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 2024-10-20.

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% 3 8% 5% 5% 5% 4 6% 7% 34%	101367
	Night	15% 10% 4 8% 5% 5% 4 4 5% 6% 33%	97322
Transparency	Day	48% 7% 13% 20% 10% 1	101128
	Night	49% 8% 13% 19% 10% 1	97180
Seeing	Day	20% 16% 31% 20% 10% 4	14362
	Night	19% 13% 31% 26% 10% 1	23652

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% 11% 6% 4 4 3 4 4 26%	2517
	11th to 20th	Day	10% 16% 7% 17% 8% 7% 5% 3 3 5% 18%	2625
	21st to end	Day	20% 19% 6% 13% 5% 4 4 3 3 5% 18%	3124
February	1st to 10th	Day	13% 16% 5% 13% 7% 6% 5% 4 4 4 23%	1710
	11th to 20th	Day	11% 14% 7% 12% 6% 5% 4 4 5% 6% 26%	1663
	21st to end	Day	16% 14% 6% 9% 6% 6% 5% 3 5% 6% 25%	1456
March	1st to 10th	Day	18% 13% 5% 8% 5% 3 4 3 5% 6% 30%	3418
	11th to 20th	Day	10% 16% 6% 9% 5% 5% 5% 5% 5% 5% 29%	3480
	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%	1890
	21st to end	Day	24% 12% 4 8% 5% 5% 4 3 5% 5% 23%	1980
November	1st to 10th	Day	13% 12% 3 8% 5% 5% 5% 4 5% 6% 33%	1570
	11th to 20th	Day	14% 14% 4 10% 7% 5% 4 5% 7% 7% 25%	1520
	21st to end	Day	19% 16% 5% 10% 6% 4 5% 3 5% 6% 21%	1520
December	1st to 10th	Day	15% 17% 7% 14% 7% 6% 5% 4 5% 6% 16%	1520
	11th to 20th	Day	18% 15% 4 9% 5% 4 5% 3 5% 7% 25%	1906
	21st to end	Day	25% 18% 5% 12% 5% 4 4 3 4 4 16%	2772
January	1st to 10th	Night	16% 17% 7% 12% 7% 6% 4 4 5% 6% 18%	4429
	11th to 20th	Night	12% 12% 6% 15% 9% 7% 5% 3 4 5% 21%	4330
	21st to end	Night	18% 14% 7% 11% 6% 5% 4 3 5% 6% 22%	4532
February	1st to 10th	Night	12% 15% 5% 11% 8% 7% 5% 4 5% 5% 22%	2470
	11th to 20th	Night	13% 13% 5% 11% 6% 5% 5% 4 5% 6% 28%	2403
	21st to end	Night	13% 11% 4 12% 6% 5% 6% 4 6% 6% 27%	1998
March	1st to 10th	Night	16% 10% 4 9% 6% 4 4 3 5% 6% 32%	3419
	11th to 20th	Night	13% 12% 5% 10% 5% 5% 4 4 6% 6% 30%	3479
	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%	2275
	21st to end	Night	22% 12% 3 8% 5% 5% 4 4 5% 6% 27%	2376
November	1st to 10th	Night	17% 10% 4 8% 5% 4 4 3 6% 6% 35%	2506
	11th to 20th	Night	16% 13% 4 8% 5% 5% 5% 4 6% 7% 27%	2660
	21st to end	Night	17% 13% 4 9% 6% 6% 5% 4 6% 6% 23%	2660
December	1st to 10th	Night	18% 17% 6% 10% 7% 6% 5% 4 5% 5% 18%	2660
	11th to 20th	Night	16% 18% 5% 11% 6% 6% 5% 4 5% 5% 20%	3288
	21st to end	Night	25% 18% 6% 13% 6% 4 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% 15% 9% 1	1672
	21st to end	Day	60% 6% 10% 15% 8% 1	1456
March	1st to 10th	Day	53% 7% 14% 15% 10% 1	3421
	11th to 20th	Day	52% 8% 13% 17% 9% 1	3480
	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	49% 7% 12% 20% 10% 1	1900
	11th to 20th	Day	55% 8% 14% 17% 6% 1	1890
	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% 18% 8%	2405
	21st to end	Night	54% 7% 13% 18% 7% 1	1998
March	1st to 10th	Night	51% 7% 11% 21% 9% 1	3429
	11th to 20th	Night	49% 8% 16% 17% 8% 1	3480
	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	47% 7% 12% 19% 14% 1	2280
	11th to 20th	Night	51% 9% 14% 20% 7%	2275
	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% 36% 9% 1	270
	21st to end	Day	36% 23% 32% 8%	268
March	1st to 10th	Day	21% 22% 37% 16% 3	460
	11th to 20th	Day	25% 21% 35% 15% 4	460
	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% 15% 6% 2	486
	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% 38% 18% 4	743
	21st to end	Night	21% 19% 37% 20% 3	628
March	1st to 10th	Night	20% 18% 37% 21% 4	760
	11th to 20th	Night	21% 20% 34% 21% 4 1	760
	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	759
	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

Page generated at 2024-10-17 13:09:43. Version ac07

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