Starry Nights Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starry Nights Ranch clear sky chart from 2005-11-06 to 2024-12-02.

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	7% 6% 2 8% 6% 6% 6% 5% 8% 10% 35%	101019
	Night	7% 6% 2 7% 5% 5% 5% 4 7% 10% 41%	98553
Transparency	Day	41% 9% 16% 19% 12% 3	104744
	Night	37% 8% 18% 21% 12% 4	102967
Seeing	Day	8% 6% 20% 25% 23% 18%	15883
	Night	9% 4 19% 32% 27% 9%	25975

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	10% 8% 3 7% 6% 3 5% 4 5% 7% 42%	2836
	11th to 20th	Day	15% 9% 3 7% 5% 5% 5% 4 6% 9% 31%	2840
	21st to end	Day	9% 7% 2 9% 6% 5% 5% 5% 7% 6% 39%	3170
February	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 4 7% 8% 44%	1900
	11th to 20th	Day	6% 5% 2 5% 5% 4 5% 4 6% 9% 51%	1876
	21st to end	Day	7% 4 2 5% 5% 5% 4 5% 6% 8% 49%	1727
March	1st to 10th	Day	6% 5% 3 8% 7% 6% 6% 6% 8% 9% 34%	3435
	11th to 20th	Day	4 3 2 5% 5% 4 4 4 8% 9% 52%	3480
	21st to end	Day	9% 4 2 5% 4 5% 5% 5% 7% 9% 48%	3815
April	1st to 10th	Day	5% 3 2 6% 5% 6% 7% 5% 7% 10% 44%	2090
	11th to 20th	Day	7% 5% 2 7% 6% 6% 6% 4 8% 9% 40%	2135
	21st to end	Day	6% 3 2 6% 5% 5% 6% 6% 7% 9% 45%	2280
May	1st to 10th	Day	3 2 1 5% 4 4 5% 4 7% 10% 54%	3765
	11th to 20th	Day	7% 5% 2 7% 6% 7% 6% 6% 9% 11% 35%	4076
	21st to end	Day	4 4 2 5% 5% 5% 5% 4 6% 9% 50%	4476
June	1st to 10th	Day	11% 9% 4 11% 8% 8% 7% 5% 9% 10% 19%	2470
	11th to 20th	Day	6% 7% 3 10% 9% 8% 8% 6% 8% 11% 23%	2470
	21st to end	Day	8% 7% 3 12% 8% 9% 8% 6% 9% 9% 22%	2470
July	1st to 10th	Day	7% 6% 3 9% 8% 8% 8% 6% 9% 12% 23%	4120
	11th to 20th	Day	5% 6% 3 10% 9% 8% 9% 7% 10% 12% 23%	4120
	21st to end	Day	5% 6% 3 10% 8% 8% 9% 7% 10% 13% 23%	4466
August	1st to 10th	Day	4 6% 3 11% 8% 8% 8% 8% 10% 13% 21%	4104
	11th to 20th	Day	4 4 2 7% 6% 8% 7% 7% 9% 12% 34%	3804
	21st to end	Day	5% 5% 3 11% 9% 9% 9% 7% 9% 13% 21%	3833
September	1st to 10th	Day	8% 6% 3 12% 9% 9% 8% 5% 9% 10% 20%	2090
	11th to 20th	Day	8% 7% 4 10% 9% 9% 8% 7% 8% 8% 22%	2090
	21st to end	Day	9% 7% 3 9% 7% 8% 8% 6% 9% 9% 24%	2090
October	1st to 10th	Day	10% 7% 3 9% 6% 7% 6% 6% 7% 10% 30%	2028
	11th to 20th	Day	6% 6% 2 7% 7% 6% 6% 5% 8% 9% 38%	1900
	21st to end	Day	7% 6% 3 5% 5% 4 6% 5% 7% 10% 43%	2090
November	1st to 10th	Day	6% 5% 2 7% 6% 6% 5% 5% 7% 9% 41%	1957
	11th to 20th	Day	7% 7% 3 7% 6% 6% 5% 5% 6% 9% 38%	2000
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	2000
December	1st to 10th	Day	7% 6% 2 7% 4 5% 5% 5% 6% 8% 44%	1739
	11th to 20th	Day	11% 6% 2 7% 4 6% 5% 4 6% 7% 43%	2153
	21st to end	Day	11% 6% 2 8% 7% 7% 7% 5% 6% 9% 33%	3124
January	1st to 10th	Night	10% 7% 3 7% 5% 5% 5% 4 6% 9% 39%	4109
	11th to 20th	Night	16% 13% 5% 8% 5% 4 4 3 5% 7% 30%	4120
	21st to end	Night	10% 7% 3 6% 5% 5% 6% 5% 6% 6% 42%	4468
February	1st to 10th	Night	11% 6% 2 6% 3 4 4 4 6% 8% 45%	2280
	11th to 20th	Night	9% 4 1 5% 4 3 4 3 6% 8% 52%	2188
	21st to end	Night	6% 4 2 4 4 4 4 3 5% 8% 57%	1727
March	1st to 10th	Night	10% 8% 3 9% 5% 5% 5% 4 5% 8% 38%	3418
	11th to 20th	Night	4 3 1 4 4 3 5% 4 8% 12% 52%	3480
	21st to end	Night	8% 5% 1 6% 3 3 4 4 6% 7% 53%	3817
April	1st to 10th	Night	4 4 1 3 4 3 4 4 6% 9% 57%	2090
	11th to 20th	Night	6% 3 2 5% 4 4 4 4 9% 9% 50%	1992
	21st to end	Night	5% 3 1 5% 4 5% 5% 4 5% 8% 54%	1900
May	1st to 10th	Night	3 3 1 4 3 4 4 4 5% 8% 60%	3130
	11th to 20th	Night	6% 4 2 5% 4 4 5% 5% 8% 10% 46%	2830
	21st to end	Night	4 4 2 5% 4 4 4 4 7% 9% 53%	3079
June	1st to 10th	Night	10% 8% 3 8% 6% 7% 7% 5% 8% 9% 30%	1710
	11th to 20th	Night	6% 6% 3 7% 8% 6% 7% 6% 8% 13% 30%	1710
	21st to end	Night	6% 6% 3 6% 7% 7% 6% 5% 9% 11% 33%	1710
July	1st to 10th	Night	6% 6% 2 7% 6% 5% 6% 6% 7% 14% 35%	2840
	11th to 20th	Night	5% 5% 3 7% 6% 6% 7% 6% 10% 13% 33%	2840
	21st to end	Night	4 7% 3 9% 7% 7% 7% 7% 9% 12% 29%	3087
August	1st to 10th	Night	3 6% 3 8% 6% 6% 7% 6% 8% 12% 34%	2825
	11th to 20th	Night	5% 4 3 8% 6% 5% 6% 4 9% 14% 36%	2992
	21st to end	Night	6% 5% 3 7% 6% 6% 7% 6% 9% 15% 29%	3816
September	1st to 10th	Night	7% 7% 2 8% 7% 7% 7% 6% 10% 12% 27%	2090
	11th to 20th	Night	8% 7% 4 10% 7% 6% 6% 5% 8% 12% 28%	2090
	21st to end	Night	10% 7% 4 9% 6% 6% 7% 5% 6% 11% 29%	2090
October	1st to 10th	Night	10% 7% 3 7% 4 5% 6% 5% 7% 9% 36%	2152
	11th to 20th	Night	6% 6% 2 6% 5% 4 6% 4 6% 9% 45%	2280
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 6% 9% 47%	2508
November	1st to 10th	Night	8% 5% 2 6% 5% 4 5% 3 7% 9% 46%	2341
	11th to 20th	Night	7% 6% 2 6% 5% 4 5% 5% 7% 8% 45%	2400
	21st to end	Night	8% 6% 3 6% 5% 4 5% 3 6% 8% 46%	2400
December	1st to 10th	Night	6% 5% 2 5% 5% 5% 5% 4 6% 7% 49%	2470
	11th to 20th	Night	11% 8% 2 6% 4 4 4 4 5% 7% 46%	3042
	21st to end	Night	10% 8% 3 8% 6% 6% 6% 4 7% 7% 35%	4532

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	42% 5% 6% 18% 22% 6%	2837
	11th to 20th	Day	50% 5% 8% 18% 15% 4	2840
	21st to end	Day	43% 6% 7% 20% 17% 7%	3170
February	1st to 10th	Day	36% 6% 10% 21% 21% 7%	1900
	11th to 20th	Day	29% 7% 8% 25% 21% 10%	1886
	21st to end	Day	31% 6% 11% 17% 25% 10%	1727
March	1st to 10th	Day	43% 8% 14% 18% 13% 4	3435
	11th to 20th	Day	27% 5% 15% 32% 16% 4	3480
	21st to end	Day	32% 8% 9% 27% 16% 9%	3815
April	1st to 10th	Day	32% 6% 14% 26% 17% 5%	2090
	11th to 20th	Day	37% 7% 13% 20% 19% 5%	2135
	21st to end	Day	32% 8% 10% 20% 24% 6%	2280
May	1st to 10th	Day	20% 10% 12% 33% 20% 5%	3800
	11th to 20th	Day	38% 9% 20% 22% 11%	4080
	21st to end	Day	30% 8% 13% 34% 15% 1	4489
June	1st to 10th	Day	56% 9% 17% 14% 4	2470
	11th to 20th	Day	50% 12% 20% 16% 2	2470
	21st to end	Day	55% 10% 22% 11% 2	2470
July	1st to 10th	Day	47% 13% 26% 12% 3	4055
	11th to 20th	Day	48% 14% 30% 8%	4051
	21st to end	Day	46% 17% 25% 12%	4324
August	1st to 10th	Day	47% 15% 29% 8% 1	4091
	11th to 20th	Day	37% 13% 29% 13% 7%	3842
	21st to end	Day	48% 15% 28% 7% 2	3833
September	1st to 10th	Day	53% 14% 20% 12% 1	2090
	11th to 20th	Day	53% 13% 20% 11% 2	2090
	21st to end	Day	50% 12% 17% 12% 8% 1	2090
October	1st to 10th	Day	54% 10% 16% 12% 6% 2	3366
	11th to 20th	Day	35% 7% 10% 24% 21% 4	3140
	21st to end	Day	33% 6% 9% 25% 22% 5%	3428
November	1st to 10th	Day	37% 7% 11% 19% 17% 9%	1957
	11th to 20th	Day	41% 7% 9% 20% 14% 8%	2000
	21st to end	Day	37% 6% 11% 21% 18% 8%	2000
December	1st to 10th	Day	36% 7% 13% 24% 16% 4	1739
	11th to 20th	Day	40% 5% 11% 19% 17% 9%	2150
	21st to end	Day	46% 7% 10% 19% 14% 4	3124
January	1st to 10th	Night	41% 5% 12% 23% 15% 4	4109
	11th to 20th	Night	53% 4 8% 22% 10% 3	4120
	21st to end	Night	41% 5% 10% 20% 16% 8%	4468
February	1st to 10th	Night	35% 6% 12% 21% 18% 8%	2280
	11th to 20th	Night	27% 6% 11% 24% 23% 9%	2189
	21st to end	Night	26% 5% 12% 22% 28% 7%	1727
March	1st to 10th	Night	45% 6% 14% 19% 13% 4	3418
	11th to 20th	Night	22% 6% 24% 32% 13% 4	3480
	21st to end	Night	28% 7% 13% 25% 22% 5%	3817
April	1st to 10th	Night	23% 6% 19% 30% 15% 7%	2090
	11th to 20th	Night	27% 6% 18% 24% 21% 4	1992
	21st to end	Night	26% 7% 14% 26% 23% 5%	1900
May	1st to 10th	Night	20% 6% 20% 35% 16% 5%	3160
	11th to 20th	Night	30% 9% 21% 31% 8% 1	2831
	21st to end	Night	24% 8% 16% 37% 14%	3087
June	1st to 10th	Night	46% 9% 23% 17% 4	1710
	11th to 20th	Night	42% 11% 24% 20% 2	1710
	21st to end	Night	40% 15% 26% 16% 3	1710
July	1st to 10th	Night	37% 12% 30% 20% 1	2795
	11th to 20th	Night	37% 14% 39% 9% 1	2786
	21st to end	Night	40% 15% 28% 15% 1	2988
August	1st to 10th	Night	37% 14% 36% 12% 2	2814
	11th to 20th	Night	35% 13% 30% 14% 7%	3020
	21st to end	Night	41% 15% 35% 9% 1	3816
September	1st to 10th	Night	44% 17% 25% 13% 1	2090
	11th to 20th	Night	45% 14% 24% 15% 2	2090
	21st to end	Night	47% 12% 18% 15% 8% 1	2090
October	1st to 10th	Night	55% 10% 14% 11% 8% 2	3594
	11th to 20th	Night	33% 7% 11% 25% 21% 3	3779
	21st to end	Night	33% 5% 10% 26% 20% 6%	4120
November	1st to 10th	Night	33% 7% 12% 21% 19% 8%	2341
	11th to 20th	Night	34% 6% 13% 26% 15% 7%	2400
	21st to end	Night	35% 5% 11% 22% 21% 6%	2400
December	1st to 10th	Night	32% 6% 12% 29% 13% 6%	2470
	11th to 20th	Night	37% 7% 10% 19% 15% 11%	3044
	21st to end	Night	46% 7% 13% 17% 13% 5%	4532

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	8% 15% 43% 24% 10%	270
	11th to 20th	Day	11% 14% 38% 21% 10% 5%	270
	21st to end	Day	16% 16% 46% 16% 5%	297
February	1st to 10th	Day	13% 13% 32% 30% 11% 1	270
	11th to 20th	Day	10% 11% 32% 31% 13% 4	298
	21st to end	Day	7% 9% 30% 32% 21% 1	382
March	1st to 10th	Day	4 11% 36% 33% 14% 2	460
	11th to 20th	Day	8% 8% 31% 32% 18% 3	460
	21st to end	Day	5% 10% 29% 32% 20% 4	506
April	1st to 10th	Day	5% 10% 38% 26% 16% 5%	460
	11th to 20th	Day	7% 9% 29% 31% 18% 6%	452
	21st to end	Day	7% 4 26% 31% 22% 10%	460
May	1st to 10th	Day	5% 4 21% 33% 25% 13%	463
	11th to 20th	Day	9% 5% 20% 27% 26% 13%	487
	21st to end	Day	9% 3 10% 24% 33% 21%	529
June	1st to 10th	Day	13% 3 12% 21% 30% 20%	490
	11th to 20th	Day	7% 2 11% 19% 31% 30%	490
	21st to end	Day	7% 4 3 17% 28% 42%	490
July	1st to 10th	Day	6% 2 3 11% 30% 48%	485
	11th to 20th	Day	6% 2 3 14% 29% 45%	484
	21st to end	Day	9% 2 5% 17% 26% 41%	532
August	1st to 10th	Day	5% 3 6% 17% 26% 44%	486
	11th to 20th	Day	5% 3 3 12% 29% 48%	479
	21st to end	Day	9% 3 8% 22% 25% 34%	539
September	1st to 10th	Day	9% 3 5% 17% 27% 40%	490
	11th to 20th	Day	7% 3 8% 22% 28% 32%	490
	21st to end	Day	8% 3 9% 23% 31% 26%	490
October	1st to 10th	Day	14% 3 16% 33% 24% 10%	490
	11th to 20th	Day	8% 4 22% 32% 26% 8%	490
	21st to end	Day	8% 5% 24% 34% 23% 6%	539
November	1st to 10th	Day	11% 8% 20% 31% 24% 6%	495
	11th to 20th	Day	12% 8% 26% 32% 19% 4	500
	21st to end	Day	8% 5% 29% 34% 21% 3	500
December	1st to 10th	Day	8% 9% 35% 29% 15% 3	293
	11th to 20th	Day	10% 11% 32% 30% 15% 2	270
	21st to end	Day	10% 10% 30% 33% 14% 3	297
January	1st to 10th	Night	11% 8% 29% 35% 16% 1	760
	11th to 20th	Night	12% 7% 29% 38% 12% 2	760
	21st to end	Night	12% 9% 36% 32% 11%	836
February	1st to 10th	Night	12% 8% 29% 38% 13%	760
	11th to 20th	Night	9% 7% 32% 38% 13% 1	743
	21st to end	Night	9% 6% 30% 42% 13%	628
March	1st to 10th	Night	6% 8% 37% 38% 11% 1	760
	11th to 20th	Night	7% 5% 31% 40% 16% 1	760
	21st to end	Night	7% 7% 31% 40% 15%	836
April	1st to 10th	Night	5% 7% 32% 42% 14% 1	760
	11th to 20th	Night	7% 6% 28% 43% 16% 1	751
	21st to end	Night	6% 5% 27% 45% 16% 1	760
May	1st to 10th	Night	6% 2 23% 45% 22% 2	760
	11th to 20th	Night	9% 3 13% 41% 30% 3	579
	21st to end	Night	6% 3 8% 35% 41% 8%	617
June	1st to 10th	Night	14% 2 5% 30% 40% 9%	570
	11th to 20th	Night	6% 2 5% 24% 43% 20%	570
	21st to end	Night	8% 1 2 16% 46% 26%	570
July	1st to 10th	Night	7% 2 1 13% 48% 29%	555
	11th to 20th	Night	6% 2 2 11% 45% 35%	552
	21st to end	Night	4 2 2 11% 47% 35%	624
August	1st to 10th	Night	4 1 4 14% 47% 30%	567
	11th to 20th	Night	6% 1 2 14% 47% 30%	681
	21st to end	Night	11% 3 6% 19% 39% 22%	836
September	1st to 10th	Night	9% 2 4 15% 46% 23%	760
	11th to 20th	Night	10% 3 4 22% 43% 18%	760
	21st to end	Night	14% 3 6% 23% 39% 15%	760
October	1st to 10th	Night	14% 2 12% 36% 27% 8%	760
	11th to 20th	Night	7% 3 13% 38% 33% 5%	760
	21st to end	Night	11% 2 21% 35% 27% 4	836
November	1st to 10th	Night	11% 4 23% 36% 24% 2	780
	11th to 20th	Night	8% 4 24% 40% 21% 3	800
	21st to end	Night	10% 6% 23% 39% 21% 1	800
December	1st to 10th	Night	9% 5% 23% 38% 23% 2	768
	11th to 20th	Night	9% 7% 23% 37% 21% 3	760
	21st to end	Night	8% 5% 28% 36% 22% 1	836

Page generated at 2024-11-29 10:43:04. Version ac07

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