Kemptville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kemptville clear sky chart from 2005-11-06 to 2024-09-29.

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	17% 10% 3 8% 5% 5% 5% 4 5% 7% 33%	101209
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 31%	97023
Transparency	Day	50% 8% 12% 20% 9% 1	100967
	Night	52% 7% 12% 18% 9% 1	96885
Seeing	Day	23% 15% 31% 20% 8% 3	14384
	Night	23% 13% 30% 25% 9% 1	23441

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	16% 16% 5% 13% 6% 6% 4 3 4 4 22%	2517
	11th to 20th	Day	15% 15% 5% 13% 6% 6% 5% 4 4 6% 22%	2520
	21st to end	Day	17% 17% 7% 12% 7% 7% 5% 3 5% 4 17%	2900
February	1st to 10th	Day	17% 15% 5% 12% 8% 4 4 3 4 5% 24%	1710
	11th to 20th	Day	13% 16% 5% 10% 7% 5% 5% 3 4 5% 27%	1682
	21st to end	Day	20% 14% 5% 10% 6% 5% 4 3 5% 5% 24%	1570
March	1st to 10th	Day	20% 13% 4 9% 6% 4 4 3 4 6% 27%	3116
	11th to 20th	Day	13% 16% 5% 9% 6% 5% 5% 3 5% 5% 29%	3470
	21st to end	Day	14% 9% 3 7% 5% 4 4 3 5% 6% 41%	4033
April	1st to 10th	Day	22% 11% 3 7% 4 5% 4 3 4 6% 32%	2280
	11th to 20th	Day	22% 10% 3 7% 4 3 3 3 4 5% 36%	2254
	21st to end	Day	23% 9% 3 7% 5% 4 4 3 5% 5% 31%	2391
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 4 4 5% 7% 31%	4426
	11th to 20th	Day	18% 10% 3 8% 4 5% 4 4 5% 7% 32%	4398
	21st to end	Day	15% 7% 3 6% 4 5% 5% 4 5% 8% 39%	4837
June	1st to 10th	Day	22% 8% 3 7% 5% 5% 5% 4 6% 6% 30%	2660
	11th to 20th	Day	15% 5% 2 7% 4 5% 5% 5% 6% 7% 38%	2660
	21st to end	Day	20% 8% 2 7% 5% 5% 4 4 6% 6% 32%	2660
July	1st to 10th	Day	12% 6% 3 6% 5% 5% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 5% 7% 8% 39%	4440
	21st to end	Day	11% 6% 2 5% 4 5% 5% 4 7% 9% 42%	4814
August	1st to 10th	Day	15% 8% 3 8% 5% 5% 4 4 5% 7% 36%	4342
	11th to 20th	Day	16% 7% 2 6% 4 5% 5% 4 6% 8% 38%	3962
	21st to end	Day	15% 6% 2 6% 4 4 5% 3 7% 9% 38%	4180
September	1st to 10th	Day	14% 5% 3 6% 4 5% 4 4 5% 7% 42%	2280
	11th to 20th	Day	14% 4 2 6% 4 4 4 4 5% 7% 47%	2275
	21st to end	Day	19% 6% 3 5% 4 4 4 4 6% 7% 39%	2019
October	1st to 10th	Day	20% 8% 3 7% 6% 4 4 3 5% 5% 35%	1800
	11th to 20th	Day	20% 11% 3 9% 5% 4 5% 4 5% 6% 28%	1800
	21st to end	Day	27% 11% 3 6% 5% 5% 4 3 4 4 27%	1835
November	1st to 10th	Day	16% 10% 2 7% 6% 5% 5% 5% 5% 6% 34%	1671
	11th to 20th	Day	19% 13% 4 8% 5% 5% 4 4 5% 5% 28%	1549
	21st to end	Day	21% 15% 4 9% 5% 5% 6% 4 5% 6% 21%	1520
December	1st to 10th	Day	24% 17% 4 11% 6% 4 5% 3 4 5% 16%	1520
	11th to 20th	Day	21% 17% 4 9% 5% 4 4 3 4 4 24%	1906
	21st to end	Day	27% 17% 5% 11% 5% 3 3 2 2 3 20%	2772
January	1st to 10th	Night	18% 16% 7% 11% 6% 4 4 3 5% 6% 21%	4429
	11th to 20th	Night	14% 15% 6% 15% 7% 5% 6% 4 4 5% 20%	4440
	21st to end	Night	18% 18% 7% 11% 6% 5% 4 3 4 4 21%	4752
February	1st to 10th	Night	16% 15% 6% 11% 7% 5% 4 4 5% 6% 22%	2470
	11th to 20th	Night	14% 14% 5% 12% 6% 4 4 3 5% 4 29%	2384
	21st to end	Night	16% 14% 4 11% 6% 3 4 4 4 5% 29%	1884
March	1st to 10th	Night	21% 12% 4 8% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	18% 17% 5% 9% 5% 4 3 3 5% 5% 27%	3485
	21st to end	Night	16% 10% 3 7% 5% 4 3 3 4 5% 40%	3599
April	1st to 10th	Night	20% 11% 3 7% 6% 5% 3 2 4 5% 33%	1900
	11th to 20th	Night	21% 9% 2 7% 4 4 4 3 3 5% 35%	1875
	21st to end	Night	22% 9% 3 8% 4 4 3 3 4 6% 33%	1804
May	1st to 10th	Night	22% 10% 3 6% 4 5% 5% 4 6% 7% 28%	2514
	11th to 20th	Night	20% 9% 3 6% 4 3 4 3 5% 6% 36%	2495
	21st to end	Night	14% 6% 2 5% 5% 4 5% 4 6% 8% 40%	2738
June	1st to 10th	Night	17% 8% 3 8% 5% 5% 6% 4 6% 8% 32%	1520
	11th to 20th	Night	15% 5% 3 6% 4 5% 3 4 7% 8% 40%	1520
	21st to end	Night	20% 7% 3 6% 4 4 4 3 6% 7% 35%	1520
July	1st to 10th	Night	11% 7% 3 9% 6% 5% 4 4 6% 8% 35%	2520
	11th to 20th	Night	13% 6% 3 6% 4 4 4 4 5% 8% 43%	2520
	21st to end	Night	10% 7% 3 6% 4 5% 5% 5% 6% 8% 42%	2739
August	1st to 10th	Night	13% 7% 3 7% 4 4 4 4 6% 8% 40%	2583
	11th to 20th	Night	13% 6% 3 7% 4 5% 4 4 5% 8% 40%	2835
	21st to end	Night	10% 6% 2 7% 4 5% 5% 4 6% 8% 41%	3476
September	1st to 10th	Night	13% 6% 2 6% 5% 4 4 3 4 6% 46%	1900
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 6% 6% 51%	1905
	21st to end	Night	16% 7% 2 7% 4 4 4 3 5% 7% 42%	2125
October	1st to 10th	Night	18% 7% 3 7% 5% 4 4 3 6% 7% 37%	2160
	11th to 20th	Night	21% 10% 3 7% 4 4 4 3 6% 6% 32%	2160
	21st to end	Night	25% 11% 2 7% 4 5% 4 4 5% 6% 27%	2520
November	1st to 10th	Night	20% 10% 3 6% 5% 4 4 2 4 6% 36%	2407
	11th to 20th	Night	18% 11% 3 7% 6% 5% 4 4 4 6% 32%	2628
	21st to end	Night	21% 14% 4 9% 5% 5% 4 3 5% 5% 24%	2660
December	1st to 10th	Night	21% 19% 4 10% 6% 5% 5% 3 4 5% 18%	2660
	11th to 20th	Night	23% 15% 4 9% 5% 4 3 3 3 4 27%	3288
	21st to end	Night	31% 16% 4 11% 5% 3 3 3 3 4 17%	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	62% 11% 13% 8% 5% 1	2518
	11th to 20th	Day	61% 9% 13% 10% 7% 1	2520
	21st to end	Day	69% 9% 10% 8% 4	2900
February	1st to 10th	Day	62% 6% 9% 18% 4 1	1710
	11th to 20th	Day	58% 7% 11% 16% 8% 1	1691
	21st to end	Day	61% 6% 10% 13% 8% 1	1570
March	1st to 10th	Day	57% 7% 10% 17% 8%	3119
	11th to 20th	Day	53% 9% 13% 14% 8% 2	3470
	21st to end	Day	41% 7% 9% 22% 17% 3	4033
April	1st to 10th	Day	53% 6% 8% 18% 13% 2	2280
	11th to 20th	Day	50% 6% 8% 19% 15% 2	2254
	21st to end	Day	54% 6% 9% 14% 14% 4	2391
May	1st to 10th	Day	49% 9% 11% 20% 9% 2	4440
	11th to 20th	Day	49% 9% 13% 19% 9% 1	4402
	21st to end	Day	40% 9% 13% 23% 14% 1	4837
June	1st to 10th	Day	52% 9% 11% 17% 11% 1	2660
	11th to 20th	Day	42% 8% 12% 23% 12% 2	2660
	21st to end	Day	50% 9% 11% 19% 10% 1	2660
July	1st to 10th	Day	41% 7% 13% 26% 12%	4370
	11th to 20th	Day	38% 9% 14% 30% 9%	4365
	21st to end	Day	37% 9% 13% 32% 10%	4661
August	1st to 10th	Day	47% 6% 14% 23% 9%	4328
	11th to 20th	Day	42% 7% 14% 28% 8%	4001
	21st to end	Day	40% 7% 16% 26% 11%	4180
September	1st to 10th	Day	38% 9% 15% 26% 12%	2280
	11th to 20th	Day	36% 6% 13% 31% 13%	2275
	21st to end	Day	42% 9% 14% 26% 9%	2019
October	1st to 10th	Day	50% 6% 12% 21% 11%	1800
	11th to 20th	Day	55% 9% 14% 16% 6% 1	1800
	21st to end	Day	59% 7% 11% 14% 8% 1	1835
November	1st to 10th	Day	48% 9% 15% 20% 7% 1	1671
	11th to 20th	Day	56% 8% 11% 15% 9% 1	1549
	21st to end	Day	62% 9% 12% 11% 5%	1520
December	1st to 10th	Day	69% 8% 12% 9% 2 1	1520
	11th to 20th	Day	63% 7% 14% 13% 3	1906
	21st to end	Day	71% 5% 7% 13% 3	2772
January	1st to 10th	Night	63% 9% 14% 10% 4	4429
	11th to 20th	Night	63% 11% 13% 9% 4	4440
	21st to end	Night	67% 7% 10% 10% 5% 1	4752
February	1st to 10th	Night	62% 6% 11% 14% 6% 1	2470
	11th to 20th	Night	57% 6% 11% 19% 7%	2386
	21st to end	Night	57% 6% 9% 18% 9% 1	1884
March	1st to 10th	Night	54% 6% 10% 20% 9% 1	3734
	11th to 20th	Night	56% 8% 14% 14% 7% 1	3486
	21st to end	Night	44% 5% 9% 22% 17% 3	3599
April	1st to 10th	Night	53% 5% 9% 19% 12% 2	1900
	11th to 20th	Night	50% 6% 8% 20% 15% 1	1875
	21st to end	Night	51% 6% 9% 16% 15% 3	1804
May	1st to 10th	Night	50% 11% 11% 17% 9% 3	2520
	11th to 20th	Night	45% 11% 13% 19% 11% 1	2496
	21st to end	Night	38% 10% 14% 20% 17% 2	2739
June	1st to 10th	Night	47% 9% 14% 18% 11% 1	1520
	11th to 20th	Night	40% 7% 14% 20% 17% 2	1520
	21st to end	Night	47% 8% 13% 18% 13% 1	1520
July	1st to 10th	Night	44% 7% 14% 20% 14% 1	2480
	11th to 20th	Night	38% 7% 14% 33% 8%	2472
	21st to end	Night	38% 9% 15% 22% 15%	2651
August	1st to 10th	Night	41% 8% 14% 25% 11%	2573
	11th to 20th	Night	41% 7% 16% 29% 7%	2862
	21st to end	Night	38% 8% 14% 27% 12% 1	3476
September	1st to 10th	Night	38% 8% 11% 28% 14% 1	1900
	11th to 20th	Night	32% 8% 15% 33% 12% 1	1905
	21st to end	Night	41% 7% 12% 28% 11% 1	2125
October	1st to 10th	Night	46% 8% 11% 21% 13% 1	2160
	11th to 20th	Night	51% 7% 13% 20% 8%	2160
	21st to end	Night	57% 7% 13% 14% 8% 1	2520
November	1st to 10th	Night	50% 6% 14% 20% 10% 1	2407
	11th to 20th	Night	54% 6% 12% 17% 9% 1	2628
	21st to end	Night	61% 7% 12% 15% 5%	2660
December	1st to 10th	Night	68% 7% 10% 12% 3	2660
	11th to 20th	Night	62% 5% 10% 15% 7% 1	3288
	21st to end	Night	72% 6% 8% 12% 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	25% 21% 32% 16% 5% 1	180
	11th to 20th	Day	33% 19% 31% 13% 4 1	180
	21st to end	Day	24% 19% 36% 15% 6%	234
February	1st to 10th	Day	32% 23% 31% 13% 1	270
	11th to 20th	Day	28% 23% 39% 10%	289
	21st to end	Day	30% 18% 35% 15% 2	382
March	1st to 10th	Day	26% 18% 35% 17% 5%	460
	11th to 20th	Day	25% 20% 35% 16% 3 1	460
	21st to end	Day	30% 22% 26% 16% 6% 1	506
April	1st to 10th	Day	32% 16% 31% 15% 5% 1	460
	11th to 20th	Day	32% 20% 23% 16% 7% 2	452
	21st to end	Day	31% 19% 29% 14% 6% 2	460
May	1st to 10th	Day	24% 18% 31% 18% 7% 2	463
	11th to 20th	Day	19% 18% 34% 19% 8% 2	487
	21st to end	Day	20% 16% 30% 23% 9% 1	529
June	1st to 10th	Day	25% 14% 30% 22% 8% 1	490
	11th to 20th	Day	16% 14% 35% 23% 10% 3	490
	21st to end	Day	22% 14% 32% 19% 10% 3	490
July	1st to 10th	Day	13% 8% 31% 31% 13% 2	485
	11th to 20th	Day	13% 10% 33% 28% 12% 3	484
	21st to end	Day	14% 7% 34% 31% 11% 3	532
August	1st to 10th	Day	15% 10% 28% 31% 14% 3	486
	11th to 20th	Day	16% 7% 25% 29% 15% 7%	479
	21st to end	Day	14% 12% 31% 24% 13% 7%	539
September	1st to 10th	Day	16% 13% 29% 23% 13% 7%	490
	11th to 20th	Day	13% 9% 25% 22% 18% 12%	490
	21st to end	Day	19% 11% 30% 21% 15% 4	483
October	1st to 10th	Day	25% 14% 26% 18% 12% 5%	450
	11th to 20th	Day	28% 17% 27% 22% 5% 1	450
	21st to end	Day	34% 14% 27% 21% 4	422
November	1st to 10th	Day	26% 20% 28% 20% 6% 1	365
	11th to 20th	Day	29% 19% 32% 13% 4 2	209
	21st to end	Day	27% 22% 33% 13% 4 1	180
December	1st to 10th	Day	34% 16% 36% 12% 3	180
	11th to 20th	Day	30% 28% 31% 8% 3 1	180
	21st to end	Day	34% 19% 29% 15% 2 1	198
January	1st to 10th	Night	26% 18% 32% 19% 4	760
	11th to 20th	Night	30% 18% 27% 20% 4 1	760
	21st to end	Night	21% 14% 35% 25% 5%	836
February	1st to 10th	Night	23% 19% 36% 20% 3	760
	11th to 20th	Night	22% 19% 37% 19% 3	743
	21st to end	Night	25% 20% 31% 22% 3	628
March	1st to 10th	Night	25% 14% 35% 22% 4	760
	11th to 20th	Night	24% 21% 30% 19% 5%	760
	21st to end	Night	24% 15% 30% 24% 7%	836
April	1st to 10th	Night	26% 15% 31% 25% 4	760
	11th to 20th	Night	26% 17% 30% 21% 7%	751
	21st to end	Night	26% 14% 29% 23% 7%	664
May	1st to 10th	Night	26% 8% 28% 27% 9% 2	380
	11th to 20th	Night	20% 11% 33% 28% 8%	374
	21st to end	Night	13% 11% 38% 26% 12%	411
June	1st to 10th	Night	17% 8% 33% 34% 7% 1	380
	11th to 20th	Night	15% 11% 30% 32% 11% 1	380
	21st to end	Night	19% 7% 34% 28% 12%	380
July	1st to 10th	Night	8% 9% 27% 44% 11% 1	370
	11th to 20th	Night	14% 5% 26% 39% 15% 1	368
	21st to end	Night	10% 4 32% 42% 11% 1	416
August	1st to 10th	Night	15% 5% 24% 40% 16%	416
	11th to 20th	Night	14% 4 21% 38% 22% 1	588
	21st to end	Night	14% 6% 29% 31% 18% 2	836
September	1st to 10th	Night	14% 8% 30% 31% 16% 1	760
	11th to 20th	Night	16% 6% 22% 29% 22% 4	760
	21st to end	Night	18% 9% 24% 28% 20% 1	756
October	1st to 10th	Night	22% 10% 29% 22% 15% 2	720
	11th to 20th	Night	25% 14% 29% 24% 8% 1	720
	21st to end	Night	30% 14% 28% 23% 5%	792
November	1st to 10th	Night	27% 14% 28% 22% 8%	740
	11th to 20th	Night	25% 19% 29% 18% 9%	760
	21st to end	Night	31% 16% 27% 21% 6%	760
December	1st to 10th	Night	31% 16% 30% 18% 4	760
	11th to 20th	Night	29% 18% 30% 18% 5% 1	760
	21st to end	Night	34% 16% 29% 18% 3	836

Page generated at 2024-09-26 09:52:24. Version ac07

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