Lake MacDonald
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake MacDonald clear sky chart from 2005-11-06 to 2024-11-08.

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	17% 11% 4 8% 5% 5% 4 4 5% 6% 30%	101600
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	97493
Transparency	Day	53% 6% 12% 19% 9% 1	105049
	Night	53% 6% 12% 19% 9% 1	102133
Seeing	Day	25% 18% 30% 18% 7% 2	14513
	Night	24% 15% 29% 24% 8% 1	23496

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	16% 20% 6% 15% 6% 4 4 3 4 4 17%	2517
	11th to 20th	Day	14% 16% 6% 17% 8% 4 3 3 4 4 20%	2520
	21st to end	Day	12% 17% 8% 13% 7% 5% 5% 5% 5% 4 18%	2772
February	1st to 10th	Day	13% 18% 5% 13% 7% 5% 3 3 4 5% 23%	1700
	11th to 20th	Day	12% 18% 7% 11% 6% 4 4 4 4 6% 24%	1715
	21st to end	Day	17% 17% 6% 9% 6% 5% 3 3 5% 4 24%	1570
March	1st to 10th	Day	18% 16% 5% 10% 5% 5% 4 3 4 5% 25%	3116
	11th to 20th	Day	12% 19% 6% 13% 6% 4 4 3 5% 4 24%	3352
	21st to end	Day	14% 10% 3 9% 6% 5% 4 3 4 5% 37%	4117
April	1st to 10th	Day	20% 15% 3 8% 4 4 4 2 4 5% 31%	2280
	11th to 20th	Day	22% 11% 4 7% 4 4 4 2 4 5% 33%	2254
	21st to end	Day	22% 11% 4 8% 5% 4 4 3 4 5% 30%	2425
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 5% 4 6% 6% 27%	4426
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	4398
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 8% 35%	4837
June	1st to 10th	Day	22% 9% 3 8% 6% 4 5% 4 6% 7% 27%	2660
	11th to 20th	Day	16% 8% 3 6% 5% 5% 5% 4 6% 8% 33%	2660
	21st to end	Day	22% 9% 3 8% 5% 5% 5% 4 6% 7% 26%	2660
July	1st to 10th	Day	13% 8% 3 8% 6% 5% 6% 5% 7% 8% 32%	4440
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 7% 9% 33%	4440
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 8% 43%	4814
August	1st to 10th	Day	17% 6% 3 8% 6% 6% 6% 4 6% 9% 30%	4423
	11th to 20th	Day	15% 8% 3 7% 4 5% 4 5% 6% 8% 35%	4011
	21st to end	Day	16% 5% 2 7% 4 4 5% 4 6% 9% 37%	4180
September	1st to 10th	Day	16% 7% 2 5% 5% 4 4 3 6% 7% 41%	2280
	11th to 20th	Day	15% 5% 2 6% 3 4 4 3 5% 7% 45%	2233
	21st to end	Day	20% 7% 2 5% 3 3 4 4 6% 6% 39%	2090
October	1st to 10th	Day	22% 9% 3 6% 4 4 4 3 5% 7% 33%	1910
	11th to 20th	Day	24% 12% 4 9% 5% 4 4 4 5% 5% 26%	1891
	21st to end	Day	25% 13% 4 7% 5% 4 4 4 5% 5% 25%	1881
November	1st to 10th	Day	17% 13% 3 8% 4 5% 4 4 6% 6% 30%	1734
	11th to 20th	Day	20% 15% 5% 9% 5% 5% 5% 3 6% 5% 23%	1576
	21st to end	Day	23% 15% 5% 8% 6% 5% 5% 3 4 5% 21%	1520
December	1st to 10th	Day	22% 22% 6% 10% 5% 4 4 3 5% 4 17%	1520
	11th to 20th	Day	21% 16% 5% 12% 5% 4 4 3 4 4 22%	1906
	21st to end	Day	23% 20% 6% 11% 5% 3 4 3 3 4 19%	2772
January	1st to 10th	Night	16% 19% 7% 11% 5% 4 4 3 4 5% 21%	4429
	11th to 20th	Night	12% 15% 6% 15% 8% 5% 4 3 4 6% 20%	4440
	21st to end	Night	12% 17% 8% 14% 7% 6% 5% 3 4 5% 19%	4884
February	1st to 10th	Night	14% 16% 6% 11% 7% 5% 5% 3 4 5% 23%	2475
	11th to 20th	Night	13% 15% 6% 12% 7% 6% 3 3 5% 4 27%	2350
	21st to end	Night	14% 15% 5% 10% 6% 4 4 4 4 6% 27%	1884
March	1st to 10th	Night	20% 13% 4 8% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	15% 21% 4 9% 5% 4 4 3 4 5% 27%	3589
	21st to end	Night	14% 11% 4 9% 5% 5% 5% 3 4 5% 36%	3514
April	1st to 10th	Night	22% 12% 2 7% 5% 4 3 2 4 6% 32%	1900
	11th to 20th	Night	20% 11% 3 6% 5% 4 4 3 5% 5% 34%	1875
	21st to end	Night	20% 11% 3 7% 5% 3 4 4 4 5% 34%	1769
May	1st to 10th	Night	18% 10% 3 8% 5% 4 5% 3 6% 7% 31%	2514
	11th to 20th	Night	19% 8% 3 6% 3 4 4 3 4 7% 38%	2495
	21st to end	Night	18% 7% 3 7% 4 5% 5% 4 6% 7% 35%	2738
June	1st to 10th	Night	19% 8% 2 7% 5% 5% 5% 4 5% 9% 30%	1520
	11th to 20th	Night	16% 7% 2 8% 4 4 4 3 6% 7% 38%	1520
	21st to end	Night	20% 9% 2 7% 4 4 4 4 5% 6% 36%	1520
July	1st to 10th	Night	14% 8% 3 9% 5% 6% 5% 3 5% 7% 35%	2520
	11th to 20th	Night	17% 7% 2 6% 4 4 4 3 6% 8% 40%	2520
	21st to end	Night	12% 5% 2 5% 3 4 5% 5% 6% 7% 45%	2739
August	1st to 10th	Night	15% 7% 3 8% 5% 4 4 4 5% 8% 38%	2506
	11th to 20th	Night	17% 7% 2 5% 4 3 4 4 6% 7% 40%	2781
	21st to end	Night	15% 6% 3 7% 4 3 4 3 5% 7% 42%	3476
September	1st to 10th	Night	13% 7% 2 7% 4 3 4 3 5% 6% 46%	1900
	11th to 20th	Night	16% 5% 2 5% 3 4 4 3 5% 7% 48%	1946
	21st to end	Night	19% 7% 2 5% 3 3 4 3 4 8% 42%	2090
October	1st to 10th	Night	18% 8% 3 7% 4 4 4 3 5% 5% 37%	2269
	11th to 20th	Night	22% 10% 4 8% 4 5% 4 3 5% 5% 31%	2289
	21st to end	Night	24% 11% 4 8% 5% 3 4 3 4 6% 28%	2717
November	1st to 10th	Night	21% 12% 4 7% 5% 4 3 3 5% 6% 30%	2505
	11th to 20th	Night	19% 12% 4 10% 5% 5% 4 3 5% 5% 28%	2603
	21st to end	Night	21% 17% 4 9% 6% 4 4 3 5% 4 22%	2660
December	1st to 10th	Night	20% 20% 6% 11% 7% 5% 4 3 4 4 18%	2660
	11th to 20th	Night	21% 17% 4 11% 5% 4 3 3 3 4 23%	3288
	21st to end	Night	24% 21% 5% 9% 5% 3 3 3 3 4 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	69% 7% 9% 11% 4	2518
	11th to 20th	Day	67% 6% 6% 14% 6% 1	2520
	21st to end	Day	66% 7% 9% 11% 6% 1	2772
February	1st to 10th	Day	63% 4 8% 17% 7% 2	1700
	11th to 20th	Day	61% 5% 10% 14% 9% 1	1724
	21st to end	Day	63% 4 7% 14% 9% 2	1570
March	1st to 10th	Day	61% 6% 8% 15% 10% 1	3119
	11th to 20th	Day	62% 4 11% 13% 9% 2	3352
	21st to end	Day	48% 4 8% 20% 18% 2	4117
April	1st to 10th	Day	56% 3 10% 17% 11% 3	2280
	11th to 20th	Day	53% 4 8% 20% 13% 2	2254
	21st to end	Day	56% 5% 7% 15% 13% 4	2425
May	1st to 10th	Day	54% 7% 8% 20% 8% 2	4440
	11th to 20th	Day	49% 9% 16% 17% 8% 2	4402
	21st to end	Day	48% 6% 11% 20% 14% 1	4837
June	1st to 10th	Day	54% 7% 10% 17% 11% 1	2660
	11th to 20th	Day	47% 7% 12% 20% 12% 3	2660
	21st to end	Day	56% 7% 11% 17% 9% 1	2660
July	1st to 10th	Day	46% 8% 13% 24% 8%	4370
	11th to 20th	Day	45% 8% 16% 25% 7%	4365
	21st to end	Day	39% 7% 14% 31% 9%	4661
August	1st to 10th	Day	50% 7% 16% 21% 7%	4409
	11th to 20th	Day	45% 7% 16% 26% 6%	4053
	21st to end	Day	43% 6% 16% 22% 12% 1	4180
September	1st to 10th	Day	41% 6% 14% 26% 12%	2280
	11th to 20th	Day	37% 7% 14% 30% 12% 1	2233
	21st to end	Day	44% 6% 14% 26% 10%	2090
October	1st to 10th	Day	48% 5% 12% 27% 7%	3170
	11th to 20th	Day	49% 7% 14% 23% 7%	3119
	21st to end	Day	50% 6% 20% 16% 7% 1	3081
November	1st to 10th	Day	52% 7% 14% 19% 7% 1	1734
	11th to 20th	Day	61% 6% 12% 12% 9%	1576
	21st to end	Day	63% 7% 12% 13% 4 1	1520
December	1st to 10th	Day	71% 4 10% 10% 4	1520
	11th to 20th	Day	64% 6% 12% 13% 5%	1906
	21st to end	Day	70% 5% 6% 13% 6%	2772
January	1st to 10th	Night	65% 6% 15% 11% 3	4429
	11th to 20th	Night	64% 7% 12% 12% 5% 1	4440
	21st to end	Night	66% 6% 10% 9% 7% 1	4884
February	1st to 10th	Night	61% 5% 9% 17% 7% 1	2475
	11th to 20th	Night	60% 4 10% 17% 9% 1	2352
	21st to end	Night	57% 5% 10% 16% 10% 2	1884
March	1st to 10th	Night	57% 4 10% 16% 10% 3	3734
	11th to 20th	Night	59% 5% 11% 15% 9% 2	3590
	21st to end	Night	50% 3 8% 21% 14% 3	3514
April	1st to 10th	Night	54% 4 9% 17% 13% 2	1900
	11th to 20th	Night	50% 5% 9% 20% 14% 1	1875
	21st to end	Night	52% 5% 9% 18% 13% 3	1769
May	1st to 10th	Night	52% 7% 10% 20% 8% 2	2520
	11th to 20th	Night	44% 9% 13% 19% 13% 2	2496
	21st to end	Night	47% 6% 10% 20% 15% 2	2739
June	1st to 10th	Night	49% 7% 11% 22% 11%	1520
	11th to 20th	Night	44% 6% 12% 22% 14% 2	1520
	21st to end	Night	49% 8% 10% 19% 13% 1	1520
July	1st to 10th	Night	47% 6% 16% 20% 11%	2480
	11th to 20th	Night	42% 6% 17% 28% 6%	2472
	21st to end	Night	35% 8% 18% 27% 12%	2651
August	1st to 10th	Night	44% 7% 15% 27% 7%	2496
	11th to 20th	Night	43% 6% 18% 27% 7%	2805
	21st to end	Night	41% 6% 16% 24% 11% 2	3476
September	1st to 10th	Night	39% 6% 13% 27% 14% 1	1900
	11th to 20th	Night	36% 6% 14% 33% 11% 1	1946
	21st to end	Night	41% 6% 12% 28% 13%	2090
October	1st to 10th	Night	45% 6% 14% 25% 11% 1	3789
	11th to 20th	Night	47% 8% 13% 24% 9%	3800
	21st to end	Night	50% 5% 18% 16% 10% 1	4467
November	1st to 10th	Night	54% 6% 14% 19% 7% 1	2505
	11th to 20th	Night	57% 5% 12% 16% 8% 2	2603
	21st to end	Night	63% 7% 11% 14% 5%	2660
December	1st to 10th	Night	69% 5% 9% 12% 4	2660
	11th to 20th	Night	64% 5% 8% 15% 6% 1	3288
	21st to end	Night	69% 5% 7% 14% 5%	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	27% 22% 32% 16% 3	180
	11th to 20th	Day	27% 23% 36% 8% 6% 1	180
	21st to end	Day	24% 21% 35% 16% 4 1	198
February	1st to 10th	Day	37% 26% 31% 6% 1	265
	11th to 20th	Day	25% 35% 33% 7%	322
	21st to end	Day	31% 25% 29% 12% 2	382
March	1st to 10th	Day	27% 22% 32% 16% 2	460
	11th to 20th	Day	30% 24% 29% 13% 4 1	460
	21st to end	Day	31% 23% 25% 15% 5% 1	506
April	1st to 10th	Day	30% 22% 31% 13% 4	460
	11th to 20th	Day	35% 20% 23% 15% 6% 1	452
	21st to end	Day	32% 19% 33% 11% 3 1	460
May	1st to 10th	Day	26% 22% 32% 15% 4 1	463
	11th to 20th	Day	22% 21% 30% 20% 7% 1	487
	21st to end	Day	25% 18% 32% 20% 5% 1	529
June	1st to 10th	Day	26% 15% 35% 17% 7%	490
	11th to 20th	Day	18% 19% 31% 21% 9% 1	490
	21st to end	Day	28% 15% 32% 17% 7% 2	490
July	1st to 10th	Day	15% 14% 35% 24% 10% 2	485
	11th to 20th	Day	17% 12% 37% 24% 9% 1	484
	21st to end	Day	17% 10% 35% 28% 9% 2	532
August	1st to 10th	Day	19% 10% 30% 30% 9% 2	486
	11th to 20th	Day	17% 8% 28% 30% 12% 5%	479
	21st to end	Day	19% 14% 29% 21% 13% 5%	539
September	1st to 10th	Day	21% 11% 31% 22% 11% 4	490
	11th to 20th	Day	14% 12% 26% 23% 17% 8%	490
	21st to end	Day	21% 16% 24% 23% 11% 5%	490
October	1st to 10th	Day	28% 16% 24% 18% 12% 1	490
	11th to 20th	Day	29% 21% 26% 16% 6% 1	485
	21st to end	Day	34% 15% 31% 16% 3	429
November	1st to 10th	Day	34% 17% 27% 16% 6% 1	386
	11th to 20th	Day	28% 24% 32% 11% 5%	236
	21st to end	Day	29% 26% 32% 12% 1	180
December	1st to 10th	Day	34% 17% 32% 13% 3 1	180
	11th to 20th	Day	32% 27% 28% 12% 1 1	180
	21st to end	Day	35% 22% 29% 10% 4 1	198
January	1st to 10th	Night	29% 17% 34% 18% 3	760
	11th to 20th	Night	28% 21% 29% 17% 5%	760
	21st to end	Night	19% 18% 36% 20% 5% 1	836
February	1st to 10th	Night	21% 22% 34% 19% 4	760
	11th to 20th	Night	23% 23% 34% 16% 3	743
	21st to end	Night	23% 19% 32% 22% 3	628
March	1st to 10th	Night	25% 18% 34% 20% 3	760
	11th to 20th	Night	26% 22% 31% 18% 4 1	760
	21st to end	Night	25% 17% 30% 22% 6%	836
April	1st to 10th	Night	29% 17% 27% 23% 4	760
	11th to 20th	Night	26% 16% 31% 20% 6%	751
	21st to end	Night	28% 16% 29% 19% 7%	629
May	1st to 10th	Night	24% 13% 33% 22% 6% 2	380
	11th to 20th	Night	22% 11% 30% 28% 8% 1	374
	21st to end	Night	18% 12% 37% 25% 9%	411
June	1st to 10th	Night	22% 8% 32% 30% 8%	380
	11th to 20th	Night	21% 8% 29% 29% 11% 1	380
	21st to end	Night	23% 6% 25% 33% 13% 1	380
July	1st to 10th	Night	14% 7% 27% 36% 15% 1	370
	11th to 20th	Night	14% 5% 26% 38% 17% 1	368
	21st to end	Night	14% 4 27% 39% 14% 1	416
August	1st to 10th	Night	15% 3 20% 44% 17% 1	378
	11th to 20th	Night	14% 5% 22% 33% 24% 1	557
	21st to end	Night	18% 6% 25% 33% 16% 2	836
September	1st to 10th	Night	16% 7% 29% 32% 14% 1	760
	11th to 20th	Night	18% 8% 19% 32% 21% 2	760
	21st to end	Night	21% 10% 24% 27% 16% 2	760
October	1st to 10th	Night	23% 14% 25% 26% 12% 1	760
	11th to 20th	Night	27% 14% 28% 24% 7% 1	760
	21st to end	Night	31% 13% 29% 22% 5%	836
November	1st to 10th	Night	29% 15% 26% 23% 6% 1	771
	11th to 20th	Night	26% 18% 31% 15% 8% 1	760
	21st to end	Night	31% 19% 27% 17% 6%	760
December	1st to 10th	Night	31% 19% 29% 17% 4	760
	11th to 20th	Night	30% 21% 27% 17% 4 1	760
	21st to end	Night	35% 18% 28% 15% 3	836

Page generated at 2024-11-05 08:15:51. Version ac07

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