Morden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morden clear sky chart from 2005-11-06 to 2024-01-14.

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% 6% 4 5% 5% 6% 7% 36%	74640
	Night	10% 9% 4 8% 7% 3 5% 5% 6% 7% 37%	75144
Transparency	Day	46% 8% 14% 23% 9% 1	74328
	Night	46% 7% 14% 22% 10% 1	74975
Seeing	Day	14% 9% 31% 29% 13% 4	15019
	Night	14% 8% 33% 32% 12% 1	25096

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% 12% 5% 11% 8% 5% 5% 7% 7% 7% 28%	1329
	11th to 20th	Day	7% 12% 6% 13% 9% 5% 7% 6% 8% 7% 20%	1353
	21st to end	Day	8% 14% 7% 10% 9% 5% 9% 6% 7% 7% 18%	1584
February	1st to 10th	Day	8% 11% 6% 8% 8% 5% 6% 6% 7% 7% 27%	1521
	11th to 20th	Day	7% 9% 4 10% 9% 6% 8% 8% 8% 7% 24%	1574
	21st to end	Day	7% 8% 5% 10% 10% 5% 6% 7% 6% 8% 29%	1455
March	1st to 10th	Day	10% 12% 6% 10% 11% 5% 6% 6% 5% 8% 22%	1813
	11th to 20th	Day	8% 9% 4 9% 9% 4 7% 5% 6% 7% 32%	1978
	21st to end	Day	13% 12% 5% 10% 7% 4 5% 4 6% 8% 27%	2178
April	1st to 10th	Day	10% 11% 6% 8% 5% 3 4 5% 5% 7% 34%	2190
	11th to 20th	Day	13% 11% 4 8% 6% 3 5% 5% 6% 6% 32%	2312
	21st to end	Day	18% 9% 4 8% 6% 3 4 4 5% 6% 33%	2340
May	1st to 10th	Day	15% 9% 3 6% 5% 3 4 5% 6% 6% 39%	2344
	11th to 20th	Day	17% 9% 3 5% 4 3 5% 5% 5% 7% 39%	2619
	21st to end	Day	18% 7% 3 5% 4 3 5% 4 5% 7% 38%	2918
June	1st to 10th	Day	13% 6% 3 5% 6% 3 5% 6% 7% 9% 37%	2700
	11th to 20th	Day	14% 6% 3 6% 5% 3 6% 6% 7% 8% 37%	2700
	21st to end	Day	11% 4 3 6% 6% 4 6% 7% 7% 9% 38%	2700
July	1st to 10th	Day	7% 3 2 4 5% 4 5% 6% 7% 9% 47%	2700
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 6% 6% 9% 45%	2700
	21st to end	Day	5% 3 1 4 4 2 5% 5% 7% 9% 55%	2826
August	1st to 10th	Day	7% 4 3 6% 5% 3 5% 6% 6% 9% 45%	2444
	11th to 20th	Day	10% 4 2 4 4 4 4 5% 6% 9% 48%	2301
	21st to end	Day	11% 4 2 5% 4 3 4 5% 5% 7% 50%	2574
September	1st to 10th	Day	11% 5% 2 4 4 2 4 4 5% 8% 51%	2206
	11th to 20th	Day	14% 6% 2 5% 5% 2 5% 5% 5% 7% 44%	1980
	21st to end	Day	16% 6% 2 5% 5% 3 4 4 5% 8% 43%	1980
October	1st to 10th	Day	17% 9% 3 5% 5% 3 4 4 6% 6% 37%	1871
	11th to 20th	Day	12% 11% 4 7% 5% 3 6% 5% 5% 7% 36%	1735
	21st to end	Day	15% 11% 4 8% 7% 3 5% 5% 6% 7% 30%	1782
November	1st to 10th	Day	14% 12% 5% 9% 6% 4 4 5% 5% 6% 30%	1575
	11th to 20th	Day	8% 12% 7% 11% 10% 4 5% 5% 4 6% 27%	1520
	21st to end	Day	11% 14% 5% 10% 8% 4 4 5% 5% 6% 28%	1387
December	1st to 10th	Day	8% 10% 7% 12% 9% 4 6% 6% 7% 6% 24%	1330
	11th to 20th	Day	9% 13% 6% 13% 10% 4 6% 6% 5% 6% 23%	1679
	21st to end	Day	9% 10% 5% 9% 8% 4 5% 5% 6% 6% 34%	2442
January	1st to 10th	Night	6% 12% 6% 9% 8% 4 6% 6% 6% 7% 30%	2837
	11th to 20th	Night	8% 13% 7% 11% 9% 4 6% 6% 6% 6% 23%	2682
	21st to end	Night	8% 11% 6% 13% 9% 5% 6% 6% 7% 6% 23%	2772
February	1st to 10th	Night	7% 10% 5% 8% 9% 4 8% 7% 6% 6% 30%	2439
	11th to 20th	Night	6% 9% 4 8% 5% 5% 7% 7% 7% 9% 33%	2273
	21st to end	Night	7% 10% 5% 8% 6% 4 6% 4 7% 7% 35%	1816
March	1st to 10th	Night	10% 12% 5% 10% 7% 4 6% 5% 5% 7% 30%	2147
	11th to 20th	Night	7% 7% 4 8% 6% 4 6% 5% 5% 7% 40%	1980
	21st to end	Night	12% 9% 5% 8% 7% 4 5% 4 6% 7% 33%	2178
April	1st to 10th	Night	8% 7% 3 6% 6% 2 5% 6% 6% 8% 42%	1766
	11th to 20th	Night	12% 11% 5% 8% 5% 2 6% 5% 5% 6% 36%	1599
	21st to end	Night	14% 9% 3 5% 6% 3 6% 5% 5% 7% 37%	1620
May	1st to 10th	Night	14% 6% 3 5% 6% 4 5% 4 5% 6% 43%	1616
	11th to 20th	Night	13% 7% 2 5% 5% 2 4 4 7% 7% 42%	1275
	21st to end	Night	17% 7% 2 4 4 3 3 4 5% 7% 44%	1358
June	1st to 10th	Night	11% 5% 2 4 6% 3 5% 5% 7% 9% 44%	1260
	11th to 20th	Night	11% 5% 3 4 6% 3 3 5% 7% 9% 45%	1260
	21st to end	Night	10% 4 2 4 5% 4 5% 5% 7% 9% 46%	1260
July	1st to 10th	Night	6% 3 2 4 4 3 3 4 5% 8% 59%	1260
	11th to 20th	Night	5% 3 2 3 4 2 5% 5% 7% 9% 55%	1260
	21st to end	Night	5% 3 1 3 4 3 4 4 6% 8% 60%	1490
August	1st to 10th	Night	7% 4 2 4 4 3 4 4 6% 7% 56%	1493
	11th to 20th	Night	7% 3 2 4 5% 3 4 4 5% 8% 54%	1600
	21st to end	Night	9% 3 1 3 4 3 4 5% 4 7% 55%	1782
September	1st to 10th	Night	10% 4 3 5% 4 2 3 4 5% 7% 55%	1752
	11th to 20th	Night	12% 4 2 4 4 2 4 4 5% 8% 51%	1980
	21st to end	Night	16% 5% 3 5% 5% 3 4 4 5% 7% 43%	1980
October	1st to 10th	Night	14% 8% 3 6% 6% 3 4 6% 4 7% 40%	2071
	11th to 20th	Night	14% 9% 3 5% 5% 3 5% 4 5% 7% 39%	2222
	21st to end	Night	11% 11% 4 7% 7% 3 5% 4 6% 7% 35%	2574
November	1st to 10th	Night	12% 10% 4 8% 6% 3 5% 5% 6% 8% 32%	2501
	11th to 20th	Night	10% 14% 7% 9% 7% 3 4 5% 5% 6% 30%	2660
	21st to end	Night	11% 13% 4 10% 9% 3 5% 5% 5% 7% 30%	2788
December	1st to 10th	Night	7% 11% 6% 11% 9% 4 6% 5% 5% 7% 28%	2850
	11th to 20th	Night	9% 13% 7% 13% 8% 5% 6% 5% 5% 6% 22%	3518
	21st to end	Night	11% 10% 5% 10% 9% 4 4 4 4 5% 33%	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	54% 9% 12% 19% 5% 1	1329
	11th to 20th	Day	61% 7% 11% 14% 6%	1353
	21st to end	Day	64% 7% 8% 14% 7%	1584
February	1st to 10th	Day	55% 7% 12% 17% 8% 1	1521
	11th to 20th	Day	53% 8% 13% 15% 10% 1	1583
	21st to end	Day	53% 7% 12% 19% 8% 1	1455
March	1st to 10th	Day	59% 8% 13% 14% 5%	1813
	11th to 20th	Day	49% 9% 14% 21% 7%	1980
	21st to end	Day	55% 8% 12% 17% 7%	2178
April	1st to 10th	Day	49% 7% 12% 22% 9% 1	2190
	11th to 20th	Day	51% 7% 12% 18% 11% 1	2312
	21st to end	Day	51% 7% 15% 17% 8% 2	2340
May	1st to 10th	Day	45% 6% 12% 24% 12% 1	2344
	11th to 20th	Day	44% 6% 12% 25% 12% 2	2623
	21st to end	Day	46% 7% 14% 22% 10% 1	2918
June	1st to 10th	Day	40% 9% 18% 22% 9% 1	2700
	11th to 20th	Day	43% 9% 15% 23% 9% 1	2700
	21st to end	Day	40% 10% 18% 25% 6% 1	2700
July	1st to 10th	Day	30% 9% 18% 33% 10% 1	2626
	11th to 20th	Day	34% 8% 17% 28% 12%	2619
	21st to end	Day	25% 9% 18% 34% 13% 1	2669
August	1st to 10th	Day	33% 11% 17% 28% 10% 1	2428
	11th to 20th	Day	32% 9% 19% 31% 9%	2301
	21st to end	Day	34% 7% 13% 32% 13% 1	2574
September	1st to 10th	Day	33% 7% 17% 30% 13% 1	2206
	11th to 20th	Day	40% 8% 17% 24% 9% 1	1980
	21st to end	Day	40% 7% 14% 31% 7%	1980
October	1st to 10th	Day	47% 7% 13% 24% 8%	1871
	11th to 20th	Day	47% 7% 14% 22% 9%	1735
	21st to end	Day	53% 8% 16% 18% 5% 1	1782
November	1st to 10th	Day	55% 8% 11% 19% 7% 1	1575
	11th to 20th	Day	58% 9% 12% 13% 7%	1520
	21st to end	Day	57% 9% 12% 16% 5%	1387
December	1st to 10th	Day	59% 8% 13% 15% 5%	1330
	11th to 20th	Day	61% 7% 11% 13% 6% 1	1680
	21st to end	Day	50% 7% 11% 22% 9%	2442
January	1st to 10th	Night	52% 8% 12% 19% 8%	2837
	11th to 20th	Night	61% 7% 10% 14% 8%	2682
	21st to end	Night	60% 7% 10% 13% 9%	2772
February	1st to 10th	Night	51% 8% 11% 17% 11% 1	2439
	11th to 20th	Night	46% 8% 15% 18% 13% 1	2274
	21st to end	Night	47% 7% 11% 22% 11% 1	1816
March	1st to 10th	Night	52% 8% 13% 18% 8% 1	2147
	11th to 20th	Night	43% 6% 12% 26% 11% 1	1980
	21st to end	Night	50% 8% 13% 17% 10% 1	2178
April	1st to 10th	Night	38% 8% 13% 24% 15% 3	1766
	11th to 20th	Night	49% 5% 10% 20% 14% 2	1599
	21st to end	Night	45% 7% 14% 21% 11% 2	1620
May	1st to 10th	Night	40% 5% 12% 28% 13% 1	1616
	11th to 20th	Night	39% 6% 12% 25% 16% 2	1275
	21st to end	Night	41% 6% 12% 24% 16% 1	1358
June	1st to 10th	Night	35% 9% 20% 26% 9% 2	1260
	11th to 20th	Night	35% 7% 16% 25% 14% 2	1260
	21st to end	Night	32% 11% 17% 31% 7% 1	1260
July	1st to 10th	Night	23% 7% 16% 38% 14% 2	1225
	11th to 20th	Night	23% 9% 17% 33% 16% 1	1218
	21st to end	Night	22% 7% 16% 38% 16% 2	1407
August	1st to 10th	Night	26% 7% 17% 35% 13% 2	1485
	11th to 20th	Night	28% 7% 20% 31% 12% 1	1600
	21st to end	Night	28% 7% 13% 34% 17% 1	1782
September	1st to 10th	Night	29% 6% 15% 31% 17% 1	1752
	11th to 20th	Night	31% 7% 18% 28% 14% 1	1980
	21st to end	Night	40% 6% 12% 31% 11% 1	1980
October	1st to 10th	Night	45% 9% 14% 24% 8% 1	2071
	11th to 20th	Night	44% 7% 12% 27% 10%	2222
	21st to end	Night	48% 8% 14% 24% 6% 1	2574
November	1st to 10th	Night	49% 8% 15% 18% 8% 2	2501
	11th to 20th	Night	55% 7% 14% 15% 7% 1	2660
	21st to end	Night	55% 8% 14% 16% 7%	2788
December	1st to 10th	Night	57% 7% 15% 16% 6%	2850
	11th to 20th	Night	62% 8% 14% 12% 5%	3516
	21st to end	Night	53% 7% 12% 18% 10% 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	10% 8% 35% 32% 12% 3	270
	11th to 20th	Day	10% 11% 36% 31% 10% 1	249
	21st to end	Day	14% 9% 34% 31% 11% 2	264
February	1st to 10th	Day	15% 11% 40% 30% 4 1	240
	11th to 20th	Day	9% 12% 38% 31% 8% 2	240
	21st to end	Day	8% 6% 48% 27% 10% 2	198
March	1st to 10th	Day	11% 8% 35% 35% 9% 2	240
	11th to 20th	Day	12% 9% 34% 28% 13% 5%	240
	21st to end	Day	14% 14% 31% 27% 11% 3	264
April	1st to 10th	Day	13% 19% 31% 28% 7% 2	450
	11th to 20th	Day	20% 12% 29% 26% 12% 1	590
	21st to end	Day	21% 12% 30% 25% 10% 2	600
May	1st to 10th	Day	16% 10% 32% 27% 12% 2	603
	11th to 20th	Day	20% 9% 30% 24% 14% 3	625
	21st to end	Day	19% 8% 26% 30% 15% 3	679
June	1st to 10th	Day	13% 11% 28% 26% 16% 6%	630
	11th to 20th	Day	15% 10% 36% 23% 13% 3	630
	21st to end	Day	11% 7% 28% 33% 17% 4	630
July	1st to 10th	Day	8% 6% 27% 33% 19% 8%	621
	11th to 20th	Day	11% 6% 31% 28% 19% 5%	618
	21st to end	Day	4 6% 25% 37% 21% 7%	684
August	1st to 10th	Day	7% 5% 27% 34% 20% 7%	626
	11th to 20th	Day	10% 5% 24% 32% 20% 9%	615
	21st to end	Day	11% 8% 27% 31% 19% 5%	693
September	1st to 10th	Day	13% 10% 31% 31% 13% 3	496
	11th to 20th	Day	17% 12% 28% 28% 11% 3	270
	21st to end	Day	21% 10% 32% 26% 11%	270
October	1st to 10th	Day	21% 10% 28% 27% 12% 1	270
	11th to 20th	Day	13% 11% 39% 28% 7% 2	270
	21st to end	Day	22% 11% 36% 21% 7% 3	297
November	1st to 10th	Day	23% 11% 28% 27% 10% 1	270
	11th to 20th	Day	14% 16% 38% 25% 6% 1	270
	21st to end	Day	17% 13% 37% 26% 7%	270
December	1st to 10th	Day	13% 9% 34% 31% 11% 3	270
	11th to 20th	Day	14% 14% 38% 28% 6%	270
	21st to end	Day	13% 9% 34% 28% 10% 4	297
January	1st to 10th	Night	11% 11% 36% 29% 11% 1	950
	11th to 20th	Night	15% 9% 35% 33% 7%	920
	21st to end	Night	14% 12% 38% 30% 7% 1	990
February	1st to 10th	Night	12% 10% 36% 33% 9% 1	900
	11th to 20th	Night	11% 8% 36% 32% 11% 2	879
	21st to end	Night	13% 7% 35% 33% 11% 2	632
March	1st to 10th	Night	15% 10% 32% 29% 13% 2	707
	11th to 20th	Night	10% 7% 38% 32% 11% 2	540
	21st to end	Night	18% 8% 28% 30% 12% 3	594
April	1st to 10th	Night	12% 9% 37% 31% 9% 1	540
	11th to 20th	Night	16% 7% 33% 31% 12% 1	533
	21st to end	Night	19% 7% 25% 37% 11% 1	540
May	1st to 10th	Night	18% 4 32% 33% 12% 1	540
	11th to 20th	Night	16% 7% 29% 33% 15%	531
	21st to end	Night	20% 8% 29% 34% 10% 1	584
June	1st to 10th	Night	13% 7% 27% 37% 15% 1	540
	11th to 20th	Night	14% 5% 32% 32% 17%	540
	21st to end	Night	10% 5% 28% 38% 19% 1	540
July	1st to 10th	Night	5% 4 27% 39% 23% 1	525
	11th to 20th	Night	7% 6% 29% 37% 21% 1	522
	21st to end	Night	6% 3 25% 43% 21% 2	591
August	1st to 10th	Night	8% 3 22% 46% 20% 1	537
	11th to 20th	Night	9% 4 25% 37% 22% 3	534
	21st to end	Night	11% 4 26% 39% 18% 1	594
September	1st to 10th	Night	12% 4 30% 35% 17% 2	540
	11th to 20th	Night	12% 6% 28% 40% 13% 1	540
	21st to end	Night	17% 6% 32% 31% 13%	540
October	1st to 10th	Night	18% 9% 34% 30% 8% 1	631
	11th to 20th	Night	19% 9% 32% 30% 10%	782
	21st to end	Night	16% 12% 37% 25% 9% 1	990
November	1st to 10th	Night	16% 12% 34% 28% 8% 1	925
	11th to 20th	Night	15% 11% 38% 27% 7% 2	950
	21st to end	Night	18% 13% 38% 25% 5% 1	950
December	1st to 10th	Night	12% 11% 35% 32% 9% 1	950
	11th to 20th	Night	15% 11% 34% 30% 9% 1	950
	21st to end	Night	20% 7% 35% 29% 9% 1	1045

Page generated at 2024-01-11 12:31:58. Version ac07

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