Pacheco State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pacheco State Park clear sky chart from 2005-11-06 to 2024-03-28.

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	6% 3 1 3 3 2 3 4 4 7% 63%	78930
	Night	7% 4 2 3 4 2 4 4 5% 8% 58%	81096
Transparency	Day	21% 7% 9% 18% 24% 21%	78648
	Night	23% 8% 11% 18% 21% 18%	80900
Seeing	Day	7% 9% 26% 32% 19% 6%	14520
	Night	7% 4 16% 37% 28% 8%	24070

By Month

Percentage Cloud Cover SW (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	9% 8% 2 6% 6% 4 5% 6% 6% 8% 40%	2635
	11th to 20th	Day	10% 7% 3 8% 8% 5% 6% 5% 5% 7% 35%	2860
	21st to end	Day	18% 8% 3 5% 6% 3 5% 6% 6% 8% 33%	3146
February	1st to 10th	Day	13% 5% 2 5% 4 3 3 5% 5% 6% 48%	1710
	11th to 20th	Day	9% 4 2 5% 4 3 6% 4 5% 8% 50%	1822
	21st to end	Day	11% 4 3 5% 5% 3 4 4 6% 6% 49%	1570
March	1st to 10th	Day	9% 7% 4 5% 5% 4 5% 6% 6% 9% 39%	1985
	11th to 20th	Day	10% 4 2 5% 5% 3 6% 4 7% 9% 44%	2090
	21st to end	Day	8% 4 2 5% 4 3 5% 6% 6% 7% 49%	2329
April	1st to 10th	Day	9% 5% 2 5% 4 3 5% 4 5% 8% 50%	2160
	11th to 20th	Day	6% 3 2 3 4 3 4 3 5% 7% 60%	2129
	21st to end	Day	5% 2 1 3 3 3 3 4 4 7% 66%	2160
May	1st to 10th	Day	2 2 1 2 3 2 4 3 5% 9% 67%	2160
	11th to 20th	Day	3 1 1 2 2 2 3 3 4 9% 69%	2364
	21st to end	Day	2 1 1 2 3 2 3 4 5% 8% 69%	2723
June	1st to 10th	Day	2 1 1 3 1 1 3 3 4 9% 71%	2520
	11th to 20th	Day	1 1 1 1 1 2 2 3 7% 82%	2520
	21st to end	Day	1 1 1 1 1 2 2 2 5% 83%	2520
July	1st to 10th	Day	1 1 1 2 1 2 6% 86%	2520
	11th to 20th	Day	1 1 1 1 1 2 2 4 5% 83%	2412
	21st to end	Day	1 1 1 1 2 2 3 5% 83%	2546
August	1st to 10th	Day	1 1 1 2 1 2 2 2 7% 81%	2322
	11th to 20th	Day	1 1 1 1 1 2 2 6% 86%	2122
	21st to end	Day	1 1 1 1 1 2 3 6% 84%	2376
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2160
	11th to 20th	Day	1 1 1 1 1 2 3 4 6% 80%	2160
	21st to end	Day	1 1 1 1 2 1 2 2 4 5% 81%	1947
October	1st to 10th	Day	2 1 1 2 3 2 3 3 4 6% 74%	1800
	11th to 20th	Day	3 2 1 2 3 2 3 3 4 6% 73%	1800
	21st to end	Day	3 2 1 2 3 2 3 4 4 6% 68%	1980
November	1st to 10th	Day	6% 3 2 3 3 3 5% 4 5% 8% 58%	1772
	11th to 20th	Day	6% 4 2 3 4 2 4 4 5% 8% 58%	1710
	21st to end	Day	8% 4 2 3 3 3 3 4 6% 7% 57%	1658
December	1st to 10th	Day	10% 5% 2 6% 4 3 4 5% 6% 7% 47%	1520
	11th to 20th	Day	20% 10% 4 6% 5% 2 4 4 5% 6% 33%	1928
	21st to end	Day	10% 9% 3 7% 6% 3 5% 6% 5% 8% 37%	2794
January	1st to 10th	Night	10% 7% 2 5% 5% 3 4 5% 5% 6% 48%	4309
	11th to 20th	Night	14% 8% 3 7% 6% 3 6% 5% 5% 7% 36%	4110
	21st to end	Night	15% 7% 3 6% 7% 4 5% 5% 6% 7% 35%	4521
February	1st to 10th	Night	12% 5% 2 4 4 2 4 4 4 6% 52%	2470
	11th to 20th	Night	8% 3 1 3 4 3 5% 5% 6% 9% 52%	2244
	21st to end	Night	9% 4 2 4 4 2 4 4 4 8% 56%	1884
March	1st to 10th	Night	10% 5% 2 6% 6% 4 5% 6% 5% 6% 45%	2190
	11th to 20th	Night	8% 4 1 5% 6% 4 5% 5% 6% 10% 47%	2090
	21st to end	Night	8% 5% 2 3 4 3 4 6% 5% 8% 53%	2180
April	1st to 10th	Night	7% 4 2 4 3 2 5% 6% 5% 7% 54%	1800
	11th to 20th	Night	4 3 2 3 4 2 3 4 6% 7% 62%	1779
	21st to end	Night	3 2 1 2 2 2 3 3 5% 12% 66%	1800
May	1st to 10th	Night	2 2 1 2 3 2 4 4 4 12% 64%	1800
	11th to 20th	Night	3 1 1 1 2 2 4 3 6% 13% 64%	1520
	21st to end	Night	2 2 1 1 1 2 3 4 6% 12% 67%	1552
June	1st to 10th	Night	1 2 1 2 3 2 4 3 5% 11% 67%	1440
	11th to 20th	Night	1 1 1 1 2 2 3 10% 78%	1440
	21st to end	Night	1 1 1 2 1 4 7% 82%	1440
July	1st to 10th	Night	1 1 2 2 3 9% 81%	1440
	11th to 20th	Night	1 1 1 1 1 2 2 4 9% 79%	1543
	21st to end	Night	1 1 1 1 1 3 3 4 9% 75%	1773
August	1st to 10th	Night	1 1 1 2 1 2 3 4 12% 73%	1615
	11th to 20th	Night	1 2 1 2 3 4 9% 77%	1780
	21st to end	Night	1 1 1 2 2 4 8% 80%	1980
September	1st to 10th	Night	1 1 1 1 1 2 2 3 7% 81%	1800
	11th to 20th	Night	2 1 1 2 1 1 2 2 4 9% 77%	1800
	21st to end	Night	2 1 1 2 1 2 3 2 6% 78%	2010
October	1st to 10th	Night	4 2 1 2 2 1 3 3 4 8% 71%	2160
	11th to 20th	Night	3 2 1 2 3 2 3 4 4 9% 68%	2160
	21st to end	Night	3 2 1 1 2 2 3 4 4 7% 70%	2376
November	1st to 10th	Night	5% 2 1 2 3 2 4 4 5% 8% 64%	2305
	11th to 20th	Night	6% 3 2 3 4 2 4 4 5% 10% 57%	2470
	21st to end	Night	6% 3 2 4 4 3 4 4 5% 7% 59%	2517
December	1st to 10th	Night	10% 5% 2 6% 4 3 4 4 5% 7% 50%	2660
	11th to 20th	Night	16% 8% 3 7% 5% 3 5% 5% 6% 7% 35%	3276
	21st to end	Night	14% 7% 2 5% 5% 4 6% 6% 6% 7% 37%	4862

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% 13% 13% 26% 8% 3	2635
	11th to 20th	Day	45% 11% 12% 15% 13% 5%	2860
	21st to end	Day	45% 11% 12% 16% 13% 3	3146
February	1st to 10th	Day	35% 7% 9% 21% 18% 10%	1710
	11th to 20th	Day	31% 9% 12% 20% 22% 7%	1832
	21st to end	Day	34% 9% 10% 22% 20% 6%	1570
March	1st to 10th	Day	39% 11% 12% 18% 17% 4	1985
	11th to 20th	Day	35% 9% 11% 22% 18% 5%	2090
	21st to end	Day	32% 11% 16% 20% 16% 4	2329
April	1st to 10th	Day	32% 8% 12% 21% 19% 7%	2160
	11th to 20th	Day	24% 6% 13% 25% 24% 8%	2132
	21st to end	Day	19% 8% 12% 28% 28% 6%	2160
May	1st to 10th	Day	15% 8% 11% 25% 32% 9%	2160
	11th to 20th	Day	12% 7% 10% 26% 33% 11%	2367
	21st to end	Day	13% 9% 14% 27% 29% 7%	2724
June	1st to 10th	Day	12% 8% 12% 23% 28% 17%	2520
	11th to 20th	Day	5% 4 8% 20% 34% 29%	2520
	21st to end	Day	7% 2 3 10% 30% 47%	2520
July	1st to 10th	Day	4 2 3 9% 22% 61%	2451
	11th to 20th	Day	6% 3 4 9% 22% 56%	2339
	21st to end	Day	5% 2 3 9% 26% 55%	2405
August	1st to 10th	Day	7% 3 4 11% 26% 49%	2306
	11th to 20th	Day	4 2 3 11% 31% 50%	2122
	21st to end	Day	4 2 3 11% 33% 48%	2376
September	1st to 10th	Day	5% 3 3 8% 28% 53%	2160
	11th to 20th	Day	4 5% 7% 19% 38% 26%	2160
	21st to end	Day	8% 3 5% 20% 40% 25%	1947
October	1st to 10th	Day	12% 4 9% 18% 27% 30%	1800
	11th to 20th	Day	14% 5% 8% 21% 25% 27%	1800
	21st to end	Day	16% 4 9% 20% 27% 23%	1980
November	1st to 10th	Day	24% 7% 12% 19% 24% 14%	1772
	11th to 20th	Day	24% 7% 11% 25% 25% 7%	1710
	21st to end	Day	26% 7% 12% 18% 28% 11%	1658
December	1st to 10th	Day	34% 8% 12% 18% 17% 11%	1520
	11th to 20th	Day	49% 9% 9% 15% 13% 5%	1928
	21st to end	Day	41% 11% 14% 20% 11% 3	2794
January	1st to 10th	Night	32% 13% 16% 25% 13% 3	4309
	11th to 20th	Night	43% 12% 13% 15% 10% 7%	4110
	21st to end	Night	43% 13% 11% 15% 13% 5%	4521
February	1st to 10th	Night	32% 7% 9% 20% 21% 11%	2470
	11th to 20th	Night	26% 9% 13% 20% 23% 9%	2245
	21st to end	Night	27% 9% 12% 27% 18% 7%	1884
March	1st to 10th	Night	35% 12% 14% 16% 17% 6%	2190
	11th to 20th	Night	31% 10% 12% 19% 20% 7%	2090
	21st to end	Night	27% 12% 14% 23% 17% 7%	2180
April	1st to 10th	Night	27% 10% 16% 22% 18% 8%	1800
	11th to 20th	Night	21% 8% 14% 26% 22% 9%	1779
	21st to end	Night	14% 10% 15% 27% 27% 7%	1800
May	1st to 10th	Night	15% 9% 12% 22% 29% 14%	1800
	11th to 20th	Night	12% 8% 13% 22% 33% 12%	1520
	21st to end	Night	10% 11% 18% 24% 29% 8%	1552
June	1st to 10th	Night	13% 8% 11% 19% 31% 17%	1440
	11th to 20th	Night	6% 5% 8% 17% 32% 32%	1440
	21st to end	Night	4 4 7% 11% 29% 46%	1440
July	1st to 10th	Night	3 3 6% 9% 19% 60%	1400
	11th to 20th	Night	5% 3 4 11% 23% 53%	1494
	21st to end	Night	6% 3 6% 9% 23% 53%	1674
August	1st to 10th	Night	7% 4 7% 13% 23% 46%	1606
	11th to 20th	Night	6% 3 4 11% 28% 49%	1780
	21st to end	Night	4 3 5% 12% 28% 49%	1980
September	1st to 10th	Night	5% 4 4 7% 22% 58%	1800
	11th to 20th	Night	7% 6% 6% 17% 33% 32%	1800
	21st to end	Night	8% 4 6% 15% 37% 30%	2010
October	1st to 10th	Night	14% 6% 8% 16% 23% 33%	2160
	11th to 20th	Night	13% 7% 8% 19% 25% 29%	2160
	21st to end	Night	12% 6% 7% 21% 27% 26%	2376
November	1st to 10th	Night	17% 8% 11% 21% 24% 18%	2305
	11th to 20th	Night	23% 7% 12% 20% 30% 9%	2470
	21st to end	Night	24% 7% 10% 18% 27% 14%	2517
December	1st to 10th	Night	31% 8% 11% 20% 18% 12%	2660
	11th to 20th	Night	44% 12% 11% 14% 15% 4	3276
	21st to end	Night	40% 14% 14% 17% 11% 4	4862

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% 10% 26% 23% 14% 3	237
	11th to 20th	Day	14% 8% 23% 32% 20% 4	370
	21st to end	Day	13% 9% 23% 31% 21% 4	407
February	1st to 10th	Day	19% 12% 18% 29% 16% 5%	370
	11th to 20th	Day	13% 14% 25% 30% 15% 1	442
	21st to end	Day	13% 13% 27% 31% 15% 2	382
March	1st to 10th	Day	19% 14% 26% 27% 12% 2	460
	11th to 20th	Day	17% 13% 25% 23% 17% 5%	460
	21st to end	Day	16% 14% 31% 27% 10% 2	491
April	1st to 10th	Day	13% 17% 30% 20% 15% 4	420
	11th to 20th	Day	10% 19% 31% 26% 10% 4	412
	21st to end	Day	5% 20% 34% 21% 13% 8%	420
May	1st to 10th	Day	7% 15% 33% 26% 14% 4	423
	11th to 20th	Day	4 16% 37% 27% 12% 4	448
	21st to end	Day	6% 13% 31% 33% 12% 5%	485
June	1st to 10th	Day	3 11% 36% 31% 12% 7%	450
	11th to 20th	Day	2 12% 32% 32% 18% 4	450
	21st to end	Day	2 7% 32% 35% 19% 5%	450
July	1st to 10th	Day	3 30% 44% 18% 5%	446
	11th to 20th	Day	1 1 27% 42% 24% 5%	444
	21st to end	Day	1 1 24% 41% 21% 11%	487
August	1st to 10th	Day	2 5% 32% 39% 17% 5%	447
	11th to 20th	Day	1 4 24% 38% 22% 10%	437
	21st to end	Day	3 21% 42% 23% 11%	495
September	1st to 10th	Day	2 5% 22% 36% 21% 14%	450
	11th to 20th	Day	2 7% 28% 34% 20% 10%	450
	21st to end	Day	3 6% 18% 36% 28% 10%	450
October	1st to 10th	Day	4 8% 22% 30% 26% 11%	450
	11th to 20th	Day	3 7% 20% 28% 30% 11%	450
	21st to end	Day	6% 6% 18% 29% 32% 10%	495
November	1st to 10th	Day	8% 5% 17% 27% 35% 7%	368
	11th to 20th	Day	5% 5% 15% 38% 30% 7%	270
	21st to end	Day	9% 4 22% 35% 29% 2	246
December	1st to 10th	Day	16% 6% 23% 29% 23% 4	180
	11th to 20th	Day	16% 9% 23% 25% 22% 5%	180
	21st to end	Day	17% 9% 26% 26% 19% 3	198
January	1st to 10th	Night	15% 3 11% 36% 25% 9%	760
	11th to 20th	Night	12% 4 11% 38% 27% 8%	760
	21st to end	Night	14% 4 11% 37% 27% 7%	836
February	1st to 10th	Night	16% 4 12% 36% 25% 8%	760
	11th to 20th	Night	10% 6% 16% 37% 24% 7%	744
	21st to end	Night	12% 7% 15% 43% 19% 4	628
March	1st to 10th	Night	14% 9% 17% 35% 21% 5%	760
	11th to 20th	Night	11% 6% 20% 35% 23% 6%	760
	21st to end	Night	10% 10% 22% 35% 19% 4	820
April	1st to 10th	Night	10% 8% 20% 36% 23% 4	720
	11th to 20th	Night	6% 12% 27% 29% 20% 6%	711
	21st to end	Night	5% 9% 28% 29% 23% 6%	720
May	1st to 10th	Night	3 7% 28% 36% 21% 5%	720
	11th to 20th	Night	3 5% 25% 41% 22% 3	458
	21st to end	Night	3 7% 26% 38% 24% 2	389
June	1st to 10th	Night	3 4 27% 40% 24% 3	360
	11th to 20th	Night	1 4 25% 42% 25% 2	360
	21st to end	Night	1 3 19% 43% 31% 4	360
July	1st to 10th	Night	1 2 22% 38% 35% 3	350
	11th to 20th	Night	1 12% 44% 34% 9%	450
	21st to end	Night	1 1 15% 37% 37% 9%	591
August	1st to 10th	Night	1 1 16% 42% 33% 6%	541
	11th to 20th	Night	1 20% 40% 30% 9%	712
	21st to end	Night	1 1 13% 38% 38% 9%	792
September	1st to 10th	Night	1 2 14% 34% 39% 10%	720
	11th to 20th	Night	2 2 18% 38% 31% 9%	720
	21st to end	Night	3 3 12% 36% 35% 12%	720
October	1st to 10th	Night	4 3 13% 38% 33% 11%	720
	11th to 20th	Night	4 3 12% 35% 33% 13%	720
	21st to end	Night	4 2 13% 32% 28% 20%	792
November	1st to 10th	Night	5% 3 12% 34% 33% 12%	740
	11th to 20th	Night	9% 2 9% 37% 34% 9%	760
	21st to end	Night	7% 4 13% 36% 32% 9%	760
December	1st to 10th	Night	13% 4 9% 39% 27% 8%	760
	11th to 20th	Night	16% 4 11% 39% 26% 5%	760
	21st to end	Night	16% 7% 15% 35% 23% 4	836

Page generated at 2024-03-24 20:37:00. Version ac07

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