Prineville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prineville clear sky chart from 2005-11-06 to 2024-11-02.

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% 8% 2 6% 4 4 4 3 5% 6% 50%	101531
	Night	9% 9% 3 6% 4 4 4 3 5% 6% 45%	97605
Transparency	Day	35% 4 9% 22% 18% 11%	101274
	Night	40% 4 12% 22% 15% 7%	97451
Seeing	Day	13% 10% 25% 27% 18% 7%	14623
	Night	14% 6% 17% 39% 22% 3	23663

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	15% 16% 4 9% 7% 6% 6% 4 6% 7% 20%	2539
	11th to 20th	Day	21% 17% 4 9% 5% 5% 5% 4 4 5% 21%	2540
	21st to end	Day	15% 14% 4 10% 6% 5% 5% 4 6% 6% 25%	2956
February	1st to 10th	Day	12% 14% 4 8% 6% 5% 4 5% 6% 8% 29%	1710
	11th to 20th	Day	11% 14% 3 10% 5% 4 4 4 6% 7% 32%	1689
	21st to end	Day	10% 15% 5% 9% 5% 5% 5% 5% 7% 7% 26%	1570
March	1st to 10th	Day	9% 14% 6% 10% 6% 5% 5% 4 6% 8% 28%	3138
	11th to 20th	Day	8% 11% 3 6% 4 4 3 3 4 7% 48%	3480
	21st to end	Day	9% 14% 4 10% 6% 6% 6% 4 6% 7% 26%	4029
April	1st to 10th	Day	11% 16% 4 9% 7% 4 5% 4 4 6% 29%	2280
	11th to 20th	Day	10% 13% 4 7% 6% 4 4 3 5% 7% 36%	2249
	21st to end	Day	8% 10% 3 7% 5% 3 5% 4 6% 8% 40%	2337
May	1st to 10th	Day	12% 9% 3 6% 4 4 4 3 5% 6% 44%	4420
	11th to 20th	Day	6% 5% 2 5% 3 3 3 3 4 5% 62%	4377
	21st to end	Day	9% 8% 2 5% 5% 4 5% 4 6% 7% 45%	4813
June	1st to 10th	Day	12% 8% 2 6% 5% 4 5% 4 5% 6% 42%	2660
	11th to 20th	Day	8% 6% 2 5% 4 4 4 3 5% 7% 52%	2660
	21st to end	Day	4 4 1 3 3 3 3 3 5% 5% 67%	2660
July	1st to 10th	Day	1 1 1 1 1 2 1 2 3 85%	4420
	11th to 20th	Day	2 1 2 2 1 2 2 3 3 82%	4420
	21st to end	Day	2 1 1 2 1 2 2 3 3 4 80%	4790
August	1st to 10th	Day	3 3 1 3 2 2 3 3 4 5% 70%	4256
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 6% 73%	3969
	21st to end	Day	3 3 1 3 2 2 3 2 3 5% 73%	4180
September	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 76%	2280
	11th to 20th	Day	5% 4 1 5% 3 4 3 3 5% 7% 60%	2280
	21st to end	Day	8% 5% 2 4 3 3 3 3 5% 6% 59%	2045
October	1st to 10th	Day	9% 7% 2 6% 3 3 4 3 4 7% 52%	1900
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 6% 7% 47%	1900
	21st to end	Day	14% 8% 2 7% 5% 4 4 4 5% 5% 43%	1976
November	1st to 10th	Day	14% 10% 4 9% 6% 4 5% 4 5% 8% 32%	1683
	11th to 20th	Day	16% 10% 2 8% 6% 5% 6% 5% 7% 7% 28%	1563
	21st to end	Day	12% 12% 2 8% 4 4 4 4 6% 8% 34%	1520
December	1st to 10th	Day	13% 10% 3 7% 4 4 5% 4 6% 8% 36%	1520
	11th to 20th	Day	14% 12% 4 8% 7% 5% 5% 6% 7% 8% 25%	1928
	21st to end	Day	13% 13% 5% 11% 6% 5% 5% 4 5% 7% 26%	2794
January	1st to 10th	Night	14% 16% 5% 10% 6% 6% 6% 4 6% 8% 21%	4406
	11th to 20th	Night	21% 18% 4 8% 6% 5% 5% 3 5% 5% 21%	4420
	21st to end	Night	16% 15% 4 9% 5% 5% 5% 4 5% 7% 24%	4703
February	1st to 10th	Night	12% 13% 4 9% 6% 5% 5% 4 6% 7% 29%	2470
	11th to 20th	Night	11% 13% 4 8% 4 4 5% 4 5% 8% 35%	2377
	21st to end	Night	10% 16% 5% 8% 7% 6% 5% 4 5% 7% 27%	1884
March	1st to 10th	Night	8% 13% 4 8% 5% 6% 5% 4 6% 8% 33%	3736
	11th to 20th	Night	7% 9% 2 7% 4 4 4 3 5% 5% 49%	3498
	21st to end	Night	8% 14% 4 9% 7% 6% 6% 6% 7% 8% 24%	3623
April	1st to 10th	Night	11% 14% 3 8% 5% 4 4 4 6% 7% 33%	1900
	11th to 20th	Night	11% 13% 4 7% 5% 5% 4 3 5% 7% 37%	1879
	21st to end	Night	10% 11% 2 7% 4 5% 4 4 7% 8% 38%	1841
May	1st to 10th	Night	10% 11% 2 7% 4 4 4 3 5% 7% 42%	2540
	11th to 20th	Night	6% 5% 2 3 3 3 4 2 4 6% 63%	2516
	21st to end	Night	10% 8% 2 5% 4 3 3 3 5% 7% 51%	2762
June	1st to 10th	Night	13% 6% 2 4 4 4 5% 3 5% 6% 47%	1520
	11th to 20th	Night	8% 5% 2 6% 4 3 3 3 5% 8% 56%	1520
	21st to end	Night	5% 4 1 3 3 2 3 3 4 5% 68%	1520
July	1st to 10th	Night	1 1 1 1 2 2 2 3 85%	2540
	11th to 20th	Night	2 1 1 2 2 1 2 2 3 3 81%	2540
	21st to end	Night	2 2 1 2 1 1 1 2 3 4 82%	2761
August	1st to 10th	Night	2 2 1 4 3 3 3 2 4 5% 70%	2676
	11th to 20th	Night	1 1 1 3 2 2 3 2 4 5% 76%	2870
	21st to end	Night	1 2 1 3 2 2 2 2 4 4 76%	3498
September	1st to 10th	Night	3 1 1 2 2 1 2 2 3 5% 78%	1900
	11th to 20th	Night	5% 4 2 4 3 3 4 3 4 6% 62%	1900
	21st to end	Night	7% 5% 2 4 3 3 4 3 4 6% 60%	2133
October	1st to 10th	Night	9% 6% 2 4 3 3 3 2 4 5% 58%	2280
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 52%	2280
	21st to end	Night	11% 9% 2 8% 5% 4 4 3 5% 6% 44%	2621
November	1st to 10th	Night	15% 11% 3 8% 6% 5% 5% 4 4 6% 33%	2418
	11th to 20th	Night	17% 10% 3 8% 6% 5% 6% 4 5% 7% 30%	2615
	21st to end	Night	12% 11% 3 7% 4 4 5% 4 6% 8% 38%	2660
December	1st to 10th	Night	12% 12% 3 8% 5% 4 4 4 6% 7% 35%	2660
	11th to 20th	Night	13% 14% 4 9% 7% 5% 6% 5% 6% 7% 25%	3276
	21st to end	Night	13% 14% 4 10% 6% 6% 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	62% 6% 14% 15% 3	2539
	11th to 20th	Day	65% 3 13% 13% 4 2	2540
	21st to end	Day	59% 4 14% 16% 5% 1	2956
February	1st to 10th	Day	52% 7% 15% 20% 6%	1710
	11th to 20th	Day	50% 7% 13% 19% 9% 2	1698
	21st to end	Day	54% 7% 15% 16% 7% 1	1570
March	1st to 10th	Day	50% 6% 8% 23% 12% 1	3138
	11th to 20th	Day	38% 4 10% 32% 16%	3480
	21st to end	Day	56% 5% 12% 21% 6%	4029
April	1st to 10th	Day	55% 6% 11% 18% 10% 1	2280
	11th to 20th	Day	49% 4 12% 19% 13% 3	2252
	21st to end	Day	41% 5% 12% 27% 12% 3	2337
May	1st to 10th	Day	40% 5% 8% 28% 18% 1	4420
	11th to 20th	Day	25% 4 6% 30% 30% 5%	4380
	21st to end	Day	36% 5% 17% 28% 13% 1	4814
June	1st to 10th	Day	42% 4 10% 29% 14% 2	2660
	11th to 20th	Day	32% 4 9% 30% 21% 4	2660
	21st to end	Day	21% 2 9% 28% 30% 11%	2660
July	1st to 10th	Day	8% 2 4 13% 22% 52%	4351
	11th to 20th	Day	10% 1 3 9% 21% 55%	4345
	21st to end	Day	11% 1 2 16% 38% 32%	4639
August	1st to 10th	Day	19% 2 3 14% 37% 26%	4240
	11th to 20th	Day	15% 1 4 29% 34% 17%	4008
	21st to end	Day	16% 2 5% 28% 28% 20%	4179
September	1st to 10th	Day	12% 2 4 26% 33% 23%	2280
	11th to 20th	Day	25% 3 8% 25% 25% 13%	2280
	21st to end	Day	28% 3 9% 26% 23% 10%	2045
October	1st to 10th	Day	35% 4 9% 21% 22% 10%	1900
	11th to 20th	Day	36% 3 14% 22% 19% 5%	1900
	21st to end	Day	43% 5% 11% 22% 18% 2	1976
November	1st to 10th	Day	50% 4 12% 23% 10% 1	1683
	11th to 20th	Day	52% 7% 16% 18% 8%	1563
	21st to end	Day	47% 5% 15% 17% 14% 1	1520
December	1st to 10th	Day	47% 7% 14% 23% 8% 1	1520
	11th to 20th	Day	55% 5% 19% 17% 4	1928
	21st to end	Day	57% 5% 14% 20% 3 1	2794
January	1st to 10th	Night	63% 5% 15% 12% 5%	4406
	11th to 20th	Night	65% 4 11% 12% 5% 3	4420
	21st to end	Night	59% 3 17% 14% 6%	4703
February	1st to 10th	Night	54% 6% 16% 16% 8%	2470
	11th to 20th	Night	47% 7% 15% 20% 9% 2	2379
	21st to end	Night	55% 6% 10% 20% 7% 1	1884
March	1st to 10th	Night	46% 6% 9% 28% 10% 1	3736
	11th to 20th	Night	36% 4 11% 38% 11%	3498
	21st to end	Night	57% 5% 16% 17% 5%	3623
April	1st to 10th	Night	50% 5% 17% 18% 8% 1	1900
	11th to 20th	Night	47% 5% 14% 20% 12% 1	1879
	21st to end	Night	43% 6% 14% 25% 10% 2	1841
May	1st to 10th	Night	42% 6% 10% 29% 12%	2540
	11th to 20th	Night	23% 4 10% 39% 22% 1	2516
	21st to end	Night	35% 4 28% 27% 6%	2762
June	1st to 10th	Night	38% 5% 13% 30% 13% 1	1520
	11th to 20th	Night	29% 4 14% 35% 15% 3	1520
	21st to end	Night	20% 3 11% 33% 26% 8%	1520
July	1st to 10th	Night	7% 2 7% 15% 26% 45%	2500
	11th to 20th	Night	12% 1 4 13% 22% 48%	2492
	21st to end	Night	10% 1 3 18% 36% 32%	2674
August	1st to 10th	Night	19% 2 3 18% 36% 23%	2668
	11th to 20th	Night	13% 1 5% 40% 30% 10%	2897
	21st to end	Night	14% 1 9% 30% 29% 17%	3498
September	1st to 10th	Night	12% 2 5% 28% 35% 18%	1900
	11th to 20th	Night	23% 3 9% 27% 25% 13%	1900
	21st to end	Night	27% 3 8% 25% 24% 13%	2133
October	1st to 10th	Night	30% 3 10% 23% 26% 8%	2280
	11th to 20th	Night	32% 4 15% 23% 22% 5%	2280
	21st to end	Night	41% 5% 12% 21% 18% 3	2621
November	1st to 10th	Night	52% 5% 9% 18% 14% 2	2418
	11th to 20th	Night	52% 6% 13% 21% 8%	2615
	21st to end	Night	44% 4 15% 20% 17% 1	2660
December	1st to 10th	Night	47% 6% 17% 20% 9% 1	2660
	11th to 20th	Night	57% 4 15% 17% 6%	3276
	21st to end	Night	56% 4 14% 20% 5% 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	34% 7% 27% 18% 12% 1	180
	11th to 20th	Day	21% 11% 29% 24% 11% 3	180
	21st to end	Day	18% 12% 27% 27% 14% 1	295
February	1st to 10th	Day	23% 13% 26% 25% 12% 1	370
	11th to 20th	Day	19% 15% 31% 23% 11% 1	377
	21st to end	Day	20% 13% 27% 29% 10% 1	382
March	1st to 10th	Day	21% 14% 28% 28% 8%	460
	11th to 20th	Day	18% 15% 25% 27% 14% 2	460
	21st to end	Day	22% 16% 26% 25% 11% 1	506
April	1st to 10th	Day	23% 15% 23% 24% 10% 4	460
	11th to 20th	Day	19% 14% 29% 24% 10% 5%	452
	21st to end	Day	14% 19% 26% 23% 13% 5%	460
May	1st to 10th	Day	17% 15% 25% 24% 15% 4	463
	11th to 20th	Day	19% 13% 23% 20% 18% 7%	488
	21st to end	Day	14% 10% 21% 26% 20% 10%	529
June	1st to 10th	Day	14% 11% 22% 23% 20% 10%	490
	11th to 20th	Day	11% 14% 29% 25% 17% 4	490
	21st to end	Day	4 7% 21% 33% 22% 12%	490
July	1st to 10th	Day	2 6% 28% 32% 21% 10%	486
	11th to 20th	Day	2 8% 26% 28% 25% 10%	484
	21st to end	Day	3 5% 28% 26% 25% 12%	531
August	1st to 10th	Day	4 5% 23% 29% 25% 14%	487
	11th to 20th	Day	2 4 20% 29% 27% 18%	477
	21st to end	Day	6% 6% 21% 26% 27% 14%	539
September	1st to 10th	Day	3 5% 21% 31% 28% 12%	490
	11th to 20th	Day	7% 6% 21% 31% 28% 7%	490
	21st to end	Day	10% 8% 19% 29% 26% 8%	490
October	1st to 10th	Day	13% 8% 21% 28% 22% 8%	490
	11th to 20th	Day	14% 9% 20% 27% 23% 8%	490
	21st to end	Day	19% 8% 25% 24% 20% 5%	425
November	1st to 10th	Day	16% 10% 25% 34% 13% 1	273
	11th to 20th	Day	18% 10% 26% 29% 14% 2	201
	21st to end	Day	17% 12% 23% 33% 12% 2	180
December	1st to 10th	Day	22% 8% 32% 23% 9% 6%	180
	11th to 20th	Day	24% 7% 33% 29% 7%	180
	21st to end	Day	20% 10% 26% 28% 13% 3	198
January	1st to 10th	Night	21% 9% 24% 29% 16% 2	760
	11th to 20th	Night	20% 9% 20% 29% 20% 2	760
	21st to end	Night	18% 6% 17% 39% 17% 3	836
February	1st to 10th	Night	17% 8% 21% 37% 15% 1	760
	11th to 20th	Night	17% 7% 20% 40% 15% 2	744
	21st to end	Night	18% 10% 19% 39% 13% 1	628
March	1st to 10th	Night	17% 11% 22% 35% 13% 1	760
	11th to 20th	Night	15% 8% 18% 38% 19% 1	760
	21st to end	Night	16% 10% 23% 36% 15% 1	836
April	1st to 10th	Night	18% 8% 19% 35% 18% 2	760
	11th to 20th	Night	17% 8% 22% 33% 17% 3	751
	21st to end	Night	16% 8% 19% 37% 18% 2	701
May	1st to 10th	Night	12% 5% 17% 43% 21% 1	380
	11th to 20th	Night	13% 5% 12% 43% 25% 2	374
	21st to end	Night	14% 4 12% 40% 27% 3	411
June	1st to 10th	Night	15% 3 13% 45% 21% 2	380
	11th to 20th	Night	10% 4 18% 46% 20% 1	380
	21st to end	Night	6% 2 14% 51% 27% 1	380
July	1st to 10th	Night	2 1 10% 50% 35% 1	370
	11th to 20th	Night	2 11% 60% 26% 2	368
	21st to end	Night	2 11% 52% 34% 2	416
August	1st to 10th	Night	2 1 5% 50% 37% 4	460
	11th to 20th	Night	2 1 6% 40% 43% 8%	596
	21st to end	Night	2 2 13% 46% 33% 4	836
September	1st to 10th	Night	3 2 11% 44% 36% 4	760
	11th to 20th	Night	5% 3 10% 42% 32% 8%	760
	21st to end	Night	9% 4 12% 39% 31% 5%	760
October	1st to 10th	Night	12% 3 11% 42% 28% 4	760
	11th to 20th	Night	13% 4 15% 40% 24% 4	760
	21st to end	Night	15% 5% 17% 40% 20% 4	836
November	1st to 10th	Night	19% 5% 17% 41% 15% 1	744
	11th to 20th	Night	19% 7% 20% 36% 16% 2	760
	21st to end	Night	18% 9% 17% 36% 17% 3	760
December	1st to 10th	Night	19% 5% 18% 35% 20% 2	760
	11th to 20th	Night	21% 6% 21% 35% 15% 2	760
	21st to end	Night	24% 10% 22% 31% 11% 1	836

Page generated at 2024-10-29 22:23:00. Version ac07

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