Flying Horse Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flying Horse 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	13% 7% 3 7% 4 4 4 4 5% 7% 41%	101032
	Night	13% 8% 3 6% 4 4 4 3 5% 7% 43%	97938
Transparency	Day	41% 7% 11% 23% 16% 3	100830
	Night	40% 6% 10% 23% 17% 3	97811
Seeing	Day	15% 7% 22% 25% 20% 11%	15287
	Night	17% 7% 24% 31% 19% 3	25025

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	14% 12% 6% 11% 6% 5% 4 4 4 4 31%	2527
	11th to 20th	Day	19% 10% 3 9% 6% 4 5% 3 4 5% 33%	2530
	21st to end	Day	25% 12% 6% 6% 3 3 3 3 4 5% 30%	3354
February	1st to 10th	Day	18% 10% 3 8% 4 4 4 3 5% 6% 35%	1900
	11th to 20th	Day	21% 10% 3 7% 4 4 3 3 5% 6% 35%	1848
	21st to end	Day	18% 10% 3 8% 4 4 4 3 5% 6% 35%	1570
March	1st to 10th	Day	22% 13% 5% 7% 4 3 3 3 4 4 32%	3120
	11th to 20th	Day	14% 7% 2 6% 3 4 3 2 5% 7% 47%	3310
	21st to end	Day	13% 7% 3 7% 5% 4 4 3 5% 7% 42%	4059
April	1st to 10th	Day	13% 7% 3 7% 4 4 4 4 5% 7% 43%	2280
	11th to 20th	Day	15% 6% 3 7% 4 4 3 3 6% 6% 42%	2254
	21st to end	Day	15% 7% 3 6% 5% 5% 4 3 5% 7% 41%	2327
May	1st to 10th	Day	17% 7% 2 7% 5% 4 5% 4 7% 8% 33%	4082
	11th to 20th	Day	17% 7% 3 6% 4 4 4 3 6% 8% 37%	4081
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	4476
June	1st to 10th	Day	9% 6% 2 6% 4 4 5% 4 6% 9% 44%	2566
	11th to 20th	Day	5% 4 2 5% 4 5% 6% 5% 7% 10% 46%	2660
	21st to end	Day	5% 4 2 5% 5% 6% 6% 6% 8% 11% 43%	2660
July	1st to 10th	Day	8% 5% 3 7% 6% 6% 6% 4 7% 10% 38%	4440
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 11% 42%	4440
	21st to end	Day	16% 10% 4 10% 5% 6% 6% 4 7% 8% 26%	4499
August	1st to 10th	Day	5% 4 2 4 3 4 5% 4 7% 8% 55%	3927
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 10% 40%	3729
	21st to end	Day	5% 3 1 5% 4 4 5% 4 6% 9% 54%	4180
September	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	2266
	11th to 20th	Day	12% 6% 3 6% 5% 4 4 3 5% 6% 46%	2090
	21st to end	Day	12% 5% 2 6% 3 4 4 3 4 7% 49%	2090
October	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 4 6% 56%	2090
	11th to 20th	Day	13% 6% 2 5% 3 3 3 2 5% 6% 53%	2022
	21st to end	Day	18% 6% 2 6% 4 3 3 2 4 5% 47%	1891
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 6% 55%	1681
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 5% 7% 48%	1710
	21st to end	Day	17% 8% 2 6% 4 4 4 3 4 5% 45%	1710
December	1st to 10th	Day	21% 9% 3 7% 5% 3 4 4 4 5% 37%	1710
	11th to 20th	Day	15% 11% 3 6% 5% 4 5% 4 5% 5% 36%	2153
	21st to end	Day	16% 13% 5% 8% 5% 5% 5% 4 4 7% 28%	2800
January	1st to 10th	Night	17% 11% 4 7% 4 3 4 4 5% 6% 36%	4428
	11th to 20th	Night	17% 13% 3 9% 6% 5% 4 3 4 4 32%	4440
	21st to end	Night	23% 13% 4 6% 3 3 3 2 4 5% 33%	4297
February	1st to 10th	Night	22% 10% 3 8% 5% 4 3 3 4 5% 33%	2280
	11th to 20th	Night	20% 8% 3 7% 5% 3 4 3 3 5% 37%	2218
	21st to end	Night	21% 10% 4 7% 4 4 4 4 5% 5% 33%	1884
March	1st to 10th	Night	23% 10% 3 7% 4 4 4 3 4 5% 34%	3733
	11th to 20th	Night	12% 7% 3 6% 4 3 4 3 4 6% 49%	3649
	21st to end	Night	14% 8% 3 7% 4 4 4 3 5% 6% 42%	3599
April	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 5% 8% 47%	1900
	11th to 20th	Night	16% 6% 2 5% 4 4 3 3 5% 6% 46%	1875
	21st to end	Night	13% 7% 2 6% 5% 4 4 4 6% 9% 40%	1853
May	1st to 10th	Night	15% 9% 3 7% 4 4 4 4 5% 7% 39%	2813
	11th to 20th	Night	13% 7% 2 6% 4 5% 4 4 6% 7% 42%	2812
	21st to end	Night	7% 6% 2 6% 5% 5% 5% 5% 6% 10% 42%	3079
June	1st to 10th	Night	11% 7% 2 5% 4 4 4 3 6% 9% 46%	1609
	11th to 20th	Night	4 3 2 5% 4 3 4 4 7% 10% 56%	1520
	21st to end	Night	3 3 1 4 4 5% 4 6% 6% 12% 51%	1520
July	1st to 10th	Night	6% 4 2 5% 5% 5% 5% 4 8% 12% 44%	2530
	11th to 20th	Night	5% 4 3 5% 3 4 4 3 6% 10% 53%	2530
	21st to end	Night	10% 9% 3 10% 7% 6% 6% 5% 7% 8% 29%	3051
August	1st to 10th	Night	4 3 1 4 3 3 4 3 6% 7% 62%	2984
	11th to 20th	Night	4 3 2 6% 4 4 6% 5% 7% 11% 49%	3100
	21st to end	Night	4 3 1 4 3 4 4 4 6% 8% 59%	3476
September	1st to 10th	Night	10% 5% 2 6% 3 3 3 4 5% 8% 50%	1900
	11th to 20th	Night	10% 5% 2 6% 3 4 4 4 4 8% 50%	2085
	21st to end	Night	10% 5% 2 5% 3 3 4 3 4 6% 54%	2090
October	1st to 10th	Night	9% 5% 1 4 2 2 3 3 4 6% 62%	2090
	11th to 20th	Night	15% 6% 2 5% 3 3 2 3 3 5% 53%	2155
	21st to end	Night	15% 7% 2 5% 3 4 4 2 4 5% 49%	2705
November	1st to 10th	Night	12% 5% 1 4 4 4 4 2 5% 5% 54%	2420
	11th to 20th	Night	13% 6% 2 4 4 3 3 3 5% 7% 49%	2470
	21st to end	Night	16% 8% 3 5% 4 4 3 2 4 6% 47%	2470
December	1st to 10th	Night	20% 11% 3 7% 4 4 4 3 5% 5% 35%	2470
	11th to 20th	Night	18% 9% 3 6% 4 4 4 3 5% 6% 40%	3042
	21st to end	Night	17% 12% 5% 9% 6% 5% 5% 3 5% 5% 28%	4861

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	55% 6% 7% 21% 10% 2	2528
	11th to 20th	Day	53% 5% 8% 20% 13% 1	2530
	21st to end	Day	56% 5% 8% 21% 9% 1	3354
February	1st to 10th	Day	51% 4 8% 22% 13% 2	1900
	11th to 20th	Day	51% 4 7% 21% 13% 4	1858
	21st to end	Day	49% 5% 9% 17% 14% 6%	1570
March	1st to 10th	Day	56% 4 6% 16% 13% 6%	3120
	11th to 20th	Day	36% 6% 10% 27% 16% 5%	3310
	21st to end	Day	41% 7% 10% 25% 16% 1	4059
April	1st to 10th	Day	40% 6% 11% 22% 19% 2	2280
	11th to 20th	Day	41% 5% 9% 22% 20% 3	2254
	21st to end	Day	43% 5% 10% 25% 14% 2	2327
May	1st to 10th	Day	45% 9% 14% 21% 11% 1	4120
	11th to 20th	Day	44% 9% 11% 24% 12% 1	4085
	21st to end	Day	39% 9% 12% 20% 20% 1	4489
June	1st to 10th	Day	36% 9% 11% 23% 18% 3	2566
	11th to 20th	Day	29% 10% 16% 23% 18% 3	2660
	21st to end	Day	30% 10% 16% 22% 17% 5%	2660
July	1st to 10th	Day	39% 7% 17% 25% 10% 2	4371
	11th to 20th	Day	34% 8% 14% 32% 10% 2	4365
	21st to end	Day	55% 7% 12% 17% 7% 2	4356
August	1st to 10th	Day	25% 7% 13% 34% 21%	3914
	11th to 20th	Day	37% 7% 12% 25% 18% 1	3765
	21st to end	Day	26% 8% 9% 34% 21% 2	4179
September	1st to 10th	Day	38% 9% 10% 20% 19% 4	2266
	11th to 20th	Day	38% 7% 9% 22% 21% 3	2090
	21st to end	Day	34% 6% 10% 23% 22% 5%	2090
October	1st to 10th	Day	30% 4 9% 22% 29% 5%	2090
	11th to 20th	Day	33% 5% 7% 21% 26% 8%	2022
	21st to end	Day	40% 4 6% 23% 22% 5%	1891
November	1st to 10th	Day	31% 4 8% 24% 27% 5%	1681
	11th to 20th	Day	36% 5% 8% 22% 22% 6%	1710
	21st to end	Day	41% 4 7% 25% 18% 4	1710
December	1st to 10th	Day	49% 5% 9% 23% 13% 2	1710
	11th to 20th	Day	48% 6% 10% 20% 15% 2	2150
	21st to end	Day	52% 7% 12% 18% 10%	2800
January	1st to 10th	Night	47% 5% 9% 23% 14% 1	4428
	11th to 20th	Night	55% 6% 6% 17% 13% 3	4440
	21st to end	Night	54% 4 7% 21% 12% 1	4297
February	1st to 10th	Night	54% 4 8% 18% 14% 1	2280
	11th to 20th	Night	51% 4 6% 21% 14% 4	2219
	21st to end	Night	53% 6% 7% 15% 16% 4	1884
March	1st to 10th	Night	52% 6% 7% 14% 16% 5%	3733
	11th to 20th	Night	36% 5% 11% 24% 14% 10%	3649
	21st to end	Night	42% 5% 10% 24% 18% 1	3599
April	1st to 10th	Night	34% 6% 11% 26% 20% 3	1900
	11th to 20th	Night	38% 5% 10% 18% 23% 6%	1875
	21st to end	Night	40% 7% 10% 24% 18% 2	1853
May	1st to 10th	Night	42% 9% 13% 22% 12% 1	2840
	11th to 20th	Night	39% 8% 15% 22% 15% 1	2813
	21st to end	Night	32% 11% 15% 22% 17% 2	3087
June	1st to 10th	Night	35% 7% 13% 25% 18% 3	1609
	11th to 20th	Night	22% 6% 19% 27% 23% 3	1520
	21st to end	Night	25% 9% 17% 29% 14% 6%	1520
July	1st to 10th	Night	31% 7% 17% 31% 12% 2	2490
	11th to 20th	Night	27% 6% 13% 37% 15% 2	2482
	21st to end	Night	50% 9% 13% 18% 8% 1	2954
August	1st to 10th	Night	21% 6% 11% 39% 23% 1	2973
	11th to 20th	Night	26% 8% 18% 29% 17% 1	3130
	21st to end	Night	21% 6% 12% 35% 24% 3	3476
September	1st to 10th	Night	32% 8% 9% 24% 21% 6%	1900
	11th to 20th	Night	32% 5% 9% 25% 24% 5%	2085
	21st to end	Night	30% 6% 8% 24% 25% 7%	2090
October	1st to 10th	Night	25% 4 7% 24% 31% 9%	2090
	11th to 20th	Night	35% 4 8% 20% 26% 7%	2155
	21st to end	Night	38% 4 7% 23% 23% 6%	2705
November	1st to 10th	Night	33% 4 7% 24% 25% 7%	2420
	11th to 20th	Night	34% 4 7% 23% 23% 8%	2470
	21st to end	Night	41% 4 7% 25% 20% 4	2470
December	1st to 10th	Night	51% 5% 9% 20% 13% 2	2470
	11th to 20th	Night	45% 5% 8% 21% 18% 3	3044
	21st to end	Night	55% 8% 9% 17% 10% 2	4861

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	24% 14% 33% 20% 7% 1	270
	11th to 20th	Day	29% 18% 33% 15% 4	270
	21st to end	Day	24% 11% 45% 16% 4	297
February	1st to 10th	Day	25% 16% 37% 17% 4 1	270
	11th to 20th	Day	31% 17% 35% 14% 3 1	270
	21st to end	Day	30% 16% 34% 14% 5%	225
March	1st to 10th	Day	23% 17% 32% 23% 4 1	270
	11th to 20th	Day	23% 13% 38% 20% 5% 1	355
	21st to end	Day	21% 15% 35% 21% 7% 1	506
April	1st to 10th	Day	18% 13% 28% 27% 12% 2	460
	11th to 20th	Day	18% 13% 26% 25% 13% 4	452
	21st to end	Day	19% 9% 30% 27% 12% 4	460
May	1st to 10th	Day	18% 12% 27% 26% 13% 5%	463
	11th to 20th	Day	15% 6% 20% 29% 19% 10%	487
	21st to end	Day	10% 4 19% 28% 23% 17%	529
June	1st to 10th	Day	12% 4 17% 25% 26% 17%	586
	11th to 20th	Day	5% 3 15% 28% 32% 18%	680
	21st to end	Day	5% 3 17% 32% 28% 14%	680
July	1st to 10th	Day	11% 2 11% 24% 28% 23%	671
	11th to 20th	Day	9% 3 10% 23% 34% 22%	668
	21st to end	Day	12% 2 9% 25% 29% 23%	552
August	1st to 10th	Day	10% 2 7% 25% 33% 22%	486
	11th to 20th	Day	11% 2 11% 29% 33% 14%	479
	21st to end	Day	8% 2 6% 23% 32% 29%	539
September	1st to 10th	Day	14% 2 10% 23% 33% 18%	490
	11th to 20th	Day	11% 2 9% 25% 36% 17%	490
	21st to end	Day	15% 5% 19% 22% 26% 13%	490
October	1st to 10th	Day	10% 2 16% 33% 27% 12%	490
	11th to 20th	Day	14% 8% 30% 27% 14% 6%	422
	21st to end	Day	24% 9% 25% 28% 12% 2	330
November	1st to 10th	Day	17% 5% 29% 29% 17% 3	273
	11th to 20th	Day	15% 14% 31% 29% 10% 1	270
	21st to end	Day	23% 9% 29% 23% 14% 2	270
December	1st to 10th	Day	21% 13% 33% 23% 9% 2	270
	11th to 20th	Day	19% 17% 30% 20% 12% 1	270
	21st to end	Day	25% 15% 33% 23% 4	297
January	1st to 10th	Night	21% 16% 32% 26% 5%	950
	11th to 20th	Night	27% 12% 34% 22% 5%	950
	21st to end	Night	24% 9% 40% 23% 3	855
February	1st to 10th	Night	26% 12% 33% 25% 4	760
	11th to 20th	Night	26% 13% 35% 23% 3	743
	21st to end	Night	27% 13% 37% 22% 2	628
March	1st to 10th	Night	23% 13% 30% 29% 6%	760
	11th to 20th	Night	20% 12% 34% 28% 6% 1	760
	21st to end	Night	20% 10% 31% 31% 8%	708
April	1st to 10th	Night	14% 10% 33% 34% 8% 1	570
	11th to 20th	Night	18% 8% 31% 30% 12%	563
	21st to end	Night	16% 8% 28% 35% 12% 2	570
May	1st to 10th	Night	16% 5% 29% 30% 16% 3	570
	11th to 20th	Night	13% 4 21% 36% 21% 4	561
	21st to end	Night	7% 2 15% 40% 32% 5%	617
June	1st to 10th	Night	12% 3 13% 37% 30% 4	570
	11th to 20th	Night	5% 1 9% 42% 39% 4	570
	21st to end	Night	5% 1 11% 41% 37% 6%	570
July	1st to 10th	Night	8% 2 8% 30% 42% 11%	555
	11th to 20th	Night	10% 2 6% 30% 45% 7%	552
	21st to end	Night	9% 1 7% 33% 41% 8%	624
August	1st to 10th	Night	7% 1 4 35% 44% 9%	567
	11th to 20th	Night	7% 2 7% 39% 43% 4	564
	21st to end	Night	7% 1 7% 30% 47% 9%	627
September	1st to 10th	Night	12% 1 9% 30% 42% 6%	570
	11th to 20th	Night	12% 2 9% 30% 40% 6%	755
	21st to end	Night	12% 2 16% 32% 34% 4	760
October	1st to 10th	Night	11% 3 16% 36% 29% 5%	760
	11th to 20th	Night	17% 6% 22% 34% 19% 2	760
	21st to end	Night	17% 7% 29% 31% 15% 2	836
November	1st to 10th	Night	16% 5% 24% 35% 17% 3	745
	11th to 20th	Night	15% 9% 33% 31% 10% 1	760
	21st to end	Night	19% 9% 28% 32% 11% 1	760
December	1st to 10th	Night	26% 10% 26% 31% 7%	760
	11th to 20th	Night	23% 8% 31% 29% 8%	760
	21st to end	Night	26% 12% 30% 28% 4	1035

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