Mariposa Fairgrounds
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mariposa Fairgrounds clear sky chart from 2005-11-06 to 2024-11-05.

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% 3 1 3 2 2 3 2 4 5% 68%	105005
	Night	9% 4 1 3 2 2 3 2 4 5% 65%	102766
Transparency	Day	20% 3 7% 17% 25% 28%	104755
	Night	23% 3 9% 19% 23% 24%	102606
Seeing	Day	10% 10% 28% 33% 14% 5%	15253
	Night	10% 2 12% 37% 30% 8%	24699

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	16% 8% 2 5% 3 3 4 3 5% 8% 43%	2539
	11th to 20th	Day	17% 7% 2 8% 5% 6% 6% 4 5% 6% 35%	2741
	21st to end	Day	19% 6% 2 6% 5% 5% 5% 3 5% 8% 36%	3146
February	1st to 10th	Day	18% 6% 2 4 3 3 3 3 4 6% 49%	1762
	11th to 20th	Day	14% 6% 1 4 4 3 3 4 5% 7% 50%	1850
	21st to end	Day	18% 7% 2 6% 3 3 4 3 4 5% 46%	1570
March	1st to 10th	Day	15% 11% 3 7% 4 4 5% 4 7% 8% 32%	3138
	11th to 20th	Day	11% 5% 1 3 3 3 3 3 4 6% 60%	3458
	21st to end	Day	16% 8% 2 6% 4 4 4 4 5% 7% 40%	4062
April	1st to 10th	Day	12% 5% 2 4 3 3 3 3 5% 5% 55%	2280
	11th to 20th	Day	10% 5% 1 5% 3 3 4 2 5% 6% 56%	2249
	21st to end	Day	8% 4 1 3 3 3 2 3 4 6% 62%	2280
May	1st to 10th	Day	5% 3 1 2 1 1 2 2 2 5% 75%	3882
	11th to 20th	Day	3 2 1 2 1 2 2 2 3 4 79%	4177
	21st to end	Day	4 2 1 2 1 2 2 2 3 4 77%	4813
June	1st to 10th	Day	3 3 1 2 2 2 3 2 4 6% 71%	2660
	11th to 20th	Day	1 1 1 1 1 2 2 2 4 85%	2660
	21st to end	Day	2 2 1 1 1 1 1 2 3 86%	2660
July	1st to 10th	Day	1 1 1 1 2 2 92%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 4 84%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4522
August	1st to 10th	Day	2 1 1 2 1 1 1 1 2 3 85%	3951
	11th to 20th	Day	1 1 1 1 1 2 3 91%	3724
	21st to end	Day	1 1 1 1 1 1 1 2 2 89%	4180
September	1st to 10th	Day	2 1 1 1 1 1 1 2 2 88%	2280
	11th to 20th	Day	2 2 1 2 1 1 2 2 3 4 81%	2247
	21st to end	Day	2 2 1 2 1 1 1 2 3 4 82%	2090
October	1st to 10th	Day	2 2 1 2 2 1 2 2 3 4 78%	3249
	11th to 20th	Day	3 2 1 2 1 2 2 2 3 4 79%	3161
	21st to end	Day	4 2 1 3 3 3 3 3 4 5% 68%	3433
November	1st to 10th	Day	9% 4 1 3 4 3 4 3 5% 7% 58%	1710
	11th to 20th	Day	8% 3 1 4 3 2 4 3 5% 6% 61%	1710
	21st to end	Day	11% 3 1 4 3 4 3 3 4 7% 57%	1710
December	1st to 10th	Day	14% 5% 1 4 4 4 3 2 4 6% 53%	1549
	11th to 20th	Day	25% 8% 2 6% 5% 3 3 3 4 5% 36%	1928
	21st to end	Day	13% 6% 4 6% 4 5% 5% 5% 6% 9% 37%	2794
January	1st to 10th	Night	15% 7% 3 6% 4 3 3 3 5% 6% 45%	4406
	11th to 20th	Night	19% 7% 3 5% 3 4 4 4 5% 7% 37%	4220
	21st to end	Night	20% 7% 2 6% 4 4 4 3 5% 7% 38%	4521
February	1st to 10th	Night	16% 6% 2 4 4 2 3 3 4 6% 50%	2416
	11th to 20th	Night	13% 5% 1 3 3 3 2 3 4 7% 54%	2218
	21st to end	Night	17% 8% 2 4 2 2 3 3 3 5% 51%	1884
March	1st to 10th	Night	20% 8% 2 5% 4 3 4 4 5% 6% 40%	3736
	11th to 20th	Night	12% 5% 1 3 2 2 2 3 3 5% 61%	3506
	21st to end	Night	21% 6% 2 4 3 3 3 3 5% 5% 45%	3590
April	1st to 10th	Night	11% 5% 2 3 2 3 3 4 4 7% 57%	1900
	11th to 20th	Night	8% 4 1 3 4 3 4 3 3 5% 62%	1879
	21st to end	Night	5% 4 1 3 3 2 3 3 4 7% 67%	1900
May	1st to 10th	Night	3 2 1 1 1 1 2 2 3 6% 77%	3094
	11th to 20th	Night	3 1 2 1 1 2 1 3 6% 79%	2719
	21st to end	Night	2 1 1 2 1 2 2 2 2 4 81%	2762
June	1st to 10th	Night	3 2 1 2 2 3 2 3 3 7% 72%	1520
	11th to 20th	Night	1 1 1 1 2 1 2 4 88%	1520
	21st to end	Night	1 1 1 1 2 2 1 2 2 86%	1520
July	1st to 10th	Night	1 1 1 1 1 1 94%	2540
	11th to 20th	Night	3 2 2 2 2 2 2 2 3 79%	2540
	21st to end	Night	1 1 1 1 1 1 2 1 3 3 84%	3035
August	1st to 10th	Night	1 2 1 2 2 2 2 2 3 3 82%	2993
	11th to 20th	Night	1 1 1 1 1 1 2 2 89%	3126
	21st to end	Night	2 1 1 1 1 1 1 2 1 89%	3498
September	1st to 10th	Night	1 1 1 2 1 1 2 2 89%	1900
	11th to 20th	Night	2 2 1 2 1 2 2 2 2 3 82%	1933
	21st to end	Night	2 1 1 2 1 1 2 1 3 4 83%	2090
October	1st to 10th	Night	2 1 1 2 1 1 2 1 2 4 82%	3728
	11th to 20th	Night	2 1 1 2 1 2 2 2 2 4 81%	3777
	21st to end	Night	5% 3 1 3 1 2 1 2 3 5% 74%	4121
November	1st to 10th	Night	10% 4 1 2 2 2 2 2 4 6% 64%	2469
	11th to 20th	Night	8% 3 1 3 2 2 3 3 4 7% 63%	2470
	21st to end	Night	11% 3 2 3 3 3 3 3 5% 5% 60%	2470
December	1st to 10th	Night	15% 4 2 4 4 2 3 2 4 7% 52%	2627
	11th to 20th	Night	25% 7% 2 4 4 3 3 3 6% 6% 38%	3276
	21st to end	Night	15% 6% 2 7% 5% 5% 5% 5% 6% 7% 36%	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	39% 9% 17% 23% 10% 2	2539
	11th to 20th	Day	49% 6% 10% 16% 11% 8%	2741
	21st to end	Day	46% 7% 13% 20% 10% 3	3146
February	1st to 10th	Day	37% 4 8% 26% 17% 8%	1762
	11th to 20th	Day	32% 3 12% 25% 22% 6%	1860
	21st to end	Day	39% 5% 10% 25% 20% 1	1570
March	1st to 10th	Day	44% 7% 13% 19% 14% 2	3138
	11th to 20th	Day	26% 4 12% 32% 16% 11%	3458
	21st to end	Day	39% 5% 15% 25% 14% 2	4062
April	1st to 10th	Day	29% 4 12% 27% 20% 8%	2280
	11th to 20th	Day	28% 3 11% 27% 23% 8%	2252
	21st to end	Day	23% 4 10% 31% 27% 6%	2280
May	1st to 10th	Day	14% 2 6% 28% 33% 17%	3882
	11th to 20th	Day	10% 3 5% 24% 42% 16%	4180
	21st to end	Day	12% 2 7% 27% 40% 13%	4814
June	1st to 10th	Day	14% 3 9% 22% 32% 20%	2660
	11th to 20th	Day	7% 1 5% 17% 39% 31%	2660
	21st to end	Day	8% 1 2 7% 31% 51%	2660
July	1st to 10th	Day	3 1 1 3 13% 79%	4351
	11th to 20th	Day	7% 1 2 5% 14% 70%	4345
	21st to end	Day	6% 1 2 6% 25% 60%	4379
August	1st to 10th	Day	8% 1 1 6% 25% 59%	3936
	11th to 20th	Day	4 1 1 4 23% 67%	3760
	21st to end	Day	6% 1 2 6% 29% 56%	4179
September	1st to 10th	Day	7% 1 2 6% 27% 56%	2280
	11th to 20th	Day	9% 1 3 21% 37% 28%	2247
	21st to end	Day	9% 1 3 17% 37% 33%	2090
October	1st to 10th	Day	12% 2 4 10% 20% 52%	3249
	11th to 20th	Day	11% 2 4 20% 43% 20%	3161
	21st to end	Day	18% 2 4 15% 43% 17%	3433
November	1st to 10th	Day	25% 4 12% 22% 23% 15%	1710
	11th to 20th	Day	24% 4 12% 24% 28% 8%	1710
	21st to end	Day	27% 5% 8% 20% 28% 12%	1710
December	1st to 10th	Day	34% 4 11% 21% 20% 10%	1549
	11th to 20th	Day	52% 3 9% 16% 14% 6%	1928
	21st to end	Day	43% 7% 15% 23% 9% 4	2794
January	1st to 10th	Night	38% 6% 21% 21% 12% 2	4406
	11th to 20th	Night	46% 6% 17% 13% 11% 7%	4220
	21st to end	Night	44% 5% 13% 22% 12% 4	4521
February	1st to 10th	Night	35% 3 11% 23% 19% 9%	2416
	11th to 20th	Night	29% 4 11% 27% 22% 7%	2219
	21st to end	Night	36% 2 12% 26% 19% 4	1884
March	1st to 10th	Night	44% 4 12% 21% 16% 2	3736
	11th to 20th	Night	27% 3 11% 34% 16% 9%	3506
	21st to end	Night	40% 3 15% 25% 14% 3	3590
April	1st to 10th	Night	27% 4 16% 26% 19% 8%	1900
	11th to 20th	Night	23% 3 13% 29% 23% 8%	1879
	21st to end	Night	19% 3 12% 32% 28% 5%	1900
May	1st to 10th	Night	11% 3 8% 32% 32% 14%	3094
	11th to 20th	Night	9% 2 6% 28% 40% 16%	2720
	21st to end	Night	10% 2 7% 29% 44% 9%	2762
June	1st to 10th	Night	13% 3 12% 22% 31% 19%	1520
	11th to 20th	Night	5% 1 5% 19% 40% 30%	1520
	21st to end	Night	7% 1 2 8% 29% 52%	1520
July	1st to 10th	Night	2 1 3 15% 79%	2500
	11th to 20th	Night	12% 1 1 4 14% 68%	2492
	21st to end	Night	8% 1 1 5% 22% 63%	2940
August	1st to 10th	Night	10% 1 1 6% 20% 61%	2984
	11th to 20th	Night	5% 1 1 5% 18% 70%	3156
	21st to end	Night	7% 1 1 6% 27% 60%	3498
September	1st to 10th	Night	5% 1 2 6% 27% 60%	1900
	11th to 20th	Night	9% 2 4 15% 40% 30%	1933
	21st to end	Night	9% 1 3 14% 39% 34%	2090
October	1st to 10th	Night	10% 1 3 9% 22% 55%	3728
	11th to 20th	Night	10% 1 4 23% 40% 21%	3777
	21st to end	Night	16% 1 3 20% 37% 23%	4121
November	1st to 10th	Night	23% 3 9% 25% 22% 18%	2469
	11th to 20th	Night	21% 3 11% 27% 25% 13%	2470
	21st to end	Night	25% 3 8% 23% 29% 11%	2470
December	1st to 10th	Night	34% 4 10% 22% 19% 12%	2627
	11th to 20th	Night	46% 4 12% 17% 16% 6%	3276
	21st to end	Night	43% 7% 16% 21% 9% 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	32% 11% 16% 26% 12% 4	180
	11th to 20th	Day	22% 6% 23% 30% 15% 4	303
	21st to end	Day	19% 5% 25% 31% 16% 4	407
February	1st to 10th	Day	24% 11% 24% 22% 14% 5%	394
	11th to 20th	Day	19% 11% 33% 24% 11% 2	455
	21st to end	Day	19% 13% 35% 24% 9% 1	382
March	1st to 10th	Day	23% 12% 35% 22% 7% 1	460
	11th to 20th	Day	22% 15% 27% 24% 11% 2	460
	21st to end	Day	23% 14% 33% 23% 7%	506
April	1st to 10th	Day	17% 19% 30% 23% 10% 1	460
	11th to 20th	Day	16% 18% 29% 26% 8% 2	452
	21st to end	Day	8% 18% 30% 27% 12% 4	460
May	1st to 10th	Day	8% 19% 33% 26% 8% 5%	463
	11th to 20th	Day	8% 15% 31% 31% 9% 6%	488
	21st to end	Day	10% 11% 26% 33% 13% 7%	529
June	1st to 10th	Day	4 13% 29% 33% 13% 7%	490
	11th to 20th	Day	3 13% 31% 33% 11% 8%	490
	21st to end	Day	3 8% 30% 33% 15% 10%	490
July	1st to 10th	Day	1 3 27% 44% 15% 10%	486
	11th to 20th	Day	1 2 18% 54% 14% 12%	484
	21st to end	Day	2 2 24% 45% 17% 11%	531
August	1st to 10th	Day	4 3 31% 40% 14% 9%	487
	11th to 20th	Day	1 4 29% 42% 14% 8%	477
	21st to end	Day	1 3 24% 46% 17% 8%	539
September	1st to 10th	Day	2 4 25% 46% 18% 5%	490
	11th to 20th	Day	5% 8% 33% 33% 18% 3	490
	21st to end	Day	3 7% 26% 45% 17% 2	490
October	1st to 10th	Day	3 11% 27% 37% 20% 2	490
	11th to 20th	Day	6% 8% 27% 35% 20% 4	490
	21st to end	Day	6% 8% 27% 35% 20% 3	536
November	1st to 10th	Day	10% 8% 23% 29% 23% 7%	282
	11th to 20th	Day	7% 6% 21% 40% 18% 8%	270
	21st to end	Day	11% 8% 23% 32% 20% 7%	270
December	1st to 10th	Day	18% 4 27% 25% 20% 7%	194
	11th to 20th	Day	16% 7% 26% 27% 17% 6%	180
	21st to end	Day	22% 7% 22% 26% 17% 6%	198
January	1st to 10th	Night	20% 2 17% 31% 21% 10%	760
	11th to 20th	Night	15% 3 14% 39% 22% 7%	760
	21st to end	Night	19% 2 15% 35% 22% 8%	836
February	1st to 10th	Night	20% 3 14% 36% 21% 6%	760
	11th to 20th	Night	17% 4 15% 33% 22% 8%	744
	21st to end	Night	21% 4 16% 39% 18% 3	628
March	1st to 10th	Night	22% 4 15% 35% 19% 5%	760
	11th to 20th	Night	17% 4 16% 31% 26% 7%	760
	21st to end	Night	19% 3 18% 36% 22% 3	836
April	1st to 10th	Night	13% 4 17% 37% 24% 4	760
	11th to 20th	Night	10% 6% 19% 36% 22% 7%	751
	21st to end	Night	7% 5% 17% 39% 25% 8%	760
May	1st to 10th	Night	7% 5% 18% 38% 24% 7%	713
	11th to 20th	Night	6% 2 16% 38% 35% 2	499
	21st to end	Night	6% 3 12% 39% 34% 6%	411
June	1st to 10th	Night	3 4 8% 36% 42% 6%	380
	11th to 20th	Night	1 2 10% 39% 43% 5%	380
	21st to end	Night	1 7% 37% 48% 7%	380
July	1st to 10th	Night	3 36% 53% 7%	370
	11th to 20th	Night	3 1 34% 52% 9%	368
	21st to end	Night	2 1 2 28% 52% 16%	576
August	1st to 10th	Night	2 3 39% 43% 12%	647
	11th to 20th	Night	1 6% 39% 43% 11%	752
	21st to end	Night	2 4 33% 49% 12%	836
September	1st to 10th	Night	1 1 5% 35% 47% 11%	760
	11th to 20th	Night	3 1 7% 39% 39% 12%	760
	21st to end	Night	2 1 9% 36% 40% 12%	760
October	1st to 10th	Night	5% 1 8% 46% 31% 10%	760
	11th to 20th	Night	4 2 11% 39% 33% 11%	760
	21st to end	Night	6% 1 12% 35% 31% 16%	836
November	1st to 10th	Night	12% 3 10% 34% 30% 11%	760
	11th to 20th	Night	10% 1 14% 39% 27% 9%	760
	21st to end	Night	11% 2 15% 38% 25% 8%	760
December	1st to 10th	Night	17% 2 13% 41% 20% 7%	760
	11th to 20th	Night	21% 1 14% 38% 20% 5%	760
	21st to end	Night	21% 3 17% 36% 18% 4	836

Page generated at 2024-11-02 23:11:20. Version ac07

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