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 2025-12-03.

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 5% 2 6% 4 4 5% 4 7% 8% 51%	135734
	Night	2 5% 2 5% 3 3 4 3 5% 8% 60%	132438
Transparency	Day	27% 6% 11% 22% 23% 10%	130688
	Night	22% 5% 12% 26% 26% 9%	128488
Seeing	Day	13% 16% 34% 25% 10% 2	16994
	Night	7% 14% 38% 29% 10% 1	27040

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 3 8% 4 2 2 2 4 7% 62%	3638
	11th to 20th	Day	3 3 7% 6% 5% 5% 3 6% 8% 54%	3850
	21st to end	Day	5% 3 7% 4 3 3 3 4 6% 61%	4510
February	1st to 10th	Day	6% 3 7% 4 2 4 3 6% 7% 58%	1800
	11th to 20th	Day	3 2 5% 3 3 4 4 5% 8% 62%	1920
	21st to end	Day	6% 2 6% 4 4 4 3 5% 7% 60%	1650
March	1st to 10th	Day	1 6% 3 6% 3 3 3 3 5% 7% 61%	4500
	11th to 20th	Day	2 9% 5% 8% 5% 5% 4 4 6% 8% 45%	4995
	21st to end	Day	1 7% 2 5% 3 4 4 4 6% 9% 55%	5788
April	1st to 10th	Day	3 8% 2 5% 5% 4 5% 4 7% 8% 50%	2400
	11th to 20th	Day	6% 10% 3 7% 4 5% 5% 3 5% 8% 44%	2371
	21st to end	Day	6% 10% 3 6% 5% 5% 5% 4 6% 8% 43%	2400
May	1st to 10th	Day	7% 10% 3 7% 5% 4 4 3 6% 8% 42%	5657
	11th to 20th	Day	6% 7% 2 6% 4 5% 5% 5% 7% 9% 45%	6288
	21st to end	Day	4 5% 2 6% 3 4 6% 6% 8% 9% 48%	6925
June	1st to 10th	Day	5% 5% 2 5% 4 4 5% 5% 8% 10% 46%	2800
	11th to 20th	Day	5% 4 2 4 3 5% 5% 5% 6% 9% 52%	2800
	21st to end	Day	3 4 2 6% 5% 5% 6% 6% 7% 9% 46%	2800
July	1st to 10th	Day	3 4 1 5% 4 5% 6% 5% 8% 8% 51%	6339
	11th to 20th	Day	4 4 2 6% 6% 7% 8% 7% 10% 10% 37%	6340
	21st to end	Day	6% 5% 3 7% 6% 6% 7% 5% 8% 8% 41%	6658
August	1st to 10th	Day	5% 4 2 7% 6% 5% 7% 7% 10% 11% 36%	5779
	11th to 20th	Day	3 3 1 5% 5% 6% 7% 6% 9% 11% 45%	5369
	21st to end	Day	5% 5% 3 7% 5% 6% 7% 6% 8% 9% 40%	5984
September	1st to 10th	Day	6% 5% 2 6% 5% 5% 4 4 6% 6% 51%	2400
	11th to 20th	Day	5% 4 2 4 4 4 4 4 5% 7% 56%	2390
	21st to end	Day	5% 4 2 4 3 3 4 3 5% 6% 61%	2198
October	1st to 10th	Day	3 4 1 4 3 3 3 3 4 4 68%	3270
	11th to 20th	Day	4 4 2 5% 3 3 4 4 7% 8% 57%	3250
	21st to end	Day	2 5% 2 4 2 2 3 2 4 6% 69%	3467
November	1st to 10th	Day	1 5% 1 4 2 2 2 3 5% 6% 68%	1853
	11th to 20th	Day	1 3 2 5% 3 3 3 2 5% 7% 66%	1890
	21st to end	Day	1 6% 2 5% 3 3 4 3 5% 7% 61%	1789
December	1st to 10th	Day	3 3 6% 2 2 3 2 3 6% 69%	2636
	11th to 20th	Day	1 3 1 4 2 2 3 2 5% 8% 69%	3026
	21st to end	Day	5% 2 7% 3 4 4 3 6% 8% 57%	4004
January	1st to 10th	Night	4 3 10% 4 3 3 2 4 7% 59%	6327
	11th to 20th	Night	2 1 4 4 4 4 4 5% 6% 65%	6174
	21st to end	Night	1 6% 2 6% 3 3 3 2 4 6% 64%	6468
February	1st to 10th	Night	5% 2 6% 3 3 3 2 4 8% 63%	2600
	11th to 20th	Night	1 4 3 7% 3 3 3 3 5% 7% 62%	2365
	21st to end	Night	1 5% 2 5% 3 4 3 3 5% 6% 64%	1980
March	1st to 10th	Night	1 7% 2 6% 3 3 3 3 5% 6% 61%	5374
	11th to 20th	Night	2 11% 4 5% 3 3 3 3 4 7% 56%	5000
	21st to end	Night	2 7% 3 5% 3 2 3 4 5% 8% 58%	5173
April	1st to 10th	Night	2 7% 2 6% 3 3 3 3 6% 7% 60%	2000
	11th to 20th	Night	5% 10% 3 4 3 3 4 3 5% 6% 54%	1977
	21st to end	Night	6% 11% 2 5% 3 3 4 2 4 7% 52%	2000
May	1st to 10th	Night	8% 10% 3 5% 3 3 4 4 6% 8% 45%	4320
	11th to 20th	Night	6% 5% 2 5% 3 3 4 3 6% 8% 53%	3624
	21st to end	Night	4 5% 2 4 3 3 3 3 5% 7% 62%	3972
June	1st to 10th	Night	4 5% 2 3 2 3 4 3 6% 10% 58%	1600
	11th to 20th	Night	3 3 1 3 3 3 3 4 6% 9% 63%	1600
	21st to end	Night	3 3 1 5% 3 4 5% 5% 8% 8% 56%	1600
July	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 9% 59%	3640
	11th to 20th	Night	2 3 1 3 4 4 5% 4 8% 12% 54%	3640
	21st to end	Night	3 3 1 5% 4 5% 6% 5% 8% 10% 50%	4197
August	1st to 10th	Night	3 3 1 4 3 4 6% 5% 9% 11% 51%	4033
	11th to 20th	Night	4 3 1 4 3 3 5% 4 9% 12% 53%	4478
	21st to end	Night	5% 5% 2 7% 4 5% 5% 5% 8% 9% 44%	4993
September	1st to 10th	Night	5% 3 2 4 3 4 5% 4 5% 9% 55%	2000
	11th to 20th	Night	6% 3 1 4 3 3 3 4 5% 7% 60%	2010
	21st to end	Night	5% 4 2 5% 3 2 3 3 5% 7% 61%	2200
October	1st to 10th	Night	3 3 1 2 2 2 3 3 4 6% 72%	3918
	11th to 20th	Night	3 5% 1 3 2 3 3 3 5% 7% 65%	3898
	21st to end	Night	2 4 1 3 2 2 2 3 4 6% 70%	4299
November	1st to 10th	Night	1 3 2 3 3 2 3 2 5% 7% 69%	2665
	11th to 20th	Night	4 2 4 3 3 3 3 4 6% 70%	2730
	21st to end	Night	1 7% 2 4 2 3 3 3 5% 7% 63%	2829
December	1st to 10th	Night	2 1 3 2 1 2 2 3 7% 75%	4599
	11th to 20th	Night	3 2 4 3 2 2 3 5% 7% 70%	5181
	21st to end	Night	1 7% 3 7% 4 3 4 3 5% 7% 55%	6974

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	22% 3 11% 28% 26% 9%	3639
	11th to 20th	Day	23% 5% 14% 21% 28% 9%	3850
	21st to end	Day	23% 4 10% 26% 25% 12%	4510
February	1st to 10th	Day	24% 4 14% 28% 21% 10%	1800
	11th to 20th	Day	19% 4 12% 28% 29% 7%	1930
	21st to end	Day	22% 5% 11% 21% 27% 15%	1650
March	1st to 10th	Day	21% 3 8% 18% 32% 18%	4500
	11th to 20th	Day	34% 7% 9% 22% 23% 6%	4995
	21st to end	Day	22% 5% 11% 40% 18% 3	5788
April	1st to 10th	Day	28% 7% 13% 24% 20% 9%	2400
	11th to 20th	Day	37% 6% 12% 19% 20% 8%	2374
	21st to end	Day	36% 7% 11% 24% 19% 3	2400
May	1st to 10th	Day	35% 6% 12% 22% 19% 6%	5657
	11th to 20th	Day	30% 9% 11% 19% 20% 10%	6292
	21st to end	Day	25% 8% 14% 18% 25% 9%	6926
June	1st to 10th	Day	28% 10% 15% 19% 19% 8%	2800
	11th to 20th	Day	26% 8% 10% 16% 21% 18%	2800
	21st to end	Day	30% 9% 11% 19% 20% 12%	2800
July	1st to 10th	Day	23% 7% 10% 16% 22% 21%	6271
	11th to 20th	Day	32% 11% 16% 22% 14% 6%	6265
	21st to end	Day	36% 9% 14% 14% 15% 12%	6466
August	1st to 10th	Day	40% 10% 16% 16% 13% 4	4208
	11th to 20th	Day	30% 10% 15% 14% 18% 12%	3885
	21st to end	Day	32% 8% 14% 16% 21% 9%	4311
September	1st to 10th	Day	31% 6% 10% 18% 23% 12%	2400
	11th to 20th	Day	26% 6% 9% 18% 28% 12%	2390
	21st to end	Day	23% 5% 7% 21% 34% 10%	2198
October	1st to 10th	Day	19% 4 7% 15% 31% 23%	3270
	11th to 20th	Day	22% 5% 9% 26% 29% 9%	3250
	21st to end	Day	16% 3 6% 20% 44% 11%	3467
November	1st to 10th	Day	16% 4 11% 21% 35% 13%	1853
	11th to 20th	Day	17% 4 7% 33% 30% 10%	1890
	21st to end	Day	22% 3 9% 27% 28% 11%	1789
December	1st to 10th	Day	17% 4 9% 34% 27% 9%	2636
	11th to 20th	Day	15% 3 11% 34% 29% 7%	3024
	21st to end	Day	23% 4 10% 26% 28% 10%	4004
January	1st to 10th	Night	24% 3 10% 28% 28% 7%	6327
	11th to 20th	Night	18% 3 11% 27% 25% 16%	6174
	21st to end	Night	21% 4 11% 24% 28% 12%	6468
February	1st to 10th	Night	21% 3 13% 31% 23% 9%	2600
	11th to 20th	Night	22% 4 11% 30% 25% 8%	2365
	21st to end	Night	20% 4 8% 26% 28% 13%	1980
March	1st to 10th	Night	21% 3 9% 17% 36% 12%	5374
	11th to 20th	Night	28% 5% 8% 19% 29% 11%	5000
	21st to end	Night	24% 5% 14% 38% 17% 2	5173
April	1st to 10th	Night	23% 4 12% 29% 24% 7%	2000
	11th to 20th	Night	30% 6% 11% 27% 20% 6%	1977
	21st to end	Night	32% 6% 12% 28% 19% 3	2000
May	1st to 10th	Night	34% 7% 13% 27% 12% 7%	4317
	11th to 20th	Night	26% 8% 13% 26% 19% 7%	3625
	21st to end	Night	21% 6% 18% 25% 25% 5%	3972
June	1st to 10th	Night	22% 7% 22% 26% 15% 9%	1600
	11th to 20th	Night	17% 8% 12% 22% 24% 17%	1600
	21st to end	Night	23% 7% 14% 22% 23% 11%	1600
July	1st to 10th	Night	21% 7% 12% 19% 30% 12%	3600
	11th to 20th	Night	20% 9% 23% 30% 15% 4	3592
	21st to end	Night	25% 8% 22% 22% 13% 10%	4077
August	1st to 10th	Night	30% 11% 24% 19% 12% 3	2928
	11th to 20th	Night	23% 9% 23% 20% 19% 6%	3238
	21st to end	Night	26% 10% 20% 21% 20% 3	3597
September	1st to 10th	Night	25% 7% 12% 24% 22% 9%	2000
	11th to 20th	Night	22% 7% 13% 22% 23% 13%	2010
	21st to end	Night	23% 5% 10% 24% 30% 8%	2200
October	1st to 10th	Night	14% 5% 8% 25% 34% 14%	3918
	11th to 20th	Night	18% 5% 10% 33% 25% 8%	3898
	21st to end	Night	15% 3 7% 28% 37% 11%	4299
November	1st to 10th	Night	15% 4 10% 25% 33% 13%	2665
	11th to 20th	Night	16% 4 8% 31% 30% 11%	2730
	21st to end	Night	20% 4 9% 27% 29% 11%	2829
December	1st to 10th	Night	12% 3 9% 37% 32% 7%	4599
	11th to 20th	Night	15% 3 9% 30% 35% 7%	5182
	21st to end	Night	27% 4 10% 22% 29% 8%	6974

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	14% 19% 34% 22% 9% 1	300
	11th to 20th	Day	11% 25% 41% 20% 3	300
	21st to end	Day	6% 18% 46% 22% 6% 2	330
February	1st to 10th	Day	12% 34% 37% 14% 2 1	300
	11th to 20th	Day	9% 33% 41% 16% 1	300
	21st to end	Day	14% 24% 42% 20% 1	249
March	1st to 10th	Day	13% 21% 40% 20% 5% 1	300
	11th to 20th	Day	19% 23% 33% 20% 5%	495
	21st to end	Day	19% 25% 35% 16% 5%	550
April	1st to 10th	Day	17% 27% 32% 18% 4 1	500
	11th to 20th	Day	24% 29% 29% 14% 3 1	492
	21st to end	Day	22% 22% 34% 15% 6% 1	500
May	1st to 10th	Day	19% 21% 36% 18% 6% 1	590
	11th to 20th	Day	18% 14% 33% 25% 9% 2	725
	21st to end	Day	13% 17% 32% 24% 13% 2	789
June	1st to 10th	Day	9% 12% 34% 29% 14% 2	730
	11th to 20th	Day	10% 15% 32% 30% 11% 2	730
	21st to end	Day	8% 12% 35% 30% 13% 2	730
July	1st to 10th	Day	7% 5% 27% 40% 17% 4	721
	11th to 20th	Day	7% 5% 24% 37% 22% 5%	718
	21st to end	Day	11% 4 21% 38% 21% 4	689
August	1st to 10th	Day	11% 7% 33% 30% 16% 4	527
	11th to 20th	Day	7% 6% 33% 36% 14% 3	517
	21st to end	Day	11% 8% 32% 34% 13% 2	583
September	1st to 10th	Day	11% 11% 32% 31% 13% 2	530
	11th to 20th	Day	8% 14% 37% 29% 11% 1	520
	21st to end	Day	8% 15% 29% 29% 15% 4	330
October	1st to 10th	Day	11% 18% 30% 22% 15% 3	330
	11th to 20th	Day	12% 26% 31% 22% 7% 2	330
	21st to end	Day	12% 18% 41% 22% 6% 1	363
November	1st to 10th	Day	16% 19% 37% 17% 10% 1	330
	11th to 20th	Day	12% 21% 40% 22% 5% 1	330
	21st to end	Day	11% 20% 41% 22% 6% 1	330
December	1st to 10th	Day	14% 17% 41% 21% 6% 1	306
	11th to 20th	Day	10% 23% 44% 17% 5%	300
	21st to end	Day	14% 26% 36% 17% 5% 2	330
January	1st to 10th	Night	5% 22% 39% 27% 6% 2	1000
	11th to 20th	Night	6% 23% 44% 20% 5% 1	925
	21st to end	Night	4 15% 51% 26% 5%	880
February	1st to 10th	Night	6% 23% 50% 19% 3	800
	11th to 20th	Night	5% 21% 50% 21% 4	784
	21st to end	Night	6% 22% 47% 22% 2	660
March	1st to 10th	Night	7% 21% 43% 23% 4 1	800
	11th to 20th	Night	8% 15% 44% 25% 8%	800
	21st to end	Night	8% 17% 47% 24% 4	745
April	1st to 10th	Night	9% 19% 44% 24% 4	600
	11th to 20th	Night	13% 18% 39% 24% 5% 1	593
	21st to end	Night	13% 16% 37% 26% 7% 1	600
May	1st to 10th	Night	13% 10% 34% 32% 10% 1	600
	11th to 20th	Night	15% 7% 30% 36% 12% 1	591
	21st to end	Night	9% 12% 30% 34% 13% 2	650
June	1st to 10th	Night	8% 7% 26% 42% 16% 2	600
	11th to 20th	Night	7% 7% 38% 35% 13% 2	600
	21st to end	Night	5% 3 29% 44% 18% 2	600
July	1st to 10th	Night	8% 2 20% 45% 23% 3	585
	11th to 20th	Night	3 4 18% 41% 31% 4	582
	21st to end	Night	6% 1 18% 43% 30% 2	657
August	1st to 10th	Night	7% 3 21% 41% 25% 3	597
	11th to 20th	Night	7% 2 21% 46% 21% 3	594
	21st to end	Night	7% 3 22% 44% 21% 2	660
September	1st to 10th	Night	7% 3 24% 43% 21% 4	600
	11th to 20th	Night	8% 4 31% 39% 16% 2	600
	21st to end	Night	9% 8% 32% 35% 15% 2	600
October	1st to 10th	Night	7% 10% 42% 29% 10% 3	798
	11th to 20th	Night	4 14% 40% 32% 8% 2	800
	21st to end	Night	8% 11% 42% 28% 10% 1	903
November	1st to 10th	Night	6% 18% 42% 25% 9%	1025
	11th to 20th	Night	6% 20% 45% 20% 7% 1	1050
	21st to end	Night	6% 17% 43% 26% 7% 1	1050
December	1st to 10th	Night	7% 21% 40% 28% 5%	1011
	11th to 20th	Night	6% 22% 45% 20% 6% 1	1000
	21st to end	Night	8% 22% 44% 21% 4 1	1100

Page generated at 2025-11-29 23:00:54. Version ac07

Copyright © 2025 Attilla Danko.