Deerlick Astronomy Village
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deerlick Astronomy Village clear sky chart from 2005-11-06 to 2024-05-13.

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	13% 6% 2 6% 4 4 5% 4 6% 7% 42%	83939
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 44%	85575
Transparency	Day	38% 8% 11% 18% 18% 6%	83662
	Night	37% 8% 11% 18% 20% 7%	85371
Seeing	Day	16% 9% 24% 24% 19% 8%	14413
	Night	15% 9% 23% 30% 20% 3	24547

By Month

Percentage Cloud Cover SE (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	17% 6% 2 5% 3 4 5% 3 6% 7% 42%	2836
	11th to 20th	Day	13% 5% 2 4 3 3 3 3 5% 6% 53%	2840
	21st to end	Day	22% 8% 2 6% 3 3 2 2 3 4 44%	3124
February	1st to 10th	Day	16% 7% 3 7% 4 3 4 4 5% 7% 40%	1872
	11th to 20th	Day	21% 6% 1 5% 3 3 4 3 5% 4 45%	1848
	21st to end	Day	18% 7% 2 7% 3 3 4 3 5% 6% 43%	1570
March	1st to 10th	Day	23% 9% 3 6% 3 4 4 3 3 5% 37%	3371
	11th to 20th	Day	11% 4 2 5% 4 4 4 4 5% 7% 52%	3480
	21st to end	Day	19% 6% 2 6% 4 4 4 3 4 5% 42%	3815
April	1st to 10th	Day	11% 4 2 6% 4 4 5% 4 5% 6% 49%	2090
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 3 5% 7% 48%	2195
	21st to end	Day	8% 4 2 4 4 4 5% 4 6% 8% 52%	2470
May	1st to 10th	Day	9% 5% 2 5% 4 3 5% 4 6% 9% 49%	2470
	11th to 20th	Day	11% 6% 2 7% 5% 6% 6% 4 6% 8% 41%	2329
	21st to end	Day	11% 6% 2 6% 4 4 6% 4 7% 8% 41%	2531
June	1st to 10th	Day	10% 6% 3 7% 6% 6% 6% 6% 8% 9% 33%	2340
	11th to 20th	Day	7% 4 2 6% 5% 6% 6% 5% 7% 10% 43%	2340
	21st to end	Day	6% 4 3 6% 6% 6% 7% 6% 10% 11% 37%	2340
July	1st to 10th	Day	8% 5% 3 8% 8% 6% 7% 6% 9% 9% 31%	2340
	11th to 20th	Day	8% 6% 3 8% 7% 6% 6% 6% 9% 11% 31%	2340
	21st to end	Day	6% 5% 2 8% 7% 6% 8% 7% 9% 12% 30%	2547
August	1st to 10th	Day	9% 7% 2 9% 7% 7% 6% 6% 9% 11% 27%	2327
	11th to 20th	Day	10% 6% 3 10% 6% 6% 6% 5% 9% 9% 30%	2300
	21st to end	Day	14% 8% 3 7% 6% 6% 7% 5% 8% 9% 29%	2293
September	1st to 10th	Day	9% 7% 3 6% 5% 5% 6% 5% 7% 8% 39%	1980
	11th to 20th	Day	13% 6% 2 7% 5% 4 4 3 6% 7% 41%	1980
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 6% 44%	1980
October	1st to 10th	Day	15% 5% 2 5% 3 2 3 3 5% 6% 51%	1980
	11th to 20th	Day	13% 4 2 4 3 3 3 3 4 6% 56%	1800
	21st to end	Day	11% 4 2 5% 4 4 3 2 4 4 56%	1980
November	1st to 10th	Day	12% 5% 2 5% 4 3 4 3 4 5% 54%	1824
	11th to 20th	Day	14% 6% 2 3 3 3 3 2 4 6% 54%	1710
	21st to end	Day	13% 6% 2 5% 4 3 4 4 5% 6% 48%	1710
December	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 4 6% 6% 38%	1710
	11th to 20th	Day	17% 5% 2 6% 3 4 3 3 5% 5% 48%	2153
	21st to end	Day	20% 8% 3 5% 4 3 3 3 5% 6% 41%	3124
January	1st to 10th	Night	17% 6% 2 5% 4 4 4 4 5% 6% 44%	4109
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 47%	4120
	21st to end	Night	20% 9% 3 6% 3 3 3 3 3 4 43%	4532
February	1st to 10th	Night	16% 6% 2 5% 4 4 4 3 5% 6% 45%	2304
	11th to 20th	Night	19% 7% 2 6% 4 3 3 3 4 5% 44%	2218
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 44%	1884
March	1st to 10th	Night	23% 8% 2 6% 4 3 4 3 4 6% 36%	3480
	11th to 20th	Night	12% 5% 2 4 3 3 4 4 6% 8% 51%	3480
	21st to end	Night	19% 6% 2 6% 4 4 4 3 4 6% 42%	3817
April	1st to 10th	Night	10% 5% 2 6% 4 4 3 3 5% 7% 50%	2090
	11th to 20th	Night	11% 5% 2 4 4 3 3 3 5% 8% 52%	1949
	21st to end	Night	8% 4 1 4 4 5% 4 3 5% 7% 55%	1710
May	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 8% 52%	1710
	11th to 20th	Night	8% 4 2 6% 5% 6% 7% 4 7% 9% 42%	1619
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 5% 7% 7% 42%	1744
June	1st to 10th	Night	8% 7% 3 6% 5% 6% 5% 5% 8% 12% 34%	1620
	11th to 20th	Night	6% 4 2 6% 5% 4 5% 5% 7% 12% 44%	1620
	21st to end	Night	7% 5% 2 5% 5% 4 7% 7% 9% 11% 38%	1620
July	1st to 10th	Night	8% 6% 3 6% 6% 6% 6% 6% 9% 12% 32%	1620
	11th to 20th	Night	5% 6% 2 8% 5% 7% 7% 7% 10% 12% 31%	1620
	21st to end	Night	6% 6% 2 5% 5% 6% 6% 6% 9% 14% 35%	1771
August	1st to 10th	Night	7% 5% 3 8% 6% 7% 6% 6% 8% 11% 31%	1611
	11th to 20th	Night	11% 5% 2 6% 6% 5% 5% 6% 9% 12% 34%	1598
	21st to end	Night	10% 7% 3 8% 5% 5% 5% 6% 7% 10% 33%	2040
September	1st to 10th	Night	10% 6% 2 6% 4 6% 5% 6% 7% 10% 39%	1980
	11th to 20th	Night	13% 6% 2 7% 5% 5% 5% 3 5% 8% 41%	1980
	21st to end	Night	13% 6% 2 6% 4 4 4 3 5% 6% 48%	1980
October	1st to 10th	Night	13% 5% 1 4 4 4 3 4 5% 6% 53%	1980
	11th to 20th	Night	12% 4 1 5% 3 3 3 3 4 5% 56%	2160
	21st to end	Night	11% 4 1 5% 4 4 4 3 4 6% 56%	2376
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 5% 56%	2249
	11th to 20th	Night	14% 6% 2 5% 3 3 3 4 4 5% 52%	2470
	21st to end	Night	14% 5% 2 5% 4 3 4 4 5% 7% 48%	2470
December	1st to 10th	Night	15% 7% 2 6% 3 4 4 4 6% 6% 44%	2470
	11th to 20th	Night	17% 6% 2 5% 3 3 3 2 4 6% 51%	3042
	21st to end	Night	18% 9% 2 7% 4 4 4 4 5% 6% 37%	4532

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	37% 7% 8% 18% 23% 7%	2837
	11th to 20th	Day	32% 5% 6% 20% 27% 11%	2840
	21st to end	Day	45% 3 4 17% 22% 8%	3124
February	1st to 10th	Day	43% 5% 10% 18% 17% 7%	1872
	11th to 20th	Day	41% 5% 5% 20% 22% 8%	1858
	21st to end	Day	42% 7% 8% 13% 21% 9%	1570
March	1st to 10th	Day	49% 6% 7% 13% 14% 10%	3371
	11th to 20th	Day	31% 6% 9% 16% 25% 12%	3480
	21st to end	Day	43% 6% 7% 19% 20% 4	3815
April	1st to 10th	Day	35% 6% 11% 19% 22% 7%	2090
	11th to 20th	Day	35% 6% 10% 18% 21% 10%	2195
	21st to end	Day	29% 7% 11% 26% 23% 4	2470
May	1st to 10th	Day	31% 7% 13% 23% 21% 5%	2470
	11th to 20th	Day	40% 8% 16% 19% 16% 1	2333
	21st to end	Day	36% 9% 14% 22% 16% 2	2531
June	1st to 10th	Day	41% 11% 17% 19% 11% 2	2340
	11th to 20th	Day	33% 11% 18% 25% 12% 1	2340
	21st to end	Day	35% 13% 19% 18% 11% 4	2340
July	1st to 10th	Day	41% 15% 17% 16% 8% 3	2275
	11th to 20th	Day	40% 14% 21% 16% 6% 3	2271
	21st to end	Day	37% 16% 21% 18% 7% 1	2405
August	1st to 10th	Day	45% 13% 18% 18% 5% 1	2314
	11th to 20th	Day	45% 13% 16% 16% 8% 2	2300
	21st to end	Day	47% 12% 16% 15% 8% 2	2293
September	1st to 10th	Day	38% 11% 14% 16% 16% 4	1980
	11th to 20th	Day	41% 8% 10% 17% 21% 3	1980
	21st to end	Day	40% 6% 11% 18% 19% 6%	1980
October	1st to 10th	Day	33% 5% 9% 21% 25% 7%	1980
	11th to 20th	Day	29% 4 9% 23% 27% 8%	1800
	21st to end	Day	31% 5% 5% 16% 29% 12%	1980
November	1st to 10th	Day	33% 5% 7% 16% 26% 13%	1824
	11th to 20th	Day	32% 4 8% 21% 23% 12%	1710
	21st to end	Day	35% 7% 7% 20% 24% 7%	1710
December	1st to 10th	Day	44% 7% 9% 16% 17% 7%	1710
	11th to 20th	Day	38% 4 8% 17% 23% 10%	2150
	21st to end	Day	42% 6% 9% 17% 22% 4	3124
January	1st to 10th	Night	36% 7% 8% 16% 24% 8%	4109
	11th to 20th	Night	33% 6% 8% 21% 24% 9%	4120
	21st to end	Night	45% 5% 5% 12% 25% 8%	4532
February	1st to 10th	Night	40% 4 9% 17% 20% 9%	2304
	11th to 20th	Night	42% 4 6% 16% 22% 9%	2219
	21st to end	Night	40% 6% 9% 15% 19% 12%	1884
March	1st to 10th	Night	47% 8% 11% 13% 14% 8%	3480
	11th to 20th	Night	29% 6% 10% 14% 28% 13%	3480
	21st to end	Night	42% 6% 7% 17% 17% 11%	3817
April	1st to 10th	Night	33% 6% 10% 20% 22% 9%	2090
	11th to 20th	Night	31% 5% 7% 23% 22% 12%	1949
	21st to end	Night	28% 8% 11% 25% 22% 7%	1710
May	1st to 10th	Night	28% 7% 15% 23% 20% 6%	1710
	11th to 20th	Night	35% 11% 15% 20% 16% 2	1620
	21st to end	Night	36% 11% 12% 21% 17% 3	1745
June	1st to 10th	Night	38% 12% 19% 17% 12% 1	1620
	11th to 20th	Night	30% 12% 20% 25% 12% 2	1620
	21st to end	Night	33% 15% 20% 18% 11% 4	1620
July	1st to 10th	Night	38% 16% 20% 14% 8% 4	1575
	11th to 20th	Night	37% 16% 21% 18% 6% 2	1566
	21st to end	Night	33% 15% 26% 18% 6% 1	1672
August	1st to 10th	Night	41% 15% 19% 20% 5%	1600
	11th to 20th	Night	37% 15% 19% 18% 9% 2	1598
	21st to end	Night	42% 13% 19% 15% 9% 2	2040
September	1st to 10th	Night	36% 13% 16% 16% 15% 4	1980
	11th to 20th	Night	40% 9% 13% 15% 18% 5%	1980
	21st to end	Night	36% 7% 11% 17% 22% 6%	1980
October	1st to 10th	Night	31% 7% 10% 18% 27% 7%	1980
	11th to 20th	Night	30% 5% 9% 20% 26% 10%	2160
	21st to end	Night	29% 4 7% 17% 29% 14%	2376
November	1st to 10th	Night	31% 5% 7% 16% 27% 14%	2249
	11th to 20th	Night	33% 5% 7% 17% 24% 14%	2470
	21st to end	Night	35% 5% 8% 17% 25% 9%	2470
December	1st to 10th	Night	39% 7% 9% 19% 20% 7%	2470
	11th to 20th	Night	36% 4 8% 16% 26% 9%	3044
	21st to end	Night	46% 6% 7% 20% 18% 3	4532

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	23% 22% 39% 13% 3	270
	11th to 20th	Day	23% 21% 35% 16% 5%	270
	21st to end	Day	25% 26% 36% 9% 4	297
February	1st to 10th	Day	22% 21% 37% 15% 5%	270
	11th to 20th	Day	35% 19% 31% 13% 1	270
	21st to end	Day	29% 23% 36% 8% 4	225
March	1st to 10th	Day	22% 15% 33% 24% 6%	418
	11th to 20th	Day	21% 16% 37% 18% 7%	460
	21st to end	Day	20% 17% 36% 19% 7% 1	506
April	1st to 10th	Day	19% 15% 32% 23% 10% 1	460
	11th to 20th	Day	14% 15% 31% 23% 14% 2	452
	21st to end	Day	13% 9% 29% 27% 18% 3	460
May	1st to 10th	Day	13% 12% 33% 25% 12% 6%	463
	11th to 20th	Day	14% 4 24% 30% 19% 10%	456
	21st to end	Day	14% 7% 14% 30% 24% 12%	485
June	1st to 10th	Day	10% 2 17% 31% 28% 11%	450
	11th to 20th	Day	8% 6% 15% 26% 26% 19%	450
	21st to end	Day	7% 2 18% 33% 27% 14%	450
July	1st to 10th	Day	10% 2 9% 23% 34% 22%	445
	11th to 20th	Day	8% 2 10% 23% 36% 20%	444
	21st to end	Day	6% 1 9% 30% 36% 18%	488
August	1st to 10th	Day	14% 2 16% 26% 26% 17%	446
	11th to 20th	Day	10% 1 11% 28% 31% 18%	439
	21st to end	Day	13% 2 13% 26% 30% 16%	495
September	1st to 10th	Day	11% 4 11% 28% 31% 15%	450
	11th to 20th	Day	15% 2 13% 28% 31% 10%	450
	21st to end	Day	18% 4 14% 29% 26% 8%	450
October	1st to 10th	Day	18% 5% 24% 26% 18% 8%	450
	11th to 20th	Day	13% 9% 24% 26% 20% 8%	450
	21st to end	Day	17% 9% 26% 26% 17% 5%	495
November	1st to 10th	Day	17% 8% 28% 26% 17% 3	422
	11th to 20th	Day	19% 16% 36% 24% 5% 1	270
	21st to end	Day	15% 15% 31% 24% 14% 1	270
December	1st to 10th	Day	26% 16% 34% 17% 7%	270
	11th to 20th	Day	27% 13% 38% 16% 5% 1	270
	21st to end	Day	28% 17% 33% 14% 5% 2	297
January	1st to 10th	Night	21% 19% 33% 22% 6%	760
	11th to 20th	Night	20% 16% 31% 26% 8%	760
	21st to end	Night	20% 17% 35% 24% 4	836
February	1st to 10th	Night	18% 14% 31% 31% 5%	760
	11th to 20th	Night	23% 16% 33% 25% 3	743
	21st to end	Night	19% 17% 37% 24% 3	628
March	1st to 10th	Night	16% 15% 33% 31% 5%	760
	11th to 20th	Night	17% 14% 33% 27% 9% 1	760
	21st to end	Night	15% 16% 34% 26% 8%	836
April	1st to 10th	Night	14% 15% 33% 27% 11%	760
	11th to 20th	Night	15% 15% 26% 29% 14% 1	687
	21st to end	Night	9% 9% 29% 38% 15% 1	570
May	1st to 10th	Night	8% 9% 27% 38% 17% 1	570
	11th to 20th	Night	10% 3 23% 37% 22% 4	540
	21st to end	Night	12% 3 13% 33% 34% 5%	584
June	1st to 10th	Night	10% 2 14% 40% 30% 4	540
	11th to 20th	Night	7% 2 15% 33% 31% 11%	540
	21st to end	Night	9% 2 12% 38% 32% 7%	540
July	1st to 10th	Night	10% 1 8% 32% 39% 10%	525
	11th to 20th	Night	7% 1 8% 30% 46% 9%	522
	21st to end	Night	7% 2 8% 32% 45% 7%	591
August	1st to 10th	Night	9% 1 7% 35% 39% 9%	537
	11th to 20th	Night	14% 1 7% 31% 40% 7%	534
	21st to end	Night	11% 2 11% 29% 38% 8%	656
September	1st to 10th	Night	10% 2 10% 33% 36% 9%	720
	11th to 20th	Night	16% 3 11% 27% 38% 4	720
	21st to end	Night	16% 3 14% 31% 33% 3	720
October	1st to 10th	Night	14% 4 19% 32% 25% 6%	720
	11th to 20th	Night	14% 5% 23% 32% 23% 4	720
	21st to end	Night	13% 9% 24% 30% 23% 2	792
November	1st to 10th	Night	14% 8% 23% 33% 20% 3	740
	11th to 20th	Night	16% 11% 29% 30% 13% 2	760
	21st to end	Night	16% 10% 28% 30% 15% 1	760
December	1st to 10th	Night	18% 15% 25% 32% 9% 1	760
	11th to 20th	Night	20% 12% 28% 29% 12% 1	760
	21st to end	Night	25% 15% 25% 28% 7%	836

Page generated at 2024-05-10 12:38:57. Version ac07

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