Duette Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Duette Park clear sky chart from 2005-11-06 to 2026-04-02.

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	7% 5% 2 7% 5% 6% 6% 5% 7% 10% 41%	131541
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 44%	130308
Transparency	Day	36% 9% 16% 20% 14% 5%	135287
	Night	35% 9% 16% 20% 14% 6%	134632
Seeing	Day	7% 5% 16% 25% 25% 21%	17420
	Night	8% 4 17% 34% 28% 9%	27543

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	6% 4 2 5% 3 3 4 4 5% 8% 55%	5258
	11th to 20th	Day	18% 7% 3 7% 5% 4 5% 4 5% 7% 34%	5280
	21st to end	Day	12% 5% 2 6% 4 3 4 4 6% 8% 48%	6235
February	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 6% 6% 48%	2100
	11th to 20th	Day	5% 5% 1 4 4 4 4 5% 6% 7% 55%	2048
	21st to end	Day	7% 4 3 5% 4 4 4 4 6% 7% 51%	1821
March	1st to 10th	Day	7% 5% 2 7% 5% 5% 5% 4 5% 8% 47%	5045
	11th to 20th	Day	4 3 2 5% 3 4 3 3 5% 8% 61%	5090
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 8% 51%	5586
April	1st to 10th	Day	6% 3 2 4 5% 5% 5% 5% 7% 9% 50%	2211
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 7% 9% 46%	2176
	21st to end	Day	5% 3 2 4 4 4 5% 4 6% 9% 52%	2375
May	1st to 10th	Day	3 2 1 5% 5% 5% 6% 5% 7% 11% 51%	5804
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 6% 10% 48%	5861
	21st to end	Day	4 4 2 5% 5% 5% 6% 5% 8% 11% 46%	6433
June	1st to 10th	Day	12% 10% 3 9% 8% 7% 7% 5% 7% 9% 23%	2600
	11th to 20th	Day	7% 6% 3 9% 8% 8% 8% 6% 9% 10% 26%	2600
	21st to end	Day	7% 7% 4 8% 8% 8% 8% 7% 8% 9% 25%	2600
July	1st to 10th	Day	6% 6% 3 10% 8% 8% 8% 7% 10% 13% 22%	5900
	11th to 20th	Day	4 5% 3 8% 7% 7% 7% 6% 10% 15% 27%	5900
	21st to end	Day	5% 5% 2 8% 7% 7% 8% 6% 9% 12% 30%	6424
August	1st to 10th	Day	6% 6% 3 11% 7% 8% 7% 6% 8% 12% 26%	4234
	11th to 20th	Day	4 5% 2 8% 7% 8% 8% 6% 8% 10% 34%	3795
	21st to end	Day	6% 5% 3 9% 8% 8% 7% 7% 10% 13% 24%	3949
September	1st to 10th	Day	7% 8% 3 10% 8% 9% 8% 6% 8% 12% 22%	2200
	11th to 20th	Day	8% 7% 3 10% 8% 8% 7% 6% 7% 10% 25%	2200
	21st to end	Day	7% 6% 3 10% 8% 7% 6% 5% 7% 9% 31%	2200
October	1st to 10th	Day	9% 7% 3 8% 6% 6% 6% 5% 6% 9% 35%	2200
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 6% 7% 49%	2025
	21st to end	Day	6% 5% 2 6% 3 5% 4 4 5% 10% 49%	2200
November	1st to 10th	Day	7% 4 2 5% 5% 4 4 4 7% 8% 50%	2057
	11th to 20th	Day	7% 6% 2 6% 5% 4 5% 4 5% 7% 49%	2100
	21st to end	Day	7% 5% 2 5% 5% 4 4 4 6% 8% 49%	1986
December	1st to 10th	Day	4 3 2 4 3 4 4 3 5% 8% 60%	3020
	11th to 20th	Day	8% 6% 2 6% 5% 4 4 4 6% 8% 46%	3463
	21st to end	Day	9% 7% 3 8% 6% 6% 5% 4 6% 8% 38%	4565
January	1st to 10th	Night	7% 5% 2 6% 4 4 4 4 5% 8% 53%	7635
	11th to 20th	Night	18% 9% 3 8% 5% 4 4 4 5% 7% 34%	7680
	21st to end	Night	12% 5% 2 6% 4 4 4 4 5% 7% 46%	7929
February	1st to 10th	Night	8% 7% 2 6% 4 4 4 4 5% 8% 48%	2520
	11th to 20th	Night	9% 5% 2 4 4 4 5% 3 5% 7% 52%	2458
	21st to end	Night	7% 5% 2 6% 4 3 4 3 6% 8% 53%	1982
March	1st to 10th	Night	8% 6% 2 7% 4 4 4 3 5% 8% 48%	5028
	11th to 20th	Night	5% 3 1 5% 3 3 3 3 6% 9% 59%	5090
	21st to end	Night	8% 5% 3 6% 4 3 4 3 5% 7% 51%	5588
April	1st to 10th	Night	5% 4 1 4 4 3 4 3 6% 9% 55%	2212
	11th to 20th	Night	5% 4 2 5% 3 4 4 4 7% 10% 53%	2173
	21st to end	Night	4 3 1 5% 4 4 4 4 5% 8% 57%	2021
May	1st to 10th	Night	4 4 2 6% 4 5% 4 4 7% 8% 53%	4132
	11th to 20th	Night	7% 5% 1 5% 3 4 4 4 6% 8% 54%	4032
	21st to end	Night	4 4 1 5% 4 4 5% 4 6% 10% 54%	4421
June	1st to 10th	Night	9% 7% 2 7% 4 5% 5% 5% 7% 11% 37%	1800
	11th to 20th	Night	6% 6% 3 7% 6% 5% 7% 6% 8% 12% 34%	1800
	21st to end	Night	6% 4 3 8% 6% 7% 6% 6% 9% 13% 33%	1800
July	1st to 10th	Night	6% 7% 3 11% 7% 7% 7% 7% 10% 12% 22%	4058
	11th to 20th	Night	5% 5% 3 9% 7% 7% 9% 7% 10% 12% 26%	4057
	21st to end	Night	6% 7% 3 11% 7% 7% 8% 6% 9% 12% 23%	4427
August	1st to 10th	Night	5% 5% 3 8% 7% 6% 5% 6% 9% 13% 32%	2915
	11th to 20th	Night	3 4 2 7% 5% 7% 7% 6% 10% 13% 35%	3211
	21st to end	Night	5% 6% 2 8% 6% 7% 7% 7% 11% 13% 27%	3949
September	1st to 10th	Night	6% 7% 3 8% 6% 7% 7% 6% 9% 13% 28%	2200
	11th to 20th	Night	10% 6% 3 9% 7% 6% 6% 5% 8% 10% 29%	2200
	21st to end	Night	9% 6% 3 9% 5% 6% 7% 6% 8% 8% 33%	2200
October	1st to 10th	Night	9% 6% 3 8% 5% 5% 5% 4 7% 9% 39%	2200
	11th to 20th	Night	5% 6% 2 6% 4 4 5% 4 6% 7% 50%	2374
	21st to end	Night	8% 5% 2 6% 3 4 4 3 6% 7% 52%	2640
November	1st to 10th	Night	7% 5% 2 6% 4 4 5% 4 6% 8% 50%	2461
	11th to 20th	Night	7% 6% 2 5% 5% 4 4 4 5% 7% 51%	2520
	21st to end	Night	7% 5% 2 6% 5% 4 4 3 5% 8% 50%	2630
December	1st to 10th	Night	5% 3 1 3 3 3 4 3 5% 8% 61%	4380
	11th to 20th	Night	9% 6% 2 6% 4 3 4 4 5% 7% 49%	4952
	21st to end	Night	11% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	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	26% 5% 8% 25% 27% 8%	5259
	11th to 20th	Day	49% 5% 7% 16% 15% 9%	5280
	21st to end	Day	34% 5% 8% 27% 16% 10%	6235
February	1st to 10th	Day	34% 5% 8% 20% 20% 13%	2100
	11th to 20th	Day	26% 5% 10% 23% 24% 11%	2058
	21st to end	Day	31% 5% 10% 18% 25% 11%	1821
March	1st to 10th	Day	35% 6% 11% 19% 21% 8%	5045
	11th to 20th	Day	22% 4 9% 23% 22% 19%	5090
	21st to end	Day	29% 6% 9% 27% 20% 9%	5586
April	1st to 10th	Day	28% 7% 15% 25% 18% 8%	2211
	11th to 20th	Day	34% 6% 11% 18% 22% 9%	2176
	21st to end	Day	27% 5% 10% 25% 26% 8%	2375
May	1st to 10th	Day	22% 10% 21% 28% 16% 4	5838
	11th to 20th	Day	30% 7% 16% 31% 16% 1	5865
	21st to end	Day	26% 11% 19% 29% 14% 1	6447
June	1st to 10th	Day	53% 10% 18% 15% 4	2600
	11th to 20th	Day	47% 12% 21% 17% 2	2600
	21st to end	Day	49% 13% 23% 13% 2 1	2600
July	1st to 10th	Day	48% 16% 29% 6% 1	5835
	11th to 20th	Day	40% 17% 32% 11%	5831
	21st to end	Day	39% 17% 25% 18% 1	6240
August	1st to 10th	Day	46% 13% 29% 9% 2	4221
	11th to 20th	Day	39% 14% 26% 16% 6%	3831
	21st to end	Day	44% 17% 27% 11% 1	3949
September	1st to 10th	Day	51% 15% 21% 11% 2	2200
	11th to 20th	Day	52% 12% 19% 13% 3	2200
	21st to end	Day	46% 10% 17% 16% 9% 2	2200
October	1st to 10th	Day	52% 11% 15% 11% 7% 4	3590
	11th to 20th	Day	27% 7% 10% 21% 30% 5%	3278
	21st to end	Day	27% 6% 9% 24% 26% 8%	3538
November	1st to 10th	Day	30% 6% 11% 22% 19% 11%	2057
	11th to 20th	Day	34% 4 9% 21% 22% 10%	2100
	21st to end	Day	32% 6% 10% 23% 19% 10%	1986
December	1st to 10th	Day	23% 4 15% 29% 20% 9%	3020
	11th to 20th	Day	33% 6% 11% 20% 20% 9%	3460
	21st to end	Day	41% 7% 12% 20% 16% 4	4565
January	1st to 10th	Night	29% 5% 9% 27% 23% 8%	7636
	11th to 20th	Night	49% 5% 9% 17% 12% 8%	7680
	21st to end	Night	36% 6% 11% 23% 14% 9%	7929
February	1st to 10th	Night	34% 5% 10% 18% 22% 10%	2520
	11th to 20th	Night	29% 5% 12% 22% 22% 9%	2459
	21st to end	Night	28% 5% 13% 21% 25% 8%	1982
March	1st to 10th	Night	35% 6% 12% 19% 19% 8%	5028
	11th to 20th	Night	21% 6% 17% 22% 17% 17%	5090
	21st to end	Night	32% 5% 10% 25% 22% 6%	5588
April	1st to 10th	Night	25% 7% 19% 26% 17% 7%	2212
	11th to 20th	Night	26% 7% 16% 22% 23% 7%	2173
	21st to end	Night	24% 6% 13% 26% 25% 6%	2021
May	1st to 10th	Night	24% 11% 19% 28% 13% 4	4160
	11th to 20th	Night	27% 7% 20% 32% 14% 1	4033
	21st to end	Night	23% 10% 21% 30% 15% 1	4429
June	1st to 10th	Night	39% 10% 24% 21% 5%	1800
	11th to 20th	Night	39% 12% 27% 18% 4	1800
	21st to end	Night	40% 16% 25% 15% 5%	1800
July	1st to 10th	Night	50% 16% 28% 6%	4015
	11th to 20th	Night	45% 20% 28% 7%	4006
	21st to end	Night	48% 15% 23% 13%	4297
August	1st to 10th	Night	39% 15% 30% 11% 5%	2904
	11th to 20th	Night	35% 16% 32% 15% 3	3241
	21st to end	Night	43% 17% 31% 8% 1	3949
September	1st to 10th	Night	44% 18% 24% 12% 2	2200
	11th to 20th	Night	48% 13% 22% 15% 2	2200
	21st to end	Night	44% 12% 19% 16% 8% 1	2200
October	1st to 10th	Night	54% 11% 12% 11% 8% 4	3590
	11th to 20th	Night	25% 8% 11% 28% 23% 4	3860
	21st to end	Night	29% 5% 9% 27% 25% 6%	4252
November	1st to 10th	Night	30% 6% 12% 21% 20% 11%	2461
	11th to 20th	Night	31% 7% 10% 23% 20% 9%	2520
	21st to end	Night	32% 5% 10% 23% 21% 8%	2630
December	1st to 10th	Night	21% 5% 17% 30% 15% 12%	4380
	11th to 20th	Night	32% 7% 13% 21% 18% 10%	4954
	21st to end	Night	42% 8% 14% 18% 14% 4	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	9% 10% 36% 29% 13% 2	330
	11th to 20th	Day	8% 13% 35% 31% 9% 4	330
	21st to end	Day	15% 13% 39% 25% 6% 1	363
February	1st to 10th	Day	11% 9% 28% 31% 17% 5%	330
	11th to 20th	Day	6% 8% 33% 34% 15% 4	330
	21st to end	Day	7% 8% 27% 37% 19% 3	364
March	1st to 10th	Day	6% 6% 34% 35% 17% 2	540
	11th to 20th	Day	7% 8% 28% 30% 23% 4	540
	21st to end	Day	6% 5% 27% 36% 22% 5%	594
April	1st to 10th	Day	5% 6% 31% 33% 22% 3	504
	11th to 20th	Day	7% 8% 24% 33% 22% 6%	492
	21st to end	Day	5% 4 19% 30% 34% 9%	500
May	1st to 10th	Day	4 3 13% 34% 33% 14%	503
	11th to 20th	Day	10% 3 14% 27% 28% 18%	527
	21st to end	Day	7% 2 7% 20% 34% 30%	573
June	1st to 10th	Day	14% 4 6% 21% 28% 26%	530
	11th to 20th	Day	8% 2 7% 17% 27% 39%	530
	21st to end	Day	5% 2 3 10% 28% 51%	530
July	1st to 10th	Day	6% 2 3 10% 21% 59%	525
	11th to 20th	Day	3 2 2 11% 31% 52%	524
	21st to end	Day	10% 1 2 13% 24% 50%	576
August	1st to 10th	Day	7% 2 5% 10% 27% 48%	526
	11th to 20th	Day	5% 1 3 10% 27% 54%	519
	21st to end	Day	8% 3 5% 15% 31% 37%	583
September	1st to 10th	Day	6% 3 5% 11% 34% 41%	530
	11th to 20th	Day	7% 3 6% 20% 32% 32%	530
	21st to end	Day	6% 2 5% 21% 36% 30%	530
October	1st to 10th	Day	11% 4 13% 30% 33% 11%	530
	11th to 20th	Day	6% 4 14% 34% 31% 11%	530
	21st to end	Day	8% 3 19% 37% 27% 7%	583
November	1st to 10th	Day	10% 6% 19% 31% 28% 7%	535
	11th to 20th	Day	11% 4 19% 35% 24% 5%	540
	21st to end	Day	8% 5% 24% 34% 23% 5%	426
December	1st to 10th	Day	5% 8% 31% 35% 14% 6%	330
	11th to 20th	Day	9% 5% 32% 34% 17% 2	330
	21st to end	Day	6% 8% 27% 34% 19% 6%	363
January	1st to 10th	Night	9% 6% 28% 40% 16%	840
	11th to 20th	Night	11% 6% 26% 42% 13% 1	840
	21st to end	Night	13% 8% 32% 37% 10%	924
February	1st to 10th	Night	11% 7% 28% 39% 15% 1	840
	11th to 20th	Night	10% 5% 28% 43% 14% 1	823
	21st to end	Night	9% 4 27% 47% 13% 1	692
March	1st to 10th	Night	6% 6% 32% 44% 12%	840
	11th to 20th	Night	7% 6% 28% 42% 16% 1	840
	21st to end	Night	6% 5% 27% 46% 15% 1	924
April	1st to 10th	Night	6% 4 25% 46% 19%	805
	11th to 20th	Night	5% 4 26% 46% 18% 1	791
	21st to end	Night	6% 3 24% 46% 22%	800
May	1st to 10th	Night	3 2 12% 50% 30% 3	648
	11th to 20th	Night	7% 2 11% 43% 32% 4	591
	21st to end	Night	5% 2 7% 35% 44% 8%	650
June	1st to 10th	Night	11% 1 5% 28% 46% 10%	600
	11th to 20th	Night	5% 2 5% 19% 46% 24%	600
	21st to end	Night	6% 1 2 13% 46% 33%	600
July	1st to 10th	Night	7% 2 2 8% 46% 35%	585
	11th to 20th	Night	5% 1 2 8% 47% 37%	582
	21st to end	Night	5% 2 2 7% 50% 34%	657
August	1st to 10th	Night	5% 2 2 10% 46% 35%	597
	11th to 20th	Night	4 1 3 8% 40% 43%	610
	21st to end	Night	10% 3 5% 19% 38% 25%	880
September	1st to 10th	Night	8% 2 5% 19% 46% 21%	800
	11th to 20th	Night	11% 5% 6% 22% 39% 18%	800
	21st to end	Night	11% 4 5% 26% 42% 13%	800
October	1st to 10th	Night	13% 3 12% 40% 29% 5%	800
	11th to 20th	Night	7% 4 14% 36% 38% 3	800
	21st to end	Night	10% 3 16% 42% 27% 2	880
November	1st to 10th	Night	9% 4 20% 41% 22% 4	820
	11th to 20th	Night	8% 5% 18% 43% 24% 2	840
	21st to end	Night	9% 2 24% 44% 20%	840
December	1st to 10th	Night	8% 4 23% 40% 24% 1	840
	11th to 20th	Night	9% 5% 22% 41% 21% 1	840
	21st to end	Night	9% 5% 24% 40% 21% 1	924

Page generated at 2026-03-30 02:18:45. Version ac07

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