Donnacona
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Donnacona clear sky chart from 2005-11-06 to 2024-12-06.

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	18% 10% 3 8% 5% 5% 5% 4 5% 7% 31%	101587
	Night	19% 12% 4 8% 5% 4 4 3 5% 6% 29%	98132
Transparency	Day	29% 47% 8% 11% 5%	105047
	Night	31% 47% 7% 10% 4	102762
Seeing	Day	24% 14% 29% 22% 9% 2	15144
	Night	25% 10% 29% 27% 8% 1	23795

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% 18% 5% 12% 6% 5% 5% 4 4 5% 21%	2517
	11th to 20th	Day	11% 15% 7% 16% 7% 5% 3 3 4 4 26%	2520
	21st to end	Day	11% 14% 5% 9% 6% 4 4 4 6% 7% 30%	2772
February	1st to 10th	Day	11% 16% 6% 11% 7% 5% 5% 4 4 6% 24%	1534
	11th to 20th	Day	14% 15% 5% 10% 6% 5% 6% 4 5% 5% 24%	1828
	21st to end	Day	13% 15% 5% 11% 6% 5% 4 4 5% 7% 27%	1570
March	1st to 10th	Day	20% 12% 3 8% 5% 5% 4 3 5% 5% 30%	3116
	11th to 20th	Day	16% 17% 5% 10% 5% 5% 4 3 4 5% 25%	3288
	21st to end	Day	15% 13% 3 7% 5% 4 4 3 5% 5% 36%	4096
April	1st to 10th	Day	22% 11% 4 8% 6% 5% 4 3 4 5% 29%	2280
	11th to 20th	Day	20% 7% 3 8% 5% 4 4 3 4 5% 38%	2323
	21st to end	Day	23% 9% 3 8% 5% 4 4 3 4 6% 31%	2470
May	1st to 10th	Day	21% 8% 3 7% 4 4 4 4 5% 7% 34%	4234
	11th to 20th	Day	16% 7% 2 8% 5% 5% 5% 4 7% 9% 32%	4398
	21st to end	Day	17% 7% 3 8% 5% 5% 6% 5% 5% 7% 32%	4837
June	1st to 10th	Day	19% 7% 2 8% 6% 6% 5% 4 6% 8% 28%	2802
	11th to 20th	Day	18% 7% 3 6% 5% 4 5% 5% 6% 7% 35%	2850
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 6% 7% 27%	2806
July	1st to 10th	Day	15% 8% 3 7% 6% 5% 5% 5% 6% 7% 32%	4440
	11th to 20th	Day	17% 7% 3 7% 5% 5% 5% 5% 7% 8% 31%	4440
	21st to end	Day	14% 5% 2 6% 4 5% 5% 4 6% 8% 40%	4814
August	1st to 10th	Day	17% 5% 2 7% 5% 5% 6% 5% 8% 10% 30%	4423
	11th to 20th	Day	21% 6% 2 7% 4 5% 5% 4 7% 8% 31%	4051
	21st to end	Day	22% 6% 2 6% 4 4 4 3 5% 6% 38%	4285
September	1st to 10th	Day	16% 6% 3 7% 4 4 4 4 5% 8% 38%	2280
	11th to 20th	Day	18% 5% 2 5% 3 3 4 3 4 7% 46%	2128
	21st to end	Day	21% 7% 3 7% 3 3 4 3 4 7% 37%	2090
October	1st to 10th	Day	22% 7% 3 8% 4 5% 5% 5% 5% 6% 31%	2063
	11th to 20th	Day	24% 8% 3 10% 5% 5% 5% 4 6% 6% 25%	1758
	21st to end	Day	27% 11% 3 7% 5% 4 4 4 4 5% 25%	1881
November	1st to 10th	Day	20% 11% 3 8% 4 5% 4 3 5% 5% 31%	1761
	11th to 20th	Day	21% 13% 4 10% 6% 4 4 3 5% 5% 26%	1785
	21st to end	Day	23% 17% 4 8% 5% 4 4 5% 4 6% 21%	1495
December	1st to 10th	Day	24% 17% 5% 9% 6% 4 4 2 4 4 21%	1365
	11th to 20th	Day	22% 13% 4 10% 7% 4 4 3 4 5% 25%	1668
	21st to end	Day	23% 18% 4 9% 4 4 3 3 4 5% 23%	2619
January	1st to 10th	Night	17% 19% 5% 12% 6% 4 4 3 4 4 21%	4429
	11th to 20th	Night	13% 17% 5% 13% 6% 5% 4 3 4 6% 23%	4440
	21st to end	Night	12% 15% 5% 11% 7% 6% 5% 4 5% 6% 25%	4884
February	1st to 10th	Night	12% 14% 6% 12% 8% 5% 5% 3 5% 4 26%	2644
	11th to 20th	Night	13% 16% 5% 12% 6% 5% 4 3 5% 5% 25%	2237
	21st to end	Night	16% 15% 4 9% 5% 4 5% 3 5% 6% 29%	1884
March	1st to 10th	Night	25% 12% 4 6% 5% 3 5% 3 4 5% 28%	3724
	11th to 20th	Night	18% 17% 4 11% 6% 5% 4 3 4 5% 23%	3671
	21st to end	Night	17% 15% 4 8% 5% 3 4 3 4 5% 32%	3534
April	1st to 10th	Night	22% 14% 4 7% 4 3 4 3 5% 5% 28%	1900
	11th to 20th	Night	22% 9% 2 6% 5% 4 4 4 4 6% 33%	1805
	21st to end	Night	23% 10% 2 7% 4 3 3 3 5% 6% 34%	1710
May	1st to 10th	Night	23% 8% 3 7% 5% 5% 5% 3 5% 6% 31%	2720
	11th to 20th	Night	22% 7% 2 7% 4 4 3 4 5% 6% 34%	2495
	21st to end	Night	19% 6% 2 6% 5% 5% 5% 4 6% 9% 34%	2738
June	1st to 10th	Night	22% 9% 2 5% 6% 4 5% 4 6% 9% 29%	1374
	11th to 20th	Night	20% 7% 2 6% 4 3 5% 4 7% 7% 35%	1330
	21st to end	Night	21% 10% 3 7% 4 4 4 3 6% 7% 29%	1367
July	1st to 10th	Night	15% 6% 2 9% 5% 6% 6% 5% 6% 8% 31%	2520
	11th to 20th	Night	21% 6% 2 6% 5% 4 4 4 6% 6% 36%	2520
	21st to end	Night	14% 6% 2 6% 4 5% 5% 4 6% 7% 42%	2739
August	1st to 10th	Night	19% 7% 3 7% 5% 5% 5% 4 6% 7% 33%	2506
	11th to 20th	Night	20% 6% 3 8% 5% 5% 5% 4 6% 7% 31%	2745
	21st to end	Night	20% 7% 3 8% 5% 4 5% 4 4 6% 34%	3369
September	1st to 10th	Night	19% 6% 2 6% 5% 3 4 3 5% 6% 41%	1900
	11th to 20th	Night	18% 5% 2 6% 4 4 4 4 4 6% 44%	2052
	21st to end	Night	19% 7% 3 6% 4 4 4 3 4 6% 40%	2090
October	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 6% 5% 37%	2114
	11th to 20th	Night	24% 10% 3 8% 4 5% 4 3 5% 5% 30%	2422
	21st to end	Night	27% 10% 3 7% 4 4 4 3 5% 6% 28%	2717
November	1st to 10th	Night	20% 11% 3 7% 4 5% 4 3 4 7% 31%	2537
	11th to 20th	Night	20% 12% 4 7% 4 4 4 3 5% 6% 31%	2614
	21st to end	Night	24% 15% 4 9% 5% 4 4 3 4 4 24%	2900
December	1st to 10th	Night	23% 16% 5% 10% 7% 5% 4 3 4 4 19%	2932
	11th to 20th	Night	21% 16% 4 11% 6% 5% 4 3 3 5% 23%	3531
	21st to end	Night	25% 19% 4 8% 4 3 3 3 3 3 24%	5038

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	42% 38% 8% 9% 2	2518
	11th to 20th	Day	40% 38% 6% 12% 3	2520
	21st to end	Day	33% 39% 9% 15% 3	2772
February	1st to 10th	Day	22% 65% 5% 4 3 1	1534
	11th to 20th	Day	22% 64% 3 7% 4	1837
	21st to end	Day	22% 65% 4 4 4 2	1570
March	1st to 10th	Day	35% 44% 6% 10% 5% 2	3119
	11th to 20th	Day	40% 40% 7% 8% 5% 1	3288
	21st to end	Day	31% 40% 5% 12% 9% 3	4096
April	1st to 10th	Day	20% 64% 4 6% 4 2	2280
	11th to 20th	Day	19% 66% 3 8% 3 1	2323
	21st to end	Day	22% 65% 3 5% 5%	2470
May	1st to 10th	Day	31% 41% 8% 11% 8%	4248
	11th to 20th	Day	30% 42% 16% 9% 3	4402
	21st to end	Day	30% 42% 7% 11% 8%	4837
June	1st to 10th	Day	18% 66% 5% 8% 3 1	2802
	11th to 20th	Day	15% 66% 5% 7% 6%	2850
	21st to end	Day	18% 65% 4 8% 4	2806
July	1st to 10th	Day	32% 38% 9% 15% 5%	4370
	11th to 20th	Day	31% 39% 15% 13% 2	4365
	21st to end	Day	23% 38% 14% 19% 6%	4661
August	1st to 10th	Day	28% 42% 13% 13% 4	4409
	11th to 20th	Day	35% 41% 12% 10% 2	4090
	21st to end	Day	30% 39% 10% 10% 10%	4285
September	1st to 10th	Day	17% 61% 7% 10% 4	2280
	11th to 20th	Day	16% 61% 7% 11% 4 1	2128
	21st to end	Day	16% 60% 5% 14% 5%	2090
October	1st to 10th	Day	35% 39% 8% 15% 3	3427
	11th to 20th	Day	33% 41% 12% 13% 1	2896
	21st to end	Day	33% 39% 15% 9% 5%	3081
November	1st to 10th	Day	28% 56% 6% 7% 3	1761
	11th to 20th	Day	25% 57% 4 10% 3 1	1785
	21st to end	Day	30% 58% 5% 5% 2	1495
December	1st to 10th	Day	28% 59% 3 7% 2	1365
	11th to 20th	Day	32% 48% 4 11% 4	1668
	21st to end	Day	41% 38% 8% 7% 5% 1	2619
January	1st to 10th	Night	42% 38% 9% 7% 4	4429
	11th to 20th	Night	42% 38% 7% 12% 2	4440
	21st to end	Night	37% 40% 9% 9% 4	4884
February	1st to 10th	Night	22% 65% 3 7% 2	2644
	11th to 20th	Night	22% 64% 3 7% 4	2239
	21st to end	Night	18% 64% 4 6% 7% 1	1884
March	1st to 10th	Night	35% 43% 8% 8% 5% 2	3734
	11th to 20th	Night	42% 40% 5% 8% 4 1	3672
	21st to end	Night	36% 40% 4 13% 6% 1	3534
April	1st to 10th	Night	19% 65% 3 6% 6% 1	1900
	11th to 20th	Night	21% 65% 2 7% 4 1	1805
	21st to end	Night	17% 67% 3 7% 5%	1710
May	1st to 10th	Night	34% 41% 8% 13% 4	2726
	11th to 20th	Night	30% 42% 11% 12% 5%	2496
	21st to end	Night	28% 42% 8% 11% 11% 1	2739
June	1st to 10th	Night	17% 66% 5% 8% 4	1374
	11th to 20th	Night	16% 66% 4 7% 6% 1	1330
	21st to end	Night	20% 64% 5% 7% 5%	1367
July	1st to 10th	Night	32% 40% 12% 11% 5%	2480
	11th to 20th	Night	31% 39% 15% 13% 2	2472
	21st to end	Night	23% 38% 15% 19% 6%	2651
August	1st to 10th	Night	34% 39% 10% 12% 4	2496
	11th to 20th	Night	36% 41% 12% 9% 2	2772
	21st to end	Night	34% 39% 7% 11% 8%	3369
September	1st to 10th	Night	16% 61% 6% 10% 6% 1	1900
	11th to 20th	Night	16% 62% 8% 12% 3	2052
	21st to end	Night	16% 59% 5% 13% 7%	2090
October	1st to 10th	Night	35% 37% 10% 14% 4	3530
	11th to 20th	Night	31% 39% 10% 17% 2	4023
	21st to end	Night	31% 38% 13% 10% 8%	4467
November	1st to 10th	Night	27% 56% 6% 7% 4	2537
	11th to 20th	Night	24% 58% 4 10% 4	2614
	21st to end	Night	29% 58% 4 5% 3	2900
December	1st to 10th	Night	29% 58% 4 6% 2	2932
	11th to 20th	Night	35% 49% 3 9% 4	3532
	21st to end	Night	42% 37% 5% 12% 4 1	5038

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% 18% 33% 16% 3 1	180
	11th to 20th	Day	29% 18% 33% 14% 5%	180
	21st to end	Day	17% 19% 41% 15% 8%	198
February	1st to 10th	Day	23% 30% 30% 13% 4 1	186
	11th to 20th	Day	22% 21% 36% 17% 3	436
	21st to end	Day	26% 23% 29% 19% 4	382
March	1st to 10th	Day	25% 20% 30% 20% 5%	460
	11th to 20th	Day	25% 21% 30% 17% 5% 1	460
	21st to end	Day	26% 18% 27% 18% 8% 2	506
April	1st to 10th	Day	27% 19% 27% 21% 5%	460
	11th to 20th	Day	27% 18% 28% 20% 6% 2	452
	21st to end	Day	30% 18% 28% 16% 5% 2	460
May	1st to 10th	Day	25% 17% 33% 18% 5% 1	463
	11th to 20th	Day	19% 13% 32% 24% 10% 2	487
	21st to end	Day	23% 18% 34% 16% 9% 1	529
June	1st to 10th	Day	22% 12% 33% 23% 10% 1	632
	11th to 20th	Day	22% 10% 28% 27% 12% 1	680
	21st to end	Day	26% 9% 26% 24% 14% 1	636
July	1st to 10th	Day	16% 11% 31% 27% 13% 1	485
	11th to 20th	Day	16% 10% 33% 27% 11% 2	484
	21st to end	Day	17% 8% 30% 31% 12% 2	532
August	1st to 10th	Day	16% 9% 27% 31% 13% 3	486
	11th to 20th	Day	20% 6% 25% 28% 17% 4	479
	21st to end	Day	22% 11% 26% 18% 17% 7%	539
September	1st to 10th	Day	18% 10% 30% 24% 14% 4	490
	11th to 20th	Day	17% 11% 23% 26% 18% 5%	490
	21st to end	Day	21% 12% 27% 23% 13% 4	490
October	1st to 10th	Day	23% 11% 26% 26% 11% 2	490
	11th to 20th	Day	28% 13% 28% 20% 9% 1	415
	21st to end	Day	33% 15% 27% 19% 6%	429
November	1st to 10th	Day	32% 13% 26% 22% 6% 1	395
	11th to 20th	Day	30% 16% 29% 17% 8% 1	385
	21st to end	Day	33% 20% 29% 16% 3 1	200
December	1st to 10th	Day	33% 14% 26% 21% 6% 1	190
	11th to 20th	Day	29% 22% 26% 16% 6% 2	180
	21st to end	Day	37% 18% 29% 11% 5% 1	198
January	1st to 10th	Night	28% 13% 34% 21% 4	760
	11th to 20th	Night	27% 14% 34% 21% 4	760
	21st to end	Night	18% 11% 35% 29% 6%	836
February	1st to 10th	Night	19% 11% 37% 26% 6%	760
	11th to 20th	Night	20% 16% 38% 20% 5%	743
	21st to end	Night	24% 13% 33% 27% 4	628
March	1st to 10th	Night	25% 12% 34% 24% 4	760
	11th to 20th	Night	25% 13% 34% 21% 6% 1	760
	21st to end	Night	24% 10% 32% 27% 6% 1	836
April	1st to 10th	Night	30% 12% 29% 23% 5%	760
	11th to 20th	Night	28% 11% 32% 24% 5%	681
	21st to end	Night	28% 14% 31% 22% 5%	570
May	1st to 10th	Night	27% 10% 32% 26% 5%	508
	11th to 20th	Night	25% 7% 29% 33% 6% 1	374
	21st to end	Night	25% 9% 31% 28% 7%	411
June	1st to 10th	Night	25% 6% 29% 33% 7%	380
	11th to 20th	Night	22% 4 26% 34% 14%	380
	21st to end	Night	23% 6% 25% 33% 12% 1	380
July	1st to 10th	Night	16% 5% 29% 38% 12%	370
	11th to 20th	Night	18% 4 23% 41% 13% 1	368
	21st to end	Night	15% 5% 23% 43% 14%	416
August	1st to 10th	Night	17% 5% 15% 42% 20% 1	378
	11th to 20th	Night	17% 5% 21% 38% 17% 1	537
	21st to end	Night	18% 6% 26% 32% 17% 1	768
September	1st to 10th	Night	22% 4 25% 34% 13% 1	760
	11th to 20th	Night	20% 6% 21% 32% 20% 1	760
	21st to end	Night	21% 6% 28% 31% 14% 1	760
October	1st to 10th	Night	22% 10% 26% 33% 9%	760
	11th to 20th	Night	29% 10% 26% 26% 9% 1	760
	21st to end	Night	31% 11% 31% 23% 4	836
November	1st to 10th	Night	28% 12% 27% 26% 7% 1	780
	11th to 20th	Night	26% 14% 29% 22% 9% 1	800
	21st to end	Night	34% 14% 25% 21% 6%	850
December	1st to 10th	Night	31% 13% 26% 22% 7%	878
	11th to 20th	Night	27% 17% 29% 20% 6%	850
	21st to end	Night	36% 14% 28% 18% 4	877

Page generated at 2024-12-03 06:45:12. Version ac07

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