% 2 14% 47% 29% 1	624
August	1st to 10th	Night	4 1 16% 48% 30% 1	567
	11th to 20th	Night	8% 3 13% 46% 28% 2	564
	21st to end	Night	6% 1 15% 42% 33% 3	627
September	1st to 10th	Night	10% 3 19% 42% 23% 3	570
	11th to 20th	Night	9% 3 20% 40% 24% 3	570
	21st to end	Night	8% 5% 23% 45% 17% 2	570
October	1st to 10th	Night	12% 5% 28% 35% 19% 2	746
	11th to 20th	Night	15% 8% 40% 30% 7% 1	760
	21st to end	Night	20% 10% 35% 27% 8%	805
November	1st to 10th	Night	11% 9% 37% 32% 10% 1	744
	11th to 20th	Night	12% 14% 38% 28% 8%	950
	21st to end	Night	18% 12% 35% 31% 5%	950
December	1st to 10th	Night	15% 11% 39% 27% 6% 1	950
	11th to 20th	Night	18% 10% 41% 27% 5%	950
	21st to end	Night	19% 16% 38% 24% 4	1045

Page generated at 2024-10-21 01:20:03. Version ac07

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