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 2024-01-13.

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 3 2 3 3 4 5% 65%	74757
	Night	10% 4 1 3 3 2 3 3 4 5% 62%	74999
Transparency	Day	23% 3 7% 19% 25% 23%	74471
	Night	25% 3 8% 20% 24% 20%	74806
Seeing	Day	10% 8% 25% 34% 18% 5%	14088
	Night	11% 2 12% 38% 30% 7%	23609

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% 7% 2 4 3 3 4 4 4 8% 43%	1519
	11th to 20th	Day	14% 5% 2 3 4 3 4 3 4 8% 51%	1589
	21st to end	Day	17% 7% 2 4 4 3 4 4 5% 8% 42%	1782
February	1st to 10th	Day	19% 5% 2 3 3 2 3 4 4 5% 50%	1631
	11th to 20th	Day	15% 5% 3 3 3 2 4 4 4 8% 49%	1750
	21st to end	Day	19% 6% 3 4 4 3 4 4 4 5% 45%	1480
March	1st to 10th	Day	18% 9% 3 4 5% 3 4 5% 6% 7% 37%	1808
	11th to 20th	Day	17% 7% 2 5% 4 3 4 4 5% 6% 41%	1980
	21st to end	Day	14% 5% 3 5% 4 2 5% 4 5% 7% 46%	2294
April	1st to 10th	Day	14% 5% 2 3 3 3 4 4 4 6% 51%	2160
	11th to 20th	Day	12% 3 2 4 3 2 2 4 5% 7% 56%	2129
	21st to end	Day	9% 4 2 3 3 2 2 3 4 5% 64%	2160
May	1st to 10th	Day	6% 4 1 3 2 2 2 3 5% 5% 66%	2186
	11th to 20th	Day	5% 3 1 3 3 2 2 3 4 6% 68%	2405
	21st to end	Day	7% 3 2 3 3 2 3 4 5% 5% 64%	2723
June	1st to 10th	Day	3 2 1 3 3 2 2 3 3 6% 69%	2520
	11th to 20th	Day	1 1 1 1 2 1 1 2 2 5% 83%	2520
	21st to end	Day	3 2 1 1 2 1 1 1 2 3 84%	2520
July	1st to 10th	Day	1 1 1 1 2 2 2 2 88%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 3 3 3 83%	2520
	21st to end	Day	1 1 1 1 2 2 2 3 3 3 81%	2572
August	1st to 10th	Day	2 1 1 1 1 2 2 2 2 84%	2289
	11th to 20th	Day	1 1 1 1 1 1 2 3 4 86%	2122
	21st to end	Day	1 1 1 1 1 1 1 2 3 88%	2376
September	1st to 10th	Day	2 1 1 1 1 1 1 1 2 88%	2160
	11th to 20th	Day	2 1 1 1 2 1 2 2 3 4 80%	2147
	21st to end	Day	3 1 1 2 1 1 2 2 3 3 81%	1980
October	1st to 10th	Day	4 2 2 2 3 1 3 2 3 5% 73%	1808
	11th to 20th	Day	4 2 1 2 2 2 2 4 3 5% 73%	1800
	21st to end	Day	6% 2 1 2 2 1 3 3 4 5% 69%	1980
November	1st to 10th	Day	9% 4 2 4 3 2 4 4 5% 6% 56%	1688
	11th to 20th	Day	9% 4 1 3 3 2 3 4 4 7% 59%	1710
	21st to end	Day	12% 4 2 3 4 2 2 3 4 7% 57%	1687
December	1st to 10th	Day	15% 6% 2 3 3 3 3 3 4 6% 53%	1520
	11th to 20th	Day	26% 8% 3 6% 5% 2 3 3 4 5% 35%	1928
	21st to end	Day	14% 7% 3 6% 6% 4 5% 6% 6% 9% 36%	2794
January	1st to 10th	Night	19% 5% 2 4 4 2 3 4 6% 7% 44%	2646
	11th to 20th	Night	13% 6% 2 3 4 3 4 4 5% 7% 49%	2429
	21st to end	Night	17% 5% 2 3 3 2 4 4 5% 7% 48%	2574
February	1st to 10th	Night	15% 5% 2 4 3 2 4 2 3 6% 53%	2326
	11th to 20th	Night	15% 5% 2 3 3 2 2 4 4 7% 52%	2098
	21st to end	Night	18% 9% 2 3 3 2 3 3 3 5% 50%	1776
March	1st to 10th	Night	20% 7% 3 4 4 2 3 4 4 5% 43%	2150
	11th to 20th	Night	18% 5% 2 4 3 3 3 3 5% 8% 46%	1980
	21st to end	Night	17% 5% 1 4 3 1 3 4 4 7% 51%	2062
April	1st to 10th	Night	14% 3 2 4 3 2 4 4 4 7% 53%	1800
	11th to 20th	Night	10% 4 1 4 2 2 4 3 4 5% 61%	1779
	21st to end	Night	7% 4 2 3 2 2 3 3 4 7% 64%	1800
May	1st to 10th	Night	6% 3 1 2 2 1 3 3 3 6% 68%	1771
	11th to 20th	Night	5% 2 1 2 3 1 2 2 4 8% 70%	1484
	21st to end	Night	5% 3 1 2 3 1 3 3 3 5% 70%	1552
June	1st to 10th	Night	4 3 1 1 2 2 3 2 3 6% 74%	1440
	11th to 20th	Night	1 1 2 3 3 4 85%	1440
	21st to end	Night	1 1 1 1 1 1 2 2 2 3 84%	1440
July	1st to 10th	Night	1 1 1 1 2 1 2 90%	1440
	11th to 20th	Night	2 1 1 2 1 2 2 2 4 82%	1440
	21st to end	Night	2 2 1 2 2 1 3 3 3 4 77%	1743
August	1st to 10th	Night	2 1 1 1 1 1 2 2 2 4 83%	1647
	11th to 20th	Night	1 1 1 1 2 1 2 3 3 4 81%	1780
	21st to end	Night	1 1 1 1 1 2 2 2 3 87%	1980
September	1st to 10th	Night	1 1 1 1 1 1 2 2 90%	1800
	11th to 20th	Night	3 1 1 1 1 2 2 2 4 83%	1811
	21st to end	Night	2 1 1 2 1 1 1 2 3 4 82%	1980
October	1st to 10th	Night	5% 2 1 2 2 1 3 3 3 4 73%	2149
	11th to 20th	Night	4 2 1 2 2 1 2 3 3 5% 75%	2160
	21st to end	Night	6% 1 1 2 2 1 1 2 4 5% 75%	2376
November	1st to 10th	Night	11% 4 1 2 2 2 2 3 3 6% 62%	2389
	11th to 20th	Night	9% 3 2 3 2 2 4 3 6% 6% 60%	2470
	21st to end	Night	11% 3 2 3 3 2 4 4 3 6% 59%	2489
December	1st to 10th	Night	16% 5% 2 3 3 1 4 3 5% 5% 52%	2660
	11th to 20th	Night	25% 7% 2 5% 4 2 3 4 5% 6% 37%	3276
	21st to end	Night	16% 7% 3 6% 7% 4 5% 5% 5% 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	42% 4 12% 24% 14% 5%	1519
	11th to 20th	Day	34% 5% 10% 20% 17% 14%	1589
	21st to end	Day	41% 4 11% 19% 20% 5%	1782
February	1st to 10th	Day	37% 2 8% 26% 17% 9%	1631
	11th to 20th	Day	34% 3 9% 23% 25% 6%	1760
	21st to end	Day	41% 3 10% 23% 20% 3	1480
March	1st to 10th	Day	45% 4 12% 20% 16% 3	1808
	11th to 20th	Day	41% 5% 10% 23% 18% 4	1980
	21st to end	Day	37% 4 17% 23% 15% 4	2294
April	1st to 10th	Day	34% 4 12% 24% 17% 8%	2160
	11th to 20th	Day	29% 3 12% 29% 20% 8%	2132
	21st to end	Day	24% 3 10% 30% 28% 5%	2160
May	1st to 10th	Day	21% 3 11% 26% 30% 11%	2186
	11th to 20th	Day	19% 3 8% 25% 32% 12%	2408
	21st to end	Day	22% 3 12% 28% 27% 8%	2724
June	1st to 10th	Day	17% 3 9% 22% 31% 18%	2520
	11th to 20th	Day	8% 1 5% 20% 35% 31%	2520
	21st to end	Day	9% 1 1 10% 31% 48%	2520
July	1st to 10th	Day	5% 2 1 6% 22% 63%	2451
	11th to 20th	Day	8% 2 2 9% 23% 56%	2445
	21st to end	Day	9% 2 1 8% 25% 54%	2429
August	1st to 10th	Day	9% 2 1 10% 25% 53%	2273
	11th to 20th	Day	5% 2 1 9% 30% 53%	2122
	21st to end	Day	6% 1 1 8% 34% 50%	2376
September	1st to 10th	Day	6% 1 2 7% 27% 57%	2160
	11th to 20th	Day	10% 2 3 20% 38% 27%	2147
	21st to end	Day	11% 1 2 18% 38% 30%	1980
October	1st to 10th	Day	16% 2 6% 17% 27% 32%	1808
	11th to 20th	Day	15% 3 6% 21% 25% 30%	1800
	21st to end	Day	18% 2 7% 21% 29% 24%	1980
November	1st to 10th	Day	29% 3 9% 23% 23% 13%	1688
	11th to 20th	Day	26% 4 10% 24% 27% 9%	1710
	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% 4 12% 23% 17% 4	2646
	11th to 20th	Night	34% 6% 12% 19% 17% 13%	2429
	21st to end	Night	37% 4 12% 18% 21% 8%	2574
February	1st to 10th	Night	35% 3 9% 23% 21% 10%	2326
	11th to 20th	Night	31% 3 10% 25% 23% 8%	2099
	21st to end	Night	39% 2 10% 25% 19% 5%	1776
March	1st to 10th	Night	43% 3 12% 19% 19% 4	2150
	11th to 20th	Night	39% 3 11% 22% 20% 6%	1980
	21st to end	Night	34% 5% 14% 25% 16% 6%	2062
April	1st to 10th	Night	32% 4 16% 23% 19% 7%	1800
	11th to 20th	Night	27% 4 12% 26% 22% 9%	1779
	21st to end	Night	22% 4 12% 31% 24% 7%	1800
May	1st to 10th	Night	18% 4 12% 24% 32% 11%	1771
	11th to 20th	Night	16% 1 11% 29% 30% 12%	1484
	21st to end	Night	17% 4 11% 32% 27% 9%	1552
June	1st to 10th	Night	15% 3 12% 23% 31% 16%	1440
	11th to 20th	Night	5% 2 6% 22% 34% 30%	1440
	21st to end	Night	8% 1 2 10% 32% 46%	1440
July	1st to 10th	Night	4 1 1 7% 26% 62%	1400
	11th to 20th	Night	9% 1 3 8% 22% 57%	1392
	21st to end	Night	13% 2 2 6% 21% 55%	1646
August	1st to 10th	Night	9% 1 2 11% 25% 51%	1638
	11th to 20th	Night	9% 2 1 10% 27% 51%	1780
	21st to end	Night	6% 1 1 9% 30% 53%	1980
September	1st to 10th	Night	6% 1 2 6% 27% 58%	1800
	11th to 20th	Night	9% 2 4 17% 39% 29%	1811
	21st to end	Night	9% 2 2 17% 40% 30%	1980
October	1st to 10th	Night	16% 2 6% 18% 26% 32%	2149
	11th to 20th	Night	14% 3 6% 19% 27% 31%	2160
	21st to end	Night	13% 2 5% 21% 33% 25%	2376
November	1st to 10th	Night	25% 2 9% 23% 21% 19%	2389
	11th to 20th	Night	25% 3 9% 25% 26% 13%	2470
	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	33% 6% 20% 25% 16% 1	180
	11th to 20th	Day	22% 3 20% 34% 16% 5%	295
	21st to end	Day	19% 7% 20% 30% 20% 4	374
February	1st to 10th	Day	23% 8% 20% 25% 20% 4	346
	11th to 20th	Day	19% 7% 32% 26% 15% 1	415
	21st to end	Day	20% 12% 27% 32% 8% 1	346
March	1st to 10th	Day	26% 10% 29% 26% 7% 1	420
	11th to 20th	Day	22% 15% 26% 22% 14% 2	420
	21st to end	Day	19% 11% 34% 26% 10% 1	462
April	1st to 10th	Day	19% 15% 28% 25% 12% 2	420
	11th to 20th	Day	17% 16% 31% 27% 8% 2	412
	21st to end	Day	9% 14% 32% 26% 15% 4	420
May	1st to 10th	Day	10% 17% 30% 27% 11% 4	423
	11th to 20th	Day	9% 15% 29% 29% 14% 5%	448
	21st to end	Day	9% 11% 26% 32% 14% 6%	485
June	1st to 10th	Day	5% 11% 29% 34% 15% 6%	450
	11th to 20th	Day	3 11% 30% 37% 13% 6%	450
	21st to end	Day	3 7% 25% 38% 20% 8%	450
July	1st to 10th	Day	2 24% 50% 16% 8%	446
	11th to 20th	Day	2 18% 47% 23% 10%	444
	21st to end	Day	1 1 17% 49% 21% 11%	487
August	1st to 10th	Day	4 4 20% 47% 16% 9%	447
	11th to 20th	Day	1 2 27% 41% 19% 10%	437
	21st to end	Day	1 2 21% 45% 22% 9%	495
September	1st to 10th	Day	3 2 20% 47% 22% 6%	450
	11th to 20th	Day	5% 6% 28% 35% 21% 4	450
	21st to end	Day	3 6% 22% 45% 21% 3	450
October	1st to 10th	Day	4 10% 27% 34% 22% 4	450
	11th to 20th	Day	7% 7% 21% 34% 26% 5%	450
	21st to end	Day	8% 6% 21% 34% 26% 4	495
November	1st to 10th	Day	11% 8% 20% 29% 27% 5%	284
	11th to 20th	Day	9% 5% 20% 32% 27% 7%	270
	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	15% 4 13% 37% 24% 7%	732
	21st to end	Night	20% 2 13% 36% 22% 7%	792
February	1st to 10th	Night	18% 2 15% 37% 22% 6%	720
	11th to 20th	Night	18% 3 15% 33% 21% 9%	704
	21st to end	Night	23% 3 13% 42% 16% 3	592
March	1st to 10th	Night	23% 4 16% 34% 18% 4	720
	11th to 20th	Night	20% 4 16% 29% 24% 7%	720
	21st to end	Night	19% 3 17% 38% 22% 2	792
April	1st to 10th	Night	15% 4 16% 40% 23% 3	720
	11th to 20th	Night	13% 4 20% 35% 22% 7%	711
	21st to end	Night	8% 4 17% 39% 26% 6%	720
May	1st to 10th	Night	7% 4 19% 42% 22% 6%	691
	11th to 20th	Night	5% 3 19% 37% 32% 3	422
	21st to end	Night	5% 2 15% 39% 35% 4	389
June	1st to 10th	Night	6% 2 13% 40% 33% 6%	360
	11th to 20th	Night	1 1 13% 44% 37% 4	360
	21st to end	Night	1 1 11% 42% 42% 4	360
July	1st to 10th	Night	4 45% 46% 5%	350
	11th to 20th	Night	2 3 41% 47% 7%	348
	21st to end	Night	2 3 31% 52% 12%	561
August	1st to 10th	Night	2 1 5% 34% 48% 11%	573
	11th to 20th	Night	1 1 6% 42% 42% 8%	712
	21st to end	Night	1 1 4 37% 50% 7%	792
September	1st to 10th	Night	1 5% 40% 45% 9%	720
	11th to 20th	Night	3 1 9% 40% 38% 10%	720
	21st to end	Night	2 1 9% 38% 39% 10%	720
October	1st to 10th	Night	5% 1 10% 44% 32% 7%	720
	11th to 20th	Night	6% 3 9% 39% 34% 10%	720
	21st to end	Night	6% 1 12% 36% 31% 14%	792
November	1st to 10th	Night	12% 2 8% 36% 30% 11%	740
	11th to 20th	Night	11% 1 13% 39% 29% 7%	760
	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 2024-01-10 16:35:24. Version ac07

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