Deerwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deerwood clear sky chart from 2005-11-06 to 2024-02-05.

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	11% 8% 4 7% 7% 4 5% 5% 6% 8% 35%	77742
	Night	9% 9% 4 8% 7% 4 5% 5% 6% 7% 36%	81109
Transparency	Day	45% 8% 16% 22% 8% 1	77452
	Night	46% 8% 15% 21% 9% 1	80980
Seeing	Day	13% 10% 32% 29% 13% 3	15094
	Night	13% 9% 34% 32% 11% 1	25215

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	5% 16% 6% 11% 7% 5% 8% 5% 5% 5% 26%	2219
	11th to 20th	Day	4 7% 5% 14% 12% 6% 11% 8% 8% 11% 15%	2330
	21st to end	Day	7% 10% 6% 12% 8% 4 8% 5% 6% 8% 26%	2794
February	1st to 10th	Day	8% 11% 5% 9% 9% 5% 6% 6% 7% 9% 25%	1533
	11th to 20th	Day	6% 8% 4 9% 10% 6% 7% 9% 9% 8% 24%	1574
	21st to end	Day	8% 9% 6% 10% 8% 5% 6% 8% 7% 7% 27%	1462
March	1st to 10th	Day	9% 12% 5% 12% 10% 5% 6% 5% 7% 8% 20%	1802
	11th to 20th	Day	7% 10% 4 7% 10% 5% 6% 6% 7% 7% 30%	1978
	21st to end	Day	11% 12% 6% 10% 8% 3 5% 4 6% 7% 29%	2178
April	1st to 10th	Day	9% 11% 6% 7% 6% 3 5% 5% 5% 7% 35%	2198
	11th to 20th	Day	14% 11% 4 8% 7% 4 6% 5% 5% 6% 30%	2312
	21st to end	Day	17% 10% 4 8% 6% 3 5% 5% 4 6% 33%	2340
May	1st to 10th	Day	14% 9% 3 6% 5% 3 4 4 5% 7% 39%	2340
	11th to 20th	Day	17% 9% 3 6% 4 2 4 4 5% 8% 38%	2640
	21st to end	Day	18% 8% 3 5% 5% 4 4 5% 5% 7% 37%	2918
June	1st to 10th	Day	12% 7% 2 6% 6% 4 5% 6% 7% 9% 37%	2700
	11th to 20th	Day	14% 5% 3 6% 6% 4 5% 6% 7% 9% 35%	2700
	21st to end	Day	12% 6% 3 5% 6% 3 6% 7% 7% 10% 37%	2700
July	1st to 10th	Day	8% 4 1 5% 5% 4 5% 5% 7% 9% 47%	2700
	11th to 20th	Day	9% 5% 2 5% 6% 3 6% 5% 6% 8% 45%	2700
	21st to end	Day	5% 3 1 4 4 3 5% 5% 5% 8% 54%	2821
August	1st to 10th	Day	8% 5% 2 5% 6% 4 5% 5% 7% 7% 46%	2464
	11th to 20th	Day	10% 5% 3 5% 4 3 4 5% 7% 9% 46%	2301
	21st to end	Day	11% 5% 2 5% 5% 3 4 5% 5% 7% 49%	2574
September	1st to 10th	Day	11% 6% 2 4 5% 3 4 4 5% 7% 50%	2207
	11th to 20th	Day	15% 6% 3 5% 5% 3 4 5% 4 7% 44%	1980
	21st to end	Day	15% 7% 2 4 5% 3 4 4 6% 9% 41%	1980
October	1st to 10th	Day	16% 9% 3 6% 5% 3 4 5% 6% 6% 36%	1879
	11th to 20th	Day	12% 11% 4 7% 6% 3 5% 4 5% 8% 36%	1719
	21st to end	Day	15% 12% 4 8% 5% 3 4 5% 6% 8% 29%	1782
November	1st to 10th	Day	15% 12% 5% 9% 6% 4 5% 4 5% 7% 28%	1582
	11th to 20th	Day	9% 12% 6% 13% 9% 4 5% 5% 5% 6% 27%	1520
	21st to end	Day	10% 12% 6% 10% 9% 5% 6% 4 6% 7% 26%	1364
December	1st to 10th	Day	8% 10% 6% 11% 10% 4 8% 6% 6% 7% 23%	1330
	11th to 20th	Day	9% 13% 5% 12% 10% 4 6% 6% 6% 6% 22%	1679
	21st to end	Day	8% 9% 5% 9% 6% 4 5% 6% 6% 7% 35%	2442
January	1st to 10th	Night	6% 12% 6% 12% 9% 4 6% 6% 5% 6% 27%	4737
	11th to 20th	Night	5% 10% 6% 13% 13% 6% 7% 7% 8% 7% 19%	4575
	21st to end	Night	8% 13% 7% 13% 8% 5% 5% 5% 6% 6% 26%	4873
February	1st to 10th	Night	7% 10% 5% 8% 8% 5% 8% 6% 7% 8% 29%	2521
	11th to 20th	Night	6% 8% 4 7% 7% 5% 7% 7% 7% 8% 33%	2273
	21st to end	Night	7% 9% 5% 8% 6% 5% 6% 5% 7% 8% 34%	1808
March	1st to 10th	Night	10% 10% 5% 10% 8% 4 6% 5% 6% 7% 29%	2157
	11th to 20th	Night	6% 9% 4 8% 7% 4 6% 5% 5% 7% 40%	1980
	21st to end	Night	11% 10% 4 9% 7% 4 5% 5% 5% 6% 34%	2178
April	1st to 10th	Night	7% 7% 4 6% 6% 4 5% 5% 7% 7% 42%	1760
	11th to 20th	Night	13% 10% 5% 7% 6% 3 6% 5% 6% 6% 33%	1599
	21st to end	Night	12% 10% 4 5% 6% 3 5% 5% 7% 8% 35%	1620
May	1st to 10th	Night	14% 7% 3 5% 5% 4 4 4 5% 6% 43%	1620
	11th to 20th	Night	13% 7% 3 5% 4 3 4 5% 5% 8% 43%	1251
	21st to end	Night	17% 9% 3 4 3 2 5% 4 4 7% 43%	1358
June	1st to 10th	Night	10% 6% 2 5% 6% 3 4 6% 6% 8% 44%	1260
	11th to 20th	Night	11% 5% 2 6% 4 3 4 6% 7% 8% 44%	1260
	21st to end	Night	9% 4 3 5% 4 3 5% 5% 7% 10% 46%	1260
July	1st to 10th	Night	7% 3 1 4 3 3 3 4 6% 8% 58%	1260
	11th to 20th	Night	5% 3 2 3 3 3 4 5% 6% 9% 57%	1260
	21st to end	Night	4 4 1 3 3 3 5% 3 7% 9% 58%	1495
August	1st to 10th	Night	6% 5% 2 4 4 3 3 4 7% 9% 54%	1475
	11th to 20th	Night	8% 2 2 5% 4 3 5% 4 5% 9% 53%	1600
	21st to end	Night	10% 3 2 4 4 2 4 4 5% 6% 55%	1782
September	1st to 10th	Night	9% 4 2 3 4 2 4 4 5% 8% 54%	1749
	11th to 20th	Night	12% 5% 2 4 3 3 4 4 5% 7% 50%	1980
	21st to end	Night	16% 6% 3 5% 5% 3 4 5% 5% 7% 43%	1980
October	1st to 10th	Night	14% 8% 4 6% 5% 3 3 5% 6% 8% 38%	2062
	11th to 20th	Night	14% 10% 3 6% 5% 3 3 5% 5% 7% 40%	2240
	21st to end	Night	11% 11% 4 9% 6% 3 5% 5% 5% 7% 34%	2574
November	1st to 10th	Night	12% 11% 4 8% 6% 4 5% 6% 6% 8% 31%	2495
	11th to 20th	Night	9% 13% 6% 10% 7% 4 6% 5% 5% 6% 29%	2660
	21st to end	Night	10% 12% 5% 9% 9% 5% 5% 4 5% 6% 30%	2814
December	1st to 10th	Night	7% 10% 6% 11% 9% 5% 6% 5% 5% 7% 28%	2850
	11th to 20th	Night	9% 13% 7% 13% 8% 5% 5% 5% 6% 7% 22%	3518
	21st to end	Night	9% 10% 4 9% 8% 5% 5% 4 5% 6% 34%	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	57% 8% 15% 16% 3	2219
	11th to 20th	Day	63% 8% 12% 12% 4	2352
	21st to end	Day	55% 7% 11% 21% 6%	2794
February	1st to 10th	Day	53% 7% 14% 18% 7% 1	1533
	11th to 20th	Day	52% 9% 13% 16% 10%	1583
	21st to end	Day	53% 9% 13% 17% 8%	1462
March	1st to 10th	Day	59% 9% 16% 11% 5%	1802
	11th to 20th	Day	49% 9% 15% 19% 8%	1980
	21st to end	Day	55% 7% 13% 18% 7%	2178
April	1st to 10th	Day	47% 7% 14% 22% 9% 1	2198
	11th to 20th	Day	52% 7% 12% 18% 10% 1	2312
	21st to end	Day	50% 7% 17% 16% 8% 1	2340
May	1st to 10th	Day	44% 7% 12% 25% 11% 1	2340
	11th to 20th	Day	43% 7% 14% 24% 10% 1	2644
	21st to end	Day	46% 7% 14% 22% 9% 1	2918
June	1st to 10th	Day	41% 9% 19% 22% 9%	2700
	11th to 20th	Day	42% 10% 17% 21% 9% 1	2700
	21st to end	Day	39% 11% 20% 24% 5% 1	2700
July	1st to 10th	Day	30% 10% 19% 31% 9% 1	2626
	11th to 20th	Day	33% 10% 19% 28% 11%	2619
	21st to end	Day	25% 9% 21% 33% 12% 1	2664
August	1st to 10th	Day	33% 10% 17% 28% 10% 1	2448
	11th to 20th	Day	32% 9% 21% 29% 9%	2301
	21st to end	Day	34% 7% 15% 31% 13%	2574
September	1st to 10th	Day	33% 6% 19% 29% 12% 1	2207
	11th to 20th	Day	40% 8% 18% 24% 9% 1	1980
	21st to end	Day	39% 8% 16% 30% 7%	1980
October	1st to 10th	Day	45% 8% 15% 23% 8%	1879
	11th to 20th	Day	47% 6% 16% 22% 9% 1	1719
	21st to end	Day	53% 8% 18% 15% 5%	1782
November	1st to 10th	Day	55% 9% 10% 18% 7% 1	1582
	11th to 20th	Day	57% 6% 16% 13% 6%	1520
	21st to end	Day	57% 8% 14% 16% 5%	1364
December	1st to 10th	Day	58% 9% 15% 14% 5%	1330
	11th to 20th	Day	59% 10% 12% 13% 6% 1	1680
	21st to end	Day	46% 8% 13% 21% 12%	2442
January	1st to 10th	Night	55% 9% 14% 16% 5%	4737
	11th to 20th	Night	62% 8% 11% 14% 4	4615
	21st to end	Night	57% 8% 10% 19% 5%	4873
February	1st to 10th	Night	50% 8% 14% 18% 10% 1	2521
	11th to 20th	Night	45% 9% 15% 19% 11% 1	2274
	21st to end	Night	46% 8% 13% 21% 11% 1	1808
March	1st to 10th	Night	52% 8% 15% 17% 8% 1	2157
	11th to 20th	Night	42% 7% 14% 25% 11% 1	1980
	21st to end	Night	49% 9% 14% 17% 10% 1	2178
April	1st to 10th	Night	38% 7% 14% 23% 15% 3	1760
	11th to 20th	Night	50% 7% 11% 18% 13% 2	1599
	21st to end	Night	45% 7% 15% 20% 11% 2	1620
May	1st to 10th	Night	41% 6% 13% 26% 13% 1	1620
	11th to 20th	Night	39% 7% 15% 23% 15% 2	1251
	21st to end	Night	41% 8% 12% 24% 15% 1	1358
June	1st to 10th	Night	35% 10% 20% 25% 8% 2	1260
	11th to 20th	Night	35% 8% 17% 25% 12% 2	1260
	21st to end	Night	31% 12% 22% 28% 7% 1	1260
July	1st to 10th	Night	23% 8% 17% 38% 13% 2	1225
	11th to 20th	Night	22% 10% 20% 31% 16% 1	1218
	21st to end	Night	21% 8% 17% 37% 15% 2	1412
August	1st to 10th	Night	25% 7% 19% 34% 12% 2	1467
	11th to 20th	Night	27% 8% 22% 30% 11% 1	1600
	21st to end	Night	28% 7% 16% 32% 16% 1	1782
September	1st to 10th	Night	28% 7% 15% 33% 15% 2	1749
	11th to 20th	Night	32% 7% 19% 28% 13% 1	1980
	21st to end	Night	40% 7% 13% 30% 10% 1	1980
October	1st to 10th	Night	43% 9% 15% 24% 8%	2062
	11th to 20th	Night	43% 7% 14% 26% 10%	2240
	21st to end	Night	47% 8% 16% 22% 6% 1	2574
November	1st to 10th	Night	48% 10% 14% 17% 8% 2	2495
	11th to 20th	Night	55% 9% 14% 14% 7% 1	2660
	21st to end	Night	55% 9% 15% 15% 6%	2814
December	1st to 10th	Night	54% 9% 16% 15% 6%	2850
	11th to 20th	Night	59% 10% 15% 11% 5% 1	3516
	21st to end	Night	50% 7% 12% 18% 11% 1	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	9% 12% 35% 32% 11% 1	270
	11th to 20th	Day	10% 10% 43% 27% 9% 1	270
	21st to end	Day	13% 11% 39% 26% 10% 2	297
February	1st to 10th	Day	11% 12% 44% 26% 5% 3	252
	11th to 20th	Day	9% 18% 32% 33% 8% 1	240
	21st to end	Day	6% 7% 45% 33% 8% 1	198
March	1st to 10th	Day	13% 12% 33% 32% 10% 1	240
	11th to 20th	Day	14% 9% 30% 34% 11% 3	240
	21st to end	Day	12% 13% 32% 31% 8% 4	264
April	1st to 10th	Day	14% 16% 35% 25% 8% 1	458
	11th to 20th	Day	18% 12% 32% 25% 12% 1	590
	21st to end	Day	17% 12% 34% 24% 10% 2	600
May	1st to 10th	Day	15% 11% 32% 29% 11% 2	603
	11th to 20th	Day	18% 11% 29% 26% 13% 3	625
	21st to end	Day	20% 10% 24% 30% 15% 3	679
June	1st to 10th	Day	12% 12% 31% 26% 15% 5%	630
	11th to 20th	Day	14% 12% 34% 25% 13% 3	630
	21st to end	Day	12% 8% 27% 34% 16% 4	630
July	1st to 10th	Day	7% 6% 29% 34% 18% 6%	621
	11th to 20th	Day	11% 8% 32% 28% 19% 3	618
	21st to end	Day	4 5% 28% 36% 19% 7%	684
August	1st to 10th	Day	7% 6% 28% 31% 21% 7%	626
	11th to 20th	Day	9% 6% 27% 32% 18% 9%	615
	21st to end	Day	11% 7% 28% 32% 19% 4	693
September	1st to 10th	Day	11% 10% 36% 29% 11% 3	497
	11th to 20th	Day	17% 11% 31% 26% 13% 1	270
	21st to end	Day	23% 11% 29% 27% 9% 1	270
October	1st to 10th	Day	20% 16% 25% 26% 13% 1	270
	11th to 20th	Day	14% 11% 40% 26% 6% 2	270
	21st to end	Day	21% 13% 37% 21% 7% 2	297
November	1st to 10th	Day	22% 12% 29% 27% 9%	270
	11th to 20th	Day	13% 17% 36% 27% 6%	270
	21st to end	Day	15% 18% 40% 23% 4	270
December	1st to 10th	Day	11% 11% 39% 26% 11% 2	270
	11th to 20th	Day	16% 15% 40% 24% 4 1	270
	21st to end	Day	13% 9% 38% 29% 7% 3	297
January	1st to 10th	Night	11% 13% 34% 30% 11% 1	950
	11th to 20th	Night	13% 12% 39% 31% 6%	950
	21st to end	Night	12% 12% 39% 29% 6% 1	1045
February	1st to 10th	Night	12% 11% 37% 31% 8% 1	923
	11th to 20th	Night	10% 10% 36% 33% 10% 2	879
	21st to end	Night	11% 9% 37% 32% 9% 2	624
March	1st to 10th	Night	14% 11% 33% 27% 12% 2	717
	11th to 20th	Night	9% 10% 40% 28% 12% 2	540
	21st to end	Night	16% 9% 28% 32% 11% 4	594
April	1st to 10th	Night	11% 9% 38% 32% 9% 1	540
	11th to 20th	Night	17% 7% 35% 30% 11%	533
	21st to end	Night	16% 7% 28% 37% 9% 1	540
May	1st to 10th	Night	17% 6% 33% 34% 9% 1	540
	11th to 20th	Night	17% 7% 28% 33% 14%	531
	21st to end	Night	19% 8% 31% 31% 11%	584
June	1st to 10th	Night	12% 7% 28% 39% 13% 1	540
	11th to 20th	Night	14% 5% 33% 32% 16% 1	540
	21st to end	Night	9% 7% 27% 39% 17% 1	540
July	1st to 10th	Night	6% 3 26% 42% 22% 1	525
	11th to 20th	Night	7% 5% 29% 41% 18% 1	522
	21st to end	Night	5% 3 26% 44% 20% 2	591
August	1st to 10th	Night	8% 4 25% 43% 20% 1	537
	11th to 20th	Night	9% 4 25% 39% 19% 3	534
	21st to end	Night	9% 6% 26% 40% 18% 1	594
September	1st to 10th	Night	11% 5% 31% 35% 16% 2	540
	11th to 20th	Night	13% 7% 29% 39% 12% 1	540
	21st to end	Night	18% 7% 33% 29% 13%	540
October	1st to 10th	Night	19% 10% 32% 30% 8%	622
	11th to 20th	Night	19% 10% 34% 28% 9%	800
	21st to end	Night	16% 12% 36% 27% 8% 1	990
November	1st to 10th	Night	16% 12% 37% 26% 7% 1	925
	11th to 20th	Night	14% 14% 38% 25% 7% 2	950
	21st to end	Night	15% 16% 39% 24% 5% 1	950
December	1st to 10th	Night	10% 12% 38% 30% 9% 1	950
	11th to 20th	Night	15% 13% 36% 28% 7% 1	950
	21st to end	Night	19% 7% 35% 29% 9% 1	1045

Page generated at 2024-02-02 04:20:28. Version ac07

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