Prineville Reservoir State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prineville Reservoir State Park 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	7% 8% 3 6% 4 4 4 3 5% 6% 50%	105419
	Night	8% 10% 3 7% 4 4 4 3 5% 6% 46%	102443
Transparency	Day	34% 6% 10% 20% 18% 11%	105162
	Night	38% 7% 12% 21% 16% 7%	102289
Seeing	Day	12% 12% 25% 27% 19% 6%	14660
	Night	13% 7% 19% 37% 21% 3	23723

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	14% 18% 4 10% 6% 6% 5% 5% 5% 7% 20%	2539
	11th to 20th	Day	17% 19% 4 9% 6% 5% 5% 4 5% 6% 21%	2540
	21st to end	Day	12% 15% 4 9% 5% 5% 5% 4 6% 7% 26%	2957
February	1st to 10th	Day	10% 14% 4 8% 5% 5% 5% 5% 6% 8% 29%	1710
	11th to 20th	Day	10% 14% 4 8% 5% 5% 6% 3 6% 7% 31%	1698
	21st to end	Day	8% 16% 5% 9% 7% 6% 5% 4 6% 8% 26%	1570
March	1st to 10th	Day	7% 12% 6% 10% 6% 5% 6% 5% 7% 7% 30%	3138
	11th to 20th	Day	6% 12% 3 6% 4 4 4 3 4 6% 48%	3476
	21st to end	Day	9% 16% 4 11% 7% 6% 5% 4 6% 6% 25%	4032
April	1st to 10th	Day	10% 16% 5% 10% 5% 5% 5% 4 5% 5% 30%	2280
	11th to 20th	Day	10% 12% 4 8% 6% 5% 4 3 6% 6% 36%	2249
	21st to end	Day	9% 10% 3 7% 4 4 5% 5% 6% 8% 40%	2324
May	1st to 10th	Day	11% 12% 3 6% 4 4 4 4 5% 6% 43%	4420
	11th to 20th	Day	7% 6% 2 4 3 2 3 2 4 6% 61%	4377
	21st to end	Day	9% 9% 2 6% 5% 4 4 4 5% 7% 46%	4813
June	1st to 10th	Day	12% 9% 2 6% 5% 4 5% 4 5% 7% 41%	2660
	11th to 20th	Day	9% 6% 2 5% 4 3 3 4 5% 7% 52%	2660
	21st to end	Day	4 3 2 3 3 2 3 4 4 5% 66%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 2 3 3 84%	4420
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 4 79%	4420
	21st to end	Day	1 2 1 2 2 2 2 2 4 4 79%	4790
August	1st to 10th	Day	3 3 1 4 3 2 3 3 4 6% 67%	4256
	11th to 20th	Day	2 2 1 3 2 3 3 2 4 5% 73%	3948
	21st to end	Day	3 3 1 3 3 2 3 2 3 5% 72%	4180
September	1st to 10th	Day	2 2 1 2 2 2 3 3 4 5% 75%	2280
	11th to 20th	Day	5% 4 2 5% 4 3 4 3 5% 7% 59%	2280
	21st to end	Day	7% 5% 2 5% 3 3 3 3 4 6% 59%	2047
October	1st to 10th	Day	7% 5% 2 4 3 3 3 3 3 5% 63%	3180
	11th to 20th	Day	7% 7% 2 6% 4 4 6% 3 6% 9% 46%	3161
	21st to end	Day	10% 10% 3 8% 5% 5% 5% 4 6% 6% 37%	3245
November	1st to 10th	Day	14% 12% 3 8% 5% 5% 4 4 6% 7% 34%	1764
	11th to 20th	Day	14% 11% 4 8% 5% 4 6% 6% 7% 7% 29%	1583
	21st to end	Day	10% 13% 3 7% 5% 5% 4 4 6% 7% 35%	1520
December	1st to 10th	Day	10% 11% 3 8% 5% 5% 5% 4 6% 6% 36%	1520
	11th to 20th	Day	11% 13% 4 9% 6% 6% 5% 5% 6% 8% 26%	1928
	21st to end	Day	11% 16% 5% 10% 6% 5% 5% 4 6% 7% 25%	2794
January	1st to 10th	Night	11% 19% 5% 11% 6% 6% 6% 3 6% 6% 21%	4406
	11th to 20th	Night	17% 20% 4 9% 5% 5% 4 4 5% 6% 21%	4420
	21st to end	Night	14% 15% 4 9% 5% 6% 6% 4 6% 6% 25%	4703
February	1st to 10th	Night	11% 15% 5% 9% 6% 4 5% 3 6% 6% 29%	2470
	11th to 20th	Night	8% 13% 5% 8% 5% 4 6% 4 5% 7% 34%	2368
	21st to end	Night	9% 15% 5% 9% 7% 5% 5% 4 5% 8% 28%	1884
March	1st to 10th	Night	6% 14% 4 9% 5% 5% 5% 4 7% 8% 32%	3736
	11th to 20th	Night	6% 9% 3 7% 4 4 3 3 5% 5% 50%	3502
	21st to end	Night	8% 15% 4 10% 7% 7% 7% 5% 6% 6% 24%	3620
April	1st to 10th	Night	11% 17% 4 8% 5% 4 4 3 5% 7% 32%	1900
	11th to 20th	Night	10% 13% 4 7% 4 4 5% 4 6% 6% 37%	1879
	21st to end	Night	8% 14% 3 7% 4 4 4 4 5% 8% 38%	1852
May	1st to 10th	Night	10% 15% 4 7% 4 3 4 3 4 5% 40%	2540
	11th to 20th	Night	7% 4 2 3 3 3 3 2 3 6% 63%	2516
	21st to end	Night	12% 11% 2 5% 3 3 2 2 5% 5% 50%	2762
June	1st to 10th	Night	12% 7% 3 6% 4 4 4 4 6% 6% 46%	1520
	11th to 20th	Night	9% 7% 2 5% 3 3 2 3 4 7% 56%	1520
	21st to end	Night	4 4 1 3 3 2 3 3 4 5% 68%	1520
July	1st to 10th	Night	1 1 1 1 2 2 2 2 2 4 84%	2540
	11th to 20th	Night	2 2 1 2 2 2 1 2 3 4 80%	2540
	21st to end	Night	1 2 1 2 2 2 2 1 3 3 81%	2761
August	1st to 10th	Night	2 3 2 5% 2 2 3 3 5% 6% 67%	2676
	11th to 20th	Night	2 2 1 3 2 2 2 2 4 5% 76%	2892
	21st to end	Night	2 3 1 2 2 2 2 2 4 4 76%	3498
September	1st to 10th	Night	2 2 2 2 2 2 2 4 5% 77%	1900
	11th to 20th	Night	4 3 1 5% 3 3 2 4 5% 6% 62%	1900
	21st to end	Night	7% 6% 1 4 2 2 4 3 5% 5% 60%	2128
October	1st to 10th	Night	6% 5% 2 4 2 2 2 2 3 4 69%	3800
	11th to 20th	Night	9% 6% 2 5% 3 3 4 3 5% 8% 51%	3777
	21st to end	Night	9% 8% 3 8% 5% 5% 5% 5% 5% 7% 41%	4304
November	1st to 10th	Night	14% 13% 3 7% 5% 4 5% 4 4 6% 35%	2535
	11th to 20th	Night	15% 11% 3 8% 6% 5% 5% 4 6% 6% 31%	2616
	21st to end	Night	11% 13% 3 6% 4 4 4 4 6% 7% 39%	2660
December	1st to 10th	Night	11% 13% 3 8% 6% 4 3 4 5% 8% 35%	2660
	11th to 20th	Night	10% 14% 5% 9% 7% 6% 6% 4 6% 6% 26%	3276
	21st to end	Night	11% 15% 5% 9% 6% 5% 5% 4 5% 6% 29%	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	58% 10% 14% 15% 3	2539
	11th to 20th	Day	61% 8% 12% 12% 4 2	2540
	21st to end	Day	55% 10% 14% 15% 5% 1	2957
February	1st to 10th	Day	50% 8% 15% 19% 7%	1710
	11th to 20th	Day	49% 9% 14% 16% 9% 3	1707
	21st to end	Day	53% 10% 15% 13% 7% 1	1570
March	1st to 10th	Day	47% 9% 12% 17% 14% 1	3138
	11th to 20th	Day	36% 6% 12% 33% 13%	3476
	21st to end	Day	54% 10% 12% 18% 5%	4032
April	1st to 10th	Day	53% 7% 13% 16% 9% 1	2280
	11th to 20th	Day	47% 6% 12% 18% 13% 3	2252
	21st to end	Day	40% 7% 14% 24% 12% 2	2324
May	1st to 10th	Day	38% 7% 10% 27% 17% 1	4420
	11th to 20th	Day	24% 5% 7% 26% 33% 5%	4380
	21st to end	Day	36% 8% 15% 27% 12% 1	4814
June	1st to 10th	Day	41% 7% 10% 28% 13% 1	2660
	11th to 20th	Day	31% 4 11% 30% 20% 4	2660
	21st to end	Day	20% 4 9% 26% 30% 11%	2660
July	1st to 10th	Day	8% 2 5% 12% 20% 53%	4351
	11th to 20th	Day	10% 3 4 8% 21% 53%	4345
	21st to end	Day	10% 2 5% 15% 37% 32%	4639
August	1st to 10th	Day	18% 3 5% 14% 33% 27%	4240
	11th to 20th	Day	14% 3 5% 25% 35% 18%	3987
	21st to end	Day	16% 2 7% 26% 27% 22%	4179
September	1st to 10th	Day	12% 3 5% 24% 32% 24%	2280
	11th to 20th	Day	25% 6% 9% 22% 25% 14%	2280
	21st to end	Day	28% 4 9% 25% 23% 11%	2047
October	1st to 10th	Day	25% 4 9% 19% 26% 18%	3180
	11th to 20th	Day	33% 5% 15% 25% 18% 4	3161
	21st to end	Day	44% 7% 9% 22% 17% 2	3245
November	1st to 10th	Day	48% 7% 12% 20% 12% 1	1764
	11th to 20th	Day	49% 12% 15% 15% 9%	1583
	21st to end	Day	47% 7% 15% 15% 15% 1	1520
December	1st to 10th	Day	46% 10% 13% 20% 9% 1	1520
	11th to 20th	Day	54% 9% 14% 15% 7%	1928
	21st to end	Day	56% 9% 12% 18% 4 1	2794
January	1st to 10th	Night	60% 10% 13% 12% 4	4406
	11th to 20th	Night	61% 8% 11% 12% 5% 3	4420
	21st to end	Night	56% 9% 14% 13% 7% 1	4703
February	1st to 10th	Night	53% 8% 16% 14% 8%	2470
	11th to 20th	Night	47% 10% 15% 17% 9% 3	2370
	21st to end	Night	53% 9% 11% 18% 7% 1	1884
March	1st to 10th	Night	44% 8% 10% 24% 12% 1	3736
	11th to 20th	Night	34% 8% 12% 32% 14%	3502
	21st to end	Night	53% 11% 15% 16% 5%	3620
April	1st to 10th	Night	50% 7% 17% 17% 8% 1	1900
	11th to 20th	Night	45% 7% 15% 20% 12% 2	1879
	21st to end	Night	43% 8% 15% 23% 10% 1	1852
May	1st to 10th	Night	40% 9% 13% 26% 12%	2540
	11th to 20th	Night	24% 4 11% 37% 23% 2	2516
	21st to end	Night	34% 8% 26% 26% 6%	2762
June	1st to 10th	Night	38% 7% 12% 29% 13% 1	1520
	11th to 20th	Night	29% 6% 14% 33% 15% 3	1520
	21st to end	Night	19% 4 12% 30% 27% 8%	1520
July	1st to 10th	Night	7% 3 6% 14% 24% 46%	2500
	11th to 20th	Night	11% 2 4 14% 22% 47%	2492
	21st to end	Night	11% 1 3 17% 37% 31%	2674
August	1st to 10th	Night	18% 3 6% 17% 34% 22%	2668
	11th to 20th	Night	12% 2 6% 39% 30% 11%	2919
	21st to end	Night	13% 3 8% 29% 28% 19%	3498
September	1st to 10th	Night	11% 3 6% 25% 36% 20%	1900
	11th to 20th	Night	21% 5% 10% 25% 26% 13%	1900
	21st to end	Night	26% 4 9% 24% 23% 14%	2128
October	1st to 10th	Night	23% 3 7% 21% 32% 14%	3800
	11th to 20th	Night	32% 5% 18% 22% 19% 4	3777
	21st to end	Night	40% 7% 11% 26% 15% 2	4304
November	1st to 10th	Night	50% 6% 12% 17% 14% 2	2535
	11th to 20th	Night	51% 9% 13% 19% 9% 1	2616
	21st to end	Night	42% 8% 13% 17% 18% 2	2660
December	1st to 10th	Night	47% 10% 14% 19% 10% 1	2660
	11th to 20th	Night	55% 9% 13% 15% 8%	3276
	21st to end	Night	53% 10% 12% 18% 6% 1	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	23% 16% 29% 17% 15% 1	180
	11th to 20th	Day	22% 13% 28% 21% 14% 3	180
	21st to end	Day	16% 11% 29% 26% 15% 2	296
February	1st to 10th	Day	19% 16% 23% 28% 13% 1	370
	11th to 20th	Day	15% 16% 34% 23% 12% 1	380
	21st to end	Day	15% 15% 27% 33% 9% 1	382
March	1st to 10th	Day	16% 15% 29% 30% 10% 1	460
	11th to 20th	Day	16% 14% 26% 27% 14% 3	460
	21st to end	Day	17% 19% 26% 27% 10% 1	506
April	1st to 10th	Day	18% 19% 23% 25% 10% 4	460
	11th to 20th	Day	14% 18% 30% 23% 12% 4	452
	21st to end	Day	13% 17% 29% 22% 14% 4	460
May	1st to 10th	Day	14% 17% 26% 24% 15% 5%	463
	11th to 20th	Day	20% 12% 23% 19% 17% 8%	488
	21st to end	Day	14% 8% 25% 24% 20% 9%	529
June	1st to 10th	Day	10% 12% 25% 24% 21% 9%	490
	11th to 20th	Day	12% 16% 26% 25% 17% 5%	490
	21st to end	Day	4 10% 21% 28% 25% 11%	490
July	1st to 10th	Day	3 5% 26% 33% 22% 10%	486
	11th to 20th	Day	2 7% 27% 28% 26% 10%	484
	21st to end	Day	3 6% 26% 28% 24% 13%	531
August	1st to 10th	Day	3 6% 24% 28% 26% 13%	487
	11th to 20th	Day	1 6% 20% 29% 28% 16%	477
	21st to end	Day	6% 7% 21% 25% 28% 12%	539
September	1st to 10th	Day	3 4 20% 33% 28% 11%	490
	11th to 20th	Day	7% 9% 20% 29% 28% 7%	490
	21st to end	Day	10% 9% 21% 27% 26% 7%	490
October	1st to 10th	Day	14% 9% 20% 28% 21% 8%	490
	11th to 20th	Day	13% 13% 19% 28% 21% 6%	490
	21st to end	Day	16% 12% 27% 24% 17% 5%	424
November	1st to 10th	Day	17% 12% 23% 34% 13% 1	300
	11th to 20th	Day	15% 14% 24% 31% 13% 3	208
	21st to end	Day	14% 14% 23% 36% 12% 1	180
December	1st to 10th	Day	17% 14% 29% 25% 9% 6%	180
	11th to 20th	Day	22% 14% 24% 33% 6% 1	180
	21st to end	Day	18% 14% 24% 31% 12% 2	198
January	1st to 10th	Night	18% 12% 26% 28% 15% 3	760
	11th to 20th	Night	17% 12% 24% 26% 20% 2	760
	21st to end	Night	18% 7% 18% 36% 17% 3	836
February	1st to 10th	Night	16% 9% 25% 34% 15% 1	760
	11th to 20th	Night	15% 8% 24% 37% 16% 2	744
	21st to end	Night	16% 11% 23% 37% 12% 1	628
March	1st to 10th	Night	14% 12% 25% 33% 14% 1	760
	11th to 20th	Night	15% 8% 21% 36% 18% 2	760
	21st to end	Night	15% 10% 25% 34% 15%	836
April	1st to 10th	Night	18% 10% 22% 31% 18% 2	760
	11th to 20th	Night	16% 9% 25% 31% 17% 3	751
	21st to end	Night	16% 9% 20% 37% 17% 1	712
May	1st to 10th	Night	11% 6% 20% 41% 20% 1	380
	11th to 20th	Night	14% 4 15% 40% 26% 2	374
	21st to end	Night	18% 4 14% 38% 25% 2	411
June	1st to 10th	Night	13% 5% 16% 42% 23% 1	380
	11th to 20th	Night	11% 3 23% 43% 18% 1	380
	21st to end	Night	5% 2 16% 49% 27% 1	380
July	1st to 10th	Night	2 1 11% 52% 32% 1	370
	11th to 20th	Night	1 1 14% 58% 24% 2	368
	21st to end	Night	1 14% 54% 30% 1	416
August	1st to 10th	Night	2 1 9% 49% 35% 4	460
	11th to 20th	Night	2 1 8% 39% 43% 7%	605
	21st to end	Night	3 2 14% 45% 32% 4	836
September	1st to 10th	Night	3 2 12% 44% 35% 4	760
	11th to 20th	Night	6% 3 13% 38% 33% 7%	760
	21st to end	Night	10% 4 13% 37% 32% 5%	760
October	1st to 10th	Night	12% 3 14% 40% 28% 4	760
	11th to 20th	Night	13% 4 16% 39% 25% 4	760
	21st to end	Night	15% 6% 19% 37% 19% 5%	836
November	1st to 10th	Night	18% 8% 19% 40% 14% 1	780
	11th to 20th	Night	18% 9% 21% 35% 15% 2	764
	21st to end	Night	16% 9% 19% 35% 18% 3	760
December	1st to 10th	Night	17% 8% 21% 32% 20% 2	760
	11th to 20th	Night	17% 10% 24% 34% 13% 1	760
	21st to end	Night	22% 14% 25% 28% 11%	836

Page generated at 2024-11-08 19:45:40. Version ac07

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