Eldorado Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eldorado Star Party clear sky chart from 2005-11-06 to 2024-03-18.

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% 4 2 4 4 2 4 4 5% 7% 56%	79240
	Night	8% 4 2 3 3 2 3 4 5% 7% 59%	80608
Transparency	Day	28% 5% 10% 21% 23% 13%	78972
	Night	25% 5% 10% 21% 23% 15%	80397
Seeing	Day	9% 6% 24% 32% 23% 6%	13921
	Night	9% 6% 31% 40% 14% 1	24085

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	9% 5% 2 3 3 2 3 2 3 6% 63%	2847
	11th to 20th	Day	7% 5% 2 3 2 1 2 3 3 6% 66%	3056
	21st to end	Day	9% 6% 2 5% 5% 2 4 3 4 6% 54%	3487
February	1st to 10th	Day	9% 5% 2 5% 3 2 3 3 3 7% 57%	1900
	11th to 20th	Day	10% 5% 2 5% 4 3 3 4 3 6% 56%	1849
	21st to end	Day	10% 4 2 3 3 2 4 4 5% 6% 58%	1570
March	1st to 10th	Day	11% 6% 2 6% 4 3 4 4 4 7% 49%	1900
	11th to 20th	Day	13% 5% 2 4 4 2 4 4 5% 6% 51%	2038
	21st to end	Day	9% 5% 2 4 3 2 3 3 3 5% 61%	2178
April	1st to 10th	Day	8% 3 2 4 4 2 3 3 5% 7% 58%	2122
	11th to 20th	Day	10% 4 2 4 4 3 3 4 4 6% 56%	2134
	21st to end	Day	10% 4 2 4 3 2 2 3 3 6% 60%	2160
May	1st to 10th	Day	10% 4 2 4 4 2 3 3 6% 8% 54%	2288
	11th to 20th	Day	11% 5% 2 5% 5% 3 4 4 5% 8% 49%	2302
	21st to end	Day	11% 5% 3 5% 5% 3 4 4 5% 7% 48%	2531
June	1st to 10th	Day	4 2 2 3 3 2 4 5% 5% 9% 61%	2340
	11th to 20th	Day	6% 4 1 3 3 2 4 4 6% 7% 60%	2340
	21st to end	Day	7% 4 2 4 4 3 4 6% 6% 7% 54%	2340
July	1st to 10th	Day	8% 5% 2 5% 6% 4 7% 6% 7% 8% 44%	2340
	11th to 20th	Day	3 2 2 3 3 3 4 5% 6% 8% 62%	2340
	21st to end	Day	3 2 2 3 4 3 5% 5% 5% 8% 60%	2438
August	1st to 10th	Day	2 1 1 2 3 2 4 5% 4 8% 67%	2149
	11th to 20th	Day	6% 3 2 4 6% 4 5% 5% 6% 8% 51%	2123
	21st to end	Day	6% 3 2 4 6% 3 5% 5% 5% 10% 48%	2376
September	1st to 10th	Day	11% 5% 2 5% 5% 3 5% 5% 5% 7% 47%	2057
	11th to 20th	Day	12% 5% 3 5% 6% 3 5% 5% 5% 7% 45%	1980
	21st to end	Day	9% 3 2 4 4 4 4 4 5% 7% 54%	1980
October	1st to 10th	Day	6% 3 1 4 4 2 4 3 5% 7% 58%	1980
	11th to 20th	Day	11% 4 2 3 4 1 3 4 4 5% 60%	1980
	21st to end	Day	12% 4 2 3 2 1 2 2 3 4 63%	2016
November	1st to 10th	Day	10% 5% 2 4 3 2 2 3 4 8% 57%	1673
	11th to 20th	Day	7% 5% 1 4 3 3 4 4 5% 5% 60%	1710
	21st to end	Day	11% 6% 3 4 3 2 3 3 4 7% 54%	1710
December	1st to 10th	Day	13% 5% 2 4 4 2 3 4 4 5% 55%	1710
	11th to 20th	Day	10% 6% 2 4 3 2 4 4 5% 6% 54%	2161
	21st to end	Day	10% 6% 2 3 2 1 2 2 3 4 64%	3135
January	1st to 10th	Night	7% 4 2 4 4 2 3 3 4 5% 63%	4108
	11th to 20th	Night	6% 5% 2 3 2 1 2 2 3 5% 69%	3928
	21st to end	Night	12% 6% 2 4 3 2 3 3 4 7% 54%	4180
February	1st to 10th	Night	8% 6% 3 3 3 2 3 3 4 7% 58%	2280
	11th to 20th	Night	12% 6% 2 4 3 3 4 3 4 5% 54%	2218
	21st to end	Night	8% 5% 2 3 3 2 3 4 6% 6% 58%	1884
March	1st to 10th	Night	10% 5% 1 4 3 2 4 5% 5% 7% 53%	2280
	11th to 20th	Night	12% 5% 3 4 3 2 4 3 4 6% 54%	2087
	21st to end	Night	7% 4 1 4 3 2 4 3 5% 6% 60%	2178
April	1st to 10th	Night	6% 3 2 4 3 2 4 4 5% 8% 59%	1833
	11th to 20th	Night	11% 4 1 3 3 2 4 4 5% 6% 58%	1777
	21st to end	Night	9% 3 2 2 3 2 2 3 4 4 65%	1800
May	1st to 10th	Night	6% 3 2 4 4 2 4 4 5% 8% 57%	1670
	11th to 20th	Night	9% 4 2 4 5% 2 4 5% 5% 8% 52%	1593
	21st to end	Night	8% 4 2 3 3 2 3 4 6% 8% 54%	1745
June	1st to 10th	Night	3 2 1 2 3 2 4 5% 6% 11% 63%	1620
	11th to 20th	Night	2 1 1 2 3 2 4 4 6% 10% 64%	1620
	21st to end	Night	5% 3 1 3 4 2 4 4 5% 9% 61%	1620
July	1st to 10th	Night	5% 4 2 5% 4 3 4 4 7% 11% 50%	1620
	11th to 20th	Night	3 1 1 2 1 2 3 3 5% 8% 71%	1620
	21st to end	Night	1 2 1 2 3 1 3 3 6% 12% 66%	1876
August	1st to 10th	Night	2 1 1 2 2 2 3 3 4 7% 73%	1790
	11th to 20th	Night	5% 2 2 3 4 4 4 5% 7% 11% 53%	1778
	21st to end	Night	5% 3 1 3 4 2 4 6% 7% 12% 52%	1980
September	1st to 10th	Night	7% 3 3 4 4 2 4 4 5% 8% 56%	1903
	11th to 20th	Night	9% 4 1 5% 4 3 3 4 7% 9% 51%	1980
	21st to end	Night	7% 4 1 3 3 2 4 4 6% 9% 57%	1980
October	1st to 10th	Night	5% 4 1 3 3 2 3 3 4 7% 64%	1980
	11th to 20th	Night	11% 4 2 3 3 1 3 3 3 4 63%	1980
	21st to end	Night	9% 4 2 4 3 2 2 3 3 4 65%	2317
November	1st to 10th	Night	9% 5% 2 3 3 2 3 3 3 5% 62%	2405
	11th to 20th	Night	7% 5% 2 4 4 2 2 3 4 5% 63%	2470
	21st to end	Night	11% 5% 2 4 3 2 4 4 5% 5% 56%	2470
December	1st to 10th	Night	9% 6% 2 3 3 2 3 3 5% 6% 59%	2470
	11th to 20th	Night	10% 6% 2 6% 4 2 4 3 4 6% 53%	3036
	21st to end	Night	10% 7% 2 3 3 1 2 3 3 6% 59%	4532

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% 3 4 16% 27% 26%	2848
	11th to 20th	Day	21% 3 7% 16% 33% 19%	3056
	21st to end	Day	31% 4 7% 17% 29% 12%	3487
February	1st to 10th	Day	30% 3 6% 15% 24% 22%	1900
	11th to 20th	Day	32% 3 5% 19% 22% 18%	1859
	21st to end	Day	27% 4 5% 13% 29% 22%	1570
March	1st to 10th	Day	35% 5% 6% 16% 21% 16%	1900
	11th to 20th	Day	35% 5% 7% 15% 20% 19%	2038
	21st to end	Day	28% 3 8% 19% 22% 21%	2178
April	1st to 10th	Day	27% 4 7% 20% 23% 19%	2122
	11th to 20th	Day	30% 4 8% 17% 21% 19%	2134
	21st to end	Day	28% 3 8% 21% 23% 17%	2160
May	1st to 10th	Day	30% 5% 9% 17% 25% 15%	2288
	11th to 20th	Day	34% 5% 10% 22% 20% 8%	2306
	21st to end	Day	36% 6% 11% 24% 18% 6%	2531
June	1st to 10th	Day	20% 7% 12% 32% 23% 6%	2340
	11th to 20th	Day	23% 5% 12% 26% 25% 9%	2340
	21st to end	Day	27% 8% 13% 24% 22% 7%	2340
July	1st to 10th	Day	36% 9% 18% 25% 11% 2	2276
	11th to 20th	Day	20% 7% 14% 31% 24% 5%	2271
	21st to end	Day	18% 7% 21% 35% 18% 1	2303
August	1st to 10th	Day	17% 5% 14% 36% 24% 3	2136
	11th to 20th	Day	29% 8% 18% 28% 14% 3	2123
	21st to end	Day	31% 8% 16% 24% 17% 4	2376
September	1st to 10th	Day	37% 6% 12% 20% 18% 7%	2057
	11th to 20th	Day	37% 7% 13% 19% 19% 5%	1980
	21st to end	Day	29% 6% 12% 20% 22% 12%	1980
October	1st to 10th	Day	25% 6% 12% 24% 23% 11%	1980
	11th to 20th	Day	28% 4 7% 17% 24% 20%	1980
	21st to end	Day	27% 3 5% 14% 30% 20%	2016
November	1st to 10th	Day	28% 4 10% 22% 21% 15%	1673
	11th to 20th	Day	26% 4 10% 18% 22% 19%	1710
	21st to end	Day	32% 3 5% 17% 26% 16%	1710
December	1st to 10th	Day	32% 4 6% 19% 26% 13%	1710
	11th to 20th	Day	32% 4 8% 15% 23% 19%	2159
	21st to end	Day	27% 2 4 17% 28% 23%	3135
January	1st to 10th	Night	23% 4 5% 14% 29% 24%	4108
	11th to 20th	Night	20% 3 4 20% 27% 26%	3928
	21st to end	Night	31% 4 6% 17% 27% 15%	4180
February	1st to 10th	Night	28% 3 8% 15% 26% 21%	2280
	11th to 20th	Night	32% 4 5% 17% 22% 20%	2218
	21st to end	Night	26% 4 7% 14% 26% 24%	1884
March	1st to 10th	Night	30% 4 9% 17% 25% 15%	2280
	11th to 20th	Night	33% 5% 6% 16% 20% 21%	2087
	21st to end	Night	25% 5% 11% 21% 18% 21%	2178
April	1st to 10th	Night	24% 5% 11% 22% 18% 21%	1833
	11th to 20th	Night	28% 4 9% 20% 18% 21%	1777
	21st to end	Night	23% 5% 10% 24% 22% 16%	1800
May	1st to 10th	Night	25% 5% 11% 23% 22% 14%	1670
	11th to 20th	Night	31% 7% 12% 24% 19% 7%	1594
	21st to end	Night	27% 7% 15% 26% 21% 4	1746
June	1st to 10th	Night	16% 7% 18% 32% 23% 4	1620
	11th to 20th	Night	15% 7% 14% 33% 24% 8%	1620
	21st to end	Night	21% 6% 13% 29% 23% 7%	1620
July	1st to 10th	Night	25% 9% 21% 27% 15% 2	1575
	11th to 20th	Night	13% 7% 13% 32% 29% 7%	1566
	21st to end	Night	10% 6% 23% 39% 21% 1	1772
August	1st to 10th	Night	11% 5% 14% 36% 30% 4	1779
	11th to 20th	Night	22% 9% 16% 32% 17% 4	1778
	21st to end	Night	24% 9% 20% 25% 17% 5%	1980
September	1st to 10th	Night	26% 7% 13% 25% 21% 8%	1903
	11th to 20th	Night	28% 8% 16% 21% 21% 5%	1980
	21st to end	Night	23% 7% 13% 25% 17% 15%	1980
October	1st to 10th	Night	20% 5% 13% 26% 22% 13%	1980
	11th to 20th	Night	27% 3 8% 18% 25% 18%	1980
	21st to end	Night	25% 3 6% 17% 26% 24%	2317
November	1st to 10th	Night	26% 3 9% 19% 25% 17%	2405
	11th to 20th	Night	25% 3 7% 21% 24% 20%	2470
	21st to end	Night	30% 4 7% 16% 24% 19%	2470
December	1st to 10th	Night	27% 3 9% 21% 23% 16%	2470
	11th to 20th	Night	33% 4 6% 16% 21% 20%	3037
	21st to end	Night	28% 3 5% 14% 29% 21%	4532

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% 8% 42% 29% 7% 2	270
	11th to 20th	Day	15% 10% 32% 28% 13% 2	270
	21st to end	Day	9% 11% 38% 29% 12%	297
February	1st to 10th	Day	18% 11% 35% 23% 11% 2	270
	11th to 20th	Day	14% 10% 44% 25% 6% 1	270
	21st to end	Day	13% 12% 49% 21% 5%	225
March	1st to 10th	Day	13% 11% 44% 26% 6%	270
	11th to 20th	Day	16% 13% 36% 23% 11% 1	261
	21st to end	Day	11% 16% 41% 25% 6%	264
April	1st to 10th	Day	9% 14% 44% 27% 7%	382
	11th to 20th	Day	11% 18% 38% 27% 6%	412
	21st to end	Day	9% 15% 42% 27% 7%	420
May	1st to 10th	Day	9% 9% 38% 35% 9%	551
	11th to 20th	Day	14% 7% 33% 32% 13% 2	625
	21st to end	Day	11% 6% 30% 40% 11% 1	679
June	1st to 10th	Day	4 3 18% 46% 26% 2	630
	11th to 20th	Day	6% 2 20% 48% 21% 3	630
	21st to end	Day	5% 2 11% 45% 31% 6%	630
July	1st to 10th	Day	6% 1 8% 37% 40% 9%	621
	11th to 20th	Day	2 1 4 40% 45% 8%	618
	21st to end	Day	2 3 33% 46% 15%	576
August	1st to 10th	Day	2 1 4 28% 50% 15%	447
	11th to 20th	Day	8% 2 27% 45% 17%	437
	21st to end	Day	5% 1 6% 27% 40% 21%	495
September	1st to 10th	Day	9% 3 28% 41% 18%	347
	11th to 20th	Day	7% 2 6% 24% 44% 17%	270
	21st to end	Day	12% 1 6% 26% 40% 16%	270
October	1st to 10th	Day	3 1 17% 37% 35% 6%	270
	11th to 20th	Day	13% 3 20% 40% 22% 1	270
	21st to end	Day	15% 7% 30% 26% 20% 2	297
November	1st to 10th	Day	14% 7% 29% 33% 16% 3	270
	11th to 20th	Day	14% 10% 23% 31% 18% 4	270
	21st to end	Day	16% 14% 36% 20% 11% 3	270
December	1st to 10th	Day	15% 8% 26% 33% 15% 3	270
	11th to 20th	Day	13% 11% 37% 26% 12% 2	270
	21st to end	Day	13% 9% 39% 29% 10%	297
January	1st to 10th	Night	11% 6% 38% 37% 7%	950
	11th to 20th	Night	12% 8% 33% 38% 8%	836
	21st to end	Night	12% 9% 38% 33% 8%	836
February	1st to 10th	Night	12% 11% 40% 31% 6%	760
	11th to 20th	Night	15% 10% 42% 30% 4	744
	21st to end	Night	12% 12% 49% 26% 2	628
March	1st to 10th	Night	13% 11% 46% 26% 4	760
	11th to 20th	Night	14% 11% 40% 31% 4	583
	21st to end	Night	8% 11% 54% 25% 2	594
April	1st to 10th	Night	6% 9% 53% 29% 3	540
	11th to 20th	Night	10% 9% 52% 26% 4	533
	21st to end	Night	7% 10% 54% 25% 4	540
May	1st to 10th	Night	5% 8% 53% 29% 4	540
	11th to 20th	Night	9% 7% 42% 34% 8%	531
	21st to end	Night	9% 4 41% 35% 9% 1	584
June	1st to 10th	Night	2 2 25% 60% 10% 1	540
	11th to 20th	Night	2 1 36% 53% 8%	540
	21st to end	Night	4 2 17% 56% 20% 1	540
July	1st to 10th	Night	6% 1 9% 56% 27% 2	525
	11th to 20th	Night	3 7% 62% 27% 1	522
	21st to end	Night	1 1 4 62% 31% 1	591
August	1st to 10th	Night	1 5% 54% 38% 2	537
	11th to 20th	Night	6% 1 6% 48% 37% 3	534
	21st to end	Night	4 1 6% 45% 39% 5%	594
September	1st to 10th	Night	5% 1 8% 47% 35% 4	540
	11th to 20th	Night	8% 1 9% 47% 33% 2	540
	21st to end	Night	7% 1 14% 48% 27% 2	540
October	1st to 10th	Night	5% 2 21% 51% 21%	540
	11th to 20th	Night	12% 4 26% 44% 13% 1	540
	21st to end	Night	9% 6% 29% 38% 17% 2	733
November	1st to 10th	Night	11% 3 28% 40% 16% 1	925
	11th to 20th	Night	8% 5% 33% 39% 14% 1	950
	21st to end	Night	14% 7% 32% 34% 12% 1	950
December	1st to 10th	Night	12% 5% 29% 42% 10% 1	950
	11th to 20th	Night	13% 8% 35% 36% 7%	950
	21st to end	Night	11% 6% 39% 35% 9% 1	1045

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