Killarney Provincial Park Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Killarney Provincial Park Observatory clear sky chart from 2005-11-06 to 2024-11-06.

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% 4 4 3 5% 7% 36%	101595
	Night	15% 11% 4 8% 5% 4 4 4 5% 6% 33%	97527
Transparency	Day	27% 46% 7% 14% 6% 1	105109
	Night	27% 47% 7% 13% 6% 1	102102
Seeing	Day	21% 15% 32% 21% 8% 2	15294
	Night	22% 12% 29% 26% 10% 1	24454

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	17% 20% 9% 13% 5% 3 3 2 3 4 22%	2208
	11th to 20th	Day	10% 15% 7% 18% 9% 5% 5% 3 5% 5% 18%	2444
	21st to end	Day	17% 20% 8% 11% 7% 5% 4 3 5% 4 16%	3000
February	1st to 10th	Day	11% 17% 6% 10% 7% 5% 5% 4 5% 5% 26%	1710
	11th to 20th	Day	11% 15% 5% 10% 7% 5% 4 3 4 6% 30%	1663
	21st to end	Day	12% 17% 7% 12% 7% 4 4 3 3 6% 25%	1517
March	1st to 10th	Day	17% 14% 4 8% 4 4 4 4 6% 5% 31%	3296
	11th to 20th	Day	11% 14% 5% 11% 6% 5% 4 4 5% 6% 30%	3480
	21st to end	Day	13% 13% 5% 9% 5% 4 3 3 5% 6% 34%	3815
April	1st to 10th	Day	18% 12% 4 8% 4 4 4 4 4 7% 30%	2230
	11th to 20th	Day	20% 10% 2 7% 4 4 4 4 5% 5% 36%	2442
	21st to end	Day	22% 8% 2 6% 4 3 4 3 5% 7% 36%	2470
May	1st to 10th	Day	17% 7% 2 6% 5% 4 4 3 6% 7% 39%	4108
	11th to 20th	Day	13% 8% 3 7% 4 3 5% 4 5% 7% 42%	4332
	21st to end	Day	17% 6% 2 6% 4 3 3 3 5% 7% 44%	4961
June	1st to 10th	Day	16% 7% 3 6% 6% 4 5% 4 6% 8% 37%	2850
	11th to 20th	Day	12% 7% 2 6% 5% 4 4 4 5% 8% 42%	2850
	21st to end	Day	16% 7% 3 6% 5% 5% 5% 3 5% 8% 37%	2850
July	1st to 10th	Day	15% 8% 3 7% 4 4 4 4 6% 7% 39%	4760
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 8% 48%	4760
	21st to end	Day	11% 5% 2 5% 4 3 4 3 6% 8% 50%	4644
August	1st to 10th	Day	10% 6% 3 6% 4 4 5% 4 7% 9% 41%	4104
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 6% 9% 42%	4044
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 5% 8% 47%	4532
September	1st to 10th	Day	12% 6% 2 8% 6% 4 4 4 6% 6% 42%	2269
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 8% 46%	2090
	21st to end	Day	19% 7% 2 6% 5% 4 4 3 5% 7% 38%	2090
October	1st to 10th	Day	18% 6% 3 7% 5% 4 5% 4 5% 6% 38%	1929
	11th to 20th	Day	25% 9% 3 8% 5% 5% 5% 3 5% 6% 26%	1900
	21st to end	Day	26% 12% 3 8% 5% 4 3 3 5% 6% 25%	1967
November	1st to 10th	Day	18% 11% 4 8% 5% 5% 5% 4 6% 7% 29%	1641
	11th to 20th	Day	15% 17% 4 9% 5% 6% 4 4 6% 6% 25%	1520
	21st to end	Day	21% 20% 5% 10% 6% 4 3 3 4 5% 19%	1520
December	1st to 10th	Day	13% 23% 5% 10% 5% 4 3 4 6% 6% 21%	1497
	11th to 20th	Day	19% 15% 5% 9% 5% 5% 4 3 4 6% 25%	1671
	21st to end	Day	25% 23% 5% 9% 5% 4 3 3 3 4 16%	2431
January	1st to 10th	Night	14% 16% 7% 11% 6% 5% 5% 4 5% 6% 21%	4748
	11th to 20th	Night	13% 14% 5% 12% 6% 6% 5% 4 6% 6% 22%	4522
	21st to end	Night	15% 19% 7% 12% 5% 5% 5% 3 5% 5% 20%	4658
February	1st to 10th	Night	12% 14% 6% 11% 6% 4 5% 4 5% 5% 26%	2470
	11th to 20th	Night	11% 12% 5% 10% 6% 5% 5% 4 5% 5% 29%	2403
	21st to end	Night	12% 16% 5% 9% 6% 5% 5% 4 6% 5% 26%	1933
March	1st to 10th	Night	15% 10% 3 9% 5% 4 4 3 5% 5% 37%	3543
	11th to 20th	Night	9% 12% 5% 9% 6% 4 4 3 5% 6% 36%	3479
	21st to end	Night	13% 9% 6% 7% 6% 4 4 3 4 6% 37%	3817
April	1st to 10th	Night	19% 11% 3 7% 4 4 4 4 5% 6% 33%	1966
	11th to 20th	Night	19% 9% 2 6% 4 3 4 3 4 7% 38%	1687
	21st to end	Night	19% 9% 3 10% 5% 5% 3 3 4 6% 33%	1710
May	1st to 10th	Night	16% 7% 2 8% 5% 4 5% 4 5% 6% 38%	2833
	11th to 20th	Night	11% 6% 3 7% 4 5% 4 4 7% 9% 39%	2559
	21st to end	Night	12% 8% 3 7% 5% 4 4 3 4 7% 42%	2614
June	1st to 10th	Night	13% 8% 2 5% 5% 6% 5% 5% 8% 6% 37%	1330
	11th to 20th	Night	11% 6% 2 5% 6% 5% 5% 5% 5% 9% 42%	1330
	21st to end	Night	14% 5% 3 8% 5% 4 3 4 6% 8% 41%	1330
July	1st to 10th	Night	13% 7% 2 7% 4 3 3 4 5% 8% 45%	2210
	11th to 20th	Night	11% 4 2 4 4 4 4 4 5% 9% 49%	2210
	21st to end	Night	9% 4 2 6% 4 4 4 3 6% 7% 51%	2896
August	1st to 10th	Night	10% 6% 3 6% 4 4 4 5% 7% 8% 43%	2825
	11th to 20th	Night	14% 6% 2 5% 4 4 3 4 5% 7% 47%	2785
	21st to end	Night	10% 6% 2 5% 4 4 4 3 5% 7% 50%	3124
September	1st to 10th	Night	12% 5% 2 6% 5% 4 4 3 5% 6% 48%	1889
	11th to 20th	Night	12% 4 1 4 3 4 4 4 4 8% 51%	2090
	21st to end	Night	18% 7% 2 6% 4 4 3 3 5% 8% 41%	2090
October	1st to 10th	Night	19% 8% 2 6% 4 3 4 3 5% 6% 39%	2250
	11th to 20th	Night	23% 9% 3 7% 5% 4 4 4 6% 6% 30%	2280
	21st to end	Night	24% 11% 3 8% 5% 4 4 3 5% 6% 27%	2627
November	1st to 10th	Night	18% 11% 3 7% 4 3 4 3 5% 8% 32%	2558
	11th to 20th	Night	17% 13% 4 10% 7% 4 6% 4 5% 6% 25%	2660
	21st to end	Night	20% 18% 4 8% 5% 4 4 3 5% 6% 22%	2660
December	1st to 10th	Night	17% 19% 5% 10% 5% 5% 4 3 4 6% 21%	2679
	11th to 20th	Night	18% 16% 4 9% 5% 4 4 3 5% 6% 26%	3526
	21st to end	Night	25% 20% 6% 11% 5% 4 3 3 3 5% 16%	5236

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	43% 40% 6% 7% 4	2209
	11th to 20th	Day	45% 39% 8% 5% 2 1	2444
	21st to end	Day	47% 41% 4 5% 3	3000
February	1st to 10th	Day	22% 64% 4 8% 2	1710
	11th to 20th	Day	20% 63% 4 7% 5%	1672
	21st to end	Day	22% 64% 2 7% 5%	1517
March	1st to 10th	Day	35% 41% 8% 7% 8% 1	3299
	11th to 20th	Day	34% 41% 8% 12% 4 1	3480
	21st to end	Day	33% 40% 8% 10% 8% 2	3815
April	1st to 10th	Day	19% 64% 3 8% 5%	2230
	11th to 20th	Day	19% 64% 2 9% 4 1	2442
	21st to end	Day	18% 65% 3 8% 5% 1	2470
May	1st to 10th	Day	27% 42% 4 18% 7% 1	4120
	11th to 20th	Day	24% 41% 8% 20% 6% 1	4336
	21st to end	Day	27% 40% 7% 11% 14% 2	4961
June	1st to 10th	Day	15% 65% 4 9% 6% 1	2850
	11th to 20th	Day	15% 64% 4 9% 7% 1	2850
	21st to end	Day	17% 63% 4 10% 6% 1	2850
July	1st to 10th	Day	33% 36% 11% 14% 6% 1	4686
	11th to 20th	Day	21% 36% 10% 27% 6%	4679
	21st to end	Day	19% 35% 7% 23% 15%	4496
August	1st to 10th	Day	23% 38% 9% 22% 7% 1	4091
	11th to 20th	Day	27% 37% 11% 17% 7%	4083
	21st to end	Day	23% 37% 9% 23% 7%	4531
September	1st to 10th	Day	17% 61% 7% 11% 5%	2269
	11th to 20th	Day	12% 59% 6% 15% 8%	2090
	21st to end	Day	17% 60% 8% 11% 4	2090
October	1st to 10th	Day	24% 37% 5% 22% 13%	3202
	11th to 20th	Day	26% 37% 10% 21% 5%	3140
	21st to end	Day	40% 36% 8% 11% 4	3217
November	1st to 10th	Day	27% 56% 5% 8% 4	1641
	11th to 20th	Day	25% 59% 5% 7% 4	1520
	21st to end	Day	26% 59% 4 7% 3	1520
December	1st to 10th	Day	26% 60% 5% 6% 3	1497
	11th to 20th	Day	32% 49% 6% 9% 4 1	1671
	21st to end	Day	50% 37% 3 8% 3	2431
January	1st to 10th	Night	39% 41% 7% 7% 5%	4748
	11th to 20th	Night	37% 40% 11% 9% 2	4522
	21st to end	Night	45% 41% 4 7% 2	4658
February	1st to 10th	Night	20% 65% 3 9% 3	2470
	11th to 20th	Night	19% 64% 4 9% 5%	2405
	21st to end	Night	21% 65% 2 7% 5%	1933
March	1st to 10th	Night	31% 42% 6% 12% 9% 1	3553
	11th to 20th	Night	30% 40% 8% 14% 6% 2	3480
	21st to end	Night	30% 41% 5% 14% 9% 2	3817
April	1st to 10th	Night	21% 64% 2 7% 5%	1966
	11th to 20th	Night	17% 65% 2 8% 7% 1	1687
	21st to end	Night	19% 65% 3 7% 5% 1	1710
May	1st to 10th	Night	29% 41% 5% 16% 8%	2840
	11th to 20th	Night	24% 42% 5% 18% 11% 1	2560
	21st to end	Night	27% 41% 5% 16% 7% 4	2615
June	1st to 10th	Night	14% 65% 2 11% 6% 2	1330
	11th to 20th	Night	13% 65% 4 9% 8% 1	1330
	21st to end	Night	14% 63% 4 11% 8% 1	1330
July	1st to 10th	Night	28% 35% 10% 16% 9% 2	2175
	11th to 20th	Night	22% 35% 11% 26% 6%	2168
	21st to end	Night	20% 35% 7% 22% 17%	2805
August	1st to 10th	Night	24% 38% 10% 18% 10%	2814
	11th to 20th	Night	25% 38% 14% 17% 6%	2812
	21st to end	Night	20% 38% 8% 25% 9%	3124
September	1st to 10th	Night	15% 60% 7% 13% 5%	1889
	11th to 20th	Night	12% 59% 6% 15% 8%	2090
	21st to end	Night	17% 60% 6% 11% 6%	2090
October	1st to 10th	Night	23% 36% 6% 23% 11%	3757
	11th to 20th	Night	24% 37% 10% 22% 7%	3779
	21st to end	Night	32% 37% 15% 12% 5%	4327
November	1st to 10th	Night	24% 58% 6% 8% 4	2558
	11th to 20th	Night	24% 60% 5% 7% 4	2660
	21st to end	Night	26% 61% 3 5% 5%	2660
December	1st to 10th	Night	27% 60% 3 7% 3	2679
	11th to 20th	Night	31% 49% 5% 7% 6% 1	3525
	21st to end	Night	48% 37% 6% 6% 3	5236

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	23% 22% 30% 20% 4 1	180
	11th to 20th	Day	21% 16% 37% 20% 6%	248
	21st to end	Day	25% 15% 33% 19% 8% 1	297
February	1st to 10th	Day	26% 25% 31% 13% 5%	270
	11th to 20th	Day	24% 23% 37% 14% 1 1	270
	21st to end	Day	32% 26% 32% 9%	225
March	1st to 10th	Day	24% 25% 30% 16% 5%	371
	11th to 20th	Day	22% 17% 35% 20% 6% 1	460
	21st to end	Day	26% 18% 33% 18% 4 1	506
April	1st to 10th	Day	25% 17% 30% 20% 7% 1	460
	11th to 20th	Day	31% 19% 25% 15% 8% 3	452
	21st to end	Day	30% 17% 29% 15% 8% 1	460
May	1st to 10th	Day	20% 14% 37% 19% 7% 3	463
	11th to 20th	Day	20% 15% 31% 20% 12% 2	487
	21st to end	Day	18% 12% 34% 24% 9% 2	601
June	1st to 10th	Day	16% 16% 37% 25% 6% 1	680
	11th to 20th	Day	16% 16% 37% 22% 6% 2	680
	21st to end	Day	21% 14% 33% 23% 8% 2	680
July	1st to 10th	Day	10% 14% 35% 30% 10% 2	671
	11th to 20th	Day	12% 13% 34% 27% 11% 4	668
	21st to end	Day	12% 9% 34% 29% 11% 5%	628
August	1st to 10th	Day	16% 8% 27% 28% 15% 5%	486
	11th to 20th	Day	13% 6% 32% 27% 13% 9%	479
	21st to end	Day	16% 11% 29% 25% 13% 6%	539
September	1st to 10th	Day	16% 10% 31% 26% 11% 5%	490
	11th to 20th	Day	14% 8% 30% 30% 12% 6%	490
	21st to end	Day	25% 13% 24% 25% 11% 2	490
October	1st to 10th	Day	24% 14% 28% 21% 10% 3	490
	11th to 20th	Day	28% 16% 35% 16% 4 1	490
	21st to end	Day	34% 19% 30% 14% 2 1	416
November	1st to 10th	Day	29% 17% 37% 11% 4	249
	11th to 20th	Day	26% 24% 32% 14% 3 1	180
	21st to end	Day	33% 19% 28% 13% 6%	180
December	1st to 10th	Day	26% 16% 36% 16% 7%	180
	11th to 20th	Day	29% 22% 30% 17% 1 1	180
	21st to end	Day	32% 21% 34% 11% 3	198
January	1st to 10th	Night	23% 15% 32% 22% 6% 1	950
	11th to 20th	Night	26% 16% 28% 23% 7% 1	950
	21st to end	Night	21% 11% 30% 28% 9% 2	910
February	1st to 10th	Night	20% 16% 37% 23% 5%	760
	11th to 20th	Night	19% 16% 35% 24% 5% 1	743
	21st to end	Night	22% 18% 34% 22% 4	628
March	1st to 10th	Night	19% 18% 35% 23% 6%	760
	11th to 20th	Night	20% 15% 34% 22% 8% 1	760
	21st to end	Night	21% 12% 33% 27% 7% 1	836
April	1st to 10th	Night	25% 12% 33% 25% 5%	730
	11th to 20th	Night	24% 13% 26% 24% 10% 2	563
	21st to end	Night	24% 14% 26% 26% 11%	570
May	1st to 10th	Night	15% 9% 28% 36% 11% 1	570
	11th to 20th	Night	15% 8% 31% 34% 11% 1	412
	21st to end	Night	13% 9% 30% 34% 13%	411
June	1st to 10th	Night	17% 7% 33% 32% 10%	380
	11th to 20th	Night	14% 7% 28% 38% 12% 1	380
	21st to end	Night	17% 6% 29% 34% 13% 2	380
July	1st to 10th	Night	10% 6% 24% 47% 11% 1	370
	11th to 20th	Night	8% 4 27% 42% 19%	368
	21st to end	Night	11% 5% 22% 41% 20% 1	604
August	1st to 10th	Night	12% 4 24% 37% 22% 2	567
	11th to 20th	Night	15% 3 23% 32% 23% 4	564
	21st to end	Night	15% 7% 22% 30% 24% 2	627
September	1st to 10th	Night	16% 7% 27% 30% 18% 2	727
	11th to 20th	Night	14% 7% 26% 29% 20% 4	760
	21st to end	Night	21% 8% 26% 25% 16% 3	760
October	1st to 10th	Night	25% 10% 25% 27% 11% 2	760
	11th to 20th	Night	30% 14% 28% 21% 6% 1	760
	21st to end	Night	31% 15% 28% 21% 4 1	836
November	1st to 10th	Night	27% 13% 28% 24% 7%	764
	11th to 20th	Night	27% 17% 27% 23% 6%	760
	21st to end	Night	31% 16% 30% 18% 5%	760
December	1st to 10th	Night	27% 17% 31% 18% 6%	779
	11th to 20th	Night	28% 17% 33% 17% 4 1	950
	21st to end	Night	31% 16% 28% 20% 6%	1045

Page generated at 2024-11-03 13:19:01. Version ac07

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