Leduc
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leduc clear sky chart from 2005-11-06 to 2024-11-04.

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	9% 9% 3 8% 6% 5% 5% 4 6% 8% 35%	105880
	Night	8% 10% 4 10% 6% 6% 5% 4 6% 8% 33%	101667
Transparency	Day	44% 9% 17% 23% 8% 1	105624
	Night	46% 8% 16% 21% 9% 1	101569
Seeing	Day	13% 7% 23% 31% 19% 6%	15612
	Night	13% 6% 27% 36% 16% 2	24398

By Month

Percentage Cloud Cover NW (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	4 11% 5% 11% 10% 7% 5% 4 7% 9% 27%	2219
	11th to 20th	Day	5% 10% 4 9% 5% 5% 8% 5% 7% 9% 33%	2199
	21st to end	Day	7% 13% 5% 9% 6% 5% 4 4 6% 7% 35%	2638
February	1st to 10th	Day	8% 15% 5% 11% 7% 5% 5% 4 8% 9% 24%	1520
	11th to 20th	Day	5% 13% 7% 11% 7% 6% 6% 5% 6% 7% 27%	1615
	21st to end	Day	3 13% 6% 11% 8% 7% 8% 5% 7% 7% 24%	1470
March	1st to 10th	Day	4 11% 6% 14% 8% 6% 5% 4 5% 9% 27%	3138
	11th to 20th	Day	5% 12% 3 7% 4 4 4 4 7% 10% 40%	3454
	21st to end	Day	6% 13% 7% 17% 7% 5% 5% 4 5% 8% 22%	3877
April	1st to 10th	Day	7% 13% 4 9% 6% 6% 5% 4 7% 8% 30%	2370
	11th to 20th	Day	11% 12% 4 8% 6% 5% 5% 5% 7% 8% 29%	2440
	21st to end	Day	12% 10% 4 9% 6% 5% 5% 4 7% 8% 31%	2470
May	1st to 10th	Day	15% 9% 3 9% 6% 5% 5% 5% 5% 7% 30%	4602
	11th to 20th	Day	11% 11% 3 9% 6% 6% 6% 5% 7% 7% 29%	4694
	21st to end	Day	12% 8% 3 9% 6% 7% 6% 5% 7% 9% 28%	5161
June	1st to 10th	Day	16% 8% 3 8% 5% 6% 5% 4 7% 8% 31%	2850
	11th to 20th	Day	18% 10% 4 8% 7% 6% 6% 5% 6% 7% 24%	2850
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 8% 11% 37%	3006
July	1st to 10th	Day	9% 5% 2 6% 4 3 4 4 6% 9% 49%	4740
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 7% 8% 48%	4740
	21st to end	Day	12% 6% 2 5% 4 4 5% 5% 6% 7% 46%	5138
August	1st to 10th	Day	12% 6% 2 6% 5% 4 5% 5% 7% 9% 40%	4500
	11th to 20th	Day	9% 5% 2 6% 5% 4 5% 4 8% 10% 43%	4145
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 9% 42%	4521
September	1st to 10th	Day	12% 5% 3 6% 5% 5% 5% 4 6% 8% 42%	2412
	11th to 20th	Day	14% 7% 2 6% 4 3 4 3 5% 9% 42%	2090
	21st to end	Day	9% 6% 2 7% 4 5% 5% 4 7% 8% 43%	2090
October	1st to 10th	Day	9% 8% 3 8% 5% 5% 4 4 6% 7% 41%	3302
	11th to 20th	Day	10% 9% 4 9% 5% 5% 5% 4 5% 9% 36%	2886
	21st to end	Day	8% 11% 3 9% 5% 5% 5% 3 6% 7% 38%	3072
November	1st to 10th	Day	8% 15% 6% 10% 6% 6% 5% 4 6% 6% 27%	1512
	11th to 20th	Day	7% 12% 5% 13% 6% 4 5% 4 6% 7% 31%	1375
	21st to end	Day	5% 11% 6% 13% 7% 6% 6% 4 5% 7% 31%	1330
December	1st to 10th	Day	6% 11% 4 13% 9% 6% 6% 4 6% 7% 27%	1330
	11th to 20th	Day	6% 11% 5% 11% 8% 5% 5% 6% 7% 8% 27%	1682
	21st to end	Day	4 8% 3 7% 7% 6% 5% 4 6% 8% 42%	2442
January	1st to 10th	Night	4 11% 5% 14% 8% 7% 7% 4 6% 7% 26%	4726
	11th to 20th	Night	4 9% 3 11% 9% 7% 5% 5% 7% 7% 33%	4699
	21st to end	Night	6% 14% 4 12% 6% 5% 4 4 5% 7% 32%	5046
February	1st to 10th	Night	5% 13% 5% 14% 8% 6% 7% 4 5% 7% 27%	2660
	11th to 20th	Night	5% 13% 4 11% 7% 6% 6% 6% 6% 7% 29%	2451
	21st to end	Night	5% 12% 4 10% 8% 6% 6% 5% 5% 7% 32%	1983
March	1st to 10th	Night	3 10% 6% 13% 8% 6% 6% 4 6% 10% 27%	3736
	11th to 20th	Night	4 9% 4 7% 5% 5% 6% 5% 7% 8% 38%	3524
	21st to end	Night	5% 13% 7% 16% 8% 7% 6% 5% 6% 7% 21%	3772
April	1st to 10th	Night	7% 11% 2 9% 7% 7% 6% 5% 8% 8% 31%	1809
	11th to 20th	Night	10% 12% 4 10% 7% 7% 6% 4 6% 7% 27%	1691
	21st to end	Night	12% 10% 4 8% 5% 4 5% 4 6% 9% 33%	1710
May	1st to 10th	Night	22% 10% 4 9% 5% 5% 4 3 5% 5% 28%	2343
	11th to 20th	Night	12% 10% 3 10% 6% 6% 6% 5% 7% 7% 27%	2199
	21st to end	Night	14% 10% 4 10% 6% 6% 6% 4 6% 9% 26%	2414
June	1st to 10th	Night	14% 8% 5% 8% 5% 5% 5% 5% 7% 8% 30%	1330
	11th to 20th	Night	16% 9% 4 10% 7% 6% 6% 6% 6% 8% 21%	1327
	21st to end	Night	11% 7% 3 7% 5% 5% 6% 5% 8% 8% 35%	1153
July	1st to 10th	Night	10% 7% 3 6% 5% 5% 5% 4 5% 8% 42%	2220
	11th to 20th	Night	7% 5% 3 7% 5% 6% 6% 5% 7% 10% 38%	2220
	21st to end	Night	14% 6% 2 4 4 4 4 4 7% 10% 42%	2414
August	1st to 10th	Night	14% 7% 2 6% 5% 4 4 4 7% 7% 39%	2427
	11th to 20th	Night	11% 8% 3 7% 4 5% 5% 5% 6% 9% 38%	2689
	21st to end	Night	11% 5% 2 7% 5% 5% 5% 4 7% 10% 40%	3146
September	1st to 10th	Night	12% 5% 3 7% 5% 4 4 4 6% 7% 44%	1766
	11th to 20th	Night	12% 7% 2 6% 5% 3 4 3 6% 8% 44%	2090
	21st to end	Night	9% 7% 2 7% 4 5% 4 4 6% 8% 42%	2090
October	1st to 10th	Night	9% 7% 3 8% 4 6% 5% 4 7% 8% 40%	3672
	11th to 20th	Night	9% 8% 3 7% 4 6% 5% 4 7% 9% 39%	4041
	21st to end	Night	6% 9% 4 9% 6% 5% 6% 4 6% 8% 36%	4457
November	1st to 10th	Night	11% 15% 6% 9% 6% 4 5% 3 6% 7% 26%	2636
	11th to 20th	Night	6% 15% 5% 10% 6% 6% 5% 4 6% 7% 29%	2802
	21st to end	Night	5% 12% 4 12% 8% 6% 6% 4 6% 8% 28%	2850
December	1st to 10th	Night	8% 14% 5% 11% 7% 6% 5% 4 5% 6% 29%	2850
	11th to 20th	Night	6% 12% 6% 12% 7% 5% 6% 5% 6% 8% 26%	3510
	21st to end	Night	3 8% 3 9% 6% 6% 5% 4 6% 8% 42%	5214

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	51% 9% 13% 20% 7%	2219
	11th to 20th	Day	45% 7% 11% 15% 20% 2	2220
	21st to end	Day	46% 7% 18% 23% 5%	2638
February	1st to 10th	Day	54% 5% 16% 16% 8% 1	1520
	11th to 20th	Day	54% 8% 14% 16% 8%	1624
	21st to end	Day	52% 8% 14% 18% 8%	1470
March	1st to 10th	Day	54% 6% 14% 17% 8%	3138
	11th to 20th	Day	37% 9% 19% 22% 13%	3455
	21st to end	Day	58% 8% 11% 18% 4	3877
April	1st to 10th	Day	48% 10% 15% 19% 7% 1	2370
	11th to 20th	Day	49% 8% 13% 21% 8%	2440
	21st to end	Day	47% 9% 15% 20% 7% 2	2470
May	1st to 10th	Day	51% 8% 11% 24% 6%	4602
	11th to 20th	Day	47% 10% 13% 22% 8%	4698
	21st to end	Day	46% 11% 16% 18% 8%	5162
June	1st to 10th	Day	49% 7% 15% 20% 8% 1	2850
	11th to 20th	Day	56% 9% 15% 16% 4	2850
	21st to end	Day	37% 11% 22% 23% 6% 1	3006
July	1st to 10th	Day	30% 9% 17% 29% 15% 1	4666
	11th to 20th	Day	32% 9% 18% 29% 13%	4659
	21st to end	Day	35% 9% 20% 24% 12% 1	4976
August	1st to 10th	Day	37% 10% 18% 32% 2	4482
	11th to 20th	Day	33% 9% 23% 29% 7%	4187
	21st to end	Day	35% 8% 29% 23% 4	4520
September	1st to 10th	Day	38% 8% 20% 25% 7% 2	2412
	11th to 20th	Day	38% 8% 19% 29% 7%	2090
	21st to end	Day	36% 10% 19% 26% 8% 2	2090
October	1st to 10th	Day	41% 6% 23% 24% 5%	3302
	11th to 20th	Day	44% 7% 15% 24% 10%	2886
	21st to end	Day	44% 7% 18% 27% 4	3072
November	1st to 10th	Day	56% 9% 13% 16% 6% 1	1512
	11th to 20th	Day	51% 8% 16% 19% 6%	1375
	21st to end	Day	51% 9% 15% 18% 6% 1	1330
December	1st to 10th	Day	55% 8% 11% 16% 8% 1	1330
	11th to 20th	Day	49% 9% 18% 16% 7%	1684
	21st to end	Day	38% 8% 10% 26% 16% 2	2442
January	1st to 10th	Night	53% 9% 14% 16% 7% 1	4726
	11th to 20th	Night	48% 7% 13% 15% 15% 2	4740
	21st to end	Night	49% 8% 16% 20% 7%	5046
February	1st to 10th	Night	54% 6% 12% 18% 8% 1	2660
	11th to 20th	Night	51% 8% 13% 17% 10% 1	2452
	21st to end	Night	48% 8% 12% 20% 11% 1	1983
March	1st to 10th	Night	50% 8% 14% 20% 8%	3736
	11th to 20th	Night	39% 9% 21% 20% 11% 1	3524
	21st to end	Night	57% 10% 11% 16% 5%	3772
April	1st to 10th	Night	46% 10% 14% 19% 11% 1	1809
	11th to 20th	Night	53% 7% 11% 18% 9% 2	1691
	21st to end	Night	46% 9% 14% 19% 12% 1	1710
May	1st to 10th	Night	56% 6% 9% 19% 10% 1	2343
	11th to 20th	Night	48% 11% 12% 20% 8% 1	2199
	21st to end	Night	49% 13% 13% 14% 9% 1	2414
June	1st to 10th	Night	49% 10% 13% 19% 8% 1	1330
	11th to 20th	Night	58% 10% 15% 13% 4	1327
	21st to end	Night	42% 11% 21% 21% 4 1	1153
July	1st to 10th	Night	38% 8% 17% 21% 15% 1	2185
	11th to 20th	Night	37% 11% 17% 26% 9% 1	2178
	21st to end	Night	35% 9% 20% 27% 9%	2337
August	1st to 10th	Night	40% 10% 18% 29% 2	2420
	11th to 20th	Night	39% 10% 21% 22% 7%	2713
	21st to end	Night	37% 9% 22% 27% 5%	3146
September	1st to 10th	Night	38% 8% 17% 24% 12% 2	1766
	11th to 20th	Night	38% 8% 16% 28% 8% 2	2090
	21st to end	Night	37% 8% 14% 24% 13% 2	2090
October	1st to 10th	Night	39% 7% 21% 26% 7%	3672
	11th to 20th	Night	39% 7% 15% 31% 7%	4041
	21st to end	Night	43% 8% 20% 24% 5%	4457
November	1st to 10th	Night	55% 7% 12% 18% 7%	2636
	11th to 20th	Night	53% 8% 13% 18% 7% 1	2802
	21st to end	Night	51% 8% 16% 17% 6% 1	2850
December	1st to 10th	Night	54% 5% 13% 17% 9% 1	2850
	11th to 20th	Night	53% 9% 17% 16% 6%	3507
	21st to end	Night	37% 7% 16% 20% 16% 3	5214

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	8% 6% 26% 33% 22% 6%	180
	11th to 20th	Day	8% 9% 26% 36% 16% 6%	180
	21st to end	Day	12% 7% 28% 32% 15% 7%	198
February	1st to 10th	Day	11% 12% 25% 33% 14% 5%	180
	11th to 20th	Day	13% 2 28% 34% 18% 5%	247
	21st to end	Day	7% 4 29% 33% 18% 8%	282
March	1st to 10th	Day	11% 7% 27% 34% 17% 3	460
	11th to 20th	Day	10% 4 26% 35% 18% 7%	460
	21st to end	Day	14% 5% 24% 32% 20% 4	506
April	1st to 10th	Day	10% 13% 28% 35% 11% 4	460
	11th to 20th	Day	15% 6% 23% 31% 19% 5%	452
	21st to end	Day	17% 10% 25% 28% 15% 5%	460
May	1st to 10th	Day	14% 9% 23% 33% 17% 4	603
	11th to 20th	Day	11% 6% 22% 36% 20% 6%	675
	21st to end	Day	15% 7% 20% 30% 20% 8%	734
June	1st to 10th	Day	18% 9% 25% 31% 14% 3	680
	11th to 20th	Day	18% 8% 22% 26% 19% 7%	680
	21st to end	Day	12% 5% 19% 30% 25% 8%	836
July	1st to 10th	Day	12% 4 15% 35% 24% 9%	671
	11th to 20th	Day	11% 4 20% 30% 26% 9%	668
	21st to end	Day	10% 5% 17% 31% 25% 11%	739
August	1st to 10th	Day	11% 4 19% 31% 23% 13%	547
	11th to 20th	Day	9% 5% 20% 33% 26% 7%	477
	21st to end	Day	13% 6% 19% 28% 26% 9%	539
September	1st to 10th	Day	14% 7% 26% 25% 20% 8%	490
	11th to 20th	Day	19% 6% 23% 29% 18% 5%	490
	21st to end	Day	12% 12% 29% 28% 15% 4	490
October	1st to 10th	Day	16% 6% 28% 28% 17% 5%	380
	11th to 20th	Day	13% 8% 32% 30% 14% 4	300
	21st to end	Day	15% 14% 31% 26% 12% 3	330
November	1st to 10th	Day	16% 5% 27% 34% 15% 3	279
	11th to 20th	Day	14% 6% 30% 34% 13% 2	201
	21st to end	Day	6% 5% 33% 39% 12% 5%	180
December	1st to 10th	Day	9% 5% 26% 36% 20% 4	180
	11th to 20th	Day	12% 8% 28% 29% 18% 4	180
	21st to end	Day	9% 4 19% 41% 23% 5%	198
January	1st to 10th	Night	10% 8% 31% 35% 15% 2	950
	11th to 20th	Night	11% 8% 32% 35% 13% 2	950
	21st to end	Night	13% 11% 32% 31% 11% 2	942
February	1st to 10th	Night	9% 7% 24% 39% 19% 3	760
	11th to 20th	Night	11% 6% 32% 36% 15% 1	744
	21st to end	Night	10% 4 25% 35% 21% 4	628
March	1st to 10th	Night	9% 5% 28% 39% 16% 3	760
	11th to 20th	Night	11% 4 30% 36% 15% 3	760
	21st to end	Night	13% 6% 25% 37% 16% 3	836
April	1st to 10th	Night	12% 6% 28% 32% 19% 2	669
	11th to 20th	Night	15% 6% 27% 36% 15% 1	563
	21st to end	Night	15% 7% 28% 34% 15% 1	570
May	1st to 10th	Night	16% 8% 24% 36% 14% 1	415
	11th to 20th	Night	11% 6% 26% 38% 17% 2	374
	21st to end	Night	19% 5% 22% 33% 18% 2	411
June	1st to 10th	Night	18% 6% 26% 35% 13% 2	380
	11th to 20th	Night	19% 5% 25% 31% 18% 2	380
	21st to end	Night	12% 6% 17% 35% 28% 2	380
July	1st to 10th	Night	15% 2 14% 44% 24%	370
	11th to 20th	Night	10% 4 20% 43% 21% 2	368
	21st to end	Night	13% 4 15% 41% 24% 3	416
August	1st to 10th	Night	13% 4 16% 33% 29% 4	378
	11th to 20th	Night	15% 2 17% 38% 25% 2	490
	21st to end	Night	13% 2 20% 41% 23% 1	627
September	1st to 10th	Night	14% 3 18% 42% 21% 2	616
	11th to 20th	Night	14% 3 21% 42% 20% 1	760
	21st to end	Night	11% 5% 30% 39% 14% 1	760
October	1st to 10th	Night	15% 5% 27% 38% 14% 1	760
	11th to 20th	Night	14% 4 33% 33% 13% 2	760
	21st to end	Night	12% 7% 32% 34% 14%	836
November	1st to 10th	Night	19% 6% 29% 34% 10% 1	940
	11th to 20th	Night	13% 8% 33% 32% 11% 2	950
	21st to end	Night	9% 5% 36% 37% 11% 2	950
December	1st to 10th	Night	15% 7% 30% 30% 14% 3	950
	11th to 20th	Night	11% 6% 33% 35% 14% 2	950
	21st to end	Night	10% 5% 29% 36% 18% 3	1045

Page generated at 2024-11-01 20:47:42. Version ac07

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