Sachs Harbour
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sachs Harbour clear sky chart from 2005-11-06 to 2024-12-09.

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
Transparency	Day	57% 6% 17% 16% 4	112874
	Night	53% 7% 14% 19% 6%	103612
Seeing	Day	14% 3 13% 27% 29% 14%	19981
	Night	8% 2 13% 30% 32% 15%	22984

By Month

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	21st to end	Day	36% 5% 14% 36% 7% 2	102
	February	1st to 10th	Day	48% 6% 21% 19% 5%	629
11th to 20th		Day	45% 10% 14% 26% 5%	1022
21st to end		Day	45% 8% 14% 27% 6% 1	1099
March	1st to 10th	Day	47% 6% 14% 19% 14%	2774
	11th to 20th	Day	39% 6% 9% 27% 19%	3314
	21st to end	Day	38% 5% 11% 24% 21% 1	4181
April	1st to 10th	Day	43% 6% 19% 25% 7%	2605
	11th to 20th	Day	50% 7% 16% 21% 6%	2897
	21st to end	Day	50% 6% 15% 23% 7%	3321
May	1st to 10th	Day	65% 5% 13% 14% 3	6433
	11th to 20th	Day	56% 6% 20% 15% 3	7533
	21st to end	Day	49% 5% 20% 21% 5%	8272
June	1st to 10th	Day	47% 5% 18% 25% 4	4560
	11th to 20th	Day	49% 10% 21% 18% 2	4560
	21st to end	Day	44% 8% 25% 22% 1	4560
July	1st to 10th	Day	66% 4 13% 14% 2	7481
	11th to 20th	Day	54% 6% 18% 16% 6%	7465
	21st to end	Day	56% 6% 22% 16% 1	7987
August	1st to 10th	Day	55% 7% 20% 15% 3	6499
	11th to 20th	Day	73% 6% 16% 5%	5557
	21st to end	Day	77% 5% 15% 3	5452
September	1st to 10th	Day	75% 4 15% 6%	2639
	11th to 20th	Day	67% 7% 20% 5%	2349
	21st to end	Day	75% 7% 14% 4	2009
October	1st to 10th	Day	64% 6% 15% 14% 1	2866
	11th to 20th	Day	76% 5% 11% 7%	2292
	21st to end	Day	69% 4 17% 10%	1804
November	1st to 10th	Day	60% 6% 18% 16%	578
	11th to 20th	Day	79% 12% 9%	34
January	1st to 10th	Night	35% 5% 16% 41% 4	7585
	11th to 20th	Night	41% 5% 13% 20% 20% 1	7600
	21st to end	Night	43% 9% 10% 27% 12%	8027
February	1st to 10th	Night	49% 9% 15% 20% 6%	3549
	11th to 20th	Night	45% 7% 16% 26% 6%	3072
	21st to end	Night	47% 7% 16% 25% 6%	2355
March	1st to 10th	Night	46% 6% 15% 23% 11%	4087
	11th to 20th	Night	39% 5% 9% 27% 20% 1	3662
	21st to end	Night	40% 4 14% 24% 17% 1	3467
April	1st to 10th	Night	41% 8% 19% 25% 6% 1	1576
	11th to 20th	Night	45% 7% 17% 25% 6%	1230
	21st to end	Night	48% 7% 14% 24% 8%	857
May	1st to 10th	Night	63% 5% 10% 18% 3	566
	August	1st to 10th	Night	49% 6% 16% 23% 7%	501
11th to 20th		Night	74% 5% 15% 5% 1	1335
21st to end		Night	77% 6% 13% 4	2204
September	1st to 10th	Night	73% 3 16% 7%	1540
	11th to 20th	Night	68% 7% 17% 7%	1829
	21st to end	Night	77% 7% 13% 3	2171
October	1st to 10th	Night	59% 9% 16% 13% 2	4104
	11th to 20th	Night	77% 5% 12% 7%	4595
	21st to end	Night	74% 4 15% 7%	5744
November	1st to 10th	Night	58% 7% 21% 13% 1	3716
	11th to 20th	Night	67% 10% 12% 10% 1	4646
	21st to end	Night	64% 8% 15% 11% 3	4800
December	1st to 10th	Night	50% 10% 19% 17% 3	4759
	11th to 20th	Night	43% 8% 16% 29% 6%	5675
	21st to end	Night	56% 7% 13% 20% 4	8360

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
February	1st to 10th	Day	1 3 8% 26% 38% 25%	101
	11th to 20th	Day	4 2 8% 29% 36% 20%	180
	21st to end	Day	2 1 9% 29% 33% 26%	150
March	1st to 10th	Day	2 1 13% 24% 36% 23%	357
	11th to 20th	Day	4 3 14% 27% 35% 17%	436
	21st to end	Day	5% 1 12% 33% 31% 18%	506
April	1st to 10th	Day	4 1 11% 21% 35% 29%	498
	11th to 20th	Day	3 3 12% 30% 35% 17%	717
	21st to end	Day	4 2 11% 30% 33% 20%	840
May	1st to 10th	Day	9% 3 12% 25% 34% 17%	934
	11th to 20th	Day	6% 4 12% 29% 33% 15%	1236
	21st to end	Day	6% 2 10% 25% 38% 19%	1351
June	1st to 10th	Day	9% 2 13% 28% 31% 18%	1250
	11th to 20th	Day	11% 3 17% 30% 30% 9%	1250
	21st to end	Day	13% 4 14% 30% 29% 10%	1250
July	1st to 10th	Day	15% 3 12% 26% 31% 13%	1226
	11th to 20th	Day	17% 4 13% 27% 28% 11%	1220
	21st to end	Day	21% 4 13% 27% 27% 9%	1363
August	1st to 10th	Day	26% 5% 13% 26% 21% 9%	1016
	11th to 20th	Day	28% 4 14% 26% 21% 7%	853
	21st to end	Day	26% 3 12% 24% 25% 9%	843
September	1st to 10th	Day	29% 4 12% 21% 20% 13%	539
	11th to 20th	Day	23% 6% 14% 27% 22% 8%	490
	21st to end	Day	25% 8% 16% 26% 17% 8%	490
October	1st to 10th	Day	15% 4 15% 28% 27% 10%	369
	11th to 20th	Day	14% 4 17% 24% 25% 17%	200
	21st to end	Day	11% 6% 19% 23% 28% 12%	220
November	1st to 10th	Day	10% 2 11% 34% 24% 18%	96
	January	1st to 10th	Night	5% 1 17% 32% 29% 16%	1220
11th to 20th		Night	4 2 15% 32% 32% 14%	1220
21st to end		Night	2 1 9% 33% 35% 20%	1308
February	1st to 10th	Night	2 2 11% 31% 33% 21%	1049
	11th to 20th	Night	5% 2 12% 29% 35% 17%	972
	21st to end	Night	3 2 11% 30% 33% 21%	703
March	1st to 10th	Night	3 1 10% 31% 38% 18%	771
	11th to 20th	Night	2 2 10% 27% 37% 22%	760
	21st to end	Night	3 1 10% 32% 34% 20%	746
April	1st to 10th	Night	2 2 9% 30% 36% 21%	474
	11th to 20th	Night	6% 1 10% 33% 35% 15%	375
	21st to end	Night	6% 2 12% 31% 36% 14%	368
May	1st to 10th	Night	6% 7% 30% 35% 23%	71
	August	1st to 10th	Night	26% 2 9% 23% 29% 11%	65
11th to 20th		Night	30% 5% 11% 23% 26% 5%	316
21st to end		Night	25% 4 9% 25% 26% 10%	418
September	1st to 10th	Night	27% 3 9% 27% 28% 7%	448
	11th to 20th	Night	21% 5% 13% 29% 23% 8%	684
	21st to end	Night	25% 4 16% 26% 22% 7%	760
October	1st to 10th	Night	16% 3 13% 31% 29% 8%	760
	11th to 20th	Night	15% 5% 16% 28% 25% 10%	833
	21st to end	Night	17% 4 13% 27% 29% 10%	1155
November	1st to 10th	Night	7% 2 15% 29% 34% 13%	1075
	11th to 20th	Night	6% 2 16% 30% 32% 14%	1284
	21st to end	Night	7% 2 13% 27% 34% 18%	1300
December	1st to 10th	Night	5% 2 17% 28% 29% 18%	1287
	11th to 20th	Night	4 4 12% 31% 30% 20%	1220
	21st to end	Night	3 3 13% 33% 35% 13%	1342

Page generated at 2024-12-06 01:54:49. Version ac07

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