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 2024-11-25.

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	10% 6% 2 6% 5% 5% 5% 5% 7% 8% 41%	100906
	Night	10% 6% 2 6% 4 4 4 4 6% 8% 44%	98545
Transparency	Day	38% 6% 13% 18% 17% 9%	104834
	Night	36% 6% 13% 17% 19% 9%	102755
Seeing	Day	12% 9% 21% 24% 20% 13%	14715
	Night	12% 6% 21% 30% 24% 6%	24662

By Month

Percentage Cloud Cover SE (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% 6% 2 5% 4 4 4 4 5% 8% 45%	2840
	11th to 20th	Day	11% 5% 1 4 3 3 3 4 6% 8% 54%	3160
	21st to end	Day	23% 7% 2 6% 3 4 4 3 4 6% 39%	3476
February	1st to 10th	Day	16% 7% 3 6% 4 4 4 3 5% 6% 43%	1900
	11th to 20th	Day	16% 6% 2 6% 3 4 3 4 5% 7% 44%	1848
	21st to end	Day	15% 8% 2 6% 5% 6% 4 4 6% 6% 39%	1570
March	1st to 10th	Day	19% 8% 3 7% 4 4 4 4 6% 6% 36%	3120
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 43%	3374
	21st to end	Day	14% 5% 2 5% 4 5% 4 4 6% 7% 44%	3932
April	1st to 10th	Day	13% 6% 2 6% 5% 3 4 4 5% 7% 46%	2280
	11th to 20th	Day	12% 6% 2 6% 5% 5% 4 3 5% 7% 45%	2254
	21st to end	Day	7% 4 2 5% 5% 4 3 3 5% 6% 56%	2280
May	1st to 10th	Day	8% 5% 2 6% 4 5% 4 5% 7% 8% 47%	3883
	11th to 20th	Day	14% 6% 3 6% 5% 4 5% 4 6% 7% 40%	4081
	21st to end	Day	5% 4 2 6% 5% 5% 5% 5% 6% 10% 47%	4476
June	1st to 10th	Day	8% 7% 3 9% 7% 7% 6% 6% 8% 10% 29%	2470
	11th to 20th	Day	5% 4 2 6% 5% 7% 9% 6% 9% 11% 36%	2470
	21st to end	Day	6% 6% 2 8% 7% 8% 9% 6% 9% 10% 30%	2470
July	1st to 10th	Day	6% 6% 3 9% 7% 8% 8% 7% 11% 13% 21%	4120
	11th to 20th	Day	5% 5% 2 8% 7% 7% 9% 7% 10% 13% 27%	4120
	21st to end	Day	5% 6% 3 9% 8% 9% 9% 7% 10% 14% 20%	4120
August	1st to 10th	Day	5% 3 2 5% 5% 6% 7% 6% 9% 13% 37%	3785
	11th to 20th	Day	6% 5% 2 6% 5% 6% 6% 6% 7% 9% 42%	3729
	21st to end	Day	6% 5% 3 8% 6% 7% 7% 6% 8% 11% 33%	4180
September	1st to 10th	Day	11% 8% 3 9% 7% 7% 6% 5% 7% 8% 31%	2199
	11th to 20th	Day	12% 7% 3 8% 7% 6% 4 4 6% 7% 36%	2090
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 5% 5% 6% 49%	2090
October	1st to 10th	Day	9% 5% 2 6% 4 4 4 3 5% 6% 51%	2090
	11th to 20th	Day	9% 3 1 3 3 3 4 2 5% 7% 59%	2090
	21st to end	Day	8% 4 2 6% 4 3 3 3 4 6% 57%	2114
November	1st to 10th	Day	8% 5% 2 5% 3 3 3 3 6% 6% 55%	1762
	11th to 20th	Day	10% 5% 2 5% 3 3 3 3 5% 7% 53%	1800
	21st to end	Day	12% 4 2 5% 4 4 4 4 5% 6% 49%	1746
December	1st to 10th	Day	13% 6% 2 6% 5% 4 4 3 5% 7% 47%	1710
	11th to 20th	Day	14% 8% 3 6% 5% 4 5% 3 5% 5% 42%	2153
	21st to end	Day	18% 9% 3 7% 4 3 3 3 3 5% 42%	3124
January	1st to 10th	Night	16% 6% 2 5% 4 4 4 4 5% 6% 45%	4101
	11th to 20th	Night	11% 7% 2 6% 4 4 3 3 5% 6% 48%	3800
	21st to end	Night	23% 9% 2 5% 3 3 3 3 4 5% 39%	4180
February	1st to 10th	Night	14% 7% 3 6% 4 3 3 3 5% 6% 44%	2280
	11th to 20th	Night	19% 7% 2 5% 3 3 3 3 5% 5% 46%	2218
	21st to end	Night	16% 9% 2 7% 5% 3 4 3 5% 5% 41%	1884
March	1st to 10th	Night	20% 13% 3 8% 4 3 4 3 4 5% 33%	3733
	11th to 20th	Night	9% 7% 2 6% 5% 4 5% 4 6% 8% 43%	3586
	21st to end	Night	13% 7% 3 6% 4 4 4 3 5% 7% 44%	3725
April	1st to 10th	Night	11% 8% 2 6% 5% 3 4 4 6% 7% 45%	1900
	11th to 20th	Night	12% 6% 2 6% 3 3 4 4 6% 8% 46%	1875
	21st to end	Night	5% 4 2 4 3 4 4 3 5% 7% 59%	1900
May	1st to 10th	Night	10% 7% 2 6% 3 4 5% 3 6% 8% 45%	3007
	11th to 20th	Night	12% 7% 2 7% 4 5% 4 4 5% 8% 43%	2812
	21st to end	Night	5% 4 1 5% 4 3 4 4 8% 12% 50%	3079
June	1st to 10th	Night	7% 5% 3 6% 5% 6% 5% 6% 8% 12% 37%	1710
	11th to 20th	Night	4 4 1 4 5% 5% 6% 6% 10% 12% 43%	1710
	21st to end	Night	5% 4 2 5% 6% 5% 6% 6% 9% 13% 40%	1710
July	1st to 10th	Night	5% 5% 2 6% 6% 7% 8% 6% 11% 17% 28%	2840
	11th to 20th	Night	3 4 1 4 4 5% 6% 5% 9% 14% 45%	2840
	21st to end	Night	3 3 2 6% 7% 7% 7% 8% 11% 16% 31%	3427
August	1st to 10th	Night	4 4 1 5% 5% 6% 6% 5% 9% 13% 43%	3144
	11th to 20th	Night	3 3 2 5% 4 5% 5% 5% 8% 12% 48%	3100
	21st to end	Night	5% 5% 2 8% 6% 6% 8% 6% 9% 11% 35%	3476
September	1st to 10th	Night	9% 6% 2 7% 5% 5% 6% 6% 8% 11% 35%	1962
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 5% 7% 8% 41%	2090
	21st to end	Night	8% 5% 1 6% 4 4 4 4 5% 8% 52%	2090
October	1st to 10th	Night	7% 4 2 5% 3 3 3 5% 7% 9% 52%	2090
	11th to 20th	Night	6% 5% 2 3 3 2 3 2 5% 6% 63%	2090
	21st to end	Night	9% 5% 2 5% 3 3 3 3 4 5% 57%	2477
November	1st to 10th	Night	7% 5% 2 5% 3 3 3 3 5% 7% 57%	2536
	11th to 20th	Night	11% 5% 2 5% 4 4 3 2 5% 6% 54%	2600
	21st to end	Night	11% 6% 2 5% 4 3 4 3 5% 7% 50%	2529
December	1st to 10th	Night	13% 6% 2 6% 4 4 3 4 5% 7% 46%	2470
	11th to 20th	Night	15% 7% 2 5% 4 3 4 3 4 6% 45%	3042
	21st to end	Night	17% 10% 3 6% 4 3 3 3 5% 5% 41%	4532

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	39% 2 5% 17% 24% 13%	2841
	11th to 20th	Day	30% 3 7% 18% 29% 13%	3160
	21st to end	Day	48% 2 4 14% 20% 12%	3476
February	1st to 10th	Day	44% 3 6% 16% 20% 10%	1900
	11th to 20th	Day	40% 4 5% 17% 22% 12%	1858
	21st to end	Day	43% 5% 7% 18% 16% 11%	1570
March	1st to 10th	Day	49% 3 7% 20% 14% 7%	3120
	11th to 20th	Day	39% 3 11% 20% 17% 9%	3374
	21st to end	Day	39% 3 12% 18% 18% 10%	3932
April	1st to 10th	Day	37% 4 10% 17% 20% 12%	2280
	11th to 20th	Day	38% 4 8% 19% 21% 10%	2254
	21st to end	Day	28% 4 10% 24% 25% 10%	2280
May	1st to 10th	Day	32% 4 13% 27% 19% 6%	3918
	11th to 20th	Day	41% 5% 12% 22% 17% 3	4085
	21st to end	Day	32% 4 15% 30% 18% 2	4489
June	1st to 10th	Day	47% 7% 15% 21% 8% 1	2470
	11th to 20th	Day	36% 8% 19% 24% 11% 2	2470
	21st to end	Day	42% 11% 19% 17% 9% 2	2470
July	1st to 10th	Day	45% 14% 29% 10% 2	4055
	11th to 20th	Day	41% 14% 31% 10% 2	4051
	21st to end	Day	48% 15% 21% 13% 3	3988
August	1st to 10th	Day	32% 10% 20% 23% 12% 2	3773
	11th to 20th	Day	34% 9% 19% 21% 17% 1	3765
	21st to end	Day	39% 13% 22% 16% 9% 1	4179
September	1st to 10th	Day	47% 9% 16% 13% 10% 5%	2199
	11th to 20th	Day	48% 6% 12% 15% 13% 6%	2090
	21st to end	Day	34% 6% 10% 20% 21% 10%	2090
October	1st to 10th	Day	35% 3 6% 12% 16% 28%	3480
	11th to 20th	Day	17% 3 4 19% 22% 35%	3458
	21st to end	Day	20% 2 4 13% 39% 22%	3467
November	1st to 10th	Day	29% 4 9% 19% 23% 16%	1762
	11th to 20th	Day	31% 3 7% 17% 28% 15%	1800
	21st to end	Day	35% 4 6% 19% 22% 14%	1746
December	1st to 10th	Day	38% 3 11% 18% 20% 10%	1710
	11th to 20th	Day	45% 2 5% 17% 20% 11%	2150
	21st to end	Day	46% 2 4 19% 22% 7%	3124
January	1st to 10th	Night	41% 3 5% 10% 25% 15%	4101
	11th to 20th	Night	37% 2 5% 15% 29% 12%	3800
	21st to end	Night	49% 2 4 14% 23% 8%	4180
February	1st to 10th	Night	41% 2 6% 18% 21% 11%	2280
	11th to 20th	Night	42% 3 6% 13% 21% 15%	2219
	21st to end	Night	45% 4 7% 15% 17% 13%	1884
March	1st to 10th	Night	55% 2 8% 15% 13% 7%	3733
	11th to 20th	Night	38% 3 11% 17% 21% 10%	3586
	21st to end	Night	41% 3 9% 19% 17% 10%	3725
April	1st to 10th	Night	39% 4 10% 14% 19% 13%	1900
	11th to 20th	Night	37% 4 8% 20% 21% 10%	1875
	21st to end	Night	26% 3 10% 28% 25% 9%	1900
May	1st to 10th	Night	37% 3 18% 20% 17% 5%	3037
	11th to 20th	Night	40% 4 13% 23% 17% 3	2813
	21st to end	Night	25% 5% 18% 32% 17% 3	3087
June	1st to 10th	Night	36% 9% 19% 24% 10% 2	1710
	11th to 20th	Night	27% 11% 23% 24% 12% 3	1710
	21st to end	Night	32% 11% 27% 19% 10% 2	1710
July	1st to 10th	Night	37% 16% 32% 12% 3	2795
	11th to 20th	Night	24% 15% 47% 12% 3	2786
	21st to end	Night	35% 22% 27% 13% 2	3318
August	1st to 10th	Night	28% 10% 26% 23% 12% 1	3132
	11th to 20th	Night	25% 9% 28% 23% 14%	3130
	21st to end	Night	37% 12% 22% 18% 9% 2	3476
September	1st to 10th	Night	38% 9% 23% 15% 11% 4	1962
	11th to 20th	Night	37% 9% 16% 18% 15% 5%	2090
	21st to end	Night	31% 7% 13% 20% 21% 9%	2090
October	1st to 10th	Night	36% 4 8% 12% 19% 22%	3480
	11th to 20th	Night	14% 2 5% 18% 29% 32%	3461
	21st to end	Night	21% 2 4 13% 42% 18%	4074
November	1st to 10th	Night	27% 4 8% 19% 25% 17%	2536
	11th to 20th	Night	32% 3 5% 17% 28% 15%	2600
	21st to end	Night	34% 3 8% 18% 22% 14%	2529
December	1st to 10th	Night	38% 4 9% 19% 22% 8%	2470
	11th to 20th	Night	40% 3 7% 13% 24% 12%	3044
	21st to end	Night	47% 3 5% 19% 22% 5%	4532

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	19% 19% 39% 16% 6% 1	270
	11th to 20th	Day	13% 20% 36% 21% 9% 1	270
	21st to end	Day	20% 25% 40% 10% 4	297
February	1st to 10th	Day	20% 26% 33% 16% 5% 1	270
	11th to 20th	Day	23% 21% 34% 19% 2	270
	21st to end	Day	13% 26% 44% 14% 4	225
March	1st to 10th	Day	15% 22% 41% 17% 4	270
	11th to 20th	Day	17% 18% 33% 22% 9% 2	393
	21st to end	Day	16% 16% 35% 22% 10% 2	506
April	1st to 10th	Day	17% 17% 30% 24% 10% 2	460
	11th to 20th	Day	15% 15% 29% 26% 13% 2	452
	21st to end	Day	10% 11% 27% 30% 18% 4	460
May	1st to 10th	Day	9% 9% 24% 29% 20% 8%	463
	11th to 20th	Day	9% 6% 21% 28% 22% 15%	487
	21st to end	Day	9% 3 17% 31% 22% 19%	529
June	1st to 10th	Day	12% 3 13% 29% 24% 19%	490
	11th to 20th	Day	8% 4 10% 26% 27% 24%	490
	21st to end	Day	8% 2 11% 23% 28% 28%	490
July	1st to 10th	Day	7% 2 6% 19% 30% 37%	485
	11th to 20th	Day	5% 1 4 17% 31% 42%	484
	21st to end	Day	6% 1 7% 18% 37% 31%	532
August	1st to 10th	Day	7% 6% 19% 31% 37%	486
	11th to 20th	Day	9% 1 5% 20% 32% 33%	479
	21st to end	Day	11% 3 7% 25% 31% 23%	539
September	1st to 10th	Day	13% 3 8% 22% 30% 23%	490
	11th to 20th	Day	16% 3 9% 29% 30% 12%	490
	21st to end	Day	10% 2 11% 31% 32% 14%	490
October	1st to 10th	Day	10% 4 24% 33% 23% 5%	490
	11th to 20th	Day	8% 4 21% 34% 25% 8%	490
	21st to end	Day	10% 9% 23% 33% 21% 4	449
November	1st to 10th	Day	16% 6% 25% 36% 14% 3	300
	11th to 20th	Day	13% 13% 34% 28% 10% 1	300
	21st to end	Day	13% 12% 36% 25% 12% 2	282
December	1st to 10th	Day	17% 16% 34% 21% 10% 2	270
	11th to 20th	Day	22% 15% 38% 20% 4 1	270
	21st to end	Day	27% 16% 27% 22% 7% 1	297
January	1st to 10th	Night	19% 11% 34% 29% 7% 1	760
	11th to 20th	Night	15% 12% 29% 33% 10%	760
	21st to end	Night	22% 12% 33% 27% 5%	836
February	1st to 10th	Night	17% 11% 32% 33% 6% 1	760
	11th to 20th	Night	20% 10% 36% 25% 9%	743
	21st to end	Night	19% 13% 36% 29% 4	628
March	1st to 10th	Night	15% 12% 32% 33% 8%	760
	11th to 20th	Night	13% 10% 34% 30% 11% 1	760
	21st to end	Night	13% 10% 32% 31% 13% 1	782
April	1st to 10th	Night	15% 11% 23% 38% 13% 1	570
	11th to 20th	Night	13% 7% 26% 35% 18% 1	563
	21st to end	Night	7% 6% 22% 41% 23% 1	570
May	1st to 10th	Night	11% 5% 18% 40% 22% 4	570
	11th to 20th	Night	8% 3 15% 36% 32% 6%	561
	21st to end	Night	7% 2 11% 32% 42% 7%	617
June	1st to 10th	Night	9% 2 8% 30% 42% 9%	570
	11th to 20th	Night	4 3 7% 29% 45% 13%	570
	21st to end	Night	5% 2 6% 22% 49% 16%	570
July	1st to 10th	Night	5% 1 3 21% 47% 23%	555
	11th to 20th	Night	6% 1 3 14% 47% 29%	552
	21st to end	Night	3 1 2 19% 53% 22%	624
August	1st to 10th	Night	4 1 3 14% 50% 28%	567
	11th to 20th	Night	5% 1 2 15% 51% 26%	564
	21st to end	Night	8% 3 7% 20% 44% 17%	627
September	1st to 10th	Night	12% 2 5% 24% 41% 17%	632
	11th to 20th	Night	13% 2 10% 29% 38% 7%	760
	21st to end	Night	10% 2 11% 30% 38% 8%	760
October	1st to 10th	Night	9% 2 23% 37% 27% 3	760
	11th to 20th	Night	9% 3 21% 35% 28% 4	760
	21st to end	Night	12% 5% 22% 38% 23% 1	836
November	1st to 10th	Night	10% 6% 24% 38% 20% 2	780
	11th to 20th	Night	12% 8% 28% 36% 15% 1	800
	21st to end	Night	13% 6% 31% 35% 14% 1	779
December	1st to 10th	Night	17% 7% 29% 30% 16% 1	760
	11th to 20th	Night	17% 9% 29% 32% 13% 1	760
	21st to end	Night	23% 9% 28% 31% 9% 1	836

Page generated at 2024-11-22 08:02:30. Version ac07

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