Luckie's Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Luckie's Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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	15% 5% 2 5% 5% 3 5% 5% 6% 7% 41%	78912
	Night	16% 5% 2 4 4 3 4 4 5% 7% 44%	80658
Transparency	Day	40% 7% 11% 18% 18% 5%	78635
	Night	39% 6% 11% 19% 20% 6%	80454
Seeing	Day	21% 8% 22% 23% 18% 9%	13980
	Night	19% 8% 20% 29% 19% 4	24144

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	19% 6% 2 4 5% 2 4 4 5% 6% 43%	2836
	11th to 20th	Day	17% 5% 2 4 4 2 3 4 3 3 52%	2840
	21st to end	Day	27% 6% 2 3 3 2 3 2 3 5% 44%	3127
February	1st to 10th	Day	19% 7% 2 5% 4 2 4 4 5% 6% 42%	1900
	11th to 20th	Day	22% 5% 2 4 4 2 4 4 5% 5% 43%	1848
	21st to end	Day	23% 6% 2 5% 4 3 3 5% 3 6% 40%	1570
March	1st to 10th	Day	17% 5% 2 4 4 2 4 4 4 6% 48%	1953
	11th to 20th	Day	20% 6% 3 5% 5% 2 5% 4 5% 6% 40%	1980
	21st to end	Day	18% 6% 3 5% 5% 3 5% 3 5% 7% 40%	2178
April	1st to 10th	Day	14% 4 3 4 4 4 5% 5% 6% 7% 44%	1981
	11th to 20th	Day	14% 5% 2 5% 6% 3 4 4 4 7% 46%	2149
	21st to end	Day	13% 3 2 4 4 2 5% 4 5% 8% 49%	2340
May	1st to 10th	Day	11% 5% 2 6% 5% 3 5% 4 5% 8% 46%	2340
	11th to 20th	Day	14% 5% 3 7% 6% 4 6% 6% 6% 7% 37%	2301
	21st to end	Day	13% 5% 2 5% 6% 4 6% 7% 6% 9% 37%	2531
June	1st to 10th	Day	12% 6% 3 6% 7% 4 7% 7% 8% 8% 33%	2340
	11th to 20th	Day	8% 4 2 5% 6% 5% 6% 7% 9% 11% 37%	2340
	21st to end	Day	8% 4 2 5% 7% 5% 6% 7% 8% 11% 36%	2340
July	1st to 10th	Day	10% 6% 4 7% 8% 5% 8% 7% 8% 9% 27%	2340
	11th to 20th	Day	10% 6% 3 6% 8% 6% 9% 8% 9% 10% 25%	2340
	21st to end	Day	7% 5% 3 7% 8% 6% 9% 7% 9% 10% 29%	2547
August	1st to 10th	Day	11% 6% 3 6% 7% 5% 7% 8% 8% 9% 30%	2327
	11th to 20th	Day	12% 6% 2 6% 7% 5% 6% 7% 7% 11% 30%	2249
	21st to end	Day	14% 6% 3 7% 6% 5% 8% 6% 7% 9% 31%	2354
September	1st to 10th	Day	12% 5% 2 7% 7% 3 6% 7% 7% 9% 37%	1980
	11th to 20th	Day	16% 6% 2 5% 6% 3 5% 5% 6% 7% 39%	1980
	21st to end	Day	15% 5% 2 5% 4 3 4 4 6% 6% 46%	1980
October	1st to 10th	Day	15% 5% 2 3 4 2 3 3 4 6% 53%	1980
	11th to 20th	Day	14% 5% 2 3 3 1 3 3 4 6% 55%	1836
	21st to end	Day	15% 5% 1 4 3 2 3 3 3 4 57%	1980
November	1st to 10th	Day	13% 4 2 3 3 2 2 4 4 5% 58%	1718
	11th to 20th	Day	17% 3 2 3 3 2 4 3 4 6% 53%	1710
	21st to end	Day	17% 4 2 3 4 2 4 4 5% 6% 49%	1710
December	1st to 10th	Day	24% 6% 2 4 4 2 4 4 5% 5% 39%	1710
	11th to 20th	Day	18% 5% 2 4 4 3 4 3 4 5% 48%	2153
	21st to end	Day	24% 6% 2 4 3 2 3 3 5% 7% 41%	3124
January	1st to 10th	Night	19% 6% 2 4 4 3 4 4 4 5% 46%	4109
	11th to 20th	Night	15% 7% 3 5% 5% 2 3 4 5% 5% 48%	4120
	21st to end	Night	27% 7% 2 4 3 2 3 3 3 4 42%	4527
February	1st to 10th	Night	17% 5% 2 4 4 3 4 4 5% 6% 47%	2280
	11th to 20th	Night	22% 6% 3 4 4 3 3 3 4 5% 43%	2218
	21st to end	Night	21% 6% 2 5% 5% 2 4 5% 5% 6% 39%	1884
March	1st to 10th	Night	18% 5% 2 4 3 2 4 3 5% 5% 49%	2166
	11th to 20th	Night	17% 5% 3 4 4 3 5% 5% 6% 6% 43%	1980
	21st to end	Night	17% 6% 3 5% 5% 2 4 4 4 5% 44%	2178
April	1st to 10th	Night	14% 4 1 4 4 2 4 5% 6% 6% 50%	1980
	11th to 20th	Night	14% 5% 2 4 4 2 4 4 4 6% 49%	1770
	21st to end	Night	11% 4 2 5% 4 2 4 4 5% 7% 52%	1620
May	1st to 10th	Night	12% 4 2 4 5% 4 3 4 6% 8% 48%	1620
	11th to 20th	Night	13% 6% 3 5% 6% 3 4 5% 6% 8% 42%	1592
	21st to end	Night	12% 6% 3 6% 5% 3 4 6% 7% 7% 41%	1744
June	1st to 10th	Night	11% 6% 2 5% 7% 5% 7% 6% 8% 9% 35%	1620
	11th to 20th	Night	8% 5% 2 5% 4 3 5% 6% 7% 12% 43%	1620
	21st to end	Night	8% 3 2 5% 5% 4 6% 6% 8% 10% 44%	1620
July	1st to 10th	Night	11% 6% 4 6% 6% 4 7% 6% 8% 11% 32%	1620
	11th to 20th	Night	9% 4 3 6% 7% 5% 6% 7% 8% 11% 33%	1620
	21st to end	Night	7% 5% 3 6% 7% 4 6% 7% 9% 11% 34%	1771
August	1st to 10th	Night	12% 5% 3 5% 5% 4 5% 7% 8% 11% 34%	1611
	11th to 20th	Night	14% 6% 2 5% 6% 3 6% 5% 7% 10% 36%	1647
	21st to end	Night	14% 6% 4 5% 6% 3 5% 6% 6% 9% 35%	1982
September	1st to 10th	Night	12% 5% 2 5% 5% 3 5% 5% 6% 8% 42%	1980
	11th to 20th	Night	17% 6% 2 4 5% 3 4 5% 5% 8% 41%	1980
	21st to end	Night	13% 6% 2 5% 5% 3 4 4 5% 6% 49%	1980
October	1st to 10th	Night	15% 5% 2 4 4 3 2 3 4 4 54%	1980
	11th to 20th	Night	14% 4 2 4 4 2 3 4 4 5% 53%	2123
	21st to end	Night	14% 4 1 3 3 2 3 4 4 5% 57%	2376
November	1st to 10th	Night	15% 4 2 4 2 2 2 3 3 5% 58%	2356
	11th to 20th	Night	16% 4 2 4 3 2 3 3 4 5% 53%	2470
	21st to end	Night	19% 4 2 4 4 2 4 4 5% 6% 46%	2470
December	1st to 10th	Night	22% 6% 2 5% 4 2 3 3 4 5% 42%	2470
	11th to 20th	Night	18% 5% 2 3 3 1 3 4 3 6% 51%	3042
	21st to end	Night	24% 6% 2 4 3 3 4 5% 5% 8% 35%	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	41% 5% 7% 18% 21% 8%	2837
	11th to 20th	Day	37% 4 6% 17% 27% 9%	2840
	21st to end	Day	45% 4 5% 17% 22% 8%	3127
February	1st to 10th	Day	43% 4 7% 19% 20% 6%	1900
	11th to 20th	Day	43% 5% 7% 18% 21% 7%	1858
	21st to end	Day	46% 5% 7% 14% 19% 9%	1570
March	1st to 10th	Day	38% 5% 8% 17% 22% 10%	1953
	11th to 20th	Day	45% 6% 8% 16% 18% 8%	1980
	21st to end	Day	44% 6% 10% 20% 17% 3	2178
April	1st to 10th	Day	36% 7% 10% 20% 21% 6%	1981
	11th to 20th	Day	39% 5% 8% 17% 23% 8%	2149
	21st to end	Day	33% 6% 10% 28% 19% 4	2340
May	1st to 10th	Day	36% 7% 12% 19% 21% 4	2340
	11th to 20th	Day	43% 10% 13% 18% 14% 2	2305
	21st to end	Day	40% 11% 12% 21% 15% 2	2531
June	1st to 10th	Day	43% 11% 16% 20% 9% 2	2340
	11th to 20th	Day	36% 11% 19% 20% 12% 1	2340
	21st to end	Day	38% 12% 17% 18% 12% 3	2340
July	1st to 10th	Day	46% 13% 15% 17% 7% 2	2275
	11th to 20th	Day	46% 13% 18% 12% 6% 3	2271
	21st to end	Day	42% 15% 17% 18% 8%	2405
August	1st to 10th	Day	44% 13% 16% 20% 6% 1	2314
	11th to 20th	Day	45% 11% 17% 17% 7% 2	2249
	21st to end	Day	46% 11% 14% 17% 9% 2	2354
September	1st to 10th	Day	41% 10% 14% 17% 16% 3	1980
	11th to 20th	Day	42% 9% 11% 16% 20% 2	1980
	21st to end	Day	38% 6% 10% 18% 21% 7%	1980
October	1st to 10th	Day	33% 5% 9% 18% 27% 8%	1980
	11th to 20th	Day	31% 5% 9% 22% 23% 10%	1836
	21st to end	Day	32% 3 5% 19% 28% 12%	1980
November	1st to 10th	Day	31% 4 7% 16% 31% 12%	1718
	11th to 20th	Day	34% 3 7% 19% 27% 10%	1710
	21st to end	Day	36% 5% 6% 18% 27% 7%	1710
December	1st to 10th	Day	47% 5% 5% 18% 18% 7%	1710
	11th to 20th	Day	38% 4 6% 16% 25% 10%	2150
	21st to end	Day	42% 4 9% 19% 23% 3	3124
January	1st to 10th	Night	39% 5% 8% 14% 27% 7%	4109
	11th to 20th	Night	38% 5% 7% 17% 23% 11%	4120
	21st to end	Night	47% 3 5% 13% 24% 8%	4527
February	1st to 10th	Night	38% 5% 8% 20% 22% 7%	2280
	11th to 20th	Night	45% 4 5% 17% 22% 7%	2219
	21st to end	Night	45% 5% 8% 15% 19% 7%	1884
March	1st to 10th	Night	38% 4 9% 17% 22% 11%	2166
	11th to 20th	Night	40% 7% 11% 16% 20% 6%	1980
	21st to end	Night	41% 5% 9% 21% 20% 3	2178
April	1st to 10th	Night	33% 5% 11% 20% 24% 7%	1980
	11th to 20th	Night	35% 4 7% 22% 21% 11%	1770
	21st to end	Night	32% 6% 10% 28% 21% 4	1620
May	1st to 10th	Night	34% 7% 13% 22% 21% 3	1620
	11th to 20th	Night	40% 8% 15% 21% 13% 1	1593
	21st to end	Night	40% 8% 13% 25% 12% 2	1745
June	1st to 10th	Night	41% 11% 16% 20% 10% 2	1620
	11th to 20th	Night	31% 11% 21% 24% 12% 1	1620
	21st to end	Night	33% 11% 19% 21% 13% 3	1620
July	1st to 10th	Night	42% 12% 19% 17% 9% 1	1575
	11th to 20th	Night	40% 14% 22% 15% 7% 2	1566
	21st to end	Night	38% 14% 21% 19% 6% 2	1672
August	1st to 10th	Night	39% 13% 22% 19% 6% 1	1600
	11th to 20th	Night	41% 11% 16% 18% 12% 1	1647
	21st to end	Night	44% 10% 17% 18% 9% 3	1982
September	1st to 10th	Night	38% 10% 14% 18% 15% 4	1980
	11th to 20th	Night	40% 8% 13% 18% 18% 2	1980
	21st to end	Night	37% 6% 11% 20% 20% 7%	1980
October	1st to 10th	Night	33% 5% 10% 18% 27% 6%	1980
	11th to 20th	Night	33% 5% 8% 21% 22% 10%	2123
	21st to end	Night	30% 4 6% 20% 27% 12%	2376
November	1st to 10th	Night	31% 4 8% 20% 26% 12%	2356
	11th to 20th	Night	34% 3 6% 17% 27% 12%	2470
	21st to end	Night	38% 4 7% 19% 24% 7%	2470
December	1st to 10th	Night	45% 5% 6% 18% 19% 6%	2470
	11th to 20th	Night	35% 4 8% 17% 28% 8%	3044
	21st to end	Night	45% 5% 9% 19% 19% 4	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	30% 19% 38% 11% 2	270
	11th to 20th	Day	33% 18% 29% 15% 5% 1	270
	21st to end	Day	32% 20% 34% 11% 3 1	297
February	1st to 10th	Day	30% 16% 36% 15% 3	270
	11th to 20th	Day	43% 18% 30% 9%	270
	21st to end	Day	40% 15% 33% 11% 1	225
March	1st to 10th	Day	25% 15% 30% 21% 9%	344
	11th to 20th	Day	27% 16% 31% 20% 5% 1	420
	21st to end	Day	29% 14% 29% 20% 7% 1	462
April	1st to 10th	Day	22% 13% 28% 24% 12% 2	420
	11th to 20th	Day	18% 16% 31% 21% 10% 3	412
	21st to end	Day	20% 10% 26% 25% 15% 5%	420
May	1st to 10th	Day	16% 13% 30% 22% 12% 7%	423
	11th to 20th	Day	19% 5% 17% 29% 19% 11%	447
	21st to end	Day	18% 6% 16% 25% 22% 13%	485
June	1st to 10th	Day	16% 4 16% 28% 23% 13%	450
	11th to 20th	Day	12% 3 15% 26% 25% 20%	450
	21st to end	Day	12% 3 19% 29% 25% 13%	450
July	1st to 10th	Day	13% 1 10% 22% 29% 24%	445
	11th to 20th	Day	11% 1 10% 23% 33% 22%	444
	21st to end	Day	6% 1 7% 26% 35% 25%	488
August	1st to 10th	Day	16% 2 11% 25% 24% 21%	446
	11th to 20th	Day	16% 1 6% 26% 33% 18%	439
	21st to end	Day	19% 2 8% 23% 30% 18%	495
September	1st to 10th	Day	14% 3 13% 25% 32% 14%	450
	11th to 20th	Day	20% 2 11% 23% 33% 11%	450
	21st to end	Day	18% 4 16% 29% 24% 9%	450
October	1st to 10th	Day	21% 4 20% 28% 19% 8%	450
	11th to 20th	Day	18% 7% 22% 31% 17% 5%	450
	21st to end	Day	21% 7% 24% 31% 15% 3	495
November	1st to 10th	Day	22% 6% 29% 25% 14% 3	316
	11th to 20th	Day	24% 17% 32% 21% 5%	270
	21st to end	Day	19% 13% 36% 22% 7% 2	270
December	1st to 10th	Day	33% 16% 29% 18% 4	270
	11th to 20th	Day	26% 14% 35% 18% 5% 1	270
	21st to end	Day	38% 12% 27% 16% 6% 1	297
January	1st to 10th	Night	25% 16% 29% 23% 6%	760
	11th to 20th	Night	23% 16% 28% 26% 7%	760
	21st to end	Night	24% 15% 33% 24% 3	836
February	1st to 10th	Night	21% 13% 31% 30% 6%	760
	11th to 20th	Night	26% 18% 29% 25% 2	743
	21st to end	Night	26% 14% 32% 25% 3	628
March	1st to 10th	Night	22% 13% 30% 31% 4	751
	11th to 20th	Night	20% 13% 28% 29% 8% 1	720
	21st to end	Night	21% 13% 26% 30% 9%	792
April	1st to 10th	Night	18% 13% 28% 29% 11%	720
	11th to 20th	Night	18% 12% 22% 32% 15% 1	546
	21st to end	Night	14% 7% 22% 34% 21% 2	540
May	1st to 10th	Night	15% 8% 21% 33% 21% 1	540
	11th to 20th	Night	18% 3 17% 31% 26% 5%	531
	21st to end	Night	16% 2 11% 30% 35% 7%	584
June	1st to 10th	Night	13% 2 12% 33% 35% 6%	540
	11th to 20th	Night	10% 1 10% 32% 31% 15%	540
	21st to end	Night	9% 1 10% 36% 34% 10%	540
July	1st to 10th	Night	13% 2 6% 23% 43% 12%	525
	11th to 20th	Night	11% 1 5% 23% 44% 16%	522
	21st to end	Night	8% 2 6% 25% 46% 14%	591
August	1st to 10th	Night	15% 2 3 23% 39% 16%	537
	11th to 20th	Night	16% 1 6% 26% 40% 11%	534
	21st to end	Night	16% 1 5% 26% 41% 11%	596
September	1st to 10th	Night	14% 1 9% 29% 36% 11%	720
	11th to 20th	Night	20% 2 11% 27% 35% 6%	720
	21st to end	Night	16% 4 13% 35% 28% 3	720
October	1st to 10th	Night	18% 4 19% 29% 23% 7%	720
	11th to 20th	Night	16% 8% 22% 33% 19% 3	720
	21st to end	Night	17% 8% 21% 33% 18% 3	792
November	1st to 10th	Night	18% 7% 21% 33% 19% 3	740
	11th to 20th	Night	19% 10% 25% 32% 13% 1	760
	21st to end	Night	21% 10% 25% 31% 12% 1	760
December	1st to 10th	Night	27% 12% 22% 30% 8% 1	760
	11th to 20th	Night	22% 11% 26% 31% 10%	760
	21st to end	Night	30% 10% 25% 29% 5%	836

Page generated at 2024-03-05 07:24:03. Version ac07

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