Saleratus Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saleratus Ranch clear sky chart from 2005-11-06 to 2026-10-14.

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 5% 4 4 5% 4 6% 7% 56%	157362
	Night	3 5% 2 5% 3 3 4 3 5% 7% 59%	151987
Transparency	Day	23% 7% 10% 20% 25% 15%	152206
	Night	22% 5% 9% 21% 27% 16%	148150
Seeing	Day	11% 19% 29% 25% 13% 3	17412
	Night	7% 11% 23% 31% 23% 5%	27805

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	2 6% 3 8% 4 4 4 4 5% 7% 53%	5318
	11th to 20th	Day	2 3 1 3 3 3 3 2 4 5% 71%	5340
	21st to end	Day	3 9% 3 6% 4 3 3 2 4 4 59%	5844
February	1st to 10th	Day	2 9% 4 6% 3 4 3 2 5% 7% 54%	1890
	11th to 20th	Day	5% 8% 3 7% 5% 3 4 4 5% 6% 49%	1845
	21st to end	Day	3 10% 2 7% 4 5% 4 3 4 5% 53%	1812
March	1st to 10th	Day	3 10% 3 6% 4 4 4 3 4 6% 54%	5064
	11th to 20th	Day	4 13% 3 8% 6% 6% 5% 4 5% 6% 41%	5110
	21st to end	Day	3 9% 3 9% 6% 5% 5% 4 6% 7% 43%	5607
April	1st to 10th	Day	4 6% 2 6% 4 4 4 4 5% 6% 55%	2419
	11th to 20th	Day	2 6% 2 6% 4 4 4 4 7% 7% 52%	2491
	21st to end	Day	4 5% 2 5% 4 4 5% 4 7% 8% 53%	2621
May	1st to 10th	Day	4 4 1 5% 4 4 5% 4 5% 7% 56%	7626
	11th to 20th	Day	3 4 2 5% 4 4 5% 4 6% 7% 56%	7596
	21st to end	Day	3 3 2 5% 4 4 5% 4 6% 7% 59%	8370
June	1st to 10th	Day	4 3 1 3 3 3 4 4 6% 7% 62%	2819
	11th to 20th	Day	3 2 1 3 2 3 3 3 3 6% 71%	2929
	21st to end	Day	2 3 1 3 4 3 3 3 5% 6% 66%	2730
July	1st to 10th	Day	2 2 1 2 2 3 3 3 4 6% 72%	7649
	11th to 20th	Day	2 3 1 4 4 6% 8% 7% 9% 11% 45%	7650
	21st to end	Day	3 3 1 4 4 5% 6% 5% 8% 10% 51%	8304
August	1st to 10th	Day	3 2 1 4 4 5% 6% 6% 8% 8% 52%	7549
	11th to 20th	Day	3 3 2 5% 5% 6% 6% 6% 8% 8% 50%	7565
	21st to end	Day	5% 5% 2 6% 5% 6% 7% 6% 9% 10% 38%	7829
September	1st to 10th	Day	5% 4 2 5% 4 4 4 5% 6% 7% 54%	2520
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 6% 57%	2321
	21st to end	Day	6% 4 1 4 3 3 3 3 4 5% 64%	2310
October	1st to 10th	Day	5% 3 1 3 2 2 2 3 4 5% 69%	3376
	11th to 20th	Day	9% 5% 2 4 3 3 3 3 5% 7% 57%	3280
	21st to end	Day	3 3 1 4 3 3 3 2 3 5% 69%	3548
November	1st to 10th	Day	3 5% 2 3 3 2 2 3 5% 7% 66%	2059
	11th to 20th	Day	3 5% 1 4 3 3 3 2 4 6% 68%	1942
	21st to end	Day	5% 5% 2 5% 3 2 4 2 5% 6% 63%	1684
December	1st to 10th	Day	3 4 2 3 2 2 3 3 6% 7% 65%	2700
	11th to 20th	Day	4 5% 2 5% 3 4 4 4 6% 9% 55%	3106
	21st to end	Day	3 8% 4 7% 4 4 4 3 5% 6% 53%	4539
January	1st to 10th	Night	3 7% 3 8% 5% 5% 5% 3 5% 5% 51%	7605
	11th to 20th	Night	1 3 1 3 3 2 2 2 3 5% 73%	7650
	21st to end	Night	2 7% 3 7% 3 3 3 3 4 6% 57%	8370
February	1st to 10th	Night	3 7% 3 4 3 3 4 3 6% 6% 58%	2730
	11th to 20th	Night	4 8% 3 6% 3 4 4 3 5% 6% 56%	2662
	21st to end	Night	4 7% 3 3 4 5% 4 3 5% 7% 56%	1988
March	1st to 10th	Night	2 9% 2 5% 3 4 4 4 5% 7% 56%	5050
	11th to 20th	Night	5% 11% 3 7% 4 5% 4 4 6% 7% 45%	5110
	21st to end	Night	3 6% 2 6% 5% 4 5% 5% 7% 8% 49%	5610
April	1st to 10th	Night	3 6% 2 6% 4 4 5% 4 5% 7% 55%	2200
	11th to 20th	Night	3 5% 2 5% 3 3 5% 5% 5% 7% 57%	2077
	21st to end	Night	4 4 1 4 3 4 4 3 6% 7% 60%	1995
May	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 7% 62%	5321
	11th to 20th	Night	3 4 2 5% 3 3 4 3 5% 7% 61%	5296
	21st to end	Night	3 3 1 3 2 3 3 2 4 7% 69%	5837
June	1st to 10th	Night	3 3 1 3 3 3 3 3 4 7% 68%	1785
	11th to 20th	Night	3 2 1 3 3 2 3 2 3 6% 71%	1680
	21st to end	Night	3 2 1 3 3 3 3 3 4 6% 68%	1884
July	1st to 10th	Night	1 2 1 3 3 3 3 3 4 4 73%	5340
	11th to 20th	Night	3 4 2 6% 5% 5% 6% 5% 8% 10% 46%	5340
	21st to end	Night	3 4 2 5% 4 4 5% 4 8% 11% 49%	5805
August	1st to 10th	Night	2 3 2 5% 4 5% 6% 5% 8% 8% 53%	5273
	11th to 20th	Night	2 2 1 4 3 4 5% 4 8% 9% 57%	5291
	21st to end	Night	5% 5% 2 6% 5% 5% 6% 5% 9% 10% 42%	6387
September	1st to 10th	Night	5% 5% 2 4 3 3 4 4 5% 7% 60%	2100
	11th to 20th	Night	5% 4 2 4 3 2 4 3 4 6% 63%	2294
	21st to end	Night	6% 4 2 4 2 2 2 2 3 4 69%	2310
October	1st to 10th	Night	5% 2 1 2 2 2 2 2 3 5% 75%	4032
	11th to 20th	Night	8% 5% 3 6% 4 4 4 3 4 5% 55%	3934
	21st to end	Night	4 4 2 4 2 2 2 2 4 6% 68%	4252
November	1st to 10th	Night	4 4 2 4 2 3 3 2 5% 6% 66%	2460
	11th to 20th	Night	2 4 2 3 3 3 3 3 4 6% 68%	2672
	21st to end	Night	4 5% 2 4 3 4 3 3 4 6% 62%	2910
December	1st to 10th	Night	3 5% 1 3 2 2 2 3 5% 7% 68%	4710
	11th to 20th	Night	3 5% 2 5% 3 3 3 3 5% 8% 58%	5321
	21st to end	Night	4 8% 2 5% 3 3 3 3 5% 7% 58%	6706

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	27% 8% 15% 29% 18% 4	5321
	11th to 20th	Day	16% 3 10% 25% 28% 18%	5340
	21st to end	Day	26% 4 7% 22% 32% 8%	5844
February	1st to 10th	Day	29% 6% 15% 19% 23% 8%	1890
	11th to 20th	Day	33% 5% 9% 22% 24% 6%	1854
	21st to end	Day	32% 5% 6% 20% 28% 8%	1812
March	1st to 10th	Day	27% 5% 8% 20% 31% 9%	5064
	11th to 20th	Day	36% 8% 10% 22% 17% 6%	5110
	21st to end	Day	33% 10% 10% 26% 19% 3	5607
April	1st to 10th	Day	27% 5% 6% 22% 28% 12%	2419
	11th to 20th	Day	25% 7% 8% 22% 29% 10%	2494
	21st to end	Day	24% 6% 7% 23% 32% 8%	2621
May	1st to 10th	Day	21% 8% 9% 20% 32% 12%	7626
	11th to 20th	Day	20% 7% 9% 20% 34% 11%	7599
	21st to end	Day	17% 7% 8% 18% 39% 11%	8371
June	1st to 10th	Day	18% 5% 5% 17% 31% 24%	2819
	11th to 20th	Day	15% 4 4 9% 27% 41%	2929
	21st to end	Day	17% 5% 4 10% 25% 39%	2730
July	1st to 10th	Day	13% 3 6% 7% 17% 55%	7586
	11th to 20th	Day	25% 10% 16% 17% 17% 15%	7581
	21st to end	Day	21% 9% 16% 20% 16% 17%	8120
August	1st to 10th	Day	26% 10% 16% 11% 18% 18%	5978
	11th to 20th	Day	29% 10% 14% 19% 16% 12%	5964
	21st to end	Day	30% 9% 15% 22% 14% 9%	6144
September	1st to 10th	Day	26% 7% 8% 16% 23% 21%	2520
	11th to 20th	Day	24% 7% 8% 15% 23% 23%	2321
	21st to end	Day	22% 4 6% 13% 35% 20%	2310
October	1st to 10th	Day	16% 3 6% 14% 32% 28%	3376
	11th to 20th	Day	25% 4 5% 25% 29% 11%	3280
	21st to end	Day	16% 4 9% 25% 39% 7%	3548
November	1st to 10th	Day	18% 4 7% 27% 34% 9%	2059
	11th to 20th	Day	19% 4 6% 30% 35% 5%	1942
	21st to end	Day	23% 5% 8% 26% 27% 12%	1684
December	1st to 10th	Day	18% 4 8% 30% 30% 10%	2700
	11th to 20th	Day	25% 6% 11% 29% 25% 4	3104
	21st to end	Day	31% 7% 11% 21% 18% 12%	4539
January	1st to 10th	Night	32% 6% 12% 28% 16% 6%	7605
	11th to 20th	Night	15% 3 10% 26% 30% 16%	7650
	21st to end	Night	26% 5% 7% 21% 29% 13%	8370
February	1st to 10th	Night	25% 5% 13% 25% 22% 10%	2730
	11th to 20th	Night	29% 5% 10% 23% 26% 8%	2663
	21st to end	Night	26% 6% 8% 22% 29% 9%	1988
March	1st to 10th	Night	24% 6% 7% 20% 28% 16%	5050
	11th to 20th	Night	34% 7% 9% 22% 23% 7%	5110
	21st to end	Night	25% 9% 11% 30% 23% 2	5610
April	1st to 10th	Night	26% 5% 7% 20% 28% 13%	2200
	11th to 20th	Night	24% 6% 6% 20% 30% 13%	2077
	21st to end	Night	20% 6% 6% 24% 34% 9%	1995
May	1st to 10th	Night	20% 5% 7% 19% 38% 11%	5319
	11th to 20th	Night	19% 5% 6% 19% 36% 15%	5297
	21st to end	Night	13% 4 6% 18% 45% 13%	5838
June	1st to 10th	Night	16% 3 5% 16% 35% 25%	1785
	11th to 20th	Night	16% 3 6% 10% 22% 44%	1680
	21st to end	Night	15% 4 4 12% 23% 43%	1884
July	1st to 10th	Night	14% 3 5% 6% 14% 58%	5295
	11th to 20th	Night	26% 7% 14% 15% 17% 21%	5286
	21st to end	Night	25% 6% 16% 19% 15% 19%	5677
August	1st to 10th	Night	28% 8% 12% 9% 16% 26%	4168
	11th to 20th	Night	23% 8% 15% 23% 16% 14%	4168
	21st to end	Night	26% 8% 14% 22% 16% 15%	5003
September	1st to 10th	Night	22% 5% 8% 16% 23% 26%	2100
	11th to 20th	Night	21% 5% 7% 17% 25% 25%	2294
	21st to end	Night	20% 3 4 14% 34% 24%	2310
October	1st to 10th	Night	14% 2 5% 13% 31% 36%	4032
	11th to 20th	Night	28% 5% 6% 17% 31% 13%	3934
	21st to end	Night	18% 3 6% 19% 44% 10%	4252
November	1st to 10th	Night	19% 4 7% 22% 35% 13%	2460
	11th to 20th	Night	16% 4 6% 25% 39% 9%	2672
	21st to end	Night	23% 5% 7% 21% 30% 14%	2910
December	1st to 10th	Night	16% 4 6% 28% 33% 12%	4710
	11th to 20th	Night	23% 5% 8% 30% 28% 5%	5322
	21st to end	Night	26% 6% 12% 24% 22% 12%	6706

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	16% 20% 35% 18% 8% 2	330
	11th to 20th	Day	14% 23% 30% 22% 10% 1	330
	21st to end	Day	9% 25% 32% 23% 10% 1	363
February	1st to 10th	Day	16% 26% 31% 21% 6% 1	330
	11th to 20th	Day	18% 30% 30% 14% 8%	330
	21st to end	Day	17% 30% 34% 15% 4	426
March	1st to 10th	Day	16% 26% 32% 18% 7%	540
	11th to 20th	Day	17% 24% 33% 17% 8% 1	540
	21st to end	Day	15% 33% 33% 13% 4 1	594
April	1st to 10th	Day	14% 29% 31% 15% 7% 3	540
	11th to 20th	Day	17% 31% 34% 12% 4 2	532
	21st to end	Day	15% 30% 31% 16% 7% 1	540
May	1st to 10th	Day	11% 26% 40% 17% 5% 1	543
	11th to 20th	Day	11% 20% 35% 21% 11% 2	568
	21st to end	Day	12% 24% 31% 22% 9% 3	617
June	1st to 10th	Day	7% 12% 30% 32% 18% 2	659
	11th to 20th	Day	5% 16% 33% 28% 13% 4	769
	21st to end	Day	7% 15% 37% 30% 8% 2	570
July	1st to 10th	Day	4 8% 30% 36% 19% 3	566
	11th to 20th	Day	4 2 20% 34% 32% 7%	564
	21st to end	Day	6% 6% 15% 40% 24% 8%	619
August	1st to 10th	Day	6% 6% 24% 38% 22% 4	567
	11th to 20th	Day	5% 7% 24% 37% 21% 7%	557
	21st to end	Day	6% 5% 22% 34% 26% 6%	627
September	1st to 10th	Day	6% 8% 26% 33% 20% 8%	570
	11th to 20th	Day	10% 14% 31% 27% 13% 5%	570
	21st to end	Day	9% 16% 27% 31% 12% 5%	570
October	1st to 10th	Day	12% 17% 25% 21% 14% 11%	366
	11th to 20th	Day	14% 20% 24% 21% 16% 5%	339
	21st to end	Day	10% 22% 26% 26% 15% 2	363
November	1st to 10th	Day	12% 24% 27% 21% 15% 2	330
	11th to 20th	Day	11% 21% 31% 22% 12% 4	330
	21st to end	Day	9% 23% 30% 21% 12% 4	330
December	1st to 10th	Day	11% 20% 30% 23% 14% 2	330
	11th to 20th	Day	8% 20% 32% 25% 13% 2	330
	21st to end	Day	19% 23% 27% 22% 8% 1	363
January	1st to 10th	Night	9% 13% 27% 30% 18% 4	840
	11th to 20th	Night	8% 13% 28% 29% 19% 3	840
	21st to end	Night	9% 13% 27% 31% 16% 4	924
February	1st to 10th	Night	7% 16% 27% 32% 14% 3	840
	11th to 20th	Night	8% 14% 33% 28% 14% 2	824
	21st to end	Night	10% 18% 29% 33% 8% 2	692
March	1st to 10th	Night	7% 17% 30% 30% 14% 2	840
	11th to 20th	Night	9% 12% 28% 28% 21% 3	840
	21st to end	Night	9% 18% 28% 31% 12% 2	924
April	1st to 10th	Night	6% 21% 29% 29% 14% 1	730
	11th to 20th	Night	7% 23% 27% 30% 11% 2	623
	21st to end	Night	7% 21% 27% 26% 16% 3	630
May	1st to 10th	Night	7% 14% 31% 31% 15% 2	630
	11th to 20th	Night	6% 10% 24% 34% 22% 4	621
	21st to end	Night	6% 14% 26% 29% 22% 4	683
June	1st to 10th	Night	4 7% 19% 38% 29% 2	630
	11th to 20th	Night	4 9% 26% 35% 23% 4	630
	21st to end	Night	3 6% 20% 37% 30% 4	630
July	1st to 10th	Night	4 3 13% 35% 36% 9%	615
	11th to 20th	Night	5% 2 11% 31% 43% 8%	612
	21st to end	Night	5% 3 8% 30% 43% 11%	690
August	1st to 10th	Night	6% 2 10% 33% 41% 8%	627
	11th to 20th	Night	4 2 10% 38% 38% 8%	624
	21st to end	Night	6% 3 10% 30% 41% 10%	693
September	1st to 10th	Night	6% 3 13% 36% 37% 6%	630
	11th to 20th	Night	6% 6% 16% 32% 32% 8%	824
	21st to end	Night	8% 9% 15% 28% 32% 9%	840
October	1st to 10th	Night	8% 7% 23% 32% 25% 6%	840
	11th to 20th	Night	8% 9% 22% 33% 22% 7%	812
	21st to end	Night	9% 11% 22% 28% 24% 6%	880
November	1st to 10th	Night	8% 10% 23% 31% 23% 5%	820
	11th to 20th	Night	4 12% 26% 32% 20% 5%	840
	21st to end	Night	8% 15% 23% 30% 19% 5%	1020
December	1st to 10th	Night	9% 10% 26% 36% 16% 3	1050
	11th to 20th	Night	11% 11% 29% 29% 18% 2	1050
	21st to end	Night	11% 15% 26% 33% 13% 2	967

Page generated at 2026-10-11 03:06:30. Version ac07

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