Don Pedro Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Don Pedro Reservoir clear sky chart from 2005-11-06 to 2024-11-12.

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	8% 3 1 3 2 2 3 2 4 5% 67%	105091
	Night	10% 4 1 3 2 2 3 2 4 5% 63%	102829
Transparency	Day	21% 3 7% 17% 24% 28%	104842
	Night	25% 3 8% 19% 22% 23%	102667
Seeing	Day	10% 8% 25% 34% 17% 5%	15262
	Night	11% 2 13% 38% 29% 7%	24661

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	19% 8% 2 4 3 3 3 2 4 6% 44%	2539
	11th to 20th	Day	20% 7% 3 8% 5% 6% 4 3 3 6% 34%	2768
	21st to end	Day	21% 8% 3 6% 4 4 5% 3 5% 8% 32%	3146
February	1st to 10th	Day	19% 7% 1 4 3 3 3 3 4 5% 48%	1721
	11th to 20th	Day	15% 6% 3 4 3 3 4 3 5% 7% 47%	1850
	21st to end	Day	18% 6% 2 4 4 4 4 3 4 5% 45%	1570
March	1st to 10th	Day	15% 10% 3 7% 5% 5% 6% 5% 7% 7% 29%	3159
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 4 6% 57%	3490
	21st to end	Day	15% 7% 3 7% 4 5% 5% 4 6% 8% 38%	4031
April	1st to 10th	Day	13% 6% 1 4 3 3 4 3 4 6% 52%	2280
	11th to 20th	Day	12% 4 2 3 3 3 2 4 5% 7% 56%	2249
	21st to end	Day	8% 4 2 3 3 2 3 2 4 5% 64%	2280
May	1st to 10th	Day	6% 3 1 2 2 2 2 2 4 5% 73%	3852
	11th to 20th	Day	3 2 1 2 1 1 1 2 3 5% 79%	4253
	21st to end	Day	4 2 1 2 2 2 2 2 3 4 77%	4813
June	1st to 10th	Day	3 2 1 3 3 2 2 3 3 6% 69%	2660
	11th to 20th	Day	1 1 2 1 1 2 2 2 4 83%	2660
	21st to end	Day	2 2 1 1 1 1 1 2 2 84%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 93%	4420
	11th to 20th	Day	1 1 1 1 2 2 2 3 3 83%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 2 88%	4494
August	1st to 10th	Day	2 1 2 1 1 2 1 3 3 84%	4013
	11th to 20th	Day	1 1 1 1 1 2 3 90%	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 1 2 89%	2280
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 79%	2266
	21st to end	Day	3 1 1 2 1 2 1 1 3 3 82%	2090
October	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 76%	3188
	11th to 20th	Day	3 2 1 2 1 2 2 2 2 3 79%	3161
	21st to end	Day	5% 2 1 3 2 3 3 3 5% 6% 66%	3448
November	1st to 10th	Day	9% 4 2 4 3 3 4 3 5% 6% 56%	1778
	11th to 20th	Day	10% 4 1 4 3 3 3 3 4 7% 59%	1719
	21st to end	Day	12% 4 1 3 4 3 2 3 4 7% 56%	1687
December	1st to 10th	Day	15% 6% 2 4 3 3 2 3 4 6% 53%	1520
	11th to 20th	Day	26% 9% 2 7% 4 3 3 2 4 5% 35%	1928
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 36%	2794
January	1st to 10th	Night	16% 8% 3 5% 3 3 3 3 6% 6% 44%	4406
	11th to 20th	Night	21% 8% 2 5% 4 4 4 3 5% 7% 36%	4196
	21st to end	Night	23% 7% 2 6% 3 4 4 4 5% 7% 35%	4521
February	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 4 5% 50%	2456
	11th to 20th	Night	16% 6% 1 4 2 3 2 4 4 7% 51%	2218
	21st to end	Night	17% 9% 2 4 3 2 3 2 3 5% 50%	1884
March	1st to 10th	Night	20% 9% 2 5% 4 4 4 4 5% 5% 37%	3713
	11th to 20th	Night	14% 4 1 3 2 2 3 2 3 5% 59%	3490
	21st to end	Night	22% 7% 1 5% 3 3 3 4 5% 6% 41%	3622
April	1st to 10th	Night	13% 4 1 4 3 4 4 3 4 7% 53%	1900
	11th to 20th	Night	10% 5% 1 4 2 3 3 3 4 4 61%	1879
	21st to end	Night	7% 4 1 3 2 3 3 3 4 7% 64%	1900
May	1st to 10th	Night	4 4 1 2 2 2 2 2 2 5% 76%	3123
	11th to 20th	Night	3 1 1 2 2 1 1 2 3 5% 80%	2626
	21st to end	Night	3 2 1 1 2 2 2 2 2 4 80%	2762
June	1st to 10th	Night	4 3 1 2 1 2 3 2 4 6% 73%	1520
	11th to 20th	Night	1 1 2 2 3 4 86%	1520
	21st to end	Night	1 2 1 1 1 1 1 2 2 3 85%	1520
July	1st to 10th	Night	1 1 1 1 1 1 95%	2540
	11th to 20th	Night	3 1 1 2 2 2 3 1 2 3 80%	2540
	21st to end	Night	1 1 1 1 1 2 2 2 3 84%	3065
August	1st to 10th	Night	2 1 1 2 1 2 2 2 3 4 80%	2926
	11th to 20th	Night	1 1 1 1 1 1 2 2 88%	3126
	21st to end	Night	2 1 1 1 1 1 1 1 2 89%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 2 90%	1900
	11th to 20th	Night	3 1 1 1 1 2 1 2 4 82%	1912
	21st to end	Night	2 1 1 2 1 1 1 2 2 4 83%	2090
October	1st to 10th	Night	3 1 1 2 1 2 2 2 3 4 80%	3789
	11th to 20th	Night	2 1 1 2 1 1 2 2 3 4 81%	3777
	21st to end	Night	6% 2 1 3 2 2 2 2 4 5% 70%	4121
November	1st to 10th	Night	11% 4 1 3 2 3 2 2 4 6% 62%	2519
	11th to 20th	Night	9% 3 1 3 2 3 4 2 6% 6% 60%	2483
	21st to end	Night	11% 4 1 3 3 3 3 3 3 6% 59%	2489
December	1st to 10th	Night	16% 5% 2 4 2 2 4 3 5% 5% 52%	2660
	11th to 20th	Night	25% 8% 2 5% 3 3 3 3 5% 6% 36%	3276
	21st to end	Night	16% 7% 3 7% 6% 5% 5% 4 5% 6% 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	43% 5% 13% 25% 11% 3	2539
	11th to 20th	Day	51% 7% 9% 14% 11% 8%	2768
	21st to end	Day	48% 8% 11% 19% 12% 3	3146
February	1st to 10th	Day	39% 3 8% 26% 16% 9%	1721
	11th to 20th	Day	35% 4 9% 23% 23% 6%	1860
	21st to end	Day	41% 3 10% 23% 20% 3	1570
March	1st to 10th	Day	48% 7% 15% 15% 14% 2	3159
	11th to 20th	Day	28% 5% 11% 31% 15% 10%	3490
	21st to end	Day	41% 5% 18% 22% 12% 2	4031
April	1st to 10th	Day	33% 4 12% 26% 17% 8%	2280
	11th to 20th	Day	29% 3 13% 29% 19% 7%	2252
	21st to end	Day	24% 3 10% 31% 27% 5%	2280
May	1st to 10th	Day	16% 2 6% 29% 28% 19%	3852
	11th to 20th	Day	11% 2 5% 24% 42% 16%	4256
	21st to end	Day	13% 2 8% 26% 41% 11%	4814
June	1st to 10th	Day	17% 3 9% 21% 32% 18%	2660
	11th to 20th	Day	8% 1 5% 20% 36% 30%	2660
	21st to end	Day	9% 1 1 10% 30% 50%	2660
July	1st to 10th	Day	3 1 1 4 13% 79%	4351
	11th to 20th	Day	7% 2 2 6% 14% 69%	4345
	21st to end	Day	5% 1 1 5% 23% 64%	4352
August	1st to 10th	Day	8% 2 1 6% 21% 62%	3998
	11th to 20th	Day	4 1 1 5% 23% 66%	3760
	21st to end	Day	6% 1 2 5% 30% 55%	4179
September	1st to 10th	Day	6% 1 2 6% 27% 58%	2280
	11th to 20th	Day	11% 2 3 20% 38% 26%	2266
	21st to end	Day	10% 1 2 17% 37% 32%	2090
October	1st to 10th	Day	12% 2 4 10% 19% 52%	3188
	11th to 20th	Day	12% 2 4 18% 42% 21%	3161
	21st to end	Day	19% 2 6% 15% 39% 19%	3448
November	1st to 10th	Day	28% 3 10% 24% 23% 13%	1778
	11th to 20th	Day	26% 4 10% 24% 27% 9%	1719
	21st to end	Day	29% 4 9% 21% 26% 11%	1687
December	1st to 10th	Day	34% 5% 10% 21% 18% 11%	1520
	11th to 20th	Day	54% 3 7% 16% 14% 6%	1928
	21st to end	Day	43% 7% 15% 23% 8% 4	2794
January	1st to 10th	Night	39% 6% 17% 23% 12% 3	4406
	11th to 20th	Night	48% 6% 13% 15% 11% 8%	4196
	21st to end	Night	47% 6% 11% 20% 12% 4	4521
February	1st to 10th	Night	37% 3 8% 22% 20% 10%	2456
	11th to 20th	Night	33% 3 10% 25% 22% 8%	2219
	21st to end	Night	39% 3 11% 24% 19% 4	1884
March	1st to 10th	Night	48% 5% 12% 18% 14% 3	3713
	11th to 20th	Night	30% 3 10% 31% 16% 11%	3490
	21st to end	Night	43% 4 14% 25% 11% 3	3622
April	1st to 10th	Night	31% 4 15% 24% 19% 7%	1900
	11th to 20th	Night	27% 4 13% 27% 21% 9%	1879
	21st to end	Night	22% 4 12% 31% 24% 7%	1900
May	1st to 10th	Night	14% 3 11% 29% 30% 14%	3123
	11th to 20th	Night	10% 1 8% 25% 38% 18%	2626
	21st to end	Night	11% 2 7% 33% 40% 7%	2762
June	1st to 10th	Night	14% 3 12% 24% 31% 16%	1520
	11th to 20th	Night	5% 2 6% 22% 36% 29%	1520
	21st to end	Night	8% 1 2 10% 31% 48%	1520
July	1st to 10th	Night	2 4 14% 79%	2500
	11th to 20th	Night	11% 1 3 5% 14% 66%	2492
	21st to end	Night	8% 2 2 4 22% 63%	2969
August	1st to 10th	Night	10% 1 2 8% 20% 60%	2917
	11th to 20th	Night	5% 1 1 5% 25% 62%	3156
	21st to end	Night	7% 1 1 8% 30% 54%	3498
September	1st to 10th	Night	5% 1 2 6% 27% 59%	1900
	11th to 20th	Night	10% 2 4 18% 40% 28%	1912
	21st to end	Night	9% 1 2 17% 39% 32%	2090
October	1st to 10th	Night	11% 2 4 11% 19% 55%	3789
	11th to 20th	Night	10% 2 4 24% 37% 23%	3777
	21st to end	Night	18% 3 4 17% 37% 22%	4121
November	1st to 10th	Night	25% 2 9% 24% 21% 18%	2519
	11th to 20th	Night	25% 3 9% 25% 26% 13%	2483
	21st to end	Night	29% 3 7% 22% 29% 11%	2489
December	1st to 10th	Night	35% 4 9% 22% 18% 12%	2660
	11th to 20th	Night	48% 5% 9% 16% 17% 6%	3276
	21st to end	Night	45% 8% 13% 20% 9% 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	32% 6% 20% 25% 16% 1	180
	11th to 20th	Day	21% 3 20% 35% 16% 5%	317
	21st to end	Day	19% 7% 21% 29% 20% 4	407
February	1st to 10th	Day	24% 9% 20% 24% 19% 3	376
	11th to 20th	Day	19% 8% 32% 25% 14% 2	455
	21st to end	Day	19% 12% 26% 32% 9% 1	382
March	1st to 10th	Day	26% 12% 28% 27% 7% 1	460
	11th to 20th	Day	21% 14% 26% 23% 14% 2	460
	21st to end	Day	19% 11% 34% 25% 9% 1	506
April	1st to 10th	Day	18% 15% 28% 24% 13% 2	460
	11th to 20th	Day	16% 15% 29% 28% 10% 2	452
	21st to end	Day	9% 13% 32% 27% 15% 4	460
May	1st to 10th	Day	10% 17% 33% 27% 10% 4	463
	11th to 20th	Day	8% 13% 27% 29% 16% 6%	488
	21st to end	Day	9% 10% 25% 34% 15% 7%	529
June	1st to 10th	Day	4 10% 28% 36% 15% 6%	490
	11th to 20th	Day	3 11% 30% 37% 13% 6%	490
	21st to end	Day	3 6% 27% 38% 19% 7%	490
July	1st to 10th	Day	2 23% 50% 17% 7%	486
	11th to 20th	Day	2 18% 48% 22% 10%	484
	21st to end	Day	1 2 18% 48% 20% 11%	531
August	1st to 10th	Day	4 4 21% 47% 16% 9%	487
	11th to 20th	Day	1 3 29% 39% 19% 9%	477
	21st to end	Day	1 3 22% 44% 22% 9%	539
September	1st to 10th	Day	2 3 22% 46% 22% 5%	490
	11th to 20th	Day	5% 8% 28% 35% 20% 3	490
	21st to end	Day	3 6% 23% 45% 21% 2	490
October	1st to 10th	Day	4 9% 27% 34% 23% 3	490
	11th to 20th	Day	7% 7% 22% 34% 25% 5%	490
	21st to end	Day	8% 7% 23% 35% 24% 4	539
November	1st to 10th	Day	10% 9% 21% 30% 25% 5%	314
	11th to 20th	Day	10% 5% 20% 32% 27% 7%	273
	21st to end	Day	12% 5% 22% 33% 23% 5%	259
December	1st to 10th	Day	17% 5% 22% 31% 18% 6%	180
	11th to 20th	Day	20% 6% 23% 26% 22% 3	180
	21st to end	Day	23% 5% 25% 24% 19% 5%	198
January	1st to 10th	Night	21% 2 17% 31% 20% 9%	760
	11th to 20th	Night	16% 4 13% 38% 23% 6%	760
	21st to end	Night	20% 3 13% 35% 21% 7%	836
February	1st to 10th	Night	20% 2 16% 35% 21% 6%	760
	11th to 20th	Night	19% 3 15% 34% 20% 8%	744
	21st to end	Night	23% 3 14% 41% 15% 3	628
March	1st to 10th	Night	23% 4 16% 34% 18% 4	760
	11th to 20th	Night	19% 4 17% 29% 23% 7%	760
	21st to end	Night	19% 3 17% 38% 21% 2	836
April	1st to 10th	Night	15% 4 16% 40% 23% 3	760
	11th to 20th	Night	12% 4 20% 36% 22% 6%	751
	21st to end	Night	8% 4 17% 40% 25% 6%	760
May	1st to 10th	Night	7% 4 21% 41% 21% 6%	729
	11th to 20th	Night	5% 3 18% 38% 33% 3	445
	21st to end	Night	5% 2 14% 41% 34% 4	411
June	1st to 10th	Night	6% 2 14% 41% 32% 5%	380
	11th to 20th	Night	1 1 14% 45% 36% 4	380
	21st to end	Night	1 1 10% 44% 41% 4	380
July	1st to 10th	Night	4 46% 45% 5%	370
	11th to 20th	Night	2 4 43% 45% 7%	368
	21st to end	Night	2 4 32% 51% 11%	593
August	1st to 10th	Night	2 6% 36% 46% 10%	606
	11th to 20th	Night	1 1 7% 44% 41% 8%	752
	21st to end	Night	2 5% 38% 48% 7%	836
September	1st to 10th	Night	1 6% 42% 43% 9%	760
	11th to 20th	Night	3 1 11% 41% 36% 9%	760
	21st to end	Night	2 1 9% 41% 37% 10%	760
October	1st to 10th	Night	5% 1 11% 46% 31% 7%	760
	11th to 20th	Night	5% 3 10% 39% 34% 9%	760
	21st to end	Night	6% 1 14% 36% 30% 13%	836
November	1st to 10th	Night	12% 3 9% 36% 29% 11%	780
	11th to 20th	Night	11% 2 13% 39% 29% 7%	764
	21st to end	Night	13% 1 14% 39% 25% 8%	760
December	1st to 10th	Night	19% 2 13% 40% 20% 6%	760
	11th to 20th	Night	25% 2 11% 36% 21% 5%	760
	21st to end	Night	22% 5% 17% 34% 19% 4	836

Page generated at 2024-11-08 19:45:36. Version ac07

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