Canton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canton clear sky chart from 2005-11-06 to 2024-04-25.

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	17% 7% 3 5% 5% 3 4 5% 5% 7% 39%	83150
	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 41%	85936
Transparency	Day	44% 5% 11% 23% 15% 2	82855
	Night	44% 5% 11% 22% 15% 2	85765
Seeing	Day	24% 14% 31% 20% 9% 3	14225
	Night	22% 11% 32% 27% 8% 1	23413

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% 7% 2 4 4 3 4 5% 5% 6% 45%	2517
	11th to 20th	Day	16% 9% 3 8% 6% 3 5% 5% 4 6% 35%	2520
	21st to end	Day	21% 12% 4 6% 5% 3 4 4 4 5% 32%	2836
February	1st to 10th	Day	17% 7% 3 6% 6% 3 6% 5% 5% 6% 36%	1762
	11th to 20th	Day	13% 6% 3 6% 5% 3 5% 5% 6% 7% 41%	1848
	21st to end	Day	20% 9% 3 4 5% 4 4 4 4 6% 38%	1570
March	1st to 10th	Day	25% 10% 3 7% 5% 3 3 3 3 5% 34%	3116
	11th to 20th	Day	11% 6% 2 5% 5% 3 6% 6% 7% 8% 40%	3251
	21st to end	Day	20% 7% 3 6% 5% 3 3 4 5% 6% 38%	4166
April	1st to 10th	Day	18% 8% 3 5% 6% 3 4 5% 5% 6% 37%	2280
	11th to 20th	Day	17% 5% 2 5% 6% 3 4 4 6% 7% 40%	2254
	21st to end	Day	22% 5% 3 4 5% 3 4 4 5% 6% 39%	2316
May	1st to 10th	Day	24% 7% 3 5% 5% 2 4 4 6% 7% 33%	2340
	11th to 20th	Day	19% 5% 3 5% 4 3 5% 4 5% 7% 41%	2419
	21st to end	Day	15% 6% 2 5% 5% 3 4 4 6% 7% 42%	2725
June	1st to 10th	Day	17% 5% 3 5% 6% 3 5% 6% 7% 8% 35%	2520
	11th to 20th	Day	17% 5% 3 6% 5% 4 5% 5% 7% 9% 36%	2520
	21st to end	Day	14% 7% 3 5% 5% 3 5% 6% 6% 8% 38%	2520
July	1st to 10th	Day	12% 6% 3 6% 6% 3 6% 5% 6% 8% 40%	2520
	11th to 20th	Day	11% 4 3 5% 5% 4 6% 6% 7% 9% 40%	2520
	21st to end	Day	12% 5% 3 6% 6% 4 5% 6% 6% 8% 39%	2744
August	1st to 10th	Day	11% 5% 2 6% 6% 4 6% 6% 7% 8% 37%	2429
	11th to 20th	Day	12% 5% 2 5% 6% 4 5% 5% 6% 9% 40%	2151
	21st to end	Day	13% 5% 2 5% 6% 3 5% 4 6% 7% 43%	2376
September	1st to 10th	Day	13% 6% 2 6% 6% 3 5% 5% 5% 7% 42%	2160
	11th to 20th	Day	14% 5% 2 4 3 2 3 4 5% 6% 51%	2038
	21st to end	Day	18% 5% 2 5% 4 3 5% 4 4 7% 44%	1980
October	1st to 10th	Day	23% 6% 2 4 4 2 4 4 4 5% 40%	1947
	11th to 20th	Day	15% 5% 2 4 4 3 4 4 7% 8% 44%	1781
	21st to end	Day	23% 6% 2 4 5% 3 5% 5% 3 7% 38%	1782
November	1st to 10th	Day	14% 6% 2 5% 5% 3 4 3 4 5% 49%	1671
	11th to 20th	Day	20% 5% 2 3 3 2 4 4 4 7% 45%	1710
	21st to end	Day	18% 6% 3 5% 4 2 3 4 4 6% 43%	1663
December	1st to 10th	Day	18% 5% 4 7% 5% 3 6% 5% 4 6% 37%	1520
	11th to 20th	Day	23% 5% 2 4 3 2 3 4 4 6% 44%	1906
	21st to end	Day	18% 12% 4 7% 6% 4 4 5% 4 6% 31%	2772
January	1st to 10th	Night	17% 7% 2 4 4 2 3 3 5% 5% 46%	4429
	11th to 20th	Night	16% 8% 4 7% 5% 2 4 4 5% 5% 41%	4440
	21st to end	Night	23% 12% 4 6% 5% 3 3 3 4 5% 31%	4819
February	1st to 10th	Night	16% 9% 4 5% 5% 2 4 5% 5% 6% 40%	2416
	11th to 20th	Night	14% 8% 3 6% 6% 3 4 5% 5% 7% 40%	2218
	21st to end	Night	19% 7% 2 5% 6% 2 4 4 4 6% 41%	1884
March	1st to 10th	Night	25% 11% 2 5% 4 3 3 4 4 5% 34%	3724
	11th to 20th	Night	12% 7% 3 5% 5% 3 5% 4 5% 7% 42%	3690
	21st to end	Night	22% 8% 2 5% 4 2 4 4 5% 5% 39%	3466
April	1st to 10th	Night	18% 8% 3 5% 5% 4 5% 5% 5% 5% 38%	1900
	11th to 20th	Night	19% 6% 2 5% 5% 3 4 5% 4 6% 40%	1875
	21st to end	Night	21% 8% 2 5% 4 2 3 3 4 5% 42%	1742
May	1st to 10th	Night	22% 8% 3 7% 6% 3 4 4 4 7% 32%	1620
	11th to 20th	Night	18% 7% 3 5% 4 3 5% 5% 5% 7% 38%	1488
	21st to end	Night	18% 6% 2 4 4 3 4 4 6% 8% 41%	1550
June	1st to 10th	Night	18% 6% 2 5% 4 3 4 4 4 7% 42%	1440
	11th to 20th	Night	17% 6% 2 5% 5% 3 5% 5% 5% 9% 38%	1440
	21st to end	Night	14% 5% 2 5% 4 2 4 3 6% 9% 44%	1440
July	1st to 10th	Night	13% 4 3 5% 5% 4 4 5% 6% 10% 42%	1440
	11th to 20th	Night	14% 5% 2 5% 6% 3 4 5% 6% 11% 39%	1440
	21st to end	Night	11% 5% 2 5% 6% 4 4 5% 6% 10% 42%	1574
August	1st to 10th	Night	8% 6% 2 5% 5% 4 4 6% 6% 9% 45%	1490
	11th to 20th	Night	12% 5% 3 6% 6% 4 6% 5% 7% 7% 40%	1747
	21st to end	Night	15% 5% 2 4 5% 2 4 4 5% 8% 46%	1980
September	1st to 10th	Night	15% 5% 2 6% 5% 3 4 4 5% 6% 45%	1800
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 6% 53%	1921
	21st to end	Night	17% 5% 2 4 5% 2 4 5% 4 6% 46%	1980
October	1st to 10th	Night	21% 6% 3 5% 5% 3 3 3 5% 5% 42%	2010
	11th to 20th	Night	16% 5% 2 5% 4 3 4 4 5% 6% 46%	2178
	21st to end	Night	25% 5% 2 4 5% 2 4 4 5% 5% 39%	2574
November	1st to 10th	Night	14% 5% 3 5% 5% 3 3 4 5% 6% 48%	2407
	11th to 20th	Night	19% 6% 3 4 4 2 4 4 5% 5% 45%	2470
	21st to end	Night	16% 6% 2 4 4 3 5% 4 5% 6% 45%	2512
December	1st to 10th	Night	19% 7% 3 5% 5% 3 4 4 5% 6% 40%	2660
	11th to 20th	Night	20% 6% 2 4 4 2 4 5% 5% 6% 42%	3288
	21st to end	Night	22% 10% 3 6% 5% 3 4 3 4 5% 36%	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	39% 4 11% 33% 11% 2	2518
	11th to 20th	Day	49% 6% 10% 24% 10% 1	2520
	21st to end	Day	54% 5% 8% 21% 10% 1	2836
February	1st to 10th	Day	48% 6% 12% 20% 13% 2	1762
	11th to 20th	Day	43% 6% 9% 23% 16% 3	1857
	21st to end	Day	48% 4 10% 21% 14% 3	1570
March	1st to 10th	Day	55% 3 11% 18% 11% 2	3119
	11th to 20th	Day	36% 9% 12% 30% 12% 2	3251
	21st to end	Day	46% 4 6% 18% 21% 6%	4166
April	1st to 10th	Day	46% 5% 10% 20% 15% 4	2280
	11th to 20th	Day	43% 4 10% 22% 18% 3	2254
	21st to end	Day	45% 5% 9% 20% 17% 4	2316
May	1st to 10th	Day	50% 6% 8% 20% 14% 2	2340
	11th to 20th	Day	43% 5% 9% 22% 18% 3	2423
	21st to end	Day	41% 6% 15% 22% 14% 3	2725
June	1st to 10th	Day	45% 7% 11% 23% 12% 1	2520
	11th to 20th	Day	43% 6% 13% 23% 13% 2	2520
	21st to end	Day	42% 7% 12% 24% 15% 1	2520
July	1st to 10th	Day	42% 6% 12% 21% 17% 2	2450
	11th to 20th	Day	39% 6% 14% 25% 14% 2	2445
	21st to end	Day	40% 7% 13% 21% 17% 2	2591
August	1st to 10th	Day	41% 7% 13% 24% 14% 1	2415
	11th to 20th	Day	40% 6% 15% 24% 14% 1	2151
	21st to end	Day	39% 6% 11% 24% 19% 2	2376
September	1st to 10th	Day	41% 5% 10% 23% 18% 2	2160
	11th to 20th	Day	34% 4 10% 25% 24% 3	2038
	21st to end	Day	41% 4 9% 24% 20% 3	1980
October	1st to 10th	Day	46% 4 8% 23% 15% 3	1947
	11th to 20th	Day	37% 5% 13% 28% 15% 2	1781
	21st to end	Day	46% 5% 11% 20% 15% 3	1782
November	1st to 10th	Day	39% 4 11% 24% 19% 3	1671
	11th to 20th	Day	40% 4 10% 23% 20% 3	1710
	21st to end	Day	42% 4 12% 27% 12% 3	1663
December	1st to 10th	Day	48% 5% 13% 18% 15% 1	1520
	11th to 20th	Day	42% 4 16% 20% 16% 2	1906
	21st to end	Day	53% 6% 10% 20% 10% 1	2772
January	1st to 10th	Night	40% 4 12% 30% 11% 4	4429
	11th to 20th	Night	45% 5% 11% 24% 12% 4	4440
	21st to end	Night	55% 5% 9% 19% 11% 1	4819
February	1st to 10th	Night	46% 4 12% 23% 12% 2	2416
	11th to 20th	Night	44% 6% 9% 20% 18% 4	2220
	21st to end	Night	45% 4 9% 24% 13% 5%	1884
March	1st to 10th	Night	53% 5% 9% 19% 12% 2	3734
	11th to 20th	Night	39% 8% 14% 24% 14% 2	3691
	21st to end	Night	46% 5% 6% 13% 24% 5%	3466
April	1st to 10th	Night	46% 5% 9% 21% 15% 3	1900
	11th to 20th	Night	45% 6% 9% 19% 20% 1	1875
	21st to end	Night	45% 4 9% 21% 15% 5%	1742
May	1st to 10th	Night	52% 5% 9% 17% 14% 3	1620
	11th to 20th	Night	45% 5% 11% 19% 16% 4	1489
	21st to end	Night	41% 7% 16% 20% 13% 1	1551
June	1st to 10th	Night	43% 6% 11% 23% 15% 1	1440
	11th to 20th	Night	43% 6% 15% 25% 11% 1	1440
	21st to end	Night	37% 6% 15% 26% 15%	1440
July	1st to 10th	Night	38% 7% 14% 22% 17% 2	1400
	11th to 20th	Night	40% 7% 16% 27% 9% 1	1392
	21st to end	Night	37% 7% 15% 23% 15% 3	1486
August	1st to 10th	Night	34% 10% 16% 25% 14% 2	1480
	11th to 20th	Night	41% 7% 14% 25% 12% 1	1747
	21st to end	Night	37% 6% 12% 25% 20% 1	1980
September	1st to 10th	Night	41% 5% 10% 26% 17% 1	1800
	11th to 20th	Night	34% 5% 10% 23% 26% 2	1921
	21st to end	Night	38% 4 9% 24% 21% 2	1980
October	1st to 10th	Night	45% 5% 12% 21% 14% 3	2010
	11th to 20th	Night	38% 5% 13% 28% 15% 1	2178
	21st to end	Night	47% 5% 11% 21% 15% 1	2574
November	1st to 10th	Night	38% 5% 11% 21% 20% 4	2407
	11th to 20th	Night	42% 4 11% 22% 19% 3	2470
	21st to end	Night	41% 4 14% 28% 12% 1	2512
December	1st to 10th	Night	45% 5% 13% 22% 14% 1	2660
	11th to 20th	Night	43% 5% 14% 18% 17% 2	3288
	21st to end	Night	52% 4 9% 23% 11% 1	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% 16% 34% 17% 6%	180
	11th to 20th	Day	31% 22% 33% 11% 3	180
	21st to end	Day	22% 23% 34% 13% 6% 1	216
February	1st to 10th	Day	32% 18% 34% 14% 2	322
	11th to 20th	Day	30% 21% 35% 13% 2	456
	21st to end	Day	31% 15% 35% 14% 4	382
March	1st to 10th	Day	25% 20% 36% 17% 3	460
	11th to 20th	Day	27% 20% 34% 15% 3 1	460
	21st to end	Day	31% 19% 33% 10% 5% 2	506
April	1st to 10th	Day	30% 18% 31% 12% 7% 2	460
	11th to 20th	Day	29% 18% 31% 14% 6% 1	452
	21st to end	Day	34% 15% 32% 13% 5% 1	437
May	1st to 10th	Day	35% 17% 26% 13% 7% 1	423
	11th to 20th	Day	22% 16% 36% 19% 5% 1	447
	21st to end	Day	21% 14% 27% 24% 10% 3	485
June	1st to 10th	Day	19% 13% 30% 25% 10% 3	450
	11th to 20th	Day	20% 13% 34% 24% 8% 2	450
	21st to end	Day	18% 11% 30% 28% 10% 3	450
July	1st to 10th	Day	15% 7% 30% 28% 16% 4	445
	11th to 20th	Day	14% 5% 30% 32% 16% 4	444
	21st to end	Day	14% 9% 34% 29% 11% 3	488
August	1st to 10th	Day	13% 7% 31% 32% 12% 6%	446
	11th to 20th	Day	15% 5% 32% 26% 15% 8%	439
	21st to end	Day	15% 7% 30% 25% 16% 7%	495
September	1st to 10th	Day	18% 11% 22% 25% 16% 8%	450
	11th to 20th	Day	17% 10% 28% 24% 11% 10%	450
	21st to end	Day	20% 11% 30% 22% 10% 6%	450
October	1st to 10th	Day	30% 8% 25% 18% 13% 6%	450
	11th to 20th	Day	19% 15% 29% 25% 9% 2	440
	21st to end	Day	31% 13% 26% 21% 7% 1	396
November	1st to 10th	Day	21% 13% 29% 25% 10% 2	365
	11th to 20th	Day	29% 17% 27% 18% 7% 1	370
	21st to end	Day	28% 13% 30% 20% 8% 1	323
December	1st to 10th	Day	23% 19% 35% 16% 7% 1	180
	11th to 20th	Day	31% 21% 35% 9% 4	180
	21st to end	Day	29% 14% 38% 12% 7% 1	198
January	1st to 10th	Night	23% 14% 38% 22% 3	760
	11th to 20th	Night	27% 15% 33% 23% 3	760
	21st to end	Night	22% 16% 36% 23% 3	836
February	1st to 10th	Night	23% 15% 34% 26% 2	760
	11th to 20th	Night	22% 17% 40% 19% 1	743
	21st to end	Night	27% 13% 36% 21% 3	628
March	1st to 10th	Night	25% 17% 36% 20% 3	760
	11th to 20th	Night	22% 17% 37% 20% 4	760
	21st to end	Night	25% 16% 34% 20% 4	836
April	1st to 10th	Night	25% 15% 35% 20% 4	760
	11th to 20th	Night	25% 15% 35% 20% 6%	751
	21st to end	Night	26% 16% 33% 20% 4 1	632
May	1st to 10th	Night	29% 15% 30% 22% 5%	540
	11th to 20th	Night	23% 12% 39% 22% 4	427
	21st to end	Night	20% 8% 29% 35% 8% 1	389
June	1st to 10th	Night	22% 7% 30% 32% 10%	360
	11th to 20th	Night	20% 6% 30% 34% 10%	360
	21st to end	Night	18% 2 33% 36% 12%	360
July	1st to 10th	Night	14% 4 25% 38% 18% 1	350
	11th to 20th	Night	16% 3 22% 41% 16% 1	348
	21st to end	Night	13% 4 24% 44% 15%	394
August	1st to 10th	Night	11% 3 28% 43% 14% 1	416
	11th to 20th	Night	14% 5% 22% 39% 20% 1	683
	21st to end	Night	16% 4 23% 36% 19% 2	792
September	1st to 10th	Night	18% 5% 28% 33% 15% 2	720
	11th to 20th	Night	18% 4 25% 33% 16% 3	720
	21st to end	Night	21% 5% 26% 29% 16% 2	720
October	1st to 10th	Night	24% 7% 25% 29% 12% 3	720
	11th to 20th	Night	19% 10% 31% 30% 9% 1	720
	21st to end	Night	29% 10% 31% 23% 7%	792
November	1st to 10th	Night	19% 12% 31% 28% 10% 1	740
	11th to 20th	Night	24% 12% 33% 24% 6% 1	760
	21st to end	Night	24% 13% 31% 26% 5% 1	760
December	1st to 10th	Night	26% 13% 32% 23% 5% 1	760
	11th to 20th	Night	23% 14% 34% 25% 4	760
	21st to end	Night	28% 13% 32% 24% 2	836

Page generated at 2024-04-22 09:25:40. Version ac07

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