Emerald Beach
Clear Sky Chart
History

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

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	9% 5% 2 5% 4 4 5% 4 7% 9% 44%	100731
	Night	10% 6% 2 6% 4 4 4 4 6% 9% 46%	98414
Transparency	Day	18% 48% 10% 10% 9% 4	104660
	Night	18% 48% 9% 10% 10% 4	102623
Seeing	Day	10% 5% 18% 26% 27% 14%	14639
	Night	11% 5% 19% 27% 28% 10%	24562

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	13% 5% 2 5% 4 5% 4 4 6% 7% 45%	2909
	11th to 20th	Day	10% 6% 2 4 4 3 4 4 6% 8% 50%	3160
	21st to end	Day	22% 9% 2 6% 4 3 4 3 5% 7% 36%	3476
February	1st to 10th	Day	15% 9% 2 6% 4 4 4 3 4 6% 43%	1900
	11th to 20th	Day	13% 7% 2 5% 4 4 4 3 5% 7% 45%	1848
	21st to end	Day	13% 7% 3 5% 5% 5% 4 4 6% 7% 40%	1570
March	1st to 10th	Day	18% 10% 3 7% 4 3 4 3 5% 6% 36%	3120
	11th to 20th	Day	9% 6% 2 6% 5% 4 6% 4 6% 9% 43%	3343
	21st to end	Day	14% 6% 2 6% 4 4 4 4 5% 6% 45%	3991
April	1st to 10th	Day	11% 6% 3 5% 4 4 4 3 6% 7% 48%	2280
	11th to 20th	Day	10% 6% 2 5% 4 6% 4 4 5% 7% 48%	2254
	21st to end	Day	7% 4 1 4 4 2 4 4 6% 7% 58%	2280
May	1st to 10th	Day	7% 4 2 5% 5% 4 5% 4 7% 9% 47%	3815
	11th to 20th	Day	14% 5% 2 6% 4 3 4 4 6% 8% 46%	4081
	21st to end	Day	4 3 2 4 3 4 5% 4 7% 12% 53%	4476
June	1st to 10th	Day	7% 5% 3 6% 5% 6% 6% 6% 9% 11% 37%	2470
	11th to 20th	Day	5% 4 1 4 4 5% 6% 7% 10% 14% 40%	2470
	21st to end	Day	6% 5% 2 6% 6% 6% 6% 6% 8% 12% 37%	2470
July	1st to 10th	Day	7% 4 2 6% 5% 6% 6% 6% 10% 14% 33%	4120
	11th to 20th	Day	4 4 1 6% 6% 6% 6% 6% 10% 12% 39%	4007
	21st to end	Day	4 3 1 6% 5% 7% 8% 8% 12% 16% 30%	4118
August	1st to 10th	Day	5% 3 1 4 4 4 5% 5% 9% 14% 48%	3785
	11th to 20th	Day	5% 3 1 5% 4 4 5% 5% 8% 12% 48%	3729
	21st to end	Day	6% 4 2 5% 4 5% 6% 6% 9% 12% 41%	4180
September	1st to 10th	Day	9% 6% 2 6% 4 4 6% 5% 8% 10% 40%	2213
	11th to 20th	Day	11% 6% 2 6% 4 4 6% 4 8% 9% 39%	2090
	21st to end	Day	6% 4 2 5% 3 4 4 5% 7% 9% 52%	2090
October	1st to 10th	Day	7% 5% 2 4 3 4 4 3 6% 8% 55%	2090
	11th to 20th	Day	8% 3 2 4 3 2 3 2 4 6% 63%	2090
	21st to end	Day	8% 4 2 5% 4 3 4 2 4 6% 56%	2128
November	1st to 10th	Day	7% 6% 2 4 3 3 3 4 5% 6% 57%	1762
	11th to 20th	Day	9% 5% 2 4 4 3 3 3 5% 7% 54%	1719
	21st to end	Day	10% 5% 2 6% 4 4 4 4 7% 8% 48%	1710
December	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 8% 46%	1710
	11th to 20th	Day	13% 8% 3 6% 5% 4 4 3 5% 5% 43%	2153
	21st to end	Day	15% 10% 4 7% 4 3 3 3 4 5% 42%	3124
January	1st to 10th	Night	15% 7% 2 6% 4 4 4 4 5% 6% 43%	4031
	11th to 20th	Night	12% 6% 2 6% 3 3 3 4 5% 7% 48%	3800
	21st to end	Night	20% 9% 3 5% 4 4 4 3 5% 5% 39%	4180
February	1st to 10th	Night	14% 8% 3 6% 4 4 4 3 4 5% 46%	2280
	11th to 20th	Night	15% 8% 3 5% 3 3 3 3 5% 6% 46%	2218
	21st to end	Night	14% 8% 3 6% 4 4 4 4 5% 5% 44%	1884
March	1st to 10th	Night	19% 11% 4 6% 4 4 4 3 5% 6% 34%	3733
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 4 7% 9% 45%	3615
	21st to end	Night	13% 6% 2 7% 4 4 4 3 5% 7% 45%	3668
April	1st to 10th	Night	10% 7% 3 6% 5% 4 4 3 6% 7% 46%	1900
	11th to 20th	Night	11% 6% 2 5% 4 4 3 4 7% 7% 47%	1875
	21st to end	Night	5% 3 1 4 3 3 3 4 5% 7% 61%	1900
May	1st to 10th	Night	7% 6% 2 5% 4 4 5% 4 7% 9% 48%	3076
	11th to 20th	Night	9% 6% 2 6% 4 5% 4 4 6% 8% 45%	2812
	21st to end	Night	4 3 1 4 3 4 4 4 7% 13% 54%	3079
June	1st to 10th	Night	6% 6% 3 7% 5% 5% 5% 4 9% 10% 41%	1710
	11th to 20th	Night	4 3 2 5% 5% 4 6% 4 10% 12% 47%	1710
	21st to end	Night	5% 5% 2 5% 4 5% 5% 6% 9% 13% 41%	1710
July	1st to 10th	Night	5% 4 2 7% 5% 5% 7% 6% 11% 17% 33%	2840
	11th to 20th	Night	2 2 1 4 4 3 5% 5% 8% 13% 52%	2933
	21st to end	Night	3 2 1 5% 5% 6% 8% 7% 13% 16% 34%	3435
August	1st to 10th	Night	3 2 1 5% 4 5% 6% 4 8% 13% 49%	3144
	11th to 20th	Night	4 3 1 4 4 4 4 4 8% 12% 52%	3100
	21st to end	Night	5% 4 2 7% 5% 6% 6% 5% 10% 12% 38%	3476
September	1st to 10th	Night	10% 5% 1 7% 6% 5% 5% 6% 7% 13% 36%	1947
	11th to 20th	Night	10% 6% 2 6% 5% 6% 5% 4 6% 8% 41%	2090
	21st to end	Night	8% 5% 1 5% 3 4 4 4 5% 9% 50%	2090
October	1st to 10th	Night	7% 5% 2 5% 4 4 3 4 6% 8% 52%	2090
	11th to 20th	Night	5% 4 2 4 2 3 3 3 5% 6% 62%	2090
	21st to end	Night	9% 5% 3 5% 4 4 4 3 5% 6% 54%	2464
November	1st to 10th	Night	8% 5% 1 4 4 2 4 4 5% 7% 56%	2536
	11th to 20th	Night	9% 5% 2 6% 3 3 4 3 5% 7% 53%	2484
	21st to end	Night	11% 5% 2 6% 4 4 4 3 6% 7% 48%	2470
December	1st to 10th	Night	12% 6% 3 6% 4 4 4 4 5% 7% 46%	2470
	11th to 20th	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	3042
	21st to end	Night	15% 10% 3 7% 5% 4 4 3 4 6% 41%	4532

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	23% 40% 6% 11% 13% 8%	2910
	11th to 20th	Day	17% 40% 5% 10% 20% 8%	3160
	21st to end	Day	32% 40% 2 10% 12% 5%	3476
February	1st to 10th	Day	17% 65% 3 5% 7% 3	1900
	11th to 20th	Day	14% 64% 3 8% 8% 3	1858
	21st to end	Day	15% 67% 4 5% 4 5%	1570
March	1st to 10th	Day	34% 43% 6% 10% 5% 2	3120
	11th to 20th	Day	24% 44% 8% 11% 12% 2	3343
	21st to end	Day	25% 42% 7% 9% 10% 7%	3991
April	1st to 10th	Day	13% 65% 4 6% 8% 4	2280
	11th to 20th	Day	14% 66% 4 8% 6% 3	2254
	21st to end	Day	11% 65% 4 8% 8% 4	2280
May	1st to 10th	Day	17% 46% 12% 14% 8% 3	3850
	11th to 20th	Day	26% 41% 6% 16% 10% 1	4085
	21st to end	Day	13% 44% 13% 23% 7% 1	4489
June	1st to 10th	Day	16% 68% 6% 8% 2	2470
	11th to 20th	Day	15% 67% 7% 7% 4	2470
	21st to end	Day	14% 66% 10% 6% 4	2470
July	1st to 10th	Day	20% 44% 29% 6% 1	4055
	11th to 20th	Day	19% 43% 33% 5%	3938
	21st to end	Day	23% 47% 21% 8% 2	3987
August	1st to 10th	Day	13% 39% 13% 23% 10% 2	3773
	11th to 20th	Day	12% 40% 16% 20% 11% 1	3765
	21st to end	Day	18% 43% 22% 11% 6%	4179
September	1st to 10th	Day	17% 63% 9% 5% 4 3	2213
	11th to 20th	Day	14% 61% 8% 9% 6% 2	2090
	21st to end	Day	13% 61% 5% 11% 7% 1	2090
October	1st to 10th	Day	22% 37% 5% 7% 10% 20%	3480
	11th to 20th	Day	6% 36% 3 14% 14% 27%	3458
	21st to end	Day	10% 37% 3 9% 29% 12%	3481
November	1st to 10th	Day	19% 56% 5% 8% 8% 5%	1762
	11th to 20th	Day	15% 59% 3 7% 11% 4	1719
	21st to end	Day	14% 60% 3 9% 9% 4	1710
December	1st to 10th	Day	17% 60% 6% 6% 7% 3	1710
	11th to 20th	Day	21% 48% 2 8% 14% 8%	2150
	21st to end	Day	30% 38% 5% 11% 14% 2	3124
January	1st to 10th	Night	28% 37% 5% 6% 14% 11%	4031
	11th to 20th	Night	24% 38% 3 9% 22% 4	3800
	21st to end	Night	29% 40% 5% 11% 12% 4	4180
February	1st to 10th	Night	15% 65% 2 6% 8% 3	2280
	11th to 20th	Night	14% 64% 3 7% 9% 4	2219
	21st to end	Night	15% 66% 5% 4 6% 5%	1884
March	1st to 10th	Night	38% 43% 7% 8% 4 1	3733
	11th to 20th	Night	21% 43% 9% 10% 12% 4	3615
	21st to end	Night	25% 42% 6% 12% 9% 6%	3668
April	1st to 10th	Night	14% 65% 4 4 7% 6%	1900
	11th to 20th	Night	13% 66% 3 8% 7% 4	1875
	21st to end	Night	8% 66% 4 11% 8% 3	1900
May	1st to 10th	Night	17% 45% 13% 12% 9% 3	3106
	11th to 20th	Night	24% 43% 8% 15% 9% 1	2813
	21st to end	Night	11% 43% 12% 26% 8% 1	3087
June	1st to 10th	Night	13% 68% 8% 9% 1 1	1710
	11th to 20th	Night	10% 68% 8% 8% 5% 1	1710
	21st to end	Night	11% 66% 13% 6% 4	1710
July	1st to 10th	Night	20% 43% 30% 7% 1	2795
	11th to 20th	Night	10% 43% 41% 5% 1	2879
	21st to end	Night	18% 51% 20% 9% 2	3325
August	1st to 10th	Night	14% 41% 16% 17% 11% 1	3132
	11th to 20th	Night	10% 41% 17% 24% 8%	3130
	21st to end	Night	19% 43% 19% 12% 7% 1	3476
September	1st to 10th	Night	14% 63% 10% 6% 4 2	1947
	11th to 20th	Night	13% 62% 8% 8% 7% 2	2090
	21st to end	Night	11% 62% 6% 12% 7% 2	2090
October	1st to 10th	Night	24% 37% 5% 7% 10% 16%	3480
	11th to 20th	Night	5% 36% 2 13% 19% 24%	3461
	21st to end	Night	9% 36% 3 8% 34% 9%	4061
November	1st to 10th	Night	17% 56% 5% 8% 9% 4	2536
	11th to 20th	Night	16% 60% 2 7% 12% 4	2484
	21st to end	Night	13% 60% 4 9% 9% 5%	2470
December	1st to 10th	Night	19% 60% 5% 7% 7% 2	2470
	11th to 20th	Night	19% 49% 4 5% 14% 9%	3044
	21st to end	Night	32% 39% 4 11% 13% 1	4532

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	16% 11% 38% 26% 9% 1	270
	11th to 20th	Day	9% 12% 34% 31% 14% 1	270
	21st to end	Day	22% 13% 40% 19% 6%	297
February	1st to 10th	Day	17% 13% 36% 26% 9%	270
	11th to 20th	Day	16% 11% 36% 29% 8%	270
	21st to end	Day	8% 12% 44% 30% 5%	225
March	1st to 10th	Day	11% 10% 40% 32% 6%	270
	11th to 20th	Day	13% 10% 32% 32% 11% 1	375
	21st to end	Day	13% 10% 30% 32% 13% 1	506
April	1st to 10th	Day	14% 8% 31% 31% 13% 2	460
	11th to 20th	Day	13% 10% 29% 29% 18% 2	452
	21st to end	Day	7% 3 27% 36% 23% 4	460
May	1st to 10th	Day	6% 5% 23% 34% 26% 6%	463
	11th to 20th	Day	8% 3 13% 38% 27% 12%	487
	21st to end	Day	6% 2 8% 34% 34% 16%	529
June	1st to 10th	Day	9% 2 10% 30% 35% 14%	490
	11th to 20th	Day	7% 2 9% 23% 37% 23%	490
	21st to end	Day	8% 1 5% 20% 38% 27%	490
July	1st to 10th	Day	7% 2 4 12% 40% 34%	485
	11th to 20th	Day	7% 1 3 9% 39% 41%	484
	21st to end	Day	5% 4 14% 41% 36%	532
August	1st to 10th	Day	7% 1 2 12% 39% 39%	486
	11th to 20th	Day	8% 2 2 11% 40% 38%	479
	21st to end	Day	7% 2 6% 18% 39% 27%	539
September	1st to 10th	Day	13% 2 5% 16% 38% 26%	490
	11th to 20th	Day	13% 2 7% 21% 40% 17%	490
	21st to end	Day	8% 1 9% 26% 38% 17%	490
October	1st to 10th	Day	9% 2 17% 37% 28% 8%	490
	11th to 20th	Day	7% 3 16% 29% 35% 10%	490
	21st to end	Day	9% 6% 17% 33% 29% 6%	430
November	1st to 10th	Day	11% 3 15% 32% 33% 6%	300
	11th to 20th	Day	14% 5% 23% 34% 21% 3	273
	21st to end	Day	11% 6% 26% 37% 16% 4	270
December	1st to 10th	Day	15% 9% 29% 30% 14% 3	270
	11th to 20th	Day	18% 11% 30% 32% 9% 1	270
	21st to end	Day	21% 7% 29% 30% 11% 1	297
January	1st to 10th	Night	15% 13% 33% 29% 10% 1	760
	11th to 20th	Night	13% 12% 27% 33% 13% 1	760
	21st to end	Night	19% 11% 35% 28% 7%	836
February	1st to 10th	Night	16% 11% 29% 33% 11% 1	760
	11th to 20th	Night	17% 13% 31% 27% 13%	743
	21st to end	Night	15% 10% 31% 34% 9%	628
March	1st to 10th	Night	14% 7% 30% 35% 14% 1	760
	11th to 20th	Night	11% 7% 28% 33% 18% 3	760
	21st to end	Night	11% 7% 26% 34% 21% 1	751
April	1st to 10th	Night	13% 8% 25% 34% 19% 2	570
	11th to 20th	Night	12% 5% 24% 31% 25% 3	563
	21st to end	Night	7% 3 17% 36% 32% 5%	570
May	1st to 10th	Night	7% 3 15% 32% 33% 9%	570
	11th to 20th	Night	7% 2 13% 32% 36% 11%	561
	21st to end	Night	6% 1 8% 23% 48% 14%	617
June	1st to 10th	Night	8% 1 6% 24% 47% 14%	570
	11th to 20th	Night	3 2 5% 21% 48% 22%	570
	21st to end	Night	8% 1 4 15% 48% 25%	570
July	1st to 10th	Night	6% 1 2 12% 46% 33%	555
	11th to 20th	Night	5% 1 1 7% 40% 45%	552
	21st to end	Night	4 2 12% 47% 34%	624
August	1st to 10th	Night	3 2 11% 41% 43%	567
	11th to 20th	Night	9% 2 9% 45% 35%	564
	21st to end	Night	8% 2 6% 16% 43% 24%	627
September	1st to 10th	Night	10% 2 4 18% 42% 24%	617
	11th to 20th	Night	11% 2 8% 20% 45% 13%	760
	21st to end	Night	10% 2 9% 26% 41% 12%	760
October	1st to 10th	Night	8% 2 16% 36% 32% 6%	760
	11th to 20th	Night	6% 4 18% 32% 31% 9%	760
	21st to end	Night	11% 5% 17% 35% 29% 3	836
November	1st to 10th	Night	10% 5% 19% 38% 24% 3	780
	11th to 20th	Night	12% 7% 26% 33% 20% 1	765
	21st to end	Night	12% 6% 28% 32% 20% 2	760
December	1st to 10th	Night	13% 8% 28% 29% 19% 3	760
	11th to 20th	Night	16% 8% 31% 28% 17% 1	760
	21st to end	Night	20% 10% 28% 28% 13% 1	836

Page generated at 2024-11-08 22:45:37. Version ac07

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