Kawartha Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kawartha Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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% 10% 4 7% 6% 4 5% 5% 5% 7% 32%	78294
	Night	15% 10% 4 8% 7% 3 5% 5% 5% 6% 32%	80887
Transparency	Day	50% 7% 13% 19% 10% 1	78004
	Night	51% 8% 12% 18% 10% 1	80711
Seeing	Day	20% 16% 31% 20% 10% 4	13397
	Night	19% 13% 32% 26% 10% 1	22889

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% 7% 10% 7% 3 4 4 4 4 27%	2517
	11th to 20th	Day	10% 15% 7% 15% 11% 6% 6% 4 3 5% 18%	2625
	21st to end	Day	20% 18% 7% 12% 6% 3 4 4 3 5% 18%	3124
February	1st to 10th	Day	13% 15% 5% 12% 9% 4 6% 4 5% 4 23%	1710
	11th to 20th	Day	12% 13% 8% 11% 8% 4 5% 5% 4 6% 26%	1654
	21st to end	Day	17% 14% 6% 8% 7% 4 6% 4 5% 5% 25%	1372
March	1st to 10th	Day	14% 11% 4 8% 7% 4 5% 5% 6% 7% 29%	1963
	11th to 20th	Day	13% 12% 5% 8% 6% 4 5% 5% 4 5% 34%	1980
	21st to end	Day	18% 11% 3 6% 5% 3 5% 4 4 6% 35%	2178
April	1st to 10th	Day	19% 10% 4 7% 7% 3 4 4 5% 6% 31%	2159
	11th to 20th	Day	20% 8% 3 6% 4 3 4 3 5% 6% 38%	2173
	21st to end	Day	20% 9% 3 7% 6% 3 5% 3 5% 6% 34%	2340
May	1st to 10th	Day	17% 8% 3 7% 7% 4 5% 4 5% 6% 34%	2389
	11th to 20th	Day	15% 7% 3 5% 5% 3 5% 5% 6% 6% 40%	2478
	21st to end	Day	13% 6% 3 5% 5% 4 5% 4 6% 8% 41%	2725
June	1st to 10th	Day	17% 6% 3 5% 5% 3 5% 5% 6% 8% 37%	2520
	11th to 20th	Day	14% 6% 2 5% 5% 3 5% 5% 7% 9% 39%	2520
	21st to end	Day	14% 7% 3 6% 5% 3 5% 5% 6% 7% 38%	2520
July	1st to 10th	Day	10% 4 2 4 4 3 5% 6% 6% 9% 45%	2520
	11th to 20th	Day	11% 6% 3 6% 6% 4 5% 5% 6% 9% 39%	2520
	21st to end	Day	10% 4 3 6% 6% 4 6% 6% 6% 10% 38%	2655
August	1st to 10th	Day	10% 6% 2 5% 5% 3 5% 6% 7% 10% 39%	2327
	11th to 20th	Day	9% 6% 2 5% 6% 4 6% 6% 8% 9% 39%	2303
	21st to end	Day	11% 8% 2 5% 6% 3 5% 5% 6% 9% 39%	2458
September	1st to 10th	Day	13% 6% 3 6% 5% 4 5% 5% 6% 7% 41%	2160
	11th to 20th	Day	12% 5% 2 4 5% 4 5% 4 6% 8% 45%	2103
	21st to end	Day	14% 6% 3 6% 7% 4 5% 4 5% 7% 39%	1913
October	1st to 10th	Day	19% 9% 3 7% 6% 3 5% 4 5% 7% 33%	1800
	11th to 20th	Day	22% 10% 4 9% 5% 3 4 4 5% 6% 27%	1800
	21st to end	Day	24% 11% 4 7% 6% 4 4 5% 5% 6% 23%	1980
November	1st to 10th	Day	14% 11% 3 7% 6% 4 5% 5% 5% 6% 33%	1570
	11th to 20th	Day	14% 13% 4 9% 7% 4 4 6% 7% 8% 25%	1520
	21st to end	Day	19% 15% 5% 9% 7% 3 5% 4 5% 6% 21%	1520
December	1st to 10th	Day	15% 16% 7% 13% 8% 4 5% 5% 5% 6% 17%	1520
	11th to 20th	Day	18% 14% 6% 7% 6% 3 5% 4 4 7% 25%	1906
	21st to end	Day	26% 17% 5% 11% 6% 3 4 4 4 4 16%	2772
January	1st to 10th	Night	17% 16% 7% 10% 9% 4 5% 4 5% 6% 18%	4429
	11th to 20th	Night	13% 11% 7% 13% 11% 5% 5% 4 4 5% 21%	4330
	21st to end	Night	18% 14% 7% 10% 7% 4 4 4 5% 6% 22%	4532
February	1st to 10th	Night	12% 14% 5% 10% 9% 5% 6% 6% 5% 6% 23%	2470
	11th to 20th	Night	13% 11% 6% 10% 7% 4 5% 5% 5% 6% 28%	2397
	21st to end	Night	13% 11% 5% 10% 7% 4 5% 5% 5% 6% 28%	1884
March	1st to 10th	Night	14% 9% 5% 7% 7% 3 4 4 5% 6% 34%	1981
	11th to 20th	Night	14% 11% 5% 7% 5% 3 4 4 6% 6% 35%	1979
	21st to end	Night	15% 8% 3 6% 6% 3 4 4 5% 6% 39%	2178
April	1st to 10th	Night	19% 9% 5% 5% 6% 3 5% 4 5% 7% 31%	1800
	11th to 20th	Night	16% 8% 3 5% 5% 3 4 5% 5% 8% 38%	1750
	21st to end	Night	15% 9% 4 7% 7% 4 5% 4 4 7% 34%	1620
May	1st to 10th	Night	17% 7% 2 6% 5% 3 5% 5% 5% 8% 38%	1570
	11th to 20th	Night	13% 6% 2 4 5% 4 5% 5% 5% 7% 44%	1415
	21st to end	Night	10% 5% 1 4 4 3 5% 5% 6% 8% 49%	1550
June	1st to 10th	Night	13% 5% 3 6% 6% 3 4 5% 7% 8% 39%	1440
	11th to 20th	Night	9% 5% 2 5% 5% 3 6% 5% 5% 9% 45%	1440
	21st to end	Night	11% 7% 3 5% 5% 4 6% 5% 6% 8% 40%	1440
July	1st to 10th	Night	6% 5% 2 5% 5% 3 4 5% 5% 7% 54%	1440
	11th to 20th	Night	9% 5% 2 5% 4 3 6% 6% 5% 9% 47%	1440
	21st to end	Night	9% 4 2 4 4 3 4 6% 7% 9% 48%	1659
August	1st to 10th	Night	7% 5% 2 5% 5% 3 4 5% 6% 7% 50%	1611
	11th to 20th	Night	7% 5% 2 5% 5% 3 4 5% 6% 9% 49%	1598
	21st to end	Night	9% 5% 2 6% 6% 2 5% 6% 6% 7% 45%	1880
September	1st to 10th	Night	10% 5% 3 6% 6% 2 4 5% 6% 8% 45%	1800
	11th to 20th	Night	12% 4 2 4 5% 3 4 4 4 6% 52%	1854
	21st to end	Night	14% 7% 2 5% 5% 3 4 4 5% 7% 43%	2046
October	1st to 10th	Night	18% 7% 3 7% 6% 3 5% 4 5% 7% 35%	2160
	11th to 20th	Night	20% 10% 3 7% 6% 4 4 5% 5% 7% 30%	2160
	21st to end	Night	22% 12% 3 7% 6% 3 5% 5% 5% 6% 27%	2376
November	1st to 10th	Night	17% 9% 4 7% 6% 3 4 4 5% 6% 35%	2506
	11th to 20th	Night	16% 11% 4 7% 6% 3 5% 5% 6% 7% 27%	2660
	21st to end	Night	18% 11% 5% 8% 7% 4 6% 5% 6% 6% 23%	2660
December	1st to 10th	Night	18% 15% 7% 10% 7% 4 6% 5% 5% 6% 19%	2660
	11th to 20th	Night	16% 17% 6% 10% 7% 4 5% 5% 5% 5% 21%	3288
	21st to end	Night	25% 18% 6% 12% 7% 3 4 3 4 4 13%	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	59% 8% 14% 12% 7% 1	2518
	11th to 20th	Day	69% 6% 10% 9% 6%	2625
	21st to end	Day	70% 5% 9% 9% 5% 1	3124
February	1st to 10th	Day	63% 6% 11% 15% 4 1	1710
	11th to 20th	Day	59% 7% 9% 14% 9% 1	1663
	21st to end	Day	62% 5% 10% 15% 8% 1	1372
March	1st to 10th	Day	54% 7% 15% 13% 10% 1	1966
	11th to 20th	Day	52% 6% 10% 17% 12% 2	1980
	21st to end	Day	51% 4 8% 17% 15% 3	2178
April	1st to 10th	Day	54% 5% 10% 19% 10% 2	2159
	11th to 20th	Day	48% 5% 10% 22% 14% 1	2173
	21st to end	Day	51% 5% 10% 18% 13% 3	2340
May	1st to 10th	Day	50% 6% 10% 18% 13% 3	2389
	11th to 20th	Day	42% 7% 10% 25% 15% 1	2482
	21st to end	Day	40% 8% 16% 21% 13% 2	2725
June	1st to 10th	Day	45% 8% 12% 21% 14% 1	2520
	11th to 20th	Day	40% 8% 13% 24% 14% 1	2520
	21st to end	Day	43% 8% 14% 22% 12% 1	2520
July	1st to 10th	Day	32% 9% 15% 25% 18% 1	2450
	11th to 20th	Day	39% 8% 16% 27% 9% 1	2445
	21st to end	Day	40% 10% 15% 24% 11% 1	2506
August	1st to 10th	Day	38% 10% 17% 24% 10% 1	2314
	11th to 20th	Day	38% 10% 16% 23% 12%	2303
	21st to end	Day	40% 8% 15% 25% 11% 1	2458
September	1st to 10th	Day	40% 8% 14% 27% 10% 1	2160
	11th to 20th	Day	36% 8% 14% 29% 13% 1	2103
	21st to end	Day	43% 8% 15% 25% 8%	1913
October	1st to 10th	Day	50% 7% 12% 19% 11% 1	1800
	11th to 20th	Day	56% 8% 14% 16% 5% 1	1800
	21st to end	Day	61% 7% 12% 14% 6%	1980
November	1st to 10th	Day	49% 8% 15% 19% 8% 1	1570
	11th to 20th	Day	54% 10% 14% 13% 7% 1	1520
	21st to end	Day	62% 8% 12% 13% 4	1520
December	1st to 10th	Day	67% 8% 12% 10% 3	1520
	11th to 20th	Day	59% 9% 12% 12% 7%	1906
	21st to end	Day	72% 6% 9% 10% 3	2772
January	1st to 10th	Night	63% 9% 13% 11% 4	4429
	11th to 20th	Night	64% 8% 12% 11% 4 1	4330
	21st to end	Night	63% 7% 12% 12% 5% 1	4532
February	1st to 10th	Night	61% 8% 9% 17% 4 1	2470
	11th to 20th	Night	56% 6% 11% 19% 8% 1	2399
	21st to end	Night	54% 7% 13% 17% 7% 1	1884
March	1st to 10th	Night	49% 6% 14% 18% 10% 2	1991
	11th to 20th	Night	50% 7% 11% 21% 11% 1	1980
	21st to end	Night	46% 6% 10% 21% 15% 3	2178
April	1st to 10th	Night	51% 6% 10% 20% 12% 1	1800
	11th to 20th	Night	44% 7% 10% 20% 16% 2	1750
	21st to end	Night	49% 6% 12% 15% 15% 2	1620
May	1st to 10th	Night	45% 7% 12% 18% 16% 3	1570
	11th to 20th	Night	39% 6% 10% 24% 18% 3	1416
	21st to end	Night	32% 7% 15% 24% 17% 4	1551
June	1st to 10th	Night	41% 7% 12% 24% 14% 2	1440
	11th to 20th	Night	35% 8% 12% 22% 20% 3	1440
	21st to end	Night	40% 9% 14% 22% 14% 1	1440
July	1st to 10th	Night	29% 8% 11% 29% 21% 3	1400
	11th to 20th	Night	33% 8% 13% 29% 17% 1	1392
	21st to end	Night	30% 9% 15% 31% 14% 1	1567
August	1st to 10th	Night	32% 7% 21% 25% 14% 1	1600
	11th to 20th	Night	30% 9% 19% 27% 14% 1	1598
	21st to end	Night	36% 9% 13% 28% 13% 1	1880
September	1st to 10th	Night	37% 7% 16% 26% 13% 1	1800
	11th to 20th	Night	31% 8% 13% 30% 16% 1	1854
	21st to end	Night	40% 8% 12% 29% 11% 1	2046
October	1st to 10th	Night	48% 8% 12% 18% 13% 1	2160
	11th to 20th	Night	52% 9% 13% 20% 6%	2160
	21st to end	Night	56% 9% 12% 13% 9% 1	2376
November	1st to 10th	Night	48% 7% 13% 21% 10% 1	2506
	11th to 20th	Night	53% 9% 14% 14% 8% 2	2660
	21st to end	Night	58% 10% 16% 12% 4	2660
December	1st to 10th	Night	65% 8% 12% 11% 4	2660
	11th to 20th	Night	63% 7% 12% 13% 4	3288
	21st to end	Night	74% 7% 8% 9% 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	20% 25% 34% 14% 6% 1	180
	11th to 20th	Day	22% 29% 30% 13% 5% 1	211
	21st to end	Day	23% 24% 34% 14% 4	297
February	1st to 10th	Day	30% 24% 31% 13% 2	270
	11th to 20th	Day	23% 31% 37% 8% 1	267
	21st to end	Day	38% 23% 31% 8%	238
March	1st to 10th	Day	21% 23% 37% 16% 3	420
	11th to 20th	Day	24% 21% 35% 15% 4	420
	21st to end	Day	31% 17% 31% 15% 5% 1	462
April	1st to 10th	Day	24% 20% 33% 15% 6% 1	420
	11th to 20th	Day	27% 20% 25% 14% 10% 4	412
	21st to end	Day	26% 17% 34% 12% 9% 1	420
May	1st to 10th	Day	24% 14% 29% 21% 7% 4	423
	11th to 20th	Day	19% 13% 36% 19% 10% 4	447
	21st to end	Day	15% 10% 32% 24% 12% 6%	485
June	1st to 10th	Day	17% 11% 37% 23% 10% 2	450
	11th to 20th	Day	15% 14% 26% 27% 13% 5%	450
	21st to end	Day	17% 9% 32% 28% 11% 4	450
July	1st to 10th	Day	9% 7% 27% 33% 18% 6%	445
	11th to 20th	Day	14% 10% 25% 27% 17% 7%	444
	21st to end	Day	9% 6% 36% 33% 11% 5%	488
August	1st to 10th	Day	9% 7% 29% 29% 17% 9%	446
	11th to 20th	Day	9% 8% 26% 26% 23% 8%	439
	21st to end	Day	13% 9% 29% 26% 15% 7%	495
September	1st to 10th	Day	12% 8% 30% 25% 15% 9%	450
	11th to 20th	Day	10% 8% 30% 24% 16% 12%	450
	21st to end	Day	14% 14% 29% 23% 14% 6%	450
October	1st to 10th	Day	22% 15% 29% 17% 12% 5%	450
	11th to 20th	Day	22% 22% 34% 16% 5% 2	450
	21st to end	Day	29% 21% 29% 16% 4	495
November	1st to 10th	Day	26% 19% 29% 20% 6%	255
	11th to 20th	Day	24% 22% 37% 12% 3 1	180
	21st to end	Day	24% 22% 41% 11% 2	180
December	1st to 10th	Day	23% 27% 36% 10% 4 1	180
	11th to 20th	Day	29% 28% 27% 13% 2 1	180
	21st to end	Day	30% 23% 34% 11% 1	198
January	1st to 10th	Night	22% 21% 34% 17% 5%	760
	11th to 20th	Night	26% 15% 33% 20% 5% 1	760
	21st to end	Night	18% 16% 36% 25% 5% 1	836
February	1st to 10th	Night	20% 17% 40% 20% 2	760
	11th to 20th	Night	21% 18% 39% 18% 4	742
	21st to end	Night	21% 19% 37% 19% 3	592
March	1st to 10th	Night	20% 18% 37% 22% 3	720
	11th to 20th	Night	21% 19% 35% 21% 4 1	720
	21st to end	Night	20% 12% 36% 24% 7% 1	792
April	1st to 10th	Night	24% 16% 33% 22% 4	720
	11th to 20th	Night	21% 14% 32% 22% 10% 1	686
	21st to end	Night	19% 12% 34% 25% 10%	540
May	1st to 10th	Night	20% 6% 29% 31% 12% 2	490
	11th to 20th	Night	15% 9% 33% 34% 9%	354
	21st to end	Night	12% 7% 31% 35% 15% 1	389
June	1st to 10th	Night	13% 8% 33% 34% 11% 1	360
	11th to 20th	Night	10% 9% 26% 41% 14% 1	360
	21st to end	Night	11% 6% 28% 40% 15%	360
July	1st to 10th	Night	6% 5% 24% 45% 19% 1	350
	11th to 20th	Night	8% 4 30% 36% 21% 1	348
	21st to end	Night	9% 3 28% 42% 18% 1	479
August	1st to 10th	Night	9% 5% 20% 39% 25% 2	537
	11th to 20th	Night	8% 4 19% 37% 28% 4	534
	21st to end	Night	12% 5% 26% 34% 22% 2	692
September	1st to 10th	Night	12% 6% 27% 33% 19% 3	720
	11th to 20th	Night	13% 6% 23% 33% 20% 5%	720
	21st to end	Night	16% 11% 23% 30% 17% 4	720
October	1st to 10th	Night	20% 8% 29% 26% 15% 2	720
	11th to 20th	Night	24% 15% 33% 20% 8% 1	720
	21st to end	Night	28% 14% 32% 21% 5%	792
November	1st to 10th	Night	23% 15% 29% 24% 9%	740
	11th to 20th	Night	21% 18% 34% 19% 6% 1	760
	21st to end	Night	24% 17% 33% 22% 4	760
December	1st to 10th	Night	26% 18% 37% 16% 3	760
	11th to 20th	Night	22% 21% 35% 19% 3 1	760
	21st to end	Night	28% 18% 34% 18% 2	836

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