Dunning
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dunning clear sky chart from 2005-11-06 to 2024-03-01.

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% 6% 2 5% 4 3 4 4 5% 7% 51%	78524
	Night	8% 6% 3 5% 5% 3 4 4 5% 7% 50%	80939
Transparency	Day	33% 5% 14% 28% 17% 3	78233
	Night	33% 4 13% 28% 18% 3	80753
Seeing	Day	12% 8% 30% 32% 15% 3	14785
	Night	11% 8% 37% 36% 8%	24921

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	6% 12% 5% 8% 5% 2 3 3 3 5% 47%	2538
	11th to 20th	Day	5% 8% 3 6% 6% 5% 7% 6% 6% 8% 40%	2540
	21st to end	Day	4 6% 3 7% 5% 3 3 5% 4 6% 53%	2893
February	1st to 10th	Day	8% 9% 4 7% 7% 3 4 5% 5% 6% 41%	1772
	11th to 20th	Day	7% 9% 3 6% 5% 3 4 4 4 6% 48%	1849
	21st to end	Day	8% 8% 3 5% 4 2 3 3 5% 5% 54%	1570
March	1st to 10th	Day	9% 5% 2 4 4 3 3 3 4 9% 53%	1800
	11th to 20th	Day	11% 7% 2 3 3 3 4 5% 5% 8% 48%	1950
	21st to end	Day	12% 11% 5% 5% 5% 3 4 5% 5% 7% 37%	2196
April	1st to 10th	Day	13% 7% 2 4 3 2 3 4 5% 7% 49%	2160
	11th to 20th	Day	16% 7% 3 5% 4 3 4 4 4 8% 43%	2191
	21st to end	Day	14% 6% 2 5% 5% 3 4 4 5% 6% 47%	2340
May	1st to 10th	Day	14% 5% 3 4 5% 3 4 5% 5% 8% 44%	2340
	11th to 20th	Day	17% 5% 2 4 4 3 4 4 5% 8% 44%	2302
	21st to end	Day	13% 5% 3 5% 6% 2 5% 5% 7% 8% 41%	2620
June	1st to 10th	Day	7% 3 1 4 4 3 4 4 6% 10% 55%	2520
	11th to 20th	Day	10% 4 2 3 4 3 4 5% 7% 8% 52%	2520
	21st to end	Day	4 3 1 4 4 2 4 5% 6% 9% 58%	2520
July	1st to 10th	Day	6% 3 2 4 4 3 4 6% 6% 9% 52%	2520
	11th to 20th	Day	5% 3 1 3 4 3 4 5% 6% 7% 57%	2520
	21st to end	Day	6% 3 2 4 5% 3 5% 5% 6% 9% 53%	2683
August	1st to 10th	Day	7% 5% 2 5% 4 3 5% 6% 7% 10% 46%	2328
	11th to 20th	Day	6% 4 1 4 4 3 5% 5% 6% 8% 54%	2301
	21st to end	Day	6% 4 2 4 5% 3 4 5% 4 6% 58%	2417
September	1st to 10th	Day	9% 4 2 4 4 2 3 4 4 6% 58%	2118
	11th to 20th	Day	6% 4 2 3 4 3 4 4 4 7% 59%	1980
	21st to end	Day	10% 4 2 4 3 2 2 3 4 5% 61%	1980
October	1st to 10th	Day	13% 6% 1 3 3 2 3 3 4 6% 56%	1980
	11th to 20th	Day	9% 5% 2 4 3 2 3 4 5% 6% 59%	1796
	21st to end	Day	12% 8% 3 4 4 2 3 3 3 5% 54%	1782
November	1st to 10th	Day	7% 4 2 5% 4 2 4 4 5% 7% 55%	1673
	11th to 20th	Day	7% 6% 2 4 4 3 3 4 4 6% 58%	1710
	21st to end	Day	8% 7% 3 4 3 2 4 3 5% 7% 54%	1710
December	1st to 10th	Day	6% 7% 3 5% 5% 3 4 5% 5% 7% 50%	1685
	11th to 20th	Day	6% 5% 2 5% 4 3 5% 4 6% 7% 53%	1926
	21st to end	Day	13% 14% 4 7% 7% 2 3 3 3 6% 38%	2794
January	1st to 10th	Night	6% 12% 4 8% 7% 3 4 4 5% 6% 41%	4417
	11th to 20th	Night	3 9% 4 7% 5% 3 5% 4 4 7% 49%	4430
	21st to end	Night	4 5% 4 7% 6% 4 5% 4 6% 6% 49%	4771
February	1st to 10th	Night	9% 8% 4 7% 6% 4 4 4 5% 6% 43%	2423
	11th to 20th	Night	6% 7% 3 7% 6% 3 4 4 7% 7% 45%	2218
	21st to end	Night	6% 6% 3 5% 5% 3 4 5% 4 7% 52%	1884
March	1st to 10th	Night	7% 6% 4 6% 5% 3 3 4 5% 6% 51%	2166
	11th to 20th	Night	10% 7% 3 5% 4 3 3 4 4 6% 51%	2009
	21st to end	Night	12% 9% 4 5% 5% 3 4 4 5% 8% 41%	2156
April	1st to 10th	Night	12% 7% 3 4 5% 2 4 4 5% 8% 47%	1800
	11th to 20th	Night	14% 7% 2 5% 4 2 5% 4 5% 7% 45%	1717
	21st to end	Night	14% 6% 2 5% 4 2 4 4 5% 7% 47%	1620
May	1st to 10th	Night	11% 5% 2 4 5% 3 5% 5% 5% 8% 46%	1620
	11th to 20th	Night	17% 6% 2 4 4 2 3 4 5% 9% 43%	1593
	21st to end	Night	15% 5% 2 5% 4 3 5% 4 7% 10% 39%	1652
June	1st to 10th	Night	9% 3 2 3 4 3 4 4 5% 10% 53%	1440
	11th to 20th	Night	10% 4 2 4 4 2 4 3 6% 10% 51%	1440
	21st to end	Night	4 4 2 5% 5% 3 4 5% 7% 9% 53%	1440
July	1st to 10th	Night	6% 3 2 4 4 3 5% 5% 6% 9% 53%	1440
	11th to 20th	Night	3 3 1 4 5% 3 5% 5% 6% 9% 57%	1440
	21st to end	Night	5% 3 1 4 5% 3 4 6% 6% 11% 51%	1634
August	1st to 10th	Night	6% 3 2 4 6% 3 6% 5% 7% 10% 47%	1611
	11th to 20th	Night	7% 4 1 4 5% 3 3 6% 5% 8% 55%	1600
	21st to end	Night	4 3 2 3 4 2 4 4 6% 8% 60%	1936
September	1st to 10th	Night	8% 4 1 4 4 2 3 3 4 7% 61%	1841
	11th to 20th	Night	6% 4 1 4 4 2 4 4 5% 7% 60%	1980
	21st to end	Night	11% 3 1 3 3 2 3 4 3 5% 61%	1980
October	1st to 10th	Night	15% 4 2 4 3 2 4 3 5% 6% 53%	1980
	11th to 20th	Night	9% 4 2 4 3 2 3 3 3 5% 63%	2145
	21st to end	Night	11% 6% 2 4 3 2 3 3 4 6% 57%	2574
November	1st to 10th	Night	6% 4 1 4 3 2 4 5% 6% 7% 58%	2405
	11th to 20th	Night	7% 5% 2 4 5% 3 4 4 5% 7% 54%	2470
	21st to end	Night	6% 6% 3 4 4 2 3 4 4 7% 55%	2470
December	1st to 10th	Night	6% 6% 3 5% 5% 3 4 4 4 7% 54%	2493
	11th to 20th	Night	5% 6% 3 4 4 2 4 4 5% 7% 55%	3271
	21st to end	Night	14% 13% 3 5% 5% 3 3 3 4 6% 40%	4873

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	39% 4 11% 29% 14% 1	2539
	11th to 20th	Day	39% 10% 14% 21% 14% 2	2540
	21st to end	Day	33% 3 19% 26% 16% 3	2893
February	1st to 10th	Day	44% 5% 13% 23% 13% 3	1772
	11th to 20th	Day	38% 4 12% 25% 18% 4	1859
	21st to end	Day	33% 3 14% 27% 18% 5%	1570
March	1st to 10th	Day	30% 4 13% 27% 23% 3	1800
	11th to 20th	Day	34% 5% 12% 28% 18% 2	1950
	21st to end	Day	46% 6% 15% 23% 10% 1	2196
April	1st to 10th	Day	34% 5% 17% 28% 14% 2	2160
	11th to 20th	Day	41% 4 14% 24% 14% 3	2194
	21st to end	Day	38% 4 12% 30% 14% 1	2340
May	1st to 10th	Day	38% 4 16% 27% 13% 1	2340
	11th to 20th	Day	40% 5% 19% 26% 10%	2306
	21st to end	Day	39% 6% 18% 24% 11% 2	2620
June	1st to 10th	Day	25% 5% 21% 35% 12% 3	2520
	11th to 20th	Day	30% 5% 16% 27% 18% 5%	2520
	21st to end	Day	22% 4 16% 33% 21% 4	2520
July	1st to 10th	Day	28% 6% 15% 30% 18% 3	2451
	11th to 20th	Day	25% 5% 12% 28% 25% 6%	2445
	21st to end	Day	26% 6% 15% 31% 20% 2	2534
August	1st to 10th	Day	31% 7% 21% 25% 13% 4	2314
	11th to 20th	Day	27% 5% 11% 35% 19% 2	2301
	21st to end	Day	27% 4 10% 28% 24% 7%	2417
September	1st to 10th	Day	27% 4 10% 26% 23% 10%	2118
	11th to 20th	Day	26% 4 10% 31% 25% 5%	1980
	21st to end	Day	27% 3 9% 32% 27% 4	1980
October	1st to 10th	Day	31% 3 8% 30% 25% 3	1980
	11th to 20th	Day	27% 4 11% 29% 22% 7%	1796
	21st to end	Day	36% 3 8% 28% 19% 6%	1782
November	1st to 10th	Day	27% 5% 15% 28% 21% 4	1673
	11th to 20th	Day	28% 3 11% 28% 24% 5%	1710
	21st to end	Day	31% 3 13% 28% 21% 5%	1710
December	1st to 10th	Day	34% 4 13% 30% 17% 3	1685
	11th to 20th	Day	29% 5% 14% 35% 15% 1	1924
	21st to end	Day	50% 3 9% 25% 11% 2	2794
January	1st to 10th	Night	44% 4 11% 27% 13% 1	4417
	11th to 20th	Night	36% 4 15% 30% 14% 1	4430
	21st to end	Night	35% 5% 16% 28% 15% 1	4771
February	1st to 10th	Night	43% 4 13% 23% 14% 3	2423
	11th to 20th	Night	37% 4 13% 28% 15% 3	2218
	21st to end	Night	32% 4 12% 27% 19% 6%	1884
March	1st to 10th	Night	34% 3 11% 27% 20% 4	2166
	11th to 20th	Night	35% 3 10% 26% 22% 3	2009
	21st to end	Night	41% 5% 17% 24% 12% 1	2156
April	1st to 10th	Night	36% 5% 16% 23% 16% 3	1800
	11th to 20th	Night	38% 5% 13% 27% 14% 3	1717
	21st to end	Night	37% 5% 12% 30% 16% 1	1620
May	1st to 10th	Night	37% 5% 17% 26% 14% 1	1620
	11th to 20th	Night	39% 5% 19% 24% 12% 2	1594
	21st to end	Night	40% 6% 20% 21% 10% 3	1653
June	1st to 10th	Night	28% 6% 21% 30% 13% 2	1440
	11th to 20th	Night	30% 4 17% 28% 14% 6%	1440
	21st to end	Night	26% 5% 17% 32% 18% 2	1440
July	1st to 10th	Night	27% 7% 16% 32% 15% 3	1400
	11th to 20th	Night	25% 6% 14% 29% 21% 6%	1392
	21st to end	Night	28% 6% 17% 26% 20% 3	1543
August	1st to 10th	Night	31% 8% 21% 25% 13% 3	1601
	11th to 20th	Night	27% 5% 14% 33% 17% 4	1600
	21st to end	Night	22% 5% 14% 26% 24% 8%	1936
September	1st to 10th	Night	24% 4 10% 25% 28% 8%	1841
	11th to 20th	Night	24% 4 12% 31% 24% 5%	1980
	21st to end	Night	27% 3 8% 31% 28% 4	1980
October	1st to 10th	Night	34% 4 9% 25% 25% 2	1980
	11th to 20th	Night	26% 3 9% 29% 25% 8%	2145
	21st to end	Night	31% 3 11% 25% 24% 7%	2574
November	1st to 10th	Night	25% 3 12% 27% 25% 7%	2405
	11th to 20th	Night	29% 3 11% 28% 22% 7%	2470
	21st to end	Night	30% 3 11% 29% 22% 4	2470
December	1st to 10th	Night	32% 3 15% 28% 18% 4	2493
	11th to 20th	Night	29% 3 11% 38% 17% 1	3272
	21st to end	Night	46% 4 10% 28% 11% 1	4873

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	8% 8% 41% 26% 16% 2	270
	11th to 20th	Day	10% 13% 36% 30% 9% 1	270
	21st to end	Day	13% 11% 41% 24% 8% 3	297
February	1st to 10th	Day	13% 11% 46% 26% 4	270
	11th to 20th	Day	13% 12% 45% 23% 6% 1	270
	21st to end	Day	14% 20% 40% 21% 4	225
March	1st to 10th	Day	11% 10% 39% 27% 10% 3	240
	11th to 20th	Day	15% 10% 35% 28% 11% 1	240
	21st to end	Day	21% 11% 38% 20% 9% 2	282
April	1st to 10th	Day	15% 16% 36% 28% 5% 1	420
	11th to 20th	Day	22% 12% 33% 25% 6% 1	472
	21st to end	Day	18% 12% 30% 26% 13% 2	600
May	1st to 10th	Day	15% 9% 32% 30% 12% 1	603
	11th to 20th	Day	19% 7% 30% 27% 14% 3	625
	21st to end	Day	17% 7% 31% 30% 13% 3	679
June	1st to 10th	Day	6% 5% 24% 35% 20% 10%	630
	11th to 20th	Day	10% 6% 29% 34% 17% 3	630
	21st to end	Day	6% 4 27% 41% 18% 4	630
July	1st to 10th	Day	8% 3 21% 37% 26% 5%	621
	11th to 20th	Day	5% 3 19% 44% 23% 5%	618
	21st to end	Day	6% 2 18% 46% 24% 4	684
August	1st to 10th	Day	8% 3 18% 43% 23% 4	626
	11th to 20th	Day	7% 3 23% 44% 20% 3	615
	21st to end	Day	5% 3 26% 39% 22% 5%	536
September	1st to 10th	Day	8% 4 26% 40% 18% 4	408
	11th to 20th	Day	4 3 23% 37% 26% 6%	270
	21st to end	Day	16% 7% 30% 29% 16% 2	270
October	1st to 10th	Day	18% 7% 21% 34% 16% 5%	270
	11th to 20th	Day	9% 13% 34% 30% 12% 2	270
	21st to end	Day	16% 12% 27% 28% 12% 3	297
November	1st to 10th	Day	12% 11% 35% 26% 11% 4	270
	11th to 20th	Day	10% 9% 45% 26% 9% 1	270
	21st to end	Day	17% 11% 36% 23% 9% 4	270
December	1st to 10th	Day	8% 13% 47% 22% 9% 1	270
	11th to 20th	Day	13% 12% 39% 28% 7% 1	270
	21st to end	Day	18% 11% 41% 24% 6% 1	297
January	1st to 10th	Night	10% 12% 41% 31% 7%	950
	11th to 20th	Night	8% 13% 42% 29% 6% 1	950
	21st to end	Night	8% 8% 48% 30% 6%	1045
February	1st to 10th	Night	12% 10% 45% 28% 4	903
	11th to 20th	Night	11% 9% 49% 27% 4	744
	21st to end	Night	10% 9% 47% 28% 6%	628
March	1st to 10th	Night	11% 9% 42% 33% 5%	722
	11th to 20th	Night	13% 8% 44% 30% 5% 1	569
	21st to end	Night	15% 8% 39% 30% 6% 1	594
April	1st to 10th	Night	15% 11% 41% 30% 3	540
	11th to 20th	Night	17% 12% 42% 27% 3	533
	21st to end	Night	16% 11% 31% 32% 9% 1	540
May	1st to 10th	Night	14% 8% 34% 36% 9%	540
	11th to 20th	Night	19% 5% 32% 32% 11%	531
	21st to end	Night	17% 5% 34% 34% 9%	584
June	1st to 10th	Night	11% 5% 26% 41% 15% 2	540
	11th to 20th	Night	11% 5% 34% 38% 10%	540
	21st to end	Night	5% 5% 24% 52% 14%	540
July	1st to 10th	Night	6% 3 27% 45% 18% 1	525
	11th to 20th	Night	3 2 25% 56% 12% 1	522
	21st to end	Night	4 2 25% 56% 12% 1	591
August	1st to 10th	Night	8% 2 20% 54% 15%	537
	11th to 20th	Night	8% 3 25% 51% 13%	534
	21st to end	Night	5% 3 27% 49% 15% 1	594
September	1st to 10th	Night	8% 3 31% 44% 13% 1	540
	11th to 20th	Night	7% 4 29% 47% 13% 1	540
	21st to end	Night	13% 5% 30% 41% 10% 1	540
October	1st to 10th	Night	18% 4 32% 31% 13%	540
	11th to 20th	Night	11% 11% 34% 33% 10%	705
	21st to end	Night	14% 11% 33% 34% 8% 1	990
November	1st to 10th	Night	8% 6% 38% 40% 7% 1	925
	11th to 20th	Night	10% 9% 42% 33% 6% 1	950
	21st to end	Night	9% 8% 38% 36% 8% 1	950
December	1st to 10th	Night	10% 12% 43% 30% 5%	950
	11th to 20th	Night	11% 9% 40% 32% 7%	950
	21st to end	Night	15% 10% 40% 29% 6%	1045

Page generated at 2024-02-27 05:30:15. Version ac07

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