High Ridge Ranch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Ridge Ranch Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	12% 6% 2 5% 4 4 4 4 5% 7% 46%	101462
	Night	14% 6% 2 5% 3 3 3 3 5% 7% 50%	98738
Transparency	Day	35% 6% 10% 21% 19% 9%	105280
	Night	33% 6% 11% 20% 19% 11%	103047
Seeing	Day	15% 8% 23% 30% 20% 5%	14965
	Night	17% 7% 25% 34% 15% 1	24954

By Month

Percentage Cloud Cover SE (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	14% 9% 2 5% 2 2 3 2 4 5% 52%	2847
	11th to 20th	Day	18% 5% 1 3 2 2 2 2 4 4 56%	2850
	21st to end	Day	18% 7% 2 5% 3 3 3 3 4 8% 44%	3373
February	1st to 10th	Day	19% 7% 3 6% 3 3 3 2 4 5% 45%	1900
	11th to 20th	Day	18% 7% 2 4 3 3 3 3 4 6% 46%	1849
	21st to end	Day	19% 5% 2 5% 3 2 3 2 4 5% 50%	1570
March	1st to 10th	Day	16% 7% 3 7% 3 4 3 3 5% 5% 43%	3391
	11th to 20th	Day	21% 10% 3 8% 5% 4 4 3 4 5% 33%	3480
	21st to end	Day	16% 7% 2 6% 3 3 3 3 5% 6% 46%	3814
April	1st to 10th	Day	14% 7% 3 7% 4 3 4 3 4 6% 43%	2090
	11th to 20th	Day	21% 7% 2 5% 4 3 4 2 5% 5% 43%	2075
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 6% 44%	2413
May	1st to 10th	Day	24% 9% 3 6% 4 4 3 4 5% 6% 31%	4082
	11th to 20th	Day	15% 6% 2 7% 4 4 4 4 5% 6% 43%	4082
	21st to end	Day	12% 5% 2 6% 5% 4 6% 5% 7% 9% 37%	4477
June	1st to 10th	Day	6% 4 2 5% 4 4 6% 6% 7% 9% 48%	2470
	11th to 20th	Day	8% 4 2 4 5% 5% 5% 4 6% 10% 46%	2470
	21st to end	Day	8% 7% 2 6% 5% 6% 6% 5% 7% 9% 39%	2470
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 4 6% 8% 47%	4120
	11th to 20th	Day	5% 4 2 4 4 5% 5% 5% 7% 11% 48%	4120
	21st to end	Day	9% 6% 3 6% 5% 5% 6% 5% 7% 10% 37%	4465
August	1st to 10th	Day	1 1 1 2 3 3 4 3 5% 9% 68%	4055
	11th to 20th	Day	3 2 1 4 3 3 4 4 7% 10% 59%	3726
	21st to end	Day	4 3 1 5% 5% 6% 6% 5% 8% 11% 46%	4020
September	1st to 10th	Day	10% 6% 2 7% 6% 5% 4 4 5% 6% 44%	2090
	11th to 20th	Day	11% 7% 2 7% 5% 5% 5% 4 7% 7% 40%	2090
	21st to end	Day	8% 4 2 5% 4 4 5% 4 5% 6% 50%	2090
October	1st to 10th	Day	7% 4 2 5% 4 4 4 4 5% 7% 55%	2090
	11th to 20th	Day	12% 5% 2 5% 3 3 4 3 5% 5% 52%	1972
	21st to end	Day	11% 5% 2 4 4 3 3 2 3 5% 58%	2090
November	1st to 10th	Day	15% 6% 2 6% 4 3 4 3 5% 7% 44%	1958
	11th to 20th	Day	12% 6% 2 5% 4 3 3 3 5% 5% 51%	1860
	21st to end	Day	17% 6% 2 6% 4 3 3 3 4 5% 46%	1800
December	1st to 10th	Day	17% 6% 3 6% 4 3 3 3 4 6% 46%	1800
	11th to 20th	Day	16% 8% 3 5% 4 4 4 3 5% 5% 44%	2251
	21st to end	Day	17% 6% 1 3 2 2 3 2 4 4 55%	3162
January	1st to 10th	Night	19% 6% 2 4 2 2 2 2 3 6% 52%	4108
	11th to 20th	Night	14% 4 1 3 2 2 2 2 3 3 65%	4120
	21st to end	Night	21% 7% 2 6% 3 3 3 2 4 6% 43%	4308
February	1st to 10th	Night	18% 8% 3 5% 3 3 2 2 3 6% 47%	2280
	11th to 20th	Night	20% 7% 2 4 2 3 3 2 3 5% 50%	2218
	21st to end	Night	20% 6% 2 4 3 3 4 3 4 5% 46%	1884
March	1st to 10th	Night	18% 9% 2 5% 5% 4 4 3 5% 5% 41%	3463
	11th to 20th	Night	24% 10% 3 6% 4 4 4 3 4 4 35%	3480
	21st to end	Night	19% 7% 2 5% 4 3 3 3 4 6% 44%	3817
April	1st to 10th	Night	15% 7% 2 6% 3 3 3 3 5% 7% 46%	2090
	11th to 20th	Night	20% 7% 2 5% 3 3 3 3 3 5% 45%	2050
	21st to end	Night	20% 6% 2 4 4 3 3 3 3 5% 47%	1764
May	1st to 10th	Night	27% 9% 2 5% 3 3 3 3 4 5% 36%	2823
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 5% 7% 49%	2823
	21st to end	Night	15% 6% 2 6% 3 3 4 4 6% 9% 42%	3090
June	1st to 10th	Night	6% 4 1 4 3 3 3 4 5% 9% 59%	1710
	11th to 20th	Night	5% 4 1 4 4 4 4 4 5% 9% 57%	1710
	21st to end	Night	8% 4 1 4 4 4 4 4 7% 9% 51%	1710
July	1st to 10th	Night	6% 4 2 3 3 3 4 4 7% 10% 54%	2850
	11th to 20th	Night	3 4 2 4 4 4 5% 4 8% 9% 53%	2850
	21st to end	Night	11% 8% 3 6% 4 4 4 4 6% 10% 41%	3098
August	1st to 10th	Night	1 1 1 2 2 2 3 2 5% 7% 74%	2866
	11th to 20th	Night	3 3 1 3 2 3 4 4 6% 11% 59%	3113
	21st to end	Night	5% 4 1 4 4 3 4 4 7% 10% 55%	3640
September	1st to 10th	Night	9% 5% 1 5% 4 4 4 4 5% 8% 51%	2090
	11th to 20th	Night	9% 6% 2 6% 5% 4 5% 4 5% 8% 46%	2090
	21st to end	Night	8% 5% 2 5% 4 4 4 3 5% 8% 52%	2090
October	1st to 10th	Night	7% 4 2 4 3 4 3 3 4 6% 61%	2090
	11th to 20th	Night	14% 5% 1 4 2 3 3 2 5% 5% 54%	2186
	21st to end	Night	15% 5% 1 4 2 2 2 2 2 4 61%	2508
November	1st to 10th	Night	14% 8% 2 5% 3 3 3 2 4 5% 52%	2340
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 4 6% 55%	2535
	21st to end	Night	18% 6% 2 4 3 3 3 3 4 6% 48%	2600
December	1st to 10th	Night	17% 7% 1 4 3 3 3 3 5% 6% 49%	2600
	11th to 20th	Night	18% 8% 3 6% 3 3 3 2 3 5% 46%	3166
	21st to end	Night	20% 6% 2 3 2 2 2 2 3 5% 54%	4578

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	35% 4 4 17% 25% 15%	2848
	11th to 20th	Day	33% 3 6% 14% 28% 16%	2850
	21st to end	Day	39% 5% 5% 11% 29% 11%	3373
February	1st to 10th	Day	44% 3 4 12% 21% 16%	1900
	11th to 20th	Day	42% 4 7% 16% 18% 13%	1859
	21st to end	Day	39% 4 6% 17% 18% 16%	1570
March	1st to 10th	Day	42% 6% 6% 14% 21% 11%	3391
	11th to 20th	Day	54% 6% 6% 9% 16% 9%	3480
	21st to end	Day	38% 6% 9% 16% 20% 11%	3814
April	1st to 10th	Day	42% 6% 7% 16% 17% 12%	2090
	11th to 20th	Day	43% 6% 7% 15% 18% 11%	2075
	21st to end	Day	41% 6% 6% 20% 18% 9%	2413
May	1st to 10th	Day	53% 7% 8% 13% 14% 5%	4120
	11th to 20th	Day	40% 7% 8% 18% 21% 6%	4086
	21st to end	Day	39% 9% 13% 28% 11% 1	4489
June	1st to 10th	Day	30% 9% 12% 26% 19% 3	2470
	11th to 20th	Day	34% 7% 13% 24% 17% 5%	2470
	21st to end	Day	40% 8% 11% 23% 15% 3	2470
July	1st to 10th	Day	31% 9% 15% 37% 7% 1	4056
	11th to 20th	Day	27% 9% 17% 30% 16% 1	4051
	21st to end	Day	36% 10% 17% 29% 8%	4325
August	1st to 10th	Day	13% 5% 12% 41% 28% 1	4041
	11th to 20th	Day	19% 6% 23% 38% 12% 2	3762
	21st to end	Day	28% 11% 17% 25% 17% 2	4019
September	1st to 10th	Day	40% 7% 9% 19% 16% 9%	2090
	11th to 20th	Day	39% 9% 11% 18% 17% 5%	2090
	21st to end	Day	32% 7% 11% 20% 18% 13%	2090
October	1st to 10th	Day	18% 4 7% 12% 24% 36%	3480
	11th to 20th	Day	23% 5% 8% 18% 24% 21%	3251
	21st to end	Day	27% 4 5% 18% 32% 14%	3428
November	1st to 10th	Day	40% 5% 8% 18% 18% 11%	1958
	11th to 20th	Day	35% 5% 6% 17% 21% 15%	1860
	21st to end	Day	41% 4 6% 16% 19% 14%	1800
December	1st to 10th	Day	40% 4 8% 20% 20% 9%	1800
	11th to 20th	Day	41% 6% 7% 10% 21% 15%	2249
	21st to end	Day	35% 3 5% 14% 28% 15%	3162
January	1st to 10th	Night	35% 3 5% 15% 23% 19%	4108
	11th to 20th	Night	26% 2 4 17% 29% 21%	4120
	21st to end	Night	43% 4 5% 11% 24% 12%	4308
February	1st to 10th	Night	41% 3 6% 13% 20% 18%	2280
	11th to 20th	Night	41% 3 5% 16% 19% 16%	2218
	21st to end	Night	42% 4 6% 14% 17% 17%	1884
March	1st to 10th	Night	44% 6% 7% 16% 18% 9%	3463
	11th to 20th	Night	52% 7% 9% 10% 13% 9%	3480
	21st to end	Night	41% 6% 9% 15% 19% 10%	3817
April	1st to 10th	Night	39% 6% 8% 17% 17% 14%	2090
	11th to 20th	Night	42% 5% 8% 13% 17% 15%	2050
	21st to end	Night	42% 5% 8% 20% 17% 9%	1764
May	1st to 10th	Night	50% 6% 8% 16% 13% 6%	2850
	11th to 20th	Night	34% 7% 11% 22% 18% 8%	2824
	21st to end	Night	37% 8% 14% 27% 11% 2	3099
June	1st to 10th	Night	23% 7% 16% 30% 22% 3	1710
	11th to 20th	Night	24% 7% 15% 30% 20% 5%	1710
	21st to end	Night	29% 9% 17% 28% 15% 3	1710
July	1st to 10th	Night	24% 8% 26% 36% 6% 1	2805
	11th to 20th	Night	24% 9% 20% 31% 15% 1	2796
	21st to end	Night	38% 10% 21% 24% 7%	2999
August	1st to 10th	Night	10% 5% 16% 46% 22% 1	2856
	11th to 20th	Night	18% 9% 31% 32% 9% 2	3143
	21st to end	Night	23% 12% 21% 26% 16% 2	3640
September	1st to 10th	Night	32% 7% 15% 22% 17% 8%	2090
	11th to 20th	Night	36% 9% 13% 22% 15% 5%	2090
	21st to end	Night	29% 7% 14% 20% 17% 12%	2090
October	1st to 10th	Night	16% 4 7% 15% 21% 37%	3480
	11th to 20th	Night	22% 4 9% 16% 29% 20%	3633
	21st to end	Night	26% 3 5% 18% 32% 16%	4120
November	1st to 10th	Night	37% 4 8% 17% 21% 13%	2340
	11th to 20th	Night	32% 4 8% 19% 20% 17%	2535
	21st to end	Night	39% 5% 8% 16% 19% 15%	2600
December	1st to 10th	Night	38% 4 8% 19% 20% 12%	2600
	11th to 20th	Night	43% 4 4 11% 20% 18%	3167
	21st to end	Night	36% 3 4 13% 29% 14%	4578

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	22% 14% 36% 22% 5%	270
	11th to 20th	Day	29% 15% 29% 20% 7%	270
	21st to end	Day	21% 15% 37% 22% 5%	297
February	1st to 10th	Day	32% 14% 29% 20% 5%	270
	11th to 20th	Day	28% 18% 33% 17% 3	270
	21st to end	Day	27% 18% 42% 13%	225
March	1st to 10th	Day	24% 16% 41% 16% 3	270
	11th to 20th	Day	21% 17% 40% 16% 5%	270
	21st to end	Day	22% 17% 37% 19% 4 1	297
April	1st to 10th	Day	23% 16% 39% 19% 3	270
	11th to 20th	Day	24% 21% 30% 19% 6%	273
	21st to end	Day	20% 13% 39% 22% 6%	593
May	1st to 10th	Day	19% 10% 38% 26% 7%	653
	11th to 20th	Day	19% 9% 29% 33% 9% 2	675
	21st to end	Day	17% 8% 26% 33% 15% 1	734
June	1st to 10th	Day	8% 3 18% 39% 28% 5%	680
	11th to 20th	Day	9% 3 17% 44% 24% 3	680
	21st to end	Day	9% 2 17% 38% 28% 8%	680
July	1st to 10th	Day	8% 3 11% 37% 32% 9%	671
	11th to 20th	Day	5% 1 8% 36% 42% 7%	668
	21st to end	Day	6% 1 6% 35% 43% 9%	739
August	1st to 10th	Day	3 1 5% 37% 41% 13%	653
	11th to 20th	Day	6% 5% 40% 39% 10%	477
	21st to end	Day	5% 1 6% 33% 36% 19%	444
September	1st to 10th	Day	9% 2 10% 29% 36% 14%	300
	11th to 20th	Day	7% 1 8% 29% 41% 14%	300
	21st to end	Day	10% 2 11% 28% 39% 11%	300
October	1st to 10th	Day	5% 3 17% 38% 27% 9%	300
	11th to 20th	Day	12% 5% 21% 39% 18% 5%	300
	21st to end	Day	21% 12% 25% 25% 14% 3	330
November	1st to 10th	Day	19% 6% 28% 30% 13% 3	300
	11th to 20th	Day	20% 13% 27% 26% 11% 3	300
	21st to end	Day	24% 16% 33% 16% 9% 2	300
December	1st to 10th	Day	20% 11% 34% 24% 7% 3	300
	11th to 20th	Day	22% 17% 29% 23% 9%	300
	21st to end	Day	24% 11% 35% 22% 7%	306
January	1st to 10th	Night	20% 10% 29% 31% 8%	950
	11th to 20th	Night	21% 12% 29% 30% 8%	950
	21st to end	Night	22% 11% 30% 29% 8%	912
February	1st to 10th	Night	25% 13% 31% 25% 6%	760
	11th to 20th	Night	27% 11% 33% 25% 3	744
	21st to end	Night	26% 13% 41% 19% 2	628
March	1st to 10th	Night	24% 11% 35% 26% 4	603
	11th to 20th	Night	24% 9% 34% 28% 5%	570
	21st to end	Night	19% 10% 40% 27% 3	627
April	1st to 10th	Night	17% 13% 36% 29% 4	570
	11th to 20th	Night	23% 11% 35% 27% 4	563
	21st to end	Night	21% 11% 38% 22% 8%	570
May	1st to 10th	Night	20% 10% 36% 28% 5%	570
	11th to 20th	Night	15% 9% 32% 36% 9% 1	561
	21st to end	Night	16% 7% 30% 35% 12%	617
June	1st to 10th	Night	7% 3 21% 46% 22% 1	570
	11th to 20th	Night	5% 2 33% 45% 14% 1	570
	21st to end	Night	7% 3 18% 44% 23% 4	570
July	1st to 10th	Night	9% 3 14% 42% 29% 4	555
	11th to 20th	Night	3 1 11% 51% 31% 2	552
	21st to end	Night	6% 2 9% 48% 31% 3	624
August	1st to 10th	Night	1 10% 49% 35% 3	567
	11th to 20th	Night	5% 1 9% 50% 31% 5%	564
	21st to end	Night	7% 7% 38% 41% 6%	627
September	1st to 10th	Night	9% 2 10% 38% 37% 5%	570
	11th to 20th	Night	12% 1 8% 39% 38% 3	570
	21st to end	Night	12% 2 13% 34% 36% 4	570
October	1st to 10th	Night	8% 2 13% 45% 28% 5%	570
	11th to 20th	Night	15% 4 21% 37% 20% 2	666
	21st to end	Night	17% 8% 21% 31% 20% 2	836
November	1st to 10th	Night	15% 7% 20% 37% 19% 2	780
	11th to 20th	Night	15% 7% 26% 36% 14% 1	935
	21st to end	Night	20% 13% 27% 29% 11% 1	1000
December	1st to 10th	Night	22% 8% 28% 32% 9% 1	1000
	11th to 20th	Night	27% 9% 26% 31% 8%	1000
	21st to end	Night	22% 8% 30% 33% 8%	1063

Page generated at 2024-12-21 03:13:53. Version ac07

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