Ghost Pine Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ghost Pine Observatory clear sky chart from 2005-11-06 to 2025-12-03.

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 1 3 2 2 3 2 4 5% 69%	135719
	Night	6% 3 1 3 2 3 3 3 4 6% 66%	132393
Transparency	Day	19% 4 7% 19% 26% 25%	130623
	Night	22% 5% 9% 18% 24% 23%	128489
Seeing	Day	8% 8% 19% 27% 27% 11%	16650
	Night	8% 6% 18% 34% 30% 5%	25912

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	11% 7% 2 5% 3 4 4 3 5% 7% 50%	3731
	11th to 20th	Day	12% 6% 3 5% 3 3 3 2 3 5% 56%	4100
	21st to end	Day	16% 7% 2 5% 3 3 3 2 4 5% 50%	4510
February	1st to 10th	Day	14% 6% 1 4 4 4 3 4 5% 6% 50%	1800
	11th to 20th	Day	10% 6% 2 6% 5% 4 4 3 5% 7% 48%	1812
	21st to end	Day	10% 4 2 5% 4 4 4 4 5% 7% 52%	1650
March	1st to 10th	Day	10% 8% 3 7% 4 5% 5% 4 6% 8% 42%	4855
	11th to 20th	Day	8% 7% 2 6% 4 3 4 3 5% 6% 53%	5000
	21st to end	Day	10% 6% 2 6% 5% 5% 6% 5% 7% 8% 42%	5569
April	1st to 10th	Day	9% 6% 2 6% 4 4 5% 3 5% 8% 47%	2400
	11th to 20th	Day	7% 3 1 4 3 3 3 3 5% 7% 59%	2369
	21st to end	Day	3 3 1 3 3 3 3 3 6% 8% 63%	2400
May	1st to 10th	Day	3 2 1 2 1 1 2 1 3 5% 79%	5744
	11th to 20th	Day	1 1 2 1 1 2 2 4 5% 79%	6101
	21st to end	Day	1 1 1 1 1 2 2 3 5% 82%	6902
June	1st to 10th	Day	4 2 1 2 2 3 3 3 5% 7% 68%	2800
	11th to 20th	Day	1 1 2 2 1 2 2 4 5% 81%	2800
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	2800
July	1st to 10th	Day	1 1 1 1 1 1 2 93%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 91%	6103
	21st to end	Day	1 1 1 1 1 2 3 89%	6402
August	1st to 10th	Day	1 1 1 1 1 2 2 4 3 84%	5777
	11th to 20th	Day	1 1 1 1 2 3 92%	5589
	21st to end	Day	1 1 1 1 1 1 1 2 3 86%	5984
September	1st to 10th	Day	1 1 2 1 1 2 4 88%	2400
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 78%	2400
	21st to end	Day	3 1 1 2 1 2 2 1 3 5% 80%	2116
October	1st to 10th	Day	2 2 1 3 2 2 2 2 4 5% 77%	3280
	11th to 20th	Day	3 3 1 2 2 2 2 2 4 4 74%	3261
	21st to end	Day	4 2 1 4 3 3 4 3 5% 6% 65%	3558
November	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 8% 60%	1975
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 6% 7% 50%	1864
	21st to end	Day	7% 5% 2 4 3 3 3 3 4 6% 60%	1680
December	1st to 10th	Day	7% 4 1 3 3 3 3 3 6% 9% 59%	2636
	11th to 20th	Day	20% 9% 3 7% 4 4 4 3 7% 8% 32%	3028
	21st to end	Day	16% 10% 3 6% 4 3 5% 5% 6% 8% 34%	4004
January	1st to 10th	Night	9% 5% 2 4 3 4 4 4 7% 9% 50%	6203
	11th to 20th	Night	10% 6% 2 5% 3 4 3 3 4 4 55%	5880
	21st to end	Night	13% 6% 2 6% 4 3 4 3 4 5% 50%	6468
February	1st to 10th	Night	12% 5% 2 5% 4 3 4 4 5% 6% 51%	2600
	11th to 20th	Night	9% 5% 2 4 4 4 4 4 6% 9% 50%	2473
	21st to end	Night	9% 4 2 4 3 3 3 3 5% 6% 57%	1980
March	1st to 10th	Night	7% 7% 2 6% 4 4 4 4 6% 8% 48%	5036
	11th to 20th	Night	9% 5% 1 4 3 3 4 3 5% 6% 56%	5000
	21st to end	Night	10% 5% 2 5% 4 4 4 4 6% 9% 46%	5404
April	1st to 10th	Night	5% 5% 2 6% 4 4 4 4 5% 6% 56%	2000
	11th to 20th	Night	6% 3 1 4 3 2 3 3 5% 6% 64%	1979
	21st to end	Night	4 3 1 2 2 2 3 3 4 7% 70%	2000
May	1st to 10th	Night	3 1 2 2 2 2 2 3 6% 79%	4238
	11th to 20th	Night	1 1 1 2 2 2 2 2 4 5% 79%	3786
	21st to end	Night	1 1 1 1 1 1 1 3 4 87%	3972
June	1st to 10th	Night	4 2 2 2 2 3 3 5% 6% 72%	1600
	11th to 20th	Night	1 1 1 1 1 2 1 3 4 85%	1600
	21st to end	Night	1 1 1 1 1 2 2 2 2 3 85%	1600
July	1st to 10th	Night	1 1 1 1 1 2 93%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 1 1 91%	3862
	21st to end	Night	1 1 1 1 2 2 3 4 87%	4472
August	1st to 10th	Night	2 1 1 1 1 2 2 3 3 85%	4035
	11th to 20th	Night	1 1 1 1 1 2 93%	4254
	21st to end	Night	1 1 1 1 1 2 1 2 3 86%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 2 4 89%	2000
	11th to 20th	Night	2 2 1 3 2 1 2 1 3 4 80%	2000
	21st to end	Night	1 1 1 1 1 2 1 3 5% 84%	2278
October	1st to 10th	Night	2 1 1 2 2 2 3 2 3 4 79%	3920
	11th to 20th	Night	2 1 1 2 1 2 3 2 3 5% 78%	3897
	21st to end	Night	4 2 1 3 2 3 3 3 5% 7% 68%	4253
November	1st to 10th	Night	6% 3 1 3 3 3 3 3 6% 8% 60%	2541
	11th to 20th	Night	9% 4 1 4 3 3 4 3 6% 7% 56%	2751
	21st to end	Night	7% 4 2 4 3 3 3 3 4 6% 60%	2940
December	1st to 10th	Night	7% 3 1 3 2 3 3 3 5% 7% 60%	4588
	11th to 20th	Night	17% 8% 2 5% 3 4 5% 4 7% 9% 35%	5176
	21st to end	Night	16% 10% 3 8% 5% 5% 4 4 5% 6% 34%	6952

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	34% 10% 15% 22% 12% 6%	3731
	11th to 20th	Day	34% 5% 7% 16% 22% 16%	4100
	21st to end	Day	37% 6% 8% 13% 14% 22%	4510
February	1st to 10th	Day	36% 5% 10% 20% 20% 9%	1800
	11th to 20th	Day	35% 5% 12% 19% 21% 8%	1821
	21st to end	Day	33% 6% 9% 24% 20% 8%	1650
March	1st to 10th	Day	38% 9% 9% 17% 22% 5%	4855
	11th to 20th	Day	32% 5% 13% 24% 18% 9%	5000
	21st to end	Day	35% 10% 15% 24% 13% 2	5569
April	1st to 10th	Day	35% 6% 12% 21% 19% 6%	2400
	11th to 20th	Day	24% 7% 13% 22% 24% 10%	2372
	21st to end	Day	19% 5% 14% 28% 26% 8%	2400
May	1st to 10th	Day	10% 3 7% 23% 31% 27%	5744
	11th to 20th	Day	8% 4 6% 26% 40% 17%	6104
	21st to end	Day	7% 3 8% 28% 41% 14%	6904
June	1st to 10th	Day	16% 5% 10% 27% 30% 12%	2800
	11th to 20th	Day	7% 3 8% 19% 35% 27%	2800
	21st to end	Day	6% 2 3 13% 36% 40%	2800
July	1st to 10th	Day	3 1 1 7% 20% 68%	6251
	11th to 20th	Day	4 1 1 5% 14% 74%	6028
	21st to end	Day	3 1 3 18% 27% 47%	6217
August	1st to 10th	Day	9% 2 3 9% 26% 51%	4206
	11th to 20th	Day	3 1 2 9% 43% 43%	4048
	21st to end	Day	6% 1 3 12% 38% 40%	4311
September	1st to 10th	Day	4 1 3 10% 29% 53%	2400
	11th to 20th	Day	11% 3 6% 23% 38% 19%	2400
	21st to end	Day	10% 3 5% 19% 30% 33%	2116
October	1st to 10th	Day	11% 2 4 12% 26% 44%	3280
	11th to 20th	Day	14% 3 5% 27% 30% 21%	3261
	21st to end	Day	19% 4 7% 23% 32% 14%	3558
November	1st to 10th	Day	23% 6% 10% 26% 23% 12%	1975
	11th to 20th	Day	31% 6% 13% 22% 21% 7%	1864
	21st to end	Day	26% 4 12% 22% 23% 13%	1680
December	1st to 10th	Day	24% 5% 6% 26% 29% 10%	2636
	11th to 20th	Day	50% 5% 10% 17% 15% 3	3028
	21st to end	Day	47% 7% 14% 18% 11% 3	4004
January	1st to 10th	Night	29% 9% 21% 21% 16% 3	6203
	11th to 20th	Night	33% 7% 8% 16% 24% 12%	5880
	21st to end	Night	37% 5% 9% 10% 16% 23%	6468
February	1st to 10th	Night	35% 4 9% 19% 20% 12%	2600
	11th to 20th	Night	30% 6% 12% 22% 22% 9%	2475
	21st to end	Night	27% 5% 12% 22% 24% 9%	1980
March	1st to 10th	Night	32% 9% 13% 18% 21% 6%	5036
	11th to 20th	Night	29% 4 14% 23% 21% 9%	5000
	21st to end	Night	33% 7% 17% 24% 16% 3	5404
April	1st to 10th	Night	28% 7% 13% 22% 22% 8%	2000
	11th to 20th	Night	21% 5% 14% 27% 19% 13%	1979
	21st to end	Night	15% 5% 13% 30% 29% 8%	2000
May	1st to 10th	Night	10% 3 6% 23% 33% 25%	4235
	11th to 20th	Night	9% 3 6% 26% 35% 21%	3786
	21st to end	Night	5% 2 6% 30% 35% 22%	3972
June	1st to 10th	Night	14% 5% 10% 25% 33% 13%	1600
	11th to 20th	Night	6% 3 6% 20% 33% 32%	1600
	21st to end	Night	7% 2 3 12% 31% 45%	1600
July	1st to 10th	Night	3 1 1 5% 20% 71%	3600
	11th to 20th	Night	4 1 1 4 9% 80%	3814
	21st to end	Night	4 2 2 17% 23% 52%	4345
August	1st to 10th	Night	11% 2 2 7% 23% 55%	2929
	11th to 20th	Night	3 1 2 5% 33% 56%	3079
	21st to end	Night	7% 1 2 8% 35% 47%	3608
September	1st to 10th	Night	4 1 3 7% 30% 55%	2000
	11th to 20th	Night	11% 2 6% 19% 37% 26%	2000
	21st to end	Night	7% 2 5% 18% 30% 38%	2278
October	1st to 10th	Night	11% 3 5% 11% 19% 52%	3920
	11th to 20th	Night	11% 3 6% 28% 31% 21%	3897
	21st to end	Night	17% 3 6% 23% 29% 22%	4253
November	1st to 10th	Night	23% 6% 11% 24% 22% 14%	2541
	11th to 20th	Night	27% 5% 13% 24% 22% 9%	2751
	21st to end	Night	26% 5% 9% 22% 25% 13%	2940
December	1st to 10th	Night	24% 5% 6% 20% 30% 15%	4588
	11th to 20th	Night	45% 7% 11% 17% 17% 3	5176
	21st to end	Night	51% 7% 11% 16% 11% 3	6952

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% 12% 25% 20% 14%	240
	11th to 20th	Day	16% 11% 27% 28% 15% 4	400
	21st to end	Day	15% 10% 27% 23% 20% 5%	440
February	1st to 10th	Day	19% 13% 22% 26% 17% 5%	400
	11th to 20th	Day	15% 19% 29% 23% 12% 3	424
	21st to end	Day	11% 15% 26% 33% 12% 3	414
March	1st to 10th	Day	14% 19% 29% 25% 10% 4	500
	11th to 20th	Day	16% 15% 22% 25% 16% 5%	500
	21st to end	Day	14% 17% 26% 29% 12% 3	550
April	1st to 10th	Day	11% 14% 24% 29% 15% 6%	500
	11th to 20th	Day	9% 14% 28% 24% 17% 9%	492
	21st to end	Day	3 11% 25% 29% 23% 9%	500
May	1st to 10th	Day	6% 10% 27% 27% 23% 7%	503
	11th to 20th	Day	6% 7% 22% 27% 20% 16%	528
	21st to end	Day	3 6% 19% 28% 28% 16%	573
June	1st to 10th	Day	4 5% 19% 27% 32% 14%	530
	11th to 20th	Day	2 7% 19% 34% 31% 7%	530
	21st to end	Day	1 5% 13% 29% 38% 15%	530
July	1st to 10th	Day	1 1 10% 30% 44% 14%	526
	11th to 20th	Day	1 8% 25% 44% 22%	524
	21st to end	Day	1 1 6% 26% 44% 22%	575
August	1st to 10th	Day	3 1 8% 29% 38% 21%	527
	11th to 20th	Day	2 1 10% 26% 37% 23%	517
	21st to end	Day	1 2 6% 25% 43% 23%	583
September	1st to 10th	Day	1 1 12% 31% 39% 17%	530
	11th to 20th	Day	4 4 12% 27% 37% 16%	530
	21st to end	Day	2 6% 20% 30% 29% 12%	530
October	1st to 10th	Day	3 10% 18% 28% 27% 14%	530
	11th to 20th	Day	6% 6% 20% 25% 31% 12%	530
	21st to end	Day	11% 8% 20% 28% 25% 8%	583
November	1st to 10th	Day	10% 9% 22% 23% 29% 7%	451
	11th to 20th	Day	11% 10% 21% 26% 24% 8%	316
	21st to end	Day	13% 8% 25% 34% 16% 5%	220
December	1st to 10th	Day	19% 11% 23% 25% 16% 7%	204
	11th to 20th	Day	19% 8% 29% 23% 15% 7%	200
	21st to end	Day	17% 18% 25% 19% 18% 3	220
January	1st to 10th	Night	17% 6% 22% 31% 18% 5%	800
	11th to 20th	Night	14% 8% 24% 35% 15% 4	800
	21st to end	Night	15% 7% 22% 32% 19% 4	880
February	1st to 10th	Night	16% 10% 20% 33% 19% 2	800
	11th to 20th	Night	12% 10% 24% 31% 19% 5%	784
	21st to end	Night	11% 11% 25% 36% 15% 2	660
March	1st to 10th	Night	14% 10% 23% 32% 19% 3	800
	11th to 20th	Night	14% 8% 23% 30% 23% 2	800
	21st to end	Night	13% 8% 28% 34% 16% 1	880
April	1st to 10th	Night	7% 7% 26% 38% 20% 2	800
	11th to 20th	Night	7% 9% 25% 35% 20% 4	791
	21st to end	Night	4 7% 26% 36% 23% 4	800
May	1st to 10th	Night	5% 7% 27% 32% 26% 4	660
	11th to 20th	Night	3 4 16% 36% 37% 4	473
	21st to end	Night	4 5% 19% 34% 34% 3	433
June	1st to 10th	Night	4 4 19% 39% 34% 2	400
	11th to 20th	Night	1 5% 18% 40% 36% 1	400
	21st to end	Night	2 1 13% 43% 40% 2	400
July	1st to 10th	Night	1 1 8% 37% 51% 3	390
	11th to 20th	Night	1 4 37% 53% 6%	480
	21st to end	Night	1 4 30% 56% 9%	657
August	1st to 10th	Night	3 4 30% 56% 8%	597
	11th to 20th	Night	1 6% 35% 49% 9%	679
	21st to end	Night	1 1 4 32% 55% 7%	880
September	1st to 10th	Night	1 1 7% 37% 48% 6%	800
	11th to 20th	Night	2 2 10% 34% 44% 8%	800
	21st to end	Night	1 3 13% 39% 35% 10%	800
October	1st to 10th	Night	4 6% 16% 35% 33% 7%	800
	11th to 20th	Night	5% 5% 17% 32% 36% 5%	800
	21st to end	Night	8% 4 21% 30% 28% 9%	880
November	1st to 10th	Night	7% 6% 20% 30% 31% 6%	820
	11th to 20th	Night	10% 5% 21% 33% 27% 3	840
	21st to end	Night	9% 7% 22% 38% 19% 5%	840
December	1st to 10th	Night	14% 8% 23% 30% 22% 4	808
	11th to 20th	Night	20% 6% 20% 33% 19% 3	800
	21st to end	Night	15% 12% 26% 29% 18% 1	880

Page generated at 2025-11-29 22:00:51. Version ac07

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