Linslaw Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Linslaw Point clear sky chart from 2005-11-06 to 2024-11-05.

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% 3 7% 4 4 4 3 5% 6% 37%	105396
	Night	20% 10% 3 7% 4 4 4 3 4 5% 36%	102341
Transparency	Day	46% 7% 11% 17% 13% 5%	105146
	Night	49% 7% 12% 17% 11% 4	102181
Seeing	Day	24% 13% 24% 25% 11% 2	14835
	Night	27% 7% 15% 29% 20% 2	23767

By Month

Percentage Cloud Cover SW (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% 19% 6% 10% 5% 4 4 3 3 3 9%	2539
	11th to 20th	Day	39% 14% 3 7% 4 4 4 3 3 4 15%	2645
	21st to end	Day	34% 13% 4 9% 5% 5% 4 3 4 5% 13%	3146
February	1st to 10th	Day	29% 15% 4 10% 5% 5% 4 4 5% 6% 13%	1710
	11th to 20th	Day	28% 15% 4 10% 5% 4 4 4 4 5% 18%	1665
	21st to end	Day	30% 18% 4 9% 5% 4 4 2 4 4 17%	1465
March	1st to 10th	Day	22% 20% 4 8% 6% 5% 4 3 5% 5% 18%	3403
	11th to 20th	Day	22% 11% 3 8% 4 4 3 2 4 5% 34%	3490
	21st to end	Day	28% 15% 4 11% 6% 6% 5% 3 4 4 13%	3825
April	1st to 10th	Day	29% 15% 4 11% 6% 5% 4 3 4 4 16%	2280
	11th to 20th	Day	25% 14% 4 9% 6% 4 4 3 4 6% 21%	2262
	21st to end	Day	23% 11% 4 8% 5% 4 4 3 6% 6% 24%	2470
May	1st to 10th	Day	19% 9% 4 8% 5% 5% 5% 3 4 6% 32%	4189
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 5% 8% 51%	4377
	21st to end	Day	15% 8% 3 7% 6% 5% 7% 5% 7% 8% 29%	4813
June	1st to 10th	Day	23% 9% 3 7% 4 3 4 4 5% 6% 31%	2660
	11th to 20th	Day	15% 9% 3 8% 6% 4 5% 4 6% 8% 33%	2660
	21st to end	Day	10% 6% 2 5% 4 3 3 2 5% 7% 53%	2660
July	1st to 10th	Day	3 3 1 3 2 2 2 2 3 4 76%	4420
	11th to 20th	Day	5% 3 1 3 2 2 2 2 3 5% 70%	4420
	21st to end	Day	4 3 1 3 2 2 2 2 3 5% 74%	4608
August	1st to 10th	Day	2 3 2 4 3 3 3 3 5% 7% 65%	4091
	11th to 20th	Day	5% 3 2 5% 3 3 4 4 5% 8% 57%	4026
	21st to end	Day	6% 5% 2 5% 4 3 4 3 5% 7% 57%	4322
September	1st to 10th	Day	5% 3 1 3 3 2 3 3 5% 6% 65%	2280
	11th to 20th	Day	10% 6% 3 7% 4 4 4 4 5% 7% 46%	2218
	21st to end	Day	14% 6% 2 6% 4 3 3 3 5% 6% 46%	2035
October	1st to 10th	Day	12% 8% 2 6% 4 3 3 2 4 5% 50%	3180
	11th to 20th	Day	17% 7% 3 9% 6% 6% 6% 5% 6% 8% 28%	3161
	21st to end	Day	22% 11% 4 9% 5% 6% 5% 4 6% 7% 22%	3448
November	1st to 10th	Day	31% 11% 5% 9% 4 5% 4 4 4 5% 18%	1646
	11th to 20th	Day	33% 9% 4 9% 5% 5% 4 4 5% 6% 18%	1520
	21st to end	Day	28% 11% 3 8% 6% 5% 5% 3 5% 5% 22%	1520
December	1st to 10th	Day	26% 12% 3 9% 6% 3 3 4 4 6% 24%	1520
	11th to 20th	Day	29% 12% 4 9% 5% 5% 5% 4 7% 6% 13%	1928
	21st to end	Day	33% 16% 4 10% 5% 5% 5% 3 4 5% 9%	2794
January	1st to 10th	Night	35% 18% 4 10% 7% 5% 4 2 3 3 9%	4406
	11th to 20th	Night	38% 15% 4 8% 4 3 4 2 3 4 16%	4314
	21st to end	Night	41% 15% 3 7% 3 3 3 2 3 5% 15%	4521
February	1st to 10th	Night	26% 14% 5% 9% 5% 4 5% 4 5% 5% 18%	2470
	11th to 20th	Night	26% 13% 4 8% 4 4 4 3 5% 4 25%	2402
	21st to end	Night	27% 15% 3 8% 5% 5% 4 3 5% 5% 20%	1989
March	1st to 10th	Night	21% 21% 4 7% 4 4 3 3 5% 5% 21%	3466
	11th to 20th	Night	19% 12% 2 7% 5% 4 4 3 3 4 37%	3490
	21st to end	Night	27% 17% 4 10% 5% 4 4 3 4 5% 17%	3828
April	1st to 10th	Night	25% 17% 4 8% 5% 5% 3 3 4 5% 22%	1900
	11th to 20th	Night	20% 14% 3 7% 5% 3 4 3 5% 6% 30%	1861
	21st to end	Night	20% 11% 3 8% 5% 4 5% 3 5% 7% 29%	1710
May	1st to 10th	Night	21% 10% 3 7% 4 3 3 3 3 4 40%	2778
	11th to 20th	Night	9% 7% 2 5% 4 3 3 3 4 6% 54%	2516
	21st to end	Night	14% 8% 3 6% 5% 4 4 4 5% 7% 41%	2762
June	1st to 10th	Night	17% 8% 3 5% 4 4 4 3 5% 7% 39%	1520
	11th to 20th	Night	11% 7% 3 5% 2 3 3 4 6% 9% 48%	1520
	21st to end	Night	9% 4 1 4 3 4 4 3 4 6% 59%	1520
July	1st to 10th	Night	2 2 1 3 1 1 2 1 2 4 81%	2540
	11th to 20th	Night	4 2 1 3 3 3 3 3 3 4 71%	2540
	21st to end	Night	3 4 2 3 2 2 2 2 3 5% 73%	2946
August	1st to 10th	Night	1 3 1 3 2 3 4 3 5% 8% 66%	2848
	11th to 20th	Night	3 4 2 6% 4 5% 4 4 6% 7% 55%	2812
	21st to end	Night	4 4 2 5% 3 3 2 3 4 5% 66%	3338
September	1st to 10th	Night	6% 4 1 4 2 3 3 3 5% 6% 65%	1900
	11th to 20th	Night	8% 6% 2 6% 4 4 3 3 5% 7% 52%	1958
	21st to end	Night	11% 6% 2 5% 3 3 3 3 5% 6% 52%	2144
October	1st to 10th	Night	9% 6% 2 6% 3 3 3 2 4 6% 55%	3800
	11th to 20th	Night	15% 9% 4 8% 5% 5% 5% 4 6% 8% 33%	3777
	21st to end	Night	25% 12% 4 9% 4 4 4 3 5% 5% 25%	4121
November	1st to 10th	Night	29% 10% 4 7% 4 4 4 4 5% 5% 25%	2526
	11th to 20th	Night	31% 10% 3 8% 6% 5% 3 3 5% 5% 20%	2660
	21st to end	Night	23% 10% 3 7% 5% 4 5% 4 5% 6% 28%	2660
December	1st to 10th	Night	25% 11% 3 7% 5% 4 4 3 5% 6% 26%	2660
	11th to 20th	Night	30% 12% 5% 8% 5% 5% 4 3 5% 6% 17%	3276
	21st to end	Night	28% 15% 5% 10% 6% 5% 4 4 5% 5% 14%	4862

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	78% 7% 8% 4 2 1	2539
	11th to 20th	Day	73% 6% 7% 6% 4 3	2645
	21st to end	Day	73% 7% 8% 7% 5% 1	3146
February	1st to 10th	Day	70% 7% 9% 9% 5% 1	1710
	11th to 20th	Day	68% 8% 10% 8% 4 2	1674
	21st to end	Day	71% 6% 8% 8% 5% 2	1465
March	1st to 10th	Day	64% 8% 11% 13% 3	3403
	11th to 20th	Day	52% 6% 9% 21% 11% 1	3490
	21st to end	Day	71% 10% 8% 7% 3	3825
April	1st to 10th	Day	71% 6% 11% 8% 4	2280
	11th to 20th	Day	64% 7% 10% 10% 6% 2	2265
	21st to end	Day	59% 8% 13% 13% 6% 1	2470
May	1st to 10th	Day	50% 9% 13% 17% 11%	4189
	11th to 20th	Day	31% 5% 17% 31% 14% 1	4380
	21st to end	Day	46% 12% 25% 15% 2	4814
June	1st to 10th	Day	52% 7% 14% 21% 6%	2660
	11th to 20th	Day	46% 9% 18% 20% 6%	2660
	21st to end	Day	29% 6% 17% 30% 14% 3	2660
July	1st to 10th	Day	13% 4 10% 15% 26% 32%	4351
	11th to 20th	Day	17% 4 6% 18% 32% 24%	4345
	21st to end	Day	13% 3 10% 26% 38% 10%	4463
August	1st to 10th	Day	18% 5% 11% 25% 31% 11%	4076
	11th to 20th	Day	22% 6% 15% 37% 16% 3	4065
	21st to end	Day	25% 6% 12% 25% 24% 8%	4321
September	1st to 10th	Day	20% 5% 11% 29% 23% 12%	2280
	11th to 20th	Day	36% 7% 13% 22% 17% 6%	2218
	21st to end	Day	37% 7% 12% 22% 17% 5%	2035
October	1st to 10th	Day	36% 5% 7% 16% 24% 10%	3180
	11th to 20th	Day	48% 9% 15% 16% 11% 1	3161
	21st to end	Day	56% 8% 9% 15% 11% 2	3448
November	1st to 10th	Day	66% 8% 9% 12% 4	1646
	11th to 20th	Day	66% 7% 9% 8% 7% 3	1520
	21st to end	Day	62% 7% 8% 7% 12% 4	1520
December	1st to 10th	Day	61% 7% 10% 11% 11% 1	1520
	11th to 20th	Day	68% 11% 9% 8% 3	1928
	21st to end	Day	75% 8% 8% 6% 2 1	2794
January	1st to 10th	Night	80% 6% 6% 4 3 1	4406
	11th to 20th	Night	73% 7% 6% 8% 4 2	4314
	21st to end	Night	74% 4 7% 8% 6% 1	4521
February	1st to 10th	Night	66% 8% 11% 11% 4 1	2470
	11th to 20th	Night	61% 7% 12% 12% 7% 2	2404
	21st to end	Night	64% 9% 9% 11% 6% 2	1989
March	1st to 10th	Night	62% 7% 13% 14% 3	3466
	11th to 20th	Night	49% 7% 13% 18% 10% 2	3490
	21st to end	Night	67% 9% 13% 10% 2	3828
April	1st to 10th	Night	63% 8% 11% 12% 4 1	1900
	11th to 20th	Night	53% 8% 15% 16% 4 3	1861
	21st to end	Night	52% 9% 12% 18% 7% 2	1710
May	1st to 10th	Night	47% 8% 13% 21% 10% 1	2778
	11th to 20th	Night	29% 6% 14% 35% 12% 3	2516
	21st to end	Night	37% 12% 32% 17% 2	2762
June	1st to 10th	Night	44% 8% 16% 29% 3 1	1520
	11th to 20th	Night	31% 9% 24% 27% 9% 1	1520
	21st to end	Night	23% 6% 21% 33% 13% 4	1520
July	1st to 10th	Night	9% 2 11% 19% 24% 34%	2500
	11th to 20th	Night	14% 4 8% 18% 27% 29%	2492
	21st to end	Night	13% 3 10% 29% 36% 8%	2854
August	1st to 10th	Night	13% 5% 12% 29% 30% 10%	2839
	11th to 20th	Night	22% 8% 17% 33% 16% 4	2839
	21st to end	Night	19% 5% 12% 31% 26% 7%	3338
September	1st to 10th	Night	18% 6% 12% 27% 25% 13%	1900
	11th to 20th	Night	31% 6% 15% 25% 15% 8%	1958
	21st to end	Night	31% 7% 15% 23% 17% 8%	2144
October	1st to 10th	Night	30% 6% 9% 23% 24% 8%	3800
	11th to 20th	Night	45% 9% 16% 18% 10% 2	3777
	21st to end	Night	58% 7% 9% 14% 9% 3	4121
November	1st to 10th	Night	59% 8% 11% 12% 9% 1	2526
	11th to 20th	Night	64% 7% 10% 10% 6% 3	2660
	21st to end	Night	56% 8% 11% 9% 11% 5%	2660
December	1st to 10th	Night	59% 5% 11% 14% 10% 1	2660
	11th to 20th	Night	68% 8% 11% 9% 5%	3276
	21st to end	Night	68% 13% 8% 7% 2 1	4862

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	49% 17% 18% 9% 7%	180
	11th to 20th	Day	44% 12% 18% 16% 9% 1	246
	21st to end	Day	37% 12% 19% 20% 11% 1	407
February	1st to 10th	Day	40% 11% 20% 21% 7% 1	370
	11th to 20th	Day	40% 16% 18% 21% 5% 1	365
	21st to end	Day	42% 17% 18% 18% 5%	332
March	1st to 10th	Day	40% 17% 21% 17% 5% 1	460
	11th to 20th	Day	33% 15% 22% 20% 8% 1	460
	21st to end	Day	40% 17% 21% 16% 6%	506
April	1st to 10th	Day	39% 16% 17% 18% 9% 1	460
	11th to 20th	Day	36% 20% 21% 15% 5% 3	452
	21st to end	Day	30% 17% 26% 18% 7% 2	460
May	1st to 10th	Day	22% 18% 29% 19% 9% 3	463
	11th to 20th	Day	30% 13% 24% 19% 9% 4	488
	21st to end	Day	22% 15% 25% 23% 12% 2	529
June	1st to 10th	Day	24% 13% 26% 25% 11% 2	490
	11th to 20th	Day	19% 20% 29% 22% 9% 1	490
	21st to end	Day	10% 10% 28% 35% 14% 2	490
July	1st to 10th	Day	6% 8% 33% 34% 16% 3	486
	11th to 20th	Day	5% 9% 32% 34% 17% 2	484
	21st to end	Day	2 6% 29% 41% 17% 4	531
August	1st to 10th	Day	4 8% 28% 39% 17% 5%	487
	11th to 20th	Day	5% 6% 22% 40% 22% 6%	477
	21st to end	Day	8% 9% 30% 32% 18% 4	539
September	1st to 10th	Day	8% 8% 29% 32% 20% 3	490
	11th to 20th	Day	16% 9% 26% 30% 16% 3	490
	21st to end	Day	19% 11% 27% 29% 10% 4	490
October	1st to 10th	Day	22% 11% 25% 23% 16% 3	490
	11th to 20th	Day	23% 12% 19% 25% 17% 4	490
	21st to end	Day	32% 13% 23% 21% 7% 4	539
November	1st to 10th	Day	38% 13% 20% 20% 7% 1	276
	11th to 20th	Day	35% 11% 29% 16% 7% 2	180
	21st to end	Day	34% 14% 18% 28% 6%	180
December	1st to 10th	Day	37% 11% 23% 19% 9% 1	180
	11th to 20th	Day	43% 11% 28% 14% 3 1	180
	21st to end	Day	41% 14% 21% 19% 5%	198
January	1st to 10th	Night	47% 9% 15% 18% 9% 2	760
	11th to 20th	Night	40% 8% 14% 22% 14% 2	760
	21st to end	Night	36% 6% 14% 28% 13% 2	836
February	1st to 10th	Night	35% 9% 13% 28% 14% 2	760
	11th to 20th	Night	35% 7% 16% 29% 12% 1	744
	21st to end	Night	38% 11% 13% 25% 13%	628
March	1st to 10th	Night	36% 10% 16% 27% 11% 1	760
	11th to 20th	Night	32% 9% 15% 28% 14% 1	760
	21st to end	Night	38% 9% 17% 22% 14% 1	836
April	1st to 10th	Night	37% 9% 14% 23% 16% 1	760
	11th to 20th	Night	26% 12% 21% 24% 15% 2	733
	21st to end	Night	26% 8% 16% 29% 19% 1	570
May	1st to 10th	Night	21% 8% 21% 28% 20% 2	527
	11th to 20th	Night	21% 6% 17% 29% 24% 2	374
	21st to end	Night	18% 7% 20% 31% 23% 1	411
June	1st to 10th	Night	20% 4 15% 38% 21% 2	380
	11th to 20th	Night	14% 5% 19% 44% 16% 2	380
	21st to end	Night	12% 3 15% 41% 29% 1	380
July	1st to 10th	Night	6% 2 13% 42% 36% 1	370
	11th to 20th	Night	7% 2 15% 49% 27%	368
	21st to end	Night	3 3 10% 42% 38% 3	526
August	1st to 10th	Night	4 2 10% 39% 39% 6%	567
	11th to 20th	Night	5% 2 9% 34% 44% 7%	564
	21st to end	Night	8% 4 16% 39% 30% 4	741
September	1st to 10th	Night	8% 4 16% 38% 33% 2	760
	11th to 20th	Night	12% 4 14% 30% 33% 7%	760
	21st to end	Night	16% 5% 14% 34% 28% 3	760
October	1st to 10th	Night	18% 5% 18% 32% 25% 3	760
	11th to 20th	Night	22% 5% 11% 31% 25% 5%	760
	21st to end	Night	30% 10% 16% 24% 16% 4	836
November	1st to 10th	Night	35% 7% 14% 28% 16% 1	760
	11th to 20th	Night	36% 11% 15% 24% 12% 1	760
	21st to end	Night	28% 9% 17% 30% 14% 2	760
December	1st to 10th	Night	32% 8% 17% 26% 16% 2	760
	11th to 20th	Night	41% 8% 16% 21% 14% 1	760
	21st to end	Night	45% 10% 14% 23% 7%	836

Page generated at 2024-11-02 23:11:10. Version ac07

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