Greater Napanee
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greater Napanee clear sky chart from 2005-11-06 to 2024-08-15.

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% 9% 3 7% 5% 4 4 4 5% 7% 35%	95721
	Night	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	92990
Transparency	Day	47% 8% 13% 21% 10% 1	95440
	Night	49% 8% 12% 19% 10% 1	92825
Seeing	Day	20% 13% 31% 23% 11% 3	14199
	Night	21% 11% 30% 26% 10% 1	23379

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	15% 16% 4 9% 5% 4 3 3 4 5% 29%	2517
	11th to 20th	Day	13% 17% 7% 14% 7% 6% 5% 4 4 4 18%	2520
	21st to end	Day	17% 20% 7% 11% 6% 5% 4 3 4 4 18%	3069
February	1st to 10th	Day	15% 15% 4 11% 8% 5% 5% 3 5% 6% 23%	1710
	11th to 20th	Day	14% 13% 5% 11% 6% 6% 5% 3 4 5% 28%	1663
	21st to end	Day	20% 13% 5% 8% 6% 5% 6% 3 4 5% 26%	1540
March	1st to 10th	Day	21% 12% 3 9% 5% 4 3 2 4 5% 31%	3243
	11th to 20th	Day	11% 15% 4 9% 6% 5% 5% 4 5% 4 32%	3480
	21st to end	Day	15% 9% 3 6% 5% 3 4 3 4 6% 43%	3937
April	1st to 10th	Day	20% 12% 2 7% 5% 4 4 3 4 5% 33%	2280
	11th to 20th	Day	20% 9% 2 6% 4 4 3 3 5% 5% 39%	2254
	21st to end	Day	20% 9% 3 8% 5% 4 4 4 5% 6% 32%	2399
May	1st to 10th	Day	19% 9% 3 8% 5% 5% 4 4 5% 7% 32%	4357
	11th to 20th	Day	15% 10% 3 7% 5% 4 5% 3 5% 8% 35%	4398
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 4 6% 8% 43%	4837
June	1st to 10th	Day	18% 6% 2 7% 6% 5% 5% 4 6% 8% 34%	2660
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 7% 9% 39%	2660
	21st to end	Day	15% 8% 2 6% 4 4 4 4 6% 8% 38%	2660
July	1st to 10th	Day	10% 5% 3 6% 5% 5% 4 4 6% 10% 42%	4440
	11th to 20th	Day	11% 5% 2 5% 4 3 5% 4 7% 9% 45%	4440
	21st to end	Day	8% 5% 2 6% 5% 6% 5% 5% 8% 9% 41%	4814
August	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 5% 7% 8% 42%	2482
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 5% 8% 9% 41%	2357
	21st to end	Day	12% 6% 2 5% 4 4 4 4 7% 8% 43%	2378
September	1st to 10th	Day	12% 6% 2 5% 4 5% 5% 4 5% 8% 44%	2160
	11th to 20th	Day	11% 6% 2 5% 4 3 4 3 5% 7% 51%	2160
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 9% 39%	1900
October	1st to 10th	Day	20% 7% 3 6% 4 4 4 4 5% 7% 36%	1800
	11th to 20th	Day	21% 7% 3 7% 5% 4 6% 4 5% 7% 32%	1800
	21st to end	Day	26% 10% 3 6% 5% 5% 4 4 5% 6% 26%	1913
November	1st to 10th	Day	16% 9% 2 7% 5% 5% 5% 4 6% 6% 35%	1655
	11th to 20th	Day	15% 11% 3 7% 6% 5% 5% 3 6% 7% 31%	1520
	21st to end	Day	21% 12% 4 8% 6% 4 4 4 5% 6% 25%	1520
December	1st to 10th	Day	21% 15% 4 9% 6% 5% 5% 4 5% 6% 22%	1520
	11th to 20th	Day	19% 15% 5% 8% 6% 4 4 4 4 5% 26%	1906
	21st to end	Day	30% 14% 4 9% 5% 4 3 2 4 4 21%	2772
January	1st to 10th	Night	19% 14% 5% 10% 6% 5% 5% 3 5% 5% 23%	4429
	11th to 20th	Night	15% 12% 5% 14% 7% 6% 6% 4 5% 5% 19%	4440
	21st to end	Night	21% 15% 6% 10% 5% 5% 5% 3 4 5% 21%	4584
February	1st to 10th	Night	16% 14% 4 10% 6% 5% 6% 4 5% 5% 25%	2470
	11th to 20th	Night	15% 13% 4 10% 6% 4 4 3 6% 6% 29%	2403
	21st to end	Night	18% 10% 3 9% 5% 5% 4 4 6% 7% 30%	1913
March	1st to 10th	Night	19% 10% 3 8% 5% 5% 4 3 4 6% 32%	3582
	11th to 20th	Night	19% 13% 3 9% 5% 4 4 3 5% 6% 29%	3479
	21st to end	Night	16% 9% 3 5% 3 3 3 3 5% 7% 43%	3695
April	1st to 10th	Night	21% 8% 3 7% 4 4 4 3 5% 7% 34%	1900
	11th to 20th	Night	18% 9% 2 7% 5% 4 4 4 5% 5% 37%	1875
	21st to end	Night	19% 9% 3 7% 5% 5% 4 4 5% 6% 35%	1799
May	1st to 10th	Night	22% 9% 4 7% 4 4 4 3 5% 5% 33%	2581
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 6% 6% 38%	2495
	21st to end	Night	12% 7% 2 5% 4 4 5% 4 6% 7% 44%	2738
June	1st to 10th	Night	13% 7% 3 7% 5% 6% 5% 5% 6% 8% 36%	1520
	11th to 20th	Night	10% 6% 2 6% 5% 4 5% 4 6% 9% 43%	1520
	21st to end	Night	14% 7% 3 7% 5% 4 4 4 6% 6% 41%	1520
July	1st to 10th	Night	11% 4 3 7% 5% 5% 6% 4 8% 8% 41%	2520
	11th to 20th	Night	13% 7% 2 5% 3 3 3 4 6% 8% 46%	2520
	21st to end	Night	10% 5% 2 5% 4 4 4 3 7% 8% 48%	2739
August	1st to 10th	Night	9% 5% 3 6% 4 4 4 4 5% 9% 47%	1672
	11th to 20th	Night	9% 6% 2 6% 4 4 4 3 7% 9% 46%	1643
	21st to end	Night	9% 5% 2 7% 3 4 4 4 7% 9% 46%	1959
September	1st to 10th	Night	12% 6% 2 5% 4 4 3 3 6% 8% 46%	1800
	11th to 20th	Night	12% 4 2 5% 3 3 3 3 6% 7% 52%	1800
	21st to end	Night	17% 5% 2 5% 4 4 4 4 6% 7% 43%	2058
October	1st to 10th	Night	17% 7% 3 7% 5% 5% 5% 3 5% 5% 37%	2160
	11th to 20th	Night	21% 8% 3 7% 5% 5% 4 3 5% 6% 34%	2160
	21st to end	Night	23% 9% 3 8% 5% 4 4 4 5% 6% 30%	2443
November	1st to 10th	Night	18% 9% 2 6% 4 3 4 3 5% 7% 38%	2421
	11th to 20th	Night	19% 8% 3 6% 5% 4 5% 4 6% 7% 33%	2660
	21st to end	Night	22% 11% 3 6% 4 4 5% 3 6% 7% 28%	2660
December	1st to 10th	Night	21% 15% 4 8% 5% 4 4 3 5% 7% 24%	2660
	11th to 20th	Night	19% 15% 4 8% 5% 4 4 4 4 4 29%	3288
	21st to end	Night	31% 13% 3 9% 4 4 4 3 4 5% 18%	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	55% 12% 13% 13% 6% 2	2518
	11th to 20th	Day	66% 11% 11% 7% 5%	2520
	21st to end	Day	67% 9% 8% 10% 5% 1	3069
February	1st to 10th	Day	61% 7% 11% 15% 5% 1	1710
	11th to 20th	Day	59% 6% 9% 16% 9% 1	1672
	21st to end	Day	58% 8% 11% 13% 10% 1	1540
March	1st to 10th	Day	54% 7% 12% 17% 9% 1	3246
	11th to 20th	Day	49% 10% 15% 15% 9% 1	3480
	21st to end	Day	40% 7% 9% 26% 15% 4	3937
April	1st to 10th	Day	54% 5% 8% 19% 12% 3	2280
	11th to 20th	Day	47% 6% 8% 22% 15% 2	2254
	21st to end	Day	51% 7% 10% 16% 13% 3	2399
May	1st to 10th	Day	48% 9% 11% 20% 10% 2	4371
	11th to 20th	Day	45% 11% 14% 20% 9% 1	4402
	21st to end	Day	35% 10% 14% 24% 14% 2	4837
June	1st to 10th	Day	46% 8% 13% 18% 13% 2	2660
	11th to 20th	Day	39% 8% 14% 25% 14% 2	2660
	21st to end	Day	41% 9% 15% 21% 12% 1	2660
July	1st to 10th	Day	37% 6% 14% 29% 13% 1	4370
	11th to 20th	Day	34% 7% 17% 33% 9%	4365
	21st to end	Day	36% 8% 17% 27% 11%	4661
August	1st to 10th	Day	37% 9% 18% 24% 11% 1	2468
	11th to 20th	Day	35% 10% 19% 25% 11% 1	2357
	21st to end	Day	37% 7% 15% 29% 12% 1	2378
September	1st to 10th	Day	36% 9% 16% 27% 12% 1	2160
	11th to 20th	Day	33% 7% 13% 30% 16% 1	2160
	21st to end	Day	42% 9% 13% 27% 9%	1900
October	1st to 10th	Day	47% 7% 13% 21% 12% 1	1800
	11th to 20th	Day	49% 8% 18% 18% 6% 1	1800
	21st to end	Day	58% 7% 10% 18% 7%	1913
November	1st to 10th	Day	46% 9% 15% 20% 9% 1	1655
	11th to 20th	Day	51% 8% 13% 17% 9% 1	1520
	21st to end	Day	57% 8% 13% 13% 8%	1520
December	1st to 10th	Day	63% 8% 14% 11% 5%	1520
	11th to 20th	Day	59% 9% 14% 13% 5%	1906
	21st to end	Day	66% 7% 9% 14% 4	2772
January	1st to 10th	Night	59% 10% 14% 13% 4	4429
	11th to 20th	Night	62% 12% 12% 9% 4 1	4440
	21st to end	Night	65% 10% 8% 12% 5% 1	4584
February	1st to 10th	Night	60% 7% 12% 15% 5% 1	2470
	11th to 20th	Night	53% 7% 11% 19% 9% 1	2405
	21st to end	Night	52% 8% 12% 18% 9% 1	1913
March	1st to 10th	Night	51% 7% 10% 22% 10% 1	3592
	11th to 20th	Night	54% 9% 12% 16% 9% 1	3480
	21st to end	Night	39% 7% 8% 24% 19% 3	3695
April	1st to 10th	Night	49% 6% 8% 21% 13% 2	1900
	11th to 20th	Night	48% 5% 10% 17% 18% 1	1875
	21st to end	Night	48% 7% 11% 15% 15% 3	1799
May	1st to 10th	Night	50% 8% 10% 17% 12% 2	2587
	11th to 20th	Night	44% 10% 13% 21% 9% 2	2496
	21st to end	Night	35% 10% 13% 20% 20% 2	2739
June	1st to 10th	Night	43% 9% 13% 21% 13% 1	1520
	11th to 20th	Night	35% 9% 13% 21% 20% 2	1520
	21st to end	Night	42% 8% 15% 21% 14% 1	1520
July	1st to 10th	Night	39% 7% 11% 23% 18% 1	2480
	11th to 20th	Night	36% 6% 13% 33% 13%	2472
	21st to end	Night	34% 7% 17% 29% 11% 2	2651
August	1st to 10th	Night	34% 8% 16% 29% 12% 1	1662
	11th to 20th	Night	33% 9% 17% 27% 13% 1	1643
	21st to end	Night	32% 10% 15% 29% 14% 1	1959
September	1st to 10th	Night	36% 7% 16% 27% 13% 1	1800
	11th to 20th	Night	30% 7% 14% 32% 15% 1	1800
	21st to end	Night	38% 9% 12% 29% 12% 1	2058
October	1st to 10th	Night	47% 8% 11% 20% 13% 1	2160
	11th to 20th	Night	50% 7% 14% 21% 7% 1	2160
	21st to end	Night	55% 8% 13% 14% 9% 1	2443
November	1st to 10th	Night	44% 7% 14% 22% 11% 1	2421
	11th to 20th	Night	49% 8% 13% 19% 10% 2	2660
	21st to end	Night	55% 9% 15% 16% 6%	2660
December	1st to 10th	Night	60% 8% 13% 15% 4	2660
	11th to 20th	Night	57% 7% 12% 17% 6% 1	3288
	21st to end	Night	67% 8% 11% 11% 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	26% 18% 32% 16% 8% 1	180
	11th to 20th	Day	28% 19% 33% 17% 3 1	180
	21st to end	Day	21% 19% 34% 20% 5%	283
February	1st to 10th	Day	29% 21% 35% 13% 2	270
	11th to 20th	Day	22% 24% 39% 14% 1	270
	21st to end	Day	34% 17% 34% 13% 3	352
March	1st to 10th	Day	23% 16% 35% 20% 5%	460
	11th to 20th	Day	22% 20% 33% 18% 5%	460
	21st to end	Day	31% 14% 31% 16% 7% 1	506
April	1st to 10th	Day	26% 20% 31% 16% 7%	460
	11th to 20th	Day	27% 17% 27% 16% 9% 3	452
	21st to end	Day	25% 12% 38% 15% 8% 1	460
May	1st to 10th	Day	22% 10% 32% 25% 9% 2	463
	11th to 20th	Day	15% 8% 36% 27% 11% 3	487
	21st to end	Day	15% 9% 32% 26% 16% 3	529
June	1st to 10th	Day	17% 10% 33% 28% 9% 2	490
	11th to 20th	Day	12% 11% 33% 28% 13% 3	490
	21st to end	Day	18% 9% 31% 27% 13% 2	490
July	1st to 10th	Day	11% 7% 25% 34% 19% 4	485
	11th to 20th	Day	13% 7% 27% 30% 18% 5%	484
	21st to end	Day	10% 6% 29% 38% 12% 4	532
August	1st to 10th	Day	14% 5% 26% 30% 20% 6%	486
	11th to 20th	Day	11% 5% 22% 34% 21% 7%	456
	21st to end	Day	12% 9% 27% 30% 15% 7%	495
September	1st to 10th	Day	12% 8% 31% 27% 14% 8%	450
	11th to 20th	Day	11% 8% 24% 26% 21% 11%	450
	21st to end	Day	16% 9% 28% 26% 16% 4	450
October	1st to 10th	Day	23% 12% 27% 18% 15% 5%	450
	11th to 20th	Day	22% 19% 30% 20% 8% 1	450
	21st to end	Day	30% 16% 28% 21% 5%	462
November	1st to 10th	Day	23% 17% 27% 23% 10% 1	349
	11th to 20th	Day	22% 23% 33% 14% 6% 2	180
	21st to end	Day	22% 19% 38% 14% 6% 1	180
December	1st to 10th	Day	26% 22% 33% 12% 7% 1	180
	11th to 20th	Day	26% 24% 34% 12% 4	180
	21st to end	Day	33% 17% 33% 13% 3	198
January	1st to 10th	Night	27% 16% 34% 19% 4	760
	11th to 20th	Night	29% 16% 29% 20% 6%	760
	21st to end	Night	22% 12% 36% 25% 6%	836
February	1st to 10th	Night	23% 16% 37% 21% 3	760
	11th to 20th	Night	22% 15% 38% 21% 4	743
	21st to end	Night	23% 17% 34% 21% 4	628
March	1st to 10th	Night	21% 13% 36% 26% 4	760
	11th to 20th	Night	24% 14% 33% 23% 5% 1	760
	21st to end	Night	21% 11% 36% 23% 8% 1	836
April	1st to 10th	Night	24% 11% 36% 24% 5%	760
	11th to 20th	Night	21% 13% 35% 21% 8% 1	751
	21st to end	Night	23% 10% 30% 25% 11% 1	659
May	1st to 10th	Night	24% 7% 27% 29% 12% 1	421
	11th to 20th	Night	13% 7% 33% 36% 10% 1	374
	21st to end	Night	10% 6% 33% 34% 15% 2	411
June	1st to 10th	Night	15% 5% 30% 34% 16% 1	380
	11th to 20th	Night	11% 5% 29% 38% 16% 1	380
	21st to end	Night	17% 6% 25% 37% 15%	380
July	1st to 10th	Night	7% 5% 26% 39% 22% 1	370
	11th to 20th	Night	10% 5% 21% 38% 23% 2	368
	21st to end	Night	12% 2 23% 47% 16% 1	416
August	1st to 10th	Night	11% 3 21% 37% 25% 3	538
	11th to 20th	Night	12% 4 19% 34% 26% 4	549
	21st to end	Night	10% 4 26% 37% 20% 2	771
September	1st to 10th	Night	13% 6% 26% 32% 20% 3	720
	11th to 20th	Night	13% 4 22% 29% 25% 6%	720
	21st to end	Night	19% 7% 23% 28% 19% 3	720
October	1st to 10th	Night	20% 11% 29% 22% 17% 2	720
	11th to 20th	Night	24% 13% 29% 24% 9% 1	720
	21st to end	Night	27% 13% 30% 25% 5%	792
November	1st to 10th	Night	25% 10% 29% 25% 10% 1	740
	11th to 20th	Night	24% 16% 33% 19% 8% 1	760
	21st to end	Night	28% 15% 30% 20% 7%	760
December	1st to 10th	Night	29% 20% 29% 19% 4	760
	11th to 20th	Night	26% 16% 37% 18% 3	760
	21st to end	Night	33% 15% 33% 16% 3	836

Page generated at 2024-08-12 09:52:55. Version ac07

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