Davenport Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Davenport Beach clear sky chart from 2005-11-05 to 2024-10-14.

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	8% 6% 2 4 3 3 3 3 5% 9% 53%	100821
	Night	10% 7% 2 5% 3 3 3 3 5% 8% 51%	97957
Transparency	Day	13% 49% 6% 10% 11% 11%	100582
	Night	16% 51% 6% 9% 9% 9%	97785
Seeing	Day	10% 5% 12% 28% 32% 14%	15429
	Night	12% 5% 11% 26% 33% 14%	24792

By Month

Percentage Cloud Cover SW (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	15% 6% 2 5% 4 4 3 3 6% 7% 44%	2777
	11th to 20th	Day	18% 8% 3 6% 4 4 4 4 5% 7% 36%	2860
	21st to end	Day	22% 8% 3 6% 5% 4 5% 3 6% 8% 33%	3146
February	1st to 10th	Day	18% 6% 2 4 4 3 3 3 5% 6% 46%	1710
	11th to 20th	Day	13% 7% 2 5% 4 4 4 4 6% 7% 43%	1762
	21st to end	Day	13% 5% 2 6% 4 3 4 4 4 6% 48%	1570
March	1st to 10th	Day	15% 10% 3 7% 6% 5% 5% 5% 7% 8% 30%	3404
	11th to 20th	Day	11% 4 1 4 3 3 3 3 5% 8% 55%	3490
	21st to end	Day	15% 8% 2 5% 4 4 5% 4 6% 9% 37%	3875
April	1st to 10th	Day	12% 6% 2 4 4 3 4 4 5% 7% 49%	2280
	11th to 20th	Day	8% 5% 2 5% 3 2 3 3 7% 9% 53%	2249
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 9% 52%	2280
May	1st to 10th	Day	6% 3 1 2 2 2 2 2 4 7% 69%	3883
	11th to 20th	Day	3 11% 2 7% 3 3 3 3 5% 11% 50%	4091
	21st to end	Day	3 9% 2 4 3 3 3 3 4 8% 58%	4813
June	1st to 10th	Day	5% 6% 2 5% 5% 3 3 4 6% 9% 51%	2660
	11th to 20th	Day	3 6% 2 3 3 3 3 4 6% 9% 59%	2660
	21st to end	Day	3 5% 2 5% 2 3 3 3 5% 10% 60%	2660
July	1st to 10th	Day	1 4 1 3 2 3 3 3 4 8% 68%	4339
	11th to 20th	Day	2 6% 2 4 3 3 3 3 5% 10% 60%	4110
	21st to end	Day	1 5% 1 5% 3 3 3 4 6% 13% 57%	4455
August	1st to 10th	Day	1 4 1 4 3 3 5% 4 7% 12% 55%	4091
	11th to 20th	Day	1 4 2 3 2 2 3 3 4 10% 66%	3799
	21st to end	Day	1 6% 2 5% 3 3 3 3 5% 12% 58%	4180
September	1st to 10th	Day	1 4 1 3 3 3 3 2 6% 8% 65%	2280
	11th to 20th	Day	4 6% 2 5% 3 3 4 4 6% 10% 54%	2280
	21st to end	Day	4 3 1 2 2 2 2 2 4 10% 67%	2012
October	1st to 10th	Day	3 3 1 4 4 4 3 2 5% 7% 65%	1900
	11th to 20th	Day	6% 5% 1 3 3 4 3 2 4 8% 59%	1831
	21st to end	Day	8% 5% 2 4 3 3 3 3 4 7% 59%	1980
November	1st to 10th	Day	9% 4 2 4 3 4 4 4 6% 7% 54%	1855
	11th to 20th	Day	10% 5% 2 4 3 3 3 4 6% 6% 53%	1710
	21st to end	Day	11% 4 1 4 3 3 3 3 3 7% 58%	1587
December	1st to 10th	Day	14% 6% 2 6% 4 3 4 3 6% 7% 45%	1520
	11th to 20th	Day	28% 9% 2 5% 3 3 3 3 6% 6% 33%	1928
	21st to end	Day	22% 6% 2 4 3 4 4 3 5% 7% 39%	2794
January	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 5% 6% 48%	4160
	11th to 20th	Night	20% 7% 2 5% 4 4 5% 5% 5% 7% 35%	4110
	21st to end	Night	21% 7% 3 7% 4 4 4 4 6% 7% 34%	4521
February	1st to 10th	Night	18% 6% 2 4 3 3 4 3 4 5% 49%	2470
	11th to 20th	Night	12% 7% 2 5% 3 2 4 4 7% 8% 45%	2304
	21st to end	Night	12% 7% 2 4 3 3 3 3 6% 6% 51%	1884
March	1st to 10th	Night	17% 11% 3 6% 5% 4 5% 3 6% 6% 34%	3466
	11th to 20th	Night	12% 4 2 4 3 3 2 2 4 8% 57%	3490
	21st to end	Night	15% 11% 2 6% 5% 4 4 3 5% 8% 37%	3777
April	1st to 10th	Night	12% 6% 2 4 5% 4 4 4 5% 8% 47%	1900
	11th to 20th	Night	10% 6% 1 4 3 3 3 3 5% 7% 54%	1879
	21st to end	Night	6% 7% 1 3 2 3 3 3 5% 11% 56%	1900
May	1st to 10th	Night	4 4 1 3 2 2 2 2 4 9% 66%	3090
	11th to 20th	Night	2 17% 4 9% 4 3 3 3 3 10% 42%	2810
	21st to end	Night	3 10% 1 4 2 3 2 2 4 10% 59%	2762
June	1st to 10th	Night	4 5% 3 5% 3 3 4 4 6% 10% 54%	1520
	11th to 20th	Night	2 7% 2 4 3 3 3 3 5% 8% 62%	1520
	21st to end	Night	3 5% 1 3 2 3 4 3 6% 10% 60%	1520
July	1st to 10th	Night	1 6% 1 3 2 3 2 2 3 7% 69%	2619
	11th to 20th	Night	1 8% 2 5% 3 2 2 2 5% 9% 61%	2860
	21st to end	Night	1 8% 2 6% 4 3 5% 4 7% 13% 48%	3109
August	1st to 10th	Night	2 8% 2 6% 4 4 4 3 6% 11% 50%	2848
	11th to 20th	Night	1 4 1 4 2 2 2 2 4 9% 68%	3035
	21st to end	Night	1 8% 2 6% 3 3 3 3 5% 8% 59%	3498
September	1st to 10th	Night	1 6% 2 3 3 3 3 3 4 8% 63%	1900
	11th to 20th	Night	4 7% 2 4 3 3 3 3 4 9% 57%	1900
	21st to end	Night	3 6% 1 4 2 2 2 2 3 8% 67%	2162
October	1st to 10th	Night	4 5% 2 5% 2 2 2 2 5% 6% 65%	2280
	11th to 20th	Night	6% 5% 2 5% 3 2 3 2 5% 7% 59%	2207
	21st to end	Night	8% 4 2 4 3 3 2 2 4 7% 62%	2376
November	1st to 10th	Night	9% 4 2 5% 2 3 3 2 5% 7% 58%	2221
	11th to 20th	Night	10% 4 1 4 3 4 3 3 6% 9% 54%	2470
	21st to end	Night	8% 4 1 4 3 3 4 3 5% 6% 59%	2591
December	1st to 10th	Night	16% 6% 2 5% 3 3 3 2 5% 6% 50%	2660
	11th to 20th	Night	28% 8% 3 4 3 2 3 3 5% 6% 34%	3276
	21st to end	Night	21% 8% 2 5% 4 3 3 3 5% 7% 39%	4862

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	24% 42% 8% 19% 6% 1	2777
	11th to 20th	Day	38% 42% 8% 8% 2 2	2860
	21st to end	Day	34% 43% 6% 11% 4 2	3146
February	1st to 10th	Day	17% 65% 4 6% 5% 2	1710
	11th to 20th	Day	14% 65% 3 6% 7% 4	1771
	21st to end	Day	12% 65% 4 10% 6% 3	1570
March	1st to 10th	Day	32% 49% 6% 5% 8% 1	3404
	11th to 20th	Day	11% 42% 9% 20% 9% 10%	3490
	21st to end	Day	28% 46% 10% 11% 3 1	3875
April	1st to 10th	Day	14% 65% 5% 9% 6% 1	2280
	11th to 20th	Day	9% 67% 6% 11% 7% 1	2252
	21st to end	Day	9% 66% 7% 8% 7% 2	2280
May	1st to 10th	Day	9% 40% 8% 19% 17% 6%	3883
	11th to 20th	Day	7% 48% 11% 14% 14% 5%	4094
	21st to end	Day	12% 42% 7% 18% 19% 2	4814
June	1st to 10th	Day	8% 66% 5% 9% 10% 3	2660
	11th to 20th	Day	6% 65% 4 9% 12% 3	2660
	21st to end	Day	6% 63% 4 6% 9% 12%	2660
July	1st to 10th	Day	5% 35% 3 5% 4 48%	4272
	11th to 20th	Day	7% 36% 4 6% 4 43%	4041
	21st to end	Day	5% 34% 3 9% 17% 31%	4315
August	1st to 10th	Day	10% 37% 4 5% 16% 27%	4076
	11th to 20th	Day	5% 37% 4 6% 24% 25%	3836
	21st to end	Day	8% 36% 5% 7% 22% 21%	4179
September	1st to 10th	Day	5% 60% 5% 6% 12% 12%	2280
	11th to 20th	Day	9% 60% 6% 7% 11% 6%	2280
	21st to end	Day	6% 60% 4 9% 15% 6%	2012
October	1st to 10th	Day	4 59% 3 7% 12% 15%	1900
	11th to 20th	Day	9% 63% 5% 6% 8% 9%	1831
	21st to end	Day	9% 62% 4 8% 8% 9%	1980
November	1st to 10th	Day	7% 58% 4 12% 13% 6%	1855
	11th to 20th	Day	14% 60% 6% 10% 9% 2	1710
	21st to end	Day	12% 60% 6% 7% 13% 2	1587
December	1st to 10th	Day	18% 61% 5% 7% 4 5%	1520
	11th to 20th	Day	32% 49% 3 5% 8% 4	1928
	21st to end	Day	28% 40% 7% 16% 8% 2	2794
January	1st to 10th	Night	23% 42% 11% 16% 6% 1	4160
	11th to 20th	Night	36% 43% 10% 6% 3 2	4110
	21st to end	Night	35% 44% 5% 8% 5% 2	4521
February	1st to 10th	Night	18% 64% 4 5% 5% 4	2470
	11th to 20th	Night	13% 65% 4 7% 8% 3	2306
	21st to end	Night	11% 65% 5% 11% 6% 2	1884
March	1st to 10th	Night	32% 48% 6% 6% 7% 1	3466
	11th to 20th	Night	14% 41% 9% 14% 13% 9%	3490
	21st to end	Night	28% 48% 7% 12% 3 1	3777
April	1st to 10th	Night	12% 66% 4 8% 7% 2	1900
	11th to 20th	Night	11% 66% 5% 11% 5% 2	1879
	21st to end	Night	9% 69% 5% 9% 7% 2	1900
May	1st to 10th	Night	9% 45% 7% 17% 13% 9%	3090
	11th to 20th	Night	10% 62% 6% 12% 6% 6%	2811
	21st to end	Night	11% 46% 9% 16% 17% 2	2762
June	1st to 10th	Night	9% 67% 3 8% 9% 5%	1520
	11th to 20th	Night	8% 65% 5% 7% 10% 5%	1520
	21st to end	Night	4 64% 3 5% 10% 14%	1520
July	1st to 10th	Night	6% 36% 5% 3 5% 46%	2577
	11th to 20th	Night	9% 36% 4 7% 6% 39%	2806
	21st to end	Night	8% 36% 6% 10% 13% 28%	3011
August	1st to 10th	Night	13% 38% 8% 5% 16% 21%	2839
	11th to 20th	Night	5% 37% 2 4 19% 33%	3063
	21st to end	Night	9% 38% 5% 7% 19% 22%	3498
September	1st to 10th	Night	6% 61% 4 5% 12% 11%	1900
	11th to 20th	Night	8% 60% 3 10% 12% 6%	1900
	21st to end	Night	7% 60% 4 9% 11% 9%	2162
October	1st to 10th	Night	5% 60% 2 5% 10% 18%	2280
	11th to 20th	Night	9% 62% 5% 7% 8% 8%	2207
	21st to end	Night	8% 62% 3 9% 8% 10%	2376
November	1st to 10th	Night	7% 58% 4 12% 12% 7%	2221
	11th to 20th	Night	13% 60% 6% 10% 8% 3	2470
	21st to end	Night	13% 60% 4 8% 10% 4	2591
December	1st to 10th	Night	16% 61% 6% 8% 4 5%	2660
	11th to 20th	Night	30% 49% 4 5% 8% 4	3276
	21st to end	Night	27% 41% 8% 12% 8% 2	4862

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	28% 3 16% 26% 21% 7%	327
	11th to 20th	Day	17% 2 13% 29% 29% 9%	370
	21st to end	Day	15% 2 13% 31% 30% 10%	407
February	1st to 10th	Day	19% 3 16% 25% 25% 12%	370
	11th to 20th	Day	15% 9% 18% 27% 26% 5%	412
	21st to end	Day	10% 6% 19% 32% 26% 6%	382
March	1st to 10th	Day	20% 6% 20% 29% 20% 5%	460
	11th to 20th	Day	21% 3 16% 27% 24% 9%	460
	21st to end	Day	13% 5% 21% 37% 19% 6%	506
April	1st to 10th	Day	13% 6% 18% 36% 20% 7%	460
	11th to 20th	Day	10% 7% 19% 33% 21% 9%	452
	21st to end	Day	8% 5% 23% 31% 21% 12%	460
May	1st to 10th	Day	7% 5% 18% 33% 29% 8%	463
	11th to 20th	Day	8% 5% 17% 29% 28% 13%	488
	21st to end	Day	9% 7% 15% 25% 28% 16%	529
June	1st to 10th	Day	8% 5% 11% 33% 32% 10%	490
	11th to 20th	Day	5% 5% 16% 31% 33% 11%	490
	21st to end	Day	6% 6% 7% 29% 41% 11%	490
July	1st to 10th	Day	8% 6% 5% 21% 42% 19%	486
	11th to 20th	Day	7% 6% 6% 19% 44% 19%	484
	21st to end	Day	4 6% 3 21% 42% 24%	531
August	1st to 10th	Day	6% 7% 5% 26% 42% 13%	487
	11th to 20th	Day	6% 5% 5% 27% 36% 21%	477
	21st to end	Day	5% 7% 3 22% 41% 22%	539
September	1st to 10th	Day	3 3 6% 25% 45% 19%	490
	11th to 20th	Day	7% 6% 7% 30% 34% 16%	490
	21st to end	Day	5% 5% 8% 21% 41% 20%	490
October	1st to 10th	Day	4 5% 10% 25% 35% 21%	490
	11th to 20th	Day	6% 5% 9% 22% 33% 25%	463
	21st to end	Day	9% 4 8% 30% 32% 17%	495
November	1st to 10th	Day	8% 3 14% 25% 34% 16%	451
	11th to 20th	Day	9% 4 10% 29% 34% 13%	270
	21st to end	Day	9% 1 8% 33% 36% 12%	212
December	1st to 10th	Day	17% 4 11% 28% 29% 11%	180
	11th to 20th	Day	16% 2 19% 24% 30% 8%	180
	21st to end	Day	19% 2 19% 29% 23% 8%	198
January	1st to 10th	Night	18% 4 13% 28% 27% 10%	760
	11th to 20th	Night	17% 3 11% 27% 29% 13%	760
	21st to end	Night	17% 4 9% 30% 32% 9%	836
February	1st to 10th	Night	19% 4 13% 26% 27% 10%	760
	11th to 20th	Night	15% 5% 16% 31% 24% 9%	744
	21st to end	Night	14% 6% 19% 31% 25% 5%	628
March	1st to 10th	Night	19% 7% 15% 28% 26% 6%	760
	11th to 20th	Night	17% 4 14% 29% 29% 8%	760
	21st to end	Night	16% 5% 17% 32% 24% 5%	836
April	1st to 10th	Night	13% 6% 18% 33% 25% 7%	760
	11th to 20th	Night	13% 9% 16% 29% 24% 9%	751
	21st to end	Night	9% 5% 17% 32% 23% 14%	760
May	1st to 10th	Night	9% 4 15% 31% 31% 11%	709
	11th to 20th	Night	8% 8% 11% 26% 32% 15%	551
	21st to end	Night	10% 8% 11% 27% 28% 15%	411
June	1st to 10th	Night	7% 4 9% 32% 36% 12%	380
	11th to 20th	Night	6% 4 10% 29% 42% 9%	380
	21st to end	Night	5% 5% 4 22% 47% 16%	380
July	1st to 10th	Night	7% 7% 3 17% 43% 23%	408
	11th to 20th	Night	9% 4 2 14% 42% 30%	552
	21st to end	Night	10% 7% 3 11% 43% 26%	624
August	1st to 10th	Night	8% 8% 2 19% 42% 20%	567
	11th to 20th	Night	6% 5% 2 20% 46% 21%	697
	21st to end	Night	6% 7% 5% 15% 44% 24%	836
September	1st to 10th	Night	6% 4 3 18% 44% 25%	760
	11th to 20th	Night	6% 5% 5% 22% 44% 17%	760
	21st to end	Night	5% 3 8% 19% 42% 23%	760
October	1st to 10th	Night	7% 3 8% 27% 34% 21%	760
	11th to 20th	Night	8% 3 8% 20% 40% 22%	734
	21st to end	Night	10% 4 7% 25% 33% 22%	792
November	1st to 10th	Night	10% 3 11% 26% 34% 17%	740
	11th to 20th	Night	12% 2 8% 28% 37% 13%	760
	21st to end	Night	9% 2 11% 33% 34% 11%	760
December	1st to 10th	Night	16% 4 11% 30% 30% 8%	760
	11th to 20th	Night	21% 4 13% 28% 27% 7%	760
	21st to end	Night	18% 4 19% 30% 23% 6%	836

Page generated at 2024-10-11 07:50:02. Version ac07

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