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 2025-01-07.

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	16% 9% 3 7% 5% 4 4 4 5% 7% 35%	105167
	Night	17% 10% 3 8% 5% 4 4 4 5% 6% 34%	103864
Transparency	Day	46% 8% 13% 22% 10% 1	108715
	Night	48% 7% 12% 20% 11% 1	108405
Seeing	Day	20% 13% 31% 23% 11% 3	14649
	Night	21% 11% 30% 26% 11% 1	23950

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% 5% 3 3 4 6% 29%	2565
	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	17% 7% 2 6% 4 4 4 4 6% 8% 39%	4142
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 7% 10% 39%	4044
	21st to end	Day	13% 5% 2 5% 4 4 5% 4 7% 9% 43%	4182
September	1st to 10th	Day	11% 6% 2 5% 4 5% 4 4 5% 8% 45%	2280
	11th to 20th	Day	10% 6% 2 5% 4 3 4 3 5% 7% 52%	2280
	21st to end	Day	16% 7% 2 6% 4 4 4 4 6% 8% 39%	2004
October	1st to 10th	Day	19% 7% 3 6% 4 4 4 4 5% 7% 37%	1900
	11th to 20th	Day	20% 7% 2 7% 4 5% 6% 4 5% 7% 33%	1900
	21st to end	Day	25% 10% 3 7% 5% 5% 4 4 5% 6% 27%	2019
November	1st to 10th	Day	15% 9% 2 7% 4 5% 5% 4 6% 7% 35%	1744
	11th to 20th	Day	15% 11% 3 7% 6% 5% 5% 4 6% 7% 32%	1600
	21st to end	Day	21% 12% 4 8% 6% 4 4 5% 5% 6% 25%	1600
December	1st to 10th	Day	20% 13% 4 10% 6% 6% 5% 4 5% 6% 22%	2600
	11th to 20th	Day	19% 16% 5% 10% 5% 4 4 3 3 4 26%	2986
	21st to end	Day	26% 12% 4 8% 5% 5% 4 3 5% 5% 25%	3960
January	1st to 10th	Night	19% 13% 5% 10% 6% 5% 5% 4 5% 5% 23%	4514
	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	11% 6% 2 7% 4 4 4 4 5% 8% 45%	2783
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 6% 8% 46%	2785
	21st to end	Night	8% 4 2 6% 4 4 5% 4 8% 10% 45%	3441
September	1st to 10th	Night	12% 6% 2 5% 4 4 3 3 5% 8% 47%	1900
	11th to 20th	Night	12% 4 2 5% 3 3 3 3 5% 7% 53%	1900
	21st to end	Night	17% 5% 2 5% 4 4 4 4 6% 6% 42%	2173
October	1st to 10th	Night	16% 7% 3 7% 5% 5% 5% 3 5% 6% 38%	2280
	11th to 20th	Night	20% 7% 3 7% 5% 5% 4 3 5% 6% 35%	2280
	21st to end	Night	22% 9% 3 8% 4 4 4 4 5% 6% 31%	2579
November	1st to 10th	Night	18% 9% 2 6% 4 3 4 3 5% 7% 38%	2552
	11th to 20th	Night	18% 9% 3 6% 4 4 5% 4 6% 7% 34%	2800
	21st to end	Night	21% 11% 3 7% 5% 4 5% 4 6% 7% 28%	2800
December	1st to 10th	Night	20% 15% 4 8% 5% 5% 5% 4 6% 7% 21%	4580
	11th to 20th	Night	21% 15% 4 8% 4 4 4 3 5% 5% 28%	5208
	21st to end	Night	28% 13% 3 9% 5% 4 4 3 4 5% 22%	6996

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	54% 12% 13% 13% 6% 2	2566
	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	43% 6% 16% 22% 11% 1	4128
	11th to 20th	Day	39% 7% 18% 27% 9%	4083
	21st to end	Day	37% 6% 15% 31% 10% 1	4182
September	1st to 10th	Day	36% 9% 16% 28% 12% 1	2280
	11th to 20th	Day	33% 6% 14% 31% 16% 1	2280
	21st to end	Day	43% 9% 13% 26% 10%	2004
October	1st to 10th	Day	39% 6% 14% 31% 10%	3160
	11th to 20th	Day	42% 6% 18% 26% 8% 1	3140
	21st to end	Day	48% 7% 14% 23% 8%	3309
November	1st to 10th	Day	46% 9% 15% 20% 9% 1	1744
	11th to 20th	Day	51% 8% 13% 18% 10% 1	1600
	21st to end	Day	57% 8% 14% 13% 8%	1600
December	1st to 10th	Day	63% 6% 17% 9% 4	2600
	11th to 20th	Day	63% 7% 10% 13% 7%	2986
	21st to end	Day	60% 6% 10% 18% 6%	3960
January	1st to 10th	Night	59% 10% 14% 13% 4	4514
	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	37% 7% 14% 28% 13% 1	2773
	11th to 20th	Night	35% 7% 16% 30% 11% 1	2812
	21st to end	Night	33% 8% 16% 32% 11% 1	3441
September	1st to 10th	Night	35% 7% 16% 28% 13% 1	1900
	11th to 20th	Night	30% 7% 14% 33% 16% 1	1900
	21st to end	Night	40% 8% 12% 28% 12% 1	2173
October	1st to 10th	Night	37% 6% 11% 26% 19% 1	3800
	11th to 20th	Night	41% 5% 15% 29% 9%	3779
	21st to end	Night	46% 5% 14% 25% 9%	4239
November	1st to 10th	Night	44% 7% 13% 23% 11% 1	2552
	11th to 20th	Night	48% 7% 13% 20% 10% 2	2800
	21st to end	Night	55% 8% 14% 16% 6%	2800
December	1st to 10th	Night	61% 7% 14% 16% 3	4580
	11th to 20th	Night	58% 6% 12% 13% 10% 1	5208
	21st to end	Night	64% 6% 9% 11% 10%	6996

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% 20% 31% 15% 8% 1	192
	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	12% 5% 23% 33% 20% 6%	479
	21st to end	Day	12% 9% 28% 30% 14% 7%	539
September	1st to 10th	Day	12% 9% 31% 27% 14% 7%	490
	11th to 20th	Day	10% 7% 23% 26% 22% 12%	490
	21st to end	Day	17% 9% 27% 27% 15% 4	490
October	1st to 10th	Day	22% 12% 28% 19% 14% 5%	490
	11th to 20th	Day	22% 19% 29% 20% 9% 1	490
	21st to end	Day	29% 17% 28% 21% 5%	502
November	1st to 10th	Day	24% 17% 28% 21% 9% 1	378
	11th to 20th	Day	21% 23% 35% 13% 7% 2	200
	21st to end	Day	24% 21% 36% 14% 5% 1	200
December	1st to 10th	Day	26% 22% 35% 12% 7% 1	200
	11th to 20th	Day	28% 26% 33% 11% 4	200
	21st to end	Day	33% 16% 31% 15% 5%	220
January	1st to 10th	Night	27% 17% 34% 18% 4	785
	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	13% 4 20% 34% 26% 4	564
	21st to end	Night	10% 4 26% 37% 21% 2	814
September	1st to 10th	Night	13% 6% 26% 32% 20% 3	760
	11th to 20th	Night	13% 4 21% 28% 26% 7%	760
	21st to end	Night	19% 7% 23% 28% 19% 3	760
October	1st to 10th	Night	19% 11% 28% 23% 18% 2	760
	11th to 20th	Night	24% 13% 28% 24% 9% 1	760
	21st to end	Night	26% 14% 30% 24% 6%	836
November	1st to 10th	Night	25% 12% 29% 24% 9% 1	780
	11th to 20th	Night	24% 16% 34% 19% 7% 1	800
	21st to end	Night	29% 16% 30% 20% 7%	800
December	1st to 10th	Night	29% 20% 29% 19% 4	800
	11th to 20th	Night	26% 16% 37% 17% 3	800
	21st to end	Night	33% 15% 33% 16% 4	880

Page generated at 2025-01-04 03:23:59. Version ac07

Copyright © 2025 Attilla Danko.