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 2024-01-12.

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	19% 11% 4 7% 6% 3 5% 4 5% 6% 30%	74746
	Night	18% 12% 4 7% 6% 3 4 4 4 6% 31%	74971
Transparency	Day	54% 6% 11% 18% 10% 1	74451
	Night	54% 6% 11% 19% 10% 1	74800
Seeing	Day	25% 18% 30% 18% 7% 2	13389
	Night	24% 15% 29% 23% 8% 1	22515

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	17% 21% 6% 11% 7% 4 5% 3 4 3 18%	1517
	11th to 20th	Day	18% 19% 6% 9% 6% 3 5% 3 5% 4 23%	1454
	21st to end	Day	13% 14% 6% 10% 7% 3 5% 5% 5% 5% 25%	1584
February	1st to 10th	Day	14% 17% 6% 11% 9% 3 4 4 4 6% 22%	1611
	11th to 20th	Day	13% 17% 7% 10% 6% 3 4 5% 4 6% 24%	1623
	21st to end	Day	18% 16% 7% 8% 7% 4 4 4 4 4 24%	1480
March	1st to 10th	Day	16% 13% 6% 9% 6% 4 5% 4 4 5% 28%	1797
	11th to 20th	Day	15% 14% 5% 8% 7% 3 4 5% 5% 5% 28%	1908
	21st to end	Day	20% 10% 4 7% 5% 3 3 4 4 5% 35%	2341
April	1st to 10th	Day	21% 13% 4 7% 5% 3 4 3 3 5% 31%	2160
	11th to 20th	Day	21% 10% 4 6% 5% 3 4 3 5% 5% 34%	2134
	21st to end	Day	23% 11% 4 7% 5% 3 4 4 4 6% 29%	2296
May	1st to 10th	Day	21% 10% 3 7% 6% 4 4 4 5% 6% 31%	2520
	11th to 20th	Day	19% 8% 3 6% 6% 3 4 4 5% 6% 34%	2478
	21st to end	Day	19% 8% 3 6% 5% 3 5% 5% 5% 7% 35%	2725
June	1st to 10th	Day	23% 8% 3 7% 6% 3 5% 5% 6% 7% 27%	2520
	11th to 20th	Day	16% 7% 3 5% 6% 4 5% 5% 6% 9% 34%	2520
	21st to end	Day	21% 8% 3 7% 6% 4 6% 5% 5% 8% 27%	2520
July	1st to 10th	Day	13% 6% 3 5% 6% 4 6% 5% 6% 7% 38%	2520
	11th to 20th	Day	16% 6% 3 6% 5% 4 6% 6% 7% 9% 33%	2520
	21st to end	Day	13% 7% 3 6% 6% 4 6% 6% 7% 9% 33%	2744
August	1st to 10th	Day	15% 6% 3 6% 6% 4 6% 5% 5% 8% 34%	2506
	11th to 20th	Day	14% 6% 3 6% 6% 4 5% 5% 6% 9% 36%	2287
	21st to end	Day	16% 7% 3 6% 5% 3 4 5% 6% 8% 38%	2376
September	1st to 10th	Day	17% 7% 3 4 6% 3 4 4 6% 7% 41%	2160
	11th to 20th	Day	16% 5% 2 5% 4 3 4 4 5% 7% 44%	2116
	21st to end	Day	20% 7% 2 5% 4 2 4 5% 6% 6% 39%	1980
October	1st to 10th	Day	23% 8% 3 5% 5% 3 5% 5% 5% 7% 33%	1810
	11th to 20th	Day	25% 11% 4 8% 6% 3 4 5% 4 5% 25%	1792
	21st to end	Day	26% 13% 4 6% 5% 3 4 5% 5% 5% 24%	1782
November	1st to 10th	Day	17% 12% 4 7% 5% 3 5% 5% 6% 6% 31%	1671
	11th to 20th	Day	21% 14% 6% 8% 5% 4 4 4 5% 6% 23%	1576
	21st to end	Day	23% 14% 5% 7% 7% 4 5% 4 4 5% 22%	1520
December	1st to 10th	Day	23% 20% 7% 9% 6% 3 4 4 4 4 17%	1520
	11th to 20th	Day	21% 15% 6% 10% 6% 3 3 4 4 5% 22%	1906
	21st to end	Day	23% 20% 6% 10% 6% 3 3 4 3 4 19%	2772
January	1st to 10th	Night	18% 19% 8% 10% 7% 4 4 4 4 4 17%	2649
	11th to 20th	Night	18% 18% 7% 10% 7% 3 4 4 4 5% 22%	2546
	21st to end	Night	11% 14% 6% 10% 7% 4 5% 4 5% 6% 28%	2772
February	1st to 10th	Night	14% 14% 7% 10% 8% 4 5% 4 5% 6% 23%	2344
	11th to 20th	Night	14% 14% 6% 11% 8% 4 4 3 5% 4 27%	2223
	21st to end	Night	15% 13% 6% 8% 7% 3 4 5% 4 6% 28%	1776
March	1st to 10th	Night	17% 12% 5% 9% 7% 3 5% 5% 4 6% 27%	2150
	11th to 20th	Night	17% 15% 5% 7% 6% 3 4 3 5% 6% 30%	2047
	21st to end	Night	17% 10% 4 6% 5% 3 5% 4 4 5% 38%	2014
April	1st to 10th	Night	23% 11% 3 7% 6% 3 3 3 4 6% 32%	1800
	11th to 20th	Night	20% 10% 3 5% 5% 3 4 4 5% 5% 36%	1775
	21st to end	Night	21% 10% 4 5% 6% 2 4 5% 4 5% 33%	1677
May	1st to 10th	Night	19% 10% 4 6% 6% 3 5% 4 4 5% 34%	1440
	11th to 20th	Night	17% 8% 4 6% 4 3 4 4 4 6% 39%	1415
	21st to end	Night	16% 7% 3 6% 4 3 4 5% 5% 7% 40%	1550
June	1st to 10th	Night	19% 7% 4 6% 6% 3 6% 5% 5% 9% 30%	1440
	11th to 20th	Night	17% 6% 3 8% 5% 3 4 5% 5% 7% 38%	1440
	21st to end	Night	18% 8% 3 5% 5% 3 5% 4 5% 6% 37%	1440
July	1st to 10th	Night	12% 6% 2 6% 4 3 5% 3 5% 9% 45%	1440
	11th to 20th	Night	14% 5% 2 5% 5% 3 5% 5% 6% 9% 41%	1440
	21st to end	Night	13% 5% 3 6% 4 3 5% 6% 7% 7% 41%	1574
August	1st to 10th	Night	12% 6% 2 6% 5% 3 5% 5% 6% 9% 41%	1432
	11th to 20th	Night	13% 5% 2 5% 6% 3 4 5% 6% 8% 43%	1591
	21st to end	Night	14% 5% 3 5% 5% 3 4 4 5% 8% 44%	1980
September	1st to 10th	Night	13% 7% 3 5% 5% 3 4 4 4 6% 45%	1800
	11th to 20th	Night	16% 5% 2 4 4 3 4 4 5% 7% 47%	1843
	21st to end	Night	20% 6% 2 4 4 3 4 4 4 7% 42%	1980
October	1st to 10th	Night	19% 7% 3 6% 5% 3 4 4 5% 6% 37%	2149
	11th to 20th	Night	23% 9% 4 6% 5% 3 4 4 5% 5% 31%	2168
	21st to end	Night	25% 11% 4 7% 7% 3 4 4 4 6% 27%	2574
November	1st to 10th	Night	21% 11% 4 6% 6% 3 4 4 5% 7% 30%	2407
	11th to 20th	Night	20% 11% 5% 9% 5% 3 5% 4 5% 5% 28%	2603
	21st to end	Night	21% 16% 5% 8% 7% 3 5% 4 4 5% 22%	2660
December	1st to 10th	Night	20% 18% 7% 10% 7% 4 4 3 4 5% 18%	2660
	11th to 20th	Night	22% 16% 5% 9% 7% 3 4 4 3 4 23%	3288
	21st to end	Night	24% 21% 5% 8% 6% 2 3 3 3 4 20%	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	70% 6% 6% 13% 5%	1518
	11th to 20th	Day	65% 5% 7% 12% 10% 1	1454
	21st to end	Day	59% 5% 8% 15% 11% 1	1584
February	1st to 10th	Day	64% 4 8% 16% 7% 2	1611
	11th to 20th	Day	61% 4 10% 14% 9% 1	1632
	21st to end	Day	64% 4 7% 14% 9% 2	1480
March	1st to 10th	Day	59% 5% 8% 15% 11% 2	1800
	11th to 20th	Day	57% 5% 10% 14% 11% 3	1908
	21st to end	Day	53% 4 8% 18% 14% 4	2341
April	1st to 10th	Day	56% 3 10% 16% 12% 3	2160
	11th to 20th	Day	52% 4 8% 20% 13% 2	2134
	21st to end	Day	56% 5% 7% 15% 13% 4	2296
May	1st to 10th	Day	54% 5% 7% 18% 13% 3	2520
	11th to 20th	Day	50% 5% 9% 18% 15% 3	2482
	21st to end	Day	49% 6% 11% 18% 14% 2	2725
June	1st to 10th	Day	54% 7% 10% 17% 11% 1	2520
	11th to 20th	Day	47% 7% 12% 20% 12% 3	2520
	21st to end	Day	56% 7% 11% 17% 9% 1	2520
July	1st to 10th	Day	42% 8% 13% 25% 11% 1	2450
	11th to 20th	Day	44% 9% 13% 24% 10%	2445
	21st to end	Day	46% 8% 15% 22% 9%	2591
August	1st to 10th	Day	47% 8% 16% 23% 7%	2492
	11th to 20th	Day	43% 8% 16% 23% 9% 1	2287
	21st to end	Day	44% 6% 13% 24% 12% 1	2376
September	1st to 10th	Day	42% 6% 13% 26% 13%	2160
	11th to 20th	Day	38% 7% 14% 29% 12% 1	2116
	21st to end	Day	44% 6% 14% 26% 9%	1980
October	1st to 10th	Day	50% 6% 11% 22% 10% 1	1810
	11th to 20th	Day	61% 6% 12% 15% 6% 1	1792
	21st to end	Day	61% 6% 12% 14% 6% 1	1782
November	1st to 10th	Day	52% 7% 14% 19% 7% 1	1671
	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	70% 5% 9% 12% 5%	2649
	11th to 20th	Night	65% 6% 9% 11% 8% 1	2546
	21st to end	Night	56% 5% 11% 15% 12% 2	2772
February	1st to 10th	Night	62% 5% 9% 17% 7% 1	2344
	11th to 20th	Night	60% 4 10% 17% 9% 1	2225
	21st to end	Night	57% 5% 10% 16% 11% 2	1776
March	1st to 10th	Night	59% 4 10% 16% 10% 2	2160
	11th to 20th	Night	55% 5% 10% 16% 11% 3	2048
	21st to end	Night	49% 4 9% 19% 15% 4	2014
April	1st to 10th	Night	55% 4 10% 17% 13% 2	1800
	11th to 20th	Night	49% 5% 9% 20% 15% 2	1775
	21st to end	Night	52% 5% 9% 18% 12% 4	1677
May	1st to 10th	Night	52% 5% 6% 19% 14% 4	1440
	11th to 20th	Night	45% 6% 8% 19% 18% 3	1416
	21st to end	Night	43% 7% 11% 21% 15% 2	1551
June	1st to 10th	Night	49% 7% 11% 22% 10%	1440
	11th to 20th	Night	45% 6% 11% 22% 14% 2	1440
	21st to end	Night	47% 9% 10% 20% 13%	1440
July	1st to 10th	Night	37% 7% 14% 27% 15% 1	1400
	11th to 20th	Night	39% 7% 13% 30% 11%	1392
	21st to end	Night	39% 9% 16% 25% 11%	1486
August	1st to 10th	Night	38% 9% 18% 26% 8%	1422
	11th to 20th	Night	38% 8% 17% 27% 11%	1591
	21st to end	Night	38% 7% 16% 28% 11%	1980
September	1st to 10th	Night	40% 6% 13% 26% 14% 1	1800
	11th to 20th	Night	37% 6% 13% 33% 10% 1	1843
	21st to end	Night	41% 6% 11% 29% 12%	1980
October	1st to 10th	Night	48% 6% 10% 24% 12% 1	2149
	11th to 20th	Night	54% 6% 12% 19% 8%	2168
	21st to end	Night	58% 6% 12% 15% 8% 1	2574
November	1st to 10th	Night	53% 6% 14% 19% 7% 1	2407
	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	26% 23% 37% 8% 6% 1	164
	21st to end	Day	25% 20% 36% 14% 4 1	176
February	1st to 10th	Day	40% 27% 29% 3	236
	11th to 20th	Day	26% 35% 32% 7%	290
	21st to end	Day	32% 25% 29% 12% 2	346
March	1st to 10th	Day	27% 22% 33% 15% 2	420
	11th to 20th	Day	31% 23% 28% 13% 4 1	420
	21st to end	Day	31% 21% 24% 17% 5% 2	462
April	1st to 10th	Day	30% 20% 32% 13% 5%	420
	11th to 20th	Day	34% 19% 23% 16% 7% 1	412
	21st to end	Day	31% 19% 33% 12% 4 1	420
May	1st to 10th	Day	26% 22% 32% 15% 4 1	423
	11th to 20th	Day	24% 22% 30% 18% 6% 1	447
	21st to end	Day	24% 19% 32% 19% 5% 1	485
June	1st to 10th	Day	27% 16% 35% 15% 7%	450
	11th to 20th	Day	19% 19% 31% 21% 10% 1	450
	21st to end	Day	26% 14% 33% 18% 7% 2	450
July	1st to 10th	Day	15% 12% 34% 25% 11% 2	445
	11th to 20th	Day	16% 12% 37% 24% 9% 1	444
	21st to end	Day	16% 10% 35% 28% 9% 1	488
August	1st to 10th	Day	18% 10% 29% 30% 10% 2	446
	11th to 20th	Day	16% 8% 28% 30% 13% 6%	439
	21st to end	Day	19% 14% 28% 20% 14% 5%	495
September	1st to 10th	Day	21% 10% 31% 22% 12% 4	450
	11th to 20th	Day	16% 13% 27% 22% 15% 7%	450
	21st to end	Day	21% 17% 24% 23% 11% 5%	450
October	1st to 10th	Day	28% 17% 24% 18% 12% 2	450
	11th to 20th	Day	30% 22% 25% 16% 7% 1	446
	21st to end	Day	35% 14% 30% 16% 4	396
November	1st to 10th	Day	33% 16% 28% 17% 6% 1	365
	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% 20% 28% 17% 6%	728
	21st to end	Night	19% 18% 37% 20% 5% 1	792
February	1st to 10th	Night	22% 22% 34% 18% 4	720
	11th to 20th	Night	23% 23% 34% 16% 4	703
	21st to end	Night	23% 19% 32% 22% 3	592
March	1st to 10th	Night	25% 18% 35% 19% 3	720
	11th to 20th	Night	26% 21% 31% 18% 4 1	720
	21st to end	Night	25% 16% 29% 23% 6% 1	792
April	1st to 10th	Night	29% 17% 27% 23% 4	720
	11th to 20th	Night	26% 16% 31% 21% 7%	711
	21st to end	Night	28% 16% 28% 20% 8%	597
May	1st to 10th	Night	24% 13% 33% 22% 6% 2	360
	11th to 20th	Night	22% 12% 31% 28% 7% 1	354
	21st to end	Night	18% 12% 36% 25% 9%	389
June	1st to 10th	Night	23% 8% 33% 29% 8%	360
	11th to 20th	Night	21% 8% 30% 29% 11% 1	360
	21st to end	Night	21% 6% 25% 34% 13% 1	360
July	1st to 10th	Night	13% 7% 27% 35% 16% 1	350
	11th to 20th	Night	14% 4 25% 38% 17% 1	348
	21st to end	Night	14% 4 28% 39% 13% 2	394
August	1st to 10th	Night	15% 4 20% 43% 17% 1	358
	11th to 20th	Night	14% 4 22% 35% 24% 1	527
	21st to end	Night	18% 6% 26% 33% 16% 2	792
September	1st to 10th	Night	16% 7% 28% 32% 15% 1	720
	11th to 20th	Night	19% 8% 20% 33% 18% 2	720
	21st to end	Night	21% 10% 23% 27% 16% 2	720
October	1st to 10th	Night	23% 14% 26% 25% 12%	720
	11th to 20th	Night	27% 14% 27% 24% 7% 1	720
	21st to end	Night	31% 13% 28% 23% 5%	792
November	1st to 10th	Night	28% 15% 26% 23% 6% 1	740
	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 2024-01-09 16:24:25. Version ac07

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