Turtle Beach Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Turtle Beach Observatory clear sky chart from 2005-11-06 to 2025-03-27.

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	13% 7% 3 6% 5% 4 4 4 5% 7% 42%	109434
	Night	13% 7% 2 5% 4 4 4 3 5% 7% 46%	110094
Transparency	Day	23% 44% 6% 12% 12% 4	113079
	Night	22% 42% 6% 12% 13% 5%	114589
Seeing	Day	14% 8% 21% 24% 24% 9%	15455
	Night	15% 8% 25% 31% 18% 3	25408

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	19% 10% 3 5% 3 3 3 2 3 4 44%	4077
	11th to 20th	Day	16% 5% 2 4 3 3 3 3 4 6% 51%	4080
	21st to end	Day	23% 11% 3 5% 3 3 2 2 3 4 41%	4488
February	1st to 10th	Day	19% 10% 3 6% 4 4 3 3 4 5% 38%	1800
	11th to 20th	Day	22% 9% 3 6% 4 3 3 2 3 4 40%	1960
	21st to end	Day	20% 9% 2 7% 5% 4 3 3 4 5% 38%	1815
March	1st to 10th	Day	20% 12% 4 9% 5% 4 4 3 4 5% 31%	3546
	11th to 20th	Day	17% 8% 3 7% 4 4 4 4 6% 8% 35%	3590
	21st to end	Day	16% 10% 4 7% 4 4 3 3 4 4 42%	3880
April	1st to 10th	Day	12% 7% 3 7% 4 4 5% 4 6% 6% 41%	2180
	11th to 20th	Day	16% 7% 3 6% 4 4 4 3 5% 8% 39%	2254
	21st to end	Day	10% 5% 3 6% 5% 5% 5% 4 5% 7% 44%	2280
May	1st to 10th	Day	16% 8% 3 8% 6% 5% 5% 4 6% 7% 32%	3765
	11th to 20th	Day	12% 6% 3 6% 4 4 4 3 5% 7% 45%	3948
	21st to end	Day	9% 6% 2 7% 6% 6% 6% 5% 7% 10% 36%	4477
June	1st to 10th	Day	7% 5% 2 7% 6% 6% 6% 5% 8% 10% 38%	2470
	11th to 20th	Day	5% 5% 2 6% 6% 6% 6% 5% 7% 11% 41%	2470
	21st to end	Day	6% 5% 2 6% 6% 6% 6% 5% 8% 10% 38%	2470
July	1st to 10th	Day	8% 6% 2 8% 6% 6% 6% 6% 8% 12% 34%	4120
	11th to 20th	Day	6% 6% 3 8% 7% 6% 7% 6% 8% 10% 33%	4120
	21st to end	Day	15% 9% 3 8% 6% 5% 5% 5% 6% 8% 29%	4465
August	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 9% 63%	4104
	11th to 20th	Day	3 3 1 4 4 3 4 4 7% 10% 56%	3729
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 7% 9% 39%	4180
September	1st to 10th	Day	9% 5% 2 7% 6% 5% 5% 5% 5% 8% 43%	2280
	11th to 20th	Day	13% 6% 3 5% 5% 5% 5% 4 7% 7% 41%	2127
	21st to end	Day	9% 4 1 5% 4 4 4 4 5% 8% 52%	2048
October	1st to 10th	Day	6% 4 1 5% 3 4 4 3 4 5% 62%	1900
	11th to 20th	Day	11% 5% 2 4 3 3 3 2 4 6% 56%	1900
	21st to end	Day	14% 6% 2 4 3 3 4 2 3 6% 53%	2090
November	1st to 10th	Day	12% 5% 2 6% 4 4 4 3 5% 6% 49%	1958
	11th to 20th	Day	11% 6% 2 7% 4 3 3 2 5% 5% 53%	2000
	21st to end	Day	16% 7% 2 7% 4 4 4 3 4 5% 45%	2000
December	1st to 10th	Day	19% 9% 2 5% 3 3 4 2 3 5% 45%	2984
	11th to 20th	Day	16% 11% 3 8% 5% 3 4 2 5% 5% 39%	3391
	21st to end	Day	15% 9% 3 6% 3 3 3 3 4 5% 46%	4488
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 4 4 52%	5888
	11th to 20th	Night	16% 8% 2 5% 3 2 3 2 3 4 51%	5900
	21st to end	Night	25% 11% 2 6% 4 3 3 2 3 4 37%	6490
February	1st to 10th	Night	17% 8% 2 6% 4 3 4 3 4 6% 42%	2600
	11th to 20th	Night	21% 9% 2 5% 4 2 3 3 4 5% 42%	2340
	21st to end	Night	21% 8% 3 6% 4 3 3 2 4 4 41%	1815
March	1st to 10th	Night	23% 11% 2 6% 4 4 4 3 5% 6% 33%	3529
	11th to 20th	Night	19% 8% 2 7% 5% 5% 4 3 5% 6% 36%	3590
	21st to end	Night	13% 7% 3 7% 5% 4 4 3 6% 6% 43%	3889
April	1st to 10th	Night	12% 6% 2 5% 5% 4 5% 4 6% 7% 45%	1999
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 4 7% 44%	1875
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 5% 5% 50%	1900
May	1st to 10th	Night	15% 9% 3 7% 5% 4 4 4 6% 8% 35%	3130
	11th to 20th	Night	15% 6% 2 7% 4 4 4 3 5% 6% 43%	2948
	21st to end	Night	10% 6% 2 7% 6% 4 5% 4 6% 11% 38%	3090
June	1st to 10th	Night	6% 4 2 5% 5% 5% 5% 4 7% 10% 47%	1710
	11th to 20th	Night	4 3 1 4 3 3 3 5% 6% 11% 57%	1710
	21st to end	Night	6% 4 1 3 3 4 4 5% 9% 11% 49%	1710
July	1st to 10th	Night	6% 6% 3 6% 6% 4 5% 4 8% 12% 40%	2850
	11th to 20th	Night	4 4 2 7% 5% 6% 7% 6% 8% 12% 39%	2850
	21st to end	Night	13% 9% 3 7% 5% 3 5% 4 6% 10% 36%	3098
August	1st to 10th	Night	1 2 1 3 2 2 2 2 5% 11% 70%	2836
	11th to 20th	Night	3 2 1 3 3 4 4 5% 8% 13% 56%	3098
	21st to end	Night	7% 5% 3 7% 5% 6% 5% 4 7% 8% 43%	3476
September	1st to 10th	Night	7% 5% 2 6% 5% 4 5% 4 6% 8% 49%	1900
	11th to 20th	Night	11% 5% 2 6% 4 5% 5% 4 5% 8% 45%	2047
	21st to end	Night	8% 5% 2 4 3 3 3 3 5% 6% 58%	2110
October	1st to 10th	Night	6% 3 1 4 3 4 4 3 5% 7% 60%	2280
	11th to 20th	Night	9% 5% 2 3 3 3 3 3 4 6% 59%	2280
	21st to end	Night	12% 5% 2 4 3 2 3 2 4 4 59%	2508
November	1st to 10th	Night	13% 5% 2 5% 4 3 3 3 4 5% 54%	2340
	11th to 20th	Night	11% 5% 2 4 5% 4 3 3 4 6% 53%	2400
	21st to end	Night	14% 7% 3 6% 4 4 3 3 5% 6% 46%	2400
December	1st to 10th	Night	21% 8% 3 5% 4 4 3 2 4 5% 41%	4202
	11th to 20th	Night	15% 10% 3 6% 4 4 3 3 4 5% 45%	4816
	21st to end	Night	14% 9% 2 5% 3 3 3 3 4 5% 49%	6490

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	35% 27% 3 20% 14% 2	4078
	11th to 20th	Day	25% 26% 3 17% 20% 9%	4080
	21st to end	Day	37% 28% 2 9% 15% 10%	4488
February	1st to 10th	Day	20% 61% 3 5% 7% 4	1800
	11th to 20th	Day	21% 60% 4 8% 6% 2	1969
	21st to end	Day	23% 62% 2 3 6% 5%	1815
March	1st to 10th	Day	39% 41% 4 6% 8% 1	3546
	11th to 20th	Day	29% 41% 5% 15% 8% 3	3590
	21st to end	Day	30% 40% 5% 11% 14% 1	3880
April	1st to 10th	Day	16% 65% 3 6% 7% 3	2180
	11th to 20th	Day	18% 66% 4 5% 4 3	2254
	21st to end	Day	12% 66% 4 8% 8% 2	2280
May	1st to 10th	Day	31% 44% 6% 12% 5% 2	3800
	11th to 20th	Day	23% 41% 5% 11% 17% 1	3952
	21st to end	Day	23% 44% 10% 15% 6% 1	4489
June	1st to 10th	Day	12% 65% 5% 8% 9%	2470
	11th to 20th	Day	15% 66% 7% 6% 4 1	2470
	21st to end	Day	15% 64% 7% 10% 4	2470
July	1st to 10th	Day	25% 41% 18% 14% 2	4056
	11th to 20th	Day	28% 39% 11% 16% 6%	4051
	21st to end	Day	35% 37% 8% 15% 5%	4325
August	1st to 10th	Day	6% 37% 9% 23% 24% 1	4090
	11th to 20th	Day	9% 38% 16% 31% 5% 1	3765
	21st to end	Day	24% 39% 10% 11% 15%	4179
September	1st to 10th	Day	12% 62% 8% 8% 8% 3	2280
	11th to 20th	Day	14% 61% 6% 9% 8% 2	2127
	21st to end	Day	13% 61% 6% 11% 6% 2	2048
October	1st to 10th	Day	7% 37% 4 7% 15% 31%	3160
	11th to 20th	Day	8% 36% 4 11% 22% 20%	3140
	21st to end	Day	16% 36% 2 7% 31% 8%	3428
November	1st to 10th	Day	20% 57% 5% 6% 8% 3	1958
	11th to 20th	Day	17% 57% 3 7% 11% 6%	2000
	21st to end	Day	17% 57% 3 10% 10% 3	2000
December	1st to 10th	Day	29% 35% 3 10% 19% 3	2984
	11th to 20th	Day	31% 32% 3 9% 16% 9%	3389
	21st to end	Day	32% 27% 4 10% 24% 3	4488
January	1st to 10th	Night	27% 27% 4 20% 20% 2	5888
	11th to 20th	Night	29% 26% 3 14% 23% 6%	5900
	21st to end	Night	41% 28% 3 9% 11% 8%	6490
February	1st to 10th	Night	18% 62% 2 7% 7% 4	2600
	11th to 20th	Night	18% 60% 4 8% 7% 3	2341
	21st to end	Night	21% 61% 2 5% 5% 6%	1815
March	1st to 10th	Night	38% 41% 4 8% 8% 2	3529
	11th to 20th	Night	32% 40% 5% 9% 11% 3	3590
	21st to end	Night	25% 42% 5% 10% 16% 2	3889
April	1st to 10th	Night	14% 65% 3 6% 7% 5%	1999
	11th to 20th	Night	16% 67% 3 6% 5% 3	1875
	21st to end	Night	12% 66% 3 7% 9% 3	1900
May	1st to 10th	Night	29% 44% 6% 11% 7% 3	3160
	11th to 20th	Night	27% 42% 5% 10% 14% 2	2949
	21st to end	Night	25% 45% 11% 14% 5% 1	3099
June	1st to 10th	Night	9% 66% 5% 10% 9%	1710
	11th to 20th	Night	9% 67% 9% 10% 4 1	1710
	21st to end	Night	11% 65% 8% 13% 3	1710
July	1st to 10th	Night	21% 41% 21% 14% 3	2805
	11th to 20th	Night	23% 41% 14% 18% 4	2796
	21st to end	Night	32% 37% 11% 14% 5% 1	2999
August	1st to 10th	Night	5% 37% 9% 22% 26% 1	2826
	11th to 20th	Night	7% 39% 19% 30% 4 1	3128
	21st to end	Night	24% 40% 9% 12% 13% 1	3476
September	1st to 10th	Night	11% 62% 7% 10% 7% 4	1900
	11th to 20th	Night	13% 61% 6% 10% 8% 2	2047
	21st to end	Night	12% 62% 6% 11% 7% 2	2110
October	1st to 10th	Night	7% 38% 4 9% 11% 32%	3800
	11th to 20th	Night	5% 36% 2 14% 21% 21%	3779
	21st to end	Night	13% 37% 2 9% 28% 11%	4120
November	1st to 10th	Night	21% 56% 5% 6% 7% 4	2340
	11th to 20th	Night	17% 57% 3 7% 9% 6%	2400
	21st to end	Night	17% 56% 3 8% 11% 5%	2400
December	1st to 10th	Night	32% 35% 3 9% 19% 2	4202
	11th to 20th	Night	27% 32% 5% 9% 18% 8%	4817
	21st to end	Night	29% 27% 5% 12% 23% 5%	6490

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% 16% 39% 15% 5%	300
	11th to 20th	Day	24% 18% 32% 22% 4	300
	21st to end	Day	25% 22% 33% 18% 3	330
February	1st to 10th	Day	24% 15% 37% 20% 3 1	300
	11th to 20th	Day	34% 18% 31% 16% 1	300
	21st to end	Day	27% 26% 33% 10% 3	249
March	1st to 10th	Day	25% 18% 32% 18% 6%	300
	11th to 20th	Day	20% 24% 37% 16% 3	300
	21st to end	Day	17% 17% 42% 19% 5%	315
April	1st to 10th	Day	15% 18% 37% 23% 7%	360
	11th to 20th	Day	23% 16% 27% 23% 10% 2	452
	21st to end	Day	13% 13% 31% 30% 11% 2	460
May	1st to 10th	Day	16% 10% 34% 27% 12% 1	463
	11th to 20th	Day	13% 5% 23% 34% 20% 4	593
	21st to end	Day	9% 5% 25% 35% 19% 7%	734
June	1st to 10th	Day	8% 3 15% 31% 32% 11%	680
	11th to 20th	Day	8% 2 14% 34% 35% 8%	680
	21st to end	Day	9% 2 11% 25% 38% 15%	680
July	1st to 10th	Day	7% 2 7% 25% 43% 15%	671
	11th to 20th	Day	4 2 6% 23% 44% 21%	668
	21st to end	Day	9% 1 6% 25% 45% 15%	739
August	1st to 10th	Day	4 1 6% 19% 49% 21%	676
	11th to 20th	Day	5% 2 3 17% 49% 24%	479
	21st to end	Day	11% 3 7% 19% 32% 28%	539
September	1st to 10th	Day	9% 1 8% 19% 41% 21%	490
	11th to 20th	Day	10% 3 10% 23% 35% 20%	337
	21st to end	Day	13% 4 8% 25% 37% 13%	300
October	1st to 10th	Day	7% 3 19% 37% 26% 9%	300
	11th to 20th	Day	9% 6% 27% 30% 21% 7%	300
	21st to end	Day	20% 12% 22% 24% 16% 5%	330
November	1st to 10th	Day	16% 9% 25% 31% 17% 3	300
	11th to 20th	Day	13% 12% 32% 29% 11% 2	300
	21st to end	Day	19% 17% 34% 22% 6% 2	300
December	1st to 10th	Day	20% 9% 37% 21% 8% 4	300
	11th to 20th	Day	22% 13% 35% 24% 6%	300
	21st to end	Day	23% 15% 35% 22% 4 1	330
January	1st to 10th	Night	22% 12% 37% 24% 5%	1000
	11th to 20th	Night	23% 15% 31% 25% 7%	1000
	21st to end	Night	23% 12% 35% 27% 3	1100
February	1st to 10th	Night	22% 15% 36% 25% 3	1000
	11th to 20th	Night	26% 15% 33% 22% 4	785
	21st to end	Night	26% 16% 36% 21% 2	495
March	1st to 10th	Night	24% 11% 32% 28% 5%	600
	11th to 20th	Night	19% 14% 36% 26% 5% 1	600
	21st to end	Night	15% 11% 39% 28% 8%	647
April	1st to 10th	Night	14% 11% 41% 28% 6%	570
	11th to 20th	Night	17% 12% 36% 24% 12%	563
	21st to end	Night	13% 10% 37% 28% 11% 1	570
May	1st to 10th	Night	12% 9% 32% 35% 11% 1	570
	11th to 20th	Night	12% 5% 27% 35% 18% 3	561
	21st to end	Night	7% 3 25% 39% 20% 5%	617
June	1st to 10th	Night	6% 2 14% 39% 35% 4	570
	11th to 20th	Night	4 3 15% 48% 28% 3	570
	21st to end	Night	8% 1 10% 37% 36% 8%	570
July	1st to 10th	Night	4 3 7% 38% 41% 8%	555
	11th to 20th	Night	3 1 7% 35% 44% 10%	552
	21st to end	Night	5% 1 6% 37% 42% 8%	624
August	1st to 10th	Night	2 1 5% 35% 48% 8%	567
	11th to 20th	Night	5% 6% 33% 47% 9%	564
	21st to end	Night	10% 2 6% 29% 42% 12%	627
September	1st to 10th	Night	7% 2 5% 32% 44% 9%	570
	11th to 20th	Night	13% 1 10% 29% 39% 8%	570
	21st to end	Night	10% 2 12% 34% 35% 8%	590
October	1st to 10th	Night	7% 2 15% 38% 33% 5%	760
	11th to 20th	Night	11% 7% 21% 39% 19% 3	760
	21st to end	Night	15% 7% 23% 34% 19% 2	836
November	1st to 10th	Night	14% 5% 27% 32% 20% 1	780
	11th to 20th	Night	13% 9% 28% 35% 14%	800
	21st to end	Night	18% 10% 31% 29% 12% 1	800
December	1st to 10th	Night	22% 13% 28% 27% 9%	965
	11th to 20th	Night	24% 10% 31% 30% 5%	1000
	21st to end	Night	22% 12% 31% 29% 6%	1100

Page generated at 2025-03-24 08:04:26. Version ac07

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