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 2024-04-10.

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	16% 12% 5% 9% 6% 3 4 4 5% 6% 30%	82959
	Night	16% 14% 7% 11% 7% 3 4 4 4 5% 25%	85820
Transparency	Day	56% 5% 11% 18% 9% 1	82665
	Night	62% 4 11% 15% 7% 1	85648
Seeing	Day	19% 10% 28% 26% 13% 4	14322
	Night	22% 10% 27% 28% 12% 1	23785

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% 25% 13% 15% 10% 4 4 2 2 3 7%	2275
	11th to 20th	Day	11% 22% 10% 20% 19% 3 4 2 2 2 4	2591
	21st to end	Day	18% 22% 11% 16% 8% 4 5% 3 3 3 7%	3124
February	1st to 10th	Day	14% 18% 8% 18% 10% 5% 5% 3 4 4 11%	1710
	11th to 20th	Day	13% 13% 10% 18% 11% 4 5% 5% 4 4 14%	1663
	21st to end	Day	15% 18% 6% 12% 9% 4 5% 4 5% 5% 19%	1546
March	1st to 10th	Day	17% 15% 5% 8% 7% 4 4 4 3 5% 28%	3324
	11th to 20th	Day	12% 16% 9% 11% 6% 3 5% 5% 4 5% 24%	3480
	21st to end	Day	15% 12% 6% 8% 7% 4 4 5% 5% 6% 29%	3815
April	1st to 10th	Day	18% 12% 6% 8% 5% 3 4 4 5% 6% 29%	2176
	11th to 20th	Day	18% 10% 4 5% 5% 2 4 3 5% 7% 37%	2312
	21st to end	Day	19% 9% 4 5% 6% 3 4 5% 5% 6% 34%	2340
May	1st to 10th	Day	18% 8% 3 6% 5% 3 4 3 6% 7% 38%	2340
	11th to 20th	Day	16% 8% 3 5% 5% 3 4 4 5% 5% 43%	2367
	21st to end	Day	12% 5% 2 5% 4 3 4 4 6% 8% 47%	2725
June	1st to 10th	Day	14% 6% 2 5% 4 3 5% 5% 6% 8% 42%	2651
	11th to 20th	Day	11% 5% 2 5% 5% 3 5% 4 5% 9% 45%	2700
	21st to end	Day	13% 7% 2 5% 5% 3 4 4 5% 8% 44%	2700
July	1st to 10th	Day	9% 4 2 3 4 3 4 5% 6% 9% 51%	2700
	11th to 20th	Day	11% 5% 2 5% 5% 2 4 5% 6% 9% 46%	2617
	21st to end	Day	11% 5% 2 5% 5% 3 4 5% 6% 10% 45%	2547
August	1st to 10th	Day	12% 4 2 5% 4 2 5% 5% 6% 9% 47%	2327
	11th to 20th	Day	11% 5% 2 6% 5% 4 3 5% 6% 8% 44%	2303
	21st to end	Day	14% 5% 2 5% 5% 3 4 5% 5% 9% 42%	2566
September	1st to 10th	Day	13% 6% 2 6% 6% 3 5% 5% 6% 9% 39%	2120
	11th to 20th	Day	14% 5% 2 5% 5% 3 5% 4 6% 8% 43%	1980
	21st to end	Day	17% 8% 3 6% 5% 3 6% 5% 6% 6% 35%	1980
October	1st to 10th	Day	21% 8% 3 7% 6% 3 4 5% 5% 6% 32%	1836
	11th to 20th	Day	27% 15% 4 8% 6% 4 5% 4 4 6% 19%	1800
	21st to end	Day	30% 16% 5% 8% 7% 3 3 3 4 4 17%	1904
November	1st to 10th	Day	17% 19% 5% 9% 7% 4 4 4 5% 5% 22%	1656
	11th to 20th	Day	18% 21% 7% 10% 6% 4 4 5% 4 6% 16%	1520
	21st to end	Day	21% 24% 11% 12% 4 3 5% 3 4 5% 10%	1520
December	1st to 10th	Day	18% 27% 13% 16% 7% 3 3 3 2 2 5%	1520
	11th to 20th	Day	19% 24% 10% 17% 7% 3 4 3 3 4 7%	1793
	21st to end	Day	26% 25% 9% 11% 7% 3 3 3 3 3 7%	2431
January	1st to 10th	Night	16% 25% 13% 17% 9% 3 3 2 3 3 5%	4680
	11th to 20th	Night	14% 17% 10% 21% 15% 5% 4 3 2 3 5%	4374
	21st to end	Night	17% 21% 11% 14% 10% 4 5% 3 4 4 8%	4532
February	1st to 10th	Night	13% 19% 9% 17% 11% 4 5% 4 4 3 11%	2470
	11th to 20th	Night	14% 15% 10% 16% 9% 3 5% 4 4 4 16%	2403
	21st to end	Night	15% 14% 7% 13% 9% 3 5% 4 5% 6% 20%	1903
March	1st to 10th	Night	13% 13% 6% 9% 6% 3 4 3 4 7% 33%	3515
	11th to 20th	Night	11% 15% 7% 9% 6% 3 4 4 4 5% 32%	3479
	21st to end	Night	15% 10% 7% 12% 6% 4 4 4 4 5% 29%	3817
April	1st to 10th	Night	20% 12% 6% 8% 5% 3 4 4 4 6% 29%	2007
	11th to 20th	Night	18% 9% 3 6% 4 3 4 4 4 7% 38%	1597
	21st to end	Night	20% 9% 5% 7% 6% 2 4 4 5% 6% 31%	1620
May	1st to 10th	Night	16% 8% 3 6% 6% 4 4 4 4 8% 37%	1620
	11th to 20th	Night	16% 6% 3 6% 5% 3 5% 4 4 7% 42%	1523
	21st to end	Night	10% 4 3 5% 6% 3 5% 5% 5% 7% 47%	1550
June	1st to 10th	Night	15% 6% 3 6% 5% 3 4 5% 5% 8% 40%	1305
	11th to 20th	Night	11% 6% 2 4 4 3 5% 5% 7% 11% 41%	1260
	21st to end	Night	14% 5% 2 5% 5% 3 5% 5% 5% 8% 42%	1260
July	1st to 10th	Night	9% 4 2 3 4 3 3 4 5% 9% 55%	1260
	11th to 20th	Night	8% 5% 3 5% 5% 3 5% 5% 7% 10% 45%	1336
	21st to end	Night	8% 6% 2 5% 5% 4 4 5% 6% 7% 49%	1771
August	1st to 10th	Night	11% 5% 2 6% 4 3 4 4 6% 7% 47%	1611
	11th to 20th	Night	10% 4 2 6% 3 3 4 4 6% 8% 48%	1598
	21st to end	Night	12% 7% 2 6% 6% 3 4 4 5% 8% 43%	1782
September	1st to 10th	Night	11% 4 2 6% 5% 3 4 5% 6% 9% 46%	1825
	11th to 20th	Night	13% 5% 3 5% 4 3 4 4 5% 7% 47%	1980
	21st to end	Night	17% 8% 3 6% 6% 4 5% 4 5% 6% 37%	1980
October	1st to 10th	Night	20% 8% 3 6% 6% 3 3 5% 5% 5% 34%	2124
	11th to 20th	Night	26% 13% 4 9% 6% 3 4 4 5% 5% 21%	2160
	21st to end	Night	29% 15% 4 9% 6% 3 4 4 4 5% 17%	2451
November	1st to 10th	Night	19% 17% 4 7% 6% 3 4 5% 4 6% 24%	2420
	11th to 20th	Night	19% 20% 6% 10% 7% 3 5% 4 5% 4 17%	2660
	21st to end	Night	23% 23% 9% 10% 6% 3 3 3 4 4 13%	2660
December	1st to 10th	Night	20% 27% 12% 14% 6% 2 4 3 3 2 6%	2660
	11th to 20th	Night	15% 24% 11% 16% 7% 3 4 4 4 3 10%	3391
	21st to end	Night	24% 23% 10% 14% 8% 3 3 3 3 3 7%	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	84% 1 9% 5%	2276
	11th to 20th	Day	89% 2 4 4 1	2591
	21st to end	Day	85% 2 8% 4 1	3124
February	1st to 10th	Day	78% 3 9% 9% 1	1710
	11th to 20th	Day	74% 5% 8% 8% 4	1672
	21st to end	Day	69% 3 10% 13% 5%	1546
March	1st to 10th	Day	60% 4 12% 16% 7% 1	3327
	11th to 20th	Day	61% 5% 10% 16% 6% 1	3480
	21st to end	Day	54% 6% 12% 17% 10% 1	3815
April	1st to 10th	Day	56% 5% 10% 19% 10%	2176
	11th to 20th	Day	48% 5% 8% 23% 15% 1	2312
	21st to end	Day	50% 5% 12% 20% 11% 3	2340
May	1st to 10th	Day	46% 5% 8% 25% 14% 2	2340
	11th to 20th	Day	44% 5% 9% 25% 15% 2	2371
	21st to end	Day	37% 5% 15% 25% 15% 3	2725
June	1st to 10th	Day	40% 5% 12% 25% 16% 1	2651
	11th to 20th	Day	36% 5% 12% 27% 18% 1	2700
	21st to end	Day	39% 5% 14% 25% 15% 1	2700
July	1st to 10th	Day	30% 6% 15% 26% 20% 2	2626
	11th to 20th	Day	34% 6% 15% 31% 13% 2	2536
	21st to end	Day	36% 7% 13% 27% 15% 2	2405
August	1st to 10th	Day	34% 6% 17% 27% 14% 2	2314
	11th to 20th	Day	38% 7% 14% 27% 13%	2303
	21st to end	Day	38% 7% 14% 26% 13% 1	2566
September	1st to 10th	Day	41% 7% 13% 26% 12% 2	2120
	11th to 20th	Day	38% 5% 16% 29% 11%	1980
	21st to end	Day	48% 5% 14% 25% 8% 1	1980
October	1st to 10th	Day	53% 4 12% 20% 10% 1	1836
	11th to 20th	Day	67% 4 10% 14% 5% 1	1800
	21st to end	Day	73% 3 9% 12% 4	1904
November	1st to 10th	Day	64% 4 10% 16% 6%	1656
	11th to 20th	Day	70% 5% 11% 9% 5% 1	1520
	21st to end	Day	79% 3 10% 7% 1	1520
December	1st to 10th	Day	87% 2 6% 4 1	1520
	11th to 20th	Day	83% 3 8% 5% 1	1792
	21st to end	Day	85% 2 10% 3	2431
January	1st to 10th	Night	87% 2 7% 4	4680
	11th to 20th	Night	86% 2 8% 3 1	4374
	21st to end	Night	83% 2 9% 4 1	4532
February	1st to 10th	Night	79% 3 7% 10% 1	2470
	11th to 20th	Night	72% 4 10% 11% 4	2405
	21st to end	Night	65% 4 12% 12% 7%	1903
March	1st to 10th	Night	53% 3 15% 20% 7%	3525
	11th to 20th	Night	54% 3 14% 18% 9% 1	3480
	21st to end	Night	57% 4 10% 19% 9% 1	3817
April	1st to 10th	Night	58% 3 8% 19% 11% 1	2007
	11th to 20th	Night	47% 5% 8% 21% 19% 2	1597
	21st to end	Night	54% 4 8% 18% 14% 2	1620
May	1st to 10th	Night	47% 5% 9% 22% 15% 3	1620
	11th to 20th	Night	43% 3 7% 24% 19% 4	1524
	21st to end	Night	36% 5% 14% 26% 15% 4	1551
June	1st to 10th	Night	42% 4 10% 23% 18% 3	1305
	11th to 20th	Night	36% 5% 14% 25% 18% 2	1260
	21st to end	Night	39% 5% 13% 24% 17% 2	1260
July	1st to 10th	Night	28% 4 12% 27% 25% 4	1225
	11th to 20th	Night	33% 6% 14% 30% 16% 2	1294
	21st to end	Night	34% 5% 16% 27% 16% 2	1672
August	1st to 10th	Night	37% 4 15% 29% 14% 2	1600
	11th to 20th	Night	33% 5% 17% 29% 15% 2	1598
	21st to end	Night	41% 5% 13% 29% 12% 1	1782
September	1st to 10th	Night	35% 6% 13% 30% 14% 2	1825
	11th to 20th	Night	37% 3 15% 30% 14%	1980
	21st to end	Night	49% 4 13% 25% 9% 1	1980
October	1st to 10th	Night	50% 5% 13% 20% 12% 1	2124
	11th to 20th	Night	63% 4 13% 15% 5%	2160
	21st to end	Night	70% 3 10% 12% 4	2451
November	1st to 10th	Night	60% 4 11% 19% 5%	2420
	11th to 20th	Night	70% 3 12% 11% 3 1	2660
	21st to end	Night	76% 4 12% 7% 1	2660
December	1st to 10th	Night	86% 3 6% 4 1	2660
	11th to 20th	Night	80% 4 11% 5% 1	3391
	21st to end	Night	86% 2 9% 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	21% 18% 37% 15% 9% 1	200
	11th to 20th	Day	19% 18% 40% 15% 7% 1	270
	21st to end	Day	25% 10% 32% 27% 5%	297
February	1st to 10th	Day	23% 23% 35% 13% 6%	270
	11th to 20th	Day	20% 16% 45% 16% 3	270
	21st to end	Day	21% 30% 33% 12% 3	225
March	1st to 10th	Day	22% 15% 38% 18% 6% 1	386
	11th to 20th	Day	20% 15% 33% 26% 6% 1	460
	21st to end	Day	26% 9% 33% 24% 7% 1	506
April	1st to 10th	Day	23% 14% 33% 21% 9% 1	457
	11th to 20th	Day	27% 13% 27% 17% 9% 6%	412
	21st to end	Day	26% 8% 28% 26% 10% 2	420
May	1st to 10th	Day	22% 7% 30% 27% 11% 3	423
	11th to 20th	Day	20% 6% 27% 26% 17% 4	447
	21st to end	Day	14% 6% 25% 31% 17% 7%	485
June	1st to 10th	Day	14% 7% 28% 33% 15% 2	581
	11th to 20th	Day	13% 7% 28% 32% 17% 3	630
	21st to end	Day	15% 6% 29% 33% 14% 3	630
July	1st to 10th	Day	10% 4 24% 34% 23% 6%	621
	11th to 20th	Day	13% 4 25% 33% 18% 7%	615
	21st to end	Day	13% 4 22% 37% 18% 6%	488
August	1st to 10th	Day	12% 4 19% 34% 20% 10%	446
	11th to 20th	Day	14% 4 13% 33% 23% 13%	439
	21st to end	Day	17% 5% 19% 31% 21% 8%	495
September	1st to 10th	Day	14% 6% 20% 34% 19% 9%	450
	11th to 20th	Day	11% 6% 20% 28% 25% 10%	450
	21st to end	Day	15% 8% 26% 27% 17% 7%	450
October	1st to 10th	Day	22% 9% 26% 24% 14% 6%	450
	11th to 20th	Day	28% 15% 30% 20% 6% 2	450
	21st to end	Day	35% 13% 30% 17% 5%	419
November	1st to 10th	Day	24% 19% 29% 21% 6% 1	262
	11th to 20th	Day	27% 18% 31% 18% 4 3	180
	21st to end	Day	28% 19% 36% 16% 2	180
December	1st to 10th	Day	29% 16% 35% 16% 3 1	180
	11th to 20th	Day	29% 20% 30% 16% 4 1	180
	21st to end	Day	38% 16% 33% 11% 3	198
January	1st to 10th	Night	25% 17% 32% 19% 6% 1	950
	11th to 20th	Night	27% 15% 32% 20% 5% 1	910
	21st to end	Night	21% 10% 34% 27% 7% 1	836
February	1st to 10th	Night	22% 15% 35% 23% 5%	760
	11th to 20th	Night	21% 12% 35% 26% 5% 1	743
	21st to end	Night	22% 15% 36% 23% 4	628
March	1st to 10th	Night	18% 12% 37% 26% 7%	760
	11th to 20th	Night	19% 14% 36% 25% 6% 1	760
	21st to end	Night	22% 10% 28% 29% 10% 1	836
April	1st to 10th	Night	24% 10% 31% 28% 7%	757
	11th to 20th	Night	22% 9% 26% 30% 11% 2	533
	21st to end	Night	26% 7% 21% 32% 12% 1	540
May	1st to 10th	Night	21% 4 23% 36% 14% 2	540
	11th to 20th	Night	20% 5% 19% 40% 15% 2	462
	21st to end	Night	13% 2 24% 39% 21% 1	389
June	1st to 10th	Night	14% 4 23% 42% 14% 2	360
	11th to 20th	Night	13% 6% 23% 40% 18% 1	360
	21st to end	Night	17% 3 18% 39% 22% 1	360
July	1st to 10th	Night	9% 3 17% 46% 21% 3	350
	11th to 20th	Night	10% 2 20% 39% 28% 2	424
	21st to end	Night	10% 3 16% 45% 25% 1	591
August	1st to 10th	Night	12% 3 16% 37% 31% 1	537
	11th to 20th	Night	11% 2 13% 38% 30% 5%	534
	21st to end	Night	15% 3 18% 34% 28% 2	594
September	1st to 10th	Night	12% 3 21% 37% 20% 7%	708
	11th to 20th	Night	14% 3 18% 38% 22% 4	720
	21st to end	Night	18% 7% 22% 29% 20% 5%	720
October	1st to 10th	Night	23% 7% 23% 30% 15% 2	720
	11th to 20th	Night	30% 10% 24% 27% 7% 1	720
	21st to end	Night	37% 11% 25% 23% 4 1	792
November	1st to 10th	Night	29% 12% 27% 23% 9% 1	740
	11th to 20th	Night	26% 19% 28% 19% 7%	760
	21st to end	Night	34% 13% 30% 20% 3	760
December	1st to 10th	Night	33% 14% 31% 17% 4	760
	11th to 20th	Night	26% 16% 38% 17% 4	826
	21st to end	Night	32% 14% 32% 18% 3	1045

Page generated at 2024-04-07 09:28:09. Version ac07

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