Twillingate Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Twillingate Astronomical Observatory clear sky chart from 2005-11-06 to 2026-10-29.

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	20% 14% 5% 10% 6% 5% 4 3 4 6% 24%	150727
	Night	20% 15% 5% 13% 7% 5% 4 3 4 5% 19%	141701
Transparency	Day	64% 3 11% 16% 5%	154155
	Night	69% 3 10% 13% 5%	146374
Seeing	Day	30% 10% 27% 22% 9% 2	20953
	Night	31% 11% 27% 22% 8% 1	27573

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	21% 22% 6% 19% 6% 4 3 2 3 3 10%	4122
	11th to 20th	Day	19% 19% 7% 20% 9% 5% 3 2 2 2 11%	4527
	21st to end	Day	9% 17% 6% 17% 17% 11% 4 2 3 3 11%	5157
February	1st to 10th	Day	18% 14% 5% 17% 15% 5% 5% 3 4 4 10%	1680
	11th to 20th	Day	19% 19% 5% 12% 10% 5% 4 4 3 4 13%	1877
	21st to end	Day	14% 14% 5% 12% 9% 9% 6% 5% 4 5% 19%	1730
March	1st to 10th	Day	15% 12% 4 15% 14% 7% 5% 4 4 4 16%	4574
	11th to 20th	Day	20% 15% 6% 11% 9% 6% 4 3 4 4 16%	4982
	21st to end	Day	26% 16% 6% 11% 6% 3 3 3 4 4 20%	5774
April	1st to 10th	Day	18% 17% 5% 9% 6% 4 4 4 5% 6% 21%	2524
	11th to 20th	Day	21% 14% 5% 8% 5% 3 4 3 5% 6% 27%	2701
	21st to end	Day	20% 18% 5% 9% 5% 4 3 3 4 5% 25%	2730
May	1st to 10th	Day	22% 16% 6% 9% 5% 5% 4 3 4 5% 19%	7912
	11th to 20th	Day	24% 14% 6% 10% 5% 4 4 3 5% 5% 22%	8593
	21st to end	Day	23% 17% 5% 7% 3 3 3 3 4 5% 26%	9682
June	1st to 10th	Day	29% 14% 3 7% 5% 4 4 3 4 5% 21%	3150
	11th to 20th	Day	25% 11% 3 7% 5% 5% 4 3 5% 6% 25%	3150
	21st to end	Day	21% 11% 3 7% 5% 4 5% 4 5% 7% 28%	3150
July	1st to 10th	Day	19% 10% 3 8% 4 5% 4 4 5% 7% 31%	8850
	11th to 20th	Day	15% 7% 4 9% 6% 5% 5% 4 6% 8% 31%	8850
	21st to end	Day	20% 10% 3 7% 4 4 4 3 5% 7% 34%	9035
August	1st to 10th	Day	20% 14% 4 8% 5% 4 4 3 4 6% 25%	6484
	11th to 20th	Day	19% 9% 4 8% 4 4 4 3 5% 6% 34%	5959
	21st to end	Day	17% 8% 2 6% 4 4 3 3 5% 8% 39%	6594
September	1st to 10th	Day	20% 7% 3 7% 4 4 4 3 6% 7% 35%	2538
	11th to 20th	Day	25% 10% 3 7% 4 4 4 4 4 6% 28%	2310
	21st to end	Day	19% 10% 3 7% 4 4 5% 4 5% 8% 32%	2310
October	1st to 10th	Day	21% 13% 3 7% 5% 4 4 3 3 5% 31%	2247
	11th to 20th	Day	22% 17% 4 8% 4 3 4 3 4 7% 23%	1929
	21st to end	Day	26% 17% 5% 7% 4 4 4 2 4 6% 19%	2052
November	1st to 10th	Day	24% 21% 5% 8% 4 4 4 3 4 5% 18%	1818
	11th to 20th	Day	23% 18% 7% 9% 6% 4 3 3 4 5% 19%	1633
	21st to end	Day	25% 18% 7% 13% 3 3 3 4 4 3 16%	1470
December	1st to 10th	Day	16% 13% 6% 18% 6% 4 4 4 4 5% 20%	2360
	11th to 20th	Day	19% 17% 7% 20% 7% 4 3 2 3 5% 12%	2698
	21st to end	Day	20% 16% 8% 26% 7% 4 4 2 3 2 8%	3575
January	1st to 10th	Night	19% 20% 7% 19% 9% 4 4 2 3 3 8%	8802
	11th to 20th	Night	15% 20% 7% 20% 9% 5% 4 3 3 3 10%	8371
	21st to end	Night	8% 15% 5% 17% 14% 11% 6% 3 4 4 13%	9056
February	1st to 10th	Night	18% 15% 6% 20% 14% 6% 4 2 3 2 11%	2940
	11th to 20th	Night	20% 20% 6% 12% 10% 5% 4 3 4 4 13%	2625
	21st to end	Night	15% 13% 5% 13% 9% 6% 5% 4 5% 5% 20%	2076
March	1st to 10th	Night	18% 14% 4 17% 9% 5% 4 3 4 5% 18%	5486
	11th to 20th	Night	19% 15% 5% 14% 7% 7% 5% 4 4 5% 15%	5197
	21st to end	Night	24% 15% 5% 11% 5% 4 4 3 4 5% 19%	5386
April	1st to 10th	Night	22% 17% 7% 10% 5% 4 3 3 3 5% 20%	2095
	11th to 20th	Night	24% 15% 6% 9% 4 3 3 3 4 5% 25%	1868
	21st to end	Night	25% 17% 5% 6% 5% 4 3 3 4 5% 24%	1890
May	1st to 10th	Night	31% 16% 5% 8% 4 4 3 2 4 5% 18%	4999
	11th to 20th	Night	24% 17% 7% 10% 4 4 3 3 4 5% 20%	4297
	21st to end	Night	27% 16% 5% 7% 4 3 4 2 4 5% 22%	4524
June	1st to 10th	Night	31% 13% 4 8% 4 3 4 3 4 5% 19%	1470
	11th to 20th	Night	29% 11% 3 8% 4 4 4 3 4 5% 24%	1470
	21st to end	Night	24% 13% 4 8% 3 4 4 3 5% 6% 25%	1470
July	1st to 10th	Night	21% 12% 4 8% 4 4 4 3 5% 6% 27%	4139
	11th to 20th	Night	14% 11% 6% 9% 5% 5% 5% 3 6% 7% 29%	4140
	21st to end	Night	20% 12% 4 8% 5% 4 5% 3 5% 7% 27%	5072
August	1st to 10th	Night	18% 15% 4 9% 5% 4 4 3 5% 6% 26%	3686
	11th to 20th	Night	18% 10% 3 8% 5% 4 5% 4 5% 6% 32%	4105
	21st to end	Night	17% 7% 3 7% 4 5% 5% 4 6% 8% 35%	4553
September	1st to 10th	Night	23% 8% 2 6% 4 3 4 3 5% 7% 35%	2079
	11th to 20th	Night	25% 11% 3 7% 4 4 4 3 4 5% 29%	2310
	21st to end	Night	21% 13% 3 9% 4 3 3 3 5% 6% 31%	2310
October	1st to 10th	Night	24% 12% 2 8% 4 4 4 3 5% 6% 27%	2373
	11th to 20th	Night	25% 16% 3 7% 4 5% 4 3 5% 6% 22%	2688
	21st to end	Night	28% 19% 3 7% 3 3 3 2 4 5% 22%	2965
November	1st to 10th	Night	25% 21% 4 9% 6% 4 4 3 5% 5% 15%	2699
	11th to 20th	Night	26% 19% 7% 8% 5% 4 3 3 5% 5% 14%	2984
	21st to end	Night	23% 20% 9% 11% 6% 4 3 3 4 5% 13%	3150
December	1st to 10th	Night	15% 15% 6% 15% 7% 5% 5% 3 4 4 21%	5050
	11th to 20th	Night	24% 17% 8% 18% 7% 4 3 2 2 4 11%	5731
	21st to end	Night	18% 16% 9% 25% 7% 4 3 2 3 3 11%	7645

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	82% 2 7% 9% 1	4123
	11th to 20th	Day	81% 4 5% 6% 5%	4556
	21st to end	Day	80% 2 6% 7% 4 1	5157
February	1st to 10th	Day	77% 4 8% 6% 5% 1	1680
	11th to 20th	Day	76% 3 8% 9% 4	1884
	21st to end	Day	68% 4 7% 13% 8%	1730
March	1st to 10th	Day	71% 3 6% 12% 6% 1	4578
	11th to 20th	Day	73% 3 8% 10% 5% 2	4982
	21st to end	Day	70% 2 7% 13% 7%	5774
April	1st to 10th	Day	65% 3 9% 15% 8% 1	2524
	11th to 20th	Day	60% 2 10% 19% 8% 1	2701
	21st to end	Day	65% 3 7% 16% 9% 1	2730
May	1st to 10th	Day	69% 2 12% 13% 4 1	7925
	11th to 20th	Day	66% 2 10% 14% 7%	8597
	21st to end	Day	62% 2 11% 19% 6%	9683
June	1st to 10th	Day	66% 3 10% 16% 5%	3150
	11th to 20th	Day	60% 4 12% 19% 5% 1	3150
	21st to end	Day	56% 5% 12% 19% 7% 1	3150
July	1st to 10th	Day	54% 2 15% 23% 6%	8775
	11th to 20th	Day	52% 3 15% 24% 5%	8768
	21st to end	Day	51% 3 15% 26% 5%	8837
August	1st to 10th	Day	61% 4 16% 17% 3	6470
	11th to 20th	Day	53% 2 18% 18% 7% 2	5998
	21st to end	Day	45% 3 18% 27% 7%	6594
September	1st to 10th	Day	49% 4 13% 25% 8% 1	2538
	11th to 20th	Day	57% 3 15% 18% 6%	2310
	21st to end	Day	52% 4 18% 19% 7%	2310
October	1st to 10th	Day	61% 3 11% 18% 6%	3601
	11th to 20th	Day	66% 3 10% 16% 5%	3064
	21st to end	Day	65% 3 10% 13% 8% 1	3263
November	1st to 10th	Day	70% 4 10% 10% 4	1818
	11th to 20th	Day	69% 4 10% 11% 5% 1	1633
	21st to end	Day	72% 5% 9% 9% 5%	1470
December	1st to 10th	Day	66% 3 9% 14% 8%	2360
	11th to 20th	Day	78% 3 13% 4 2	2697
	21st to end	Day	85% 2 6% 6% 1	3575
January	1st to 10th	Night	82% 2 7% 7% 2	8802
	11th to 20th	Night	79% 5% 5% 7% 4	8417
	21st to end	Night	75% 3 8% 7% 6% 1	9056
February	1st to 10th	Night	81% 3 6% 6% 3	2940
	11th to 20th	Night	76% 3 8% 9% 3	2629
	21st to end	Night	65% 5% 7% 15% 7% 1	2076
March	1st to 10th	Night	69% 3 9% 12% 5% 2	5495
	11th to 20th	Night	72% 3 9% 9% 6% 1	5198
	21st to end	Night	69% 2 9% 14% 6%	5386
April	1st to 10th	Night	68% 3 5% 14% 10%	2095
	11th to 20th	Night	63% 2 10% 18% 7% 1	1868
	21st to end	Night	64% 3 8% 16% 8% 1	1890
May	1st to 10th	Night	71% 2 12% 12% 3	5004
	11th to 20th	Night	70% 1 11% 14% 4	4298
	21st to end	Night	67% 2 9% 18% 5%	4525
June	1st to 10th	Night	67% 4 10% 13% 6%	1470
	11th to 20th	Night	63% 3 12% 16% 5%	1470
	21st to end	Night	61% 4 11% 17% 6% 1	1470
July	1st to 10th	Night	58% 3 15% 22% 3	4106
	11th to 20th	Night	55% 3 13% 22% 7%	4098
	21st to end	Night	59% 2 13% 22% 4	4956
August	1st to 10th	Night	60% 4 13% 20% 4	3675
	11th to 20th	Night	54% 3 18% 16% 8% 1	4132
	21st to end	Night	49% 2 17% 24% 7%	4552
September	1st to 10th	Night	51% 3 13% 24% 9% 1	2079
	11th to 20th	Night	58% 4 12% 18% 8%	2310
	21st to end	Night	55% 4 14% 20% 7%	2310
October	1st to 10th	Night	63% 3 13% 15% 5%	3802
	11th to 20th	Night	65% 3 13% 13% 5%	4289
	21st to end	Night	64% 2 13% 13% 6% 1	4715
November	1st to 10th	Night	72% 4 8% 11% 5%	2699
	11th to 20th	Night	72% 5% 9% 12% 2	2984
	21st to end	Night	75% 5% 8% 8% 4	3150
December	1st to 10th	Night	67% 3 6% 15% 9%	5050
	11th to 20th	Night	80% 3 10% 4 3	5733
	21st to end	Night	81% 3 6% 9% 2	7645

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% 14% 33% 17% 4 1	430
	11th to 20th	Day	28% 17% 34% 17% 4	430
	21st to end	Day	30% 23% 29% 16% 2	473
February	1st to 10th	Day	26% 20% 34% 15% 5%	430
	11th to 20th	Day	28% 21% 32% 15% 3 1	426
	21st to end	Day	21% 19% 37% 16% 5% 2	355
March	1st to 10th	Day	27% 13% 37% 16% 5% 1	430
	11th to 20th	Day	28% 16% 25% 19% 10% 2	430
	21st to end	Day	33% 13% 29% 18% 6% 2	517
April	1st to 10th	Day	29% 14% 33% 18% 5% 1	544
	11th to 20th	Day	31% 9% 27% 24% 7% 2	739
	21st to end	Day	32% 8% 26% 23% 9% 1	750
May	1st to 10th	Day	34% 8% 24% 21% 10% 3	753
	11th to 20th	Day	29% 5% 27% 23% 12% 3	774
	21st to end	Day	35% 6% 23% 26% 9% 1	845
June	1st to 10th	Day	37% 6% 22% 23% 9% 3	780
	11th to 20th	Day	31% 6% 21% 26% 13% 2	780
	21st to end	Day	26% 3 23% 28% 15% 4	780
July	1st to 10th	Day	27% 3 23% 32% 11% 3	770
	11th to 20th	Day	23% 3 23% 29% 20% 2	768
	21st to end	Day	26% 4 24% 31% 14% 2	850
August	1st to 10th	Day	27% 6% 18% 29% 16% 4	775
	11th to 20th	Day	25% 3 21% 29% 20% 3	767
	21st to end	Day	26% 5% 24% 25% 17% 4	858
September	1st to 10th	Day	26% 8% 25% 26% 12% 3	595
	11th to 20th	Day	34% 9% 25% 24% 7% 1	450
	21st to end	Day	25% 11% 35% 21% 6% 1	450
October	1st to 10th	Day	26% 12% 35% 18% 6% 1	450
	11th to 20th	Day	38% 11% 25% 15% 10% 2	450
	21st to end	Day	33% 14% 26% 19% 6% 2	486
November	1st to 10th	Day	40% 15% 30% 12% 2	425
	11th to 20th	Day	37% 17% 24% 16% 5% 1	430
	21st to end	Day	36% 17% 32% 13% 2	430
December	1st to 10th	Day	29% 16% 32% 17% 6%	430
	11th to 20th	Day	31% 26% 27% 15% 2	430
	21st to end	Day	27% 19% 30% 17% 6% 1	473
January	1st to 10th	Night	29% 18% 30% 18% 5% 1	950
	11th to 20th	Night	29% 17% 35% 14% 5%	950
	21st to end	Night	26% 19% 35% 16% 3	1045
February	1st to 10th	Night	27% 20% 30% 18% 4 1	950
	11th to 20th	Night	32% 17% 31% 15% 3 1	908
	21st to end	Night	23% 14% 36% 19% 7% 1	692
March	1st to 10th	Night	28% 17% 32% 18% 5% 1	840
	11th to 20th	Night	27% 11% 29% 23% 9% 1	686
	21st to end	Night	34% 13% 26% 20% 5% 1	693
April	1st to 10th	Night	31% 13% 30% 19% 6% 1	630
	11th to 20th	Night	32% 9% 29% 20% 9% 1	624
	21st to end	Night	36% 5% 25% 28% 6% 1	630
May	1st to 10th	Night	38% 5% 20% 25% 10% 2	630
	11th to 20th	Night	38% 6% 20% 24% 11% 1	622
	21st to end	Night	35% 5% 25% 25% 9% 1	682
June	1st to 10th	Night	38% 6% 18% 27% 10% 1	630
	11th to 20th	Night	36% 4 19% 27% 13% 2	630
	21st to end	Night	32% 5% 21% 26% 14% 1	630
July	1st to 10th	Night	28% 3 23% 33% 11% 1	616
	11th to 20th	Night	24% 3 26% 35% 11%	612
	21st to end	Night	26% 5% 23% 31% 13% 1	689
August	1st to 10th	Night	25% 4 19% 34% 16% 2	628
	11th to 20th	Night	24% 3 22% 34% 16% 1	622
	21st to end	Night	26% 4 20% 31% 16% 2	693
September	1st to 10th	Night	27% 5% 26% 31% 11%	630
	11th to 20th	Night	32% 9% 25% 28% 6%	630
	21st to end	Night	31% 8% 31% 23% 6% 1	630
October	1st to 10th	Night	35% 8% 28% 22% 6% 1	666
	11th to 20th	Night	36% 10% 23% 22% 9% 1	918
	21st to end	Night	38% 13% 22% 21% 6% 1	1042
November	1st to 10th	Night	37% 15% 28% 16% 3	930
	11th to 20th	Night	38% 12% 27% 16% 5% 1	950
	21st to end	Night	36% 16% 30% 15% 3	950
December	1st to 10th	Night	31% 16% 30% 18% 5% 1	950
	11th to 20th	Night	35% 18% 29% 14% 4	950
	21st to end	Night	27% 19% 28% 18% 6% 1	1045

Page generated at 2026-10-26 05:37:47. Version ac07

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