Solar Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Solar Hills Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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	4 7% 2 5% 4 4 4 4 6% 7% 53%	101126
	Night	5% 8% 3 6% 4 3 4 3 5% 7% 53%	97909
Transparency	Day	26% 9% 13% 20% 21% 11%	100885
	Night	27% 8% 13% 22% 21% 9%	97739
Seeing	Day	7% 10% 26% 31% 20% 6%	15290
	Night	7% 5% 24% 40% 22% 3	25405

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	3 10% 5% 12% 5% 5% 4 4 5% 7% 41%	2744
	11th to 20th	Day	5% 16% 3 9% 4 4 4 3 6% 7% 41%	2860
	21st to end	Day	3 12% 4 7% 4 3 3 3 4 6% 51%	3146
February	1st to 10th	Day	5% 11% 4 8% 4 5% 4 3 6% 7% 43%	1710
	11th to 20th	Day	5% 15% 4 6% 5% 3 3 4 5% 6% 45%	1693
	21st to end	Day	3 12% 4 10% 6% 4 4 3 4 6% 44%	1570
March	1st to 10th	Day	4 12% 3 6% 4 4 4 4 6% 6% 46%	3441
	11th to 20th	Day	4 10% 3 7% 4 4 4 4 6% 7% 47%	3490
	21st to end	Day	3 13% 4 8% 6% 5% 5% 5% 6% 8% 38%	3840
April	1st to 10th	Day	6% 7% 3 6% 4 3 3 4 5% 8% 50%	2280
	11th to 20th	Day	5% 10% 3 7% 4 5% 5% 4 5% 6% 46%	2251
	21st to end	Day	4 9% 3 4 3 4 5% 4 5% 8% 50%	2280
May	1st to 10th	Day	5% 9% 2 6% 4 5% 5% 4 6% 7% 47%	4066
	11th to 20th	Day	4 4 1 4 4 5% 5% 4 7% 8% 53%	4129
	21st to end	Day	4 5% 1 4 4 4 4 4 5% 7% 57%	4825
June	1st to 10th	Day	3 3 1 4 3 3 3 4 5% 8% 62%	2660
	11th to 20th	Day	4 3 1 3 3 4 3 3 5% 6% 66%	2660
	21st to end	Day	2 3 1 3 3 3 4 4 5% 8% 64%	2660
July	1st to 10th	Day	2 2 1 3 3 3 4 3 4 5% 69%	4430
	11th to 20th	Day	2 2 1 3 3 5% 6% 7% 11% 13% 49%	4112
	21st to end	Day	3 3 1 4 4 4 5% 4 6% 8% 57%	4454
August	1st to 10th	Day	3 3 1 5% 4 5% 7% 7% 10% 14% 40%	4092
	11th to 20th	Day	3 3 2 5% 4 5% 6% 5% 8% 8% 52%	3921
	21st to end	Day	3 3 1 4 5% 5% 6% 5% 8% 9% 51%	4180
September	1st to 10th	Day	5% 3 1 4 3 4 4 4 5% 6% 59%	2280
	11th to 20th	Day	4 3 1 5% 3 4 4 4 5% 7% 61%	2262
	21st to end	Day	4 3 1 4 3 3 3 3 3 6% 67%	2008
October	1st to 10th	Day	7% 4 1 3 2 2 4 3 6% 6% 62%	1900
	11th to 20th	Day	4 5% 2 3 3 2 3 3 4 5% 67%	1900
	21st to end	Day	5% 6% 2 5% 2 3 3 2 3 5% 64%	2025
November	1st to 10th	Day	3 4 2 3 3 3 3 2 4 6% 68%	1829
	11th to 20th	Day	4 6% 2 5% 3 3 3 2 4 4 63%	1668
	21st to end	Day	4 8% 3 6% 3 3 3 2 4 4 60%	1520
December	1st to 10th	Day	6% 11% 3 8% 3 3 3 2 5% 4 53%	1520
	11th to 20th	Day	5% 12% 3 9% 4 3 3 3 5% 6% 46%	1926
	21st to end	Day	4 11% 4 8% 4 3 4 3 4 6% 48%	2794
January	1st to 10th	Night	3 14% 6% 12% 4 4 3 3 4 5% 43%	4225
	11th to 20th	Night	7% 18% 4 7% 4 3 3 2 4 6% 42%	4110
	21st to end	Night	5% 16% 4 7% 4 3 3 2 4 5% 46%	4521
February	1st to 10th	Night	5% 12% 4 7% 4 3 3 2 4 5% 49%	2470
	11th to 20th	Night	6% 10% 4 8% 4 3 3 3 4 6% 48%	2374
	21st to end	Night	4 11% 4 7% 5% 4 4 4 5% 6% 48%	1884
March	1st to 10th	Night	4 13% 3 7% 4 4 4 4 5% 6% 47%	3430
	11th to 20th	Night	5% 11% 3 7% 4 4 4 4 5% 7% 47%	3490
	21st to end	Night	5% 15% 4 7% 5% 5% 5% 5% 6% 7% 37%	3811
April	1st to 10th	Night	6% 10% 3 6% 5% 3 4 4 5% 7% 47%	1900
	11th to 20th	Night	7% 10% 3 7% 4 4 5% 4 5% 5% 46%	1877
	21st to end	Night	9% 8% 3 4 3 4 4 4 6% 6% 51%	1900
May	1st to 10th	Night	8% 9% 2 5% 3 3 4 4 6% 7% 49%	2901
	11th to 20th	Night	6% 4 1 4 4 4 4 4 6% 9% 54%	2771
	21st to end	Night	7% 4 1 3 3 3 3 3 4 5% 64%	2762
June	1st to 10th	Night	3 3 1 3 3 3 4 3 6% 7% 64%	1520
	11th to 20th	Night	3 2 1 4 2 3 4 3 5% 5% 69%	1520
	21st to end	Night	3 2 1 2 3 3 4 5% 6% 7% 65%	1520
July	1st to 10th	Night	2 2 1 3 3 3 3 3 5% 5% 71%	2540
	11th to 20th	Night	1 1 1 3 3 4 5% 5% 11% 12% 55%	2853
	21st to end	Night	2 3 1 4 4 5% 5% 5% 7% 10% 55%	3109
August	1st to 10th	Night	3 3 2 5% 5% 5% 7% 6% 10% 12% 42%	2847
	11th to 20th	Night	3 3 1 4 4 5% 6% 5% 6% 10% 54%	2904
	21st to end	Night	3 3 2 5% 5% 5% 5% 5% 7% 9% 52%	3487
September	1st to 10th	Night	4 2 2 4 4 3 4 3 6% 9% 59%	1900
	11th to 20th	Night	4 3 1 4 3 4 4 3 5% 7% 64%	1914
	21st to end	Night	5% 3 1 3 2 3 2 2 3 5% 71%	2171
October	1st to 10th	Night	5% 5% 1 4 3 3 4 2 4 6% 63%	2280
	11th to 20th	Night	3 5% 1 3 2 3 3 3 3 6% 69%	2280
	21st to end	Night	6% 7% 2 4 2 3 2 1 3 4 65%	2436
November	1st to 10th	Night	4 5% 1 3 3 2 3 3 5% 5% 66%	2229
	11th to 20th	Night	6% 7% 1 5% 3 2 2 3 3 4 64%	2509
	21st to end	Night	6% 9% 2 5% 3 2 3 3 4 5% 58%	2660
December	1st to 10th	Night	6% 11% 3 6% 3 2 3 3 3 6% 54%	2660
	11th to 20th	Night	5% 12% 4 7% 4 3 4 3 6% 8% 44%	3271
	21st to end	Night	5% 12% 4 9% 4 3 3 3 3 5% 48%	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	33% 12% 20% 22% 12% 1	2745
	11th to 20th	Day	32% 17% 20% 21% 10% 1	2860
	21st to end	Day	32% 9% 15% 31% 10% 3	3146
February	1st to 10th	Day	40% 7% 17% 20% 12% 4	1710
	11th to 20th	Day	38% 7% 12% 22% 19% 4	1702
	21st to end	Day	39% 6% 10% 21% 20% 3	1570
March	1st to 10th	Day	26% 10% 16% 24% 20% 3	3441
	11th to 20th	Day	29% 12% 16% 29% 11% 2	3490
	21st to end	Day	32% 17% 16% 19% 14% 2	3840
April	1st to 10th	Day	31% 6% 12% 23% 20% 8%	2280
	11th to 20th	Day	35% 8% 13% 19% 20% 6%	2254
	21st to end	Day	29% 7% 14% 24% 21% 4	2280
May	1st to 10th	Day	27% 9% 16% 20% 22% 7%	4066
	11th to 20th	Day	22% 11% 13% 24% 23% 7%	4132
	21st to end	Day	20% 7% 14% 18% 33% 8%	4825
June	1st to 10th	Day	19% 5% 9% 20% 29% 18%	2660
	11th to 20th	Day	18% 5% 8% 13% 25% 30%	2660
	21st to end	Day	17% 5% 9% 15% 25% 28%	2660
July	1st to 10th	Day	17% 6% 7% 9% 18% 44%	4361
	11th to 20th	Day	20% 9% 9% 26% 20% 15%	4042
	21st to end	Day	22% 9% 10% 17% 17% 24%	4314
August	1st to 10th	Day	29% 10% 19% 19% 12% 11%	4078
	11th to 20th	Day	28% 8% 13% 15% 24% 13%	3960
	21st to end	Day	26% 8% 12% 17% 23% 13%	4179
September	1st to 10th	Day	26% 8% 8% 13% 26% 20%	2280
	11th to 20th	Day	21% 8% 10% 16% 27% 17%	2262
	21st to end	Day	20% 6% 6% 17% 36% 14%	2008
October	1st to 10th	Day	22% 7% 10% 23% 26% 11%	1900
	11th to 20th	Day	19% 4 7% 24% 35% 9%	1900
	21st to end	Day	23% 5% 11% 28% 28% 5%	2025
November	1st to 10th	Day	16% 7% 12% 24% 34% 6%	1829
	11th to 20th	Day	24% 5% 10% 33% 23% 4	1668
	21st to end	Day	28% 6% 10% 28% 23% 5%	1520
December	1st to 10th	Day	34% 7% 16% 23% 17% 3	1520
	11th to 20th	Day	37% 6% 13% 23% 19% 1	1924
	21st to end	Day	33% 9% 15% 17% 21% 5%	2794
January	1st to 10th	Night	37% 11% 17% 21% 14% 1	4225
	11th to 20th	Night	32% 16% 19% 22% 10% 1	4110
	21st to end	Night	37% 9% 15% 27% 11% 2	4521
February	1st to 10th	Night	38% 6% 15% 23% 16% 2	2470
	11th to 20th	Night	35% 7% 14% 24% 18% 3	2375
	21st to end	Night	34% 6% 13% 23% 21% 4	1884
March	1st to 10th	Night	28% 12% 13% 22% 23% 2	3430
	11th to 20th	Night	28% 12% 16% 28% 13% 2	3490
	21st to end	Night	34% 16% 15% 21% 12% 2	3811
April	1st to 10th	Night	33% 6% 13% 20% 20% 7%	1900
	11th to 20th	Night	34% 8% 11% 19% 20% 8%	1877
	21st to end	Night	29% 8% 14% 22% 23% 4	1900
May	1st to 10th	Night	25% 8% 14% 22% 26% 5%	2901
	11th to 20th	Night	20% 8% 16% 29% 20% 7%	2772
	21st to end	Night	18% 6% 10% 18% 31% 17%	2762
June	1st to 10th	Night	15% 7% 9% 20% 29% 19%	1520
	11th to 20th	Night	16% 5% 8% 14% 21% 36%	1520
	21st to end	Night	16% 5% 8% 16% 25% 30%	1520
July	1st to 10th	Night	16% 5% 8% 10% 15% 46%	2500
	11th to 20th	Night	16% 7% 11% 34% 15% 18%	2800
	21st to end	Night	21% 9% 14% 18% 17% 21%	3011
August	1st to 10th	Night	30% 9% 21% 16% 12% 12%	2838
	11th to 20th	Night	26% 6% 20% 14% 16% 18%	2931
	21st to end	Night	27% 7% 11% 18% 23% 14%	3487
September	1st to 10th	Night	20% 6% 11% 17% 23% 23%	1900
	11th to 20th	Night	18% 7% 13% 16% 26% 20%	1914
	21st to end	Night	17% 4 6% 18% 39% 15%	2171
October	1st to 10th	Night	22% 5% 10% 21% 27% 15%	2280
	11th to 20th	Night	18% 4 9% 22% 34% 12%	2280
	21st to end	Night	24% 3 8% 29% 29% 6%	2436
November	1st to 10th	Night	19% 6% 12% 26% 30% 7%	2229
	11th to 20th	Night	24% 4 10% 31% 27% 4	2509
	21st to end	Night	28% 5% 9% 25% 27% 5%	2660
December	1st to 10th	Night	31% 6% 16% 24% 19% 3	2660
	11th to 20th	Night	35% 8% 13% 23% 21% 1	3272
	21st to end	Night	36% 7% 12% 19% 23% 2	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	9% 9% 24% 36% 16% 7%	270
	11th to 20th	Day	7% 12% 28% 36% 15% 2	270
	21st to end	Day	6% 6% 25% 43% 15% 5%	297
February	1st to 10th	Day	11% 12% 32% 34% 8% 3	270
	11th to 20th	Day	13% 14% 34% 28% 10% 1	270
	21st to end	Day	11% 14% 36% 29% 8% 2	225
March	1st to 10th	Day	12% 19% 30% 28% 9% 1	457
	11th to 20th	Day	9% 16% 33% 27% 13% 2	460
	21st to end	Day	14% 24% 32% 22% 8%	506
April	1st to 10th	Day	12% 19% 32% 26% 9% 2	460
	11th to 20th	Day	14% 24% 32% 20% 9% 2	452
	21st to end	Day	10% 21% 35% 22% 11% 2	460
May	1st to 10th	Day	12% 20% 33% 24% 9% 2	463
	11th to 20th	Day	9% 12% 28% 27% 19% 5%	520
	21st to end	Day	5% 15% 25% 31% 20% 4	734
June	1st to 10th	Day	3 8% 26% 33% 24% 6%	680
	11th to 20th	Day	5% 8% 30% 33% 21% 4	680
	21st to end	Day	1 7% 25% 37% 24% 5%	680
July	1st to 10th	Day	1 2 14% 39% 35% 8%	671
	11th to 20th	Day	2 2 12% 37% 34% 13%	485
	21st to end	Day	5% 2 14% 33% 35% 12%	531
August	1st to 10th	Day	5% 3 17% 33% 32% 10%	487
	11th to 20th	Day	3 3 19% 35% 31% 9%	477
	21st to end	Day	4 1 16% 41% 28% 10%	539
September	1st to 10th	Day	6% 4 19% 30% 30% 10%	490
	11th to 20th	Day	5% 7% 29% 34% 20% 5%	490
	21st to end	Day	5% 11% 23% 25% 29% 8%	408
October	1st to 10th	Day	5% 12% 18% 28% 23% 14%	300
	11th to 20th	Day	4 9% 22% 33% 24% 7%	300
	21st to end	Day	7% 7% 26% 28% 27% 5%	311
November	1st to 10th	Day	6% 14% 29% 27% 19% 6%	270
	11th to 20th	Day	4 8% 30% 35% 16% 7%	270
	21st to end	Day	6% 9% 27% 33% 18% 6%	270
December	1st to 10th	Day	8% 8% 33% 31% 16% 4	270
	11th to 20th	Day	8% 8% 25% 34% 21% 4	270
	21st to end	Day	14% 9% 29% 32% 12% 3	297
January	1st to 10th	Night	7% 6% 23% 41% 20% 3	836
	11th to 20th	Night	7% 6% 27% 39% 18% 3	760
	21st to end	Night	10% 4 23% 44% 15% 3	836
February	1st to 10th	Night	9% 5% 33% 40% 12% 2	760
	11th to 20th	Night	8% 6% 34% 38% 12% 1	744
	21st to end	Night	10% 7% 36% 39% 8%	628
March	1st to 10th	Night	8% 8% 35% 37% 12% 1	760
	11th to 20th	Night	7% 4 28% 42% 20% 1	760
	21st to end	Night	8% 10% 31% 38% 12% 1	831
April	1st to 10th	Night	9% 9% 34% 38% 10% 1	570
	11th to 20th	Night	9% 12% 30% 37% 12% 1	563
	21st to end	Night	10% 7% 31% 35% 15% 2	570
May	1st to 10th	Night	8% 6% 29% 42% 14% 1	570
	11th to 20th	Night	7% 5% 20% 43% 22% 3	561
	21st to end	Night	6% 9% 24% 38% 20% 3	617
June	1st to 10th	Night	4 3 19% 43% 28% 3	570
	11th to 20th	Night	3 3 26% 43% 22% 3	570
	21st to end	Night	3 2 16% 44% 32% 3	570
July	1st to 10th	Night	4 1 11% 39% 41% 4	555
	11th to 20th	Night	3 1 7% 41% 45% 5%	552
	21st to end	Night	4 1 8% 34% 49% 4	624
August	1st to 10th	Night	5% 1 12% 36% 43% 4	567
	11th to 20th	Night	4 2 9% 42% 39% 5%	564
	21st to end	Night	3 2 12% 43% 35% 5%	627
September	1st to 10th	Night	3 2 11% 49% 32% 3	570
	11th to 20th	Night	3 3 18% 41% 30% 4	584
	21st to end	Night	5% 3 19% 38% 29% 6%	760
October	1st to 10th	Night	5% 5% 23% 43% 23% 2	760
	11th to 20th	Night	4 4 25% 41% 22% 4	760
	21st to end	Night	8% 5% 24% 37% 22% 4	812
November	1st to 10th	Night	5% 4 27% 39% 23% 3	749
	11th to 20th	Night	6% 7% 25% 39% 19% 4	950
	21st to end	Night	7% 6% 27% 36% 20% 3	950
December	1st to 10th	Night	8% 6% 27% 42% 15% 2	950
	11th to 20th	Night	11% 8% 25% 36% 18% 2	950
	21st to end	Night	11% 8% 27% 42% 10% 2	1045

Page generated at 2024-10-22 18:21:04. Version ac07

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