Elkhorn Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elkhorn Ranch clear sky chart from 2005-11-06 to 2024-11-10.

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 6% 2 6% 4 4 5% 4 6% 8% 51%	105186
	Night	2 5% 2 5% 3 3 4 3 6% 8% 59%	102676
Transparency	Day	28% 7% 12% 21% 23% 9%	104933
	Night	23% 6% 13% 26% 24% 8%	102519
Seeing	Day	13% 16% 33% 26% 11% 2	15555
	Night	7% 14% 37% 30% 11% 1	25579

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	4 2 7% 5% 3 3 3 6% 8% 59%	2538
	11th to 20th	Day	1 4 4 8% 4 4 4 4 6% 9% 53%	2680
	21st to end	Day	6% 4 7% 3 3 4 3 5% 8% 57%	3146
February	1st to 10th	Day	6% 3 8% 4 2 4 3 6% 7% 58%	1710
	11th to 20th	Day	3 2 5% 3 3 4 4 5% 8% 62%	1821
	21st to end	Day	6% 2 6% 4 4 4 3 5% 7% 59%	1570
March	1st to 10th	Day	1 6% 4 7% 3 3 3 3 4 7% 59%	3130
	11th to 20th	Day	2 12% 6% 7% 3 4 4 3 5% 8% 45%	3485
	21st to end	Day	1 8% 3 6% 3 3 4 3 6% 8% 54%	4036
April	1st to 10th	Day	3 8% 2 5% 5% 4 5% 4 7% 8% 50%	2280
	11th to 20th	Day	6% 10% 3 7% 4 5% 5% 3 5% 7% 44%	2251
	21st to end	Day	6% 11% 3 6% 5% 5% 5% 3 6% 7% 43%	2280
May	1st to 10th	Day	6% 11% 3 8% 5% 5% 4 4 6% 8% 40%	3947
	11th to 20th	Day	7% 8% 2 6% 4 5% 5% 5% 7% 9% 40%	4378
	21st to end	Day	4 5% 2 5% 3 4 5% 5% 8% 10% 50%	4825
June	1st to 10th	Day	5% 5% 2 5% 4 4 5% 5% 9% 10% 47%	2660
	11th to 20th	Day	5% 4 2 5% 4 5% 5% 5% 6% 9% 51%	2660
	21st to end	Day	3 4 2 6% 5% 5% 6% 6% 7% 9% 45%	2660
July	1st to 10th	Day	4 4 1 5% 5% 4 5% 5% 7% 7% 52%	4430
	11th to 20th	Day	4 4 2 7% 6% 7% 8% 6% 10% 9% 38%	4430
	21st to end	Day	6% 4 2 6% 5% 5% 7% 5% 7% 7% 44%	4627
August	1st to 10th	Day	7% 5% 3 9% 7% 5% 7% 6% 8% 9% 34%	4092
	11th to 20th	Day	4 4 2 5% 5% 6% 7% 6% 9% 10% 43%	3729
	21st to end	Day	4 5% 3 7% 5% 5% 6% 5% 8% 8% 44%	4180
September	1st to 10th	Day	6% 5% 2 6% 5% 5% 4 5% 6% 6% 51%	2280
	11th to 20th	Day	5% 4 2 4 4 4 4 4 5% 7% 57%	2271
	21st to end	Day	5% 4 2 4 3 3 4 3 5% 6% 62%	2088
October	1st to 10th	Day	3 4 1 4 3 3 3 3 4 4 68%	3170
	11th to 20th	Day	4 4 2 5% 3 3 4 4 7% 8% 56%	3150
	21st to end	Day	2 5% 2 4 2 2 3 2 4 6% 69%	3359
November	1st to 10th	Day	1 5% 1 4 2 2 2 3 5% 7% 66%	1754
	11th to 20th	Day	1 3 2 5% 3 3 3 2 5% 7% 65%	1710
	21st to end	Day	1 6% 2 5% 3 3 4 3 5% 7% 60%	1619
December	1st to 10th	Day	4 3 7% 3 3 4 2 5% 8% 60%	1520
	11th to 20th	Day	1 5% 2 5% 3 2 3 3 6% 11% 60%	1926
	21st to end	Day	7% 3 8% 4 3 4 3 6% 7% 55%	2794
January	1st to 10th	Night	4 3 10% 5% 4 3 3 4 7% 57%	4417
	11th to 20th	Night	2 1 3 4 3 4 5% 6% 7% 65%	4320
	21st to end	Night	1 7% 3 7% 4 3 3 3 4 6% 59%	4521
February	1st to 10th	Night	5% 3 6% 3 3 3 2 4 7% 63%	2470
	11th to 20th	Night	1 4 3 7% 3 2 3 3 5% 7% 63%	2244
	21st to end	Night	4 2 5% 3 4 3 3 5% 6% 64%	1884
March	1st to 10th	Night	1 7% 2 5% 3 3 3 3 5% 6% 61%	3734
	11th to 20th	Night	2 15% 4 6% 3 3 3 2 4 6% 52%	3490
	21st to end	Night	2 8% 3 5% 3 2 3 4 5% 8% 58%	3610
April	1st to 10th	Night	2 7% 2 5% 3 3 3 3 6% 7% 60%	1900
	11th to 20th	Night	5% 10% 3 4 3 3 4 3 5% 6% 54%	1877
	21st to end	Night	6% 11% 2 5% 4 3 3 2 4 7% 52%	1900
May	1st to 10th	Night	7% 8% 4 5% 3 3 4 3 6% 8% 49%	3020
	11th to 20th	Night	8% 7% 2 6% 3 3 4 3 6% 9% 49%	2524
	21st to end	Night	3 4 1 3 3 3 3 3 6% 8% 62%	2762
June	1st to 10th	Night	3 5% 2 3 2 3 4 3 6% 10% 59%	1520
	11th to 20th	Night	3 3 2 3 3 3 3 4 6% 9% 62%	1520
	21st to end	Night	3 3 1 4 3 4 5% 5% 8% 8% 56%	1520
July	1st to 10th	Night	4 4 1 4 4 3 4 4 5% 8% 59%	2540
	11th to 20th	Night	2 3 1 2 4 4 5% 4 8% 11% 57%	2540
	21st to end	Night	3 3 1 4 4 4 5% 5% 8% 9% 56%	2918
August	1st to 10th	Night	4 4 2 5% 4 6% 6% 6% 10% 10% 43%	2847
	11th to 20th	Night	3 3 1 4 3 3 4 5% 10% 12% 52%	3108
	21st to end	Night	3 4 1 6% 4 5% 5% 5% 9% 10% 48%	3487
September	1st to 10th	Night	5% 3 2 4 3 5% 5% 4 5% 9% 54%	1900
	11th to 20th	Night	6% 3 1 4 3 3 3 4 5% 8% 61%	1909
	21st to end	Night	5% 4 2 4 3 2 3 3 5% 7% 63%	2090
October	1st to 10th	Night	3 3 1 2 2 2 3 3 4 6% 72%	3798
	11th to 20th	Night	3 5% 1 3 2 3 3 3 5% 7% 64%	3778
	21st to end	Night	2 4 2 3 2 2 2 3 4 6% 70%	4166
November	1st to 10th	Night	1 3 2 3 3 3 3 3 5% 7% 68%	2529
	11th to 20th	Night	1 4 1 4 3 3 2 3 4 6% 69%	2470
	21st to end	Night	1 6% 2 4 2 3 3 3 5% 7% 63%	2559
December	1st to 10th	Night	1 4 1 4 3 2 4 3 5% 9% 64%	2660
	11th to 20th	Night	1 5% 2 5% 4 3 3 3 7% 9% 59%	3271
	21st to end	Night	1 8% 3 8% 4 3 4 3 5% 7% 54%	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	21% 4 15% 27% 25% 7%	2539
	11th to 20th	Day	23% 5% 17% 27% 22% 5%	2680
	21st to end	Day	27% 5% 12% 30% 20% 6%	3146
February	1st to 10th	Day	25% 4 14% 28% 20% 8%	1710
	11th to 20th	Day	19% 4 12% 28% 30% 7%	1831
	21st to end	Day	23% 5% 11% 22% 27% 13%	1570
March	1st to 10th	Day	23% 4 10% 22% 31% 10%	3130
	11th to 20th	Day	35% 8% 10% 30% 15% 3	3485
	21st to end	Day	25% 5% 13% 33% 20% 4	4036
April	1st to 10th	Day	27% 7% 13% 23% 21% 9%	2280
	11th to 20th	Day	38% 5% 12% 19% 19% 8%	2254
	21st to end	Day	38% 7% 10% 24% 18% 3	2280
May	1st to 10th	Day	35% 6% 13% 19% 19% 8%	3947
	11th to 20th	Day	35% 11% 13% 21% 17% 3	4382
	21st to end	Day	24% 6% 15% 18% 26% 10%	4825
June	1st to 10th	Day	28% 10% 15% 19% 19% 9%	2660
	11th to 20th	Day	27% 8% 10% 16% 21% 17%	2660
	21st to end	Day	30% 9% 11% 19% 20% 11%	2660
July	1st to 10th	Day	25% 8% 10% 14% 24% 19%	4361
	11th to 20th	Day	32% 11% 13% 21% 16% 7%	4355
	21st to end	Day	33% 9% 13% 15% 15% 15%	4481
August	1st to 10th	Day	41% 11% 16% 16% 12% 4	4078
	11th to 20th	Day	30% 10% 15% 14% 18% 13%	3765
	21st to end	Day	32% 8% 14% 16% 21% 9%	4179
September	1st to 10th	Day	32% 6% 10% 16% 23% 13%	2280
	11th to 20th	Day	26% 5% 9% 18% 28% 13%	2271
	21st to end	Day	23% 5% 7% 21% 34% 10%	2088
October	1st to 10th	Day	19% 4 7% 15% 31% 23%	3170
	11th to 20th	Day	22% 5% 9% 27% 29% 8%	3150
	21st to end	Day	17% 3 6% 20% 44% 11%	3359
November	1st to 10th	Day	17% 4 11% 21% 34% 14%	1754
	11th to 20th	Day	18% 4 7% 33% 29% 9%	1710
	21st to end	Day	22% 3 9% 25% 28% 12%	1619
December	1st to 10th	Day	21% 6% 14% 27% 24% 7%	1520
	11th to 20th	Day	19% 5% 14% 30% 26% 6%	1924
	21st to end	Day	26% 5% 11% 23% 26% 9%	2794
January	1st to 10th	Night	25% 4 12% 27% 27% 4	4417
	11th to 20th	Night	17% 3 13% 33% 25% 8%	4320
	21st to end	Night	25% 6% 14% 28% 22% 6%	4521
February	1st to 10th	Night	22% 3 14% 32% 22% 7%	2470
	11th to 20th	Night	22% 4 11% 30% 26% 8%	2244
	21st to end	Night	20% 4 8% 27% 28% 12%	1884
March	1st to 10th	Night	22% 4 11% 21% 35% 8%	3734
	11th to 20th	Night	33% 7% 10% 27% 20% 3	3490
	21st to end	Night	23% 6% 15% 34% 19% 2	3610
April	1st to 10th	Night	23% 4 12% 28% 24% 7%	1900
	11th to 20th	Night	30% 6% 11% 27% 20% 6%	1877
	21st to end	Night	33% 6% 12% 28% 19% 3	1900
May	1st to 10th	Night	31% 6% 12% 24% 18% 10%	3020
	11th to 20th	Night	30% 11% 16% 26% 15% 3	2525
	21st to end	Night	20% 6% 18% 23% 27% 6%	2762
June	1st to 10th	Night	21% 6% 22% 26% 15% 10%	1520
	11th to 20th	Night	17% 9% 12% 22% 23% 17%	1520
	21st to end	Night	23% 7% 14% 22% 23% 10%	1520
July	1st to 10th	Night	23% 8% 12% 19% 26% 12%	2500
	11th to 20th	Night	18% 7% 18% 35% 16% 5%	2492
	21st to end	Night	21% 9% 18% 26% 11% 15%	2826
August	1st to 10th	Night	31% 11% 24% 19% 12% 3	2838
	11th to 20th	Night	22% 9% 24% 19% 19% 6%	3138
	21st to end	Night	25% 10% 20% 21% 20% 3	3487
September	1st to 10th	Night	25% 7% 12% 23% 23% 10%	1900
	11th to 20th	Night	21% 7% 13% 22% 23% 14%	1909
	21st to end	Night	22% 5% 10% 24% 30% 8%	2090
October	1st to 10th	Night	14% 5% 8% 25% 34% 14%	3798
	11th to 20th	Night	18% 5% 10% 34% 25% 8%	3778
	21st to end	Night	15% 3 7% 28% 36% 11%	4166
November	1st to 10th	Night	16% 4 10% 25% 32% 13%	2529
	11th to 20th	Night	16% 4 9% 31% 30% 10%	2470
	21st to end	Night	20% 4 9% 25% 30% 11%	2559
December	1st to 10th	Night	18% 5% 15% 27% 25% 9%	2660
	11th to 20th	Night	21% 5% 13% 26% 28% 7%	3272
	21st to end	Night	27% 5% 11% 22% 26% 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	13% 20% 33% 23% 10% 1	270
	11th to 20th	Day	12% 26% 39% 19% 4	270
	21st to end	Day	6% 16% 45% 23% 6% 2	297
February	1st to 10th	Day	10% 33% 39% 15% 2 1	270
	11th to 20th	Day	9% 33% 41% 16% 1	270
	21st to end	Day	15% 24% 41% 19%	225
March	1st to 10th	Day	13% 20% 41% 20% 5% 1	270
	11th to 20th	Day	18% 22% 33% 21% 5%	455
	21st to end	Day	20% 24% 35% 16% 5%	506
April	1st to 10th	Day	17% 26% 33% 18% 5% 1	460
	11th to 20th	Day	26% 28% 28% 14% 3 1	452
	21st to end	Day	23% 22% 34% 15% 6% 1	460
May	1st to 10th	Day	19% 21% 37% 17% 6% 1	545
	11th to 20th	Day	19% 12% 32% 27% 9% 2	675
	21st to end	Day	14% 16% 31% 24% 13% 2	734
June	1st to 10th	Day	9% 11% 33% 30% 15% 3	680
	11th to 20th	Day	10% 14% 34% 29% 11% 2	680
	21st to end	Day	8% 11% 34% 31% 14% 2	680
July	1st to 10th	Day	7% 5% 27% 39% 17% 4	671
	11th to 20th	Day	8% 5% 23% 37% 23% 5%	668
	21st to end	Day	11% 4 20% 38% 22% 5%	639
August	1st to 10th	Day	11% 6% 30% 32% 17% 4	487
	11th to 20th	Day	7% 6% 33% 37% 13% 3	477
	21st to end	Day	12% 8% 32% 34% 13% 2	539
September	1st to 10th	Day	11% 11% 30% 31% 14% 3	490
	11th to 20th	Day	9% 14% 37% 28% 11% 1	481
	21st to end	Day	9% 16% 28% 28% 15% 4	300
October	1st to 10th	Day	11% 17% 30% 22% 16% 4	300
	11th to 20th	Day	10% 23% 32% 24% 8% 2	300
	21st to end	Day	13% 18% 40% 22% 6% 1	330
November	1st to 10th	Day	18% 18% 36% 17% 10% 1	297
	11th to 20th	Day	12% 23% 37% 22% 6% 1	270
	21st to end	Day	11% 19% 40% 22% 6% 1	270
December	1st to 10th	Day	16% 19% 39% 21% 5% 1	270
	11th to 20th	Day	11% 21% 42% 19% 6%	270
	21st to end	Day	14% 26% 35% 17% 6% 2	297
January	1st to 10th	Night	5% 22% 38% 27% 7% 2	950
	11th to 20th	Night	6% 24% 43% 19% 6% 1	879
	21st to end	Night	4 15% 49% 27% 5%	836
February	1st to 10th	Night	6% 23% 49% 19% 3	760
	11th to 20th	Night	5% 21% 49% 22% 4	744
	21st to end	Night	6% 23% 46% 22% 3	628
March	1st to 10th	Night	7% 21% 42% 24% 5% 1	760
	11th to 20th	Night	8% 14% 43% 26% 8%	760
	21st to end	Night	8% 17% 46% 25% 4	708
April	1st to 10th	Night	10% 19% 43% 24% 5%	570
	11th to 20th	Night	13% 18% 39% 24% 5% 1	563
	21st to end	Night	14% 16% 36% 26% 7% 1	570
May	1st to 10th	Night	13% 11% 34% 33% 10% 1	570
	11th to 20th	Night	15% 6% 27% 37% 13% 1	561
	21st to end	Night	9% 12% 28% 35% 14% 2	617
June	1st to 10th	Night	7% 6% 25% 43% 16% 2	570
	11th to 20th	Night	7% 7% 36% 35% 14% 2	570
	21st to end	Night	4 2 29% 45% 18% 2	570
July	1st to 10th	Night	8% 2 19% 44% 24% 3	555
	11th to 20th	Night	3 4 17% 40% 32% 4	552
	21st to end	Night	5% 1 17% 44% 31% 2	624
August	1st to 10th	Night	8% 3 18% 42% 27% 3	567
	11th to 20th	Night	7% 2 21% 45% 22% 3	564
	21st to end	Night	7% 4 22% 44% 21% 2	627
September	1st to 10th	Night	6% 3 22% 43% 22% 4	570
	11th to 20th	Night	8% 4 30% 40% 17% 2	570
	21st to end	Night	9% 8% 31% 35% 16% 2	570
October	1st to 10th	Night	7% 9% 41% 30% 10% 3	758
	11th to 20th	Night	4 13% 39% 34% 9% 2	760
	21st to end	Night	8% 11% 40% 29% 11% 1	858
November	1st to 10th	Night	6% 17% 40% 26% 9%	973
	11th to 20th	Night	7% 20% 43% 21% 8% 1	950
	21st to end	Night	6% 17% 41% 27% 7% 1	950
December	1st to 10th	Night	7% 22% 39% 27% 5%	950
	11th to 20th	Night	6% 20% 45% 21% 6% 1	950
	21st to end	Night	9% 22% 43% 21% 4 1	1045

Page generated at 2024-11-07 04:55:44. Version ac07

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