Abraham Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Abraham Lake clear sky chart from 2005-11-06 to 2024-11-01.

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	6% 9% 4 10% 7% 6% 6% 5% 7% 8% 31%	102608
	Night	3 8% 4 10% 7% 7% 7% 6% 8% 9% 31%	96370
Transparency	Day	44% 11% 16% 19% 9% 1	102355
	Night	41% 13% 18% 20% 8% 1	96269
Seeing	Day	17% 20% 33% 20% 7% 2	15808
	Night	11% 17% 38% 24% 9% 1	24140

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	4 3 13% 13% 13% 10% 7% 10% 9% 18%	2219
	11th to 20th	Day	1 4 2 9% 10% 8% 7% 8% 8% 9% 34%	2339
	21st to end	Day	1 6% 4 9% 8% 8% 8% 8% 11% 11% 26%	2794
February	1st to 10th	Day	1 6% 4 11% 9% 9% 9% 7% 10% 10% 24%	1520
	11th to 20th	Day	1 9% 4 12% 8% 8% 7% 7% 8% 9% 28%	1574
	21st to end	Day	1 5% 5% 12% 11% 8% 10% 7% 9% 10% 23%	1570
March	1st to 10th	Day	5% 3 14% 12% 9% 7% 5% 7% 7% 30%	3138
	11th to 20th	Day	3 8% 3 8% 6% 7% 7% 6% 8% 8% 35%	3303
	21st to end	Day	1 14% 8% 22% 8% 5% 6% 4 7% 7% 18%	4071
April	1st to 10th	Day	3 13% 6% 14% 10% 9% 8% 6% 8% 8% 15%	2280
	11th to 20th	Day	3 14% 6% 15% 10% 6% 7% 5% 7% 8% 19%	2421
	21st to end	Day	6% 16% 6% 14% 7% 6% 6% 5% 6% 8% 21%	2524
May	1st to 10th	Day	7% 22% 5% 10% 6% 5% 5% 3 6% 8% 23%	4420
	11th to 20th	Day	6% 12% 4 10% 7% 6% 7% 5% 8% 9% 26%	4652
	21st to end	Day	11% 17% 5% 13% 7% 6% 6% 5% 5% 7% 17%	5161
June	1st to 10th	Day	15% 12% 3 10% 6% 6% 6% 5% 7% 8% 21%	2855
	11th to 20th	Day	19% 13% 3 9% 6% 5% 6% 4 7% 7% 20%	3040
	21st to end	Day	11% 9% 4 8% 8% 6% 7% 5% 7% 7% 28%	3040
July	1st to 10th	Day	7% 6% 3 6% 5% 4 5% 4 6% 7% 48%	5042
	11th to 20th	Day	6% 3 1 4 4 3 4 4 7% 8% 55%	4740
	21st to end	Day	6% 5% 2 6% 5% 4 5% 5% 7% 9% 45%	4895
August	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 4 7% 7% 37%	4401
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 6% 9% 11% 37%	4271
	21st to end	Day	10% 7% 3 7% 6% 5% 6% 5% 7% 8% 36%	4500
September	1st to 10th	Day	11% 10% 4 7% 4 4 5% 4 5% 8% 39%	2280
	11th to 20th	Day	8% 11% 3 8% 6% 4 5% 5% 6% 8% 37%	2165
	21st to end	Day	8% 9% 4 9% 6% 7% 5% 5% 6% 7% 33%	2090
October	1st to 10th	Day	6% 12% 5% 8% 6% 5% 5% 5% 7% 8% 33%	2004
	11th to 20th	Day	5% 8% 5% 9% 6% 6% 7% 5% 8% 10% 33%	1710
	21st to end	Day	2 9% 4 11% 7% 8% 7% 6% 9% 9% 30%	1881
November	1st to 10th	Day	1 8% 5% 12% 8% 7% 8% 6% 8% 10% 27%	1594
	11th to 20th	Day	1 6% 3 9% 7% 7% 8% 7% 10% 11% 31%	1330
	21st to end	Day	1 7% 4 11% 8% 9% 7% 6% 8% 9% 30%	1330
December	1st to 10th	Day	2 5% 3 12% 11% 6% 7% 7% 8% 10% 29%	1330
	11th to 20th	Day	5% 3 12% 8% 10% 9% 7% 10% 10% 26%	1682
	21st to end	Day	5% 3 9% 7% 7% 7% 6% 9% 11% 35%	2442
January	1st to 10th	Night	5% 5% 17% 10% 10% 9% 7% 10% 9% 17%	4726
	11th to 20th	Night	4 2 9% 9% 9% 8% 6% 13% 10% 30%	4590
	21st to end	Night	1 5% 4 11% 9% 10% 9% 8% 9% 9% 26%	4862
February	1st to 10th	Night	1 8% 3 11% 10% 10% 9% 7% 9% 10% 22%	2660
	11th to 20th	Night	1 6% 4 12% 6% 8% 8% 6% 10% 11% 27%	2488
	21st to end	Night	5% 4 10% 12% 8% 8% 7% 9% 10% 27%	1884
March	1st to 10th	Night	4 5% 13% 10% 10% 11% 7% 9% 9% 22%	3736
	11th to 20th	Night	2 7% 3 8% 5% 5% 8% 7% 8% 10% 36%	3663
	21st to end	Night	1 13% 8% 20% 9% 5% 5% 4 7% 6% 21%	3568
April	1st to 10th	Night	2 11% 5% 12% 9% 7% 6% 6% 8% 9% 25%	1900
	11th to 20th	Night	3 12% 5% 13% 7% 4 5% 5% 8% 8% 29%	1710
	21st to end	Night	3 13% 4 12% 6% 6% 5% 5% 6% 7% 34%	1653
May	1st to 10th	Night	5% 22% 6% 12% 5% 4 4 3 5% 6% 26%	2540
	11th to 20th	Night	6% 13% 4 10% 5% 6% 5% 6% 7% 8% 30%	2241
	21st to end	Night	9% 12% 4 10% 7% 7% 6% 5% 9% 8% 24%	2414
June	1st to 10th	Night	14% 11% 3 7% 4 6% 5% 4 6% 8% 33%	1321
	11th to 20th	Night	15% 11% 4 9% 6% 6% 6% 4 6% 7% 25%	1140
	21st to end	Night	7% 6% 1 6% 5% 4 4 5% 7% 11% 43%	1140
July	1st to 10th	Night	6% 5% 2 5% 5% 4 4 4 6% 8% 51%	1900
	11th to 20th	Night	5% 4 1 3 3 3 4 3 5% 7% 62%	2220
	21st to end	Night	4 4 2 4 4 4 5% 5% 8% 10% 51%	2654
August	1st to 10th	Night	11% 10% 3 6% 3 3 4 4 6% 9% 40%	2529
	11th to 20th	Night	7% 6% 2 5% 4 3 5% 4 8% 11% 44%	2557
	21st to end	Night	8% 7% 2 6% 4 5% 4 4 6% 9% 43%	3166
September	1st to 10th	Night	8% 8% 2 5% 4 4 6% 4 6% 8% 45%	1900
	11th to 20th	Night	8% 10% 4 8% 5% 4 5% 3 6% 7% 40%	2014
	21st to end	Night	5% 8% 3 8% 4 5% 5% 6% 7% 9% 40%	2090
October	1st to 10th	Night	5% 10% 5% 10% 5% 5% 5% 4 7% 9% 36%	2173
	11th to 20th	Night	3 9% 4 11% 6% 6% 7% 5% 7% 9% 33%	2470
	21st to end	Night	2 9% 4 14% 9% 8% 7% 5% 7% 8% 28%	2717
November	1st to 10th	Night	1 9% 5% 12% 10% 8% 8% 6% 9% 10% 24%	2470
	11th to 20th	Night	1 6% 3 10% 8% 8% 10% 6% 8% 11% 28%	2850
	21st to end	Night	1 7% 4 11% 9% 8% 8% 6% 9% 9% 28%	2850
December	1st to 10th	Night	1 7% 3 11% 8% 7% 8% 7% 9% 12% 28%	2850
	11th to 20th	Night	5% 4 15% 9% 11% 9% 7% 9% 10% 21%	3510
	21st to end	Night	3 3 10% 8% 9% 9% 7% 9% 12% 29%	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	46% 14% 15% 17% 6% 1	2219
	11th to 20th	Day	37% 12% 14% 15% 17% 4	2361
	21st to end	Day	33% 19% 24% 18% 6% 1	2794
February	1st to 10th	Day	45% 12% 16% 14% 10% 3	1520
	11th to 20th	Day	46% 12% 13% 19% 9% 1	1582
	21st to end	Day	49% 13% 12% 16% 9% 1	1570
March	1st to 10th	Day	38% 17% 16% 16% 12% 1	3138
	11th to 20th	Day	34% 19% 20% 21% 7%	3304
	21st to end	Day	59% 10% 12% 12% 7%	4071
April	1st to 10th	Day	56% 16% 14% 11% 3	2280
	11th to 20th	Day	57% 11% 13% 15% 4	2421
	21st to end	Day	59% 10% 12% 14% 4	2524
May	1st to 10th	Day	59% 8% 14% 16% 3	4420
	11th to 20th	Day	50% 11% 15% 19% 6%	4656
	21st to end	Day	57% 16% 13% 10% 4	5162
June	1st to 10th	Day	56% 10% 13% 14% 5% 1	2855
	11th to 20th	Day	60% 9% 12% 13% 6%	3040
	21st to end	Day	50% 9% 17% 16% 8% 1	3040
July	1st to 10th	Day	34% 7% 11% 22% 21% 5%	4963
	11th to 20th	Day	27% 6% 13% 31% 21% 3	4659
	21st to end	Day	32% 8% 16% 26% 17% 1	4740
August	1st to 10th	Day	40% 9% 13% 30% 7%	4384
	11th to 20th	Day	36% 10% 21% 27% 6% 1	4313
	21st to end	Day	39% 9% 22% 21% 7% 1	4499
September	1st to 10th	Day	41% 8% 18% 23% 9% 1	2280
	11th to 20th	Day	42% 9% 14% 25% 9% 1	2165
	21st to end	Day	43% 11% 16% 19% 9% 1	2090
October	1st to 10th	Day	45% 10% 15% 23% 7%	2004
	11th to 20th	Day	41% 11% 18% 23% 6%	1710
	21st to end	Day	41% 15% 18% 18% 7%	1881
November	1st to 10th	Day	44% 15% 18% 15% 7% 1	1594
	11th to 20th	Day	36% 13% 26% 17% 6%	1330
	21st to end	Day	41% 13% 19% 18% 5% 3	1330
December	1st to 10th	Day	44% 12% 18% 16% 10% 1	1330
	11th to 20th	Day	39% 15% 20% 17% 8% 1	1684
	21st to end	Day	32% 14% 18% 21% 14% 1	2442
January	1st to 10th	Night	46% 19% 14% 14% 6% 1	4726
	11th to 20th	Night	37% 15% 13% 13% 17% 5%	4630
	21st to end	Night	39% 17% 21% 16% 6% 1	4862
February	1st to 10th	Night	49% 13% 13% 14% 9% 2	2660
	11th to 20th	Night	43% 12% 16% 17% 10% 1	2490
	21st to end	Night	44% 11% 14% 21% 9% 1	1884
March	1st to 10th	Night	41% 17% 16% 15% 11%	3736
	11th to 20th	Night	31% 17% 21% 23% 8%	3663
	21st to end	Night	55% 9% 11% 18% 6%	3568
April	1st to 10th	Night	46% 16% 16% 16% 6%	1900
	11th to 20th	Night	47% 9% 19% 17% 7%	1710
	21st to end	Night	46% 11% 18% 20% 5% 1	1653
May	1st to 10th	Night	57% 6% 16% 19% 3	2540
	11th to 20th	Night	43% 15% 15% 21% 6%	2241
	21st to end	Night	45% 18% 16% 16% 5%	2414
June	1st to 10th	Night	47% 8% 16% 21% 7% 1	1321
	11th to 20th	Night	53% 10% 16% 16% 5%	1140
	21st to end	Night	32% 8% 26% 26% 7% 1	1140
July	1st to 10th	Night	30% 7% 14% 29% 20% 1	1870
	11th to 20th	Night	21% 6% 17% 36% 18% 1	2178
	21st to end	Night	26% 7% 21% 32% 14% 1	2570
August	1st to 10th	Night	37% 7% 18% 33% 4	2521
	11th to 20th	Night	31% 9% 28% 26% 6%	2581
	21st to end	Night	34% 10% 26% 24% 6%	3166
September	1st to 10th	Night	34% 9% 20% 26% 9% 1	1900
	11th to 20th	Night	40% 9% 18% 23% 10% 1	2014
	21st to end	Night	35% 12% 21% 23% 9%	2090
October	1st to 10th	Night	41% 11% 18% 23% 6% 1	2173
	11th to 20th	Night	42% 12% 19% 21% 7%	2470
	21st to end	Night	46% 14% 15% 18% 6%	2717
November	1st to 10th	Night	48% 16% 13% 14% 8% 1	2470
	11th to 20th	Night	39% 17% 20% 15% 8% 1	2850
	21st to end	Night	43% 14% 17% 16% 7% 3	2850
December	1st to 10th	Night	43% 12% 13% 19% 11% 2	2850
	11th to 20th	Night	45% 16% 20% 13% 5% 1	3507
	21st to end	Night	37% 13% 21% 19% 9% 1	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	12% 18% 35% 23% 10% 2	180
	11th to 20th	Day	14% 14% 44% 21% 5% 2	180
	21st to end	Day	11% 29% 41% 12% 6% 2	198
February	1st to 10th	Day	19% 23% 39% 11% 5% 2	180
	11th to 20th	Day	13% 18% 38% 24% 7%	245
	21st to end	Day	14% 23% 38% 17% 6% 1	382
March	1st to 10th	Day	15% 26% 32% 18% 7% 2	460
	11th to 20th	Day	14% 26% 33% 21% 4 2	460
	21st to end	Day	16% 25% 33% 20% 5% 2	506
April	1st to 10th	Day	21% 25% 31% 17% 5% 1	460
	11th to 20th	Day	13% 26% 34% 18% 8% 2	452
	21st to end	Day	19% 24% 28% 19% 8% 1	460
May	1st to 10th	Day	18% 18% 36% 20% 6% 1	463
	11th to 20th	Day	16% 11% 30% 28% 13% 2	646
	21st to end	Day	24% 14% 28% 22% 10% 2	734
June	1st to 10th	Day	21% 22% 31% 20% 5% 1	685
	11th to 20th	Day	26% 20% 30% 17% 7% 1	870
	21st to end	Day	17% 16% 30% 24% 10% 3	870
July	1st to 10th	Day	14% 16% 33% 26% 9% 2	851
	11th to 20th	Day	16% 12% 36% 23% 12% 1	668
	21st to end	Day	11% 17% 35% 23% 11% 3	597
August	1st to 10th	Day	14% 14% 33% 25% 11% 2	487
	11th to 20th	Day	11% 21% 38% 21% 8% 2	477
	21st to end	Day	17% 22% 34% 20% 6% 1	539
September	1st to 10th	Day	19% 25% 29% 21% 5% 1	490
	11th to 20th	Day	20% 19% 36% 19% 5% 1	490
	21st to end	Day	21% 28% 30% 14% 5% 1	490
October	1st to 10th	Day	21% 24% 29% 18% 6% 2	485
	11th to 20th	Day	19% 23% 33% 19% 5%	300
	21st to end	Day	18% 23% 38% 15% 4 1	330
November	1st to 10th	Day	13% 27% 39% 14% 5% 2	255
	11th to 20th	Day	18% 27% 41% 9% 5% 1	180
	21st to end	Day	16% 27% 29% 17% 7% 5%	180
December	1st to 10th	Day	11% 23% 37% 19% 6% 4	180
	11th to 20th	Day	11% 25% 40% 19% 4 1	180
	21st to end	Day	10% 13% 47% 23% 7% 1	198
January	1st to 10th	Night	9% 21% 49% 16% 5%	950
	11th to 20th	Night	8% 25% 45% 17% 4 1	879
	21st to end	Night	7% 27% 43% 16% 5%	836
February	1st to 10th	Night	10% 22% 38% 22% 8% 1	760
	11th to 20th	Night	7% 19% 43% 24% 7%	744
	21st to end	Night	7% 13% 42% 24% 13% 1	628
March	1st to 10th	Night	5% 20% 41% 23% 9% 1	760
	11th to 20th	Night	6% 19% 45% 21% 7% 1	760
	21st to end	Night	8% 16% 37% 28% 10% 1	836
April	1st to 10th	Night	9% 16% 35% 29% 11% 1	760
	11th to 20th	Night	10% 13% 41% 25% 11%	582
	21st to end	Night	12% 13% 37% 28% 8% 1	513
May	1st to 10th	Night	14% 9% 29% 35% 13% 1	380
	11th to 20th	Night	13% 4 28% 38% 17% 1	374
	21st to end	Night	20% 9% 25% 32% 13%	411
June	1st to 10th	Night	19% 8% 34% 28% 10% 1	380
	11th to 20th	Night	21% 10% 31% 27% 10%	380
	21st to end	Night	12% 9% 29% 31% 18% 1	380
July	1st to 10th	Night	12% 5% 32% 34% 15%	370
	11th to 20th	Night	13% 8% 29% 38% 13%	368
	21st to end	Night	6% 6% 25% 44% 18% 1	416
August	1st to 10th	Night	13% 4 19% 37% 25% 2	378
	11th to 20th	Night	12% 6% 25% 36% 20% 1	410
	21st to end	Night	13% 11% 31% 34% 11% 1	634
September	1st to 10th	Night	14% 12% 30% 31% 11% 2	760
	11th to 20th	Night	14% 9% 31% 30% 13% 2	760
	21st to end	Night	17% 19% 31% 21% 10% 1	760
October	1st to 10th	Night	13% 15% 36% 27% 10%	760
	11th to 20th	Night	16% 16% 41% 21% 6%	760
	21st to end	Night	12% 20% 42% 21% 4	836
November	1st to 10th	Night	10% 24% 45% 15% 5%	770
	11th to 20th	Night	13% 24% 47% 13% 3	950
	21st to end	Night	10% 25% 41% 17% 6% 1	950
December	1st to 10th	Night	8% 25% 39% 20% 7%	950
	11th to 20th	Night	8% 23% 44% 18% 6% 1	950
	21st to end	Night	4 22% 47% 19% 6% 1	1045

Page generated at 2024-10-29 09:20:52. Version ac07

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