Ashland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ashland 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	8% 9% 3 6% 4 3 3 3 4 6% 51%	105322
	Night	9% 11% 3 7% 4 4 4 3 4 6% 45%	102384
Transparency	Day	33% 6% 10% 21% 19% 11%	105073
	Night	38% 8% 10% 20% 16% 7%	102223
Seeing	Day	16% 16% 28% 26% 12% 3	14942
	Night	15% 9% 19% 33% 21% 3	23986

By Month

Percentage Cloud Cover SW (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% 23% 5% 10% 5% 4 5% 4 4 6% 21%	2539
	11th to 20th	Day	20% 18% 4 9% 5% 5% 5% 3 4 5% 23%	2682
	21st to end	Day	14% 14% 5% 9% 5% 5% 5% 4 6% 7% 27%	3146
February	1st to 10th	Day	7% 15% 4 9% 5% 6% 6% 4 8% 6% 30%	1710
	11th to 20th	Day	9% 16% 4 8% 5% 4 5% 3 6% 7% 33%	1665
	21st to end	Day	11% 21% 5% 8% 6% 4 3 3 4 6% 29%	1539
March	1st to 10th	Day	11% 21% 7% 11% 6% 5% 5% 3 4 4 24%	3347
	11th to 20th	Day	8% 14% 3 5% 4 4 3 3 5% 5% 46%	3490
	21st to end	Day	12% 20% 5% 10% 7% 5% 5% 4 6% 6% 21%	3880
April	1st to 10th	Day	12% 19% 5% 9% 5% 4 4 3 4 6% 28%	2280
	11th to 20th	Day	14% 17% 4 7% 5% 4 3 3 5% 7% 30%	2249
	21st to end	Day	10% 14% 4 7% 5% 4 4 3 6% 8% 35%	2368
May	1st to 10th	Day	10% 12% 4 6% 4 3 3 2 4 6% 46%	4169
	11th to 20th	Day	7% 6% 2 4 2 3 2 3 5% 6% 60%	4377
	21st to end	Day	9% 9% 2 5% 3 3 3 3 5% 8% 49%	4813
June	1st to 10th	Day	11% 9% 2 5% 5% 4 4 3 6% 8% 43%	2660
	11th to 20th	Day	7% 6% 2 5% 4 4 3 3 5% 7% 54%	2660
	21st to end	Day	5% 3 1 2 2 2 3 2 4 5% 70%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 1 2 3 87%	4420
	11th to 20th	Day	2 2 1 2 2 2 3 2 2 3 79%	4420
	21st to end	Day	1 1 1 1 2 1 2 2 3 86%	4561
August	1st to 10th	Day	2 2 1 2 2 3 3 2 3 5% 74%	4091
	11th to 20th	Day	1 1 1 2 1 2 2 2 3 5% 79%	4026
	21st to end	Day	2 2 1 3 2 2 2 2 3 4 77%	4194
September	1st to 10th	Day	2 2 1 2 2 1 1 2 4 5% 78%	2280
	11th to 20th	Day	4 4 1 4 3 3 3 4 6% 7% 60%	2280
	21st to end	Day	6% 4 1 4 3 2 3 3 5% 7% 63%	1995
October	1st to 10th	Day	5% 3 1 3 3 2 3 2 3 4 70%	3180
	11th to 20th	Day	6% 6% 2 4 4 4 5% 4 5% 8% 52%	3161
	21st to end	Day	10% 10% 3 8% 5% 4 4 4 5% 7% 40%	3448
November	1st to 10th	Day	15% 13% 3 7% 5% 4 4 4 4 8% 33%	1740
	11th to 20th	Day	16% 10% 3 8% 4 5% 6% 5% 8% 8% 28%	1530
	21st to end	Day	12% 15% 3 7% 4 5% 4 3 5% 7% 35%	1520
December	1st to 10th	Day	10% 11% 2 7% 6% 3 5% 4 6% 7% 38%	1520
	11th to 20th	Day	13% 15% 4 8% 6% 6% 5% 4 6% 9% 23%	1928
	21st to end	Day	13% 16% 4 9% 6% 5% 6% 5% 6% 8% 21%	2794
January	1st to 10th	Night	14% 21% 6% 10% 5% 5% 5% 4 6% 6% 18%	4406
	11th to 20th	Night	18% 18% 6% 8% 4 4 4 3 4 6% 25%	4267
	21st to end	Night	16% 18% 5% 11% 5% 5% 4 3 5% 5% 24%	4521
February	1st to 10th	Night	9% 14% 5% 10% 5% 5% 4 4 6% 6% 31%	2470
	11th to 20th	Night	11% 17% 5% 8% 5% 4 5% 3 4 6% 32%	2402
	21st to end	Night	9% 18% 6% 10% 5% 4 5% 4 6% 6% 28%	1914
March	1st to 10th	Night	12% 19% 6% 11% 6% 4 4 3 5% 6% 23%	3525
	11th to 20th	Night	8% 13% 4 7% 4 4 3 3 4 5% 47%	3490
	21st to end	Night	9% 21% 6% 11% 6% 6% 5% 3 5% 5% 22%	3772
April	1st to 10th	Night	11% 18% 5% 10% 4 4 4 4 5% 6% 29%	1900
	11th to 20th	Night	11% 17% 4 7% 4 3 4 4 5% 6% 34%	1879
	21st to end	Night	14% 15% 4 6% 3 2 3 3 6% 10% 33%	1809
May	1st to 10th	Night	12% 16% 4 8% 4 2 3 2 3 5% 41%	2796
	11th to 20th	Night	6% 6% 3 6% 3 3 3 3 4 5% 59%	2516
	21st to end	Night	10% 12% 3 5% 3 2 3 3 4 6% 49%	2762
June	1st to 10th	Night	11% 9% 2 6% 5% 4 4 3 6% 6% 44%	1520
	11th to 20th	Night	7% 9% 3 6% 4 3 3 3 5% 5% 53%	1520
	21st to end	Night	5% 4 1 3 2 2 2 2 4 5% 70%	1520
July	1st to 10th	Night	1 2 1 1 2 1 1 2 3 85%	2540
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 4 78%	2540
	21st to end	Night	1 1 1 1 1 2 2 1 2 3 85%	2981
August	1st to 10th	Night	2 2 1 2 2 2 2 3 4 5% 77%	2848
	11th to 20th	Night	1 1 2 1 2 2 2 3 4 80%	2812
	21st to end	Night	5% 3 1 3 1 2 2 1 3 4 75%	3484
September	1st to 10th	Night	2 2 1 2 1 1 2 2 3 5% 79%	1900
	11th to 20th	Night	4 4 1 4 3 3 3 3 6% 6% 62%	1900
	21st to end	Night	8% 6% 2 4 2 2 3 2 4 5% 62%	2178
October	1st to 10th	Night	4 4 1 3 2 3 3 2 3 4 70%	3800
	11th to 20th	Night	9% 7% 2 6% 3 3 3 2 4 6% 55%	3777
	21st to end	Night	7% 9% 3 7% 5% 5% 5% 4 7% 7% 41%	4121
November	1st to 10th	Night	15% 14% 4 8% 4 4 5% 3 4 6% 32%	2410
	11th to 20th	Night	16% 11% 2 7% 5% 5% 6% 5% 7% 8% 28%	2646
	21st to end	Night	12% 14% 4 6% 4 4 4 3 5% 7% 37%	2660
December	1st to 10th	Night	12% 12% 3 7% 4 4 3 4 6% 7% 37%	2660
	11th to 20th	Night	11% 16% 4 10% 6% 7% 6% 5% 6% 7% 23%	3276
	21st to end	Night	14% 17% 5% 9% 5% 6% 5% 4 5% 7% 24%	4862

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	62% 10% 13% 10% 4 1	2539
	11th to 20th	Day	64% 6% 7% 11% 7% 4	2682
	21st to end	Day	53% 9% 14% 13% 7% 3	3146
February	1st to 10th	Day	50% 10% 15% 14% 9% 2	1710
	11th to 20th	Day	50% 8% 12% 19% 9% 2	1674
	21st to end	Day	56% 7% 9% 17% 9% 2	1539
March	1st to 10th	Day	60% 8% 8% 16% 6%	3347
	11th to 20th	Day	38% 9% 10% 18% 24% 1	3490
	21st to end	Day	59% 11% 13% 13% 3	3880
April	1st to 10th	Day	56% 8% 13% 14% 8% 2	2280
	11th to 20th	Day	51% 8% 14% 15% 9% 4	2252
	21st to end	Day	43% 9% 15% 21% 11% 1	2368
May	1st to 10th	Day	36% 9% 12% 25% 17% 2	4169
	11th to 20th	Day	23% 5% 9% 27% 31% 4	4380
	21st to end	Day	27% 9% 18% 35% 10%	4814
June	1st to 10th	Day	37% 8% 15% 28% 12% 1	2660
	11th to 20th	Day	26% 8% 11% 34% 18% 3	2660
	21st to end	Day	17% 4 9% 30% 30% 10%	2660
July	1st to 10th	Day	6% 2 4 16% 21% 51%	4351
	11th to 20th	Day	11% 3 3 13% 26% 44%	4345
	21st to end	Day	6% 2 3 18% 41% 29%	4417
August	1st to 10th	Day	14% 3 5% 17% 33% 28%	4076
	11th to 20th	Day	9% 3 6% 31% 35% 15%	4065
	21st to end	Day	13% 3 5% 31% 32% 17%	4193
September	1st to 10th	Day	10% 3 4 21% 33% 29%	2280
	11th to 20th	Day	22% 5% 10% 25% 27% 12%	2280
	21st to end	Day	22% 6% 9% 23% 25% 16%	1995
October	1st to 10th	Day	19% 4 11% 15% 24% 27%	3180
	11th to 20th	Day	28% 6% 17% 30% 15% 4	3161
	21st to end	Day	39% 6% 10% 23% 17% 5%	3448
November	1st to 10th	Day	49% 7% 12% 17% 13% 2	1740
	11th to 20th	Day	51% 10% 13% 12% 10% 4	1530
	21st to end	Day	50% 5% 12% 14% 12% 6%	1520
December	1st to 10th	Day	44% 8% 13% 18% 14% 3	1520
	11th to 20th	Day	57% 9% 15% 12% 7% 1	1928
	21st to end	Day	59% 11% 11% 14% 4 1	2794
January	1st to 10th	Night	62% 11% 10% 11% 4 1	4406
	11th to 20th	Night	60% 7% 9% 11% 8% 4	4267
	21st to end	Night	62% 8% 7% 11% 9% 3	4521
February	1st to 10th	Night	50% 8% 13% 16% 11% 2	2470
	11th to 20th	Night	53% 9% 10% 17% 9% 2	2404
	21st to end	Night	52% 11% 13% 14% 8% 2	1914
March	1st to 10th	Night	57% 10% 12% 15% 5%	3525
	11th to 20th	Night	38% 8% 9% 21% 22% 1	3490
	21st to end	Night	56% 14% 13% 12% 4	3772
April	1st to 10th	Night	52% 9% 16% 15% 7% 1	1900
	11th to 20th	Night	47% 10% 15% 16% 8% 4	1879
	21st to end	Night	44% 10% 17% 20% 7% 1	1809
May	1st to 10th	Night	36% 12% 14% 23% 14% 1	2796
	11th to 20th	Night	22% 11% 10% 39% 15% 4	2516
	21st to end	Night	26% 16% 25% 30% 3	2762
June	1st to 10th	Night	38% 9% 16% 31% 5%	1520
	11th to 20th	Night	28% 9% 14% 33% 15% 1	1520
	21st to end	Night	17% 5% 12% 40% 21% 6%	1520
July	1st to 10th	Night	7% 3 5% 18% 20% 47%	2500
	11th to 20th	Night	12% 3 4 15% 33% 34%	2492
	21st to end	Night	7% 2 4 20% 47% 20%	2888
August	1st to 10th	Night	11% 3 5% 21% 47% 13%	2839
	11th to 20th	Night	8% 3 8% 40% 29% 11%	2839
	21st to end	Night	16% 3 7% 33% 31% 10%	3484
September	1st to 10th	Night	9% 2 7% 23% 35% 24%	1900
	11th to 20th	Night	20% 4 13% 25% 27% 10%	1900
	21st to end	Night	25% 4 10% 24% 19% 18%	2178
October	1st to 10th	Night	19% 5% 7% 17% 28% 24%	3800
	11th to 20th	Night	31% 5% 11% 35% 12% 6%	3777
	21st to end	Night	38% 7% 12% 19% 16% 7%	4121
November	1st to 10th	Night	51% 7% 11% 14% 12% 5%	2410
	11th to 20th	Night	51% 10% 11% 13% 10% 4	2646
	21st to end	Night	47% 7% 11% 13% 15% 7%	2660
December	1st to 10th	Night	44% 9% 9% 20% 15% 2	2660
	11th to 20th	Night	59% 9% 8% 13% 10% 1	3276
	21st to end	Night	56% 10% 11% 15% 6% 2	4862

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	32% 18% 28% 17% 4 2	180
	11th to 20th	Day	27% 18% 27% 16% 10% 3	270
	21st to end	Day	22% 19% 23% 23% 12%	407
February	1st to 10th	Day	19% 20% 29% 23% 7% 1	370
	11th to 20th	Day	25% 22% 23% 22% 6%	365
	21st to end	Day	23% 23% 28% 22% 5%	368
March	1st to 10th	Day	27% 21% 28% 18% 5%	460
	11th to 20th	Day	22% 19% 27% 22% 11%	460
	21st to end	Day	25% 26% 27% 17% 5%	506
April	1st to 10th	Day	24% 21% 28% 18% 7% 1	460
	11th to 20th	Day	29% 19% 26% 18% 5% 2	452
	21st to end	Day	22% 21% 27% 20% 8% 2	460
May	1st to 10th	Day	18% 22% 29% 21% 8% 2	463
	11th to 20th	Day	23% 18% 25% 20% 10% 3	488
	21st to end	Day	19% 13% 28% 25% 10% 5%	529
June	1st to 10th	Day	15% 19% 29% 20% 13% 4	490
	11th to 20th	Day	14% 20% 30% 24% 10% 2	490
	21st to end	Day	5% 13% 33% 29% 14% 6%	490
July	1st to 10th	Day	6% 12% 36% 28% 14% 6%	486
	11th to 20th	Day	2 9% 39% 29% 14% 6%	484
	21st to end	Day	2 8% 34% 31% 16% 8%	531
August	1st to 10th	Day	2 10% 33% 31% 17% 8%	487
	11th to 20th	Day	3 13% 25% 33% 18% 8%	477
	21st to end	Day	5% 9% 28% 36% 18% 4	539
September	1st to 10th	Day	3 10% 28% 38% 18% 3	490
	11th to 20th	Day	8% 12% 27% 35% 16% 2	490
	21st to end	Day	9% 11% 30% 32% 16% 1	490
October	1st to 10th	Day	12% 13% 27% 30% 18% 1	490
	11th to 20th	Day	16% 11% 22% 28% 21% 1	490
	21st to end	Day	18% 17% 26% 22% 15% 2	539
November	1st to 10th	Day	20% 16% 19% 30% 13% 1	318
	11th to 20th	Day	17% 13% 23% 33% 11% 3	185
	21st to end	Day	19% 14% 26% 29% 13%	180
December	1st to 10th	Day	24% 11% 30% 22% 9% 4	180
	11th to 20th	Day	27% 13% 24% 26% 8% 2	180
	21st to end	Day	24% 18% 26% 23% 10%	198
January	1st to 10th	Night	22% 13% 29% 25% 9% 2	760
	11th to 20th	Night	18% 15% 23% 28% 14% 2	760
	21st to end	Night	20% 12% 20% 33% 13% 3	836
February	1st to 10th	Night	17% 13% 23% 36% 11% 1	760
	11th to 20th	Night	20% 11% 24% 30% 13% 1	744
	21st to end	Night	17% 14% 25% 34% 11% 1	628
March	1st to 10th	Night	23% 14% 23% 28% 9% 3	760
	11th to 20th	Night	18% 12% 24% 28% 17% 2	760
	21st to end	Night	21% 17% 22% 27% 12% 1	836
April	1st to 10th	Night	19% 14% 22% 30% 13% 1	760
	11th to 20th	Night	20% 12% 23% 27% 16% 3	751
	21st to end	Night	23% 9% 18% 30% 18% 3	669
May	1st to 10th	Night	17% 9% 18% 33% 21% 1	532
	11th to 20th	Night	14% 7% 17% 37% 24% 2	374
	21st to end	Night	20% 7% 17% 30% 25% 2	411
June	1st to 10th	Night	13% 7% 14% 37% 27% 1	380
	11th to 20th	Night	10% 6% 21% 41% 21% 1	380
	21st to end	Night	7% 2 11% 44% 35% 1	380
July	1st to 10th	Night	2 2 11% 40% 44% 1	370
	11th to 20th	Night	4 1 10% 47% 37% 1	368
	21st to end	Night	1 1 6% 36% 51% 6%	548
August	1st to 10th	Night	3 1 6% 36% 47% 7%	567
	11th to 20th	Night	3 1 8% 37% 44% 8%	564
	21st to end	Night	3 3 17% 37% 36% 4	822
September	1st to 10th	Night	3 3 14% 38% 36% 5%	760
	11th to 20th	Night	6% 4 14% 35% 35% 6%	760
	21st to end	Night	12% 4 14% 34% 30% 7%	760
October	1st to 10th	Night	9% 3 17% 39% 28% 3	760
	11th to 20th	Night	13% 5% 15% 37% 25% 5%	760
	21st to end	Night	14% 8% 19% 33% 20% 6%	836
November	1st to 10th	Night	21% 9% 22% 31% 14% 4	754
	11th to 20th	Night	21% 9% 22% 34% 12% 1	760
	21st to end	Night	19% 9% 24% 31% 16% 2	760
December	1st to 10th	Night	18% 13% 20% 33% 13% 2	760
	11th to 20th	Night	22% 15% 23% 27% 11% 2	760
	21st to end	Night	26% 20% 24% 23% 7% 1	836

Page generated at 2024-11-01 19:47:52. Version ac07

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