Pisony Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pisony Ranch clear sky chart from 2005-11-06 to 2024-02-10.

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% 8% 3 6% 6% 3 5% 6% 7% 9% 40%	77787
	Night	5% 7% 4 7% 6% 3 5% 5% 7% 9% 43%	81131
Transparency	Day	38% 9% 17% 23% 12% 2	77501
	Night	35% 9% 19% 23% 11% 2	80997
Seeing	Day	20% 20% 27% 20% 10% 2	14192
	Night	16% 18% 27% 26% 12% 2	23548

By Month

Percentage Cloud Cover NW (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	1 5% 3 11% 10% 4 5% 5% 8% 14% 35%	2219
	11th to 20th	Day	1 8% 5% 10% 7% 5% 7% 6% 7% 9% 33%	2384
	21st to end	Day	1 5% 3 7% 6% 4 6% 7% 8% 10% 42%	2794
February	1st to 10th	Day	3 8% 5% 8% 8% 5% 6% 7% 7% 11% 33%	1526
	11th to 20th	Day	3 10% 5% 8% 8% 4 7% 6% 7% 11% 31%	1575
	21st to end	Day	2 9% 5% 12% 8% 2 7% 5% 7% 9% 34%	1479
March	1st to 10th	Day	2 7% 6% 9% 7% 4 5% 5% 7% 10% 38%	1800
	11th to 20th	Day	4 9% 5% 6% 5% 4 7% 6% 8% 10% 38%	1949
	21st to end	Day	6% 13% 5% 7% 7% 4 6% 5% 7% 10% 30%	2213
April	1st to 10th	Day	6% 12% 4 9% 8% 4 5% 6% 8% 8% 29%	2182
	11th to 20th	Day	9% 14% 5% 8% 6% 4 4 6% 6% 8% 30%	2310
	21st to end	Day	10% 13% 5% 7% 6% 3 5% 5% 6% 7% 33%	2340
May	1st to 10th	Day	11% 13% 4 8% 7% 4 6% 6% 6% 8% 27%	2385
	11th to 20th	Day	14% 10% 3 6% 5% 4 6% 5% 6% 8% 32%	2622
	21st to end	Day	23% 9% 4 6% 5% 3 5% 5% 5% 8% 26%	2917
June	1st to 10th	Day	14% 9% 4 7% 6% 4 7% 6% 7% 7% 30%	2700
	11th to 20th	Day	17% 7% 4 7% 7% 4 6% 6% 7% 7% 27%	2700
	21st to end	Day	7% 4 2 5% 6% 4 6% 6% 6% 9% 44%	2700
July	1st to 10th	Day	7% 4 2 4 5% 3 6% 6% 7% 9% 47%	2700
	11th to 20th	Day	7% 3 2 4 5% 3 5% 6% 6% 7% 53%	2700
	21st to end	Day	4 2 1 3 3 3 5% 4 5% 8% 61%	2786
August	1st to 10th	Day	10% 3 1 3 4 3 5% 5% 6% 8% 51%	2507
	11th to 20th	Day	7% 3 2 4 3 2 4 5% 7% 9% 54%	2300
	21st to end	Day	8% 4 2 4 5% 3 5% 5% 6% 8% 51%	2574
September	1st to 10th	Day	12% 6% 2 3 4 2 4 4 6% 7% 49%	2199
	11th to 20th	Day	11% 6% 2 4 4 2 5% 4 6% 9% 47%	1980
	21st to end	Day	10% 7% 2 3 4 2 4 5% 6% 9% 48%	1980
October	1st to 10th	Day	10% 10% 4 6% 6% 3 5% 5% 5% 7% 40%	1924
	11th to 20th	Day	5% 8% 3 6% 6% 3 6% 5% 6% 8% 44%	1670
	21st to end	Day	4 11% 3 8% 5% 3 5% 5% 6% 11% 39%	1782
November	1st to 10th	Day	6% 11% 4 6% 5% 3 4 6% 8% 9% 37%	1614
	11th to 20th	Day	2 7% 3 6% 4 2 5% 7% 8% 10% 46%	1492
	21st to end	Day	3 8% 5% 9% 6% 3 4 4 7% 10% 41%	1330
December	1st to 10th	Day	2 5% 3 8% 6% 3 6% 6% 8% 10% 43%	1330
	11th to 20th	Day	2 7% 3 10% 7% 2 5% 7% 7% 12% 38%	1682
	21st to end	Day	1 7% 3 5% 6% 3 5% 5% 8% 12% 44%	2442
January	1st to 10th	Night	2 6% 5% 9% 7% 4 5% 7% 9% 11% 35%	4726
	11th to 20th	Night	1 7% 4 9% 8% 4 6% 8% 7% 10% 35%	4542
	21st to end	Night	1 8% 4 7% 6% 4 6% 6% 7% 12% 40%	4862
February	1st to 10th	Night	3 10% 5% 8% 9% 4 5% 5% 6% 9% 35%	2638
	11th to 20th	Night	1 11% 5% 8% 7% 4 6% 5% 8% 10% 36%	2272
	21st to end	Night	1 7% 5% 12% 7% 5% 6% 6% 5% 7% 38%	1776
March	1st to 10th	Night	2 8% 4 11% 8% 3 4 6% 6% 10% 40%	2160
	11th to 20th	Night	4 6% 4 7% 5% 3 5% 5% 7% 10% 44%	2009
	21st to end	Night	5% 8% 5% 10% 6% 3 4 5% 8% 10% 36%	2142
April	1st to 10th	Night	7% 9% 5% 8% 6% 3 5% 6% 5% 8% 38%	1777
	11th to 20th	Night	8% 11% 4 8% 5% 2 4 4 7% 9% 37%	1601
	21st to end	Night	7% 12% 5% 6% 6% 4 5% 5% 5% 8% 37%	1620
May	1st to 10th	Night	9% 10% 3 7% 6% 4 5% 6% 5% 8% 38%	1571
	11th to 20th	Night	12% 8% 2 4 5% 3 4 4 8% 9% 42%	1271
	21st to end	Night	21% 7% 3 5% 4 4 6% 4 5% 7% 34%	1358
June	1st to 10th	Night	11% 6% 2 6% 5% 3 6% 5% 7% 9% 38%	1260
	11th to 20th	Night	17% 7% 3 5% 4 4 6% 7% 5% 8% 34%	1260
	21st to end	Night	5% 4 2 4 4 3 5% 6% 6% 9% 52%	1260
July	1st to 10th	Night	7% 3 2 4 3 2 4 4 6% 9% 56%	1260
	11th to 20th	Night	4 4 1 3 4 2 5% 3 5% 7% 61%	1260
	21st to end	Night	5% 2 1 2 3 2 3 5% 4 6% 66%	1528
August	1st to 10th	Night	7% 4 2 4 4 3 3 4 6% 6% 58%	1432
	11th to 20th	Night	7% 3 1 3 2 2 4 6% 6% 9% 57%	1599
	21st to end	Night	8% 4 2 4 3 2 4 4 5% 7% 57%	1782
September	1st to 10th	Night	10% 4 2 4 4 2 3 3 4 8% 56%	1759
	11th to 20th	Night	12% 7% 1 4 2 2 3 4 6% 8% 51%	1980
	21st to end	Night	10% 6% 2 4 4 2 4 4 5% 9% 50%	1980
October	1st to 10th	Night	10% 8% 2 4 5% 2 4 5% 5% 8% 48%	2035
	11th to 20th	Night	5% 6% 2 4 4 4 5% 5% 7% 10% 48%	2286
	21st to end	Night	5% 9% 4 7% 5% 4 5% 5% 7% 10% 40%	2574
November	1st to 10th	Night	5% 11% 4 7% 6% 3 5% 6% 6% 8% 40%	2444
	11th to 20th	Night	1 7% 3 5% 5% 3 5% 5% 7% 11% 47%	2683
	21st to end	Night	2 7% 5% 7% 5% 3 5% 5% 7% 11% 42%	2850
December	1st to 10th	Night	1 6% 4 9% 6% 3 5% 6% 7% 11% 40%	2850
	11th to 20th	Night	2 7% 4 8% 8% 4 6% 8% 8% 11% 35%	3510
	21st to end	Night	1 7% 4 8% 7% 4 6% 5% 7% 8% 43%	5214

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	37% 10% 22% 20% 10% 2	2219
	11th to 20th	Day	43% 9% 18% 13% 12% 5%	2408
	21st to end	Day	32% 10% 26% 26% 6% 1	2794
February	1st to 10th	Day	43% 9% 19% 20% 7% 2	1526
	11th to 20th	Day	43% 10% 19% 19% 8% 1	1584
	21st to end	Day	44% 8% 15% 22% 9% 2	1479
March	1st to 10th	Day	39% 10% 19% 23% 9% 1	1800
	11th to 20th	Day	36% 11% 19% 23% 10% 1	1950
	21st to end	Day	46% 10% 20% 18% 6%	2213
April	1st to 10th	Day	45% 11% 18% 20% 7%	2182
	11th to 20th	Day	48% 9% 15% 19% 8% 1	2310
	21st to end	Day	47% 7% 17% 20% 8% 1	2340
May	1st to 10th	Day	51% 8% 15% 18% 7%	2385
	11th to 20th	Day	46% 8% 15% 22% 8% 1	2626
	21st to end	Day	54% 9% 15% 14% 7%	2918
June	1st to 10th	Day	48% 9% 15% 19% 8% 1	2700
	11th to 20th	Day	51% 8% 12% 17% 10% 1	2700
	21st to end	Day	32% 9% 16% 26% 14% 2	2700
July	1st to 10th	Day	28% 9% 15% 28% 15% 5%	2626
	11th to 20th	Day	28% 7% 13% 26% 22% 5%	2619
	21st to end	Day	20% 7% 11% 29% 26% 7%	2631
August	1st to 10th	Day	28% 8% 14% 26% 18% 7%	2490
	11th to 20th	Day	24% 6% 17% 33% 16% 3	2300
	21st to end	Day	27% 8% 12% 28% 21% 4	2574
September	1st to 10th	Day	32% 6% 12% 27% 17% 5%	2199
	11th to 20th	Day	31% 7% 13% 29% 17% 3	1980
	21st to end	Day	32% 8% 16% 31% 11% 2	1980
October	1st to 10th	Day	40% 8% 16% 23% 11% 1	1924
	11th to 20th	Day	36% 9% 18% 24% 13% 1	1670
	21st to end	Day	38% 9% 19% 22% 10% 1	1782
November	1st to 10th	Day	39% 12% 17% 21% 10% 1	1614
	11th to 20th	Day	29% 13% 23% 24% 10% 1	1492
	21st to end	Day	38% 8% 25% 18% 8% 3	1330
December	1st to 10th	Day	34% 10% 25% 19% 9% 2	1330
	11th to 20th	Day	35% 12% 25% 21% 6%	1684
	21st to end	Day	29% 9% 19% 23% 16% 4	2442
January	1st to 10th	Night	36% 13% 20% 22% 7% 2	4726
	11th to 20th	Night	44% 8% 17% 15% 10% 7%	4580
	21st to end	Night	33% 10% 25% 24% 7% 1	4862
February	1st to 10th	Night	44% 8% 16% 19% 11% 2	2638
	11th to 20th	Night	40% 9% 21% 21% 8%	2273
	21st to end	Night	43% 8% 13% 24% 10% 2	1776
March	1st to 10th	Night	39% 9% 22% 21% 8%	2160
	11th to 20th	Night	34% 9% 23% 21% 11% 1	2009
	21st to end	Night	40% 11% 21% 21% 7% 1	2142
April	1st to 10th	Night	42% 9% 17% 22% 9% 1	1777
	11th to 20th	Night	42% 8% 15% 27% 7%	1601
	21st to end	Night	43% 8% 14% 26% 8% 1	1620
May	1st to 10th	Night	41% 10% 18% 23% 9%	1571
	11th to 20th	Night	36% 7% 17% 30% 10% 1	1271
	21st to end	Night	48% 8% 17% 19% 8% 1	1358
June	1st to 10th	Night	40% 7% 19% 24% 9% 1	1260
	11th to 20th	Night	43% 9% 18% 19% 10%	1260
	21st to end	Night	25% 9% 20% 29% 15% 2	1260
July	1st to 10th	Night	22% 7% 19% 35% 13% 3	1225
	11th to 20th	Night	22% 7% 15% 27% 23% 6%	1218
	21st to end	Night	18% 6% 12% 31% 26% 7%	1443
August	1st to 10th	Night	25% 6% 14% 29% 20% 5%	1424
	11th to 20th	Night	21% 7% 18% 33% 19% 3	1599
	21st to end	Night	25% 5% 12% 32% 24% 3	1782
September	1st to 10th	Night	26% 6% 15% 32% 16% 6%	1759
	11th to 20th	Night	29% 7% 15% 29% 16% 3	1980
	21st to end	Night	31% 7% 18% 27% 13% 3	1980
October	1st to 10th	Night	35% 7% 17% 26% 14% 1	2035
	11th to 20th	Night	29% 8% 18% 29% 13% 3	2286
	21st to end	Night	38% 10% 17% 25% 10%	2574
November	1st to 10th	Night	40% 10% 18% 20% 9% 1	2444
	11th to 20th	Night	29% 12% 22% 24% 12% 1	2683
	21st to end	Night	35% 11% 23% 19% 10% 3	2850
December	1st to 10th	Night	36% 9% 22% 20% 10% 3	2850
	11th to 20th	Night	38% 13% 24% 19% 6%	3507
	21st to end	Night	34% 9% 20% 19% 13% 5%	5214

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	19% 22% 28% 17% 6% 7%	180
	11th to 20th	Day	21% 14% 32% 25% 7% 2	180
	21st to end	Day	16% 29% 36% 10% 7% 3	198
February	1st to 10th	Day	22% 20% 36% 16% 4 1	184
	11th to 20th	Day	17% 23% 35% 18% 6% 1	240
	21st to end	Day	19% 25% 36% 15% 6% 1	345
March	1st to 10th	Day	21% 29% 29% 14% 5% 2	420
	11th to 20th	Day	22% 25% 25% 17% 9% 2	420
	21st to end	Day	27% 28% 24% 13% 6% 2	462
April	1st to 10th	Day	22% 26% 30% 17% 5%	420
	11th to 20th	Day	25% 24% 29% 15% 6% 2	412
	21st to end	Day	27% 23% 25% 16% 7% 2	420
May	1st to 10th	Day	23% 18% 25% 19% 12% 3	423
	11th to 20th	Day	26% 15% 19% 23% 13% 4	593
	21st to end	Day	27% 12% 19% 25% 14% 3	679
June	1st to 10th	Day	22% 20% 22% 23% 10% 3	630
	11th to 20th	Day	27% 20% 22% 20% 9% 2	630
	21st to end	Day	13% 14% 27% 26% 16% 4	630
July	1st to 10th	Day	11% 14% 25% 28% 19% 3	621
	11th to 20th	Day	14% 17% 27% 27% 15% 1	618
	21st to end	Day	8% 15% 34% 27% 13% 3	532
August	1st to 10th	Day	13% 16% 28% 29% 10% 4	447
	11th to 20th	Day	10% 13% 35% 26% 11% 4	437
	21st to end	Day	13% 18% 33% 22% 11% 2	495
September	1st to 10th	Day	21% 22% 26% 21% 8% 2	450
	11th to 20th	Day	20% 15% 31% 20% 11% 2	450
	21st to end	Day	27% 22% 28% 14% 6% 2	450
October	1st to 10th	Day	22% 21% 27% 19% 9% 2	394
	11th to 20th	Day	24% 19% 24% 20% 11% 2	270
	21st to end	Day	28% 21% 28% 15% 7% 2	297
November	1st to 10th	Day	28% 27% 23% 18% 4 1	270
	11th to 20th	Day	29% 25% 32% 11% 3	257
	21st to end	Day	26% 22% 26% 14% 7% 6%	180
December	1st to 10th	Day	21% 26% 23% 18% 10% 2	180
	11th to 20th	Day	24% 22% 32% 17% 4 1	180
	21st to end	Day	16% 20% 36% 16% 10% 3	198
January	1st to 10th	Night	20% 22% 31% 21% 5% 1	950
	11th to 20th	Night	13% 22% 36% 22% 5% 1	855
	21st to end	Night	11% 26% 33% 22% 7% 2	836
February	1st to 10th	Night	16% 16% 33% 23% 10% 3	758
	11th to 20th	Night	15% 17% 33% 27% 7% 1	704
	21st to end	Night	11% 16% 33% 26% 13% 1	592
March	1st to 10th	Night	12% 20% 35% 21% 10% 1	720
	11th to 20th	Night	16% 20% 27% 26% 10% 1	720
	21st to end	Night	18% 17% 23% 30% 9% 3	792
April	1st to 10th	Night	14% 20% 27% 25% 11% 2	697
	11th to 20th	Night	16% 23% 24% 25% 12% 1	533
	21st to end	Night	18% 16% 27% 26% 11% 1	540
May	1st to 10th	Night	21% 13% 22% 27% 16% 1	491
	11th to 20th	Night	20% 8% 16% 29% 25% 3	354
	21st to end	Night	26% 8% 15% 30% 19% 2	389
June	1st to 10th	Night	18% 14% 20% 31% 14% 3	360
	11th to 20th	Night	24% 14% 21% 25% 16% 1	360
	21st to end	Night	9% 11% 19% 38% 22% 1	360
July	1st to 10th	Night	10% 8% 16% 37% 29%	350
	11th to 20th	Night	8% 7% 21% 44% 18% 1	348
	21st to end	Night	8% 7% 17% 42% 24% 2	394
August	1st to 10th	Night	9% 6% 13% 41% 30% 2	358
	11th to 20th	Night	9% 6% 20% 36% 25% 3	531
	21st to end	Night	12% 10% 23% 35% 18% 3	594
September	1st to 10th	Night	14% 10% 19% 33% 21% 4	666
	11th to 20th	Night	17% 10% 19% 28% 19% 5%	720
	21st to end	Night	18% 15% 26% 24% 14% 3	720
October	1st to 10th	Night	21% 12% 18% 33% 15% 2	720
	11th to 20th	Night	15% 19% 23% 28% 14% 1	720
	21st to end	Night	17% 22% 28% 23% 8% 2	792
November	1st to 10th	Night	21% 24% 26% 23% 5% 1	779
	11th to 20th	Night	21% 27% 30% 18% 3 1	950
	21st to end	Night	16% 23% 35% 18% 7% 1	950
December	1st to 10th	Night	14% 21% 31% 25% 9% 1	950
	11th to 20th	Night	15% 22% 36% 23% 4 1	950
	21st to end	Night	14% 22% 33% 23% 7% 1	1045

Page generated at 2024-02-07 04:11:59. Version ac07

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