Crestview
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crestview clear sky chart from 2005-11-06 to 2024-11-03.

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	2 3 1 4 3 3 3 3 5% 7% 67%	101080
	Night	1 3 1 3 2 3 3 3 5% 7% 70%	98123
Transparency	Day	18% 4 8% 21% 27% 23%	100824
	Night	16% 4 9% 25% 28% 18%	97969
Seeing	Day	5% 17% 29% 27% 16% 6%	15155
	Night	3 9% 26% 34% 22% 6%	24627

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	1 2 2 4 3 3 3 3 6% 13% 60%	2539
	11th to 20th	Day	3 2 5% 4 5% 5% 5% 7% 10% 54%	2606
	21st to end	Day	1 5% 3 6% 4 4 4 4 7% 11% 50%	3146
February	1st to 10th	Day	1 3 2 4 2 4 3 3 6% 8% 64%	1826
	11th to 20th	Day	3 2 5% 4 4 4 4 6% 9% 58%	1850
	21st to end	Day	3 2 5% 4 3 4 4 6% 7% 62%	1570
March	1st to 10th	Day	4 2 6% 5% 6% 5% 4 8% 10% 49%	3138
	11th to 20th	Day	4 4 7% 3 2 3 3 5% 8% 61%	3330
	21st to end	Day	5% 3 5% 4 3 4 4 7% 9% 56%	4148
April	1st to 10th	Day	1 4 2 5% 3 4 3 4 6% 8% 60%	2280
	11th to 20th	Day	2 4 1 4 3 3 4 3 5% 7% 64%	2249
	21st to end	Day	1 5% 2 3 3 3 3 3 6% 7% 66%	2280
May	1st to 10th	Day	1 3 3 3 3 3 3 5% 6% 72%	4012
	11th to 20th	Day	2 4 1 3 3 3 4 3 4 5% 67%	4071
	21st to end	Day	3 5% 1 4 3 3 3 2 3 5% 68%	4800
June	1st to 10th	Day	4 3 1 4 3 3 3 3 5% 7% 63%	2660
	11th to 20th	Day	2 2 2 2 2 2 1 3 4 78%	2660
	21st to end	Day	3 3 1 3 2 2 3 2 4 4 74%	2660
July	1st to 10th	Day	2 1 1 2 2 2 2 2 3 4 79%	4420
	11th to 20th	Day	3 3 1 5% 4 4 4 3 5% 6% 62%	4420
	21st to end	Day	4 3 1 3 3 3 3 3 4 4 70%	4702
August	1st to 10th	Day	3 2 1 4 3 3 3 3 4 5% 69%	3854
	11th to 20th	Day	2 1 1 1 2 2 2 2 2 3 83%	3724
	21st to end	Day	2 1 1 2 1 1 2 1 2 3 84%	4180
September	1st to 10th	Day	3 2 1 2 2 2 3 2 3 4 75%	2280
	11th to 20th	Day	3 3 1 3 2 2 2 2 3 4 75%	2199
	21st to end	Day	1 2 1 2 2 2 2 2 3 5% 78%	2090
October	1st to 10th	Day	3 4 1 3 2 2 2 2 4 5% 72%	2024
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 5% 75%	1900
	21st to end	Day	1 2 1 3 1 2 2 2 4 6% 77%	2017
November	1st to 10th	Day	1 2 1 4 3 2 2 3 5% 8% 68%	1692
	11th to 20th	Day	1 1 2 1 2 2 3 5% 9% 73%	1710
	21st to end	Day	1 3 1 3 2 2 2 3 5% 9% 70%	1710
December	1st to 10th	Day	1 2 1 3 2 2 3 3 5% 10% 67%	1611
	11th to 20th	Day	3 1 6% 4 5% 5% 5% 8% 8% 54%	1928
	21st to end	Day	6% 3 5% 4 3 5% 4 6% 11% 53%	2794
January	1st to 10th	Night	3 3 6% 3 3 4 3 5% 8% 61%	4406
	11th to 20th	Night	2 1 4 4 4 4 4 8% 12% 57%	4354
	21st to end	Night	1 5% 2 5% 4 4 4 4 7% 10% 54%	4521
February	1st to 10th	Night	3 2 5% 4 3 3 4 5% 8% 63%	2352
	11th to 20th	Night	4 2 4 2 3 4 3 5% 9% 64%	2218
	21st to end	Night	2 2 4 4 3 3 3 5% 8% 66%	1884
March	1st to 10th	Night	3 3 6% 4 4 5% 4 7% 8% 56%	3736
	11th to 20th	Night	7% 3 6% 2 2 3 4 5% 7% 60%	3646
	21st to end	Night	4 2 5% 3 3 4 3 5% 8% 62%	3503
April	1st to 10th	Night	1 4 2 4 2 3 3 4 4 7% 64%	1900
	11th to 20th	Night	1 3 1 3 3 2 3 3 5% 8% 67%	1879
	21st to end	Night	1 5% 2 3 2 3 3 2 4 4 71%	1900
May	1st to 10th	Night	1 2 1 2 2 1 2 2 4 5% 77%	2961
	11th to 20th	Night	2 2 1 3 3 3 2 2 3 5% 75%	2834
	21st to end	Night	3 3 1 2 2 2 2 2 4 5% 75%	2771
June	1st to 10th	Night	2 2 1 3 2 3 3 3 6% 7% 67%	1520
	11th to 20th	Night	2 1 2 1 1 1 2 3 4 82%	1520
	21st to end	Night	1 2 1 2 2 1 2 1 3 3 83%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 3 89%	2540
	11th to 20th	Night	2 3 1 4 3 3 3 3 5% 5% 67%	2540
	21st to end	Night	2 2 1 2 2 2 2 3 4 79%	2848
August	1st to 10th	Night	2 1 1 2 2 2 2 2 3 6% 77%	3091
	11th to 20th	Night	1 1 2 1 2 2 1 2 3 85%	3126
	21st to end	Night	1 1 1 1 1 1 2 3 89%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 2 88%	1900
	11th to 20th	Night	1 2 1 2 1 2 2 2 3 4 80%	1980
	21st to end	Night	1 2 2 1 2 2 1 3 4 82%	2090
October	1st to 10th	Night	3 4 1 2 2 1 2 2 3 3 77%	2152
	11th to 20th	Night	1 2 1 2 1 2 2 2 4 5% 79%	2280
	21st to end	Night	1 2 1 2 1 2 2 2 3 5% 80%	2579
November	1st to 10th	Night	1 2 1 2 2 2 3 2 4 7% 75%	2431
	11th to 20th	Night	2 1 2 2 2 2 3 4 8% 74%	2470
	21st to end	Night	3 1 4 2 3 3 3 4 7% 70%	2470
December	1st to 10th	Night	2 2 4 2 3 4 2 6% 9% 67%	2565
	11th to 20th	Night	2 2 4 4 4 4 5% 9% 11% 55%	3276
	21st to end	Night	1 6% 3 7% 4 4 5% 4 8% 10% 49%	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	18% 6% 16% 29% 26% 5%	2539
	11th to 20th	Day	26% 4 18% 24% 20% 8%	2606
	21st to end	Day	29% 5% 13% 24% 23% 5%	3146
February	1st to 10th	Day	19% 5% 13% 23% 27% 13%	1826
	11th to 20th	Day	22% 5% 10% 25% 30% 10%	1860
	21st to end	Day	22% 9% 10% 24% 27% 7%	1570
March	1st to 10th	Day	31% 5% 8% 27% 22% 8%	3138
	11th to 20th	Day	23% 6% 14% 38% 15% 4	3330
	21st to end	Day	25% 8% 13% 28% 23% 3	4148
April	1st to 10th	Day	23% 6% 13% 29% 19% 9%	2280
	11th to 20th	Day	21% 5% 12% 30% 23% 9%	2252
	21st to end	Day	19% 5% 13% 33% 25% 5%	2280
May	1st to 10th	Day	14% 5% 8% 29% 31% 13%	4012
	11th to 20th	Day	17% 4 6% 27% 36% 10%	4074
	21st to end	Day	19% 3 6% 29% 39% 4	4801
June	1st to 10th	Day	22% 3 9% 22% 32% 12%	2660
	11th to 20th	Day	12% 1 6% 18% 38% 25%	2660
	21st to end	Day	14% 3 2 11% 33% 36%	2660
July	1st to 10th	Day	10% 2 2 6% 15% 65%	4351
	11th to 20th	Day	20% 4 3 9% 20% 44%	4345
	21st to end	Day	17% 2 4 13% 19% 45%	4553
August	1st to 10th	Day	16% 2 2 10% 26% 44%	3839
	11th to 20th	Day	8% 2 1 6% 20% 62%	3760
	21st to end	Day	8% 1 2 8% 29% 52%	4179
September	1st to 10th	Day	14% 2 3 10% 29% 43%	2280
	11th to 20th	Day	14% 3 2 18% 31% 30%	2199
	21st to end	Day	12% 2 2 18% 36% 31%	2090
October	1st to 10th	Day	17% 2 4 18% 31% 27%	2024
	11th to 20th	Day	14% 3 3 19% 37% 24%	1900
	21st to end	Day	10% 4 5% 21% 39% 20%	2017
November	1st to 10th	Day	15% 4 9% 25% 32% 16%	1692
	11th to 20th	Day	10% 4 11% 27% 34% 14%	1710
	21st to end	Day	15% 4 10% 24% 33% 14%	1710
December	1st to 10th	Day	15% 6% 12% 27% 27% 12%	1611
	11th to 20th	Day	23% 7% 19% 25% 17% 9%	1928
	21st to end	Day	27% 5% 13% 24% 22% 9%	2794
January	1st to 10th	Night	20% 5% 11% 32% 25% 6%	4406
	11th to 20th	Night	20% 4 17% 31% 20% 8%	4354
	21st to end	Night	25% 5% 14% 29% 21% 7%	4521
February	1st to 10th	Night	20% 5% 11% 26% 24% 13%	2352
	11th to 20th	Night	19% 5% 10% 25% 28% 12%	2219
	21st to end	Night	18% 7% 10% 29% 28% 8%	1884
March	1st to 10th	Night	25% 5% 9% 31% 21% 9%	3736
	11th to 20th	Night	23% 6% 13% 33% 20% 5%	3646
	21st to end	Night	21% 7% 14% 31% 24% 3	3503
April	1st to 10th	Night	22% 5% 13% 32% 21% 7%	1900
	11th to 20th	Night	18% 5% 13% 30% 25% 10%	1879
	21st to end	Night	17% 4 16% 38% 21% 4	1900
May	1st to 10th	Night	12% 3 7% 36% 35% 7%	2961
	11th to 20th	Night	14% 2 7% 32% 37% 7%	2835
	21st to end	Night	14% 3 8% 36% 36% 4	2771
June	1st to 10th	Night	16% 4 9% 30% 33% 7%	1520
	11th to 20th	Night	8% 2 8% 22% 38% 21%	1520
	21st to end	Night	9% 1 3 15% 37% 35%	1520
July	1st to 10th	Night	4 1 2 7% 19% 68%	2500
	11th to 20th	Night	17% 3 2 12% 28% 38%	2492
	21st to end	Night	10% 2 4 19% 24% 42%	2759
August	1st to 10th	Night	10% 1 4 13% 32% 39%	3082
	11th to 20th	Night	7% 2 1 10% 22% 58%	3156
	21st to end	Night	4 2 2 11% 40% 42%	3498
September	1st to 10th	Night	6% 1 2 13% 40% 38%	1900
	11th to 20th	Night	10% 2 5% 19% 40% 23%	1980
	21st to end	Night	9% 2 3 23% 38% 25%	2090
October	1st to 10th	Night	14% 3 6% 20% 36% 21%	2152
	11th to 20th	Night	10% 4 5% 22% 38% 21%	2280
	21st to end	Night	10% 3 6% 24% 39% 19%	2579
November	1st to 10th	Night	10% 6% 10% 26% 33% 14%	2431
	11th to 20th	Night	11% 4 11% 26% 35% 13%	2470
	21st to end	Night	16% 4 11% 25% 32% 12%	2470
December	1st to 10th	Night	16% 6% 14% 26% 27% 11%	2565
	11th to 20th	Night	19% 7% 19% 26% 21% 8%	3276
	21st to end	Night	31% 4 11% 22% 23% 9%	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	7% 24% 32% 24% 9% 4	180
	11th to 20th	Day	4 24% 26% 23% 18% 6%	220
	21st to end	Day	3 17% 28% 31% 16% 5%	407
February	1st to 10th	Day	3 25% 31% 22% 14% 6%	426
	11th to 20th	Day	4 20% 33% 27% 14% 1	455
	21st to end	Day	6% 24% 31% 27% 12% 1	382
March	1st to 10th	Day	5% 26% 34% 25% 7% 2	460
	11th to 20th	Day	7% 27% 28% 21% 14% 3	460
	21st to end	Day	7% 27% 35% 23% 8%	506
April	1st to 10th	Day	7% 23% 33% 23% 11% 3	460
	11th to 20th	Day	10% 24% 33% 21% 10% 2	452
	21st to end	Day	7% 22% 30% 25% 12% 5%	460
May	1st to 10th	Day	9% 22% 32% 21% 10% 5%	463
	11th to 20th	Day	10% 20% 30% 22% 12% 6%	488
	21st to end	Day	9% 18% 25% 24% 19% 6%	529
June	1st to 10th	Day	6% 16% 32% 23% 17% 7%	490
	11th to 20th	Day	5% 21% 31% 22% 13% 7%	490
	21st to end	Day	2 14% 32% 31% 14% 6%	490
July	1st to 10th	Day	3 7% 32% 31% 20% 8%	486
	11th to 20th	Day	4 6% 26% 35% 20% 9%	484
	21st to end	Day	7% 7% 26% 32% 18% 10%	531
August	1st to 10th	Day	4 10% 29% 29% 21% 7%	487
	11th to 20th	Day	4 11% 27% 29% 20% 9%	477
	21st to end	Day	4 7% 26% 35% 20% 8%	539
September	1st to 10th	Day	5% 10% 23% 33% 22% 6%	490
	11th to 20th	Day	7% 14% 26% 29% 19% 4	490
	21st to end	Day	5% 12% 25% 35% 18% 5%	490
October	1st to 10th	Day	5% 14% 29% 28% 19% 5%	490
	11th to 20th	Day	4 15% 23% 35% 18% 5%	490
	21st to end	Day	4 16% 30% 26% 18% 6%	466
November	1st to 10th	Day	7% 16% 25% 17% 25% 10%	276
	11th to 20th	Day	1 20% 20% 32% 18% 9%	270
	21st to end	Day	1 14% 27% 29% 23% 6%	270
December	1st to 10th	Day	6% 14% 28% 27% 17% 7%	223
	11th to 20th	Day	3 21% 29% 26% 16% 6%	180
	21st to end	Day	4 25% 26% 27% 12% 6%	198
January	1st to 10th	Night	4 11% 34% 25% 18% 9%	760
	11th to 20th	Night	1 13% 30% 34% 15% 7%	760
	21st to end	Night	3 10% 31% 33% 17% 6%	836
February	1st to 10th	Night	2 12% 31% 33% 19% 4	760
	11th to 20th	Night	3 13% 31% 30% 18% 5%	744
	21st to end	Night	1 18% 33% 33% 11% 4	628
March	1st to 10th	Night	3 16% 35% 29% 12% 5%	760
	11th to 20th	Night	3 14% 32% 27% 18% 6%	760
	21st to end	Night	2 17% 38% 28% 13% 2	836
April	1st to 10th	Night	4 13% 34% 30% 16% 3	760
	11th to 20th	Night	3 15% 31% 31% 15% 5%	751
	21st to end	Night	4 10% 33% 31% 17% 6%	760
May	1st to 10th	Night	4 10% 31% 33% 18% 4	632
	11th to 20th	Night	3 9% 30% 37% 18% 3	561
	21st to end	Night	6% 7% 24% 33% 25% 5%	420
June	1st to 10th	Night	2 4 23% 39% 30% 2	380
	11th to 20th	Night	3 4 24% 41% 24% 3	380
	21st to end	Night	2 2 19% 48% 27% 2	380
July	1st to 10th	Night	1 1 13% 45% 37% 2	370
	11th to 20th	Night	2 1 14% 45% 35% 3	368
	21st to end	Night	3 8% 43% 41% 5%	467
August	1st to 10th	Night	3 2 14% 41% 34% 6%	706
	11th to 20th	Night	1 2 17% 43% 32% 5%	752
	21st to end	Night	2 2 15% 41% 34% 7%	836
September	1st to 10th	Night	2 2 15% 39% 36% 7%	760
	11th to 20th	Night	3 6% 18% 35% 31% 7%	760
	21st to end	Night	2 6% 17% 36% 31% 8%	760
October	1st to 10th	Night	4 6% 20% 36% 28% 6%	760
	11th to 20th	Night	3 8% 17% 38% 27% 8%	760
	21st to end	Night	3 6% 25% 30% 24% 12%	836
November	1st to 10th	Night	2 9% 23% 30% 26% 10%	748
	11th to 20th	Night	2 8% 29% 34% 20% 6%	760
	21st to end	Night	2 10% 27% 31% 24% 5%	760
December	1st to 10th	Night	2 11% 31% 34% 16% 6%	760
	11th to 20th	Night	2 15% 34% 31% 15% 3	760
	21st to end	Night	2 16% 35% 29% 14% 3	836

Page generated at 2024-10-31 00:39:28. Version ac07

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