Parkfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parkfield clear sky chart from 2005-11-06 to 2024-11-08.

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	4 3 1 3 3 3 3 3 4 5% 69%	104859
	Night	5% 4 1 4 3 3 3 2 4 5% 67%	102989
Transparency	Day	18% 3 6% 18% 27% 28%	104613
	Night	20% 3 8% 18% 25% 26%	102825
Seeing	Day	7% 6% 20% 32% 25% 10%	15496
	Night	7% 3 10% 35% 36% 9%	25027

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	7% 6% 2 6% 4 4 5% 4 6% 5% 52%	2633
	11th to 20th	Day	8% 6% 2 8% 5% 5% 5% 5% 6% 8% 41%	2860
	21st to end	Day	13% 8% 3 7% 4 5% 5% 4 5% 8% 37%	3146
February	1st to 10th	Day	13% 7% 2 3 3 3 4 4 4 6% 52%	1776
	11th to 20th	Day	7% 7% 3 5% 4 4 4 4 5% 7% 51%	1850
	21st to end	Day	11% 8% 2 6% 4 3 4 4 5% 7% 46%	1570
March	1st to 10th	Day	7% 8% 4 9% 5% 6% 6% 5% 7% 7% 36%	3195
	11th to 20th	Day	5% 5% 2 4 4 4 4 3 5% 7% 59%	3490
	21st to end	Day	7% 8% 3 8% 5% 6% 6% 5% 5% 7% 41%	4010
April	1st to 10th	Day	7% 7% 2 5% 4 3 3 3 5% 7% 54%	2280
	11th to 20th	Day	5% 5% 2 4 3 3 4 3 5% 7% 58%	2249
	21st to end	Day	4 3 1 3 3 4 4 3 5% 6% 64%	2280
May	1st to 10th	Day	2 2 1 3 2 2 2 2 3 5% 76%	3800
	11th to 20th	Day	1 1 1 1 2 2 2 2 4 5% 79%	3998
	21st to end	Day	2 1 1 2 2 1 2 2 3 4 81%	4813
June	1st to 10th	Day	2 2 1 3 2 2 3 3 5% 7% 71%	2660
	11th to 20th	Day	1 1 1 1 1 1 1 2 4 87%	2660
	21st to end	Day	1 1 1 1 1 2 2 3 87%	2660
July	1st to 10th	Day	1 1 2 93%	4420
	11th to 20th	Day	1 1 1 2 2 1 2 2 2 3 83%	4238
	21st to end	Day	1 1 1 1 1 2 1 2 3 87%	4455
August	1st to 10th	Day	1 1 1 1 1 2 1 3 4 85%	3917
	11th to 20th	Day	1 1 1 1 1 1 1 1 93%	3724
	21st to end	Day	1 1 1 1 1 1 1 3 90%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 3 89%	2280
	11th to 20th	Day	1 1 1 2 3 2 1 2 3 83%	2267
	21st to end	Day	1 2 1 1 2 1 3 2 3 4 80%	2090
October	1st to 10th	Day	1 1 1 2 2 2 2 3 5% 5% 76%	3194
	11th to 20th	Day	1 2 1 3 2 2 3 2 4 4 78%	3161
	21st to end	Day	3 4 2 4 2 2 3 3 5% 6% 66%	3448
November	1st to 10th	Day	3 4 1 5% 3 3 3 4 5% 7% 62%	1818
	11th to 20th	Day	5% 5% 2 4 3 3 4 3 4 7% 61%	1710
	21st to end	Day	5% 5% 2 4 4 4 4 4 5% 5% 59%	1710
December	1st to 10th	Day	7% 6% 3 6% 4 3 4 3 6% 8% 50%	1595
	11th to 20th	Day	17% 11% 3 8% 4 3 4 3 5% 6% 35%	1928
	21st to end	Day	10% 8% 3 7% 5% 5% 5% 4 6% 8% 38%	2794
January	1st to 10th	Night	7% 7% 2 6% 4 4 4 4 5% 6% 51%	4312
	11th to 20th	Night	9% 8% 3 8% 5% 5% 5% 4 6% 8% 41%	4110
	21st to end	Night	13% 6% 2 7% 5% 5% 5% 4 5% 8% 41%	4521
February	1st to 10th	Night	11% 6% 2 5% 3 4 3 3 5% 5% 53%	2403
	11th to 20th	Night	6% 5% 2 5% 3 3 4 3 5% 8% 57%	2218
	21st to end	Night	7% 6% 3 5% 4 3 4 2 5% 6% 55%	1884
March	1st to 10th	Night	7% 10% 4 8% 5% 5% 5% 4 5% 8% 40%	3674
	11th to 20th	Night	4 4 2 4 3 3 4 3 4 6% 63%	3490
	21st to end	Night	9% 7% 3 7% 5% 4 3 3 5% 6% 47%	3643
April	1st to 10th	Night	4 4 2 5% 3 3 4 3 5% 6% 60%	1900
	11th to 20th	Night	3 3 1 4 3 3 3 3 3 6% 68%	1879
	21st to end	Night	2 2 1 2 2 3 4 4 5% 6% 69%	1900
May	1st to 10th	Night	1 1 2 1 1 2 2 3 4 82%	3180
	11th to 20th	Night	2 1 1 1 1 3 3 4 7% 77%	2885
	21st to end	Night	1 1 1 1 1 1 1 2 2 3 85%	2762
June	1st to 10th	Night	2 2 1 2 2 2 2 3 4 5% 77%	1520
	11th to 20th	Night	1 1 1 1 2 2 3 88%	1520
	21st to end	Night	1 1 1 2 3 90%	1520
July	1st to 10th	Night	1 1 2 2 93%	2540
	11th to 20th	Night	1 1 1 1 1 1 1 2 3 88%	2722
	21st to end	Night	1 1 1 1 1 1 1 1 3 3 87%	3109
August	1st to 10th	Night	1 1 2 1 2 1 3 3 86%	3025
	11th to 20th	Night	1 1 1 1 2 2 91%	3126
	21st to end	Night	1 1 1 1 1 2 92%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 2 88%	1900
	11th to 20th	Night	1 1 2 1 1 2 1 3 3 85%	1911
	21st to end	Night	1 1 1 2 1 2 2 2 3 84%	2090
October	1st to 10th	Night	2 1 1 2 2 1 2 1 3 4 81%	3769
	11th to 20th	Night	1 2 1 2 2 2 2 2 3 4 79%	3777
	21st to end	Night	3 3 1 3 2 2 2 2 3 5% 74%	4121
November	1st to 10th	Night	2 4 1 4 3 3 3 2 5% 6% 68%	2419
	11th to 20th	Night	4 3 2 5% 3 3 3 3 5% 7% 63%	2470
	21st to end	Night	4 4 2 5% 4 3 4 4 6% 7% 56%	2470
December	1st to 10th	Night	8% 5% 2 5% 4 4 4 3 5% 8% 52%	2583
	11th to 20th	Night	17% 10% 3 6% 5% 4 5% 3 5% 7% 36%	3276
	21st to end	Night	10% 7% 3 8% 6% 5% 5% 4 6% 8% 39%	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	29% 7% 14% 31% 15% 4	2633
	11th to 20th	Day	40% 4 12% 20% 15% 9%	2860
	21st to end	Day	43% 6% 13% 17% 15% 6%	3146
February	1st to 10th	Day	33% 3 7% 20% 23% 14%	1776
	11th to 20th	Day	32% 5% 7% 23% 24% 10%	1860
	21st to end	Day	36% 5% 10% 20% 23% 6%	1570
March	1st to 10th	Day	39% 9% 13% 19% 16% 5%	3195
	11th to 20th	Day	24% 5% 9% 34% 18% 10%	3490
	21st to end	Day	36% 9% 11% 24% 16% 4	4010
April	1st to 10th	Day	29% 4 10% 26% 20% 10%	2280
	11th to 20th	Day	25% 5% 10% 28% 24% 9%	2252
	21st to end	Day	21% 4 9% 28% 30% 8%	2280
May	1st to 10th	Day	13% 2 7% 23% 34% 22%	3800
	11th to 20th	Day	9% 2 7% 24% 41% 16%	4001
	21st to end	Day	9% 3 5% 28% 47% 8%	4814
June	1st to 10th	Day	13% 2 10% 21% 36% 18%	2660
	11th to 20th	Day	6% 2 4 15% 42% 32%	2660
	21st to end	Day	6% 1 2 10% 33% 48%	2660
July	1st to 10th	Day	2 1 1 5% 17% 75%	4351
	11th to 20th	Day	9% 2 2 5% 18% 65%	4164
	21st to end	Day	6% 2 1 8% 28% 54%	4315
August	1st to 10th	Day	7% 1 1 9% 36% 47%	3902
	11th to 20th	Day	3 1 7% 28% 60%	3760
	21st to end	Day	5% 1 1 11% 25% 58%	4179
September	1st to 10th	Day	5% 2 2 10% 30% 52%	2280
	11th to 20th	Day	8% 2 2 19% 42% 28%	2267
	21st to end	Day	10% 3 2 17% 38% 31%	2090
October	1st to 10th	Day	11% 2 3 11% 22% 50%	3194
	11th to 20th	Day	13% 2 5% 20% 33% 27%	3161
	21st to end	Day	19% 2 3 14% 36% 27%	3448
November	1st to 10th	Day	21% 4 8% 20% 29% 18%	1818
	11th to 20th	Day	24% 4 10% 21% 26% 15%	1710
	21st to end	Day	26% 4 7% 17% 27% 20%	1710
December	1st to 10th	Day	31% 5% 10% 18% 22% 14%	1595
	11th to 20th	Day	49% 4 7% 16% 14% 8%	1928
	21st to end	Day	41% 6% 10% 25% 13% 5%	2794
January	1st to 10th	Night	31% 6% 14% 27% 18% 4	4312
	11th to 20th	Night	39% 5% 14% 22% 12% 9%	4110
	21st to end	Night	39% 5% 13% 20% 16% 7%	4521
February	1st to 10th	Night	33% 4 7% 19% 24% 13%	2403
	11th to 20th	Night	25% 5% 9% 23% 28% 11%	2219
	21st to end	Night	30% 4 9% 24% 26% 7%	1884
March	1st to 10th	Night	40% 6% 12% 22% 16% 5%	3674
	11th to 20th	Night	20% 6% 11% 30% 23% 10%	3490
	21st to end	Night	33% 7% 15% 23% 17% 5%	3643
April	1st to 10th	Night	24% 4 14% 27% 19% 12%	1900
	11th to 20th	Night	18% 4 13% 27% 27% 11%	1879
	21st to end	Night	16% 3 10% 29% 32% 9%	1900
May	1st to 10th	Night	9% 2 8% 29% 28% 25%	3180
	11th to 20th	Night	8% 1 10% 25% 38% 18%	2886
	21st to end	Night	7% 2 7% 26% 44% 14%	2762
June	1st to 10th	Night	11% 2 10% 20% 36% 20%	1520
	11th to 20th	Night	5% 1 4 15% 40% 34%	1520
	21st to end	Night	4 1 1 10% 33% 51%	1520
July	1st to 10th	Night	2 1 4 16% 76%	2500
	11th to 20th	Night	5% 1 1 4 17% 71%	2673
	21st to end	Night	5% 2 1 6% 28% 58%	3011
August	1st to 10th	Night	7% 1 1 10% 28% 53%	3016
	11th to 20th	Night	3 1 1 4 25% 66%	3156
	21st to end	Night	4 1 1 7% 27% 60%	3498
September	1st to 10th	Night	6% 2 2 7% 26% 58%	1900
	11th to 20th	Night	7% 1 3 15% 36% 38%	1911
	21st to end	Night	7% 2 2 15% 41% 33%	2090
October	1st to 10th	Night	9% 2 3 10% 21% 54%	3769
	11th to 20th	Night	12% 2 4 20% 38% 25%	3777
	21st to end	Night	15% 1 2 14% 41% 26%	4121
November	1st to 10th	Night	18% 3 7% 21% 31% 21%	2419
	11th to 20th	Night	21% 3 11% 21% 27% 18%	2470
	21st to end	Night	25% 4 9% 17% 26% 18%	2470
December	1st to 10th	Night	30% 4 9% 17% 23% 16%	2583
	11th to 20th	Night	48% 5% 9% 15% 15% 8%	3276
	21st to end	Night	41% 6% 13% 20% 14% 5%	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	20% 7% 32% 26% 11% 3	235
	11th to 20th	Day	15% 6% 27% 33% 17% 3	370
	21st to end	Day	13% 7% 28% 30% 20% 3	407
February	1st to 10th	Day	17% 10% 24% 27% 17% 5%	401
	11th to 20th	Day	13% 12% 26% 31% 16% 3	455
	21st to end	Day	16% 12% 26% 33% 12% 2	382
March	1st to 10th	Day	16% 13% 25% 29% 15% 1	460
	11th to 20th	Day	15% 10% 26% 28% 17% 4	460
	21st to end	Day	15% 16% 25% 27% 15% 2	506
April	1st to 10th	Day	13% 10% 24% 27% 19% 6%	460
	11th to 20th	Day	9% 14% 23% 28% 19% 6%	452
	21st to end	Day	4 10% 27% 33% 18% 9%	460
May	1st to 10th	Day	7% 7% 26% 36% 17% 6%	463
	11th to 20th	Day	3 10% 21% 32% 24% 9%	488
	21st to end	Day	5% 10% 20% 30% 23% 12%	529
June	1st to 10th	Day	2 6% 17% 34% 26% 14%	490
	11th to 20th	Day	1 6% 19% 37% 29% 9%	490
	21st to end	Day	1 3 18% 33% 29% 17%	490
July	1st to 10th	Day	1 1 13% 39% 30% 17%	486
	11th to 20th	Day	2 8% 34% 33% 23%	484
	21st to end	Day	1 1 10% 31% 36% 21%	531
August	1st to 10th	Day	1 2 14% 38% 28% 17%	487
	11th to 20th	Day	1 1 13% 31% 34% 20%	477
	21st to end	Day	1 1 8% 31% 35% 23%	539
September	1st to 10th	Day	1 2 13% 28% 35% 21%	490
	11th to 20th	Day	2 3 17% 32% 34% 11%	490
	21st to end	Day	2 4 13% 32% 39% 11%	490
October	1st to 10th	Day	3 4 17% 36% 31% 9%	490
	11th to 20th	Day	3 6% 19% 34% 30% 9%	490
	21st to end	Day	6% 4 19% 33% 31% 8%	539
November	1st to 10th	Day	6% 5% 19% 36% 30% 4	372
	11th to 20th	Day	6% 5% 19% 39% 23% 9%	270
	21st to end	Day	7% 6% 23% 38% 23% 4	270
December	1st to 10th	Day	14% 4 25% 37% 18% 2	215
	11th to 20th	Day	11% 9% 27% 29% 19% 5%	180
	21st to end	Day	18% 8% 25% 30% 14% 5%	198
January	1st to 10th	Night	16% 3 10% 38% 25% 7%	760
	11th to 20th	Night	10% 3 11% 41% 28% 7%	760
	21st to end	Night	13% 5% 11% 39% 26% 6%	836
February	1st to 10th	Night	15% 5% 11% 35% 27% 7%	760
	11th to 20th	Night	11% 4 14% 35% 28% 7%	744
	21st to end	Night	12% 6% 14% 45% 19% 3	628
March	1st to 10th	Night	15% 6% 14% 38% 23% 5%	760
	11th to 20th	Night	11% 3 15% 37% 29% 6%	760
	21st to end	Night	11% 8% 16% 35% 26% 5%	836
April	1st to 10th	Night	5% 8% 14% 41% 28% 4	760
	11th to 20th	Night	5% 8% 17% 33% 30% 6%	751
	21st to end	Night	4 6% 19% 35% 29% 7%	760
May	1st to 10th	Night	3 4 14% 42% 28% 8%	760
	11th to 20th	Night	4 4 16% 37% 33% 7%	600
	21st to end	Night	3 5% 13% 38% 34% 6%	411
June	1st to 10th	Night	3 2 11% 38% 42% 3	380
	11th to 20th	Night	1 2 12% 41% 40% 5%	380
	21st to end	Night	1 1 9% 33% 50% 6%	380
July	1st to 10th	Night	1 2 28% 58% 11%	370
	11th to 20th	Night	1 1 22% 56% 19%	471
	21st to end	Night	1 1 1 17% 58% 21%	624
August	1st to 10th	Night	2 1 5% 26% 52% 15%	666
	11th to 20th	Night	1 1 5% 23% 58% 13%	752
	21st to end	Night	1 3 21% 56% 18%	836
September	1st to 10th	Night	1 1 4 23% 54% 17%	760
	11th to 20th	Night	2 1 7% 32% 44% 14%	760
	21st to end	Night	1 2 8% 28% 49% 13%	760
October	1st to 10th	Night	3 3 6% 36% 39% 13%	760
	11th to 20th	Night	5% 2 7% 36% 38% 11%	760
	21st to end	Night	5% 2 8% 35% 38% 13%	836
November	1st to 10th	Night	4 3 12% 35% 36% 11%	770
	11th to 20th	Night	6% 2 9% 41% 35% 7%	760
	21st to end	Night	5% 3 10% 41% 32% 9%	760
December	1st to 10th	Night	12% 3 10% 40% 30% 5%	760
	11th to 20th	Night	16% 4 9% 42% 24% 5%	760
	21st to end	Night	13% 6% 15% 39% 22% 5%	836

Page generated at 2024-11-05 05:15:51. Version ac07

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