Blanc-Sablon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blanc-Sablon 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	24% 13% 4 8% 5% 4 4 3 5% 6% 25%	102776
	Night	22% 14% 4 8% 5% 4 4 3 5% 5% 26%	97074
Transparency	Day	59% 7% 13% 16% 6% 1	106166
	Night	59% 6% 12% 16% 7% 1	101794
Seeing	Day	28% 10% 24% 24% 11% 2	18217
	Night	28% 11% 28% 24% 8% 1	24655

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	11% 15% 6% 11% 5% 4 5% 3 4 5% 32%	2216
	11th to 20th	Day	21% 19% 5% 9% 6% 3 3 3 4 5% 22%	2474
	21st to end	Day	8% 10% 4 9% 6% 5% 4 4 6% 10% 34%	2783
February	1st to 10th	Day	12% 16% 4 9% 5% 4 4 3 5% 6% 32%	1520
	11th to 20th	Day	10% 18% 5% 9% 6% 4 5% 3 4 5% 31%	1618
	21st to end	Day	11% 15% 4 9% 4 4 3 3 4 6% 35%	1570
March	1st to 10th	Day	9% 11% 4 10% 5% 6% 6% 4 5% 6% 34%	3114
	11th to 20th	Day	12% 24% 9% 16% 7% 5% 4 2 3 4 14%	3251
	21st to end	Day	25% 15% 4 8% 5% 4 4 3 4 5% 22%	4153
April	1st to 10th	Day	21% 16% 5% 10% 6% 4 5% 3 5% 6% 20%	2280
	11th to 20th	Day	19% 15% 4 8% 5% 4 4 4 4 6% 28%	2385
	21st to end	Day	20% 13% 5% 9% 5% 4 4 3 5% 6% 26%	2547
May	1st to 10th	Day	28% 15% 4 9% 5% 4 5% 3 5% 5% 17%	4425
	11th to 20th	Day	20% 11% 4 9% 5% 5% 4 4 5% 6% 25%	4542
	21st to end	Day	37% 13% 4 7% 4 3 3 3 4 5% 17%	5173
June	1st to 10th	Day	30% 12% 4 9% 6% 4 4 4 5% 6% 18%	2850
	11th to 20th	Day	31% 10% 3 7% 4 4 4 4 5% 7% 21%	3024
	21st to end	Day	30% 11% 3 7% 5% 4 4 4 4 8% 20%	3040
July	1st to 10th	Day	30% 14% 4 8% 4 4 3 4 3 5% 21%	4983
	11th to 20th	Day	32% 12% 3 5% 4 3 3 3 4 5% 26%	4725
	21st to end	Day	23% 9% 2 7% 5% 4 4 4 6% 9% 27%	4815
August	1st to 10th	Day	29% 10% 3 6% 4 4 3 4 6% 8% 23%	4424
	11th to 20th	Day	29% 12% 3 7% 4 4 5% 3 4 6% 24%	4278
	21st to end	Day	22% 9% 3 7% 4 4 4 3 5% 7% 31%	4441
September	1st to 10th	Day	28% 8% 2 6% 4 3 3 3 6% 7% 31%	2280
	11th to 20th	Day	28% 9% 3 7% 4 4 4 3 5% 5% 28%	2166
	21st to end	Day	27% 9% 2 7% 4 4 4 3 5% 6% 29%	2090
October	1st to 10th	Day	26% 10% 2 6% 5% 3 4 2 4 6% 33%	1990
	11th to 20th	Day	27% 11% 3 7% 4 4 3 2 5% 5% 29%	1720
	21st to end	Day	24% 14% 3 6% 3 4 4 2 4 6% 30%	1881
November	1st to 10th	Day	23% 12% 3 6% 4 4 4 3 4 4 33%	1725
	11th to 20th	Day	22% 16% 3 7% 5% 4 3 2 3 4 31%	1418
	21st to end	Day	25% 17% 6% 7% 4 3 2 2 3 5% 26%	1400
December	1st to 10th	Day	18% 18% 5% 9% 4 4 4 3 5% 7% 23%	1365
	11th to 20th	Day	28% 14% 5% 7% 3 3 3 3 5% 6% 22%	1668
	21st to end	Day	17% 16% 3 9% 5% 3 4 3 5% 6% 29%	2442
January	1st to 10th	Night	10% 16% 7% 10% 5% 4 4 3 5% 6% 30%	4739
	11th to 20th	Night	15% 17% 6% 13% 7% 4 3 3 4 5% 22%	4493
	21st to end	Night	9% 12% 4 11% 5% 3 4 4 6% 6% 37%	4884
February	1st to 10th	Night	12% 14% 5% 10% 6% 4 3 4 4 6% 32%	2660
	11th to 20th	Night	12% 17% 6% 11% 6% 4 4 3 4 5% 30%	2447
	21st to end	Night	11% 15% 5% 10% 5% 4 3 3 4 5% 34%	1884
March	1st to 10th	Night	10% 13% 4 10% 7% 5% 5% 4 6% 6% 31%	3726
	11th to 20th	Night	14% 25% 9% 14% 6% 4 3 3 3 3 16%	3708
	21st to end	Night	21% 17% 4 8% 5% 4 4 3 5% 5% 23%	3478
April	1st to 10th	Night	20% 20% 6% 10% 6% 4 3 3 4 4 21%	1900
	11th to 20th	Night	21% 14% 4 7% 5% 3 4 4 4 5% 28%	1745
	21st to end	Night	24% 11% 4 9% 5% 4 3 2 4 5% 29%	1629
May	1st to 10th	Night	25% 18% 5% 9% 5% 4 5% 4 5% 5% 16%	2525
	11th to 20th	Night	22% 12% 4 7% 4 4 4 3 5% 6% 29%	2360
	21st to end	Night	38% 14% 3 6% 4 3 3 3 3 4 18%	2412
June	1st to 10th	Night	33% 12% 3 8% 6% 4 3 4 5% 5% 19%	1330
	11th to 20th	Night	33% 11% 3 7% 3 4 5% 4 5% 6% 18%	1170
	21st to end	Night	33% 12% 3 7% 4 4 4 4 5% 5% 19%	1140
July	1st to 10th	Night	34% 18% 3 6% 4 3 3 2 4 3 18%	1954
	11th to 20th	Night	36% 12% 3 5% 3 3 3 2 5% 4 24%	2241
	21st to end	Night	23% 8% 3 7% 4 4 5% 4 6% 7% 31%	2750
August	1st to 10th	Night	27% 11% 3 7% 5% 3 4 3 5% 7% 24%	2516
	11th to 20th	Night	32% 10% 3 6% 5% 4 3 3 4 5% 27%	2559
	21st to end	Night	23% 7% 2 5% 3 5% 4 4 6% 7% 34%	3221
September	1st to 10th	Night	28% 8% 3 6% 4 4 4 3 5% 6% 30%	1900
	11th to 20th	Night	29% 8% 3 6% 4 3 4 3 5% 5% 31%	2013
	21st to end	Night	27% 9% 3 7% 4 4 3 3 5% 6% 30%	2090
October	1st to 10th	Night	25% 10% 2 7% 4 5% 5% 3 4 5% 30%	2187
	11th to 20th	Night	25% 10% 3 7% 4 4 3 3 4 6% 30%	2460
	21st to end	Night	27% 13% 3 8% 4 3 3 3 4 6% 27%	2717
November	1st to 10th	Night	26% 11% 3 8% 4 3 4 3 4 5% 29%	2568
	11th to 20th	Night	27% 15% 3 7% 3 3 3 2 4 5% 27%	2980
	21st to end	Night	25% 19% 4 8% 4 3 3 3 4 4 23%	3000
December	1st to 10th	Night	18% 20% 6% 8% 5% 3 4 3 4 5% 23%	2932
	11th to 20th	Night	26% 16% 4 7% 3 3 3 3 5% 8% 22%	3531
	21st to end	Night	17% 16% 5% 9% 5% 3 4 3 5% 6% 27%	5225

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	55% 6% 11% 14% 9% 4	2217
	11th to 20th	Day	61% 10% 12% 13% 4	2474
	21st to end	Day	40% 10% 17% 19% 11% 2	2783
February	1st to 10th	Day	52% 6% 10% 21% 9% 2	1520
	11th to 20th	Day	57% 5% 10% 15% 11% 1	1625
	21st to end	Day	51% 4 9% 19% 16% 1	1570
March	1st to 10th	Day	49% 6% 12% 18% 13% 2	3118
	11th to 20th	Day	75% 5% 6% 9% 5%	3251
	21st to end	Day	61% 8% 9% 11% 8% 1	4153
April	1st to 10th	Day	64% 8% 8% 11% 8% 1	2280
	11th to 20th	Day	57% 6% 13% 15% 9% 1	2385
	21st to end	Day	58% 7% 10% 16% 7% 1	2547
May	1st to 10th	Day	67% 9% 9% 11% 3	4440
	11th to 20th	Day	56% 9% 14% 17% 4	4546
	21st to end	Day	67% 9% 10% 12% 3	5173
June	1st to 10th	Day	66% 8% 11% 10% 5%	2850
	11th to 20th	Day	62% 9% 12% 14% 3	3024
	21st to end	Day	61% 8% 13% 15% 3	3040
July	1st to 10th	Day	65% 6% 10% 15% 5%	4905
	11th to 20th	Day	61% 4 15% 16% 4	4643
	21st to end	Day	54% 7% 18% 20% 2	4662
August	1st to 10th	Day	60% 6% 16% 16% 2	4410
	11th to 20th	Day	62% 6% 14% 15% 3	4320
	21st to end	Day	53% 5% 16% 21% 5%	4441
September	1st to 10th	Day	52% 7% 14% 19% 8%	2280
	11th to 20th	Day	57% 6% 15% 15% 6% 1	2166
	21st to end	Day	56% 7% 14% 16% 7%	2090
October	1st to 10th	Day	48% 4 17% 26% 6%	3302
	11th to 20th	Day	58% 5% 17% 13% 6%	2842
	21st to end	Day	62% 3 10% 16% 7% 1	3092
November	1st to 10th	Day	55% 5% 15% 17% 8% 1	1725
	11th to 20th	Day	59% 3 14% 17% 7%	1418
	21st to end	Day	62% 5% 11% 14% 7%	1400
December	1st to 10th	Day	61% 6% 11% 16% 6%	1365
	11th to 20th	Day	62% 6% 13% 13% 6% 1	1667
	21st to end	Day	53% 6% 13% 18% 10%	2442
January	1st to 10th	Night	55% 5% 11% 16% 8% 5%	4739
	11th to 20th	Night	59% 12% 11% 13% 5%	4493
	21st to end	Night	44% 7% 10% 18% 18% 3	4884
February	1st to 10th	Night	54% 5% 11% 20% 9% 2	2660
	11th to 20th	Night	58% 4 13% 15% 9% 1	2451
	21st to end	Night	52% 4 11% 20% 11% 1	1884
March	1st to 10th	Night	52% 7% 10% 18% 12% 2	3735
	11th to 20th	Night	74% 4 7% 8% 7%	3709
	21st to end	Night	62% 7% 11% 12% 6% 2	3478
April	1st to 10th	Night	67% 6% 8% 11% 7% 1	1900
	11th to 20th	Night	57% 6% 12% 16% 8% 1	1745
	21st to end	Night	59% 6% 12% 14% 8% 2	1629
May	1st to 10th	Night	68% 9% 12% 8% 3	2530
	11th to 20th	Night	55% 9% 13% 18% 5%	2361
	21st to end	Night	69% 7% 8% 14% 3	2413
June	1st to 10th	Night	67% 8% 11% 10% 4 1	1330
	11th to 20th	Night	65% 9% 14% 9% 3	1170
	21st to end	Night	65% 7% 12% 12% 4	1140
July	1st to 10th	Night	71% 4 7% 13% 4	1923
	11th to 20th	Night	64% 4 11% 18% 3	2199
	21st to end	Night	52% 6% 19% 20% 2	2663
August	1st to 10th	Night	61% 5% 18% 15% 1	2505
	11th to 20th	Night	62% 5% 17% 13% 3	2583
	21st to end	Night	50% 6% 17% 22% 5%	3220
September	1st to 10th	Night	54% 7% 16% 17% 6%	1900
	11th to 20th	Night	54% 6% 16% 17% 6%	2013
	21st to end	Night	55% 6% 15% 16% 7% 1	2090
October	1st to 10th	Night	55% 4 12% 22% 7%	3655
	11th to 20th	Night	56% 5% 13% 17% 9%	4087
	21st to end	Night	62% 4 10% 15% 9%	4467
November	1st to 10th	Night	58% 5% 11% 17% 8% 1	2568
	11th to 20th	Night	60% 5% 13% 16% 5%	2980
	21st to end	Night	65% 5% 11% 13% 5%	3000
December	1st to 10th	Night	65% 6% 12% 12% 5% 1	2932
	11th to 20th	Night	61% 6% 13% 16% 4 1	3533
	21st to end	Night	56% 6% 12% 19% 6%	5225

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	20% 13% 32% 22% 11% 2	370
	11th to 20th	Day	24% 11% 34% 20% 8% 2	370
	21st to end	Day	19% 13% 31% 28% 8% 1	407
February	1st to 10th	Day	21% 10% 29% 28% 9% 3	370
	11th to 20th	Day	17% 15% 34% 27% 7% 1	366
	21st to end	Day	18% 15% 32% 24% 9% 3	307
March	1st to 10th	Day	15% 14% 35% 25% 8% 3	370
	11th to 20th	Day	22% 13% 23% 22% 16% 4	370
	21st to end	Day	23% 14% 28% 26% 8% 2	500
April	1st to 10th	Day	24% 13% 26% 25% 10% 2	460
	11th to 20th	Day	23% 10% 24% 27% 13% 4	583
	21st to end	Day	25% 9% 26% 25% 13% 3	650
May	1st to 10th	Day	28% 10% 23% 25% 11% 3	653
	11th to 20th	Day	27% 8% 23% 22% 15% 5%	674
	21st to end	Day	34% 8% 21% 27% 9% 1	735
June	1st to 10th	Day	33% 9% 20% 22% 12% 4	680
	11th to 20th	Day	36% 8% 17% 26% 10% 2	680
	21st to end	Day	36% 7% 16% 26% 10% 5%	680
July	1st to 10th	Day	38% 7% 19% 20% 14% 3	670
	11th to 20th	Day	33% 6% 19% 26% 15% 1	668
	21st to end	Day	33% 6% 17% 29% 14% 2	740
August	1st to 10th	Day	32% 6% 17% 28% 15% 3	675
	11th to 20th	Day	33% 8% 18% 26% 13% 2	667
	21st to end	Day	28% 7% 21% 27% 13% 3	696
September	1st to 10th	Day	32% 11% 25% 19% 11% 2	490
	11th to 20th	Day	27% 10% 27% 28% 6% 2	430
	21st to end	Day	31% 11% 25% 24% 7% 3	390
October	1st to 10th	Day	29% 9% 34% 21% 6% 1	390
	11th to 20th	Day	31% 10% 20% 29% 10%	390
	21st to end	Day	28% 15% 23% 21% 11% 1	429
November	1st to 10th	Day	29% 16% 34% 17% 3 1	395
	11th to 20th	Day	30% 14% 26% 19% 10%	400
	21st to end	Day	32% 17% 26% 19% 6%	400
December	1st to 10th	Day	28% 11% 28% 25% 8% 1	385
	11th to 20th	Day	25% 17% 33% 20% 5% 1	370
	21st to end	Day	22% 15% 28% 24% 8% 3	407
January	1st to 10th	Night	21% 16% 34% 20% 7% 1	850
	11th to 20th	Night	22% 15% 35% 23% 5%	850
	21st to end	Night	22% 13% 33% 26% 5%	935
February	1st to 10th	Night	20% 11% 34% 26% 8% 1	850
	11th to 20th	Night	19% 13% 37% 25% 6% 1	785
	21st to end	Night	18% 7% 35% 28% 10% 2	628
March	1st to 10th	Night	16% 14% 36% 25% 9% 1	760
	11th to 20th	Night	23% 11% 26% 29% 11% 1	708
	21st to end	Night	25% 12% 32% 24% 7%	627
April	1st to 10th	Night	28% 11% 29% 23% 9% 1	570
	11th to 20th	Night	26% 10% 27% 24% 12% 1	564
	21st to end	Night	29% 7% 23% 30% 9% 1	570
May	1st to 10th	Night	30% 8% 22% 26% 12% 3	570
	11th to 20th	Night	29% 8% 25% 25% 12% 2	562
	21st to end	Night	37% 7% 21% 26% 9% 1	616
June	1st to 10th	Night	36% 6% 21% 26% 10% 1	570
	11th to 20th	Night	36% 5% 18% 29% 10% 1	410
	21st to end	Night	37% 6% 15% 24% 16% 2	380
July	1st to 10th	Night	42% 7% 16% 23% 11% 1	397
	11th to 20th	Night	40% 6% 16% 28% 11%	552
	21st to end	Night	33% 4 17% 32% 12% 1	623
August	1st to 10th	Night	32% 6% 17% 32% 13% 1	568
	11th to 20th	Night	35% 8% 15% 27% 14% 1	562
	21st to end	Night	30% 4 21% 27% 16% 1	627
September	1st to 10th	Night	29% 9% 25% 27% 9% 1	570
	11th to 20th	Night	31% 8% 31% 22% 7%	570
	21st to end	Night	33% 8% 29% 22% 7% 1	570
October	1st to 10th	Night	29% 9% 30% 25% 6% 1	667
	11th to 20th	Night	31% 8% 25% 27% 9% 1	855
	21st to end	Night	33% 12% 25% 22% 8% 1	946
November	1st to 10th	Night	31% 14% 32% 18% 4 1	880
	11th to 20th	Night	34% 14% 27% 19% 7% 1	900
	21st to end	Night	33% 16% 31% 16% 3	900
December	1st to 10th	Night	28% 12% 32% 22% 6% 1	878
	11th to 20th	Night	27% 17% 31% 21% 4	850
	21st to end	Night	22% 14% 32% 23% 8% 1	935

Page generated at 2024-12-03 06:45:15. Version ac07

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