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 2026-07-31.

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	12% 7% 2 6% 4 4 4 4 5% 7% 42%	137798
	Night	13% 7% 2 6% 4 4 4 3 5% 7% 45%	135496
Transparency	Day	26% 36% 8% 14% 12% 4	141404
	Night	26% 36% 7% 13% 13% 5%	139970
Seeing	Day	14% 8% 21% 25% 24% 9%	17370
	Night	15% 8% 25% 31% 18% 3	27093

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	18% 10% 3 6% 3 3 3 3 3 5% 43%	5289
	11th to 20th	Day	13% 5% 2 4 3 3 4 3 5% 7% 52%	5310
	21st to end	Day	25% 11% 3 6% 3 3 3 2 3 4 39%	5812
February	1st to 10th	Day	19% 10% 3 6% 4 4 3 3 4 5% 40%	1890
	11th to 20th	Day	21% 9% 3 6% 4 3 3 2 3 5% 39%	2061
	21st to end	Day	19% 9% 2 7% 4 4 3 3 4 5% 39%	1903
March	1st to 10th	Day	18% 12% 3 8% 4 4 3 3 3 5% 36%	5046
	11th to 20th	Day	13% 6% 2 6% 4 4 3 3 4 6% 49%	5090
	21st to end	Day	14% 10% 4 7% 4 4 4 3 4 6% 41%	5583
April	1st to 10th	Day	12% 7% 3 8% 5% 4 5% 4 6% 6% 40%	2410
	11th to 20th	Day	15% 6% 3 6% 5% 4 4 4 6% 8% 40%	2494
	21st to end	Day	11% 6% 3 6% 5% 6% 5% 4 5% 7% 42%	2520
May	1st to 10th	Day	21% 8% 3 7% 5% 4 4 4 5% 6% 32%	7021
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	7383
	21st to end	Day	10% 7% 3 7% 6% 5% 6% 5% 8% 10% 33%	8392
June	1st to 10th	Day	7% 5% 2 7% 6% 6% 7% 5% 8% 10% 37%	2730
	11th to 20th	Day	6% 5% 2 6% 6% 6% 6% 5% 7% 11% 40%	2730
	21st to end	Day	6% 5% 2 6% 6% 6% 7% 5% 8% 10% 39%	2730
July	1st to 10th	Day	7% 5% 2 7% 6% 6% 6% 6% 8% 12% 35%	6030
	11th to 20th	Day	5% 5% 2 7% 6% 5% 6% 5% 8% 11% 40%	6030
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 5% 7% 9% 37%	6553
August	1st to 10th	Day	2 2 1 3 3 3 4 4 6% 9% 63%	4234
	11th to 20th	Day	3 3 1 4 3 3 4 5% 7% 10% 56%	3849
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 7% 9% 39%	4312
September	1st to 10th	Day	8% 5% 2 7% 6% 5% 5% 5% 5% 8% 44%	2400
	11th to 20th	Day	12% 5% 2 5% 5% 5% 5% 4 7% 7% 41%	2239
	21st to end	Day	9% 4 1 5% 4 4 4 4 5% 8% 52%	2156
October	1st to 10th	Day	6% 4 1 5% 3 4 4 3 4 5% 63%	2000
	11th to 20th	Day	10% 5% 2 4 3 3 3 2 4 6% 57%	2000
	21st to end	Day	14% 5% 2 4 3 3 4 2 3 6% 53%	2200
November	1st to 10th	Day	11% 5% 2 6% 3 4 4 3 5% 6% 51%	2058
	11th to 20th	Day	11% 6% 2 6% 3 3 3 2 5% 5% 53%	2100
	21st to end	Day	16% 7% 2 7% 5% 4 4 3 4 5% 45%	2100
December	1st to 10th	Day	20% 9% 2 5% 3 3 4 2 3 5% 44%	3075
	11th to 20th	Day	16% 11% 3 8% 5% 4 4 2 5% 5% 39%	3481
	21st to end	Day	15% 9% 3 6% 4 3 3 3 4 5% 45%	4587
January	1st to 10th	Night	18% 6% 2 5% 3 3 3 3 4 5% 50%	7634
	11th to 20th	Night	13% 7% 2 5% 3 3 4 3 4 5% 52%	7680
	21st to end	Night	26% 10% 3 7% 4 3 3 2 3 4 34%	8402
February	1st to 10th	Night	17% 8% 2 6% 3 3 4 3 4 6% 43%	2730
	11th to 20th	Night	20% 9% 2 5% 4 2 3 3 4 5% 42%	2460
	21st to end	Night	21% 8% 3 6% 4 3 3 2 3 4 41%	1903
March	1st to 10th	Night	21% 10% 2 6% 3 3 4 3 4 5% 39%	5029
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 4 5% 46%	5090
	21st to end	Night	16% 8% 3 7% 4 4 4 3 4 5% 42%	5588
April	1st to 10th	Night	13% 7% 2 5% 5% 4 4 4 6% 7% 44%	2209
	11th to 20th	Night	14% 5% 2 6% 4 4 4 4 4 7% 45%	2075
	21st to end	Night	12% 6% 3 6% 4 4 5% 4 5% 5% 47%	2100
May	1st to 10th	Night	20% 10% 3 8% 4 4 4 3 5% 7% 32%	5832
	11th to 20th	Night	13% 7% 3 8% 5% 5% 5% 4 6% 7% 38%	5492
	21st to end	Night	12% 8% 3 7% 6% 4 6% 4 7% 10% 34%	5793
June	1st to 10th	Night	6% 5% 3 6% 5% 5% 5% 4 7% 10% 45%	1890
	11th to 20th	Night	4 3 1 4 3 3 4 5% 6% 11% 55%	1890
	21st to end	Night	6% 4 1 4 4 4 4 5% 9% 11% 50%	1890
July	1st to 10th	Night	5% 6% 3 6% 5% 4 6% 5% 9% 14% 37%	4168
	11th to 20th	Night	5% 4 2 6% 5% 5% 6% 5% 8% 13% 41%	4167
	21st to end	Night	10% 7% 3 7% 5% 4 5% 4 6% 10% 41%	4539
August	1st to 10th	Night	1 2 1 3 2 2 2 2 5% 11% 70%	2926
	11th to 20th	Night	3 2 1 3 3 4 4 5% 8% 12% 56%	3198
	21st to end	Night	7% 5% 3 7% 5% 6% 5% 4 7% 8% 42%	3586
September	1st to 10th	Night	6% 4 2 6% 5% 4 4 4 6% 8% 50%	2000
	11th to 20th	Night	11% 5% 2 6% 4 5% 5% 3 5% 8% 46%	2155
	21st to end	Night	8% 5% 1 4 3 3 3 4 5% 7% 58%	2221
October	1st to 10th	Night	5% 3 1 4 3 3 4 3 5% 7% 61%	2400
	11th to 20th	Night	8% 5% 2 3 3 3 3 3 4 5% 60%	2400
	21st to end	Night	12% 5% 2 4 3 2 3 2 4 5% 59%	2640
November	1st to 10th	Night	12% 4 2 5% 3 3 3 3 4 5% 56%	2460
	11th to 20th	Night	11% 5% 2 4 4 4 4 3 4 6% 54%	2520
	21st to end	Night	14% 7% 3 6% 4 3 3 3 5% 6% 46%	2520
December	1st to 10th	Night	21% 9% 3 5% 4 4 3 2 4 5% 41%	4330
	11th to 20th	Night	15% 10% 3 6% 4 4 3 3 4 5% 45%	4946
	21st to end	Night	14% 10% 2 5% 3 3 3 3 4 5% 49%	6633

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	37% 21% 4 20% 16% 1	5290
	11th to 20th	Day	25% 21% 4 18% 23% 9%	5310
	21st to end	Day	42% 22% 2 9% 15% 9%	5812
February	1st to 10th	Day	20% 59% 2 7% 7% 5%	1890
	11th to 20th	Day	23% 57% 4 8% 6% 2	2070
	21st to end	Day	23% 59% 2 3 7% 5%	1903
March	1st to 10th	Day	40% 29% 3 7% 13% 8%	5046
	11th to 20th	Day	24% 29% 4 13% 16% 13%	5090
	21st to end	Day	33% 29% 8% 16% 12% 3	5585
April	1st to 10th	Day	19% 59% 4 7% 7% 3	2410
	11th to 20th	Day	19% 60% 5% 7% 6% 3	2494
	21st to end	Day	17% 60% 5% 8% 8% 2	2520
May	1st to 10th	Day	42% 25% 6% 16% 8% 2	7056
	11th to 20th	Day	33% 25% 12% 14% 15% 1	7387
	21st to end	Day	34% 27% 13% 16% 9% 1	8405
June	1st to 10th	Day	15% 60% 6% 9% 9%	2730
	11th to 20th	Day	18% 61% 8% 8% 4 1	2730
	21st to end	Day	15% 59% 8% 13% 4	2730
July	1st to 10th	Day	28% 30% 23% 17% 3	5966
	11th to 20th	Day	26% 28% 18% 23% 5%	5961
	21st to end	Day	31% 27% 11% 24% 7%	6371
August	1st to 10th	Day	7% 36% 9% 24% 24% 1	4220
	11th to 20th	Day	9% 37% 16% 31% 5% 1	3885
	21st to end	Day	25% 38% 10% 12% 15%	4311
September	1st to 10th	Day	12% 59% 8% 8% 9% 3	2400
	11th to 20th	Day	14% 58% 7% 12% 7% 2	2239
	21st to end	Day	14% 58% 7% 12% 7% 2	2156
October	1st to 10th	Day	8% 36% 4 7% 16% 30%	3260
	11th to 20th	Day	8% 35% 4 11% 23% 20%	3240
	21st to end	Day	16% 35% 2 8% 30% 8%	3538
November	1st to 10th	Day	20% 55% 5% 7% 9% 4	2058
	11th to 20th	Day	17% 54% 4 9% 11% 6%	2100
	21st to end	Day	18% 54% 3 11% 10% 3	2100
December	1st to 10th	Day	30% 34% 3 11% 19% 3	3075
	11th to 20th	Day	32% 31% 3 9% 16% 9%	3479
	21st to end	Day	32% 26% 4 10% 24% 4	4587
January	1st to 10th	Night	31% 21% 6% 20% 20% 3	7635
	11th to 20th	Night	28% 21% 3 15% 24% 9%	7680
	21st to end	Night	45% 22% 3 11% 12% 7%	8402
February	1st to 10th	Night	19% 59% 3 7% 8% 5%	2730
	11th to 20th	Night	20% 57% 5% 9% 7% 2	2461
	21st to end	Night	21% 59% 2 5% 7% 6%	1903
March	1st to 10th	Night	37% 29% 3 9% 14% 8%	5029
	11th to 20th	Night	28% 29% 4 11% 13% 15%	5090
	21st to end	Night	33% 30% 5% 12% 16% 4	5588
April	1st to 10th	Night	18% 59% 4 7% 8% 5%	2209
	11th to 20th	Night	17% 61% 4 8% 7% 3	2075
	21st to end	Night	16% 60% 5% 7% 9% 3	2100
May	1st to 10th	Night	43% 25% 8% 13% 10% 2	5862
	11th to 20th	Night	37% 25% 9% 13% 14% 3	5493
	21st to end	Night	37% 27% 15% 15% 6% 1	5805
June	1st to 10th	Night	13% 60% 5% 11% 10%	1890
	11th to 20th	Night	12% 62% 10% 11% 4 1	1890
	21st to end	Night	12% 60% 10% 16% 3	1890
July	1st to 10th	Night	25% 31% 26% 16% 2	4125
	11th to 20th	Night	24% 30% 22% 20% 4	4116
	21st to end	Night	31% 28% 12% 22% 7% 1	4410
August	1st to 10th	Night	5% 36% 10% 22% 26% 1	2916
	11th to 20th	Night	8% 38% 19% 32% 4 1	3228
	21st to end	Night	25% 39% 9% 13% 13% 1	3586
September	1st to 10th	Night	12% 59% 7% 10% 8% 4	2000
	11th to 20th	Night	13% 58% 6% 13% 8% 2	2155
	21st to end	Night	12% 59% 7% 12% 7% 3	2221
October	1st to 10th	Night	7% 36% 4 9% 11% 32%	3920
	11th to 20th	Night	6% 35% 2 15% 22% 21%	3899
	21st to end	Night	13% 36% 3 10% 28% 10%	4252
November	1st to 10th	Night	20% 54% 5% 7% 8% 5%	2460
	11th to 20th	Night	17% 54% 3 9% 10% 6%	2520
	21st to end	Night	18% 54% 3 9% 11% 5%	2520
December	1st to 10th	Night	34% 34% 3 9% 19% 2	4330
	11th to 20th	Night	28% 31% 5% 9% 19% 8%	4947
	21st to end	Night	29% 26% 5% 12% 23% 5%	6633

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% 14% 5%	330
	11th to 20th	Day	23% 18% 33% 21% 5%	330
	21st to end	Day	26% 22% 32% 17% 2	363
February	1st to 10th	Day	23% 15% 38% 20% 3 1	330
	11th to 20th	Day	34% 19% 30% 15% 2	330
	21st to end	Day	26% 26% 36% 10% 3	273
March	1st to 10th	Day	25% 18% 34% 19% 5%	330
	11th to 20th	Day	19% 24% 37% 17% 3	330
	21st to end	Day	17% 16% 39% 23% 6%	363
April	1st to 10th	Day	16% 18% 37% 23% 7%	430
	11th to 20th	Day	21% 17% 30% 22% 9% 1	532
	21st to end	Day	16% 13% 31% 28% 10% 2	540
May	1st to 10th	Day	19% 11% 34% 25% 11% 1	543
	11th to 20th	Day	15% 7% 24% 31% 19% 4	685
	21st to end	Day	9% 5% 25% 35% 19% 6%	844
June	1st to 10th	Day	8% 4 16% 32% 30% 10%	780
	11th to 20th	Day	9% 3 15% 34% 32% 7%	780
	21st to end	Day	9% 2 11% 27% 37% 14%	780
July	1st to 10th	Day	7% 2 7% 25% 45% 14%	771
	11th to 20th	Day	5% 2 7% 22% 44% 19%	768
	21st to end	Day	8% 1 6% 25% 46% 15%	845
August	1st to 10th	Day	3 1 6% 20% 48% 22%	726
	11th to 20th	Day	4 2 3 17% 48% 25%	519
	21st to end	Day	11% 2 7% 20% 33% 27%	583
September	1st to 10th	Day	8% 1 9% 22% 40% 20%	530
	11th to 20th	Day	9% 3 9% 23% 35% 21%	369
	21st to end	Day	13% 4 10% 25% 36% 12%	330
October	1st to 10th	Day	6% 3 19% 38% 26% 8%	330
	11th to 20th	Day	8% 6% 26% 31% 22% 7%	330
	21st to end	Day	20% 12% 23% 24% 16% 5%	363
November	1st to 10th	Day	15% 9% 25% 31% 18% 3	330
	11th to 20th	Day	12% 12% 33% 30% 11% 2	330
	21st to end	Day	19% 17% 36% 21% 6% 2	330
December	1st to 10th	Day	21% 9% 40% 19% 8% 3	330
	11th to 20th	Day	22% 12% 34% 25% 7%	330
	21st to end	Day	22% 16% 34% 23% 4 1	363
January	1st to 10th	Night	22% 12% 37% 24% 5%	1050
	11th to 20th	Night	22% 15% 31% 24% 7%	1050
	21st to end	Night	24% 12% 34% 27% 3	1155
February	1st to 10th	Night	21% 15% 37% 25% 3	1050
	11th to 20th	Night	26% 14% 33% 23% 4	825
	21st to end	Night	26% 16% 35% 21% 2	519
March	1st to 10th	Night	24% 11% 33% 27% 5%	630
	11th to 20th	Night	20% 13% 35% 26% 5% 1	630
	21st to end	Night	16% 10% 38% 29% 8%	693
April	1st to 10th	Night	16% 11% 40% 27% 6%	630
	11th to 20th	Night	16% 13% 36% 24% 11%	623
	21st to end	Night	14% 10% 38% 27% 11% 1	630
May	1st to 10th	Night	14% 10% 31% 34% 10%	630
	11th to 20th	Night	13% 7% 27% 33% 17% 3	621
	21st to end	Night	7% 4 25% 39% 20% 4	683
June	1st to 10th	Night	7% 3 16% 39% 32% 3	630
	11th to 20th	Night	5% 3 15% 48% 26% 3	630
	21st to end	Night	8% 1 10% 38% 36% 7%	630
July	1st to 10th	Night	4 2 7% 37% 42% 9%	615
	11th to 20th	Night	4 2 6% 35% 44% 9%	612
	21st to end	Night	5% 1 7% 36% 42% 9%	687
August	1st to 10th	Night	2 1 5% 36% 47% 9%	597
	11th to 20th	Night	5% 6% 33% 47% 9%	594
	21st to end	Night	10% 2 5% 29% 42% 12%	660
September	1st to 10th	Night	7% 2 6% 33% 43% 8%	600
	11th to 20th	Night	12% 1 10% 29% 40% 8%	600
	21st to end	Night	10% 2 12% 34% 34% 8%	621
October	1st to 10th	Night	7% 2 15% 38% 33% 5%	800
	11th to 20th	Night	10% 6% 20% 40% 20% 3	800
	21st to end	Night	15% 7% 23% 34% 19% 2	880
November	1st to 10th	Night	14% 6% 25% 33% 21% 1	820
	11th to 20th	Night	13% 9% 29% 36% 14%	840
	21st to end	Night	19% 9% 31% 29% 11% 1	840
December	1st to 10th	Night	23% 13% 28% 27% 8%	1013
	11th to 20th	Night	24% 10% 31% 29% 5%	1050
	21st to end	Night	22% 12% 30% 29% 6%	1155

Page generated at 2026-07-28 02:25:23. Version ac07

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