Anola
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Anola 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	12% 9% 3 9% 6% 5% 5% 4 6% 7% 34%	101870
	Night	10% 10% 4 9% 6% 6% 5% 4 6% 7% 33%	97241
Transparency	Day	49% 4 15% 24% 7%	101612
	Night	51% 4 14% 23% 8% 1	97147
Seeing	Day	14% 9% 30% 29% 14% 4	16248
	Night	15% 7% 30% 34% 13% 1	26147

By Month

Percentage Cloud Cover NW (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	6% 17% 5% 14% 9% 7% 7% 5% 5% 5% 19%	2219
	11th to 20th	Day	5% 9% 6% 19% 12% 12% 9% 6% 7% 5% 10%	2199
	21st to end	Day	7% 20% 7% 17% 8% 6% 6% 4 5% 4 14%	2739
February	1st to 10th	Day	8% 12% 6% 12% 8% 7% 8% 5% 8% 6% 20%	1653
	11th to 20th	Day	8% 10% 4 9% 7% 10% 7% 6% 8% 7% 24%	1664
	21st to end	Day	5% 12% 4 13% 8% 9% 8% 4 6% 6% 25%	1464
March	1st to 10th	Day	10% 13% 4 11% 10% 6% 6% 5% 5% 8% 24%	3240
	11th to 20th	Day	6% 10% 5% 15% 12% 8% 6% 4 5% 6% 22%	3478
	21st to end	Day	8% 15% 6% 13% 7% 4 4 3 5% 6% 30%	3814
April	1st to 10th	Day	9% 11% 4 9% 5% 4 4 4 5% 7% 35%	2310
	11th to 20th	Day	13% 10% 3 9% 6% 4 4 3 6% 6% 35%	2442
	21st to end	Day	15% 9% 3 7% 5% 4 5% 5% 6% 6% 35%	2470
May	1st to 10th	Day	16% 10% 3 6% 4 4 4 4 5% 7% 37%	4301
	11th to 20th	Day	20% 9% 3 7% 5% 4 4 4 5% 7% 32%	4571
	21st to end	Day	20% 9% 3 7% 5% 4 4 3 5% 6% 33%	5173
June	1st to 10th	Day	14% 8% 3 7% 5% 6% 5% 4 6% 7% 35%	2850
	11th to 20th	Day	16% 7% 3 7% 5% 5% 4 5% 6% 8% 35%	2850
	21st to end	Day	12% 6% 3 7% 6% 6% 5% 5% 8% 9% 35%	2850
July	1st to 10th	Day	9% 4 2 5% 5% 5% 6% 5% 7% 10% 41%	4750
	11th to 20th	Day	9% 4 2 5% 4 3 4 4 7% 9% 51%	4750
	21st to end	Day	7% 4 2 5% 5% 4 5% 4 6% 9% 51%	5150
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	4229
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 5% 8% 46%	4041
	21st to end	Day	14% 5% 2 5% 4 4 5% 4 5% 9% 44%	4532
September	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 6% 8% 48%	2365
	11th to 20th	Day	14% 7% 3 6% 4 4 4 4 6% 8% 38%	2095
	21st to end	Day	16% 7% 3 6% 4 4 4 3 5% 7% 41%	2090
October	1st to 10th	Day	16% 11% 3 8% 5% 4 5% 3 4 6% 34%	1918
	11th to 20th	Day	14% 13% 4 9% 5% 5% 4 3 5% 6% 32%	1886
	21st to end	Day	16% 15% 4 11% 5% 5% 5% 4 6% 7% 24%	1881
November	1st to 10th	Day	16% 15% 4 9% 5% 3 6% 3 5% 7% 27%	1497
	11th to 20th	Day	9% 17% 6% 14% 9% 4 4 4 4 6% 24%	1520
	21st to end	Day	12% 14% 5% 13% 11% 6% 5% 3 4 6% 22%	1428
December	1st to 10th	Day	8% 14% 7% 17% 8% 8% 6% 5% 5% 5% 16%	1330
	11th to 20th	Day	10% 16% 6% 14% 7% 4 6% 4 5% 7% 20%	1679
	21st to end	Day	10% 13% 5% 12% 6% 7% 6% 7% 9% 7% 17%	2442
January	1st to 10th	Night	5% 14% 6% 14% 8% 10% 8% 5% 6% 6% 18%	4737
	11th to 20th	Night	5% 14% 6% 15% 12% 12% 8% 6% 6% 5% 12%	4709
	21st to end	Night	9% 19% 8% 13% 7% 6% 5% 4 5% 5% 18%	4923
February	1st to 10th	Night	7% 13% 5% 11% 7% 6% 8% 5% 6% 6% 25%	2527
	11th to 20th	Night	6% 11% 3 9% 7% 7% 7% 5% 5% 6% 33%	2403
	21st to end	Night	6% 11% 5% 13% 7% 7% 5% 4 5% 7% 29%	2008
March	1st to 10th	Night	11% 11% 4 11% 8% 6% 6% 4 5% 6% 29%	3620
	11th to 20th	Night	5% 9% 4 9% 6% 5% 5% 4 5% 8% 41%	3480
	21st to end	Night	11% 14% 4 9% 6% 4 4 3 6% 6% 33%	3817
April	1st to 10th	Night	12% 9% 3 6% 4 5% 5% 4 7% 7% 40%	1868
	11th to 20th	Night	13% 12% 4 8% 4 4 4 4 6% 5% 37%	1689
	21st to end	Night	12% 9% 3 8% 5% 6% 5% 4 5% 6% 37%	1710
May	1st to 10th	Night	18% 10% 3 7% 4 4 4 3 6% 6% 35%	2668
	11th to 20th	Night	16% 7% 2 5% 4 4 4 3 6% 7% 40%	2331
	21st to end	Night	18% 9% 3 6% 3 3 3 3 5% 6% 41%	2414
June	1st to 10th	Night	13% 6% 2 6% 5% 4 5% 4 6% 8% 41%	1330
	11th to 20th	Night	13% 7% 2 6% 5% 3 5% 3 7% 7% 42%	1330
	21st to end	Night	10% 7% 1 6% 4 4 5% 4 6% 8% 44%	1330
July	1st to 10th	Night	8% 3 1 4 3 4 4 5% 7% 9% 51%	2220
	11th to 20th	Night	6% 3 1 3 3 3 4 4 7% 10% 56%	2220
	21st to end	Night	5% 3 1 4 4 4 5% 4 8% 10% 51%	2414
August	1st to 10th	Night	7% 5% 1 6% 4 4 5% 5% 6% 8% 49%	2707
	11th to 20th	Night	9% 4 2 5% 4 4 4 4 6% 8% 51%	2798
	21st to end	Night	10% 4 2 6% 4 4 5% 4 6% 7% 47%	3135
September	1st to 10th	Night	10% 4 1 5% 4 4 4 3 5% 7% 53%	1814
	11th to 20th	Night	14% 6% 2 6% 4 4 5% 4 5% 7% 43%	2083
	21st to end	Night	16% 6% 2 6% 5% 5% 4 4 5% 7% 41%	2090
October	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 3 5% 8% 37%	2242
	11th to 20th	Night	14% 12% 4 8% 5% 5% 4 4 5% 6% 33%	2289
	21st to end	Night	15% 12% 3 9% 5% 5% 5% 3 6% 6% 30%	2717
November	1st to 10th	Night	13% 14% 5% 11% 6% 5% 5% 4 5% 5% 28%	2615
	11th to 20th	Night	10% 17% 6% 12% 7% 5% 4 4 5% 5% 25%	2660
	21st to end	Night	12% 14% 5% 13% 8% 6% 6% 3 4 5% 23%	2750
December	1st to 10th	Night	7% 13% 5% 15% 11% 7% 6% 4 5% 7% 20%	2850
	11th to 20th	Night	9% 16% 6% 14% 7% 5% 6% 4 6% 6% 21%	3518
	21st to end	Night	8% 11% 4 13% 9% 8% 6% 5% 7% 7% 22%	5225

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	68% 3 12% 15% 3	2219
	11th to 20th	Day	73% 4 10% 11% 2	2220
	21st to end	Day	73% 3 8% 12% 4	2739
February	1st to 10th	Day	60% 5% 12% 14% 8% 1	1653
	11th to 20th	Day	55% 5% 13% 20% 7%	1673
	21st to end	Day	58% 5% 11% 17% 9%	1464
March	1st to 10th	Day	59% 4 13% 19% 5%	3240
	11th to 20th	Day	61% 5% 12% 16% 5%	3480
	21st to end	Day	55% 5% 12% 22% 7%	3814
April	1st to 10th	Day	48% 4 11% 25% 12%	2310
	11th to 20th	Day	48% 4 12% 23% 12% 1	2442
	21st to end	Day	48% 4 14% 24% 8% 1	2470
May	1st to 10th	Day	47% 4 10% 28% 11% 1	4301
	11th to 20th	Day	52% 3 10% 23% 11% 1	4575
	21st to end	Day	52% 4 11% 24% 10% 1	5173
June	1st to 10th	Day	48% 5% 13% 23% 11% 1	2850
	11th to 20th	Day	47% 5% 15% 23% 10% 1	2850
	21st to end	Day	44% 5% 19% 23% 8%	2850
July	1st to 10th	Day	37% 5% 23% 28% 7%	4676
	11th to 20th	Day	30% 3 21% 38% 7%	4669
	21st to end	Day	32% 3 20% 37% 8%	4988
August	1st to 10th	Day	35% 3 19% 34% 9%	4213
	11th to 20th	Day	38% 3 22% 32% 5%	4080
	21st to end	Day	40% 3 22% 30% 6%	4531
September	1st to 10th	Day	34% 5% 18% 32% 9% 1	2365
	11th to 20th	Day	44% 5% 20% 26% 4	2095
	21st to end	Day	44% 4 15% 31% 7%	2090
October	1st to 10th	Day	52% 4 16% 21% 6%	1918
	11th to 20th	Day	54% 4 13% 23% 6% 1	1886
	21st to end	Day	59% 5% 17% 16% 3	1881
November	1st to 10th	Day	58% 4 16% 17% 4 1	1497
	11th to 20th	Day	61% 6% 14% 13% 4	1520
	21st to end	Day	67% 4 14% 13% 2	1428
December	1st to 10th	Day	68% 5% 13% 11% 3	1330
	11th to 20th	Day	62% 3 16% 14% 4	1680
	21st to end	Day	61% 4 11% 19% 5%	2442
January	1st to 10th	Night	66% 3 14% 14% 4	4737
	11th to 20th	Night	73% 3 8% 13% 2	4750
	21st to end	Night	68% 3 11% 14% 3	4923
February	1st to 10th	Night	56% 6% 12% 17% 9%	2527
	11th to 20th	Night	49% 4 15% 23% 9%	2404
	21st to end	Night	55% 4 11% 19% 11%	2008
March	1st to 10th	Night	56% 4 11% 20% 9%	3620
	11th to 20th	Night	41% 3 17% 27% 11% 1	3480
	21st to end	Night	52% 3 10% 25% 10% 1	3817
April	1st to 10th	Night	42% 4 11% 25% 16% 2	1868
	11th to 20th	Night	48% 3 9% 21% 16% 3	1689
	21st to end	Night	47% 4 9% 26% 12% 1	1710
May	1st to 10th	Night	49% 4 9% 25% 13%	2668
	11th to 20th	Night	43% 3 12% 29% 9% 3	2331
	21st to end	Night	45% 3 11% 27% 14% 1	2414
June	1st to 10th	Night	39% 8% 17% 24% 13% 1	1330
	11th to 20th	Night	40% 5% 15% 23% 14% 2	1330
	21st to end	Night	37% 6% 20% 27% 8% 1	1330
July	1st to 10th	Night	29% 6% 23% 34% 8% 1	2185
	11th to 20th	Night	24% 4 23% 40% 9% 1	2178
	21st to end	Night	28% 2 23% 37% 8% 1	2337
August	1st to 10th	Night	32% 3 16% 36% 12% 1	2700
	11th to 20th	Night	32% 3 26% 31% 8%	2825
	21st to end	Night	37% 2 20% 32% 9%	3135
September	1st to 10th	Night	33% 3 18% 32% 13%	1814
	11th to 20th	Night	41% 4 18% 26% 10% 1	2083
	21st to end	Night	44% 4 13% 29% 9% 1	2090
October	1st to 10th	Night	46% 4 15% 25% 9%	2242
	11th to 20th	Night	52% 4 14% 24% 6%	2289
	21st to end	Night	54% 4 16% 21% 4	2717
November	1st to 10th	Night	58% 4 16% 15% 6% 1	2615
	11th to 20th	Night	61% 5% 14% 14% 5%	2660
	21st to end	Night	65% 5% 15% 12% 4	2750
December	1st to 10th	Night	64% 4 16% 12% 3	2850
	11th to 20th	Night	62% 4 14% 15% 4	3516
	21st to end	Night	60% 4 11% 19% 6%	5225

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	12% 4 36% 31% 14% 3	270
	11th to 20th	Day	10% 7% 30% 39% 13% 1	270
	21st to end	Day	15% 7% 28% 32% 12% 5%	297
February	1st to 10th	Day	14% 9% 32% 35% 8% 2	270
	11th to 20th	Day	12% 9% 36% 27% 11% 5%	270
	21st to end	Day	9% 4 44% 30% 11% 1	225
March	1st to 10th	Day	10% 10% 35% 31% 13% 1	270
	11th to 20th	Day	11% 11% 34% 26% 15% 3	270
	21st to end	Day	13% 8% 33% 30% 14% 2	297
April	1st to 10th	Day	14% 7% 31% 33% 11% 4	490
	11th to 20th	Day	18% 12% 31% 25% 13% 1	640
	21st to end	Day	16% 9% 34% 27% 12% 2	650
May	1st to 10th	Day	16% 14% 30% 26% 12% 2	653
	11th to 20th	Day	20% 12% 25% 27% 14% 3	675
	21st to end	Day	20% 10% 23% 30% 14% 3	734
June	1st to 10th	Day	17% 12% 27% 25% 12% 7%	680
	11th to 20th	Day	18% 10% 33% 28% 9% 3	680
	21st to end	Day	12% 8% 28% 30% 18% 5%	680
July	1st to 10th	Day	8% 6% 31% 27% 20% 9%	671
	11th to 20th	Day	11% 7% 31% 28% 18% 5%	668
	21st to end	Day	7% 5% 31% 30% 19% 8%	739
August	1st to 10th	Day	8% 7% 26% 32% 21% 6%	676
	11th to 20th	Day	10% 6% 23% 34% 18% 9%	665
	21st to end	Day	14% 7% 30% 28% 17% 4	748
September	1st to 10th	Day	10% 6% 31% 34% 16% 2	575
	11th to 20th	Day	15% 10% 37% 26% 8% 3	305
	21st to end	Day	21% 9% 30% 29% 10% 1	300
October	1st to 10th	Day	19% 13% 24% 32% 8% 4	300
	11th to 20th	Day	16% 9% 35% 32% 8% 1	300
	21st to end	Day	26% 9% 31% 22% 11% 1	330
November	1st to 10th	Day	23% 8% 28% 30% 10% 1	273
	11th to 20th	Day	16% 10% 40% 23% 9% 2	270
	21st to end	Day	17% 13% 37% 28% 5%	270
December	1st to 10th	Day	13% 6% 32% 32% 14% 3	270
	11th to 20th	Day	14% 7% 42% 26% 10% 1	270
	21st to end	Day	12% 7% 30% 32% 14% 4	297
January	1st to 10th	Night	13% 7% 32% 32% 14% 3	950
	11th to 20th	Night	16% 6% 31% 35% 11% 1	950
	21st to end	Night	15% 7% 31% 34% 12% 1	1045
February	1st to 10th	Night	14% 7% 26% 36% 15% 1	950
	11th to 20th	Night	12% 5% 30% 36% 15% 3	929
	21st to end	Night	10% 6% 35% 32% 15% 2	752
March	1st to 10th	Night	14% 7% 30% 32% 15% 2	698
	11th to 20th	Night	12% 7% 38% 30% 13% 1	570
	21st to end	Night	19% 7% 26% 30% 15% 3	627
April	1st to 10th	Night	15% 6% 29% 36% 12% 1	570
	11th to 20th	Night	18% 6% 30% 33% 13% 1	563
	21st to end	Night	16% 8% 31% 34% 11%	570
May	1st to 10th	Night	19% 6% 35% 30% 10% 1	570
	11th to 20th	Night	17% 8% 29% 31% 13% 1	561
	21st to end	Night	18% 7% 31% 32% 11%	617
June	1st to 10th	Night	14% 6% 29% 35% 16%	570
	11th to 20th	Night	15% 6% 32% 33% 14%	570
	21st to end	Night	13% 5% 21% 40% 20% 1	570
July	1st to 10th	Night	6% 4 25% 40% 23% 2	555
	11th to 20th	Night	9% 5% 25% 40% 20% 2	552
	21st to end	Night	8% 3 23% 42% 22% 3	624
August	1st to 10th	Night	8% 3 21% 45% 21% 1	567
	11th to 20th	Night	10% 4 21% 38% 23% 3	564
	21st to end	Night	12% 5% 24% 41% 18% 1	627
September	1st to 10th	Night	12% 4 29% 36% 17% 2	570
	11th to 20th	Night	16% 5% 27% 39% 13%	570
	21st to end	Night	18% 7% 32% 31% 12% 1	570
October	1st to 10th	Night	21% 7% 32% 31% 8%	722
	11th to 20th	Night	19% 8% 34% 29% 8% 1	769
	21st to end	Night	22% 8% 30% 30% 9% 1	1045
November	1st to 10th	Night	19% 9% 35% 27% 10%	935
	11th to 20th	Night	19% 8% 32% 30% 9% 2	950
	21st to end	Night	19% 8% 39% 26% 6% 1	950
December	1st to 10th	Night	12% 5% 31% 37% 12% 2	950
	11th to 20th	Night	16% 9% 34% 31% 10% 1	950
	21st to end	Night	18% 7% 30% 30% 13% 1	1045

Page generated at 2024-10-30 12:19:20. Version ac07

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