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 2024-01-14.

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% 9% 4 7% 6% 3 5% 4 5% 6% 33%	74714
	Night	23% 10% 4 7% 6% 3 4 4 5% 6% 29%	75053
Transparency	Day	51% 9% 15% 17% 7% 1	74398
	Night	56% 8% 13% 15% 6% 1	74887
Seeing	Day	20% 5% 18% 25% 23% 9%	14447
	Night	26% 5% 17% 24% 21% 7%	22655

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	36% 13% 5% 8% 5% 3 5% 3 3 4 14%	1329
	11th to 20th	Day	26% 14% 5% 11% 8% 4 4 5% 5% 4 11%	1281
	21st to end	Day	26% 17% 6% 9% 8% 4 6% 5% 5% 4 10%	1540
February	1st to 10th	Day	29% 13% 5% 9% 6% 4 5% 4 5% 4 16%	1620
	11th to 20th	Day	24% 11% 4 8% 7% 4 5% 6% 4 5% 21%	1575
	21st to end	Day	21% 10% 5% 7% 7% 4 6% 5% 5% 7% 23%	1332
March	1st to 10th	Day	23% 12% 4 8% 5% 4 7% 5% 5% 6% 21%	1877
	11th to 20th	Day	24% 12% 4 8% 7% 4 6% 5% 5% 4 22%	1980
	21st to end	Day	23% 10% 4 8% 7% 4 5% 4 5% 5% 25%	2191
April	1st to 10th	Day	21% 11% 5% 7% 7% 4 5% 5% 4 7% 23%	2160
	11th to 20th	Day	18% 10% 5% 7% 7% 4 5% 4 5% 6% 29%	2285
	21st to end	Day	18% 9% 4 7% 6% 4 5% 4 5% 6% 32%	2347
May	1st to 10th	Day	13% 7% 3 6% 6% 4 6% 5% 5% 8% 39%	2520
	11th to 20th	Day	15% 8% 3 5% 6% 4 5% 5% 7% 8% 36%	2477
	21st to end	Day	15% 8% 3 5% 6% 4 6% 6% 6% 7% 37%	2869
June	1st to 10th	Day	17% 7% 4 7% 5% 4 5% 5% 6% 8% 31%	2700
	11th to 20th	Day	12% 6% 3 8% 6% 4 7% 5% 6% 9% 34%	2700
	21st to end	Day	11% 5% 3 6% 6% 4 5% 4 6% 8% 43%	2700
July	1st to 10th	Day	10% 5% 2 5% 5% 3 4 4 4 7% 50%	2700
	11th to 20th	Day	7% 3 3 3 5% 2 4 4 6% 7% 55%	2700
	21st to end	Day	6% 3 2 3 2 2 4 4 4 6% 66%	2880
August	1st to 10th	Day	8% 5% 2 3 3 3 3 4 4 6% 59%	2432
	11th to 20th	Day	6% 4 2 3 3 3 3 4 5% 9% 58%	2298
	21st to end	Day	9% 4 2 5% 5% 3 4 5% 6% 8% 49%	2566
September	1st to 10th	Day	10% 5% 2 4 4 3 4 4 6% 7% 50%	2160
	11th to 20th	Day	15% 8% 3 6% 6% 4 4 4 5% 6% 39%	2097
	21st to end	Day	20% 9% 3 6% 5% 3 4 4 5% 7% 35%	1936
October	1st to 10th	Day	21% 9% 3 6% 5% 3 4 4 5% 7% 31%	1800
	11th to 20th	Day	26% 12% 4 8% 6% 4 4 4 5% 6% 21%	1800
	21st to end	Day	26% 11% 4 8% 6% 3 4 4 5% 6% 22%	1815
November	1st to 10th	Day	31% 11% 5% 9% 6% 3 5% 4 4 5% 17%	1488
	11th to 20th	Day	28% 12% 5% 9% 6% 3 4 3 5% 5% 20%	1520
	21st to end	Day	31% 12% 5% 8% 6% 4 5% 5% 3 6% 15%	1520
December	1st to 10th	Day	26% 15% 6% 9% 6% 2 4 3 5% 5% 18%	1392
	11th to 20th	Day	34% 15% 4 10% 8% 3 6% 4 2 3 9%	1685
	21st to end	Day	34% 17% 4 8% 8% 3 5% 4 3 5% 9%	2442
January	1st to 10th	Night	34% 13% 5% 8% 7% 3 4 4 3 5% 15%	2836
	11th to 20th	Night	30% 14% 4 9% 6% 3 4 4 4 6% 15%	2751
	21st to end	Night	28% 14% 5% 8% 7% 4 4 4 4 5% 16%	2813
February	1st to 10th	Night	29% 12% 4 8% 6% 4 4 4 4 5% 21%	2340
	11th to 20th	Night	24% 11% 4 7% 5% 3 4 4 5% 7% 27%	2272
	21st to end	Night	25% 10% 3 8% 6% 3 6% 5% 4 5% 25%	1924
March	1st to 10th	Night	23% 10% 5% 7% 5% 4 6% 6% 6% 6% 23%	2078
	11th to 20th	Night	24% 9% 3 8% 8% 4 5% 4 6% 7% 24%	1979
	21st to end	Night	22% 12% 4 9% 7% 3 5% 5% 5% 6% 22%	2165
April	1st to 10th	Night	20% 11% 3 8% 8% 4 5% 5% 5% 7% 24%	1800
	11th to 20th	Night	18% 10% 3 8% 7% 4 5% 6% 5% 7% 28%	1621
	21st to end	Night	19% 8% 3 6% 6% 4 6% 5% 6% 7% 29%	1612
May	1st to 10th	Night	15% 7% 4 5% 5% 5% 5% 5% 5% 6% 39%	1440
	11th to 20th	Night	15% 9% 3 7% 6% 3 5% 6% 7% 8% 32%	1416
	21st to end	Night	14% 7% 4 7% 6% 3 5% 4 6% 8% 34%	1404
June	1st to 10th	Night	15% 8% 4 8% 6% 3 6% 6% 5% 6% 34%	1260
	11th to 20th	Night	14% 8% 4 7% 7% 4 6% 5% 5% 8% 32%	1260
	21st to end	Night	10% 5% 3 5% 6% 3 6% 5% 6% 8% 43%	1260
July	1st to 10th	Night	8% 6% 3 5% 4 3 5% 4 4 7% 51%	1260
	11th to 20th	Night	5% 4 2 4 4 3 5% 4 6% 9% 55%	1260
	21st to end	Night	4 3 2 3 4 2 4 4 4 6% 65%	1437
August	1st to 10th	Night	8% 4 2 3 4 3 3 2 5% 7% 59%	1503
	11th to 20th	Night	5% 3 1 4 4 2 3 5% 6% 8% 59%	1602
	21st to end	Night	9% 5% 2 5% 5% 3 4 5% 6% 8% 48%	1789
September	1st to 10th	Night	7% 4 2 4 5% 3 4 4 4 6% 57%	1800
	11th to 20th	Night	16% 5% 3 6% 5% 3 3 4 5% 6% 42%	1862
	21st to end	Night	19% 8% 3 5% 4 2 4 4 5% 7% 39%	2024
October	1st to 10th	Night	18% 7% 3 6% 5% 3 4 4 5% 6% 41%	2160
	11th to 20th	Night	26% 8% 3 5% 5% 3 4 4 5% 5% 33%	2160
	21st to end	Night	25% 9% 3 7% 6% 3 4 4 4 5% 30%	2538
November	1st to 10th	Night	31% 10% 4 7% 6% 4 4 4 4 5% 19%	2590
	11th to 20th	Night	28% 12% 4 7% 7% 3 4 5% 4 4 21%	2660
	21st to end	Night	30% 10% 5% 7% 7% 4 4 5% 4 5% 19%	2660
December	1st to 10th	Night	27% 13% 5% 7% 7% 4 5% 4 3 5% 21%	2783
	11th to 20th	Night	36% 16% 6% 8% 6% 4 4 3 3 4 10%	3520
	21st to end	Night	35% 16% 5% 8% 6% 3 4 4 3 4 13%	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	74% 7% 8% 7% 4	1329
	11th to 20th	Day	75% 9% 8% 6% 2	1281
	21st to end	Day	75% 9% 7% 6% 2	1540
February	1st to 10th	Day	70% 10% 7% 8% 3 1	1620
	11th to 20th	Day	64% 10% 10% 12% 3	1584
	21st to end	Day	60% 8% 15% 11% 4 2	1332
March	1st to 10th	Day	61% 11% 12% 12% 4	1877
	11th to 20th	Day	64% 9% 10% 13% 3 1	1980
	21st to end	Day	63% 6% 16% 13% 3	2191
April	1st to 10th	Day	59% 10% 15% 12% 4	2160
	11th to 20th	Day	55% 8% 11% 16% 9%	2285
	21st to end	Day	53% 9% 12% 17% 9% 1	2347
May	1st to 10th	Day	44% 11% 16% 21% 7% 1	2520
	11th to 20th	Day	45% 10% 17% 22% 5% 1	2480
	21st to end	Day	45% 11% 18% 21% 5%	2870
June	1st to 10th	Day	49% 11% 17% 16% 5% 2	2700
	11th to 20th	Day	46% 12% 19% 17% 4	2700
	21st to end	Day	40% 10% 20% 21% 9% 1	2700
July	1st to 10th	Day	36% 9% 19% 24% 10% 2	2626
	11th to 20th	Day	27% 11% 22% 30% 9% 1	2619
	21st to end	Day	20% 8% 22% 34% 14% 3	2720
August	1st to 10th	Day	28% 9% 20% 29% 12% 2	2415
	11th to 20th	Day	25% 10% 22% 26% 14% 2	2298
	21st to end	Day	32% 10% 23% 27% 7% 1	2566
September	1st to 10th	Day	34% 11% 18% 24% 11% 2	2160
	11th to 20th	Day	45% 10% 14% 18% 12% 1	2097
	21st to end	Day	49% 9% 16% 17% 9% 1	1936
October	1st to 10th	Day	51% 11% 14% 16% 8%	1800
	11th to 20th	Day	64% 7% 15% 12% 3	1800
	21st to end	Day	63% 8% 12% 11% 6%	1815
November	1st to 10th	Day	69% 8% 9% 10% 4	1488
	11th to 20th	Day	66% 8% 10% 10% 4 1	1520
	21st to end	Day	70% 9% 9% 8% 5%	1520
December	1st to 10th	Day	68% 9% 9% 9% 3 1	1392
	11th to 20th	Day	79% 8% 6% 4 2	1688
	21st to end	Day	76% 7% 9% 5% 2	2442
January	1st to 10th	Night	74% 6% 8% 8% 4	2836
	11th to 20th	Night	71% 9% 12% 6% 2	2751
	21st to end	Night	69% 9% 9% 11% 2	2813
February	1st to 10th	Night	67% 8% 10% 9% 4 1	2340
	11th to 20th	Night	57% 11% 14% 13% 5%	2274
	21st to end	Night	61% 7% 12% 14% 5% 1	1924
March	1st to 10th	Night	59% 9% 14% 13% 5%	2078
	11th to 20th	Night	60% 8% 11% 15% 5% 1	1980
	21st to end	Night	63% 9% 13% 13% 3	2165
April	1st to 10th	Night	60% 7% 14% 16% 3	1800
	11th to 20th	Night	54% 8% 11% 19% 7% 1	1621
	21st to end	Night	52% 9% 13% 18% 8% 1	1612
May	1st to 10th	Night	45% 8% 16% 23% 8%	1440
	11th to 20th	Night	47% 11% 16% 20% 5% 1	1416
	21st to end	Night	48% 9% 18% 19% 5%	1404
June	1st to 10th	Night	51% 9% 15% 17% 6% 2	1260
	11th to 20th	Night	51% 8% 19% 17% 5%	1260
	21st to end	Night	39% 8% 20% 23% 7% 2	1260
July	1st to 10th	Night	34% 9% 18% 24% 13% 2	1225
	11th to 20th	Night	27% 9% 25% 28% 11% 1	1218
	21st to end	Night	19% 8% 17% 34% 17% 4	1357
August	1st to 10th	Night	26% 8% 16% 32% 15% 2	1495
	11th to 20th	Night	22% 9% 25% 25% 15% 3	1602
	21st to end	Night	34% 9% 19% 31% 6% 1	1789
September	1st to 10th	Night	29% 8% 17% 31% 13% 2	1800
	11th to 20th	Night	42% 9% 13% 17% 17% 3	1862
	21st to end	Night	46% 8% 16% 20% 8% 2	2024
October	1st to 10th	Night	45% 8% 17% 20% 9% 1	2160
	11th to 20th	Night	54% 8% 15% 18% 5%	2160
	21st to end	Night	57% 8% 14% 15% 6%	2538
November	1st to 10th	Night	66% 9% 11% 9% 4 1	2590
	11th to 20th	Night	66% 9% 12% 9% 4 1	2660
	21st to end	Night	66% 9% 9% 10% 5% 1	2660
December	1st to 10th	Night	67% 8% 11% 10% 4 1	2783
	11th to 20th	Night	78% 7% 8% 5% 2	3516
	21st to end	Night	73% 8% 10% 7% 2	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	36% 10% 21% 18% 8% 6%	180
	11th to 20th	Day	40% 6% 22% 20% 13%	166
	21st to end	Day	34% 6% 19% 24% 12% 5%	244
February	1st to 10th	Day	35% 10% 25% 16% 13% 1	340
	11th to 20th	Day	30% 5% 26% 25% 13% 2	335
	21st to end	Day	23% 11% 27% 21% 14% 4	280
March	1st to 10th	Day	26% 7% 18% 25% 20% 3	405
	11th to 20th	Day	27% 8% 21% 23% 17% 4	420
	21st to end	Day	27% 7% 23% 25% 14% 4	462
April	1st to 10th	Day	24% 9% 26% 22% 14% 4	420
	11th to 20th	Day	24% 7% 22% 24% 15% 9%	412
	21st to end	Day	19% 7% 24% 28% 17% 5%	420
May	1st to 10th	Day	14% 5% 17% 30% 29% 6%	423
	11th to 20th	Day	16% 3 12% 28% 30% 11%	448
	21st to end	Day	12% 3 16% 32% 29% 8%	631
June	1st to 10th	Day	18% 4 17% 30% 23% 7%	630
	11th to 20th	Day	11% 4 23% 29% 26% 6%	630
	21st to end	Day	12% 2 17% 29% 30% 11%	630
July	1st to 10th	Day	12% 1 12% 27% 33% 14%	621
	11th to 20th	Day	6% 3 13% 30% 36% 12%	618
	21st to end	Day	4 1 8% 26% 42% 19%	626
August	1st to 10th	Day	9% 2 9% 20% 35% 24%	447
	11th to 20th	Day	5% 2 10% 28% 36% 19%	437
	21st to end	Day	11% 4 15% 26% 34% 11%	495
September	1st to 10th	Day	12% 4 15% 31% 28% 10%	450
	11th to 20th	Day	20% 4 13% 26% 24% 13%	450
	21st to end	Day	22% 6% 18% 26% 20% 8%	450
October	1st to 10th	Day	26% 4 18% 21% 21% 10%	450
	11th to 20th	Day	32% 5% 17% 20% 18% 9%	450
	21st to end	Day	28% 10% 22% 25% 11% 4	379
November	1st to 10th	Day	31% 8% 31% 19% 10% 2	180
	11th to 20th	Day	34% 10% 14% 21% 15% 6%	180
	21st to end	Day	40% 9% 18% 16% 12% 5%	180
December	1st to 10th	Day	34% 9% 21% 18% 13% 4	180
	11th to 20th	Day	32% 13% 19% 19% 14% 2	180
	21st to end	Day	38% 10% 25% 21% 5% 2	198
January	1st to 10th	Night	39% 10% 19% 18% 11% 3	850
	11th to 20th	Night	37% 6% 17% 17% 19% 3	817
	21st to end	Night	36% 5% 19% 19% 17% 4	841
February	1st to 10th	Night	34% 7% 20% 23% 14% 3	720
	11th to 20th	Night	27% 6% 21% 26% 19% 2	704
	21st to end	Night	29% 8% 18% 24% 17% 5%	592
March	1st to 10th	Night	26% 6% 22% 23% 16% 7%	720
	11th to 20th	Night	29% 8% 19% 23% 16% 5%	720
	21st to end	Night	28% 6% 17% 26% 18% 7%	792
April	1st to 10th	Night	25% 6% 18% 25% 20% 6%	720
	11th to 20th	Night	23% 4 20% 28% 20% 5%	553
	21st to end	Night	22% 5% 18% 29% 21% 5%	532
May	1st to 10th	Night	15% 2 21% 27% 27% 8%	360
	11th to 20th	Night	19% 5% 11% 24% 32% 9%	354
	21st to end	Night	12% 4 15% 33% 28% 8%	389
June	1st to 10th	Night	19% 4 12% 34% 26% 5%	360
	11th to 20th	Night	17% 4 16% 32% 24% 8%	360
	21st to end	Night	13% 1 14% 31% 33% 8%	360
July	1st to 10th	Night	13% 1 11% 27% 33% 15%	350
	11th to 20th	Night	7% 2 13% 30% 36% 12%	348
	21st to end	Night	5% 1 8% 27% 43% 16%	394
August	1st to 10th	Night	8% 2 7% 24% 39% 20%	429
	11th to 20th	Night	6% 1 4 29% 46% 13%	534
	21st to end	Night	11% 3 12% 25% 39% 10%	601
September	1st to 10th	Night	10% 1 10% 32% 32% 14%	720
	11th to 20th	Night	18% 3 12% 18% 29% 19%	720
	21st to end	Night	22% 3 17% 23% 27% 8%	720
October	1st to 10th	Night	21% 4 13% 25% 26% 11%	720
	11th to 20th	Night	30% 5% 14% 21% 22% 8%	720
	21st to end	Night	31% 7% 18% 24% 15% 5%	792
November	1st to 10th	Night	36% 6% 18% 24% 14% 1	740
	11th to 20th	Night	35% 6% 19% 22% 14% 4	760
	21st to end	Night	36% 7% 18% 22% 14% 4	760
December	1st to 10th	Night	32% 7% 18% 22% 17% 4	818
	11th to 20th	Night	43% 7% 18% 21% 10% 1	850
	21st to end	Night	38% 9% 25% 19% 8% 2	935

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