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 2024-09-29.

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	3 7% 3 7% 5% 4 5% 4 6% 7% 49%	100829
	Night	2 7% 3 6% 4 4 4 4 6% 7% 54%	97637
Transparency	Day	34% 7% 11% 19% 20% 10%	100589
	Night	29% 7% 12% 22% 22% 9%	97466
Seeing	Day	9% 18% 31% 27% 12% 3	15179
	Night	6% 11% 27% 34% 19% 3	25275

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 16% 5% 4 4 3 6% 6% 42%	2771
	11th to 20th	Day	2 10% 5% 9% 6% 5% 4 4 6% 7% 42%	2860
	21st to end	Day	2 10% 5% 10% 4 4 4 3 4 5% 48%	3146
February	1st to 10th	Day	2 13% 5% 9% 6% 4 5% 3 5% 6% 41%	1710
	11th to 20th	Day	2 10% 4 9% 5% 4 5% 4 5% 7% 45%	1699
	21st to end	Day	1 12% 5% 11% 6% 4 4 3 5% 6% 43%	1570
March	1st to 10th	Day	2 9% 4 10% 4 4 4 4 6% 7% 47%	3444
	11th to 20th	Day	1 12% 4 9% 6% 5% 5% 5% 6% 7% 39%	3490
	21st to end	Day	1 9% 5% 10% 6% 6% 7% 6% 7% 9% 34%	3839
April	1st to 10th	Day	3 9% 3 7% 4 3 5% 4 6% 6% 49%	2280
	11th to 20th	Day	2 11% 4 7% 4 5% 5% 5% 6% 8% 43%	2251
	21st to end	Day	4 11% 3 6% 4 5% 4 3 6% 8% 46%	2280
May	1st to 10th	Day	3 7% 3 7% 5% 5% 6% 4 6% 7% 47%	4041
	11th to 20th	Day	2 6% 2 6% 5% 5% 6% 6% 7% 10% 46%	4102
	21st to end	Day	3 5% 2 6% 5% 5% 5% 4 8% 8% 51%	4825
June	1st to 10th	Day	2 3 1 4 4 4 5% 4 6% 7% 59%	2660
	11th to 20th	Day	3 2 1 5% 4 3 4 4 6% 7% 63%	2660
	21st to end	Day	2 4 1 4 4 4 5% 4 5% 8% 59%	2660
July	1st to 10th	Day	3 3 1 4 3 3 4 4 5% 4 66%	4400
	11th to 20th	Day	2 3 1 4 4 6% 8% 8% 11% 12% 42%	4110
	21st to end	Day	4 4 2 5% 4 5% 5% 5% 6% 7% 52%	4454
August	1st to 10th	Day	5% 4 2 6% 6% 7% 8% 7% 10% 12% 34%	4092
	11th to 20th	Day	4 4 2 6% 6% 6% 6% 5% 7% 8% 46%	3914
	21st to end	Day	3 3 2 6% 5% 6% 6% 6% 8% 11% 44%	4180
September	1st to 10th	Day	6% 4 2 7% 5% 5% 5% 4 4 7% 51%	2280
	11th to 20th	Day	5% 3 2 5% 4 5% 4 4 6% 7% 54%	2265
	21st to end	Day	4 4 2 5% 4 4 4 3 4 5% 62%	1986
October	1st to 10th	Day	6% 5% 2 6% 4 3 3 3 5% 6% 58%	1800
	11th to 20th	Day	4 4 2 4 3 3 2 3 4 6% 67%	1800
	21st to end	Day	4 8% 2 4 3 3 2 3 4 5% 62%	1980
November	1st to 10th	Day	1 5% 1 4 3 2 2 3 5% 6% 68%	1838
	11th to 20th	Day	2 8% 2 5% 2 3 3 3 5% 4 63%	1682
	21st to end	Day	2 6% 3 8% 3 3 4 3 3 5% 59%	1520
December	1st to 10th	Day	2 10% 3 8% 5% 3 3 3 6% 4 52%	1520
	11th to 20th	Day	2 10% 5% 10% 4 4 4 4 5% 7% 44%	1926
	21st to end	Day	1 8% 4 10% 5% 5% 4 3 5% 6% 49%	2794
January	1st to 10th	Night	9% 6% 16% 5% 5% 4 3 4 5% 42%	4211
	11th to 20th	Night	1 13% 5% 8% 6% 6% 5% 5% 4 7% 41%	4110
	21st to end	Night	2 12% 5% 10% 4 3 4 3 4 6% 47%	4521
February	1st to 10th	Night	1 11% 5% 9% 5% 4 4 3 3 6% 49%	2470
	11th to 20th	Night	2 8% 4 9% 4 4 4 3 5% 6% 48%	2365
	21st to end	Night	2 11% 3 9% 6% 4 4 3 5% 5% 47%	1880
March	1st to 10th	Night	1 9% 3 7% 5% 4 6% 4 5% 7% 49%	3430
	11th to 20th	Night	1 11% 3 8% 4 5% 6% 4 6% 7% 45%	3490
	21st to end	Night	1 12% 6% 7% 5% 5% 5% 5% 9% 8% 37%	3811
April	1st to 10th	Night	3 8% 3 6% 4 4 5% 4 7% 7% 49%	1900
	11th to 20th	Night	2 12% 4 6% 3 4 5% 4 6% 7% 47%	1877
	21st to end	Night	4 9% 3 5% 4 3 5% 4 6% 7% 51%	1900
May	1st to 10th	Night	3 8% 2 4 4 3 4 3 7% 8% 53%	2925
	11th to 20th	Night	4 5% 1 4 3 4 4 4 6% 9% 56%	2785
	21st to end	Night	3 3 1 3 2 3 4 3 5% 6% 67%	2762
June	1st to 10th	Night	2 2 1 2 2 2 2 4 6% 8% 68%	1520
	11th to 20th	Night	2 2 1 2 2 3 4 3 5% 6% 72%	1520
	21st to end	Night	1 1 1 3 2 3 4 4 5% 8% 66%	1520
July	1st to 10th	Night	1 2 1 3 2 3 3 3 5% 6% 71%	2564
	11th to 20th	Night	1 1 1 3 3 3 5% 5% 9% 12% 57%	2860
	21st to end	Night	2 2 1 4 4 5% 5% 6% 7% 10% 55%	3109
August	1st to 10th	Night	3 2 1 4 5% 5% 7% 6% 10% 13% 43%	2847
	11th to 20th	Night	2 2 1 3 3 4 7% 5% 8% 9% 55%	2925
	21st to end	Night	3 3 1 5% 4 5% 5% 5% 7% 9% 53%	3487
September	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 10% 59%	1900
	11th to 20th	Night	3 2 1 3 2 4 5% 4 6% 7% 63%	1911
	21st to end	Night	3 3 1 3 2 2 2 3 3 4 72%	2161
October	1st to 10th	Night	4 4 1 4 3 3 4 2 4 8% 63%	2160
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 5% 72%	2160
	21st to end	Night	3 8% 2 4 2 3 2 2 3 4 65%	2376
November	1st to 10th	Night	2 5% 1 3 2 2 3 3 6% 7% 66%	2220
	11th to 20th	Night	2 8% 2 4 3 3 3 2 4 5% 63%	2496
	21st to end	Night	2 9% 4 7% 3 3 3 3 4 7% 57%	2660
December	1st to 10th	Night	2 8% 3 7% 4 3 4 3 4 7% 55%	2660
	11th to 20th	Night	2 9% 4 8% 5% 5% 5% 5% 6% 7% 46%	3271
	21st to end	Night	1 8% 4 10% 5% 4 4 3 4 5% 49%	4873

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	42% 6% 15% 18% 16% 3	2772
	11th to 20th	Day	44% 6% 16% 21% 11% 2	2860
	21st to end	Day	41% 5% 9% 25% 16% 4	3146
February	1st to 10th	Day	43% 7% 14% 16% 14% 6%	1710
	11th to 20th	Day	40% 6% 9% 20% 19% 5%	1708
	21st to end	Day	44% 5% 7% 18% 20% 5%	1570
March	1st to 10th	Day	37% 6% 10% 23% 21% 4	3444
	11th to 20th	Day	44% 8% 14% 23% 9% 2	3490
	21st to end	Day	49% 8% 11% 18% 13% 2	3839
April	1st to 10th	Day	36% 7% 10% 22% 19% 6%	2280
	11th to 20th	Day	40% 7% 10% 19% 20% 4	2254
	21st to end	Day	38% 7% 11% 24% 18% 2	2280
May	1st to 10th	Day	35% 7% 10% 19% 22% 7%	4041
	11th to 20th	Day	31% 9% 13% 21% 21% 6%	4105
	21st to end	Day	28% 6% 11% 18% 31% 6%	4825
June	1st to 10th	Day	24% 7% 11% 22% 25% 12%	2660
	11th to 20th	Day	22% 5% 8% 15% 27% 22%	2660
	21st to end	Day	25% 6% 10% 15% 24% 21%	2660
July	1st to 10th	Day	21% 6% 7% 8% 13% 44%	4331
	11th to 20th	Day	29% 11% 13% 19% 16% 11%	4041
	21st to end	Day	30% 10% 10% 13% 16% 20%	4314
August	1st to 10th	Day	41% 11% 17% 14% 10% 7%	4078
	11th to 20th	Day	36% 10% 14% 11% 21% 9%	3953
	21st to end	Day	32% 9% 12% 17% 22% 8%	4179
September	1st to 10th	Day	35% 7% 9% 13% 22% 14%	2280
	11th to 20th	Day	30% 9% 10% 15% 26% 11%	2265
	21st to end	Day	27% 5% 8% 20% 30% 10%	1986
October	1st to 10th	Day	31% 6% 10% 21% 24% 9%	1800
	11th to 20th	Day	21% 4 7% 24% 34% 10%	1800
	21st to end	Day	27% 5% 8% 27% 26% 6%	1980
November	1st to 10th	Day	20% 5% 11% 25% 32% 7%	1838
	11th to 20th	Day	24% 5% 10% 31% 26% 6%	1682
	21st to end	Day	28% 6% 9% 25% 21% 11%	1520
December	1st to 10th	Day	35% 8% 12% 24% 16% 5%	1520
	11th to 20th	Day	40% 7% 10% 18% 23% 3	1924
	21st to end	Day	34% 6% 12% 17% 20% 11%	2794
January	1st to 10th	Night	44% 5% 12% 20% 15% 4	4211
	11th to 20th	Night	44% 7% 13% 22% 13% 2	4110
	21st to end	Night	38% 6% 8% 28% 16% 3	4521
February	1st to 10th	Night	38% 6% 13% 20% 18% 6%	2470
	11th to 20th	Night	36% 6% 11% 23% 18% 6%	2366
	21st to end	Night	38% 5% 10% 19% 22% 6%	1880
March	1st to 10th	Night	31% 7% 10% 22% 26% 3	3430
	11th to 20th	Night	35% 10% 13% 27% 13% 2	3490
	21st to end	Night	44% 9% 15% 19% 12% 2	3811
April	1st to 10th	Night	34% 8% 12% 22% 20% 5%	1900
	11th to 20th	Night	35% 8% 12% 20% 21% 5%	1877
	21st to end	Night	33% 7% 12% 26% 20% 2	1900
May	1st to 10th	Night	27% 8% 9% 23% 29% 3	2925
	11th to 20th	Night	21% 8% 12% 32% 23% 3	2786
	21st to end	Night	17% 6% 11% 19% 35% 12%	2762
June	1st to 10th	Night	14% 7% 10% 25% 33% 12%	1520
	11th to 20th	Night	14% 6% 8% 17% 30% 26%	1520
	21st to end	Night	15% 6% 10% 18% 28% 23%	1520
July	1st to 10th	Night	16% 6% 9% 10% 13% 46%	2524
	11th to 20th	Night	17% 8% 14% 31% 16% 14%	2806
	21st to end	Night	23% 10% 14% 17% 17% 19%	3011
August	1st to 10th	Night	28% 11% 24% 15% 12% 10%	2838
	11th to 20th	Night	21% 9% 25% 13% 18% 14%	2952
	21st to end	Night	24% 8% 15% 21% 23% 8%	3487
September	1st to 10th	Night	22% 8% 13% 17% 26% 14%	1900
	11th to 20th	Night	19% 7% 13% 19% 28% 14%	1911
	21st to end	Night	17% 5% 8% 24% 35% 11%	2161
October	1st to 10th	Night	23% 5% 12% 22% 27% 11%	2160
	11th to 20th	Night	16% 5% 9% 23% 35% 11%	2160
	21st to end	Night	24% 4 8% 29% 26% 8%	2376
November	1st to 10th	Night	19% 7% 12% 25% 28% 9%	2220
	11th to 20th	Night	23% 5% 10% 28% 28% 6%	2496
	21st to end	Night	29% 5% 8% 22% 24% 11%	2660
December	1st to 10th	Night	31% 7% 13% 21% 21% 7%	2660
	11th to 20th	Night	34% 9% 10% 20% 23% 3	3272
	21st to end	Night	37% 7% 9% 16% 22% 9%	4873

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% 18% 29% 27% 12% 2	270
	11th to 20th	Day	12% 23% 32% 23% 10%	270
	21st to end	Day	4 17% 39% 28% 9% 2	297
February	1st to 10th	Day	14% 29% 33% 21% 3 1	270
	11th to 20th	Day	15% 32% 33% 14% 5%	270
	21st to end	Day	20% 28% 31% 18% 3	225
March	1st to 10th	Day	17% 33% 28% 19% 3	460
	11th to 20th	Day	11% 31% 30% 22% 6%	460
	21st to end	Day	18% 35% 30% 14% 3	506
April	1st to 10th	Day	15% 28% 35% 17% 5% 1	460
	11th to 20th	Day	17% 33% 32% 13% 4	452
	21st to end	Day	13% 31% 35% 16% 5%	460
May	1st to 10th	Day	16% 28% 35% 15% 5%	463
	11th to 20th	Day	9% 21% 35% 24% 8% 2	506
	21st to end	Day	10% 20% 31% 24% 12% 3	734
June	1st to 10th	Day	5% 11% 31% 33% 16% 4	680
	11th to 20th	Day	5% 14% 35% 30% 12% 4	680
	21st to end	Day	3 12% 34% 31% 18% 3	680
July	1st to 10th	Day	3 5% 23% 41% 24% 5%	654
	11th to 20th	Day	4 4 23% 38% 23% 8%	484
	21st to end	Day	6% 3 24% 38% 23% 6%	531
August	1st to 10th	Day	8% 6% 25% 36% 19% 6%	487
	11th to 20th	Day	5% 4 31% 37% 18% 4	477
	21st to end	Day	3 5% 32% 37% 19% 4	539
September	1st to 10th	Day	8% 8% 27% 33% 20% 5%	490
	11th to 20th	Day	5% 13% 41% 28% 10% 2	490
	21st to end	Day	7% 17% 30% 30% 13% 4	400
October	1st to 10th	Day	10% 21% 24% 25% 17% 4	270
	11th to 20th	Day	4 20% 31% 26% 16% 2	270
	21st to end	Day	8% 20% 33% 28% 11% 1	297
November	1st to 10th	Day	11% 28% 24% 26% 10% 1	270
	11th to 20th	Day	5% 21% 32% 24% 15% 2	270
	21st to end	Day	8% 21% 29% 27% 13% 2	270
December	1st to 10th	Day	9% 25% 33% 22% 11% 1	270
	11th to 20th	Day	11% 19% 30% 27% 10% 2	270
	21st to end	Day	17% 20% 33% 22% 8% 1	297
January	1st to 10th	Night	7% 11% 29% 32% 16% 5%	822
	11th to 20th	Night	7% 13% 30% 30% 16% 3	760
	21st to end	Night	6% 10% 31% 35% 15% 4	836
February	1st to 10th	Night	9% 14% 35% 30% 9% 2	760
	11th to 20th	Night	6% 15% 39% 28% 10% 1	744
	21st to end	Night	9% 16% 41% 27% 7%	628
March	1st to 10th	Night	8% 19% 33% 29% 9% 2	760
	11th to 20th	Night	5% 12% 32% 33% 18% 1	760
	21st to end	Night	7% 20% 32% 29% 10% 1	831
April	1st to 10th	Night	10% 16% 37% 30% 6% 1	570
	11th to 20th	Night	9% 20% 33% 28% 9% 1	563
	21st to end	Night	9% 17% 30% 28% 13% 2	570
May	1st to 10th	Night	6% 13% 35% 33% 12% 1	570
	11th to 20th	Night	8% 8% 27% 37% 17% 3	561
	21st to end	Night	6% 13% 29% 34% 17% 2	617
June	1st to 10th	Night	3 7% 25% 37% 25% 2	570
	11th to 20th	Night	3 10% 27% 41% 17% 2	570
	21st to end	Night	2 4 21% 45% 27% 3	570
July	1st to 10th	Night	3 1 18% 39% 37% 3	555
	11th to 20th	Night	2 3 8% 40% 42% 5%	552
	21st to end	Night	3 2 10% 36% 45% 4	624
August	1st to 10th	Night	4 2 11% 39% 38% 6%	567
	11th to 20th	Night	3 2 12% 42% 36% 5%	564
	21st to end	Night	3 2 15% 42% 31% 7%	627
September	1st to 10th	Night	3 3 15% 44% 33% 3	570
	11th to 20th	Night	3 3 23% 38% 29% 5%	581
	21st to end	Night	4 8% 19% 37% 24% 9%	756
October	1st to 10th	Night	6% 11% 25% 37% 18% 2	720
	11th to 20th	Night	3 9% 28% 33% 21% 5%	720
	21st to end	Night	9% 9% 25% 32% 20% 5%	792
November	1st to 10th	Night	6% 12% 26% 33% 19% 4	740
	11th to 20th	Night	7% 12% 29% 31% 16% 3	950
	21st to end	Night	8% 13% 28% 32% 15% 3	950
December	1st to 10th	Night	7% 14% 31% 33% 12% 2	950
	11th to 20th	Night	8% 17% 29% 29% 16% 1	950
	21st to end	Night	10% 13% 36% 32% 8% 1	1045

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