Ghost Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ghost Ranch clear sky chart from 2005-11-06 to 2026-01-17.

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	2 3 2 4 4 4 5% 4 6% 8% 57%	135632
	Night	2 4 2 5% 4 4 4 4 6% 9% 57%	133544
Transparency	Day	22% 7% 10% 23% 25% 13%	130610
	Night	21% 7% 10% 23% 26% 13%	129569
Seeing	Day	9% 12% 25% 29% 19% 5%	16749
	Night	6% 7% 22% 41% 21% 2	26965

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	1 5% 4 7% 4 4 4 4 6% 8% 53%	4067
	11th to 20th	Day	1 3 2 5% 3 3 3 4 5% 8% 63%	4154
	21st to end	Day	1 5% 2 6% 5% 4 5% 4 6% 7% 55%	4510
February	1st to 10th	Day	1 6% 3 6% 3 3 4 4 5% 7% 58%	1800
	11th to 20th	Day	1 5% 2 7% 5% 3 4 5% 6% 8% 54%	1921
	21st to end	Day	1 7% 2 6% 3 4 4 4 6% 8% 55%	1650
March	1st to 10th	Day	1 5% 2 5% 5% 4 4 4 6% 8% 57%	4776
	11th to 20th	Day	3 6% 3 7% 4 5% 5% 4 6% 9% 48%	5000
	21st to end	Day	1 5% 2 5% 4 5% 5% 4 6% 8% 56%	5633
April	1st to 10th	Day	2 4 1 4 3 4 4 4 6% 7% 61%	2400
	11th to 20th	Day	2 4 1 4 4 4 4 4 5% 8% 60%	2371
	21st to end	Day	2 5% 1 3 4 3 4 4 5% 9% 60%	2400
May	1st to 10th	Day	3 3 2 4 3 4 5% 5% 7% 8% 55%	5440
	11th to 20th	Day	2 3 1 4 3 5% 5% 4 6% 7% 59%	5850
	21st to end	Day	1 2 1 2 2 3 3 3 6% 8% 68%	6925
June	1st to 10th	Day	2 2 1 3 3 4 4 4 7% 8% 61%	2800
	11th to 20th	Day	1 1 1 2 2 3 3 3 5% 7% 71%	2800
	21st to end	Day	3 3 2 4 4 4 5% 5% 7% 7% 59%	2800
July	1st to 10th	Day	1 2 1 3 3 5% 5% 5% 6% 7% 63%	6302
	11th to 20th	Day	1 1 1 3 4 6% 9% 8% 11% 11% 45%	5880
	21st to end	Day	2 3 2 6% 5% 6% 8% 7% 10% 11% 39%	6401
August	1st to 10th	Day	2 2 1 5% 5% 6% 7% 6% 9% 12% 44%	5745
	11th to 20th	Day	2 2 1 3 4 4 7% 6% 8% 10% 53%	5366
	21st to end	Day	3 3 1 5% 5% 6% 8% 6% 10% 11% 43%	5984
September	1st to 10th	Day	5% 4 2 5% 4 5% 5% 4 6% 8% 53%	2400
	11th to 20th	Day	4 4 1 4 4 4 4 4 6% 7% 58%	2400
	21st to end	Day	2 3 1 3 3 4 4 3 5% 6% 66%	2154
October	1st to 10th	Day	2 2 1 3 3 3 3 3 4 7% 69%	3270
	11th to 20th	Day	4 3 2 5% 4 4 4 4 5% 7% 59%	3250
	21st to end	Day	3 2 1 3 2 3 2 3 4 6% 72%	3548
November	1st to 10th	Day	1 3 1 3 2 2 3 2 4 7% 70%	1996
	11th to 20th	Day	1 2 1 3 2 2 2 3 6% 7% 70%	1890
	21st to end	Day	2 5% 3 4 4 4 4 3 5% 7% 61%	1851
December	1st to 10th	Day	1 2 2 3 2 2 2 2 3 7% 74%	2700
	11th to 20th	Day	1 4 1 4 3 2 3 3 5% 10% 61%	3106
	21st to end	Day	2 5% 2 5% 3 2 3 3 6% 7% 61%	4092
January	1st to 10th	Night	1 5% 3 8% 5% 4 5% 3 5% 10% 51%	6161
	11th to 20th	Night	1 4 2 5% 4 4 5% 4 6% 9% 57%	5958
	21st to end	Night	1 5% 3 7% 5% 4 5% 3 6% 11% 49%	6468
February	1st to 10th	Night	1 5% 2 5% 3 3 3 3 5% 9% 62%	2600
	11th to 20th	Night	3 7% 2 5% 3 3 4 4 6% 7% 57%	2364
	21st to end	Night	2 5% 2 5% 4 3 3 3 5% 7% 62%	1980
March	1st to 10th	Night	1 7% 2 5% 3 3 4 3 4 7% 61%	5094
	11th to 20th	Night	4 7% 2 6% 4 4 4 3 5% 7% 54%	5000
	21st to end	Night	2 4 2 5% 4 3 5% 4 5% 7% 60%	5334
April	1st to 10th	Night	1 4 1 4 4 3 5% 4 7% 8% 59%	2000
	11th to 20th	Night	2 5% 1 3 3 3 3 3 6% 7% 62%	1977
	21st to end	Night	2 4 1 3 3 3 4 4 6% 6% 63%	2000
May	1st to 10th	Night	4 5% 2 5% 4 4 5% 4 6% 7% 55%	4540
	11th to 20th	Night	3 3 1 5% 4 4 5% 4 7% 7% 58%	4044
	21st to end	Night	2 2 1 3 3 3 4 3 6% 7% 67%	3972
June	1st to 10th	Night	1 2 1 3 2 3 5% 3 7% 10% 62%	1600
	11th to 20th	Night	2 2 1 3 2 2 3 3 5% 5% 73%	1600
	21st to end	Night	3 3 2 4 3 4 5% 5% 7% 8% 55%	1600
July	1st to 10th	Night	1 2 1 5% 4 5% 5% 4 6% 7% 59%	3672
	11th to 20th	Night	1 2 1 5% 4 6% 8% 7% 12% 12% 43%	4100
	21st to end	Night	4 4 2 8% 5% 7% 7% 6% 10% 11% 36%	4472
August	1st to 10th	Night	3 3 2 7% 5% 6% 8% 6% 9% 10% 40%	4066
	11th to 20th	Night	2 3 1 6% 5% 5% 6% 6% 10% 13% 44%	4483
	21st to end	Night	4 4 2 8% 7% 8% 8% 7% 10% 10% 33%	4993
September	1st to 10th	Night	4 3 2 5% 5% 5% 6% 5% 7% 9% 50%	2000
	11th to 20th	Night	4 3 1 4 3 3 4 4 5% 9% 61%	2000
	21st to end	Night	4 3 2 4 3 3 3 3 4 6% 66%	2240
October	1st to 10th	Night	2 2 1 3 2 2 2 2 4 6% 72%	3920
	11th to 20th	Night	5% 3 2 5% 3 4 3 3 5% 6% 62%	3898
	21st to end	Night	2 1 1 2 2 2 3 2 4 6% 76%	4252
November	1st to 10th	Night	1 3 1 2 2 2 2 3 4 6% 73%	2500
	11th to 20th	Night	2 1 2 2 2 2 3 5% 6% 73%	2730
	21st to end	Night	2 6% 2 4 3 3 3 3 5% 8% 60%	2767
December	1st to 10th	Night	1 3 1 3 2 2 2 2 4 10% 71%	4710
	11th to 20th	Night	1 3 1 4 3 3 4 3 6% 11% 62%	5321
	21st to end	Night	2 5% 2 6% 4 4 4 3 6% 9% 56%	7128

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% 8% 9% 30% 27% 2	4068
	11th to 20th	Day	17% 6% 13% 27% 22% 16%	4154
	21st to end	Day	26% 8% 7% 20% 25% 14%	4510
February	1st to 10th	Day	26% 6% 11% 27% 22% 8%	1800
	11th to 20th	Day	28% 4 9% 26% 26% 7%	1931
	21st to end	Day	26% 5% 7% 18% 29% 14%	1650
March	1st to 10th	Day	21% 8% 4 20% 36% 11%	4776
	11th to 20th	Day	27% 9% 8% 24% 26% 6%	5000
	21st to end	Day	23% 7% 6% 34% 25% 5%	5633
April	1st to 10th	Day	20% 5% 8% 24% 29% 14%	2400
	11th to 20th	Day	22% 6% 6% 20% 30% 16%	2374
	21st to end	Day	21% 5% 8% 24% 31% 11%	2400
May	1st to 10th	Day	19% 10% 12% 20% 24% 15%	5440
	11th to 20th	Day	18% 9% 8% 16% 32% 16%	5853
	21st to end	Day	12% 7% 7% 18% 32% 24%	6926
June	1st to 10th	Day	18% 5% 11% 21% 25% 20%	2800
	11th to 20th	Day	13% 4 6% 15% 25% 37%	2800
	21st to end	Day	21% 6% 9% 19% 23% 22%	2800
July	1st to 10th	Day	18% 7% 9% 13% 19% 34%	6234
	11th to 20th	Day	24% 11% 21% 29% 9% 7%	5811
	21st to end	Day	30% 10% 21% 23% 12% 4	6217
August	1st to 10th	Day	33% 12% 20% 19% 9% 6%	4185
	11th to 20th	Day	23% 8% 17% 20% 17% 14%	3882
	21st to end	Day	31% 11% 18% 21% 16% 4	4311
September	1st to 10th	Day	28% 6% 12% 23% 21% 11%	2400
	11th to 20th	Day	24% 6% 10% 17% 29% 15%	2400
	21st to end	Day	19% 4 7% 20% 36% 14%	2154
October	1st to 10th	Day	16% 4 6% 16% 34% 24%	3270
	11th to 20th	Day	23% 7% 6% 19% 33% 13%	3250
	21st to end	Day	14% 5% 5% 23% 39% 14%	3548
November	1st to 10th	Day	15% 3 7% 27% 36% 12%	1996
	11th to 20th	Day	14% 3 8% 31% 36% 7%	1890
	21st to end	Day	24% 4 6% 26% 30% 10%	1851
December	1st to 10th	Day	13% 3 9% 33% 35% 8%	2700
	11th to 20th	Day	19% 4 8% 33% 31% 4	3104
	21st to end	Day	21% 5% 11% 28% 27% 7%	4092
January	1st to 10th	Night	25% 7% 8% 30% 25% 5%	6161
	11th to 20th	Night	17% 9% 10% 28% 21% 15%	5958
	21st to end	Night	25% 7% 8% 24% 29% 8%	6468
February	1st to 10th	Night	21% 4 13% 29% 25% 9%	2600
	11th to 20th	Night	25% 6% 8% 28% 25% 7%	2364
	21st to end	Night	22% 5% 6% 21% 35% 12%	1980
March	1st to 10th	Night	20% 7% 4 18% 38% 13%	5094
	11th to 20th	Night	25% 8% 6% 22% 29% 10%	5000
	21st to end	Night	17% 10% 7% 35% 25% 5%	5334
April	1st to 10th	Night	21% 6% 8% 23% 28% 14%	2000
	11th to 20th	Night	21% 5% 6% 20% 31% 17%	1977
	21st to end	Night	19% 6% 7% 22% 32% 13%	2000
May	1st to 10th	Night	23% 10% 9% 18% 24% 16%	4537
	11th to 20th	Night	19% 10% 9% 20% 24% 18%	4045
	21st to end	Night	13% 8% 7% 14% 25% 33%	3972
June	1st to 10th	Night	18% 6% 14% 18% 24% 22%	1600
	11th to 20th	Night	13% 4 6% 12% 27% 38%	1600
	21st to end	Night	24% 7% 10% 14% 20% 25%	1600
July	1st to 10th	Night	23% 8% 12% 9% 12% 36%	3632
	11th to 20th	Night	25% 10% 27% 23% 6% 10%	4046
	21st to end	Night	36% 10% 21% 21% 11% 1	4344
August	1st to 10th	Night	40% 12% 19% 13% 8% 8%	2950
	11th to 20th	Night	29% 9% 21% 14% 11% 16%	3243
	21st to end	Night	37% 13% 17% 16% 12% 5%	3597
September	1st to 10th	Night	28% 8% 14% 21% 18% 12%	2000
	11th to 20th	Night	20% 7% 11% 17% 24% 22%	2000
	21st to end	Night	19% 5% 8% 18% 33% 18%	2240
October	1st to 10th	Night	15% 4 6% 15% 37% 24%	3920
	11th to 20th	Night	22% 6% 6% 17% 31% 18%	3898
	21st to end	Night	11% 3 4 25% 38% 18%	4252
November	1st to 10th	Night	12% 4 5% 28% 39% 12%	2500
	11th to 20th	Night	12% 3 7% 31% 37% 9%	2730
	21st to end	Night	23% 4 7% 24% 31% 11%	2767
December	1st to 10th	Night	14% 3 7% 33% 38% 6%	4710
	11th to 20th	Night	16% 5% 8% 33% 34% 4	5322
	21st to end	Night	23% 6% 11% 27% 31% 3	7128

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	12% 17% 30% 29% 10% 2	330
	11th to 20th	Day	14% 14% 28% 28% 13% 2	318
	21st to end	Day	8% 12% 28% 34% 14% 5%	330
February	1st to 10th	Day	13% 19% 26% 32% 9% 1	300
	11th to 20th	Day	11% 21% 31% 28% 9%	300
	21st to end	Day	20% 20% 29% 23% 7% 1	249
March	1st to 10th	Day	16% 22% 29% 22% 10% 1	420
	11th to 20th	Day	19% 21% 28% 21% 9% 3	500
	21st to end	Day	22% 23% 31% 16% 6% 1	550
April	1st to 10th	Day	15% 25% 31% 19% 9% 1	500
	11th to 20th	Day	15% 30% 31% 17% 6% 1	492
	21st to end	Day	13% 24% 36% 20% 7%	500
May	1st to 10th	Day	14% 20% 35% 20% 10% 1	503
	11th to 20th	Day	10% 16% 32% 25% 13% 3	572
	21st to end	Day	8% 13% 29% 31% 17% 2	789
June	1st to 10th	Day	4 7% 25% 35% 26% 2	730
	11th to 20th	Day	4 8% 28% 32% 23% 5%	730
	21st to end	Day	6% 5% 24% 33% 27% 5%	730
July	1st to 10th	Day	4 4 16% 35% 33% 8%	710
	11th to 20th	Day	2 2 11% 33% 37% 15%	524
	21st to end	Day	5% 3 10% 31% 36% 15%	575
August	1st to 10th	Day	4 5% 13% 34% 30% 13%	527
	11th to 20th	Day	6% 5% 16% 34% 31% 9%	517
	21st to end	Day	5% 3 13% 39% 30% 10%	583
September	1st to 10th	Day	6% 3 17% 35% 29% 9%	530
	11th to 20th	Day	6% 7% 23% 37% 19% 8%	530
	21st to end	Day	5% 9% 24% 30% 22% 10%	374
October	1st to 10th	Day	6% 10% 23% 27% 25% 8%	330
	11th to 20th	Day	10% 15% 26% 23% 18% 9%	330
	21st to end	Day	11% 11% 25% 28% 18% 7%	363
November	1st to 10th	Day	9% 12% 29% 28% 17% 4	330
	11th to 20th	Day	7% 9% 28% 33% 19% 4	330
	21st to end	Day	13% 11% 34% 23% 13% 7%	330
December	1st to 10th	Day	12% 14% 28% 26% 15% 5%	330
	11th to 20th	Day	11% 14% 26% 29% 18% 2	330
	21st to end	Day	15% 21% 24% 28% 9% 1	363
January	1st to 10th	Night	6% 10% 26% 40% 16% 2	913
	11th to 20th	Night	5% 8% 28% 40% 17% 2	824
	21st to end	Night	5% 9% 28% 41% 16% 2	880
February	1st to 10th	Night	7% 9% 30% 41% 11% 1	800
	11th to 20th	Night	9% 10% 33% 37% 10% 1	784
	21st to end	Night	9% 10% 38% 37% 6%	660
March	1st to 10th	Night	7% 10% 33% 40% 10% 1	800
	11th to 20th	Night	9% 9% 25% 41% 15% 1	800
	21st to end	Night	10% 10% 32% 36% 11%	815
April	1st to 10th	Night	8% 14% 34% 36% 7%	600
	11th to 20th	Night	10% 14% 28% 36% 12%	593
	21st to end	Night	6% 13% 30% 42% 9%	600
May	1st to 10th	Night	8% 7% 28% 42% 15%	600
	11th to 20th	Night	7% 6% 27% 40% 19% 2	591
	21st to end	Night	4 8% 28% 43% 16% 1	650
June	1st to 10th	Night	3 4 17% 50% 24% 1	600
	11th to 20th	Night	3 4 22% 51% 20% 1	600
	21st to end	Night	5% 4 14% 44% 32% 1	600
July	1st to 10th	Night	3 3 8% 43% 41% 2	585
	11th to 20th	Night	3 1 3 34% 52% 6%	582
	21st to end	Night	5% 2 3 28% 53% 9%	657
August	1st to 10th	Night	4 3 5% 28% 50% 11%	597
	11th to 20th	Night	4 3 4 40% 43% 5%	594
	21st to end	Night	5% 3 5% 38% 45% 5%	660
September	1st to 10th	Night	5% 1 7% 45% 38% 4	600
	11th to 20th	Night	6% 2 10% 47% 32% 3	600
	21st to end	Night	6% 3 14% 45% 29% 3	685
October	1st to 10th	Night	6% 3 18% 48% 23% 2	800
	11th to 20th	Night	5% 5% 20% 45% 20% 4	800
	21st to end	Night	7% 5% 22% 40% 21% 5%	880
November	1st to 10th	Night	3 5% 22% 49% 19% 3	860
	11th to 20th	Night	5% 7% 24% 43% 18% 3	1050
	21st to end	Night	9% 9% 24% 36% 19% 3	1050
December	1st to 10th	Night	8% 9% 30% 40% 12% 1	1050
	11th to 20th	Night	9% 12% 26% 37% 15% 1	1050
	21st to end	Night	10% 12% 29% 39% 9% 1	1155

Page generated at 2026-01-13 23:14:25. Version ac07

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