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 2024-03-18.

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% 4 8% 7% 4 5% 5% 6% 7% 33%	78097
	Night	10% 10% 5% 9% 7% 4 6% 5% 5% 7% 32%	81682
Transparency	Day	50% 5% 14% 23% 8% 1	77800
	Night	52% 4 14% 21% 8% 1	81561
Seeing	Day	14% 8% 31% 29% 14% 4	15248
	Night	15% 7% 30% 34% 13% 1	25415

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	7% 16% 6% 12% 10% 6% 7% 7% 5% 5% 19%	2219
	11th to 20th	Day	5% 8% 7% 17% 14% 9% 10% 8% 7% 5% 10%	2199
	21st to end	Day	8% 19% 8% 15% 10% 5% 6% 5% 5% 4 14%	2739
February	1st to 10th	Day	8% 12% 6% 11% 9% 5% 8% 7% 7% 7% 20%	1653
	11th to 20th	Day	8% 10% 4 8% 8% 6% 10% 7% 8% 7% 24%	1664
	21st to end	Day	6% 11% 5% 12% 8% 6% 9% 6% 6% 6% 25%	1464
March	1st to 10th	Day	11% 13% 6% 10% 8% 5% 7% 6% 5% 7% 23%	1962
	11th to 20th	Day	7% 11% 5% 10% 10% 6% 6% 6% 5% 7% 29%	2055
	21st to end	Day	11% 13% 4 8% 7% 3 5% 5% 6% 8% 30%	2178
April	1st to 10th	Day	10% 11% 4 8% 6% 3 4 5% 5% 7% 35%	2187
	11th to 20th	Day	13% 8% 4 8% 7% 3 5% 4 6% 7% 35%	2312
	21st to end	Day	15% 9% 4 6% 5% 3 5% 5% 5% 7% 35%	2340
May	1st to 10th	Day	16% 10% 4 5% 5% 3 4 4 5% 6% 39%	2437
	11th to 20th	Day	17% 8% 3 5% 5% 2 5% 4 6% 7% 36%	2573
	21st to end	Day	17% 8% 3 5% 5% 3 5% 4 5% 7% 37%	2918
June	1st to 10th	Day	14% 7% 3 6% 5% 5% 6% 5% 6% 7% 35%	2700
	11th to 20th	Day	16% 7% 3 6% 6% 4 5% 5% 6% 8% 35%	2700
	21st to end	Day	11% 6% 4 6% 6% 4 5% 6% 7% 9% 35%	2700
July	1st to 10th	Day	7% 3 2 4 4 4 6% 6% 7% 11% 46%	2700
	11th to 20th	Day	11% 4 3 5% 5% 3 4 6% 7% 9% 44%	2700
	21st to end	Day	8% 4 2 4 6% 3 5% 5% 6% 8% 50%	2939
August	1st to 10th	Day	7% 5% 2 5% 4 3 5% 5% 6% 10% 47%	2402
	11th to 20th	Day	11% 4 2 6% 5% 3 5% 6% 5% 8% 46%	2301
	21st to end	Day	13% 5% 3 4 4 3 5% 5% 6% 8% 45%	2574
September	1st to 10th	Day	11% 5% 2 5% 5% 3 4 5% 5% 8% 48%	2241
	11th to 20th	Day	14% 7% 3 6% 5% 3 4 6% 6% 8% 38%	1985
	21st to end	Day	17% 7% 3 5% 5% 3 4 4 5% 7% 40%	1980
October	1st to 10th	Day	17% 10% 3 7% 7% 3 5% 5% 4 6% 33%	1818
	11th to 20th	Day	14% 13% 4 8% 7% 4 5% 5% 4 6% 32%	1787
	21st to end	Day	16% 14% 4 10% 6% 3 6% 5% 6% 6% 23%	1782
November	1st to 10th	Day	17% 13% 5% 8% 6% 3 6% 4 5% 7% 27%	1489
	11th to 20th	Day	9% 15% 8% 13% 10% 4 4 4 5% 6% 24%	1520
	21st to end	Day	13% 13% 6% 11% 12% 5% 5% 4 4 6% 22%	1428
December	1st to 10th	Day	8% 13% 7% 15% 9% 6% 7% 7% 6% 5% 16%	1330
	11th to 20th	Day	10% 15% 7% 12% 9% 3 5% 6% 5% 7% 21%	1679
	21st to end	Day	10% 12% 6% 11% 8% 6% 7% 8% 9% 7% 17%	2442
January	1st to 10th	Night	5% 13% 7% 12% 10% 7% 8% 7% 6% 7% 18%	4737
	11th to 20th	Night	5% 13% 6% 12% 15% 9% 9% 8% 6% 5% 12%	4709
	21st to end	Night	9% 18% 9% 12% 9% 4 6% 6% 5% 5% 18%	4923
February	1st to 10th	Night	8% 12% 5% 10% 8% 4 8% 7% 6% 6% 25%	2527
	11th to 20th	Night	7% 10% 3 7% 8% 4 9% 6% 5% 6% 34%	2403
	21st to end	Night	7% 10% 5% 11% 8% 5% 6% 5% 5% 8% 29%	2008
March	1st to 10th	Night	11% 11% 5% 9% 8% 4 5% 5% 5% 6% 31%	2218
	11th to 20th	Night	7% 8% 4 8% 6% 3 4 4 5% 7% 43%	2068
	21st to end	Night	13% 11% 4 7% 6% 3 4 4 6% 8% 34%	2178
April	1st to 10th	Night	12% 8% 3 5% 5% 3 5% 5% 7% 7% 40%	1771
	11th to 20th	Night	12% 11% 5% 8% 5% 4 4 4 5% 6% 38%	1599
	21st to end	Night	12% 9% 3 6% 7% 5% 6% 5% 5% 7% 37%	1620
May	1st to 10th	Night	15% 9% 3 6% 5% 3 3 5% 6% 6% 39%	1522
	11th to 20th	Night	15% 7% 2 4 4 3 4 4 6% 8% 42%	1319
	21st to end	Night	17% 7% 3 5% 4 3 4 3 5% 8% 42%	1358
June	1st to 10th	Night	14% 5% 2 5% 6% 3 5% 5% 6% 8% 42%	1260
	11th to 20th	Night	12% 6% 3 6% 5% 3 4 4 7% 8% 42%	1260
	21st to end	Night	9% 6% 2 5% 5% 4 5% 5% 6% 8% 44%	1260
July	1st to 10th	Night	5% 3 1 4 4 3 3 6% 6% 8% 56%	1260
	11th to 20th	Night	7% 3 2 3 3 3 5% 6% 7% 10% 51%	1260
	21st to end	Night	7% 4 1 4 4 2 4 4 6% 9% 55%	1379
August	1st to 10th	Night	7% 4 1 4 4 3 5% 5% 5% 7% 55%	1533
	11th to 20th	Night	8% 4 2 5% 4 2 4 6% 6% 7% 52%	1600
	21st to end	Night	10% 5% 2 4 5% 2 5% 4 5% 7% 52%	1782
September	1st to 10th	Night	10% 4 1 4 5% 3 4 4 5% 7% 52%	1718
	11th to 20th	Night	14% 5% 2 5% 4 3 4 6% 5% 7% 44%	1973
	21st to end	Night	17% 6% 3 5% 6% 3 5% 5% 5% 7% 40%	1980
October	1st to 10th	Night	17% 8% 3 6% 6% 3 5% 4 5% 8% 36%	2124
	11th to 20th	Night	15% 12% 4 7% 6% 4 5% 5% 5% 6% 32%	2168
	21st to end	Night	15% 11% 4 8% 7% 3 5% 4 6% 7% 29%	2574
November	1st to 10th	Night	14% 13% 6% 9% 7% 4 5% 4 4 5% 28%	2588
	11th to 20th	Night	11% 15% 7% 10% 8% 4 5% 4 5% 5% 26%	2660
	21st to end	Night	12% 13% 6% 12% 9% 5% 6% 5% 4 6% 23%	2750
December	1st to 10th	Night	7% 11% 6% 13% 12% 7% 6% 6% 5% 7% 20%	2850
	11th to 20th	Night	9% 14% 7% 13% 8% 4 5% 6% 6% 6% 21%	3518
	21st to end	Night	9% 10% 5% 11% 10% 6% 7% 6% 6% 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	60% 6% 12% 16% 6%	1962
	11th to 20th	Day	55% 5% 13% 20% 7%	2057
	21st to end	Day	52% 5% 15% 20% 8% 1	2178
April	1st to 10th	Day	48% 4 11% 25% 11% 1	2187
	11th to 20th	Day	48% 4 12% 23% 12% 1	2312
	21st to end	Day	48% 4 15% 23% 8% 1	2340
May	1st to 10th	Day	46% 5% 10% 25% 14% 1	2437
	11th to 20th	Day	46% 4 10% 26% 13% 1	2577
	21st to end	Day	47% 5% 12% 22% 13% 1	2918
June	1st to 10th	Day	47% 5% 13% 24% 11% 1	2700
	11th to 20th	Day	47% 5% 15% 23% 10% 1	2700
	21st to end	Day	44% 6% 19% 23% 7%	2700
July	1st to 10th	Day	31% 6% 18% 33% 11% 1	2626
	11th to 20th	Day	34% 6% 17% 32% 10%	2619
	21st to end	Day	34% 5% 19% 31% 11%	2776
August	1st to 10th	Day	33% 5% 19% 34% 8% 1	2386
	11th to 20th	Day	37% 5% 20% 32% 6% 1	2301
	21st to end	Day	37% 5% 16% 34% 8%	2574
September	1st to 10th	Day	35% 6% 17% 32% 9% 1	2241
	11th to 20th	Day	44% 5% 19% 26% 5%	1985
	21st to end	Day	45% 4 14% 32% 5%	1980
October	1st to 10th	Day	53% 4 17% 19% 6%	1818
	11th to 20th	Day	55% 4 13% 23% 5% 1	1787
	21st to end	Day	60% 5% 16% 16% 3	1782
November	1st to 10th	Day	58% 4 16% 17% 4 1	1489
	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	54% 5% 12% 20% 10% 1	2218
	11th to 20th	Night	41% 4 15% 27% 11% 1	2068
	21st to end	Night	48% 4 13% 21% 12% 1	2178
April	1st to 10th	Night	42% 4 12% 24% 16% 2	1771
	11th to 20th	Night	48% 3 9% 21% 16% 3	1599
	21st to end	Night	48% 4 9% 26% 12% 1	1620
May	1st to 10th	Night	45% 5% 11% 25% 14%	1522
	11th to 20th	Night	40% 4 12% 27% 13% 3	1319
	21st to end	Night	41% 5% 12% 22% 17% 2	1358
June	1st to 10th	Night	39% 8% 17% 24% 12% 1	1260
	11th to 20th	Night	40% 5% 16% 23% 15% 2	1260
	21st to end	Night	36% 6% 21% 28% 8% 1	1260
July	1st to 10th	Night	23% 6% 17% 39% 13% 1	1225
	11th to 20th	Night	27% 7% 22% 30% 14% 1	1218
	21st to end	Night	27% 3 15% 41% 13% 1	1302
August	1st to 10th	Night	28% 5% 18% 37% 11% 1	1526
	11th to 20th	Night	30% 5% 22% 32% 11%	1600
	21st to end	Night	33% 4 15% 34% 13% 1	1782
September	1st to 10th	Night	34% 3 18% 31% 13%	1718
	11th to 20th	Night	41% 5% 17% 26% 10% 1	1973
	21st to end	Night	45% 4 13% 29% 8%	1980
October	1st to 10th	Night	47% 5% 16% 23% 9%	2124
	11th to 20th	Night	53% 4 14% 24% 5%	2168
	21st to end	Night	55% 4 16% 20% 4	2574
November	1st to 10th	Night	58% 4 16% 15% 6% 1	2588
	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% 10% 33% 27% 16% 3	261
	21st to end	Day	13% 7% 34% 29% 14% 3	264
April	1st to 10th	Day	15% 7% 32% 32% 11% 3	447
	11th to 20th	Day	17% 11% 31% 26% 14% 1	590
	21st to end	Day	16% 9% 34% 27% 12% 2	600
May	1st to 10th	Day	16% 14% 29% 27% 13% 1	603
	11th to 20th	Day	20% 12% 23% 28% 14% 3	625
	21st to end	Day	20% 9% 23% 30% 14% 3	679
June	1st to 10th	Day	17% 11% 27% 25% 12% 7%	630
	11th to 20th	Day	18% 10% 31% 28% 10% 3	630
	21st to end	Day	12% 7% 28% 30% 19% 5%	630
July	1st to 10th	Day	8% 6% 32% 28% 19% 7%	621
	11th to 20th	Day	11% 8% 31% 29% 17% 4	618
	21st to end	Day	8% 5% 30% 29% 19% 8%	684
August	1st to 10th	Day	7% 7% 27% 31% 21% 7%	626
	11th to 20th	Day	10% 6% 24% 34% 17% 8%	615
	21st to end	Day	14% 7% 29% 28% 17% 5%	693
September	1st to 10th	Day	11% 6% 33% 33% 15% 2	531
	11th to 20th	Day	14% 11% 37% 26% 9% 3	275
	21st to end	Day	22% 9% 30% 27% 10% 1	270
October	1st to 10th	Day	19% 13% 23% 32% 9% 5%	270
	11th to 20th	Day	16% 8% 33% 33% 9% 1	270
	21st to end	Day	27% 9% 32% 20% 10% 1	297
November	1st to 10th	Day	23% 8% 28% 30% 10% 1	270
	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% 37% 30% 13% 1	564
	21st to end	Night	19% 8% 25% 30% 16% 3	594
April	1st to 10th	Night	16% 6% 29% 36% 12% 1	540
	11th to 20th	Night	17% 6% 30% 33% 13% 1	533
	21st to end	Night	16% 8% 31% 34% 11%	540
May	1st to 10th	Night	19% 5% 34% 31% 10% 1	540
	11th to 20th	Night	17% 7% 29% 31% 14% 1	531
	21st to end	Night	19% 7% 31% 32% 11% 1	584
June	1st to 10th	Night	14% 6% 27% 35% 17%	540
	11th to 20th	Night	13% 6% 31% 34% 15%	540
	21st to end	Night	12% 6% 20% 40% 21% 1	540
July	1st to 10th	Night	6% 4 26% 41% 22% 1	525
	11th to 20th	Night	9% 5% 25% 40% 19% 2	522
	21st to end	Night	8% 3 23% 41% 22% 3	591
August	1st to 10th	Night	8% 3 22% 45% 21% 1	537
	11th to 20th	Night	10% 4 22% 39% 23% 3	534
	21st to end	Night	12% 5% 22% 41% 18% 1	594
September	1st to 10th	Night	12% 4 29% 36% 17% 2	540
	11th to 20th	Night	16% 5% 26% 40% 13%	540
	21st to end	Night	19% 7% 31% 31% 12% 1	540
October	1st to 10th	Night	20% 7% 31% 32% 9%	684
	11th to 20th	Night	20% 8% 33% 30% 9% 1	728
	21st to end	Night	23% 8% 29% 29% 9% 1	990
November	1st to 10th	Night	19% 9% 35% 27% 10%	925
	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 2024-03-15 13:01:40. Version ac07

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