Port Elgin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Elgin clear sky chart from 2005-11-06 to 2024-02-25.

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	18% 10% 4 7% 5% 3 4 4 5% 7% 31%	78347
	Night	19% 11% 4 7% 6% 3 4 4 5% 6% 31%	80967
Transparency	Day	36% 37% 9% 12% 5%	78042
	Night	37% 36% 9% 12% 5%	80807
Seeing	Day	25% 18% 33% 18% 5% 1	15981
	Night	25% 17% 32% 21% 5%	23648

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	14% 14% 4 9% 8% 4 6% 5% 4 5% 25%	2207
	11th to 20th	Day	13% 12% 5% 10% 6% 3 4 4 3 5% 34%	2481
	21st to end	Day	13% 10% 5% 12% 7% 3 4 5% 4 7% 30%	3124
February	1st to 10th	Day	17% 13% 4 9% 7% 3 4 5% 4 5% 30%	1710
	11th to 20th	Day	16% 15% 4 9% 7% 3 5% 4 4 5% 28%	1663
	21st to end	Day	11% 12% 6% 7% 5% 4 5% 4 6% 7% 32%	1372
March	1st to 10th	Day	16% 15% 6% 9% 6% 3 4 4 5% 5% 26%	1958
	11th to 20th	Day	14% 12% 6% 11% 7% 3 4 5% 5% 6% 29%	1980
	21st to end	Day	18% 16% 6% 8% 5% 3 4 3 3 4 29%	2178
April	1st to 10th	Day	22% 12% 5% 8% 6% 3 5% 4 4 5% 27%	2155
	11th to 20th	Day	20% 12% 3 5% 6% 3 4 5% 5% 7% 31%	2230
	21st to end	Day	22% 13% 3 6% 5% 3 5% 4 5% 6% 28%	2340
May	1st to 10th	Day	26% 10% 3 7% 5% 4 5% 5% 5% 5% 26%	2428
	11th to 20th	Day	23% 9% 3 5% 4 3 5% 4 5% 6% 34%	2478
	21st to end	Day	21% 9% 3 6% 5% 2 4 4 5% 7% 32%	2724
June	1st to 10th	Day	27% 9% 3 6% 6% 3 4 4 5% 7% 25%	2595
	11th to 20th	Day	20% 8% 3 7% 5% 3 5% 5% 5% 6% 32%	2700
	21st to end	Day	25% 8% 3 6% 5% 3 4 4 5% 7% 30%	2700
July	1st to 10th	Day	17% 6% 3 5% 4 4 5% 5% 6% 9% 35%	2700
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 5% 7% 9% 35%	2601
	21st to end	Day	16% 7% 4 7% 6% 3 5% 6% 7% 9% 30%	2716
August	1st to 10th	Day	16% 6% 2 5% 6% 3 5% 6% 6% 9% 37%	2327
	11th to 20th	Day	15% 6% 3 7% 6% 4 6% 6% 7% 9% 32%	2304
	21st to end	Day	13% 7% 2 6% 4 3 4 4 5% 9% 43%	2498
September	1st to 10th	Day	17% 6% 2 4 4 3 4 5% 6% 9% 41%	2160
	11th to 20th	Day	18% 7% 3 6% 5% 3 4 5% 5% 6% 38%	2091
	21st to end	Day	19% 6% 2 6% 4 2 4 4 5% 6% 41%	1923
October	1st to 10th	Day	19% 7% 3 5% 5% 3 5% 4 5% 7% 36%	1800
	11th to 20th	Day	19% 10% 3 7% 5% 3 5% 4 5% 7% 32%	1800
	21st to end	Day	21% 10% 4 6% 6% 3 5% 4 4 7% 29%	1972
November	1st to 10th	Day	20% 13% 4 8% 6% 4 3 4 4 5% 29%	1485
	11th to 20th	Day	19% 13% 3 6% 6% 3 5% 4 4 6% 30%	1520
	21st to end	Day	17% 14% 6% 7% 6% 3 5% 4 5% 5% 28%	1520
December	1st to 10th	Day	23% 15% 5% 6% 6% 3 4 4 5% 7% 23%	1520
	11th to 20th	Day	19% 17% 7% 10% 5% 3 5% 3 3 5% 23%	1906
	21st to end	Day	19% 14% 9% 13% 5% 3 4 3 3 4 22%	2481
January	1st to 10th	Night	14% 11% 4 7% 6% 4 5% 5% 5% 6% 34%	4748
	11th to 20th	Night	17% 12% 6% 8% 6% 3 5% 4 4 5% 30%	4480
	21st to end	Night	14% 12% 5% 9% 9% 3 4 4 4 6% 30%	4532
February	1st to 10th	Night	18% 13% 4 8% 6% 3 5% 4 5% 6% 28%	2470
	11th to 20th	Night	17% 15% 4 9% 7% 4 4 4 4 5% 27%	2403
	21st to end	Night	13% 13% 5% 8% 5% 3 5% 4 5% 5% 33%	1978
March	1st to 10th	Night	17% 16% 5% 8% 7% 3 5% 4 4 5% 28%	1985
	11th to 20th	Night	17% 12% 5% 9% 7% 4 4 4 4 5% 30%	1979
	21st to end	Night	20% 13% 5% 9% 5% 2 4 3 3 5% 31%	2178
April	1st to 10th	Night	24% 12% 3 7% 7% 3 5% 5% 4 4 26%	1805
	11th to 20th	Night	21% 12% 3 6% 5% 2 4 2 4 5% 33%	1679
	21st to end	Night	22% 14% 5% 7% 4 3 4 4 4 5% 27%	1620
May	1st to 10th	Night	26% 9% 3 5% 6% 3 3 5% 5% 6% 29%	1530
	11th to 20th	Night	21% 11% 2 6% 5% 3 4 3 4 7% 34%	1416
	21st to end	Night	17% 8% 4 6% 5% 3 5% 5% 5% 8% 34%	1550
June	1st to 10th	Night	27% 8% 3 5% 7% 3 5% 3 6% 8% 26%	1379
	11th to 20th	Night	21% 8% 3 5% 5% 3 5% 4 4 7% 35%	1260
	21st to end	Night	23% 10% 3 6% 6% 3 4 5% 4 7% 30%	1260
July	1st to 10th	Night	17% 7% 3 5% 5% 4 5% 4 7% 8% 34%	1260
	11th to 20th	Night	14% 7% 3 6% 6% 3 6% 6% 7% 11% 31%	1340
	21st to end	Night	15% 8% 3 7% 7% 4 5% 5% 5% 8% 32%	1599
August	1st to 10th	Night	14% 6% 2 5% 6% 4 4 7% 7% 8% 38%	1612
	11th to 20th	Night	13% 9% 4 7% 6% 4 5% 6% 5% 8% 33%	1596
	21st to end	Night	15% 6% 2 4 5% 3 4 5% 6% 10% 41%	1858
September	1st to 10th	Night	15% 6% 3 6% 4 3 4 4 5% 8% 43%	1800
	11th to 20th	Night	17% 6% 2 6% 5% 3 5% 3 4 6% 43%	1866
	21st to end	Night	18% 6% 2 5% 4 4 4 4 4 7% 42%	2036
October	1st to 10th	Night	19% 7% 3 6% 5% 3 3 4 5% 6% 39%	2160
	11th to 20th	Night	18% 6% 4 6% 6% 3 5% 5% 6% 7% 36%	2160
	21st to end	Night	27% 10% 3 6% 6% 3 4 4 4 6% 29%	2383
November	1st to 10th	Night	22% 13% 4 7% 5% 3 4 4 4 6% 29%	2591
	11th to 20th	Night	20% 12% 3 7% 6% 4 5% 4 5% 6% 29%	2660
	21st to end	Night	22% 12% 4 6% 5% 4 5% 5% 5% 6% 26%	2660
December	1st to 10th	Night	24% 13% 5% 7% 6% 3 5% 4 5% 6% 23%	2660
	11th to 20th	Night	24% 16% 6% 8% 6% 3 3 3 3 4 23%	3293
	21st to end	Night	25% 14% 5% 10% 5% 2 3 4 4 5% 24%	5181

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	44% 30% 14% 10% 2	2208
	11th to 20th	Day	39% 28% 7% 16% 10% 1	2481
	21st to end	Day	42% 26% 11% 10% 10%	3124
February	1st to 10th	Day	40% 35% 9% 9% 7%	1710
	11th to 20th	Day	40% 37% 7% 10% 5% 1	1671
	21st to end	Day	37% 36% 9% 12% 6% 1	1372
March	1st to 10th	Day	42% 37% 6% 11% 3	1962
	11th to 20th	Day	35% 38% 8% 13% 4 1	1980
	21st to end	Day	39% 37% 6% 11% 5% 1	2178
April	1st to 10th	Day	40% 36% 6% 11% 5% 1	2155
	11th to 20th	Day	35% 37% 7% 12% 9% 1	2230
	21st to end	Day	34% 39% 8% 12% 6% 1	2340
May	1st to 10th	Day	39% 37% 7% 10% 6% 1	2428
	11th to 20th	Day	34% 38% 7% 15% 7%	2482
	21st to end	Day	31% 40% 9% 14% 5%	2724
June	1st to 10th	Day	40% 39% 8% 10% 3	2595
	11th to 20th	Day	34% 38% 8% 13% 6% 1	2700
	21st to end	Day	38% 40% 8% 10% 3 1	2700
July	1st to 10th	Day	31% 40% 9% 15% 5%	2625
	11th to 20th	Day	30% 41% 12% 12% 5%	2520
	21st to end	Day	32% 42% 10% 13% 2	2564
August	1st to 10th	Day	31% 40% 10% 15% 4	2314
	11th to 20th	Day	30% 40% 11% 15% 4	2304
	21st to end	Day	25% 38% 12% 18% 7%	2498
September	1st to 10th	Day	29% 38% 11% 15% 7%	2160
	11th to 20th	Day	30% 38% 8% 16% 8% 1	2091
	21st to end	Day	30% 37% 6% 19% 7%	1923
October	1st to 10th	Day	30% 38% 10% 17% 6%	1800
	11th to 20th	Day	35% 39% 10% 14% 3	1800
	21st to end	Day	36% 39% 8% 10% 5%	1972
November	1st to 10th	Day	34% 42% 7% 12% 5%	1485
	11th to 20th	Day	32% 42% 11% 10% 5%	1520
	21st to end	Day	36% 42% 10% 9% 3	1520
December	1st to 10th	Day	38% 43% 9% 8% 2	1520
	11th to 20th	Day	47% 35% 8% 7% 3	1905
	21st to end	Day	50% 29% 12% 7% 2	2481
January	1st to 10th	Night	37% 29% 15% 17% 2	4748
	11th to 20th	Night	40% 30% 9% 16% 6%	4480
	21st to end	Night	44% 25% 10% 15% 5% 1	4532
February	1st to 10th	Night	39% 36% 7% 9% 7% 1	2470
	11th to 20th	Night	39% 37% 7% 9% 7% 1	2406
	21st to end	Night	37% 37% 6% 13% 7% 1	1978
March	1st to 10th	Night	42% 38% 6% 9% 6% 1	1994
	11th to 20th	Night	37% 38% 7% 13% 4 1	1980
	21st to end	Night	37% 37% 7% 12% 6% 1	2178
April	1st to 10th	Night	41% 38% 6% 7% 7% 1	1805
	11th to 20th	Night	36% 35% 7% 13% 9%	1679
	21st to end	Night	36% 38% 8% 10% 8% 1	1620
May	1st to 10th	Night	37% 38% 7% 11% 6% 1	1530
	11th to 20th	Night	34% 38% 7% 14% 6% 1	1417
	21st to end	Night	31% 39% 10% 14% 5%	1551
June	1st to 10th	Night	41% 39% 6% 10% 4	1379
	11th to 20th	Night	34% 38% 7% 14% 7% 1	1260
	21st to end	Night	39% 39% 10% 8% 4	1260
July	1st to 10th	Night	30% 41% 11% 15% 4	1225
	11th to 20th	Night	31% 42% 9% 12% 5%	1298
	21st to end	Night	33% 41% 10% 10% 5%	1511
August	1st to 10th	Night	28% 40% 12% 15% 5%	1600
	11th to 20th	Night	31% 40% 13% 14% 2	1596
	21st to end	Night	27% 39% 13% 16% 5%	1858
September	1st to 10th	Night	28% 39% 9% 19% 6%	1800
	11th to 20th	Night	29% 37% 9% 16% 8% 1	1866
	21st to end	Night	29% 38% 8% 16% 9% 1	2036
October	1st to 10th	Night	29% 38% 10% 17% 7%	2160
	11th to 20th	Night	31% 38% 12% 15% 3	2160
	21st to end	Night	38% 39% 8% 9% 6%	2383
November	1st to 10th	Night	33% 43% 7% 11% 5%	2591
	11th to 20th	Night	33% 43% 9% 9% 5%	2660
	21st to end	Night	33% 43% 11% 10% 2	2660
December	1st to 10th	Night	37% 42% 9% 8% 3	2660
	11th to 20th	Night	47% 33% 6% 10% 3	3295
	21st to end	Night	50% 28% 12% 8% 3	5181

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	30% 24% 32% 12% 1	180
	11th to 20th	Day	28% 24% 30% 14% 4	337
	21st to end	Day	20% 20% 39% 17% 3 1	407
February	1st to 10th	Day	26% 23% 32% 14% 4 1	370
	11th to 20th	Day	27% 27% 30% 11% 3 1	366
	21st to end	Day	21% 21% 36% 18% 4	292
March	1st to 10th	Day	26% 24% 36% 10% 3 1	412
	11th to 20th	Day	22% 25% 34% 15% 4	420
	21st to end	Day	28% 25% 31% 12% 3 1	462
April	1st to 10th	Day	33% 28% 28% 9% 2	420
	11th to 20th	Day	30% 24% 31% 12% 4	412
	21st to end	Day	28% 23% 28% 15% 5% 1	420
May	1st to 10th	Day	33% 19% 29% 14% 5% 1	511
	11th to 20th	Day	29% 17% 29% 18% 6% 1	624
	21st to end	Day	27% 17% 36% 18% 3	680
June	1st to 10th	Day	33% 15% 31% 15% 5%	630
	11th to 20th	Day	26% 13% 34% 21% 5% 1	630
	21st to end	Day	27% 11% 31% 23% 7% 1	630
July	1st to 10th	Day	22% 12% 39% 19% 6% 1	620
	11th to 20th	Day	18% 8% 37% 27% 9% 1	618
	21st to end	Day	20% 10% 39% 24% 7%	656
August	1st to 10th	Day	14% 10% 38% 30% 7%	446
	11th to 20th	Day	18% 10% 35% 25% 11% 1	439
	21st to end	Day	16% 15% 32% 27% 8% 3	495
September	1st to 10th	Day	16% 12% 43% 19% 9% 1	450
	11th to 20th	Day	23% 18% 29% 21% 7% 2	450
	21st to end	Day	22% 16% 31% 20% 9% 2	421
October	1st to 10th	Day	23% 16% 30% 19% 10% 2	360
	11th to 20th	Day	22% 21% 29% 20% 7% 1	360
	21st to end	Day	26% 23% 29% 17% 4 1	396
November	1st to 10th	Day	27% 23% 30% 14% 6% 1	365
	11th to 20th	Day	26% 26% 29% 14% 4 1	370
	21st to end	Day	29% 27% 29% 12% 2	370
December	1st to 10th	Day	32% 21% 30% 14% 3	370
	11th to 20th	Day	29% 31% 28% 11% 1	370
	21st to end	Day	25% 25% 34% 13% 3	222
January	1st to 10th	Night	26% 20% 32% 17% 4	850
	11th to 20th	Night	26% 22% 30% 18% 4	844
	21st to end	Night	20% 20% 36% 18% 5%	836
February	1st to 10th	Night	27% 18% 33% 19% 2	760
	11th to 20th	Night	26% 24% 33% 14% 3 1	743
	21st to end	Night	21% 18% 36% 20% 4 1	611
March	1st to 10th	Night	26% 18% 36% 17% 3	720
	11th to 20th	Night	23% 20% 30% 21% 5% 1	720
	21st to end	Night	25% 19% 32% 18% 6%	792
April	1st to 10th	Night	31% 18% 30% 18% 2	545
	11th to 20th	Night	30% 16% 29% 19% 5% 1	534
	21st to end	Night	30% 15% 30% 19% 6% 1	540
May	1st to 10th	Night	30% 14% 28% 22% 6% 1	540
	11th to 20th	Night	26% 14% 29% 26% 5%	532
	21st to end	Night	22% 14% 42% 20% 2	583
June	1st to 10th	Night	32% 10% 32% 23% 4	479
	11th to 20th	Night	26% 8% 36% 26% 5%	360
	21st to end	Night	23% 9% 32% 29% 6% 1	360
July	1st to 10th	Night	19% 7% 43% 24% 7%	350
	11th to 20th	Night	16% 9% 40% 30% 5%	428
	21st to end	Night	19% 8% 36% 31% 6%	590
August	1st to 10th	Night	15% 6% 39% 30% 9%	538
	11th to 20th	Night	16% 9% 35% 31% 8% 1	532
	21st to end	Night	17% 9% 31% 32% 11%	594
September	1st to 10th	Night	19% 9% 37% 26% 8%	540
	11th to 20th	Night	20% 12% 28% 31% 8% 1	606
	21st to end	Night	22% 14% 31% 24% 9%	720
October	1st to 10th	Night	22% 12% 29% 26% 10%	720
	11th to 20th	Night	20% 15% 35% 21% 8% 1	720
	21st to end	Night	30% 21% 30% 17% 3	796
November	1st to 10th	Night	28% 20% 28% 18% 5%	830
	11th to 20th	Night	25% 24% 27% 18% 5% 1	850
	21st to end	Night	29% 22% 29% 17% 3	850
December	1st to 10th	Night	31% 20% 29% 17% 3	850
	11th to 20th	Night	28% 25% 32% 12% 2	850
	21st to end	Night	30% 23% 26% 17% 3 1	935

Page generated at 2024-02-22 07:05:43. Version ac07

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