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 2025-03-12.

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	14% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	108980
	Night	14% 11% 4 10% 5% 5% 5% 4 5% 6% 32%	110014
Transparency	Day	49% 7% 13% 20% 10% 1	112610
	Night	49% 8% 13% 19% 10% 1	114547
Seeing	Day	20% 16% 31% 20% 10% 4	14743
	Night	19% 13% 32% 26% 10% 1	24224

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	12% 13% 6% 12% 6% 5% 4 4 5% 5% 27%	3597
	11th to 20th	Day	9% 16% 7% 19% 10% 8% 5% 3 3 5% 15%	3730
	21st to end	Day	15% 17% 6% 14% 6% 6% 5% 4 4 5% 18%	4466
February	1st to 10th	Day	13% 16% 5% 13% 7% 6% 5% 4 4 4 23%	1800
	11th to 20th	Day	12% 15% 7% 12% 6% 5% 4 4 5% 6% 25%	1753
	21st to end	Day	16% 14% 6% 9% 6% 6% 5% 3 5% 5% 24%	1530
March	1st to 10th	Day	19% 13% 5% 8% 5% 4 4 3 5% 6% 30%	3527
	11th to 20th	Day	10% 16% 6% 9% 5% 5% 5% 5% 5% 5% 29%	3491
	21st to end	Day	15% 10% 2 6% 4 4 4 3 5% 5% 41%	3815
April	1st to 10th	Day	19% 11% 4 9% 5% 5% 4 3 5% 5% 31%	2279
	11th to 20th	Day	21% 9% 2 7% 3 4 4 3 5% 5% 37%	2296
	21st to end	Day	19% 10% 3 7% 5% 5% 4 3 5% 5% 34%	2470
May	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 3 5% 6% 34%	4199
	11th to 20th	Day	15% 10% 3 7% 4 5% 5% 4 6% 8% 34%	4398
	21st to end	Day	13% 7% 2 6% 4 4 4 4 6% 7% 44%	4837
June	1st to 10th	Day	16% 8% 2 7% 4 4 5% 4 6% 8% 35%	2660
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 8% 38%	2660
	21st to end	Day	15% 7% 3 6% 5% 4 5% 4 7% 7% 37%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 6% 5% 8% 11% 37%	4440
	11th to 20th	Day	11% 5% 2 5% 4 5% 5% 4 7% 9% 43%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 10% 42%	4658
August	1st to 10th	Day	15% 9% 3 6% 4 4 4 4 7% 8% 37%	4104
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 10% 36%	4044
	21st to end	Day	9% 7% 2 6% 5% 4 5% 4 7% 9% 43%	4318
September	1st to 10th	Day	12% 6% 3 7% 4 4 5% 3 6% 7% 42%	2280
	11th to 20th	Day	11% 5% 2 5% 4 5% 4 4 6% 8% 46%	2219
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 3 5% 7% 39%	2019
October	1st to 10th	Day	18% 9% 3 8% 5% 5% 4 4 5% 7% 33%	1900
	11th to 20th	Day	21% 10% 4 9% 5% 4 4 3 5% 6% 28%	1900
	21st to end	Day	23% 12% 4 8% 5% 6% 4 3 5% 6% 24%	2090
November	1st to 10th	Day	13% 12% 3 7% 5% 5% 5% 4 5% 6% 33%	1654
	11th to 20th	Day	13% 14% 4 10% 6% 5% 4 5% 7% 7% 25%	1600
	21st to end	Day	18% 17% 5% 10% 6% 5% 5% 3 5% 6% 20%	1600
December	1st to 10th	Day	16% 21% 6% 14% 6% 5% 4 4 5% 6% 14%	2600
	11th to 20th	Day	17% 18% 5% 10% 6% 4 4 3 4 6% 23%	2986
	21st to end	Day	22% 18% 5% 14% 5% 4 4 3 4 4 17%	3960
January	1st to 10th	Night	13% 14% 7% 14% 7% 5% 4 3 5% 6% 20%	6349
	11th to 20th	Night	11% 12% 7% 17% 10% 7% 6% 3 5% 6% 18%	6150
	21st to end	Night	13% 14% 7% 13% 6% 5% 4 3 5% 6% 23%	6490
February	1st to 10th	Night	12% 16% 5% 12% 8% 6% 5% 4 5% 5% 22%	2600
	11th to 20th	Night	13% 13% 5% 11% 6% 5% 5% 4 5% 6% 27%	2533
	21st to end	Night	13% 12% 5% 12% 6% 5% 6% 4 6% 6% 27%	2099
March	1st to 10th	Night	16% 10% 4 9% 6% 4 4 3 5% 6% 31%	3529
	11th to 20th	Night	13% 12% 5% 10% 5% 5% 4 4 6% 6% 31%	3497
	21st to end	Night	15% 8% 4 6% 5% 4 4 4 5% 7% 40%	3817
April	1st to 10th	Night	19% 11% 4 6% 5% 4 5% 4 5% 6% 31%	1900
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 4 5% 7% 37%	1848
	21st to end	Night	15% 9% 4 8% 6% 5% 5% 3 5% 6% 34%	1710
May	1st to 10th	Night	17% 8% 2 7% 5% 4 4 4 4 6% 38%	2741
	11th to 20th	Night	16% 7% 2 6% 5% 5% 5% 4 6% 7% 38%	2495
	21st to end	Night	11% 6% 2 5% 4 4 4 3 5% 7% 48%	2738
June	1st to 10th	Night	13% 6% 3 8% 5% 3 4 4 7% 8% 38%	1520
	11th to 20th	Night	9% 5% 2 6% 4 5% 6% 4 6% 8% 45%	1520
	21st to end	Night	12% 8% 3 6% 4 5% 5% 4 6% 8% 40%	1520
July	1st to 10th	Night	6% 5% 2 7% 4 5% 5% 4 6% 7% 48%	2520
	11th to 20th	Night	12% 5% 2 5% 3 4 4 4 5% 8% 49%	2520
	21st to end	Night	8% 5% 1 5% 3 4 5% 4 6% 9% 50%	2891
August	1st to 10th	Night	9% 6% 2 6% 4 4 4 4 5% 7% 48%	2825
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 6% 8% 47%	2785
	21st to end	Night	10% 6% 2 6% 5% 3 5% 4 6% 7% 47%	3306
September	1st to 10th	Night	10% 5% 3 7% 5% 4 4 4 6% 7% 46%	1900
	11th to 20th	Night	11% 4 2 5% 4 4 3 3 4 6% 53%	1957
	21st to end	Night	15% 7% 3 6% 4 4 4 3 5% 7% 42%	2160
October	1st to 10th	Night	17% 7% 3 8% 5% 5% 4 3 5% 7% 36%	2280
	11th to 20th	Night	19% 10% 3 8% 6% 4 4 4 5% 7% 31%	2280
	21st to end	Night	21% 11% 3 8% 5% 4 4 4 5% 6% 28%	2508
November	1st to 10th	Night	16% 10% 4 8% 5% 4 4 3 6% 6% 35%	2642
	11th to 20th	Night	16% 13% 4 8% 5% 5% 5% 4 6% 7% 27%	2800
	21st to end	Night	17% 13% 5% 9% 6% 6% 5% 4 6% 6% 23%	2800
December	1st to 10th	Night	15% 18% 6% 12% 7% 6% 5% 4 6% 6% 16%	4580
	11th to 20th	Night	15% 16% 6% 13% 6% 6% 5% 4 5% 5% 18%	5208
	21st to end	Night	21% 17% 5% 16% 6% 4 4 3 4 5% 15%	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	55% 7% 12% 16% 9% 1	3598
	11th to 20th	Day	71% 6% 9% 8% 5%	3761
	21st to end	Day	67% 6% 10% 9% 8% 1	4466
February	1st to 10th	Day	63% 6% 10% 16% 4 1	1800
	11th to 20th	Day	60% 7% 9% 15% 9% 1	1762
	21st to end	Day	61% 6% 10% 15% 8% 1	1530
March	1st to 10th	Day	53% 7% 14% 15% 10% 1	3530
	11th to 20th	Day	52% 8% 14% 17% 9% 1	3491
	21st to end	Day	43% 5% 9% 23% 18% 2	3815
April	1st to 10th	Day	55% 5% 10% 19% 10% 1	2279
	11th to 20th	Day	49% 5% 10% 21% 15% 1	2296
	21st to end	Day	51% 5% 10% 17% 13% 3	2470
May	1st to 10th	Day	48% 8% 11% 20% 12% 1	4211
	11th to 20th	Day	46% 10% 12% 21% 10% 1	4402
	21st to end	Day	37% 8% 14% 22% 15% 3	4837
June	1st to 10th	Day	45% 8% 12% 20% 14% 1	2660
	11th to 20th	Day	41% 8% 13% 24% 14% 1	2660
	21st to end	Day	44% 8% 13% 22% 12% 1	2660
July	1st to 10th	Day	37% 8% 17% 22% 14% 1	4370
	11th to 20th	Day	34% 8% 17% 32% 9% 1	4365
	21st to end	Day	35% 10% 14% 28% 14%	4509
August	1st to 10th	Day	44% 7% 15% 23% 10% 1	4091
	11th to 20th	Day	40% 8% 16% 26% 9%	4083
	21st to end	Day	34% 8% 15% 32% 11% 1	4318
September	1st to 10th	Day	40% 8% 15% 27% 10% 1	2280
	11th to 20th	Day	34% 7% 14% 30% 14% 1	2219
	21st to end	Day	44% 8% 15% 24% 10%	2019
October	1st to 10th	Day	40% 8% 14% 27% 10% 1	3160
	11th to 20th	Day	44% 7% 16% 20% 12% 1	3140
	21st to end	Day	51% 8% 15% 19% 7%	3428
November	1st to 10th	Day	49% 8% 14% 19% 8% 1	1654
	11th to 20th	Day	54% 10% 14% 14% 8% 1	1600
	21st to end	Day	62% 8% 12% 13% 4	1600
December	1st to 10th	Day	70% 7% 13% 8% 2	2600
	11th to 20th	Day	62% 8% 11% 13% 7%	2986
	21st to end	Day	69% 7% 8% 9% 7%	3960
January	1st to 10th	Night	60% 8% 11% 13% 8%	6349
	11th to 20th	Night	65% 8% 11% 10% 5% 1	6194
	21st to end	Night	59% 7% 11% 11% 11% 1	6490
February	1st to 10th	Night	61% 7% 10% 16% 5% 1	2600
	11th to 20th	Night	57% 6% 11% 18% 8%	2535
	21st to end	Night	54% 7% 13% 18% 7% 1	2099
March	1st to 10th	Night	51% 7% 11% 20% 9% 1	3539
	11th to 20th	Night	49% 8% 16% 18% 8% 1	3498
	21st to end	Night	41% 6% 13% 22% 17% 2	3817
April	1st to 10th	Night	52% 6% 10% 20% 12% 1	1900
	11th to 20th	Night	45% 7% 10% 20% 16% 2	1848
	21st to end	Night	49% 6% 12% 15% 15% 2	1710
May	1st to 10th	Night	45% 7% 13% 16% 17% 2	2748
	11th to 20th	Night	43% 9% 13% 22% 11% 2	2496
	21st to end	Night	33% 7% 14% 25% 19% 2	2739
June	1st to 10th	Night	42% 7% 12% 23% 14% 2	1520
	11th to 20th	Night	34% 9% 13% 22% 19% 2	1520
	21st to end	Night	41% 8% 13% 22% 14% 1	1520
July	1st to 10th	Night	32% 8% 16% 24% 18% 2	2480
	11th to 20th	Night	33% 7% 13% 33% 14%	2472
	21st to end	Night	29% 9% 15% 33% 14% 1	2799
August	1st to 10th	Night	35% 6% 16% 25% 17% 1	2814
	11th to 20th	Night	34% 7% 18% 28% 13% 1	2812
	21st to end	Night	32% 8% 14% 31% 13% 1	3306
September	1st to 10th	Night	36% 7% 15% 27% 13% 1	1900
	11th to 20th	Night	30% 7% 13% 31% 17% 1	1957
	21st to end	Night	40% 8% 12% 28% 11% 1	2160
October	1st to 10th	Night	35% 7% 11% 27% 19% 1	3800
	11th to 20th	Night	42% 8% 16% 25% 9%	3779
	21st to end	Night	44% 9% 15% 24% 7%	4120
November	1st to 10th	Night	48% 8% 13% 21% 10% 1	2642
	11th to 20th	Night	53% 9% 14% 15% 8% 2	2800
	21st to end	Night	58% 10% 15% 13% 4	2800
December	1st to 10th	Night	64% 8% 15% 9% 3	4580
	11th to 20th	Night	64% 9% 11% 11% 5%	5208
	21st to end	Night	71% 7% 8% 9% 6%	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	20% 26% 35% 14% 5% 1	200
	11th to 20th	Day	21% 29% 30% 14% 5% 1	235
	21st to end	Day	23% 25% 34% 14% 4	330
February	1st to 10th	Day	31% 24% 31% 12% 2	300
	11th to 20th	Day	26% 31% 34% 8% 1	300
	21st to end	Day	36% 21% 34% 9%	294
March	1st to 10th	Day	23% 23% 36% 16% 3	500
	11th to 20th	Day	25% 22% 34% 15% 4	464
	21st to end	Day	30% 18% 32% 14% 5% 1	506
April	1st to 10th	Day	25% 21% 33% 14% 6% 1	460
	11th to 20th	Day	30% 21% 24% 13% 9% 3	452
	21st to end	Day	26% 18% 35% 12% 9% 1	460
May	1st to 10th	Day	24% 14% 30% 21% 8% 4	463
	11th to 20th	Day	18% 13% 34% 21% 11% 3	487
	21st to end	Day	16% 11% 32% 23% 12% 5%	529
June	1st to 10th	Day	18% 11% 36% 23% 10% 2	490
	11th to 20th	Day	15% 13% 28% 26% 13% 4	490
	21st to end	Day	18% 11% 31% 26% 10% 3	490
July	1st to 10th	Day	9% 8% 28% 32% 17% 5%	485
	11th to 20th	Day	13% 10% 26% 26% 17% 7%	484
	21st to end	Day	9% 6% 34% 33% 13% 5%	532
August	1st to 10th	Day	10% 8% 29% 28% 16% 8%	486
	11th to 20th	Day	10% 9% 26% 25% 23% 8%	479
	21st to end	Day	12% 9% 29% 27% 16% 7%	539
September	1st to 10th	Day	13% 9% 29% 25% 16% 8%	490
	11th to 20th	Day	10% 7% 28% 23% 18% 14%	490
	21st to end	Day	15% 14% 28% 23% 14% 6%	490
October	1st to 10th	Day	21% 15% 30% 17% 12% 5%	490
	11th to 20th	Day	21% 21% 34% 16% 6% 2	490
	21st to end	Day	28% 22% 29% 17% 4	539
November	1st to 10th	Day	27% 19% 29% 20% 5%	279
	11th to 20th	Day	23% 23% 38% 12% 4 1	200
	21st to end	Day	24% 23% 40% 12% 2	200
December	1st to 10th	Day	25% 27% 34% 11% 4 1	200
	11th to 20th	Day	30% 28% 26% 13% 2 1	200
	21st to end	Day	29% 22% 35% 11% 2 1	220
January	1st to 10th	Night	22% 21% 36% 17% 5%	800
	11th to 20th	Night	26% 15% 33% 20% 5% 1	800
	21st to end	Night	18% 16% 36% 24% 5% 1	880
February	1st to 10th	Night	20% 18% 40% 20% 2	800
	11th to 20th	Night	22% 19% 38% 18% 4	783
	21st to end	Night	20% 19% 37% 20% 3	660
March	1st to 10th	Night	20% 18% 37% 21% 3	800
	11th to 20th	Night	20% 20% 35% 20% 4 1	767
	21st to end	Night	19% 14% 36% 24% 7% 1	836
April	1st to 10th	Night	24% 16% 34% 22% 4	760
	11th to 20th	Night	22% 15% 32% 22% 9% 1	724
	21st to end	Night	18% 13% 34% 25% 10%	570
May	1st to 10th	Night	19% 6% 29% 32% 12% 2	517
	11th to 20th	Night	15% 9% 32% 34% 9%	374
	21st to end	Night	12% 7% 31% 35% 14% 1	411
June	1st to 10th	Night	14% 8% 32% 35% 11% 1	380
	11th to 20th	Night	10% 9% 26% 41% 13% 1	380
	21st to end	Night	12% 7% 28% 39% 14%	380
July	1st to 10th	Night	6% 5% 24% 46% 18% 1	370
	11th to 20th	Night	9% 4 29% 35% 22% 1	368
	21st to end	Night	9% 3 27% 42% 19% 1	506
August	1st to 10th	Night	9% 5% 20% 39% 25% 2	567
	11th to 20th	Night	9% 4 20% 36% 28% 3	564
	21st to end	Night	11% 5% 25% 34% 23% 2	731
September	1st to 10th	Night	12% 6% 27% 33% 19% 3	760
	11th to 20th	Night	12% 5% 22% 32% 23% 6%	760
	21st to end	Night	17% 10% 22% 30% 17% 4	760
October	1st to 10th	Night	19% 9% 30% 26% 15% 2	760
	11th to 20th	Night	23% 15% 32% 21% 8% 1	760
	21st to end	Night	27% 15% 33% 21% 5%	836
November	1st to 10th	Night	23% 16% 29% 24% 8%	780
	11th to 20th	Night	22% 18% 34% 19% 6% 1	800
	21st to end	Night	24% 18% 32% 22% 4	800
December	1st to 10th	Night	25% 18% 37% 16% 3	800
	11th to 20th	Night	22% 21% 35% 19% 3 1	800
	21st to end	Night	28% 18% 34% 18% 3	880

Page generated at 2025-03-09 08:08:45. Version ac07

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