Lasqueti Island Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lasqueti Island Observatory clear sky chart from 2005-11-06 to 2026-01-02.

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	17% 9% 3 7% 5% 5% 4 3 5% 6% 35%	131369
	Night	22% 10% 3 8% 5% 4 4 3 5% 6% 29%	128676
Transparency	Day	48% 9% 16% 19% 7% 1	131068
	Night	55% 8% 15% 16% 6% 1	128554
Seeing	Day	20% 6% 18% 25% 23% 8%	17038
	Night	26% 6% 17% 24% 21% 7%	25146

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	34% 14% 4 9% 5% 5% 5% 4 5% 5% 9%	3186
	11th to 20th	Day	19% 11% 5% 11% 8% 6% 5% 4 6% 7% 20%	3159
	21st to end	Day	33% 15% 4 8% 5% 4 4 3 3 4 17%	3876
February	1st to 10th	Day	27% 15% 4 10% 6% 5% 5% 3 5% 4 15%	1800
	11th to 20th	Day	24% 12% 4 9% 6% 6% 6% 4 4 5% 21%	1755
	21st to end	Day	22% 12% 5% 8% 7% 6% 5% 4 5% 6% 21%	1485
March	1st to 10th	Day	18% 18% 6% 10% 6% 5% 6% 4 5% 5% 18%	4736
	11th to 20th	Day	18% 13% 4 9% 6% 6% 6% 4 5% 5% 25%	5000
	21st to end	Day	24% 13% 4 11% 7% 6% 5% 3 4 6% 18%	5524
April	1st to 10th	Day	21% 13% 4 8% 6% 5% 4 5% 4 7% 23%	2400
	11th to 20th	Day	17% 10% 4 8% 6% 5% 4 4 5% 6% 31%	2543
	21st to end	Day	18% 10% 3 8% 5% 5% 3 3 5% 6% 33%	2609
May	1st to 10th	Day	10% 8% 3 8% 5% 4 5% 3 5% 6% 44%	6320
	11th to 20th	Day	14% 8% 3 7% 4 5% 5% 4 6% 10% 34%	6277
	21st to end	Day	16% 8% 3 8% 6% 6% 6% 4 5% 7% 31%	7287
June	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 7% 7% 33%	3000
	11th to 20th	Day	11% 7% 3 8% 5% 6% 6% 4 7% 9% 34%	3000
	21st to end	Day	11% 7% 3 7% 5% 5% 4 4 6% 8% 41%	3000
July	1st to 10th	Day	7% 3 1 4 3 3 3 3 4 6% 63%	6780
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 5% 73%	6780
	21st to end	Day	5% 4 1 4 3 4 3 2 4 6% 65%	7222
August	1st to 10th	Day	5% 3 1 2 2 3 2 2 4 6% 71%	4397
	11th to 20th	Day	11% 6% 3 5% 4 4 4 4 6% 9% 43%	4156
	21st to end	Day	12% 6% 2 5% 4 4 4 3 5% 6% 47%	4642
September	1st to 10th	Day	9% 5% 3 5% 3 4 4 3 6% 7% 51%	2400
	11th to 20th	Day	15% 8% 3 7% 4 5% 4 3 5% 6% 40%	2329
	21st to end	Day	21% 9% 3 7% 4 4 4 3 5% 6% 34%	2150
October	1st to 10th	Day	22% 10% 3 8% 6% 5% 4 3 5% 6% 27%	3280
	11th to 20th	Day	27% 10% 3 8% 5% 5% 5% 3 5% 5% 24%	3261
	21st to end	Day	24% 13% 4 9% 5% 5% 5% 4 6% 6% 20%	3250
November	1st to 10th	Day	31% 12% 4 10% 5% 5% 5% 3 5% 5% 16%	1648
	11th to 20th	Day	27% 14% 5% 10% 6% 4 4 3 5% 4 19%	1680
	21st to end	Day	31% 13% 5% 9% 6% 5% 4 4 4 5% 14%	1680
December	1st to 10th	Day	22% 14% 5% 10% 6% 4 5% 4 6% 7% 17%	2467
	11th to 20th	Day	39% 14% 4 10% 5% 5% 5% 2 3 3 10%	2715
	21st to end	Day	36% 16% 4 10% 6% 4 4 3 4 4 9%	3575
January	1st to 10th	Night	32% 15% 5% 11% 6% 4 4 4 3 4 11%	6781
	11th to 20th	Night	20% 9% 3 9% 6% 6% 5% 4 6% 8% 25%	6739
	21st to end	Night	34% 12% 4 8% 5% 4 4 3 4 5% 19%	7057
February	1st to 10th	Night	27% 13% 4 9% 5% 5% 4 3 4 5% 20%	2600
	11th to 20th	Night	24% 11% 4 8% 4 5% 4 3 5% 6% 27%	2532
	21st to end	Night	25% 11% 3 9% 5% 4 5% 4 4 5% 23%	2145
March	1st to 10th	Night	24% 13% 4 7% 4 4 5% 4 5% 6% 24%	5150
	11th to 20th	Night	18% 10% 3 9% 6% 5% 6% 4 6% 6% 28%	4999
	21st to end	Night	29% 13% 4 10% 6% 5% 4 3 4 4 18%	5451
April	1st to 10th	Night	19% 11% 3 9% 7% 6% 5% 4 5% 7% 24%	2000
	11th to 20th	Night	16% 10% 3 9% 6% 5% 4 4 5% 7% 31%	1803
	21st to end	Night	19% 9% 3 7% 6% 5% 6% 3 7% 6% 30%	1790
May	1st to 10th	Night	13% 8% 3 6% 4 4 4 3 5% 5% 45%	3640
	11th to 20th	Night	14% 8% 3 8% 5% 4 4 4 7% 8% 35%	3616
	21st to end	Night	17% 11% 4 11% 6% 5% 5% 4 5% 6% 26%	3572
June	1st to 10th	Night	15% 9% 3 8% 5% 4 6% 4 6% 5% 35%	1400
	11th to 20th	Night	12% 8% 4 8% 7% 6% 6% 5% 6% 7% 32%	1400
	21st to end	Night	10% 7% 4 7% 5% 5% 4 4 6% 8% 41%	1400
July	1st to 10th	Night	6% 4 2 5% 3 4 4 3 5% 7% 58%	3180
	11th to 20th	Night	2 2 1 2 2 2 2 2 4 7% 74%	3180
	21st to end	Night	4 4 1 4 4 3 3 3 5% 7% 62%	3621
August	1st to 10th	Night	5% 3 1 2 2 2 2 2 4 5% 72%	2754
	11th to 20th	Night	12% 6% 2 7% 5% 4 5% 4 6% 8% 42%	2902
	21st to end	Night	11% 6% 3 7% 5% 5% 5% 3 4 6% 46%	3267
September	1st to 10th	Night	7% 4 2 5% 4 4 4 3 4 7% 57%	2000
	11th to 20th	Night	16% 6% 3 7% 5% 4 3 4 5% 6% 42%	2070
	21st to end	Night	20% 8% 3 6% 4 3 4 3 5% 6% 38%	2250
October	1st to 10th	Night	21% 9% 3 8% 5% 4 5% 3 5% 6% 31%	3920
	11th to 20th	Night	26% 9% 3 7% 4 4 5% 3 5% 6% 28%	3897
	21st to end	Night	24% 10% 4 9% 5% 4 4 3 5% 6% 26%	4549
November	1st to 10th	Night	31% 11% 3 9% 5% 5% 4 3 4 5% 18%	2870
	11th to 20th	Night	28% 13% 4 8% 6% 4 4 4 4 4 20%	2940
	21st to end	Night	29% 12% 4 9% 6% 4 4 3 4 5% 19%	2940
December	1st to 10th	Night	24% 13% 4 9% 6% 6% 5% 3 5% 7% 18%	4928
	11th to 20th	Night	38% 17% 5% 9% 4 4 3 3 3 4 9%	5710
	21st to end	Night	34% 16% 4 9% 5% 5% 4 3 3 4 12%	7623

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	72% 10% 8% 9% 2	3186
	11th to 20th	Day	57% 12% 14% 14% 3	3180
	21st to end	Day	71% 7% 11% 10% 1	3876
February	1st to 10th	Day	70% 10% 7% 9% 3 1	1800
	11th to 20th	Day	64% 9% 10% 13% 4 1	1764
	21st to end	Day	62% 8% 14% 10% 4 1	1485
March	1st to 10th	Day	64% 9% 11% 11% 5%	4736
	11th to 20th	Day	58% 8% 10% 19% 4	5000
	21st to end	Day	66% 9% 14% 9% 2	5524
April	1st to 10th	Day	59% 10% 15% 12% 4	2400
	11th to 20th	Day	52% 8% 12% 16% 10% 2	2543
	21st to end	Day	51% 9% 13% 18% 8% 1	2609
May	1st to 10th	Day	40% 7% 17% 23% 12% 1	6320
	11th to 20th	Day	43% 11% 20% 22% 3	6280
	21st to end	Day	50% 10% 20% 16% 5%	7288
June	1st to 10th	Day	47% 11% 18% 16% 6% 2	3000
	11th to 20th	Day	45% 12% 20% 18% 5%	3000
	21st to end	Day	42% 10% 20% 20% 8% 1	3000
July	1st to 10th	Day	23% 7% 20% 26% 19% 5%	6706
	11th to 20th	Day	14% 6% 22% 37% 19% 3	6699
	21st to end	Day	21% 6% 32% 28% 11% 2	7018
August	1st to 10th	Day	17% 6% 15% 48% 13% 1	4380
	11th to 20th	Day	37% 10% 27% 17% 8% 1	4195
	21st to end	Day	37% 9% 20% 24% 9% 1	4641
September	1st to 10th	Day	33% 11% 20% 24% 12% 2	2400
	11th to 20th	Day	44% 10% 16% 18% 11% 1	2329
	21st to end	Day	50% 9% 16% 16% 9%	2150
October	1st to 10th	Day	55% 10% 14% 17% 5%	3280
	11th to 20th	Day	62% 6% 12% 17% 4	3261
	21st to end	Day	64% 8% 12% 12% 4	3250
November	1st to 10th	Day	70% 7% 9% 9% 4	1648
	11th to 20th	Day	67% 8% 10% 10% 4 1	1680
	21st to end	Day	71% 8% 9% 7% 4	1680
December	1st to 10th	Day	63% 9% 13% 12% 2 1	2467
	11th to 20th	Day	80% 6% 7% 5% 2	2718
	21st to end	Day	78% 6% 10% 5% 1	3575
January	1st to 10th	Night	73% 7% 9% 8% 2	6781
	11th to 20th	Night	53% 10% 18% 16% 3	6780
	21st to end	Night	67% 7% 11% 14% 2	7057
February	1st to 10th	Night	66% 8% 10% 10% 5% 1	2600
	11th to 20th	Night	58% 10% 13% 13% 6% 1	2534
	21st to end	Night	62% 7% 12% 13% 5% 1	2145
March	1st to 10th	Night	58% 8% 13% 15% 6%	5150
	11th to 20th	Night	52% 10% 11% 23% 3	5000
	21st to end	Night	67% 9% 11% 11% 2	5451
April	1st to 10th	Night	59% 8% 15% 16% 3	2000
	11th to 20th	Night	51% 8% 12% 20% 8% 2	1803
	21st to end	Night	51% 9% 14% 18% 7% 1	1790
May	1st to 10th	Night	39% 6% 15% 29% 12%	3637
	11th to 20th	Night	44% 8% 22% 21% 4	3616
	21st to end	Night	58% 8% 16% 16% 3	3572
June	1st to 10th	Night	49% 9% 16% 17% 7% 2	1400
	11th to 20th	Night	50% 9% 19% 18% 5%	1400
	21st to end	Night	41% 8% 19% 22% 7% 2	1400
July	1st to 10th	Night	26% 7% 20% 24% 18% 5%	3145
	11th to 20th	Night	13% 5% 24% 38% 19% 2	3138
	21st to end	Night	22% 6% 30% 27% 14% 2	3520
August	1st to 10th	Night	16% 5% 12% 43% 23% 1	2746
	11th to 20th	Night	39% 9% 26% 16% 9% 2	2929
	21st to end	Night	38% 7% 20% 26% 8% 1	3267
September	1st to 10th	Night	28% 8% 17% 31% 13% 3	2000
	11th to 20th	Night	41% 8% 14% 18% 16% 2	2070
	21st to end	Night	47% 8% 17% 18% 8% 2	2250
October	1st to 10th	Night	52% 8% 18% 16% 6%	3920
	11th to 20th	Night	56% 7% 14% 19% 3	3897
	21st to end	Night	57% 8% 17% 14% 4	4549
November	1st to 10th	Night	67% 9% 10% 9% 4 1	2870
	11th to 20th	Night	67% 8% 12% 9% 3 1	2940
	21st to end	Night	67% 9% 9% 10% 4 1	2940
December	1st to 10th	Night	64% 8% 14% 11% 2	4928
	11th to 20th	Night	78% 6% 8% 5% 2	5706
	21st to end	Night	73% 8% 10% 7% 2	7623

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	37% 10% 22% 18% 7% 5%	202
	11th to 20th	Day	36% 9% 22% 21% 13%	200
	21st to end	Day	35% 6% 19% 23% 12% 6%	295
February	1st to 10th	Day	32% 10% 24% 18% 16% 1	400
	11th to 20th	Day	28% 5% 25% 25% 13% 3	395
	21st to end	Day	24% 14% 25% 20% 13% 3	331
March	1st to 10th	Day	25% 9% 19% 24% 20% 3	482
	11th to 20th	Day	26% 8% 20% 22% 20% 4	500
	21st to end	Day	28% 7% 24% 24% 13% 3	550
April	1st to 10th	Day	24% 9% 24% 24% 15% 4	500
	11th to 20th	Day	22% 7% 23% 26% 14% 8%	492
	21st to end	Day	19% 7% 22% 28% 19% 6%	500
May	1st to 10th	Day	13% 6% 17% 30% 28% 6%	503
	11th to 20th	Day	16% 4 13% 30% 28% 9%	528
	21st to end	Day	13% 3 18% 31% 27% 7%	736
June	1st to 10th	Day	17% 5% 18% 29% 24% 7%	730
	11th to 20th	Day	11% 4 23% 28% 28% 7%	730
	21st to end	Day	13% 2 17% 28% 30% 10%	730
July	1st to 10th	Day	12% 2 12% 28% 34% 13%	721
	11th to 20th	Day	5% 3 13% 31% 36% 12%	718
	21st to end	Day	5% 2 9% 27% 40% 18%	729
August	1st to 10th	Day	8% 2 9% 20% 38% 22%	527
	11th to 20th	Day	8% 3 10% 28% 34% 17%	517
	21st to end	Day	12% 3 14% 25% 35% 11%	583
September	1st to 10th	Day	10% 4 14% 29% 32% 12%	530
	11th to 20th	Day	19% 4 15% 26% 25% 12%	530
	21st to end	Day	23% 6% 19% 27% 18% 7%	530
October	1st to 10th	Day	26% 4 20% 22% 19% 9%	530
	11th to 20th	Day	31% 6% 19% 19% 17% 8%	530
	21st to end	Day	30% 11% 20% 23% 11% 4	447
November	1st to 10th	Day	31% 8% 32% 19% 9% 1	220
	11th to 20th	Day	35% 10% 15% 20% 14% 5%	220
	21st to end	Day	42% 10% 17% 15% 12% 5%	220
December	1st to 10th	Day	35% 11% 20% 15% 14% 5%	220
	11th to 20th	Day	36% 14% 18% 20% 11% 1	220
	21st to end	Day	40% 8% 25% 19% 6% 1	242
January	1st to 10th	Night	39% 10% 19% 18% 11% 3	905
	11th to 20th	Night	35% 7% 18% 17% 20% 2	900
	21st to end	Night	36% 5% 19% 18% 16% 5%	941
February	1st to 10th	Night	32% 7% 19% 24% 15% 3	800
	11th to 20th	Night	27% 6% 20% 26% 20% 2	784
	21st to end	Night	30% 9% 18% 23% 16% 4	660
March	1st to 10th	Night	26% 7% 22% 23% 16% 6%	800
	11th to 20th	Night	28% 9% 19% 23% 17% 5%	800
	21st to end	Night	28% 6% 17% 25% 17% 6%	880
April	1st to 10th	Night	24% 6% 19% 26% 20% 6%	800
	11th to 20th	Night	21% 6% 20% 29% 20% 5%	615
	21st to end	Night	22% 5% 18% 29% 21% 5%	590
May	1st to 10th	Night	15% 3 20% 28% 27% 8%	400
	11th to 20th	Night	18% 6% 12% 25% 30% 8%	394
	21st to end	Night	13% 5% 16% 32% 27% 8%	433
June	1st to 10th	Night	18% 6% 14% 35% 24% 5%	400
	11th to 20th	Night	16% 4 16% 32% 24% 8%	400
	21st to end	Night	13% 2 14% 32% 33% 8%	400
July	1st to 10th	Night	12% 1 13% 26% 34% 14%	390
	11th to 20th	Night	6% 2 14% 31% 35% 12%	388
	21st to end	Night	5% 1 9% 27% 42% 16%	438
August	1st to 10th	Night	8% 2 6% 24% 40% 20%	478
	11th to 20th	Night	8% 2 5% 28% 43% 13%	594
	21st to end	Night	11% 3 12% 25% 39% 10%	669
September	1st to 10th	Night	10% 1 10% 30% 34% 15%	800
	11th to 20th	Night	18% 4 13% 18% 30% 18%	800
	21st to end	Night	23% 4 17% 23% 25% 8%	800
October	1st to 10th	Night	21% 5% 13% 26% 25% 10%	800
	11th to 20th	Night	30% 5% 14% 22% 21% 8%	800
	21st to end	Night	31% 7% 18% 24% 15% 4	880
November	1st to 10th	Night	36% 8% 19% 23% 13% 1	820
	11th to 20th	Night	36% 7% 18% 22% 13% 4	840
	21st to end	Night	35% 8% 18% 22% 14% 4	840
December	1st to 10th	Night	32% 7% 17% 21% 18% 4	912
	11th to 20th	Night	43% 8% 18% 20% 10% 1	950
	21st to end	Night	37% 10% 24% 19% 8% 2	1045

Page generated at 2025-12-29 22:14:10. Version ac07

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