Log Hill Mesa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Log Hill Mesa clear sky chart from 2005-11-06 to 2026-07-01.

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 6% 2 6% 4 4 5% 4 6% 7% 52%	146602
	Night	2 6% 3 6% 3 4 4 4 5% 7% 56%	143332
Transparency	Day	30% 7% 10% 21% 23% 10%	141501
	Night	25% 7% 11% 24% 24% 9%	139441
Seeing	Day	9% 17% 31% 27% 13% 3	17524
	Night	6% 10% 29% 34% 18% 3	27676

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 9% 4 15% 5% 4 3 3 6% 7% 43%	5177
	11th to 20th	Day	1 6% 3 9% 5% 4 3 3 4 6% 56%	5340
	21st to end	Day	1 7% 4 9% 4 3 4 3 5% 6% 55%	5844
February	1st to 10th	Day	2 12% 5% 8% 5% 4 5% 3 6% 7% 44%	1890
	11th to 20th	Day	2 11% 4 8% 5% 5% 5% 4 5% 7% 43%	1883
	21st to end	Day	1 11% 5% 10% 5% 4 4 3 4 6% 47%	1730
March	1st to 10th	Day	1 9% 4 9% 4 4 4 3 5% 6% 50%	5064
	11th to 20th	Day	1 12% 4 9% 6% 5% 6% 5% 6% 8% 39%	5110
	21st to end	Day	1 7% 4 8% 5% 5% 6% 6% 7% 10% 41%	5621
April	1st to 10th	Day	2 9% 3 7% 4 3 5% 4 6% 6% 50%	2520
	11th to 20th	Day	2 10% 4 7% 4 5% 4 4 6% 8% 44%	2491
	21st to end	Day	3 10% 3 6% 4 5% 5% 3 6% 9% 46%	2520
May	1st to 10th	Day	3 6% 2 6% 5% 5% 5% 4 6% 7% 50%	7505
	11th to 20th	Day	2 5% 2 6% 4 5% 5% 5% 7% 9% 51%	7655
	21st to end	Day	2 3 1 4 4 4 5% 4 7% 8% 57%	9026
June	1st to 10th	Day	3 3 1 4 4 4 4 4 7% 8% 58%	2940
	11th to 20th	Day	3 2 1 4 3 3 4 4 5% 7% 65%	2940
	21st to end	Day	2 3 1 4 4 4 4 4 5% 8% 61%	2940
July	1st to 10th	Day	2 2 1 3 3 4 4 4 5% 4 67%	6296
	11th to 20th	Day	2 3 1 4 4 6% 8% 7% 11% 12% 45%	5880
	21st to end	Day	3 4 2 5% 5% 5% 7% 6% 8% 8% 48%	6401
August	1st to 10th	Day	3 3 2 5% 5% 5% 7% 6% 8% 11% 45%	5779
	11th to 20th	Day	3 3 1 5% 5% 5% 6% 5% 7% 8% 52%	5632
	21st to end	Day	3 3 2 7% 5% 6% 7% 6% 9% 11% 41%	5984
September	1st to 10th	Day	6% 4 2 7% 4 5% 5% 4 4 8% 51%	2400
	11th to 20th	Day	5% 3 2 5% 4 5% 4 4 6% 7% 54%	2384
	21st to end	Day	5% 4 2 5% 3 4 4 3 4 6% 62%	2111
October	1st to 10th	Day	3 3 1 3 2 2 2 2 3 5% 73%	3270
	11th to 20th	Day	4 4 2 5% 4 4 5% 4 6% 8% 53%	3250
	21st to end	Day	3 5% 1 3 2 2 2 2 4 5% 69%	3548
November	1st to 10th	Day	1 5% 1 4 3 2 2 2 5% 6% 67%	2035
	11th to 20th	Day	2 7% 2 5% 2 3 3 3 5% 5% 63%	1858
	21st to end	Day	2 6% 3 7% 3 4 4 3 3 5% 60%	1680
December	1st to 10th	Day	1 8% 3 6% 3 2 2 2 4 4 64%	2700
	11th to 20th	Day	1 6% 3 7% 3 3 3 3 4 7% 58%	3106
	21st to end	Day	2 9% 3 9% 4 4 4 3 5% 6% 50%	4092
January	1st to 10th	Night	1 10% 6% 14% 5% 5% 5% 4 6% 7% 39%	7799
	11th to 20th	Night	1 8% 3 7% 4 4 4 3 3 5% 58%	7650
	21st to end	Night	1 9% 4 8% 3 3 4 3 4 5% 56%	8370
February	1st to 10th	Night	1 10% 5% 8% 4 4 4 3 4 6% 51%	2730
	11th to 20th	Night	2 8% 4 9% 5% 5% 5% 4 5% 6% 47%	2621
	21st to end	Night	2 10% 3 8% 6% 4 4 3 5% 6% 49%	2072
March	1st to 10th	Night	1 9% 3 8% 5% 4 5% 4 5% 7% 50%	5050
	11th to 20th	Night	1 9% 5% 8% 4 4 5% 3 5% 7% 49%	5110
	21st to end	Night	1 9% 5% 7% 4 5% 5% 5% 7% 8% 44%	5593
April	1st to 10th	Night	3 8% 3 6% 4 4 5% 4 7% 7% 50%	2100
	11th to 20th	Night	2 12% 3 5% 3 4 4 4 6% 8% 48%	2077
	21st to end	Night	4 9% 3 5% 4 3 5% 3 6% 7% 52%	2100
May	1st to 10th	Night	3 6% 2 5% 4 3 4 4 7% 9% 52%	5438
	11th to 20th	Night	3 4 1 4 3 3 4 4 6% 9% 59%	5219
	21st to end	Night	2 2 1 3 2 2 3 3 5% 7% 70%	5181
June	1st to 10th	Night	2 2 1 2 2 2 2 3 6% 8% 68%	1680
	11th to 20th	Night	2 2 1 2 2 2 4 3 4 6% 73%	1680
	21st to end	Night	1 1 1 3 2 3 4 4 5% 8% 67%	1680
July	1st to 10th	Night	1 1 1 3 2 3 4 4 6% 7% 68%	3678
	11th to 20th	Night	1 1 1 3 3 4 5% 5% 9% 14% 54%	4100
	21st to end	Night	1 2 1 4 4 4 5% 5% 7% 10% 57%	4472
August	1st to 10th	Night	2 2 1 3 4 4 6% 5% 8% 11% 54%	4033
	11th to 20th	Night	2 1 1 3 3 3 5% 4 7% 10% 61%	4217
	21st to end	Night	3 3 2 6% 5% 5% 6% 5% 9% 10% 46%	4993
September	1st to 10th	Night	3 3 1 4 3 3 4 4 5% 10% 59%	2000
	11th to 20th	Night	3 2 1 3 2 4 5% 4 6% 7% 63%	2012
	21st to end	Night	3 3 1 3 2 2 2 3 4 5% 71%	2288
October	1st to 10th	Night	2 2 1 2 2 2 2 1 2 5% 78%	3920
	11th to 20th	Night	3 3 1 4 3 3 4 4 5% 7% 63%	3898
	21st to end	Night	3 6% 2 4 2 2 2 2 3 4 70%	4252
November	1st to 10th	Night	2 5% 1 3 2 2 3 3 5% 6% 66%	2460
	11th to 20th	Night	2 8% 2 3 3 3 3 2 5% 5% 64%	2760
	21st to end	Night	2 8% 3 6% 3 3 3 3 4 6% 58%	2940
December	1st to 10th	Night	1 6% 2 6% 3 2 3 2 4 5% 66%	4710
	11th to 20th	Night	1 6% 2 5% 3 3 4 4 5% 7% 59%	5321
	21st to end	Night	2 10% 4 9% 5% 4 4 3 5% 6% 47%	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	39% 7% 13% 25% 15% 1	5180
	11th to 20th	Day	31% 4 12% 23% 23% 7%	5340
	21st to end	Day	31% 4 9% 26% 25% 6%	5844
February	1st to 10th	Day	40% 7% 13% 16% 17% 7%	1890
	11th to 20th	Day	40% 7% 8% 20% 19% 5%	1892
	21st to end	Day	41% 5% 6% 20% 22% 7%	1730
March	1st to 10th	Day	32% 7% 9% 19% 24% 9%	5064
	11th to 20th	Day	39% 8% 11% 22% 16% 3	5110
	21st to end	Day	39% 7% 12% 28% 13% 2	5621
April	1st to 10th	Day	34% 7% 10% 23% 20% 6%	2520
	11th to 20th	Day	38% 7% 9% 20% 21% 5%	2494
	21st to end	Day	36% 8% 11% 23% 19% 3	2520
May	1st to 10th	Day	31% 6% 11% 26% 21% 4	7505
	11th to 20th	Day	26% 8% 10% 19% 30% 7%	7658
	21st to end	Day	22% 6% 9% 22% 32% 9%	9027
June	1st to 10th	Day	24% 7% 11% 22% 25% 11%	2940
	11th to 20th	Day	20% 5% 8% 15% 28% 24%	2940
	21st to end	Day	23% 6% 9% 15% 23% 24%	2940
July	1st to 10th	Day	21% 5% 7% 8% 14% 46%	6228
	11th to 20th	Day	26% 10% 15% 20% 18% 11%	5811
	21st to end	Day	31% 10% 13% 13% 18% 15%	6217
August	1st to 10th	Day	40% 11% 17% 14% 11% 7%	4208
	11th to 20th	Day	36% 9% 13% 11% 21% 10%	4079
	21st to end	Day	32% 9% 13% 17% 22% 8%	4311
September	1st to 10th	Day	34% 7% 9% 14% 22% 13%	2400
	11th to 20th	Day	30% 9% 10% 15% 26% 10%	2384
	21st to end	Day	27% 5% 8% 20% 30% 10%	2111
October	1st to 10th	Day	18% 4 6% 16% 38% 18%	3270
	11th to 20th	Day	25% 7% 8% 27% 26% 6%	3250
	21st to end	Day	18% 4 6% 27% 37% 8%	3548
November	1st to 10th	Day	21% 5% 10% 26% 32% 7%	2035
	11th to 20th	Day	23% 5% 10% 32% 24% 7%	1858
	21st to end	Day	28% 6% 9% 26% 21% 10%	1680
December	1st to 10th	Day	25% 5% 8% 35% 21% 6%	2700
	11th to 20th	Day	26% 5% 9% 29% 28% 3	3104
	21st to end	Day	32% 5% 12% 23% 20% 8%	4092
January	1st to 10th	Night	39% 7% 12% 26% 13% 2	7800
	11th to 20th	Night	30% 5% 11% 25% 22% 7%	7650
	21st to end	Night	29% 5% 8% 24% 28% 6%	8370
February	1st to 10th	Night	35% 6% 12% 21% 19% 7%	2730
	11th to 20th	Night	35% 7% 11% 23% 18% 6%	2622
	21st to end	Night	36% 5% 10% 20% 23% 6%	2072
March	1st to 10th	Night	29% 8% 8% 19% 28% 9%	5050
	11th to 20th	Night	31% 9% 10% 23% 22% 5%	5110
	21st to end	Night	36% 8% 15% 28% 12% 1	5593
April	1st to 10th	Night	33% 8% 11% 23% 20% 5%	2100
	11th to 20th	Night	34% 7% 11% 21% 23% 5%	2077
	21st to end	Night	31% 7% 11% 26% 22% 3	2100
May	1st to 10th	Night	25% 7% 12% 30% 23% 3	5436
	11th to 20th	Night	18% 7% 10% 27% 34% 5%	5220
	21st to end	Night	14% 5% 10% 24% 37% 11%	5182
June	1st to 10th	Night	13% 7% 10% 25% 33% 13%	1680
	11th to 20th	Night	14% 5% 7% 16% 29% 28%	1680
	21st to end	Night	14% 6% 10% 17% 27% 27%	1680
July	1st to 10th	Night	16% 6% 9% 11% 12% 47%	3638
	11th to 20th	Night	17% 7% 15% 30% 18% 13%	4046
	21st to end	Night	20% 9% 17% 18% 22% 15%	4344
August	1st to 10th	Night	27% 11% 23% 16% 12% 11%	2928
	11th to 20th	Night	20% 9% 24% 14% 19% 14%	3046
	21st to end	Night	24% 9% 15% 21% 23% 8%	3597
September	1st to 10th	Night	22% 8% 13% 18% 26% 14%	2000
	11th to 20th	Night	19% 7% 13% 19% 29% 13%	2012
	21st to end	Night	16% 4 9% 24% 35% 10%	2288
October	1st to 10th	Night	13% 3 7% 14% 42% 22%	3920
	11th to 20th	Night	17% 6% 7% 31% 31% 7%	3898
	21st to end	Night	18% 5% 5% 25% 36% 11%	4252
November	1st to 10th	Night	19% 7% 12% 26% 29% 8%	2460
	11th to 20th	Night	22% 5% 9% 28% 28% 7%	2760
	21st to end	Night	28% 6% 8% 24% 24% 11%	2940
December	1st to 10th	Night	21% 5% 9% 36% 25% 4	4710
	11th to 20th	Night	22% 7% 9% 32% 27% 5%	5322
	21st to end	Night	34% 9% 9% 20% 21% 6%	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	11% 18% 31% 28% 11% 2	330
	11th to 20th	Day	10% 20% 32% 25% 11% 2	330
	21st to end	Day	4 16% 39% 30% 9% 2	363
February	1st to 10th	Day	13% 26% 33% 22% 4 1	330
	11th to 20th	Day	16% 31% 33% 16% 4	330
	21st to end	Day	17% 26% 30% 22% 4	273
March	1st to 10th	Day	15% 31% 30% 19% 4 1	540
	11th to 20th	Day	10% 30% 32% 21% 6%	540
	21st to end	Day	16% 31% 31% 17% 5%	594
April	1st to 10th	Day	14% 25% 33% 20% 6% 1	540
	11th to 20th	Day	16% 32% 32% 15% 4	532
	21st to end	Day	12% 30% 35% 16% 6%	540
May	1st to 10th	Day	14% 26% 35% 18% 7% 1	543
	11th to 20th	Day	10% 21% 34% 24% 9% 2	588
	21st to end	Day	9% 19% 31% 24% 14% 3	844
June	1st to 10th	Day	5% 11% 31% 33% 16% 4	780
	11th to 20th	Day	5% 13% 34% 31% 13% 4	780
	21st to end	Day	3 12% 34% 30% 17% 3	780
July	1st to 10th	Day	3 5% 23% 41% 24% 5%	704
	11th to 20th	Day	4 4 23% 39% 23% 8%	524
	21st to end	Day	6% 3 23% 38% 24% 6%	575
August	1st to 10th	Day	7% 6% 27% 36% 19% 6%	527
	11th to 20th	Day	5% 4 29% 37% 20% 5%	517
	21st to end	Day	3 5% 31% 37% 19% 5%	583
September	1st to 10th	Day	8% 8% 26% 34% 20% 5%	530
	11th to 20th	Day	5% 12% 41% 29% 10% 2	530
	21st to end	Day	7% 15% 29% 30% 14% 4	441
October	1st to 10th	Day	9% 18% 25% 24% 17% 6%	330
	11th to 20th	Day	5% 20% 32% 26% 15% 2	330
	21st to end	Day	7% 17% 35% 27% 12% 2	363
November	1st to 10th	Day	10% 25% 25% 27% 12% 2	330
	11th to 20th	Day	5% 19% 31% 27% 15% 2	330
	21st to end	Day	8% 19% 28% 30% 13% 2	330
December	1st to 10th	Day	9% 22% 31% 25% 13% 1	330
	11th to 20th	Day	9% 18% 31% 28% 12% 3	330
	21st to end	Day	15% 19% 33% 22% 9% 1	363
January	1st to 10th	Night	7% 11% 31% 32% 15% 4	908
	11th to 20th	Night	7% 12% 30% 33% 15% 3	840
	21st to end	Night	5% 9% 34% 35% 13% 3	924
February	1st to 10th	Night	8% 13% 39% 29% 9% 2	840
	11th to 20th	Night	6% 14% 42% 27% 9% 1	824
	21st to end	Night	8% 15% 42% 28% 7%	692
March	1st to 10th	Night	7% 18% 34% 30% 9% 2	840
	11th to 20th	Night	5% 11% 36% 32% 16% 1	840
	21st to end	Night	6% 18% 36% 29% 9% 1	919
April	1st to 10th	Night	10% 16% 38% 30% 6%	630
	11th to 20th	Night	9% 19% 36% 27% 9% 1	623
	21st to end	Night	8% 16% 33% 29% 12% 2	630
May	1st to 10th	Night	6% 12% 34% 36% 12% 1	630
	11th to 20th	Night	8% 8% 30% 36% 16% 3	621
	21st to end	Night	6% 11% 29% 34% 17% 2	683
June	1st to 10th	Night	3 7% 26% 39% 24% 2	630
	11th to 20th	Night	3 9% 28% 42% 16% 2	630
	21st to end	Night	2 3 24% 43% 25% 3	630
July	1st to 10th	Night	3 1 18% 40% 35% 3	585
	11th to 20th	Night	2 3 9% 41% 40% 5%	582
	21st to end	Night	3 2 10% 37% 43% 4	657
August	1st to 10th	Night	4 2 13% 40% 37% 5%	597
	11th to 20th	Night	3 2 11% 42% 37% 5%	594
	21st to end	Night	3 2 15% 42% 31% 6%	660
September	1st to 10th	Night	3 3 15% 45% 31% 3	600
	11th to 20th	Night	2 3 24% 39% 27% 4	612
	21st to end	Night	4 7% 19% 38% 24% 8%	800
October	1st to 10th	Night	5% 11% 26% 38% 19% 2	800
	11th to 20th	Night	4 8% 30% 33% 20% 5%	800
	21st to end	Night	9% 9% 27% 33% 18% 5%	880
November	1st to 10th	Night	6% 11% 27% 35% 18% 3	820
	11th to 20th	Night	7% 11% 32% 32% 15% 3	1050
	21st to end	Night	8% 12% 30% 32% 14% 3	1050
December	1st to 10th	Night	7% 13% 31% 34% 13% 2	1050
	11th to 20th	Night	7% 16% 31% 29% 16% 1	1050
	21st to end	Night	10% 13% 37% 32% 8% 1	1155

Page generated at 2026-06-28 00:10:48. Version ac07

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