Mount Pinos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Pinos clear sky chart from 2005-11-06 to 2025-11-03.

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	2 3 1 3 3 2 3 3 4 6% 71%	134843
	Night	2 4 1 4 3 3 3 3 4 6% 68%	132717
Transparency	Day	14% 3 5% 15% 29% 33%	129923
	Night	15% 3 5% 16% 29% 32%	128610
Seeing	Day	9% 12% 28% 32% 15% 5%	16883
	Night	6% 7% 19% 34% 28% 7%	26565

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	2 4 2 5% 3 3 3 3 5% 7% 62%	3655
	11th to 20th	Day	3 4 2 5% 3 3 3 3 4 7% 64%	4100
	21st to end	Day	3 8% 3 8% 5% 3 4 4 6% 8% 51%	4621
February	1st to 10th	Day	4 8% 2 5% 4 3 4 4 5% 6% 54%	2000
	11th to 20th	Day	4 7% 3 6% 4 4 3 3 6% 8% 52%	1950
	21st to end	Day	4 7% 3 7% 5% 4 4 3 5% 6% 54%	1650
March	1st to 10th	Day	4 8% 3 7% 5% 5% 5% 4 5% 6% 48%	4518
	11th to 20th	Day	2 6% 3 6% 5% 4 4 3 4 8% 56%	4838
	21st to end	Day	2 7% 2 4 4 4 5% 5% 8% 9% 50%	5915
April	1st to 10th	Day	4 8% 2 4 4 3 4 3 5% 7% 55%	2400
	11th to 20th	Day	3 4 2 5% 3 3 3 3 5% 7% 63%	2369
	21st to end	Day	3 4 1 3 3 2 3 3 5% 7% 65%	2400
May	1st to 10th	Day	2 2 1 4 2 2 2 3 4 4 73%	5457
	11th to 20th	Day	1 1 1 2 2 1 2 3 4 7% 77%	5841
	21st to end	Day	1 2 1 2 2 1 2 2 2 5% 81%	6466
June	1st to 10th	Day	1 2 1 2 2 2 3 3 5% 7% 72%	2800
	11th to 20th	Day	1 1 1 1 1 2 3 4 85%	2800
	21st to end	Day	1 1 1 1 1 1 3 5% 85%	2800
July	1st to 10th	Day	1 1 1 1 1 2 2 91%	6319
	11th to 20th	Day	1 1 1 2 1 2 2 2 3 5% 82%	6234
	21st to end	Day	1 1 1 1 1 1 1 4 4 85%	6229
August	1st to 10th	Day	1 1 2 1 2 2 2 4 5% 80%	5346
	11th to 20th	Day	1 1 1 1 2 93%	5364
	21st to end	Day	1 1 1 2 1 2 2 2 3 5% 81%	5984
September	1st to 10th	Day	1 1 1 2 2 2 2 2 3 5% 81%	2400
	11th to 20th	Day	1 1 1 2 1 2 1 2 4 84%	2310
	21st to end	Day	1 1 1 2 2 2 2 2 3 4 81%	2200
October	1st to 10th	Day	1 2 1 2 2 2 3 2 3 4 78%	3536
	11th to 20th	Day	1 1 2 2 3 3 2 3 4 80%	3261
	21st to end	Day	1 1 2 5% 3 3 4 3 4 5% 70%	3558
November	1st to 10th	Day	1 4 1 4 3 3 3 3 5% 6% 67%	1797
	11th to 20th	Day	2 4 1 4 3 3 4 4 6% 6% 66%	1800
	21st to end	Day	3 6% 3 6% 4 5% 4 3 5% 6% 55%	1800
December	1st to 10th	Day	2 4 2 6% 4 4 4 4 6% 6% 59%	2950
	11th to 20th	Day	3 5% 2 6% 5% 4 5% 5% 7% 7% 52%	3171
	21st to end	Day	4 7% 4 7% 4 5% 5% 5% 6% 8% 45%	4004
January	1st to 10th	Night	2 5% 3 7% 4 3 4 4 5% 7% 57%	6288
	11th to 20th	Night	2 4 2 5% 4 3 3 3 5% 5% 64%	5880
	21st to end	Night	3 9% 3 6% 4 4 4 4 6% 7% 50%	6358
February	1st to 10th	Night	3 8% 3 7% 5% 4 3 3 5% 7% 52%	2400
	11th to 20th	Night	4 7% 2 5% 4 3 4 3 5% 7% 54%	2338
	21st to end	Night	3 7% 2 7% 4 4 4 4 5% 6% 54%	1980
March	1st to 10th	Night	2 7% 2 11% 5% 4 5% 5% 7% 8% 44%	5376
	11th to 20th	Night	2 5% 2 8% 6% 4 4 4 4 7% 53%	5146
	21st to end	Night	2 7% 3 8% 5% 5% 5% 5% 6% 8% 46%	5059
April	1st to 10th	Night	2 7% 3 6% 5% 3 4 3 6% 7% 54%	2000
	11th to 20th	Night	2 6% 2 4 4 3 3 3 4 7% 63%	1979
	21st to end	Night	2 5% 2 4 3 2 3 3 4 8% 64%	2000
May	1st to 10th	Night	2 3 1 4 3 2 2 2 3 4 75%	4542
	11th to 20th	Night	1 1 1 2 1 1 2 2 4 5% 80%	4074
	21st to end	Night	1 1 2 1 1 1 1 1 3 87%	4410
June	1st to 10th	Night	1 2 1 2 2 2 3 3 5% 5% 75%	1600
	11th to 20th	Night	1 1 1 1 1 1 3 4 88%	1600
	21st to end	Night	1 1 1 1 1 2 3 89%	1600
July	1st to 10th	Night	1 1 1 1 1 2 2 93%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 2 2 90%	3725
	21st to end	Night	1 1 1 1 1 1 2 3 89%	4648
August	1st to 10th	Night	1 1 1 1 1 2 1 3 5% 85%	4486
	11th to 20th	Night	1 1 1 1 2 94%	4506
	21st to end	Night	1 1 1 1 1 1 2 3 89%	5015
September	1st to 10th	Night	1 1 1 2 1 1 1 1 2 3 87%	2000
	11th to 20th	Night	1 1 1 1 2 2 1 3 3 85%	2088
	21st to end	Night	1 1 2 1 2 2 2 3 4 81%	2200
October	1st to 10th	Night	1 1 1 1 2 2 2 2 3 84%	3659
	11th to 20th	Night	1 1 1 2 1 2 2 3 4 5% 78%	3897
	21st to end	Night	1 2 3 5% 2 2 2 2 3 5% 73%	4253
November	1st to 10th	Night	1 5% 1 4 3 3 3 4 6% 7% 63%	2545
	11th to 20th	Night	2 4 1 5% 2 3 4 3 5% 7% 63%	2600
	21st to end	Night	2 5% 2 5% 5% 4 4 4 6% 7% 55%	2600
December	1st to 10th	Night	2 4 1 5% 3 3 4 4 5% 8% 61%	4240
	11th to 20th	Night	3 5% 2 5% 5% 5% 6% 6% 8% 9% 47%	5033
	21st to end	Night	4 6% 2 8% 6% 6% 6% 6% 8% 10% 39%	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	16% 4 5% 24% 36% 16%	3655
	11th to 20th	Day	17% 5% 11% 12% 22% 34%	4100
	21st to end	Day	27% 4 7% 16% 23% 23%	4621
February	1st to 10th	Day	28% 3 5% 18% 26% 21%	2000
	11th to 20th	Day	25% 4 6% 21% 28% 16%	1960
	21st to end	Day	28% 5% 6% 20% 27% 14%	1650
March	1st to 10th	Day	29% 5% 6% 17% 24% 20%	4518
	11th to 20th	Day	25% 4 9% 28% 22% 13%	4838
	21st to end	Day	21% 7% 11% 27% 29% 5%	5915
April	1st to 10th	Day	23% 5% 9% 24% 28% 12%	2400
	11th to 20th	Day	19% 4 8% 24% 30% 15%	2372
	21st to end	Day	15% 5% 8% 27% 36% 10%	2400
May	1st to 10th	Day	12% 3 7% 20% 39% 18%	5457
	11th to 20th	Day	8% 2 4 18% 43% 24%	5844
	21st to end	Day	9% 2 3 17% 42% 27%	6467
June	1st to 10th	Day	12% 3 6% 20% 34% 25%	2800
	11th to 20th	Day	5% 2 4 13% 32% 43%	2800
	21st to end	Day	6% 2 2 6% 28% 56%	2800
July	1st to 10th	Day	3 1 1 3 14% 78%	6251
	11th to 20th	Day	8% 2 2 8% 22% 57%	6159
	21st to end	Day	5% 2 4 14% 27% 49%	6049
August	1st to 10th	Day	8% 2 3 9% 30% 49%	3890
	11th to 20th	Day	3 1 1 5% 24% 65%	3880
	21st to end	Day	6% 1 1 4 26% 61%	4311
September	1st to 10th	Day	7% 3 3 8% 30% 49%	2400
	11th to 20th	Day	6% 3 2 9% 35% 44%	2310
	21st to end	Day	9% 2 3 11% 38% 38%	2200
October	1st to 10th	Day	9% 3 3 9% 24% 52%	3536
	11th to 20th	Day	9% 1 3 9% 41% 37%	3261
	21st to end	Day	14% 3 3 10% 35% 35%	3558
November	1st to 10th	Day	15% 3 4 20% 33% 26%	1797
	11th to 20th	Day	16% 3 7% 17% 29% 28%	1800
	21st to end	Day	26% 4 7% 14% 24% 26%	1800
December	1st to 10th	Day	22% 4 4 13% 28% 29%	2950
	11th to 20th	Day	27% 4 7% 24% 26% 12%	3170
	21st to end	Day	30% 4 9% 20% 23% 14%	4004
January	1st to 10th	Night	18% 3 5% 22% 34% 18%	6288
	11th to 20th	Night	17% 5% 7% 14% 25% 32%	5880
	21st to end	Night	27% 4 6% 15% 21% 28%	6358
February	1st to 10th	Night	28% 5% 7% 15% 24% 22%	2400
	11th to 20th	Night	24% 4 7% 20% 28% 18%	2339
	21st to end	Night	26% 5% 7% 19% 27% 17%	1980
March	1st to 10th	Night	23% 6% 8% 17% 29% 17%	5376
	11th to 20th	Night	23% 3 9% 31% 22% 12%	5146
	21st to end	Night	21% 4 13% 29% 28% 6%	5059
April	1st to 10th	Night	23% 3 12% 24% 25% 13%	2000
	11th to 20th	Night	17% 3 9% 22% 31% 17%	1979
	21st to end	Night	13% 4 10% 28% 35% 11%	2000
May	1st to 10th	Night	10% 2 8% 20% 38% 21%	4539
	11th to 20th	Night	6% 2 3 22% 45% 21%	4075
	21st to end	Night	6% 1 4 17% 41% 31%	4410
June	1st to 10th	Night	10% 2 8% 21% 36% 23%	1600
	11th to 20th	Night	5% 1 5% 14% 32% 44%	1600
	21st to end	Night	4 1 2 7% 28% 58%	1600
July	1st to 10th	Night	3 1 1 3 14% 79%	3600
	11th to 20th	Night	4 1 2 7% 19% 67%	3677
	21st to end	Night	4 1 2 13% 30% 50%	4517
August	1st to 10th	Night	6% 2 1 10% 35% 46%	3256
	11th to 20th	Night	3 1 1 6% 28% 62%	3256
	21st to end	Night	4 1 1 6% 29% 60%	3608
September	1st to 10th	Night	6% 2 2 9% 29% 52%	2000
	11th to 20th	Night	5% 2 3 10% 38% 42%	2088
	21st to end	Night	6% 2 2 14% 37% 39%	2200
October	1st to 10th	Night	7% 1 2 10% 21% 58%	3659
	11th to 20th	Night	8% 1 2 11% 32% 46%	3897
	21st to end	Night	11% 5% 3 8% 33% 41%	4253
November	1st to 10th	Night	16% 3 5% 17% 32% 27%	2545
	11th to 20th	Night	16% 4 7% 14% 29% 30%	2600
	21st to end	Night	23% 4 7% 15% 24% 26%	2600
December	1st to 10th	Night	19% 4 3 12% 31% 31%	4240
	11th to 20th	Night	29% 3 8% 20% 23% 16%	5033
	21st to end	Night	29% 5% 8% 21% 24% 13%	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	21% 18% 30% 23% 7% 1	203
	11th to 20th	Day	19% 19% 29% 25% 7% 1	400
	21st to end	Day	17% 23% 32% 18% 8% 2	464
February	1st to 10th	Day	15% 19% 35% 21% 7% 3	500
	11th to 20th	Day	21% 18% 31% 21% 7% 1	495
	21st to end	Day	17% 20% 35% 22% 6%	414
March	1st to 10th	Day	19% 23% 32% 20% 5% 1	500
	11th to 20th	Day	20% 20% 30% 23% 6% 1	500
	21st to end	Day	16% 23% 33% 21% 6%	550
April	1st to 10th	Day	15% 15% 32% 25% 11% 2	500
	11th to 20th	Day	13% 17% 33% 25% 10% 1	492
	21st to end	Day	9% 16% 29% 27% 14% 5%	500
May	1st to 10th	Day	11% 14% 33% 27% 13% 2	503
	11th to 20th	Day	9% 12% 31% 30% 14% 5%	528
	21st to end	Day	10% 10% 29% 32% 14% 5%	573
June	1st to 10th	Day	4 7% 28% 32% 22% 7%	530
	11th to 20th	Day	2 7% 28% 37% 19% 7%	530
	21st to end	Day	2 7% 27% 37% 18% 9%	530
July	1st to 10th	Day	2 3 18% 43% 24% 11%	526
	11th to 20th	Day	3 1 11% 42% 26% 17%	524
	21st to end	Day	2 2 14% 42% 27% 14%	575
August	1st to 10th	Day	2 1 23% 41% 21% 11%	527
	11th to 20th	Day	2 3 17% 42% 29% 8%	517
	21st to end	Day	2 3 17% 48% 22% 9%	583
September	1st to 10th	Day	2 5% 25% 42% 21% 6%	530
	11th to 20th	Day	1 8% 30% 43% 16% 2	530
	21st to end	Day	1 11% 28% 40% 16% 4	530
October	1st to 10th	Day	5% 10% 32% 35% 17% 2	530
	11th to 20th	Day	5% 10% 36% 33% 13% 3	530
	21st to end	Day	5% 12% 31% 35% 13% 3	583
November	1st to 10th	Day	8% 10% 29% 30% 19% 3	321
	11th to 20th	Day	9% 13% 29% 32% 13% 4	300
	21st to end	Day	12% 15% 31% 26% 12% 3	300
December	1st to 10th	Day	7% 14% 34% 31% 13% 2	300
	11th to 20th	Day	13% 16% 27% 26% 15% 4	245
	21st to end	Day	20% 24% 25% 20% 9% 3	220
January	1st to 10th	Night	13% 9% 25% 30% 17% 7%	800
	11th to 20th	Night	8% 9% 30% 33% 15% 5%	800
	21st to end	Night	12% 12% 29% 29% 14% 4	880
February	1st to 10th	Night	12% 11% 25% 30% 16% 5%	800
	11th to 20th	Night	11% 10% 26% 30% 15% 8%	784
	21st to end	Night	9% 13% 25% 33% 16% 3	660
March	1st to 10th	Night	10% 14% 25% 32% 17% 2	800
	11th to 20th	Night	10% 10% 23% 32% 21% 4	800
	21st to end	Night	9% 13% 22% 34% 19% 3	880
April	1st to 10th	Night	7% 10% 27% 34% 18% 4	800
	11th to 20th	Night	6% 9% 25% 35% 23% 3	791
	21st to end	Night	5% 8% 26% 33% 23% 6%	800
May	1st to 10th	Night	5% 6% 25% 34% 26% 4	795
	11th to 20th	Night	5% 8% 17% 36% 31% 3	591
	21st to end	Night	4 5% 23% 32% 30% 4	625
June	1st to 10th	Night	2 4 14% 42% 34% 5%	400
	11th to 20th	Night	2 13% 43% 35% 7%	400
	21st to end	Night	1 1 10% 42% 40% 7%	400
July	1st to 10th	Night	1 1 3 33% 54% 9%	390
	11th to 20th	Night	2 1 29% 55% 13%	421
	21st to end	Night	2 1 3 25% 54% 16%	732
August	1st to 10th	Night	2 4 34% 50% 9%	796
	11th to 20th	Night	3 31% 53% 12%	792
	21st to end	Night	2 3 30% 53% 12%	880
September	1st to 10th	Night	1 2 7% 31% 48% 12%	800
	11th to 20th	Night	1 1 9% 43% 36% 9%	800
	21st to end	Night	1 2 14% 38% 38% 8%	800
October	1st to 10th	Night	2 3 16% 44% 30% 5%	800
	11th to 20th	Night	3 5% 19% 36% 29% 8%	800
	21st to end	Night	3 6% 20% 33% 29% 9%	880
November	1st to 10th	Night	4 9% 17% 37% 24% 9%	788
	11th to 20th	Night	6% 5% 21% 38% 23% 8%	800
	21st to end	Night	7% 9% 27% 31% 22% 6%	800
December	1st to 10th	Night	7% 9% 26% 34% 20% 4	800
	11th to 20th	Night	12% 10% 21% 38% 15% 5%	800
	21st to end	Night	13% 12% 24% 32% 14% 5%	880

Page generated at 2025-10-30 23:02:39. Version ac07

Copyright © 2025 Attilla Danko.