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 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	13% 7% 3 7% 5% 4 5% 4 6% 8% 40%	148895
	Night	13% 7% 3 7% 4 4 4 3 5% 7% 42%	143008
Transparency	Day	41% 5% 11% 24% 16% 3	152559
	Night	40% 5% 11% 23% 18% 4	147419
Seeing	Day	15% 8% 22% 24% 20% 10%	17939
	Night	17% 7% 24% 31% 19% 3	27592

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	15% 10% 6% 11% 5% 5% 4 3 5% 4 32%	4691
	11th to 20th	Day	12% 8% 3 9% 4 3 3 2 3 5% 47%	4710
	21st to end	Day	20% 9% 4 5% 4 4 4 3 4 5% 37%	6232
February	1st to 10th	Day	18% 10% 3 8% 4 4 4 3 5% 6% 35%	2100
	11th to 20th	Day	21% 9% 4 7% 4 4 3 3 4 6% 34%	2048
	21st to end	Day	17% 10% 3 8% 4 4 4 3 5% 6% 37%	1730
March	1st to 10th	Day	17% 12% 5% 8% 4 4 4 3 4 4 36%	4580
	11th to 20th	Day	13% 8% 3 7% 3 4 3 2 4 6% 47%	4845
	21st to end	Day	12% 7% 3 7% 5% 4 4 3 5% 7% 43%	5948
April	1st to 10th	Day	13% 6% 2 7% 4 4 4 3 5% 7% 43%	2520
	11th to 20th	Day	14% 6% 3 7% 4 4 4 3 6% 7% 42%	2494
	21st to end	Day	14% 7% 3 6% 5% 5% 4 3 5% 8% 41%	2572
May	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 6% 8% 32%	7616
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 8% 37%	7626
	21st to end	Day	17% 8% 4 8% 5% 5% 5% 4 5% 7% 30%	8391
June	1st to 10th	Day	9% 6% 2 6% 4 5% 5% 4 6% 8% 43%	2836
	11th to 20th	Day	7% 4 2 5% 4 5% 6% 5% 7% 10% 45%	2940
	21st to end	Day	5% 4 1 5% 5% 5% 6% 5% 8% 11% 44%	2940
July	1st to 10th	Day	8% 6% 3 8% 6% 6% 6% 4 7% 10% 36%	8280
	11th to 20th	Day	8% 5% 2 8% 6% 6% 7% 6% 8% 12% 32%	8280
	21st to end	Day	10% 6% 3 7% 4 5% 6% 5% 8% 12% 33%	8401
August	1st to 10th	Day	7% 4 2 5% 4 5% 5% 4 7% 8% 48%	5762
	11th to 20th	Day	6% 5% 2 6% 5% 5% 5% 5% 7% 10% 45%	5486
	21st to end	Day	4 3 1 4 4 3 4 3 6% 9% 59%	6080
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 6% 8% 43%	2504
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 4 5% 6% 48%	2310
	21st to end	Day	11% 6% 2 6% 4 4 4 3 4 7% 49%	2310
October	1st to 10th	Day	10% 5% 2 5% 2 3 4 3 4 6% 56%	2310
	11th to 20th	Day	12% 6% 2 4 3 2 3 2 5% 6% 54%	2161
	21st to end	Day	19% 6% 2 6% 3 3 3 2 4 5% 46%	1990
November	1st to 10th	Day	13% 6% 2 5% 3 2 3 3 4 6% 53%	1852
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 5% 7% 47%	1890
	21st to end	Day	16% 8% 2 6% 4 4 4 3 4 5% 43%	1890
December	1st to 10th	Day	17% 7% 2 7% 5% 3 4 3 4 6% 44%	3020
	11th to 20th	Day	18% 10% 4 7% 5% 4 4 3 5% 6% 33%	3463
	21st to end	Day	18% 12% 5% 8% 5% 5% 5% 4 5% 7% 27%	4087
January	1st to 10th	Night	16% 11% 3 8% 4 3 3 3 4 6% 38%	8232
	11th to 20th	Night	15% 10% 3 8% 5% 4 4 2 3 4 42%	8280
	21st to end	Night	18% 11% 4 8% 4 3 3 2 4 4 37%	7932
February	1st to 10th	Night	22% 9% 3 9% 5% 4 3 3 4 5% 32%	2520
	11th to 20th	Night	22% 8% 4 7% 5% 3 4 3 3 5% 35%	2458
	21st to end	Night	20% 9% 4 8% 4 4 3 4 5% 5% 35%	2076
March	1st to 10th	Night	18% 11% 3 7% 4 4 4 3 4 6% 36%	5493
	11th to 20th	Night	11% 6% 2 6% 4 3 4 3 5% 6% 49%	5334
	21st to end	Night	13% 7% 3 8% 5% 5% 4 3 5% 6% 41%	5265
April	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 5% 8% 46%	2100
	11th to 20th	Night	14% 5% 2 5% 3 4 3 4 5% 7% 46%	2075
	21st to end	Night	13% 7% 2 6% 5% 4 4 4 6% 9% 40%	2048
May	1st to 10th	Night	15% 9% 3 8% 4 5% 4 4 5% 7% 35%	5237
	11th to 20th	Night	12% 7% 3 7% 5% 6% 5% 4 6% 7% 37%	5234
	21st to end	Night	16% 9% 3 8% 5% 5% 5% 4 5% 8% 31%	5761
June	1st to 10th	Night	10% 7% 2 6% 4 4 4 3 6% 9% 46%	1778
	11th to 20th	Night	5% 3 2 5% 4 4 4 4 7% 10% 54%	1680
	21st to end	Night	3 3 1 4 4 5% 4 6% 7% 12% 51%	1680
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 5% 4 7% 10% 44%	4708
	11th to 20th	Night	6% 5% 3 7% 5% 5% 6% 5% 8% 12% 40%	4707
	21st to end	Night	7% 6% 3 8% 6% 5% 5% 5% 8% 12% 35%	5674
August	1st to 10th	Night	5% 4 2 5% 4 4 5% 3 6% 7% 54%	4369
	11th to 20th	Night	3 2 1 4 3 3 5% 4 6% 11% 57%	4560
	21st to end	Night	3 3 1 4 3 3 4 3 5% 8% 63%	5046
September	1st to 10th	Night	10% 5% 2 6% 3 3 3 4 5% 7% 52%	2100
	11th to 20th	Night	9% 4 2 6% 4 4 4 4 5% 8% 51%	2305
	21st to end	Night	10% 5% 2 5% 4 3 4 3 5% 6% 53%	2310
October	1st to 10th	Night	9% 5% 1 4 2 3 3 3 4 5% 62%	2310
	11th to 20th	Night	14% 6% 2 5% 3 3 2 3 3 5% 54%	2303
	21st to end	Night	16% 7% 2 5% 3 3 4 2 4 5% 48%	2848
November	1st to 10th	Night	13% 5% 1 4 4 4 4 2 5% 5% 52%	2666
	11th to 20th	Night	13% 7% 2 4 4 3 3 3 5% 7% 49%	2730
	21st to end	Night	16% 9% 3 5% 4 4 3 2 4 6% 46%	2730
December	1st to 10th	Night	19% 10% 3 7% 3 3 3 2 4 4 41%	4380
	11th to 20th	Night	20% 9% 3 6% 4 4 4 3 5% 5% 39%	4952
	21st to end	Night	19% 12% 5% 10% 6% 5% 5% 3 4 5% 26%	7127

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% 3 11% 20% 9% 1	4692
	11th to 20th	Day	41% 3 5% 27% 22% 1	4710
	21st to end	Day	50% 3 7% 21% 14% 5%	6232
February	1st to 10th	Day	51% 4 9% 22% 13% 2	2100
	11th to 20th	Day	53% 3 8% 20% 13% 3	2058
	21st to end	Day	47% 4 9% 19% 15% 5%	1730
March	1st to 10th	Day	52% 3 5% 16% 18% 6%	4580
	11th to 20th	Day	39% 4 8% 24% 19% 5%	4845
	21st to end	Day	41% 5% 10% 28% 15% 1	5950
April	1st to 10th	Day	39% 6% 12% 22% 19% 2	2520
	11th to 20th	Day	41% 5% 9% 23% 19% 3	2494
	21st to end	Day	42% 5% 11% 26% 15% 2	2572
May	1st to 10th	Day	48% 6% 14% 22% 10% 1	7651
	11th to 20th	Day	45% 6% 13% 21% 14% 1	7630
	21st to end	Day	52% 6% 10% 17% 13% 2	8405
June	1st to 10th	Day	37% 9% 11% 23% 18% 3	2836
	11th to 20th	Day	31% 9% 16% 24% 17% 3	2940
	21st to end	Day	30% 10% 16% 24% 17% 4	2940
July	1st to 10th	Day	41% 6% 15% 26% 11% 1	8211
	11th to 20th	Day	41% 9% 20% 24% 6% 1	8205
	21st to end	Day	41% 6% 22% 22% 8% 1	8216
August	1st to 10th	Day	31% 6% 13% 30% 19% 1	5749
	11th to 20th	Day	33% 5% 16% 29% 16% 1	5522
	21st to end	Day	22% 6% 10% 37% 23% 2	6079
September	1st to 10th	Day	38% 8% 10% 21% 20% 4	2504
	11th to 20th	Day	36% 7% 9% 24% 21% 2	2310
	21st to end	Day	35% 6% 10% 22% 23% 5%	2310
October	1st to 10th	Day	21% 3 5% 18% 45% 8%	3700
	11th to 20th	Day	23% 3 7% 25% 30% 11%	3479
	21st to end	Day	31% 3 6% 26% 27% 7%	3190
November	1st to 10th	Day	34% 4 8% 23% 26% 5%	1852
	11th to 20th	Day	37% 5% 8% 23% 22% 6%	1890
	21st to end	Day	43% 4 7% 25% 18% 4	1890
December	1st to 10th	Day	43% 3 7% 27% 19% 1	3020
	11th to 20th	Day	51% 4 8% 19% 15% 2	3460
	21st to end	Day	55% 6% 11% 20% 7%	4087
January	1st to 10th	Night	48% 4 13% 24% 11% 1	8233
	11th to 20th	Night	47% 4 4 21% 21% 3	8280
	21st to end	Night	52% 3 7% 19% 15% 4	7932
February	1st to 10th	Night	55% 4 9% 18% 13% 1	2520
	11th to 20th	Night	53% 4 6% 21% 14% 4	2459
	21st to end	Night	51% 5% 7% 17% 17% 3	2076
March	1st to 10th	Night	49% 4 6% 16% 18% 6%	5493
	11th to 20th	Night	35% 4 9% 22% 19% 11%	5334
	21st to end	Night	44% 4 9% 25% 15% 2	5265
April	1st to 10th	Night	36% 5% 12% 25% 19% 3	2100
	11th to 20th	Night	37% 5% 12% 19% 22% 6%	2075
	21st to end	Night	40% 6% 10% 24% 18% 1	2048
May	1st to 10th	Night	47% 6% 13% 22% 12% 1	5264
	11th to 20th	Night	45% 7% 14% 18% 16% 1	5235
	21st to end	Night	50% 8% 13% 18% 10% 1	5771
June	1st to 10th	Night	35% 6% 13% 25% 18% 3	1778
	11th to 20th	Night	24% 6% 18% 26% 22% 3	1680
	21st to end	Night	25% 9% 17% 29% 14% 6%	1680
July	1st to 10th	Night	34% 7% 16% 28% 14% 1	4670
	11th to 20th	Night	35% 9% 21% 26% 8% 1	4662
	21st to end	Night	41% 6% 22% 23% 8% 1	5546
August	1st to 10th	Night	28% 6% 13% 32% 20% 1	4358
	11th to 20th	Night	22% 6% 20% 36% 16% 1	4590
	21st to end	Night	19% 4 11% 38% 25% 2	5046
September	1st to 10th	Night	31% 7% 9% 25% 22% 5%	2100
	11th to 20th	Night	31% 5% 9% 26% 24% 4	2305
	21st to end	Night	32% 5% 9% 23% 25% 7%	2310
October	1st to 10th	Night	19% 3 5% 18% 44% 12%	3700
	11th to 20th	Night	21% 2 5% 23% 36% 12%	3724
	21st to end	Night	28% 3 7% 23% 27% 11%	4598
November	1st to 10th	Night	34% 4 7% 25% 24% 6%	2666
	11th to 20th	Night	34% 4 7% 24% 22% 7%	2730
	21st to end	Night	42% 4 7% 25% 18% 4	2730
December	1st to 10th	Night	48% 3 7% 21% 20% 1	4380
	11th to 20th	Night	47% 4 8% 22% 17% 2	4954
	21st to end	Night	59% 6% 8% 18% 8% 1	7127

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	22% 16% 32% 21% 7% 1	330
	11th to 20th	Day	26% 21% 34% 15% 4	330
	21st to end	Day	24% 12% 45% 15% 4	363
February	1st to 10th	Day	24% 15% 38% 18% 4 1	330
	11th to 20th	Day	29% 19% 36% 13% 2 1	330
	21st to end	Day	26% 16% 36% 16% 4	273
March	1st to 10th	Day	23% 16% 34% 21% 4 1	330
	11th to 20th	Day	23% 14% 39% 19% 5% 1	425
	21st to end	Day	20% 15% 39% 20% 6% 1	594
April	1st to 10th	Day	18% 13% 29% 27% 11% 1	540
	11th to 20th	Day	17% 14% 27% 27% 12% 3	532
	21st to end	Day	18% 8% 31% 27% 12% 4	540
May	1st to 10th	Day	18% 12% 29% 25% 12% 4	543
	11th to 20th	Day	15% 7% 23% 28% 18% 9%	567
	21st to end	Day	13% 5% 20% 27% 21% 15%	617
June	1st to 10th	Day	12% 4 17% 27% 25% 16%	676
	11th to 20th	Day	7% 4 16% 28% 29% 17%	780
	21st to end	Day	6% 3 16% 31% 28% 16%	780
July	1st to 10th	Day	11% 2 10% 23% 30% 24%	771
	11th to 20th	Day	9% 3 9% 22% 35% 21%	768
	21st to end	Day	10% 2 9% 25% 30% 24%	642
August	1st to 10th	Day	10% 3 7% 26% 34% 22%	566
	11th to 20th	Day	10% 3 10% 28% 34% 15%	559
	21st to end	Day	7% 2 8% 24% 32% 28%	627
September	1st to 10th	Day	13% 2 11% 23% 32% 19%	570
	11th to 20th	Day	10% 2 8% 25% 37% 19%	570
	21st to end	Day	15% 4 18% 24% 26% 12%	570
October	1st to 10th	Day	11% 2 16% 34% 26% 11%	570
	11th to 20th	Day	14% 7% 29% 29% 16% 6%	470
	21st to end	Day	24% 10% 25% 28% 11% 2	363
November	1st to 10th	Day	19% 8% 30% 26% 15% 3	330
	11th to 20th	Day	17% 15% 30% 28% 9% 1	330
	21st to end	Day	22% 11% 32% 21% 12% 2	330
December	1st to 10th	Day	20% 14% 36% 21% 8% 2	330
	11th to 20th	Day	20% 17% 31% 22% 10% 1	330
	21st to end	Day	26% 14% 34% 23% 4	363
January	1st to 10th	Night	21% 15% 33% 27% 5%	1050
	11th to 20th	Night	25% 12% 36% 22% 4	1050
	21st to end	Night	24% 10% 40% 23% 3	944
February	1st to 10th	Night	25% 11% 35% 25% 3	840
	11th to 20th	Night	28% 14% 34% 22% 2	823
	21st to end	Night	25% 12% 37% 23% 2	692
March	1st to 10th	Night	22% 14% 31% 28% 5%	840
	11th to 20th	Night	20% 12% 34% 28% 5% 1	840
	21st to end	Night	19% 10% 34% 30% 7%	782
April	1st to 10th	Night	15% 9% 33% 34% 8%	630
	11th to 20th	Night	17% 7% 33% 30% 12%	623
	21st to end	Night	16% 7% 27% 36% 12% 1	630
May	1st to 10th	Night	16% 5% 30% 31% 15% 3	630
	11th to 20th	Night	13% 5% 22% 36% 20% 4	621
	21st to end	Night	9% 2 16% 39% 29% 5%	683
June	1st to 10th	Night	12% 3 13% 38% 30% 4	630
	11th to 20th	Night	6% 1 10% 43% 37% 3	630
	21st to end	Night	5% 1 11% 40% 38% 6%	630
July	1st to 10th	Night	8% 2 7% 29% 43% 11%	615
	11th to 20th	Night	9% 2 6% 29% 46% 7%	612
	21st to end	Night	8% 1 8% 33% 41% 8%	690
August	1st to 10th	Night	7% 1 4 36% 44% 8%	627
	11th to 20th	Night	6% 1 6% 38% 43% 5%	624
	21st to end	Night	6% 1 7% 31% 46% 8%	693
September	1st to 10th	Night	11% 1 9% 31% 42% 7%	630
	11th to 20th	Night	11% 2 9% 30% 41% 7%	835
	21st to end	Night	12% 2 17% 33% 33% 4	840
October	1st to 10th	Night	12% 3 15% 38% 28% 5%	840
	11th to 20th	Night	17% 5% 21% 36% 19% 2	813
	21st to end	Night	18% 7% 29% 30% 14% 1	880
November	1st to 10th	Night	16% 5% 25% 35% 16% 2	820
	11th to 20th	Night	15% 9% 34% 31% 10% 1	840
	21st to end	Night	20% 10% 28% 31% 10% 1	840
December	1st to 10th	Night	25% 11% 27% 31% 6%	840
	11th to 20th	Night	23% 8% 32% 29% 7%	840
	21st to end	Night	27% 12% 30% 27% 4	1145

Page generated at 2026-10-11 04:06:31. Version ac07

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