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 2024-11-02.

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 6% 2 5% 4 4 5% 4 6% 7% 54%	100851
	Night	4 6% 2 5% 4 4 4 4 5% 7% 57%	98337
Transparency	Day	26% 7% 9% 19% 24% 15%	100616
	Night	25% 6% 9% 21% 25% 15%	98161
Seeing	Day	10% 18% 29% 26% 14% 4	14810
	Night	7% 11% 22% 31% 24% 5%	25221

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 7% 3 6% 3 3 4 4 6% 7% 55%	2858
	11th to 20th	Day	3 5% 1 5% 4 4 5% 4 5% 6% 57%	2860
	21st to end	Day	5% 13% 4 6% 3 3 3 2 4 5% 53%	3146
February	1st to 10th	Day	3 10% 4 6% 3 3 3 2 6% 7% 53%	1710
	11th to 20th	Day	5% 8% 3 7% 5% 3 4 3 5% 6% 51%	1665
	21st to end	Day	3 11% 3 7% 4 5% 4 3 4 5% 50%	1643
March	1st to 10th	Day	3 9% 2 5% 4 5% 4 4 5% 6% 51%	3444
	11th to 20th	Day	5% 13% 3 7% 6% 6% 6% 5% 6% 7% 38%	3490
	21st to end	Day	4 11% 3 10% 7% 5% 5% 4 6% 7% 39%	3825
April	1st to 10th	Day	5% 6% 2 6% 4 4 4 4 5% 6% 55%	2189
	11th to 20th	Day	2 6% 2 6% 4 5% 4 4 7% 7% 52%	2251
	21st to end	Day	4 6% 2 4 4 4 5% 4 6% 8% 53%	2371
May	1st to 10th	Day	4 4 2 5% 4 4 5% 4 5% 6% 56%	4110
	11th to 20th	Day	3 4 2 5% 4 4 5% 5% 7% 8% 54%	4071
	21st to end	Day	3 4 2 5% 4 3 4 4 5% 7% 60%	4477
June	1st to 10th	Day	3 3 1 3 3 3 4 3 5% 7% 64%	2551
	11th to 20th	Day	3 2 1 3 2 3 3 3 3 6% 70%	2651
	21st to end	Day	2 3 1 4 4 4 3 3 5% 7% 65%	2470
July	1st to 10th	Day	3 2 1 3 3 3 4 3 5% 6% 68%	4110
	11th to 20th	Day	2 3 1 5% 5% 7% 9% 8% 10% 11% 39%	4110
	21st to end	Day	4 3 2 5% 5% 5% 6% 6% 7% 9% 49%	4454
August	1st to 10th	Day	5% 4 2 7% 6% 7% 8% 7% 11% 11% 33%	4092
	11th to 20th	Day	4 4 2 5% 5% 6% 6% 6% 8% 8% 47%	4028
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 9% 46%	4221
September	1st to 10th	Day	6% 4 2 5% 4 4 4 5% 6% 7% 54%	2280
	11th to 20th	Day	6% 4 2 5% 3 3 4 4 5% 6% 58%	2100
	21st to end	Day	6% 3 1 3 3 3 3 3 4 5% 67%	2090
October	1st to 10th	Day	8% 5% 2 5% 3 3 3 3 5% 6% 58%	1906
	11th to 20th	Day	5% 4 1 3 2 2 2 2 3 5% 70%	1900
	21st to end	Day	4 3 1 4 3 3 3 2 3 6% 69%	2090
November	1st to 10th	Day	3 5% 2 3 2 2 2 3 5% 6% 66%	1869
	11th to 20th	Day	2 5% 1 4 3 3 3 2 4 6% 69%	1758
	21st to end	Day	4 5% 2 5% 3 2 3 2 4 5% 64%	1524
December	1st to 10th	Day	5% 7% 3 5% 4 3 3 3 5% 5% 56%	1520
	11th to 20th	Day	6% 9% 3 6% 4 4 4 5% 6% 7% 47%	1926
	21st to end	Day	4 10% 4 6% 4 4 4 3 5% 5% 52%	3091
January	1st to 10th	Night	2 6% 3 7% 5% 4 5% 3 5% 5% 54%	4097
	11th to 20th	Night	2 6% 2 6% 4 3 3 3 4 7% 60%	4110
	21st to end	Night	4 9% 3 7% 4 4 3 3 5% 6% 52%	4521
February	1st to 10th	Night	3 8% 3 4 3 3 4 3 6% 6% 57%	2470
	11th to 20th	Night	3 8% 2 5% 3 3 4 3 5% 6% 57%	2402
	21st to end	Night	4 8% 3 4 4 5% 4 3 5% 6% 54%	1805
March	1st to 10th	Night	2 10% 2 5% 3 4 5% 4 5% 7% 53%	3430
	11th to 20th	Night	6% 11% 3 7% 4 5% 5% 4 6% 7% 42%	3490
	21st to end	Night	3 9% 3 7% 6% 5% 6% 5% 7% 7% 43%	3828
April	1st to 10th	Night	3 6% 2 5% 5% 4 5% 4 5% 7% 54%	1990
	11th to 20th	Night	3 5% 2 5% 3 3 5% 4 5% 7% 57%	1877
	21st to end	Night	4 5% 1 3 3 4 5% 3 5% 7% 60%	1805
May	1st to 10th	Night	4 3 1 4 3 3 4 3 7% 8% 61%	2860
	11th to 20th	Night	3 3 2 4 3 3 4 4 7% 9% 57%	2834
	21st to end	Night	4 3 2 3 3 3 3 3 5% 6% 65%	3110
June	1st to 10th	Night	3 3 1 3 3 2 4 2 4 6% 69%	1615
	11th to 20th	Night	4 3 1 3 3 2 3 2 3 6% 69%	1520
	21st to end	Night	3 2 1 4 3 3 4 3 5% 7% 65%	1704
July	1st to 10th	Night	2 3 1 3 3 3 3 3 5% 5% 69%	2860
	11th to 20th	Night	2 3 2 5% 5% 6% 6% 6% 10% 11% 44%	2860
	21st to end	Night	3 5% 2 6% 4 4 6% 4 8% 9% 49%	3109
August	1st to 10th	Night	4 5% 3 7% 6% 7% 8% 7% 11% 9% 34%	2847
	11th to 20th	Night	3 3 2 5% 4 5% 6% 5% 9% 8% 52%	2811
	21st to end	Night	5% 5% 2 5% 4 4 4 4 6% 8% 52%	3446
September	1st to 10th	Night	5% 5% 2 4 3 3 4 4 5% 6% 60%	1900
	11th to 20th	Night	5% 5% 1 4 3 2 3 3 4 6% 65%	2076
	21st to end	Night	5% 3 2 3 2 1 2 2 3 4 72%	2090
October	1st to 10th	Night	8% 4 2 3 3 2 3 2 4 5% 63%	2272
	11th to 20th	Night	4 3 1 3 2 3 3 2 3 5% 72%	2280
	21st to end	Night	4 4 1 2 2 3 3 3 4 6% 68%	2508
November	1st to 10th	Night	4 4 2 4 2 3 3 2 5% 6% 66%	2244
	11th to 20th	Night	1 4 2 3 3 3 3 3 4 6% 69%	2417
	21st to end	Night	4 5% 2 4 3 3 3 3 4 6% 62%	2632
December	1st to 10th	Night	4 8% 2 5% 3 3 3 3 4 6% 59%	2660
	11th to 20th	Night	6% 8% 3 7% 4 4 3 4 6% 8% 49%	3271
	21st to end	Night	5% 10% 3 5% 3 3 4 4 5% 7% 53%	4586

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% 6% 16% 30% 18% 3	2859
	11th to 20th	Day	27% 5% 16% 35% 13% 4	2860
	21st to end	Day	34% 5% 8% 27% 20% 5%	3146
February	1st to 10th	Day	30% 6% 16% 20% 22% 7%	1710
	11th to 20th	Day	33% 4 9% 24% 24% 6%	1674
	21st to end	Day	35% 5% 6% 19% 29% 6%	1643
March	1st to 10th	Day	27% 6% 10% 26% 25% 5%	3444
	11th to 20th	Day	37% 11% 10% 24% 14% 4	3490
	21st to end	Day	37% 10% 9% 22% 20% 3	3825
April	1st to 10th	Day	27% 6% 5% 22% 28% 12%	2189
	11th to 20th	Day	25% 7% 8% 22% 28% 10%	2254
	21st to end	Day	25% 7% 6% 23% 31% 8%	2371
May	1st to 10th	Day	23% 7% 7% 15% 34% 15%	4110
	11th to 20th	Day	20% 9% 8% 18% 32% 13%	4074
	21st to end	Day	17% 8% 7% 13% 39% 16%	4477
June	1st to 10th	Day	17% 5% 5% 17% 31% 25%	2551
	11th to 20th	Day	15% 4 4 10% 27% 40%	2651
	21st to end	Day	18% 5% 4 11% 25% 37%	2470
July	1st to 10th	Day	16% 5% 6% 9% 14% 50%	4046
	11th to 20th	Day	28% 11% 13% 17% 19% 12%	4041
	21st to end	Day	24% 9% 13% 20% 12% 22%	4314
August	1st to 10th	Day	34% 13% 20% 11% 10% 12%	4078
	11th to 20th	Day	29% 8% 12% 14% 19% 16%	4067
	21st to end	Day	29% 7% 11% 20% 20% 13%	4220
September	1st to 10th	Day	27% 7% 7% 13% 23% 23%	2280
	11th to 20th	Day	24% 7% 8% 14% 23% 24%	2100
	21st to end	Day	19% 4 5% 13% 37% 21%	2090
October	1st to 10th	Day	25% 5% 8% 18% 28% 16%	1906
	11th to 20th	Day	17% 3 3 20% 37% 19%	1900
	21st to end	Day	18% 4 8% 26% 35% 9%	2090
November	1st to 10th	Day	19% 4 7% 27% 33% 10%	1869
	11th to 20th	Day	18% 4 7% 30% 36% 5%	1758
	21st to end	Day	23% 4 8% 26% 27% 11%	1524
December	1st to 10th	Day	30% 4 13% 27% 19% 7%	1520
	11th to 20th	Day	35% 7% 13% 24% 16% 5%	1924
	21st to end	Day	34% 7% 10% 14% 18% 17%	3091
January	1st to 10th	Night	31% 6% 10% 30% 19% 4	4097
	11th to 20th	Night	25% 5% 16% 35% 15% 3	4110
	21st to end	Night	33% 6% 8% 28% 21% 4	4521
February	1st to 10th	Night	26% 5% 14% 25% 21% 9%	2470
	11th to 20th	Night	27% 4 10% 23% 27% 8%	2403
	21st to end	Night	29% 6% 7% 22% 28% 8%	1805
March	1st to 10th	Night	26% 7% 7% 27% 25% 8%	3430
	11th to 20th	Night	36% 8% 10% 23% 18% 5%	3490
	21st to end	Night	31% 9% 11% 22% 23% 3	3828
April	1st to 10th	Night	27% 5% 7% 20% 28% 12%	1990
	11th to 20th	Night	25% 6% 6% 20% 30% 13%	1877
	21st to end	Night	21% 6% 6% 25% 32% 10%	1805
May	1st to 10th	Night	17% 5% 8% 17% 41% 11%	2860
	11th to 20th	Night	18% 7% 8% 21% 34% 12%	2835
	21st to end	Night	16% 4 7% 17% 36% 19%	3110
June	1st to 10th	Night	16% 3 4 16% 36% 26%	1615
	11th to 20th	Night	17% 3 6% 10% 22% 43%	1520
	21st to end	Night	16% 4 4 13% 23% 39%	1704
July	1st to 10th	Night	17% 4 7% 7% 12% 54%	2815
	11th to 20th	Night	26% 7% 11% 18% 21% 18%	2806
	21st to end	Night	26% 7% 13% 16% 13% 25%	3011
August	1st to 10th	Night	36% 11% 16% 11% 11% 15%	2838
	11th to 20th	Night	24% 8% 14% 15% 20% 19%	2838
	21st to end	Night	26% 6% 10% 16% 21% 21%	3446
September	1st to 10th	Night	23% 5% 7% 15% 23% 27%	1900
	11th to 20th	Night	20% 5% 7% 18% 25% 26%	2076
	21st to end	Night	18% 3 4 14% 36% 26%	2090
October	1st to 10th	Night	23% 4 8% 19% 24% 23%	2272
	11th to 20th	Night	16% 3 5% 17% 36% 23%	2280
	21st to end	Night	18% 4 6% 24% 35% 13%	2508
November	1st to 10th	Night	19% 4 8% 23% 33% 13%	2244
	11th to 20th	Night	17% 4 6% 26% 38% 9%	2417
	21st to end	Night	24% 5% 7% 20% 31% 14%	2632
December	1st to 10th	Night	27% 5% 10% 27% 22% 8%	2660
	11th to 20th	Night	32% 5% 11% 24% 23% 5%	3272
	21st to end	Night	30% 6% 11% 17% 20% 17%	4586

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% 18% 35% 20% 10% 2	270
	11th to 20th	Day	12% 24% 31% 21% 10% 1	270
	21st to end	Day	9% 21% 31% 25% 12% 2	297
February	1st to 10th	Day	14% 27% 30% 21% 6%	270
	11th to 20th	Day	14% 28% 32% 16% 10%	270
	21st to end	Day	17% 32% 31% 15% 4	363
March	1st to 10th	Day	15% 26% 34% 18% 7%	460
	11th to 20th	Day	13% 24% 35% 18% 8% 2	460
	21st to end	Day	15% 34% 32% 13% 4 1	506
April	1st to 10th	Day	13% 30% 33% 15% 7% 3	460
	11th to 20th	Day	15% 31% 35% 13% 5% 2	452
	21st to end	Day	12% 30% 33% 17% 8% 1	460
May	1st to 10th	Day	12% 26% 39% 17% 5% 1	463
	11th to 20th	Day	9% 17% 36% 23% 12% 2	488
	21st to end	Day	11% 24% 31% 22% 9% 3	529
June	1st to 10th	Day	6% 12% 29% 33% 18% 2	571
	11th to 20th	Day	6% 15% 31% 28% 15% 5%	671
	21st to end	Day	6% 11% 38% 34% 9% 2	490
July	1st to 10th	Day	4 7% 27% 37% 22% 3	486
	11th to 20th	Day	4 2 19% 35% 33% 8%	484
	21st to end	Day	7% 5% 13% 42% 25% 8%	531
August	1st to 10th	Day	7% 4 21% 40% 24% 4	487
	11th to 20th	Day	6% 7% 23% 35% 21% 7%	477
	21st to end	Day	6% 5% 22% 35% 26% 7%	539
September	1st to 10th	Day	6% 5% 23% 34% 22% 9%	490
	11th to 20th	Day	9% 13% 28% 30% 14% 6%	490
	21st to end	Day	8% 14% 26% 33% 13% 6%	490
October	1st to 10th	Day	11% 18% 25% 20% 14% 12%	306
	11th to 20th	Day	9% 19% 25% 23% 18% 6%	300
	21st to end	Day	10% 22% 25% 26% 15% 2	330
November	1st to 10th	Day	12% 22% 26% 22% 16% 2	273
	11th to 20th	Day	7% 22% 30% 24% 13% 4	270
	21st to end	Day	8% 23% 29% 21% 14% 4	270
December	1st to 10th	Day	11% 21% 29% 22% 14% 3	270
	11th to 20th	Day	10% 19% 31% 25% 13% 2	270
	21st to end	Day	16% 23% 27% 24% 9% 1	297
January	1st to 10th	Night	7% 12% 26% 30% 20% 5%	760
	11th to 20th	Night	8% 12% 27% 30% 20% 3	760
	21st to end	Night	8% 13% 24% 32% 17% 4	836
February	1st to 10th	Night	8% 15% 26% 33% 15% 3	760
	11th to 20th	Night	7% 13% 32% 30% 15% 3	744
	21st to end	Night	10% 17% 28% 34% 9% 2	628
March	1st to 10th	Night	7% 16% 30% 31% 15% 2	760
	11th to 20th	Night	8% 11% 26% 29% 23% 3	760
	21st to end	Night	9% 18% 26% 30% 13% 2	836
April	1st to 10th	Night	6% 21% 28% 28% 15% 1	660
	11th to 20th	Night	6% 23% 25% 32% 12% 2	563
	21st to end	Night	7% 21% 26% 25% 17% 3	570
May	1st to 10th	Night	7% 14% 29% 32% 16% 2	570
	11th to 20th	Night	6% 9% 23% 35% 23% 4	561
	21st to end	Night	7% 14% 24% 28% 23% 4	617
June	1st to 10th	Night	4 8% 20% 36% 30% 3	570
	11th to 20th	Night	4 8% 25% 34% 24% 5%	570
	21st to end	Night	3 5% 18% 38% 32% 4	570
July	1st to 10th	Night	4 3 13% 30% 39% 10%	555
	11th to 20th	Night	5% 2 9% 31% 44% 9%	552
	21st to end	Night	5% 2 6% 28% 45% 13%	624
August	1st to 10th	Night	6% 2 9% 30% 44% 9%	567
	11th to 20th	Night	4 2 10% 36% 39% 9%	564
	21st to end	Night	6% 3 9% 29% 43% 11%	627
September	1st to 10th	Night	6% 3 11% 33% 40% 7%	570
	11th to 20th	Night	5% 5% 15% 32% 35% 8%	746
	21st to end	Night	7% 8% 15% 27% 33% 10%	760
October	1st to 10th	Night	9% 7% 22% 30% 26% 6%	760
	11th to 20th	Night	6% 8% 22% 34% 24% 7%	760
	21st to end	Night	9% 11% 20% 28% 25% 6%	836
November	1st to 10th	Night	8% 9% 21% 31% 24% 6%	748
	11th to 20th	Night	3 12% 25% 32% 22% 6%	760
	21st to end	Night	8% 15% 20% 31% 20% 6%	922
December	1st to 10th	Night	9% 10% 24% 36% 18% 3	950
	11th to 20th	Night	11% 11% 27% 29% 19% 2	950
	21st to end	Night	11% 14% 24% 35% 14% 2	875

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