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 2024-11-05.

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% 12% 4 9% 5% 4 4 3 5% 7% 32%	101491
	Night	16% 14% 6% 11% 6% 4 4 3 4 5% 27%	97568
Transparency	Day	52% 5% 12% 20% 10% 1	105050
	Night	58% 4 11% 17% 9% 1	102097
Seeing	Day	19% 10% 28% 26% 13% 4	15195
	Night	22% 10% 27% 28% 12% 1	24418

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% 26% 12% 17% 8% 5% 3 2 2 3 7%	2275
	11th to 20th	Day	11% 22% 10% 24% 15% 5% 3 2 2 2 4	2591
	21st to end	Day	18% 23% 10% 17% 7% 5% 4 2 3 3 7%	3124
February	1st to 10th	Day	13% 20% 8% 19% 9% 6% 4 2 4 4 11%	1710
	11th to 20th	Day	12% 14% 9% 19% 10% 5% 4 4 4 4 14%	1663
	21st to end	Day	15% 19% 6% 13% 8% 5% 4 3 5% 5% 19%	1546
March	1st to 10th	Day	17% 16% 4 9% 6% 5% 4 3 4 5% 28%	3324
	11th to 20th	Day	11% 17% 8% 12% 5% 5% 5% 4 4 5% 24%	3480
	21st to end	Day	15% 13% 5% 10% 6% 4 4 4 5% 5% 29%	3815
April	1st to 10th	Day	17% 13% 5% 9% 5% 4 4 3 5% 6% 29%	2187
	11th to 20th	Day	18% 11% 3 6% 4 4 4 2 5% 6% 37%	2442
	21st to end	Day	19% 9% 3 7% 4 3 4 4 5% 6% 35%	2470
May	1st to 10th	Day	17% 9% 2 6% 4 4 4 3 6% 7% 39%	4108
	11th to 20th	Day	15% 9% 2 6% 4 4 4 3 6% 8% 40%	4203
	21st to end	Day	14% 6% 2 5% 4 4 3 3 5% 7% 48%	4837
June	1st to 10th	Day	14% 7% 3 6% 4 4 5% 4 5% 7% 41%	2799
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 4 6% 9% 44%	2850
	21st to end	Day	14% 7% 2 5% 4 4 4 4 5% 8% 42%	2850
July	1st to 10th	Day	13% 6% 3 5% 4 5% 5% 4 6% 9% 40%	4760
	11th to 20th	Day	12% 5% 2 4 4 3 4 3 5% 9% 49%	4593
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 10% 47%	4466
August	1st to 10th	Day	12% 5% 2 6% 4 4 5% 5% 7% 9% 42%	4104
	11th to 20th	Day	14% 6% 2 7% 4 4 4 5% 6% 9% 40%	4044
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 10% 45%	4510
September	1st to 10th	Day	13% 7% 2 7% 5% 4 4 4 6% 9% 39%	2237
	11th to 20th	Day	13% 6% 2 5% 5% 4 4 3 6% 8% 45%	2090
	21st to end	Day	17% 8% 2 7% 4 5% 5% 4 6% 6% 35%	2090
October	1st to 10th	Day	20% 8% 3 8% 5% 4 4 4 5% 6% 33%	1938
	11th to 20th	Day	25% 15% 4 9% 5% 5% 5% 3 4 6% 20%	1900
	21st to end	Day	29% 17% 5% 9% 5% 4 3 2 4 4 18%	2009
November	1st to 10th	Day	16% 21% 5% 9% 6% 5% 4 3 5% 5% 22%	1692
	11th to 20th	Day	17% 23% 6% 11% 4 4 5% 4 4 6% 16%	1520
	21st to end	Day	20% 26% 9% 12% 4 4 4 2 4 5% 10%	1520
December	1st to 10th	Day	17% 30% 10% 18% 6% 4 3 2 2 2 5%	1520
	11th to 20th	Day	18% 25% 8% 19% 6% 4 4 3 3 3 7%	1793
	21st to end	Day	25% 26% 8% 13% 6% 4 3 2 3 3 7%	2431
January	1st to 10th	Night	15% 26% 13% 19% 8% 4 3 2 3 3 5%	4680
	11th to 20th	Night	14% 18% 10% 24% 12% 6% 4 2 2 3 5%	4374
	21st to end	Night	17% 22% 10% 17% 8% 5% 4 2 4 3 8%	4532
February	1st to 10th	Night	13% 22% 8% 19% 9% 5% 4 3 4 3 11%	2470
	11th to 20th	Night	13% 17% 9% 18% 7% 4 4 3 4 4 16%	2403
	21st to end	Night	14% 16% 6% 14% 7% 5% 4 3 5% 6% 20%	1903
March	1st to 10th	Night	13% 14% 5% 10% 5% 4 3 3 5% 6% 33%	3515
	11th to 20th	Night	11% 16% 6% 10% 5% 3 4 3 4 5% 32%	3479
	21st to end	Night	15% 11% 6% 13% 5% 4 4 3 4 4 29%	3817
April	1st to 10th	Night	19% 14% 4 9% 5% 4 3 3 4 6% 29%	2007
	11th to 20th	Night	18% 10% 3 6% 4 4 4 3 4 7% 37%	1687
	21st to end	Night	20% 10% 4 8% 5% 3 4 4 5% 6% 31%	1710
May	1st to 10th	Night	15% 8% 3 7% 5% 5% 4 4 5% 7% 39%	2833
	11th to 20th	Night	16% 7% 2 7% 5% 4 4 3 4 6% 41%	2687
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 5% 7% 47%	2738
June	1st to 10th	Night	15% 7% 2 7% 5% 4 4 4 5% 8% 39%	1377
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 4 7% 11% 40%	1330
	21st to end	Night	14% 6% 2 6% 5% 5% 4 4 6% 8% 41%	1330
July	1st to 10th	Night	10% 8% 4 6% 4 3 3 3 5% 8% 47%	2210
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 6% 8% 50%	2356
	21st to end	Night	7% 7% 2 6% 4 5% 4 4 6% 7% 49%	3087
August	1st to 10th	Night	12% 7% 2 8% 4 4 4 4 6% 6% 43%	2825
	11th to 20th	Night	14% 6% 3 8% 4 4 5% 3 6% 8% 41%	2785
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 7% 48%	3124
September	1st to 10th	Night	11% 5% 2 7% 4 4 4 4 5% 8% 46%	1928
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 5% 7% 49%	2090
	21st to end	Night	17% 8% 3 7% 5% 5% 5% 3 5% 5% 37%	2090
October	1st to 10th	Night	19% 8% 3 7% 5% 5% 4 4 5% 6% 35%	2242
	11th to 20th	Night	25% 12% 3 10% 5% 4 4 3 5% 5% 23%	2280
	21st to end	Night	28% 15% 3 10% 5% 4 5% 3 4 5% 18%	2588
November	1st to 10th	Night	18% 19% 4 8% 4 5% 3 4 4 6% 24%	2484
	11th to 20th	Night	18% 22% 5% 12% 6% 4 4 3 4 4 17%	2660
	21st to end	Night	22% 24% 8% 11% 6% 4 3 3 4 4 13%	2660
December	1st to 10th	Night	20% 31% 10% 15% 5% 3 3 2 3 2 6%	2660
	11th to 20th	Night	15% 25% 10% 18% 6% 4 4 3 4 3 10%	3391
	21st to end	Night	24% 24% 9% 15% 6% 4 3 2 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%	2187
	11th to 20th	Day	48% 5% 8% 23% 15% 1	2442
	21st to end	Day	50% 5% 11% 20% 12% 2	2470
May	1st to 10th	Day	44% 5% 12% 20% 18% 2	4120
	11th to 20th	Day	43% 5% 17% 23% 10% 1	4207
	21st to end	Day	37% 4 12% 22% 20% 5%	4837
June	1st to 10th	Day	41% 5% 12% 25% 15% 1	2799
	11th to 20th	Day	36% 5% 12% 27% 19% 1	2850
	21st to end	Day	41% 5% 14% 24% 14% 1	2850
July	1st to 10th	Day	40% 6% 16% 20% 16% 2	4686
	11th to 20th	Day	32% 5% 14% 36% 12% 1	4512
	21st to end	Day	32% 6% 13% 29% 18% 2	4324
August	1st to 10th	Day	37% 6% 14% 25% 16% 1	4091
	11th to 20th	Day	41% 6% 15% 26% 11%	4083
	21st to end	Day	35% 6% 15% 32% 12% 1	4510
September	1st to 10th	Day	40% 6% 13% 26% 12% 2	2237
	11th to 20th	Day	37% 5% 15% 29% 14%	2090
	21st to end	Day	48% 5% 14% 24% 9% 1	2090
October	1st to 10th	Day	46% 4 13% 25% 10% 1	3224
	11th to 20th	Day	54% 4 11% 22% 9%	3140
	21st to end	Day	64% 4 12% 16% 4	3285
November	1st to 10th	Day	64% 5% 10% 15% 6%	1692
	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	57% 3 8% 20% 11% 1	2007
	11th to 20th	Night	48% 5% 7% 21% 18% 2	1687
	21st to end	Night	54% 4 8% 17% 15% 2	1710
May	1st to 10th	Night	45% 4 11% 21% 16% 3	2840
	11th to 20th	Night	44% 4 11% 24% 16% 2	2688
	21st to end	Night	37% 3 13% 24% 20% 3	2739
June	1st to 10th	Night	43% 5% 10% 23% 18% 3	1377
	11th to 20th	Night	36% 6% 14% 25% 18% 2	1330
	21st to end	Night	40% 4 13% 25% 16% 2	1330
July	1st to 10th	Night	38% 3 12% 24% 17% 6%	2175
	11th to 20th	Night	31% 5% 12% 36% 15% 2	2314
	21st to end	Night	33% 6% 14% 26% 21% 1	2988
August	1st to 10th	Night	41% 4 12% 28% 15% 1	2814
	11th to 20th	Night	41% 5% 16% 23% 14% 1	2812
	21st to end	Night	36% 5% 12% 32% 14% 1	3124
September	1st to 10th	Night	34% 6% 13% 30% 14% 2	1928
	11th to 20th	Night	36% 3 14% 30% 16%	2090
	21st to end	Night	49% 4 13% 25% 9%	2090
October	1st to 10th	Night	41% 5% 12% 26% 16% 1	3736
	11th to 20th	Night	52% 4 16% 18% 11%	3779
	21st to end	Night	56% 4 15% 19% 5%	4262
November	1st to 10th	Night	60% 4 11% 19% 5%	2484
	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	22% 14% 33% 21% 8% 1	460
	11th to 20th	Day	29% 13% 27% 16% 9% 6%	452
	21st to end	Day	25% 9% 28% 26% 10% 2	460
May	1st to 10th	Day	21% 8% 30% 27% 11% 3	463
	11th to 20th	Day	20% 6% 26% 27% 17% 4	487
	21st to end	Day	14% 7% 25% 30% 17% 7%	529
June	1st to 10th	Day	14% 8% 28% 33% 15% 2	629
	11th to 20th	Day	13% 7% 29% 32% 16% 3	680
	21st to end	Day	16% 6% 30% 32% 13% 3	680
July	1st to 10th	Day	11% 4 25% 34% 21% 5%	671
	11th to 20th	Day	13% 4 27% 32% 17% 7%	664
	21st to end	Day	12% 4 21% 37% 19% 7%	532
August	1st to 10th	Day	12% 5% 20% 34% 20% 10%	486
	11th to 20th	Day	14% 4 15% 33% 22% 12%	479
	21st to end	Day	16% 5% 19% 31% 22% 8%	539
September	1st to 10th	Day	14% 7% 20% 33% 19% 8%	490
	11th to 20th	Day	10% 6% 19% 27% 26% 12%	490
	21st to end	Day	16% 8% 26% 27% 17% 7%	490
October	1st to 10th	Day	21% 10% 26% 23% 13% 6%	490
	11th to 20th	Day	27% 15% 30% 21% 6% 1	490
	21st to end	Day	34% 15% 29% 17% 5%	458
November	1st to 10th	Day	24% 19% 30% 20% 6% 1	274
	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	23% 9% 27% 28% 10% 2	563
	21st to end	Night	26% 8% 22% 31% 12% 1	570
May	1st to 10th	Night	20% 4 23% 37% 15% 2	570
	11th to 20th	Night	19% 5% 19% 40% 15% 1	488
	21st to end	Night	13% 2 23% 40% 20% 1	411
June	1st to 10th	Night	14% 5% 23% 41% 14% 2	380
	11th to 20th	Night	13% 5% 24% 40% 18% 1	380
	21st to end	Night	17% 4 18% 39% 21% 1	380
July	1st to 10th	Night	10% 4 18% 46% 20% 2	370
	11th to 20th	Night	10% 2 20% 38% 28% 2	449
	21st to end	Night	10% 3 16% 44% 26% 1	624
August	1st to 10th	Night	12% 3 16% 37% 31% 1	567
	11th to 20th	Night	12% 2 13% 38% 30% 5%	564
	21st to end	Night	15% 3 17% 35% 28% 2	627
September	1st to 10th	Night	12% 4 21% 36% 21% 7%	748
	11th to 20th	Night	14% 3 17% 38% 25% 4	760
	21st to end	Night	18% 7% 22% 30% 19% 5%	760
October	1st to 10th	Night	22% 7% 24% 31% 14% 2	760
	11th to 20th	Night	29% 11% 24% 28% 8% 1	760
	21st to end	Night	35% 12% 25% 24% 4	836
November	1st to 10th	Night	29% 12% 27% 22% 9% 1	760
	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 2024-11-03 02:11:07. Version ac07

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