Ladysmith
Clear Sky Chart
History

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

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	14% 9% 3 8% 5% 4 5% 4 5% 7% 35%	101676
	Night	14% 10% 4 8% 5% 4 4 4 5% 6% 36%	97616
Transparency	Day	46% 7% 13% 23% 10% 1	105207
	Night	47% 6% 12% 23% 11% 1	102225
Seeing	Day	17% 11% 30% 25% 13% 4	16073
	Night	18% 8% 32% 31% 11% 1	25934

By Month

Percentage Cloud Cover SE (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	12% 19% 8% 15% 5% 4 4 3 5% 5% 20%	2527
	11th to 20th	Day	7% 11% 6% 16% 8% 10% 10% 5% 6% 6% 16%	2530
	21st to end	Day	11% 19% 8% 15% 5% 5% 5% 3 5% 6% 18%	2920
February	1st to 10th	Day	8% 14% 5% 10% 5% 4 4 4 6% 8% 32%	1710
	11th to 20th	Day	9% 10% 4 12% 5% 5% 5% 4 5% 7% 34%	1664
	21st to end	Day	12% 11% 5% 11% 7% 5% 4 5% 4 6% 31%	1560
March	1st to 10th	Day	12% 9% 3 6% 4 4 4 3 4 5% 44%	3147
	11th to 20th	Day	9% 9% 3 11% 5% 5% 4 5% 6% 7% 36%	3480
	21st to end	Day	21% 11% 4 11% 5% 4 4 3 4 6% 26%	4004
April	1st to 10th	Day	16% 13% 3 9% 5% 4 4 4 5% 7% 31%	2280
	11th to 20th	Day	22% 9% 4 8% 5% 4 5% 4 5% 5% 30%	2254
	21st to end	Day	21% 11% 3 7% 6% 4 4 4 5% 5% 30%	2404
May	1st to 10th	Day	18% 6% 2 6% 4 4 4 3 6% 6% 40%	4399
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 4 6% 7% 41%	4399
	21st to end	Day	19% 9% 3 7% 5% 4 4 3 5% 6% 35%	4824
June	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 6% 8% 41%	2660
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 7% 37%	2660
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 8% 10% 38%	2660
July	1st to 10th	Day	14% 5% 2 5% 4 4 5% 5% 7% 10% 39%	4440
	11th to 20th	Day	7% 4 2 4 3 4 5% 5% 7% 11% 50%	4440
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 46%	4813
August	1st to 10th	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	4330
	11th to 20th	Day	14% 5% 2 4 3 4 4 4 6% 8% 47%	4041
	21st to end	Day	15% 6% 3 6% 5% 5% 5% 4 6% 7% 38%	4186
September	1st to 10th	Day	12% 6% 2 6% 4 4 5% 3 6% 7% 45%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 4 4 6% 8% 44%	2280
	21st to end	Day	17% 6% 2 6% 5% 4 4 4 5% 8% 41%	2020
October	1st to 10th	Day	17% 7% 2 7% 4 4 4 4 5% 6% 39%	1900
	11th to 20th	Day	17% 13% 3 8% 5% 5% 4 3 6% 6% 31%	1900
	21st to end	Day	20% 11% 3 7% 4 4 4 4 4 6% 33%	1948
November	1st to 10th	Day	14% 12% 3 7% 5% 5% 4 3 5% 7% 34%	1747
	11th to 20th	Day	16% 12% 6% 12% 7% 5% 5% 3 5% 5% 24%	1528
	21st to end	Day	15% 13% 4 9% 5% 4 5% 4 6% 8% 29%	1520
December	1st to 10th	Day	11% 14% 6% 15% 8% 6% 5% 4 5% 6% 20%	1520
	11th to 20th	Day	13% 16% 7% 12% 7% 5% 5% 4 5% 5% 20%	1918
	21st to end	Day	24% 19% 6% 14% 5% 4 3 2 2 3 17%	2783
January	1st to 10th	Night	11% 14% 8% 14% 6% 5% 4 3 5% 4 26%	4428
	11th to 20th	Night	8% 12% 5% 16% 8% 8% 8% 5% 6% 5% 19%	4440
	21st to end	Night	11% 21% 10% 14% 6% 4 4 3 4 4 19%	4744
February	1st to 10th	Night	7% 11% 5% 10% 7% 6% 4 4 6% 6% 33%	2470
	11th to 20th	Night	8% 11% 4 8% 6% 5% 5% 4 6% 7% 36%	2403
	21st to end	Night	13% 12% 4 8% 7% 5% 5% 4 6% 6% 32%	1894
March	1st to 10th	Night	9% 6% 2 6% 5% 4 5% 4 6% 8% 45%	3733
	11th to 20th	Night	9% 9% 4 10% 6% 5% 4 3 6% 6% 38%	3480
	21st to end	Night	23% 13% 5% 10% 5% 4 4 3 3 4 27%	3626
April	1st to 10th	Night	19% 11% 3 7% 4 3 5% 3 5% 7% 34%	1900
	11th to 20th	Night	24% 8% 3 6% 4 4 3 3 4 6% 35%	1875
	21st to end	Night	20% 9% 2 6% 4 3 4 3 7% 7% 35%	1773
May	1st to 10th	Night	18% 7% 2 7% 4 5% 4 4 5% 8% 36%	2506
	11th to 20th	Night	15% 5% 2 5% 4 3 4 3 4 5% 51%	2506
	21st to end	Night	15% 6% 2 7% 5% 4 4 4 5% 8% 39%	2743
June	1st to 10th	Night	13% 5% 2 6% 4 3 4 3 8% 9% 43%	1520
	11th to 20th	Night	11% 7% 2 6% 5% 4 4 4 7% 8% 43%	1520
	21st to end	Night	9% 6% 2 5% 5% 5% 5% 4 6% 9% 44%	1520
July	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 6% 8% 47%	2530
	11th to 20th	Night	6% 3 1 4 4 3 3 4 7% 9% 56%	2530
	21st to end	Night	9% 5% 2 5% 4 3 4 3 6% 8% 53%	2750
August	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 6% 6% 46%	2606
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 6% 8% 50%	2798
	21st to end	Night	17% 6% 3 5% 4 4 3 4 5% 7% 43%	3468
September	1st to 10th	Night	10% 5% 1 5% 4 3 4 3 5% 6% 53%	1900
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 5% 7% 49%	1900
	21st to end	Night	14% 5% 2 6% 4 4 4 3 5% 7% 45%	2139
October	1st to 10th	Night	14% 6% 2 6% 4 3 4 3 5% 6% 47%	2280
	11th to 20th	Night	15% 9% 3 8% 4 4 4 3 5% 5% 38%	2280
	21st to end	Night	19% 10% 3 8% 5% 4 4 4 5% 6% 33%	2650
November	1st to 10th	Night	17% 10% 3 6% 4 4 4 3 4 8% 37%	2546
	11th to 20th	Night	14% 12% 5% 10% 5% 5% 4 3 5% 7% 31%	2675
	21st to end	Night	14% 11% 4 9% 5% 5% 5% 4 5% 7% 32%	2660
December	1st to 10th	Night	11% 15% 6% 11% 7% 5% 4 3 5% 6% 27%	2660
	11th to 20th	Night	13% 15% 6% 11% 7% 5% 5% 4 5% 6% 23%	3279
	21st to end	Night	25% 17% 6% 10% 5% 4 3 3 4 5% 19%	4884

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	64% 7% 9% 15% 4	2528
	11th to 20th	Day	67% 8% 7% 12% 6%	2530
	21st to end	Day	65% 6% 12% 13% 4	2920
February	1st to 10th	Day	49% 6% 13% 20% 10% 1	1710
	11th to 20th	Day	49% 5% 13% 22% 9% 1	1673
	21st to end	Day	54% 6% 11% 19% 9% 2	1560
March	1st to 10th	Day	41% 6% 16% 21% 15% 2	3147
	11th to 20th	Day	43% 8% 14% 22% 12% 1	3480
	21st to end	Day	60% 5% 9% 19% 6% 1	4004
April	1st to 10th	Day	52% 7% 10% 19% 12% 1	2280
	11th to 20th	Day	54% 6% 10% 18% 10% 2	2254
	21st to end	Day	56% 6% 11% 17% 10%	2404
May	1st to 10th	Day	41% 8% 11% 27% 11% 2	4440
	11th to 20th	Day	40% 8% 15% 24% 12% 1	4403
	21st to end	Day	49% 7% 11% 20% 13% 1	4837
June	1st to 10th	Day	38% 9% 14% 27% 12% 1	2660
	11th to 20th	Day	44% 9% 12% 20% 13% 1	2660
	21st to end	Day	38% 9% 18% 24% 10% 1	2660
July	1st to 10th	Day	38% 8% 17% 27% 10%	4371
	11th to 20th	Day	26% 7% 18% 33% 14% 1	4365
	21st to end	Day	34% 7% 15% 28% 16%	4662
August	1st to 10th	Day	39% 6% 16% 24% 13% 1	4315
	11th to 20th	Day	34% 7% 14% 34% 10%	4080
	21st to end	Day	43% 7% 15% 23% 11% 1	4185
September	1st to 10th	Day	37% 7% 15% 28% 13%	2280
	11th to 20th	Day	37% 8% 19% 29% 7% 1	2280
	21st to end	Day	42% 6% 14% 29% 9%	2020
October	1st to 10th	Day	30% 5% 12% 34% 18%	3160
	11th to 20th	Day	46% 4 10% 24% 14% 1	3140
	21st to end	Day	46% 4 18% 23% 8%	3186
November	1st to 10th	Day	49% 7% 12% 20% 11% 1	1747
	11th to 20th	Day	60% 7% 13% 14% 6% 1	1528
	21st to end	Day	52% 6% 16% 18% 6% 1	1520
December	1st to 10th	Day	64% 7% 13% 13% 4	1520
	11th to 20th	Day	63% 6% 12% 13% 4 1	1915
	21st to end	Day	74% 4 7% 10% 5%	2783
January	1st to 10th	Night	60% 7% 11% 17% 5% 1	4428
	11th to 20th	Night	63% 7% 11% 13% 5%	4440
	21st to end	Night	66% 6% 8% 15% 5%	4744
February	1st to 10th	Night	50% 6% 11% 21% 10% 1	2470
	11th to 20th	Night	46% 7% 13% 23% 9% 1	2404
	21st to end	Night	51% 7% 14% 19% 8% 2	1894
March	1st to 10th	Night	36% 7% 16% 26% 13% 2	3733
	11th to 20th	Night	44% 8% 11% 24% 12% 1	3480
	21st to end	Night	62% 4 7% 17% 9% 1	3626
April	1st to 10th	Night	50% 6% 9% 18% 16% 1	1900
	11th to 20th	Night	50% 5% 9% 19% 13% 3	1875
	21st to end	Night	46% 7% 10% 21% 14% 1	1773
May	1st to 10th	Night	44% 8% 14% 16% 17% 1	2530
	11th to 20th	Night	36% 5% 9% 28% 18% 3	2507
	21st to end	Night	40% 9% 15% 21% 14% 1	2751
June	1st to 10th	Night	34% 8% 17% 26% 14% 1	1520
	11th to 20th	Night	37% 8% 14% 22% 16% 2	1520
	21st to end	Night	34% 9% 16% 28% 12% 2	1520
July	1st to 10th	Night	34% 7% 19% 25% 14% 1	2490
	11th to 20th	Night	24% 6% 14% 37% 17% 2	2482
	21st to end	Night	29% 6% 14% 31% 19% 2	2662
August	1st to 10th	Night	38% 5% 14% 27% 13% 2	2597
	11th to 20th	Night	33% 6% 15% 32% 12% 2	2825
	21st to end	Night	41% 7% 14% 26% 11% 2	3468
September	1st to 10th	Night	31% 7% 13% 32% 16% 1	1900
	11th to 20th	Night	33% 7% 16% 32% 12%	1900
	21st to end	Night	37% 6% 14% 30% 11% 1	2139
October	1st to 10th	Night	28% 4 8% 34% 23% 3	3800
	11th to 20th	Night	38% 5% 12% 27% 17% 1	3779
	21st to end	Night	52% 5% 10% 22% 11%	4362
November	1st to 10th	Night	46% 6% 13% 23% 12%	2546
	11th to 20th	Night	53% 7% 15% 15% 10% 1	2675
	21st to end	Night	52% 6% 15% 20% 6% 1	2660
December	1st to 10th	Night	58% 7% 12% 18% 5%	2660
	11th to 20th	Night	60% 7% 11% 16% 4	3281
	21st to end	Night	68% 5% 8% 14% 4	4884

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	17% 12% 34% 24% 10% 3	270
	11th to 20th	Day	19% 13% 37% 23% 8% 1	270
	21st to end	Day	18% 9% 36% 27% 9%	297
February	1st to 10th	Day	14% 13% 47% 17% 7% 2	270
	11th to 20th	Day	14% 17% 45% 18% 5% 1	270
	21st to end	Day	16% 14% 47% 22% 1	225
March	1st to 10th	Day	17% 15% 40% 19% 7% 1	270
	11th to 20th	Day	18% 13% 39% 18% 9% 3	270
	21st to end	Day	25% 14% 30% 20% 7% 4	410
April	1st to 10th	Day	20% 17% 35% 21% 5% 1	460
	11th to 20th	Day	27% 13% 28% 23% 8% 1	452
	21st to end	Day	27% 14% 27% 22% 8% 2	545
May	1st to 10th	Day	22% 14% 30% 26% 8% 1	653
	11th to 20th	Day	20% 12% 27% 24% 13% 4	675
	21st to end	Day	21% 10% 27% 23% 16% 4	734
June	1st to 10th	Day	12% 9% 30% 28% 16% 4	680
	11th to 20th	Day	14% 9% 34% 29% 11% 3	680
	21st to end	Day	13% 8% 31% 26% 15% 6%	680
July	1st to 10th	Day	10% 5% 20% 31% 24% 11%	671
	11th to 20th	Day	11% 8% 25% 30% 17% 9%	668
	21st to end	Day	8% 4 28% 31% 20% 9%	739
August	1st to 10th	Day	12% 7% 24% 28% 23% 7%	676
	11th to 20th	Day	15% 6% 18% 30% 25% 7%	665
	21st to end	Day	15% 7% 23% 29% 20% 5%	545
September	1st to 10th	Day	13% 9% 24% 29% 20% 4	490
	11th to 20th	Day	12% 6% 29% 32% 19% 3	490
	21st to end	Day	20% 10% 27% 26% 14% 3	408
October	1st to 10th	Day	16% 13% 26% 30% 11% 3	300
	11th to 20th	Day	22% 19% 34% 18% 6% 1	300
	21st to end	Day	26% 13% 39% 17% 4 1	330
November	1st to 10th	Day	20% 13% 36% 22% 8% 1	300
	11th to 20th	Day	21% 19% 35% 20% 5%	273
	21st to end	Day	21% 16% 37% 20% 6%	270
December	1st to 10th	Day	14% 16% 41% 21% 8% 1	270
	11th to 20th	Day	23% 17% 33% 20% 7% 1	270
	21st to end	Day	27% 15% 36% 18% 3	297
January	1st to 10th	Night	14% 10% 38% 28% 9%	950
	11th to 20th	Night	19% 9% 36% 28% 6% 2	950
	21st to end	Night	19% 9% 35% 31% 6%	1045
February	1st to 10th	Night	14% 9% 40% 30% 6% 1	950
	11th to 20th	Night	14% 13% 39% 27% 7%	929
	21st to end	Night	19% 11% 37% 28% 5%	638
March	1st to 10th	Night	16% 13% 35% 29% 7% 1	760
	11th to 20th	Night	17% 12% 34% 29% 8% 1	570
	21st to end	Night	22% 10% 30% 29% 8% 2	627
April	1st to 10th	Night	22% 10% 33% 28% 6% 1	570
	11th to 20th	Night	29% 9% 27% 28% 7%	563
	21st to end	Night	24% 8% 30% 31% 7% 1	570
May	1st to 10th	Night	23% 9% 33% 28% 6% 1	570
	11th to 20th	Night	19% 8% 32% 30% 9% 2	561
	21st to end	Night	16% 7% 26% 36% 14% 1	617
June	1st to 10th	Night	12% 8% 30% 38% 11%	570
	11th to 20th	Night	15% 5% 30% 41% 8% 1	570
	21st to end	Night	13% 4 24% 44% 14% 1	570
July	1st to 10th	Night	8% 2 24% 37% 26% 3	555
	11th to 20th	Night	11% 3 25% 39% 20% 2	552
	21st to end	Night	8% 2 18% 48% 23% 2	624
August	1st to 10th	Night	10% 4 17% 45% 22% 2	567
	11th to 20th	Night	15% 2 20% 33% 27% 3	564
	21st to end	Night	16% 4 21% 33% 24% 1	627
September	1st to 10th	Night	11% 4 23% 41% 18% 4	570
	11th to 20th	Night	13% 3 29% 34% 18% 3	570
	21st to end	Night	16% 7% 30% 32% 13% 1	728
October	1st to 10th	Night	17% 8% 30% 31% 14% 1	760
	11th to 20th	Night	19% 11% 33% 29% 8%	760
	21st to end	Night	24% 11% 28% 29% 8%	836
November	1st to 10th	Night	22% 7% 33% 28% 8% 1	790
	11th to 20th	Night	20% 12% 37% 24% 7%	956
	21st to end	Night	20% 13% 36% 25% 6%	950
December	1st to 10th	Night	18% 10% 38% 27% 7% 1	950
	11th to 20th	Night	21% 9% 38% 23% 7% 1	950
	21st to end	Night	26% 10% 35% 23% 6% 1	1045

Page generated at 2024-11-08 21:45:37. Version ac07

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