Arden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arden clear sky chart from 2005-11-06 to 2024-11-04.

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	16% 10% 3 8% 5% 5% 4 4 5% 7% 33%	101564
	Night	17% 11% 3 8% 5% 4 4 4 5% 6% 32%	97456
Transparency	Day	49% 6% 12% 22% 10% 1	105099
	Night	50% 6% 12% 21% 10% 1	102010
Seeing	Day	23% 16% 31% 19% 9% 3	14480
	Night	22% 14% 31% 24% 9% 1	23639

By Month

Percentage Cloud Cover NE (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% 18% 5% 10% 6% 5% 4 3 5% 4 25%	2517
	11th to 20th	Day	13% 16% 7% 13% 6% 6% 5% 4 4 4 22%	2520
	21st to end	Day	18% 20% 6% 14% 6% 5% 3 2 3 4 19%	3037
February	1st to 10th	Day	14% 17% 4 12% 7% 5% 4 3 6% 5% 22%	1710
	11th to 20th	Day	12% 15% 5% 12% 5% 4 5% 4 4 5% 28%	1663
	21st to end	Day	19% 15% 5% 8% 7% 6% 4 3 5% 4 24%	1535
March	1st to 10th	Day	20% 14% 4 8% 5% 4 3 3 4 6% 29%	3235
	11th to 20th	Day	10% 18% 5% 9% 5% 5% 4 3 4 5% 31%	3480
	21st to end	Day	14% 10% 3 7% 3 4 3 3 4 6% 43%	3942
April	1st to 10th	Day	21% 14% 3 8% 5% 4 4 3 4 5% 31%	2280
	11th to 20th	Day	22% 10% 3 6% 4 4 4 3 4 5% 37%	2254
	21st to end	Day	22% 10% 3 8% 6% 4 4 3 4 4 32%	2408
May	1st to 10th	Day	20% 7% 3 7% 5% 4 5% 3 5% 6% 33%	4386
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 4 5% 7% 33%	4398
	21st to end	Day	14% 6% 2 6% 5% 4 5% 4 6% 8% 41%	4837
June	1st to 10th	Day	19% 9% 3 7% 5% 5% 5% 4 6% 7% 30%	2660
	11th to 20th	Day	16% 5% 2 6% 5% 5% 5% 4 6% 8% 37%	2660
	21st to end	Day	17% 8% 3 7% 6% 5% 5% 5% 5% 8% 32%	2660
July	1st to 10th	Day	11% 6% 2 6% 6% 5% 6% 4 7% 10% 36%	4440
	11th to 20th	Day	12% 5% 2 5% 5% 4 5% 5% 7% 10% 40%	4440
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 4 7% 8% 41%	4814
August	1st to 10th	Day	16% 8% 3 7% 4 4 5% 4 6% 7% 35%	4178
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 9% 35%	4044
	21st to end	Day	13% 6% 2 6% 4 4 5% 4 7% 10% 39%	4190
September	1st to 10th	Day	13% 7% 2 6% 5% 4 4 3 6% 7% 42%	2280
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 48%	2280
	21st to end	Day	19% 6% 2 6% 4 4 5% 2 6% 8% 38%	2003
October	1st to 10th	Day	19% 9% 3 7% 5% 4 4 3 5% 7% 35%	1900
	11th to 20th	Day	21% 10% 3 8% 6% 5% 4 3 6% 7% 28%	1900
	21st to end	Day	25% 12% 3 8% 5% 5% 4 3 5% 6% 25%	2006
November	1st to 10th	Day	15% 9% 3 8% 5% 5% 4 4 6% 6% 35%	1669
	11th to 20th	Day	17% 14% 4 9% 5% 5% 4 3 4 5% 29%	1520
	21st to end	Day	22% 14% 5% 9% 5% 5% 4 4 5% 6% 23%	1520
December	1st to 10th	Day	21% 17% 4 10% 6% 5% 5% 3 5% 6% 18%	1520
	11th to 20th	Day	19% 16% 5% 8% 5% 4 4 3 4 5% 26%	1906
	21st to end	Day	27% 18% 4 12% 5% 4 3 2 3 4 19%	2772
January	1st to 10th	Night	18% 14% 7% 11% 6% 6% 5% 4 5% 5% 19%	4429
	11th to 20th	Night	14% 15% 5% 13% 8% 7% 5% 3 6% 5% 20%	4440
	21st to end	Night	19% 17% 6% 12% 6% 5% 4 3 4 4 20%	4618
February	1st to 10th	Night	14% 16% 5% 10% 7% 4 4 5% 6% 6% 24%	2470
	11th to 20th	Night	13% 15% 5% 9% 6% 5% 4 4 6% 5% 29%	2403
	21st to end	Night	14% 14% 4 8% 6% 4 4 4 6% 6% 30%	1918
March	1st to 10th	Night	18% 12% 4 9% 5% 4 4 3 4 5% 31%	3601
	11th to 20th	Night	16% 16% 5% 9% 4 4 4 4 5% 6% 26%	3479
	21st to end	Night	15% 10% 3 7% 4 4 4 3 4 5% 40%	3690
April	1st to 10th	Night	21% 11% 3 6% 4 3 4 3 5% 6% 35%	1900
	11th to 20th	Night	19% 9% 3 7% 5% 3 4 3 5% 5% 38%	1875
	21st to end	Night	20% 9% 2 7% 4 4 4 4 5% 7% 34%	1787
May	1st to 10th	Night	22% 10% 3 7% 4 4 4 4 5% 6% 33%	2552
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 5% 7% 37%	2495
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 8% 43%	2738
June	1st to 10th	Night	16% 7% 3 7% 6% 6% 4 4 7% 8% 34%	1520
	11th to 20th	Night	12% 6% 3 5% 5% 4 4 4 6% 9% 42%	1520
	21st to end	Night	16% 6% 3 8% 5% 5% 5% 3 6% 8% 37%	1520
July	1st to 10th	Night	10% 5% 3 7% 6% 6% 5% 5% 6% 8% 39%	2520
	11th to 20th	Night	14% 5% 2 6% 3 4 3 3 6% 8% 46%	2520
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 6% 8% 46%	2739
August	1st to 10th	Night	12% 7% 2 6% 4 4 4 4 5% 8% 44%	2748
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 4 8% 44%	2785
	21st to end	Night	11% 4 2 6% 4 5% 5% 5% 7% 9% 41%	3434
September	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 5% 9% 46%	1900
	11th to 20th	Night	12% 4 2 5% 4 3 4 4 4 8% 51%	1900
	21st to end	Night	17% 5% 3 6% 4 4 4 4 6% 5% 43%	2171
October	1st to 10th	Night	15% 9% 3 6% 5% 4 5% 3 5% 6% 39%	2280
	11th to 20th	Night	21% 8% 3 8% 4 4 5% 4 6% 5% 32%	2280
	21st to end	Night	23% 10% 3 7% 5% 5% 5% 4 4 5% 29%	2591
November	1st to 10th	Night	17% 10% 3 6% 4 4 5% 4 5% 6% 36%	2481
	11th to 20th	Night	18% 11% 3 7% 5% 5% 5% 4 5% 6% 32%	2660
	21st to end	Night	21% 13% 3 9% 5% 5% 4 4 5% 6% 25%	2660
December	1st to 10th	Night	20% 16% 5% 10% 6% 4 5% 3 5% 5% 20%	2660
	11th to 20th	Night	19% 18% 4 8% 5% 4 4 3 4 5% 27%	3288
	21st to end	Night	29% 17% 4 9% 5% 4 4 3 4 4 16%	4884

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	58% 8% 15% 12% 6% 2	2518
	11th to 20th	Day	65% 5% 12% 11% 7%	2520
	21st to end	Day	72% 4 8% 10% 5% 1	3037
February	1st to 10th	Day	62% 6% 9% 17% 5% 1	1710
	11th to 20th	Day	58% 5% 10% 15% 10% 1	1672
	21st to end	Day	62% 4 9% 12% 11% 1	1535
March	1st to 10th	Day	57% 5% 11% 16% 10% 1	3238
	11th to 20th	Day	54% 6% 13% 15% 10% 2	3480
	21st to end	Day	41% 6% 7% 27% 16% 4	3942
April	1st to 10th	Day	56% 4 7% 18% 12% 3	2280
	11th to 20th	Day	48% 5% 7% 21% 16% 2	2254
	21st to end	Day	55% 4 8% 16% 14% 4	2408
May	1st to 10th	Day	50% 6% 10% 22% 10% 2	4400
	11th to 20th	Day	49% 7% 13% 20% 9% 2	4402
	21st to end	Day	40% 7% 13% 24% 15% 2	4837
June	1st to 10th	Day	51% 7% 10% 18% 12% 1	2660
	11th to 20th	Day	43% 5% 12% 25% 13% 2	2660
	21st to end	Day	48% 6% 14% 19% 12% 1	2660
July	1st to 10th	Day	41% 7% 14% 25% 12% 1	4370
	11th to 20th	Day	36% 7% 15% 33% 9%	4365
	21st to end	Day	38% 7% 14% 30% 11%	4661
August	1st to 10th	Day	46% 6% 14% 22% 12%	4164
	11th to 20th	Day	44% 6% 14% 27% 8% 1	4083
	21st to end	Day	39% 6% 14% 30% 10%	4190
September	1st to 10th	Day	39% 6% 14% 28% 13% 1	2280
	11th to 20th	Day	35% 6% 12% 31% 15% 1	2280
	21st to end	Day	44% 5% 14% 27% 10%	2003
October	1st to 10th	Day	43% 5% 12% 31% 9%	3160
	11th to 20th	Day	46% 5% 14% 25% 10% 1	3140
	21st to end	Day	52% 5% 14% 21% 7%	3283
November	1st to 10th	Day	47% 7% 15% 22% 9% 1	1669
	11th to 20th	Day	56% 6% 12% 16% 10% 1	1520
	21st to end	Day	61% 8% 12% 10% 8%	1520
December	1st to 10th	Day	67% 6% 12% 11% 5%	1520
	11th to 20th	Day	61% 6% 14% 12% 6%	1906
	21st to end	Day	71% 4 7% 14% 5%	2772
January	1st to 10th	Night	64% 6% 14% 12% 4	4429
	11th to 20th	Night	64% 6% 13% 11% 5% 1	4440
	21st to end	Night	67% 6% 10% 11% 6% 1	4618
February	1st to 10th	Night	59% 6% 11% 18% 6%	2470
	11th to 20th	Night	56% 5% 10% 20% 9% 1	2405
	21st to end	Night	55% 5% 10% 19% 11% 1	1918
March	1st to 10th	Night	54% 6% 8% 22% 10% 1	3611
	11th to 20th	Night	56% 6% 13% 16% 8% 1	3480
	21st to end	Night	42% 8% 8% 23% 16% 3	3690
April	1st to 10th	Night	52% 4 7% 21% 14% 2	1900
	11th to 20th	Night	48% 5% 9% 20% 17% 1	1875
	21st to end	Night	49% 6% 10% 16% 16% 3	1787
May	1st to 10th	Night	51% 6% 10% 19% 12% 2	2558
	11th to 20th	Night	45% 6% 13% 25% 9% 2	2496
	21st to end	Night	37% 7% 14% 22% 18% 2	2739
June	1st to 10th	Night	46% 8% 12% 21% 12% 1	1520
	11th to 20th	Night	38% 7% 13% 22% 18% 2	1520
	21st to end	Night	44% 8% 14% 20% 13% 1	1520
July	1st to 10th	Night	41% 6% 13% 23% 16% 2	2480
	11th to 20th	Night	36% 6% 13% 34% 11%	2472
	21st to end	Night	35% 8% 14% 30% 12% 1	2651
August	1st to 10th	Night	38% 7% 14% 26% 13% 1	2738
	11th to 20th	Night	38% 6% 14% 31% 10% 1	2812
	21st to end	Night	36% 8% 15% 29% 11% 1	3434
September	1st to 10th	Night	35% 6% 14% 30% 14% 1	1900
	11th to 20th	Night	32% 6% 15% 32% 14% 1	1900
	21st to end	Night	42% 4 11% 30% 11% 1	2171
October	1st to 10th	Night	39% 5% 11% 27% 17%	3800
	11th to 20th	Night	44% 5% 15% 26% 10%	3779
	21st to end	Night	50% 6% 13% 24% 8%	4264
November	1st to 10th	Night	47% 6% 13% 23% 10% 1	2481
	11th to 20th	Night	52% 7% 11% 19% 10% 2	2660
	21st to end	Night	58% 7% 13% 16% 6%	2660
December	1st to 10th	Night	64% 6% 11% 14% 4	2660
	11th to 20th	Night	61% 5% 11% 15% 8% 1	3288
	21st to end	Night	71% 5% 9% 12% 3	4884

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	27% 22% 32% 16% 3 1	180
	11th to 20th	Day	31% 19% 31% 15% 3 1	180
	21st to end	Day	26% 19% 35% 15% 4	274
February	1st to 10th	Day	31% 27% 30% 10% 2	270
	11th to 20th	Day	29% 26% 40% 5%	270
	21st to end	Day	36% 22% 30% 10% 1	347
March	1st to 10th	Day	27% 21% 33% 16% 4	460
	11th to 20th	Day	28% 20% 33% 15% 4	460
	21st to end	Day	34% 20% 27% 13% 5% 1	506
April	1st to 10th	Day	30% 22% 29% 15% 4	460
	11th to 20th	Day	34% 22% 21% 15% 7% 2	452
	21st to end	Day	31% 20% 30% 11% 6% 2	460
May	1st to 10th	Day	26% 15% 32% 17% 7% 3	463
	11th to 20th	Day	17% 17% 37% 18% 9% 1	487
	21st to end	Day	17% 18% 33% 20% 9% 4	529
June	1st to 10th	Day	26% 10% 35% 21% 7% 1	490
	11th to 20th	Day	16% 17% 33% 21% 13% 2	490
	21st to end	Day	21% 14% 32% 22% 9% 2	490
July	1st to 10th	Day	13% 9% 30% 30% 14% 3	485
	11th to 20th	Day	16% 10% 30% 26% 14% 4	484
	21st to end	Day	14% 9% 35% 27% 12% 4	532
August	1st to 10th	Day	13% 8% 31% 28% 15% 5%	486
	11th to 20th	Day	13% 7% 28% 29% 17% 6%	479
	21st to end	Day	16% 11% 29% 25% 13% 7%	539
September	1st to 10th	Day	15% 12% 32% 23% 12% 6%	490
	11th to 20th	Day	13% 8% 26% 23% 18% 12%	490
	21st to end	Day	19% 11% 29% 22% 14% 4	490
October	1st to 10th	Day	26% 13% 29% 16% 11% 4	490
	11th to 20th	Day	25% 21% 30% 17% 5% 1	490
	21st to end	Day	30% 19% 28% 19% 4	494
November	1st to 10th	Day	28% 15% 29% 18% 9%	345
	11th to 20th	Day	29% 21% 31% 13% 4 2	180
	21st to end	Day	27% 23% 32% 13% 3 1	180
December	1st to 10th	Day	31% 23% 32% 11% 2 1	180
	11th to 20th	Day	36% 23% 27% 11% 3 1	180
	21st to end	Day	36% 20% 31% 10% 3 1	198
January	1st to 10th	Night	28% 19% 30% 19% 4	760
	11th to 20th	Night	28% 17% 29% 20% 5% 1	760
	21st to end	Night	21% 16% 36% 22% 5%	836
February	1st to 10th	Night	23% 20% 36% 18% 3	760
	11th to 20th	Night	22% 19% 39% 16% 4	743
	21st to end	Night	25% 20% 34% 18% 3	628
March	1st to 10th	Night	23% 17% 35% 21% 3	760
	11th to 20th	Night	27% 18% 30% 21% 4 1	760
	21st to end	Night	23% 16% 34% 19% 7% 1	836
April	1st to 10th	Night	27% 17% 32% 21% 3	760
	11th to 20th	Night	24% 21% 29% 19% 6% 1	751
	21st to end	Night	25% 13% 29% 23% 10%	647
May	1st to 10th	Night	26% 8% 25% 29% 10% 1	405
	11th to 20th	Night	15% 10% 34% 33% 7%	374
	21st to end	Night	12% 9% 39% 26% 13%	411
June	1st to 10th	Night	17% 8% 32% 33% 9% 1	380
	11th to 20th	Night	14% 10% 30% 31% 13% 2	380
	21st to end	Night	20% 7% 26% 36% 11%	380
July	1st to 10th	Night	8% 5% 32% 39% 15%	370
	11th to 20th	Night	13% 3 29% 36% 18% 1	368
	21st to end	Night	11% 4 29% 43% 13% 1	416
August	1st to 10th	Night	13% 5% 24% 37% 20% 2	516
	11th to 20th	Night	13% 5% 21% 36% 23% 2	564
	21st to end	Night	13% 6% 30% 30% 18% 2	807
September	1st to 10th	Night	12% 6% 31% 30% 17% 3	760
	11th to 20th	Night	14% 6% 23% 27% 25% 6%	760
	21st to end	Night	20% 11% 22% 28% 18% 2	760
October	1st to 10th	Night	21% 12% 28% 23% 14% 2	760
	11th to 20th	Night	26% 13% 30% 23% 8% 1	760
	21st to end	Night	29% 14% 30% 22% 6%	836
November	1st to 10th	Night	24% 14% 30% 24% 8%	755
	11th to 20th	Night	25% 16% 33% 17% 8% 1	760
	21st to end	Night	30% 17% 28% 19% 6%	760
December	1st to 10th	Night	31% 18% 30% 18% 3	760
	11th to 20th	Night	27% 20% 33% 18% 2 1	760
	21st to end	Night	35% 15% 32% 16% 2	836

Page generated at 2024-11-01 22:47:50. Version ac07

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