Double Diamond Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Double Diamond Ranch clear sky chart from 2005-11-06 to 2024-02-10.

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	5% 3 2 3 4 3 4 4 5% 7% 60%	78930
	Night	4 3 2 3 4 2 4 4 5% 8% 61%	80093
Transparency	Day	23% 5% 9% 18% 25% 20%	78680
	Night	21% 5% 9% 18% 25% 21%	79865
Seeing	Day	8% 9% 25% 31% 22% 5%	13566
	Night	6% 6% 25% 41% 20% 2	23820

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	3 3 1 2 2 1 3 3 3 5% 74%	3167
	11th to 20th	Day	3 2 1 2 2 1 3 3 4 5% 73%	3170
	21st to end	Day	3 4 2 4 4 2 4 4 4 6% 64%	3487
February	1st to 10th	Day	3 3 1 3 3 2 5% 5% 4 6% 64%	1890
	11th to 20th	Day	5% 3 2 3 3 2 4 4 4 7% 62%	1749
	21st to end	Day	2 3 1 2 3 2 4 4 5% 9% 65%	1480
March	1st to 10th	Day	3 5% 3 4 4 3 4 5% 6% 9% 54%	1800
	11th to 20th	Day	5% 5% 2 4 4 2 5% 4 5% 5% 58%	1876
	21st to end	Day	2 3 2 3 3 2 3 4 6% 7% 66%	2375
April	1st to 10th	Day	4 3 2 3 3 2 4 4 5% 7% 65%	2160
	11th to 20th	Day	3 3 1 2 3 2 4 4 5% 6% 66%	2131
	21st to end	Day	5% 3 1 2 2 2 3 2 4 6% 69%	2160
May	1st to 10th	Day	4 3 1 2 3 2 3 4 5% 6% 66%	2160
	11th to 20th	Day	5% 4 1 3 4 3 4 3 5% 7% 60%	2125
	21st to end	Day	4 2 1 2 3 2 3 4 6% 9% 63%	2522
June	1st to 10th	Day	2 2 1 3 3 2 4 5% 7% 9% 62%	2340
	11th to 20th	Day	3 2 1 2 3 2 5% 5% 6% 8% 61%	2340
	21st to end	Day	5% 3 1 3 5% 4 6% 7% 7% 9% 53%	2340
July	1st to 10th	Day	7% 4 2 5% 6% 5% 7% 8% 8% 9% 39%	2200
	11th to 20th	Day	5% 3 2 4 5% 3 6% 6% 7% 9% 50%	2160
	21st to end	Day	4 3 2 5% 6% 4 7% 6% 8% 10% 46%	2349
August	1st to 10th	Day	3 2 1 5% 4 4 7% 6% 7% 11% 50%	2149
	11th to 20th	Day	7% 6% 3 7% 8% 4 7% 8% 7% 9% 35%	2123
	21st to end	Day	7% 4 2 5% 7% 5% 5% 7% 7% 9% 42%	2376
September	1st to 10th	Day	10% 5% 2 5% 5% 3 5% 6% 7% 8% 43%	2160
	11th to 20th	Day	11% 5% 2 5% 6% 3 5% 6% 7% 8% 42%	2033
	21st to end	Day	8% 4 2 5% 4 4 5% 4 5% 6% 53%	1980
October	1st to 10th	Day	3 3 2 3 3 2 4 4 5% 7% 63%	1980
	11th to 20th	Day	7% 3 2 4 4 2 3 3 3 5% 65%	1900
	21st to end	Day	5% 2 1 2 3 2 2 2 3 6% 71%	1980
November	1st to 10th	Day	6% 4 1 2 2 1 2 2 3 6% 71%	1774
	11th to 20th	Day	4 4 1 3 4 1 3 4 4 5% 68%	1710
	21st to end	Day	6% 5% 2 4 4 2 3 3 3 6% 63%	1710
December	1st to 10th	Day	7% 4 2 3 3 2 3 3 5% 8% 61%	1710
	11th to 20th	Day	2 3 1 4 4 3 5% 5% 6% 8% 60%	2161
	21st to end	Day	3 3 1 3 2 2 2 3 5% 6% 69%	3203
January	1st to 10th	Night	3 3 1 2 3 2 3 3 3 5% 72%	3788
	11th to 20th	Night	4 2 1 2 2 2 2 4 4 7% 70%	3800
	21st to end	Night	4 4 2 5% 5% 3 4 4 4 7% 57%	4180
February	1st to 10th	Night	3 4 2 3 3 3 3 4 4 7% 63%	2274
	11th to 20th	Night	5% 4 2 4 4 2 5% 5% 4 7% 58%	2098
	21st to end	Night	4 3 2 3 3 2 4 4 4 6% 65%	1776
March	1st to 10th	Night	4 4 1 4 4 3 4 4 6% 8% 58%	2160
	11th to 20th	Night	5% 5% 3 4 4 3 4 3 5% 5% 59%	2079
	21st to end	Night	3 3 1 3 3 2 4 4 5% 6% 67%	1980
April	1st to 10th	Night	5% 3 2 4 4 3 4 4 5% 6% 60%	1800
	11th to 20th	Night	4 3 2 3 3 3 4 4 5% 7% 62%	1777
	21st to end	Night	3 3 1 2 3 2 3 4 5% 6% 68%	1800
May	1st to 10th	Night	4 3 2 3 4 2 4 4 5% 7% 64%	1800
	11th to 20th	Night	6% 3 2 4 4 2 4 3 7% 6% 58%	1770
	21st to end	Night	3 3 2 3 4 3 4 4 6% 9% 58%	1747
June	1st to 10th	Night	3 2 1 3 3 3 5% 7% 7% 10% 57%	1620
	11th to 20th	Night	2 3 1 3 4 4 5% 5% 7% 10% 55%	1620
	21st to end	Night	3 3 1 3 4 3 4 7% 6% 9% 56%	1620
July	1st to 10th	Night	4 3 1 5% 4 3 6% 7% 8% 12% 47%	1752
	11th to 20th	Night	3 2 1 2 3 2 4 5% 7% 10% 61%	1800
	21st to end	Night	2 2 1 3 4 3 5% 5% 6% 11% 57%	1969
August	1st to 10th	Night	3 1 1 2 2 2 4 5% 9% 13% 59%	1790
	11th to 20th	Night	4 3 1 4 5% 3 4 6% 10% 13% 47%	1778
	21st to end	Night	5% 3 2 3 5% 3 5% 6% 9% 10% 48%	1980
September	1st to 10th	Night	7% 3 2 3 5% 3 4 5% 6% 11% 52%	1800
	11th to 20th	Night	7% 5% 2 5% 5% 3 4 6% 6% 10% 48%	1926
	21st to end	Night	8% 2 2 3 4 4 4 6% 7% 9% 52%	1980
October	1st to 10th	Night	4 3 1 3 3 2 4 4 6% 8% 60%	1980
	11th to 20th	Night	8% 3 1 4 3 2 4 3 5% 6% 61%	2056
	21st to end	Night	4 3 2 3 3 1 2 3 3 5% 70%	2376
November	1st to 10th	Night	5% 3 1 2 2 1 3 3 4 5% 70%	2281
	11th to 20th	Night	3 4 2 3 3 1 3 3 5% 7% 66%	2470
	21st to end	Night	5% 3 2 3 3 2 3 4 5% 7% 63%	2470
December	1st to 10th	Night	7% 3 2 4 4 2 3 4 5% 8% 59%	2470
	11th to 20th	Night	3 4 2 4 5% 3 4 5% 4 7% 60%	3036
	21st to end	Night	3 3 1 3 3 2 3 3 4 6% 69%	4490

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	16% 2 4 11% 27% 40%	3168
	11th to 20th	Day	14% 3 5% 13% 42% 23%	3170
	21st to end	Day	21% 5% 6% 18% 34% 15%	3487
February	1st to 10th	Day	20% 4 5% 13% 25% 32%	1890
	11th to 20th	Day	23% 4 6% 14% 26% 27%	1759
	21st to end	Day	17% 3 4 13% 28% 34%	1480
March	1st to 10th	Day	26% 4 7% 16% 25% 23%	1800
	11th to 20th	Day	26% 4 5% 12% 22% 31%	1876
	21st to end	Day	18% 3 6% 11% 30% 32%	2375
April	1st to 10th	Day	19% 4 6% 14% 27% 32%	2160
	11th to 20th	Day	18% 4 8% 11% 26% 34%	2134
	21st to end	Day	18% 3 4 12% 31% 32%	2160
May	1st to 10th	Day	18% 4 6% 12% 25% 34%	2160
	11th to 20th	Day	22% 5% 8% 18% 26% 21%	2128
	21st to end	Day	17% 6% 11% 20% 23% 23%	2522
June	1st to 10th	Day	16% 7% 13% 23% 26% 17%	2340
	11th to 20th	Day	18% 6% 10% 17% 30% 19%	2340
	21st to end	Day	25% 9% 11% 21% 21% 13%	2340
July	1st to 10th	Day	37% 11% 16% 22% 13% 2	2141
	11th to 20th	Day	27% 9% 13% 24% 21% 5%	2097
	21st to end	Day	27% 10% 18% 31% 13% 1	2219
August	1st to 10th	Day	25% 9% 14% 32% 17% 3	2136
	11th to 20th	Day	41% 10% 17% 19% 10% 2	2123
	21st to end	Day	36% 10% 15% 20% 14% 5%	2376
September	1st to 10th	Day	36% 9% 13% 19% 14% 9%	2160
	11th to 20th	Day	36% 9% 13% 18% 19% 5%	2033
	21st to end	Day	29% 6% 12% 19% 23% 11%	1980
October	1st to 10th	Day	19% 7% 10% 25% 20% 18%	1980
	11th to 20th	Day	24% 3 7% 18% 24% 23%	1900
	21st to end	Day	17% 3 4 16% 32% 29%	1980
November	1st to 10th	Day	17% 3 6% 20% 29% 25%	1774
	11th to 20th	Day	18% 4 8% 20% 28% 21%	1710
	21st to end	Day	24% 3 6% 16% 28% 22%	1710
December	1st to 10th	Day	24% 3 7% 20% 28% 18%	1710
	11th to 20th	Day	21% 4 7% 18% 30% 20%	2159
	21st to end	Day	15% 4 4 14% 31% 31%	3203
January	1st to 10th	Night	15% 3 4 9% 33% 36%	3788
	11th to 20th	Night	15% 3 5% 14% 31% 33%	3800
	21st to end	Night	25% 6% 6% 15% 34% 14%	4180
February	1st to 10th	Night	21% 4 7% 13% 23% 33%	2274
	11th to 20th	Night	26% 4 7% 12% 22% 29%	2098
	21st to end	Night	21% 3 5% 9% 27% 35%	1776
March	1st to 10th	Night	23% 4 6% 16% 27% 24%	2160
	11th to 20th	Night	27% 4 5% 13% 23% 28%	2079
	21st to end	Night	19% 4 7% 12% 26% 32%	1980
April	1st to 10th	Night	23% 5% 6% 12% 25% 29%	1800
	11th to 20th	Night	20% 5% 7% 14% 22% 31%	1777
	21st to end	Night	15% 5% 9% 14% 27% 30%	1800
May	1st to 10th	Night	19% 5% 8% 12% 24% 31%	1800
	11th to 20th	Night	26% 6% 10% 19% 20% 20%	1771
	21st to end	Night	22% 7% 14% 22% 18% 17%	1748
June	1st to 10th	Night	19% 8% 13% 28% 22% 10%	1620
	11th to 20th	Night	21% 7% 12% 21% 26% 13%	1620
	21st to end	Night	21% 7% 15% 21% 23% 13%	1620
July	1st to 10th	Night	26% 11% 20% 30% 11% 2	1702
	11th to 20th	Night	18% 7% 15% 30% 26% 4	1740
	21st to end	Night	19% 9% 20% 36% 15% 1	1859
August	1st to 10th	Night	15% 8% 17% 36% 23% 2	1779
	11th to 20th	Night	24% 11% 24% 29% 11% 2	1778
	21st to end	Night	27% 10% 19% 23% 16% 5%	1980
September	1st to 10th	Night	27% 7% 19% 23% 15% 8%	1800
	11th to 20th	Night	30% 9% 18% 21% 17% 6%	1926
	21st to end	Night	26% 8% 15% 21% 20% 10%	1980
October	1st to 10th	Night	20% 8% 15% 21% 19% 17%	1980
	11th to 20th	Night	25% 4 8% 19% 21% 23%	2056
	21st to end	Night	17% 3 5% 14% 30% 30%	2376
November	1st to 10th	Night	17% 4 5% 16% 33% 25%	2281
	11th to 20th	Night	19% 3 7% 20% 27% 24%	2470
	21st to end	Night	22% 4 7% 15% 28% 24%	2470
December	1st to 10th	Night	23% 4 6% 20% 26% 20%	2470
	11th to 20th	Night	24% 4 5% 17% 26% 24%	3037
	21st to end	Night	17% 4 5% 15% 35% 25%	4490

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	13% 20% 33% 24% 9% 1	270
	11th to 20th	Day	13% 13% 36% 26% 11% 1	270
	21st to end	Day	10% 25% 28% 26% 9% 2	297
February	1st to 10th	Day	11% 18% 33% 24% 12% 2	267
	11th to 20th	Day	15% 18% 38% 17% 10% 1	240
	21st to end	Day	12% 24% 38% 18% 8%	198
March	1st to 10th	Day	10% 13% 45% 23% 8% 1	240
	11th to 20th	Day	15% 18% 39% 18% 8% 2	316
	21st to end	Day	10% 23% 40% 21% 5%	462
April	1st to 10th	Day	8% 19% 45% 22% 6%	420
	11th to 20th	Day	8% 22% 43% 22% 5%	412
	21st to end	Day	10% 16% 47% 22% 4	420
May	1st to 10th	Day	4 17% 39% 29% 9% 1	423
	11th to 20th	Day	5% 8% 41% 33% 11% 2	448
	21st to end	Day	5% 6% 33% 43% 13% 1	670
June	1st to 10th	Day	3 3 21% 44% 25% 4	630
	11th to 20th	Day	3 2 16% 47% 29% 3	630
	21st to end	Day	5% 1 11% 38% 39% 5%	630
July	1st to 10th	Day	5% 1 9% 30% 42% 13%	486
	11th to 20th	Day	2 2 7% 35% 42% 13%	444
	21st to end	Day	3 7% 42% 37% 11%	487
August	1st to 10th	Day	3 1 5% 26% 50% 15%	447
	11th to 20th	Day	10% 1 9% 26% 37% 16%	437
	21st to end	Day	7% 1 6% 29% 43% 14%	495
September	1st to 10th	Day	9% 1 9% 36% 36% 9%	450
	11th to 20th	Day	9% 1 8% 33% 38% 11%	323
	21st to end	Day	9% 3 10% 32% 32% 14%	270
October	1st to 10th	Day	9% 3 18% 35% 29% 7%	270
	11th to 20th	Day	9% 7% 22% 37% 16% 8%	270
	21st to end	Day	9% 11% 27% 26% 19% 7%	297
November	1st to 10th	Day	11% 6% 26% 35% 17% 5%	270
	11th to 20th	Day	11% 9% 30% 27% 15% 7%	270
	21st to end	Day	17% 17% 26% 23% 13% 4	270
December	1st to 10th	Day	12% 11% 28% 31% 17% 1	270
	11th to 20th	Day	9% 18% 36% 27% 11% 1	270
	21st to end	Day	8% 19% 36% 26% 10% 1	297
January	1st to 10th	Night	9% 7% 28% 40% 14% 2	760
	11th to 20th	Night	9% 6% 29% 38% 16% 1	760
	21st to end	Night	7% 9% 32% 38% 13% 1	836
February	1st to 10th	Night	6% 11% 28% 37% 15% 2	758
	11th to 20th	Night	9% 7% 33% 40% 11%	704
	21st to end	Night	8% 12% 38% 35% 7%	592
March	1st to 10th	Night	7% 9% 34% 37% 12% 1	720
	11th to 20th	Night	8% 10% 36% 29% 14% 2	720
	21st to end	Night	5% 10% 39% 36% 9% 1	594
April	1st to 10th	Night	5% 11% 33% 42% 9%	540
	11th to 20th	Night	5% 10% 44% 34% 7%	533
	21st to end	Night	4 11% 36% 39% 8% 1	540
May	1st to 10th	Night	3 10% 35% 40% 12%	540
	11th to 20th	Night	6% 7% 30% 44% 12%	531
	21st to end	Night	4 7% 34% 40% 15%	584
June	1st to 10th	Night	3 2 27% 50% 17% 1	540
	11th to 20th	Night	2 2 27% 49% 19%	540
	21st to end	Night	3 2 19% 55% 20% 1	540
July	1st to 10th	Night	4 1 13% 49% 31% 2	525
	11th to 20th	Night	4 1 12% 52% 30% 2	522
	21st to end	Night	2 1 12% 49% 34% 3	591
August	1st to 10th	Night	2 1 8% 45% 41% 4	537
	11th to 20th	Night	4 1 6% 34% 48% 8%	534
	21st to end	Night	5% 7% 45% 40% 3	594
September	1st to 10th	Night	7% 1 7% 41% 37% 6%	540
	11th to 20th	Night	9% 9% 43% 36% 3	540
	21st to end	Night	8% 1 13% 40% 35% 4	540
October	1st to 10th	Night	4 2 17% 46% 29% 2	540
	11th to 20th	Night	8% 3 19% 45% 22% 3	616
	21st to end	Night	7% 5% 19% 37% 26% 7%	792
November	1st to 10th	Night	8% 2 20% 39% 26% 4	801
	11th to 20th	Night	5% 5% 19% 45% 23% 3	950
	21st to end	Night	7% 9% 25% 37% 19% 2	950
December	1st to 10th	Night	7% 5% 23% 44% 18% 2	950
	11th to 20th	Night	5% 10% 31% 40% 13% 1	950
	21st to end	Night	6% 10% 31% 39% 12% 2	1016

Page generated at 2024-02-07 05:11:53. Version ac07

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