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 2024-03-06.

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	14% 7% 3 6% 5% 3 5% 5% 5% 7% 40%	78802
	Night	14% 7% 3 5% 5% 3 4 4 5% 7% 42%	80743
Transparency	Day	42% 7% 11% 22% 16% 3	78514
	Night	41% 6% 10% 22% 17% 4	80552
Seeing	Day	15% 7% 21% 24% 20% 11%	14302
	Night	17% 7% 24% 31% 19% 3	24233

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% 11% 6% 10% 7% 4 5% 5% 4 4 31%	2527
	11th to 20th	Day	19% 9% 3 7% 7% 3 5% 4 3 5% 33%	2530
	21st to end	Day	25% 11% 7% 5% 4 2 3 4 4 5% 30%	3354
February	1st to 10th	Day	19% 10% 3 7% 5% 2 5% 3 5% 6% 35%	1900
	11th to 20th	Day	21% 9% 4 6% 4 3 4 4 5% 6% 35%	1848
	21st to end	Day	18% 9% 4 7% 4 3 4 4 5% 6% 36%	1570
March	1st to 10th	Day	17% 9% 4 5% 4 3 4 4 4 5% 39%	1850
	11th to 20th	Day	22% 9% 3 6% 5% 3 4 3 4 6% 34%	1880
	21st to end	Day	17% 8% 4 7% 7% 3 5% 5% 5% 6% 33%	2312
April	1st to 10th	Day	12% 6% 3 6% 5% 3 5% 4 5% 7% 45%	2160
	11th to 20th	Day	15% 6% 3 7% 5% 3 4 4 5% 7% 42%	2134
	21st to end	Day	16% 6% 3 5% 5% 4 5% 4 5% 7% 41%	2204
May	1st to 10th	Day	16% 6% 2 5% 5% 3 5% 5% 5% 8% 40%	2340
	11th to 20th	Day	16% 6% 3 6% 6% 3 5% 4 6% 7% 39%	2301
	21st to end	Day	8% 5% 3 6% 7% 5% 6% 7% 7% 10% 38%	2531
June	1st to 10th	Day	9% 5% 2 5% 5% 3 5% 5% 6% 9% 45%	2430
	11th to 20th	Day	5% 3 2 5% 5% 3 6% 6% 7% 11% 46%	2520
	21st to end	Day	5% 4 2 4 5% 4 7% 7% 8% 11% 43%	2520
July	1st to 10th	Day	9% 5% 3 7% 7% 5% 7% 6% 7% 9% 35%	2520
	11th to 20th	Day	8% 5% 2 5% 6% 4 6% 7% 6% 10% 40%	2520
	21st to end	Day	9% 4 3 5% 5% 4 5% 7% 8% 11% 38%	2566
August	1st to 10th	Day	7% 5% 3 6% 5% 4 7% 6% 8% 10% 39%	2234
	11th to 20th	Day	9% 6% 2 6% 6% 4 5% 7% 6% 9% 39%	2125
	21st to end	Day	8% 5% 2 5% 6% 4 5% 6% 7% 10% 43%	2376
September	1st to 10th	Day	12% 5% 2 5% 6% 4 5% 6% 6% 8% 41%	2147
	11th to 20th	Day	12% 5% 3 5% 6% 3 4 5% 4 6% 47%	1980
	21st to end	Day	11% 5% 2 5% 4 3 4 4 4 7% 52%	1980
October	1st to 10th	Day	10% 5% 2 4 4 2 4 4 4 6% 54%	1980
	11th to 20th	Day	13% 6% 2 4 4 2 3 3 5% 6% 52%	1916
	21st to end	Day	19% 5% 3 5% 4 3 3 3 4 5% 46%	1792
November	1st to 10th	Day	12% 5% 2 4 3 2 3 4 3 6% 55%	1672
	11th to 20th	Day	15% 7% 2 4 4 2 3 4 5% 7% 48%	1710
	21st to end	Day	17% 7% 2 5% 4 3 4 4 4 5% 45%	1710
December	1st to 10th	Day	21% 8% 3 6% 6% 2 4 4 4 5% 37%	1710
	11th to 20th	Day	16% 10% 4 6% 5% 3 5% 5% 5% 5% 36%	2153
	21st to end	Day	16% 13% 5% 7% 6% 3 4 5% 4 7% 29%	2800
January	1st to 10th	Night	17% 10% 4 7% 4 2 4 4 4 7% 36%	4428
	11th to 20th	Night	17% 12% 4 8% 7% 4 5% 4 4 4 32%	4440
	21st to end	Night	23% 13% 4 5% 4 2 3 3 4 5% 33%	4297
February	1st to 10th	Night	22% 9% 4 7% 5% 4 4 3 4 5% 33%	2280
	11th to 20th	Night	21% 7% 4 7% 6% 3 4 4 3 5% 37%	2218
	21st to end	Night	21% 9% 4 6% 5% 3 4 4 5% 5% 33%	1884
March	1st to 10th	Night	17% 8% 2 4 5% 3 4 4 4 6% 42%	2227
	11th to 20th	Night	18% 8% 4 7% 5% 3 4 4 4 7% 38%	2079
	21st to end	Night	16% 8% 4 6% 5% 3 5% 4 5% 6% 36%	2057
April	1st to 10th	Night	11% 6% 2 4 4 2 4 5% 5% 9% 49%	1800
	11th to 20th	Night	16% 5% 2 4 4 3 3 4 5% 7% 46%	1775
	21st to end	Night	14% 6% 3 5% 5% 3 5% 5% 6% 9% 40%	1756
May	1st to 10th	Night	13% 7% 3 5% 4 3 3 4 5% 7% 44%	1620
	11th to 20th	Night	11% 5% 3 6% 5% 4 4 5% 7% 8% 41%	1592
	21st to end	Night	6% 4 2 4 6% 4 6% 6% 7% 11% 44%	1744
June	1st to 10th	Night	10% 6% 2 5% 5% 2 5% 4 5% 8% 48%	1525
	11th to 20th	Night	4 2 2 4 5% 2 4 5% 7% 10% 56%	1440
	21st to end	Night	3 2 1 4 4 3 5% 7% 6% 13% 51%	1440
July	1st to 10th	Night	7% 4 3 4 6% 4 5% 5% 7% 11% 45%	1440
	11th to 20th	Night	7% 4 3 5% 4 3 5% 5% 6% 10% 49%	1440
	21st to end	Night	7% 3 2 5% 5% 3 6% 6% 8% 10% 46%	1748
August	1st to 10th	Night	7% 4 2 5% 5% 3 5% 5% 7% 9% 50%	1700
	11th to 20th	Night	6% 3 2 5% 5% 3 6% 6% 7% 9% 47%	1776
	21st to end	Night	7% 4 2 4 4 3 4 5% 6% 10% 50%	1980
September	1st to 10th	Night	11% 5% 2 6% 3 2 4 5% 5% 8% 50%	1800
	11th to 20th	Night	10% 4 2 5% 4 3 4 4 4 8% 51%	1975
	21st to end	Night	9% 4 2 4 3 2 4 4 4 6% 56%	1980
October	1st to 10th	Night	9% 4 2 3 3 2 3 4 4 6% 61%	1980
	11th to 20th	Night	16% 6% 2 5% 4 2 3 4 3 5% 50%	2041
	21st to end	Night	16% 7% 2 5% 4 3 4 3 4 6% 47%	2562
November	1st to 10th	Night	13% 4 2 4 4 2 4 3 4 5% 54%	2406
	11th to 20th	Night	13% 6% 2 4 4 2 3 3 4 8% 50%	2470
	21st to end	Night	16% 8% 3 4 4 3 3 3 4 6% 47%	2470
December	1st to 10th	Night	20% 10% 3 6% 5% 3 4 3 5% 5% 35%	2470
	11th to 20th	Night	18% 9% 3 5% 4 3 4 4 5% 6% 40%	3042
	21st to end	Night	17% 12% 5% 8% 7% 4 5% 4 5% 6% 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	48% 4 8% 20% 18% 4	1850
	11th to 20th	Day	52% 5% 10% 20% 11% 2	1880
	21st to end	Day	51% 7% 10% 20% 11% 2	2312
April	1st to 10th	Day	39% 6% 11% 22% 20% 2	2160
	11th to 20th	Day	42% 5% 9% 21% 20% 3	2134
	21st to end	Day	44% 5% 10% 25% 14% 2	2204
May	1st to 10th	Day	42% 6% 13% 26% 12% 1	2340
	11th to 20th	Day	44% 8% 11% 23% 13% 1	2305
	21st to end	Day	40% 9% 16% 22% 11% 2	2531
June	1st to 10th	Day	35% 9% 12% 24% 18% 2	2430
	11th to 20th	Day	29% 10% 17% 24% 17% 3	2520
	21st to end	Day	30% 10% 16% 22% 17% 5%	2520
July	1st to 10th	Day	42% 10% 13% 19% 13% 4	2451
	11th to 20th	Day	36% 11% 17% 21% 13% 3	2445
	21st to end	Day	35% 10% 17% 25% 11% 3	2423
August	1st to 10th	Day	37% 10% 15% 25% 13%	2221
	11th to 20th	Day	40% 9% 13% 21% 16% 2	2125
	21st to end	Day	34% 10% 13% 23% 16% 4	2376
September	1st to 10th	Day	38% 9% 11% 21% 18% 3	2147
	11th to 20th	Day	38% 7% 9% 21% 22% 3	1980
	21st to end	Day	31% 6% 11% 24% 23% 5%	1980
October	1st to 10th	Day	31% 5% 9% 23% 27% 5%	1980
	11th to 20th	Day	34% 5% 7% 20% 25% 8%	1916
	21st to end	Day	41% 4 6% 22% 22% 4	1792
November	1st to 10th	Day	31% 4 8% 24% 27% 5%	1672
	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	44% 5% 8% 17% 19% 6%	2227
	11th to 20th	Night	47% 5% 10% 21% 14% 2	2079
	21st to end	Night	48% 6% 11% 22% 12% 2	2057
April	1st to 10th	Night	33% 5% 12% 26% 20% 3	1800
	11th to 20th	Night	38% 5% 10% 18% 23% 6%	1775
	21st to end	Night	40% 7% 10% 24% 17% 1	1756
May	1st to 10th	Night	39% 6% 11% 24% 18% 3	1620
	11th to 20th	Night	38% 9% 15% 22% 15% 1	1593
	21st to end	Night	31% 10% 18% 23% 15% 2	1745
June	1st to 10th	Night	34% 6% 13% 26% 18% 3	1525
	11th to 20th	Night	22% 7% 19% 28% 21% 3	1440
	21st to end	Night	25% 9% 17% 29% 13% 6%	1440
July	1st to 10th	Night	31% 9% 17% 26% 14% 3	1400
	11th to 20th	Night	31% 8% 17% 23% 17% 4	1392
	21st to end	Night	28% 12% 16% 28% 13% 2	1651
August	1st to 10th	Night	29% 9% 16% 28% 18% 1	1689
	11th to 20th	Night	28% 12% 18% 22% 17% 2	1776
	21st to end	Night	28% 8% 15% 27% 17% 5%	1980
September	1st to 10th	Night	32% 8% 9% 25% 20% 5%	1800
	11th to 20th	Night	31% 5% 9% 25% 24% 5%	1975
	21st to end	Night	28% 6% 8% 24% 26% 7%	1980
October	1st to 10th	Night	26% 5% 8% 24% 29% 8%	1980
	11th to 20th	Night	37% 4 8% 19% 25% 6%	2041
	21st to end	Night	39% 4 7% 23% 22% 5%	2562
November	1st to 10th	Night	33% 4 7% 24% 25% 7%	2406
	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	22% 17% 32% 23% 4 1	255
	11th to 20th	Day	25% 13% 36% 19% 6% 2	320
	21st to end	Day	22% 14% 34% 21% 7% 2	462
April	1st to 10th	Day	16% 14% 27% 28% 13% 2	420
	11th to 20th	Day	18% 12% 26% 26% 14% 4	412
	21st to end	Day	20% 9% 29% 26% 11% 5%	420
May	1st to 10th	Day	17% 11% 27% 27% 12% 4	423
	11th to 20th	Day	15% 5% 21% 29% 19% 11%	447
	21st to end	Day	9% 4 16% 27% 25% 18%	485
June	1st to 10th	Day	11% 3 16% 25% 27% 18%	540
	11th to 20th	Day	4 3 15% 28% 31% 19%	630
	21st to end	Day	5% 3 17% 31% 29% 15%	630
July	1st to 10th	Day	11% 2 10% 24% 28% 25%	621
	11th to 20th	Day	10% 3 9% 22% 34% 23%	618
	21st to end	Day	9% 1 9% 25% 30% 25%	507
August	1st to 10th	Day	10% 2 6% 26% 33% 23%	446
	11th to 20th	Day	12% 2 9% 27% 35% 15%	439
	21st to end	Day	8% 2 6% 24% 33% 26%	495
September	1st to 10th	Day	14% 2 9% 22% 33% 20%	450
	11th to 20th	Day	11% 2 9% 23% 37% 17%	450
	21st to end	Day	13% 4 19% 23% 27% 14%	450
October	1st to 10th	Day	11% 2 17% 33% 25% 12%	450
	11th to 20th	Day	15% 8% 31% 28% 13% 5%	386
	21st to end	Day	26% 10% 24% 27% 12% 2	297
November	1st to 10th	Day	17% 6% 29% 28% 17% 3	270
	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	22% 13% 30% 30% 6%	743
	11th to 20th	Night	21% 11% 33% 27% 6% 1	720
	21st to end	Night	20% 10% 30% 32% 8%	671
April	1st to 10th	Night	14% 8% 33% 35% 9% 1	540
	11th to 20th	Night	19% 7% 30% 30% 13%	533
	21st to end	Night	16% 7% 27% 35% 13% 2	540
May	1st to 10th	Night	16% 5% 30% 30% 16% 3	540
	11th to 20th	Night	13% 4 21% 36% 21% 5%	531
	21st to end	Night	7% 1 14% 39% 33% 5%	584
June	1st to 10th	Night	12% 3 13% 37% 31% 4	540
	11th to 20th	Night	5% 1 9% 42% 39% 4	540
	21st to end	Night	5% 1 11% 40% 38% 6%	540
July	1st to 10th	Night	8% 2 7% 29% 42% 12%	525
	11th to 20th	Night	10% 2 7% 29% 46% 7%	522
	21st to end	Night	8% 1 7% 33% 42% 9%	591
August	1st to 10th	Night	8% 1 4 35% 44% 8%	537
	11th to 20th	Night	7% 2 6% 38% 44% 4	534
	21st to end	Night	7% 1 7% 30% 47% 9%	594
September	1st to 10th	Night	12% 1 9% 29% 43% 6%	540
	11th to 20th	Night	12% 2 9% 30% 40% 7%	715
	21st to end	Night	11% 2 17% 32% 35% 4	720
October	1st to 10th	Night	12% 3 16% 36% 28% 6%	720
	11th to 20th	Night	18% 6% 22% 34% 18% 2	720
	21st to end	Night	18% 7% 29% 30% 14% 2	792
November	1st to 10th	Night	16% 5% 24% 35% 17% 3	740
	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

Page generated at 2024-03-03 05:28:54. Version ac07

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