Millsite Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Millsite Lake clear sky chart from 2005-11-06 to 2024-01-31.

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% 10% 4 7% 6% 3 5% 4 5% 7% 32%	74882
	Night	19% 11% 4 7% 6% 3 4 4 5% 6% 30%	75244
Transparency	Day	53% 6% 11% 19% 10% 1	74587
	Night	56% 5% 11% 18% 9% 1	75073
Seeing	Day	25% 16% 29% 18% 8% 2	13486
	Night	26% 13% 28% 24% 8% 1	22774

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	20% 19% 6% 10% 8% 3 4 4 4 4 18%	1517
	11th to 20th	Day	22% 17% 6% 11% 6% 3 4 4 4 4 20%	1520
	21st to end	Day	15% 17% 6% 10% 9% 6% 5% 4 5% 5% 18%	1773
February	1st to 10th	Day	18% 18% 6% 10% 7% 4 5% 4 4 5% 18%	1620
	11th to 20th	Day	17% 14% 7% 9% 8% 4 5% 4 4 5% 24%	1597
	21st to end	Day	21% 16% 4 10% 7% 4 5% 4 4 5% 21%	1480
March	1st to 10th	Day	17% 14% 7% 11% 6% 3 4 4 3 4 27%	1800
	11th to 20th	Day	19% 12% 4 9% 7% 4 4 3 4 5% 29%	1980
	21st to end	Day	24% 10% 3 6% 5% 2 3 3 3 5% 35%	2292
April	1st to 10th	Day	22% 11% 4 6% 4 2 5% 3 3 5% 34%	2160
	11th to 20th	Day	22% 8% 3 4 5% 3 4 4 4 6% 38%	2134
	21st to end	Day	25% 9% 3 5% 6% 3 4 5% 5% 6% 31%	2224
May	1st to 10th	Day	20% 7% 3 6% 5% 3 4 4 5% 6% 35%	2520
	11th to 20th	Day	16% 6% 3 5% 5% 3 5% 5% 6% 7% 40%	2478
	21st to end	Day	16% 6% 3 5% 5% 4 5% 5% 6% 8% 37%	2725
June	1st to 10th	Day	21% 6% 3 6% 6% 3 5% 6% 6% 7% 33%	2520
	11th to 20th	Day	18% 6% 2 5% 5% 3 5% 4 6% 8% 38%	2520
	21st to end	Day	18% 7% 3 5% 5% 3 4 5% 5% 8% 35%	2520
July	1st to 10th	Day	12% 5% 3 5% 4 3 4 5% 7% 9% 44%	2520
	11th to 20th	Day	14% 6% 2 5% 5% 3 5% 5% 6% 10% 39%	2520
	21st to end	Day	13% 4 3 5% 5% 3 6% 6% 6% 9% 40%	2744
August	1st to 10th	Day	12% 6% 3 5% 5% 3 5% 6% 5% 8% 41%	2431
	11th to 20th	Day	13% 6% 2 5% 4 3 5% 7% 7% 9% 39%	2254
	21st to end	Day	14% 7% 2 5% 5% 3 5% 4 7% 9% 39%	2376
September	1st to 10th	Day	15% 6% 2 6% 4 3 4 5% 5% 8% 43%	2160
	11th to 20th	Day	14% 5% 3 4 5% 2 4 4 4 7% 46%	2160
	21st to end	Day	20% 6% 2 5% 5% 3 4 5% 5% 7% 38%	1926
October	1st to 10th	Day	22% 9% 4 6% 5% 3 4 4 5% 6% 33%	1800
	11th to 20th	Day	22% 12% 3 6% 6% 3 4 5% 4 7% 27%	1800
	21st to end	Day	28% 11% 3 6% 6% 3 4 4 5% 6% 25%	1854
November	1st to 10th	Day	17% 9% 4 6% 7% 4 4 4 6% 7% 31%	1671
	11th to 20th	Day	17% 12% 5% 9% 6% 4 5% 4 5% 5% 28%	1568
	21st to end	Day	20% 16% 5% 10% 7% 4 5% 5% 4 5% 20%	1520
December	1st to 10th	Day	25% 19% 5% 9% 6% 3 5% 4 3 6% 14%	1520
	11th to 20th	Day	21% 17% 6% 10% 6% 4 4 4 4 4 19%	1906
	21st to end	Day	28% 17% 5% 9% 7% 4 4 4 3 3 17%	2772
January	1st to 10th	Night	20% 20% 7% 10% 7% 3 5% 4 4 4 17%	2649
	11th to 20th	Night	19% 18% 6% 11% 7% 4 6% 4 4 4 18%	2660
	21st to end	Night	15% 16% 7% 10% 6% 4 5% 4 4 5% 24%	2806
February	1st to 10th	Night	19% 16% 6% 12% 8% 4 5% 4 4 4 18%	2340
	11th to 20th	Night	15% 13% 7% 11% 7% 4 5% 5% 4 6% 25%	2248
	21st to end	Night	19% 13% 6% 9% 7% 2 5% 4 4 6% 25%	1776
March	1st to 10th	Night	18% 15% 6% 8% 7% 3 4 3 4 4 28%	2145
	11th to 20th	Night	20% 13% 5% 7% 6% 3 3 3 4 5% 31%	1979
	21st to end	Night	20% 11% 4 7% 6% 3 3 2 3 5% 36%	2063
April	1st to 10th	Night	22% 10% 4 7% 5% 2 4 4 4 6% 34%	1800
	11th to 20th	Night	23% 6% 4 6% 5% 4 3 4 5% 6% 34%	1775
	21st to end	Night	23% 9% 4 6% 5% 3 5% 4 4 6% 33%	1752
May	1st to 10th	Night	24% 7% 2 5% 4 3 4 5% 5% 8% 33%	1440
	11th to 20th	Night	13% 6% 3 6% 5% 4 6% 5% 4 7% 42%	1415
	21st to end	Night	13% 6% 3 5% 6% 2 5% 5% 5% 8% 43%	1550
June	1st to 10th	Night	19% 6% 2 6% 5% 3 5% 6% 6% 9% 32%	1440
	11th to 20th	Night	16% 6% 2 4 5% 3 5% 5% 7% 8% 40%	1440
	21st to end	Night	17% 6% 2 5% 5% 3 5% 5% 6% 8% 36%	1440
July	1st to 10th	Night	11% 5% 3 4 4 3 5% 5% 5% 8% 47%	1440
	11th to 20th	Night	12% 6% 2 4 5% 3 5% 5% 6% 10% 42%	1440
	21st to end	Night	12% 6% 2 5% 4 3 5% 5% 6% 9% 42%	1574
August	1st to 10th	Night	12% 5% 3 4 5% 3 5% 5% 8% 8% 42%	1503
	11th to 20th	Night	14% 7% 3 7% 4 3 4 4 7% 8% 40%	1629
	21st to end	Night	12% 5% 2 5% 6% 2 4 5% 6% 9% 42%	1980
September	1st to 10th	Night	15% 6% 2 5% 6% 2 3 4 5% 7% 44%	1800
	11th to 20th	Night	15% 5% 3 4 4 3 4 3 5% 7% 48%	1800
	21st to end	Night	17% 5% 2 6% 5% 3 4 3 6% 7% 41%	2031
October	1st to 10th	Night	22% 8% 3 6% 6% 3 4 4 4 7% 32%	2160
	11th to 20th	Night	20% 8% 4 7% 6% 3 5% 5% 5% 6% 31%	2160
	21st to end	Night	28% 10% 4 6% 7% 3 3 4 4 5% 25%	2502
November	1st to 10th	Night	20% 9% 3 7% 5% 2 4 4 5% 7% 34%	2407
	11th to 20th	Night	18% 12% 3 7% 6% 3 5% 5% 5% 5% 30%	2608
	21st to end	Night	23% 15% 4 7% 5% 4 4 5% 5% 6% 22%	2660
December	1st to 10th	Night	23% 19% 6% 10% 7% 4 5% 4 4 4 15%	2660
	11th to 20th	Night	23% 16% 5% 8% 7% 3 4 3 3 4 24%	3288
	21st to end	Night	31% 15% 5% 10% 6% 3 4 3 3 4 15%	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	72% 5% 8% 11% 3	1518
	11th to 20th	Day	71% 4 7% 11% 8% 1	1520
	21st to end	Day	69% 5% 8% 11% 6% 1	1773
February	1st to 10th	Day	69% 5% 7% 13% 4 1	1620
	11th to 20th	Day	65% 4 9% 14% 8% 1	1606
	21st to end	Day	68% 4 7% 12% 7% 1	1480
March	1st to 10th	Day	63% 4 9% 15% 8% 1	1803
	11th to 20th	Day	60% 5% 10% 12% 11% 2	1980
	21st to end	Day	54% 3 7% 17% 13% 5%	2292
April	1st to 10th	Day	55% 4 7% 19% 13% 2	2160
	11th to 20th	Day	49% 5% 7% 21% 15% 3	2134
	21st to end	Day	54% 6% 7% 16% 13% 3	2224
May	1st to 10th	Day	51% 5% 8% 20% 14% 2	2520
	11th to 20th	Day	42% 6% 9% 25% 15% 2	2482
	21st to end	Day	44% 7% 15% 21% 12% 2	2725
June	1st to 10th	Day	51% 7% 11% 19% 11% 1	2520
	11th to 20th	Day	45% 6% 11% 25% 12% 2	2520
	21st to end	Day	48% 7% 12% 21% 11% 1	2520
July	1st to 10th	Day	37% 6% 12% 29% 16% 1	2450
	11th to 20th	Day	40% 7% 16% 27% 9%	2445
	21st to end	Day	40% 8% 16% 24% 12%	2591
August	1st to 10th	Day	41% 7% 15% 27% 10%	2417
	11th to 20th	Day	40% 9% 16% 25% 10%	2254
	21st to end	Day	42% 7% 12% 28% 11% 1	2376
September	1st to 10th	Day	41% 5% 14% 27% 12% 1	2160
	11th to 20th	Day	39% 6% 10% 29% 16% 1	2160
	21st to end	Day	46% 6% 12% 26% 10%	1926
October	1st to 10th	Day	54% 5% 10% 20% 11% 1	1800
	11th to 20th	Day	56% 6% 14% 18% 5% 1	1800
	21st to end	Day	62% 4 10% 15% 8% 1	1854
November	1st to 10th	Day	52% 8% 13% 20% 7% 1	1671
	11th to 20th	Day	59% 6% 11% 15% 7% 2	1568
	21st to end	Day	68% 6% 11% 9% 6%	1520
December	1st to 10th	Day	73% 7% 9% 9% 2	1520
	11th to 20th	Day	70% 6% 11% 10% 2	1906
	21st to end	Day	74% 5% 7% 12% 2	2772
January	1st to 10th	Night	72% 4 8% 11% 4	2649
	11th to 20th	Night	72% 5% 8% 9% 5%	2660
	21st to end	Night	65% 5% 8% 14% 7% 1	2806
February	1st to 10th	Night	71% 4 8% 10% 5%	2340
	11th to 20th	Night	63% 4 8% 17% 7%	2250
	21st to end	Night	62% 5% 9% 15% 8% 1	1776
March	1st to 10th	Night	61% 4 10% 16% 8% 1	2155
	11th to 20th	Night	59% 3 9% 18% 10% 1	1980
	21st to end	Night	55% 4 5% 19% 15% 3	2063
April	1st to 10th	Night	54% 3 9% 20% 13% 2	1800
	11th to 20th	Night	51% 5% 10% 17% 16% 1	1775
	21st to end	Night	53% 6% 9% 16% 13% 3	1752
May	1st to 10th	Night	52% 4 8% 17% 15% 4	1440
	11th to 20th	Night	43% 7% 8% 23% 16% 3	1416
	21st to end	Night	42% 6% 14% 20% 16% 2	1551
June	1st to 10th	Night	46% 7% 14% 22% 10% 1	1440
	11th to 20th	Night	42% 5% 13% 21% 16% 2	1440
	21st to end	Night	45% 8% 12% 22% 12% 1	1440
July	1st to 10th	Night	35% 8% 12% 26% 17% 2	1400
	11th to 20th	Night	37% 7% 13% 30% 13% 1	1392
	21st to end	Night	38% 7% 15% 27% 12% 1	1486
August	1st to 10th	Night	38% 7% 18% 25% 11% 1	1493
	11th to 20th	Night	42% 6% 12% 24% 14% 1	1629
	21st to end	Night	37% 7% 14% 31% 11%	1980
September	1st to 10th	Night	39% 7% 13% 28% 12% 1	1800
	11th to 20th	Night	36% 5% 13% 30% 15% 1	1800
	21st to end	Night	43% 5% 12% 28% 12% 1	2031
October	1st to 10th	Night	53% 5% 10% 20% 11% 1	2160
	11th to 20th	Night	54% 6% 13% 19% 7% 1	2160
	21st to end	Night	62% 6% 11% 12% 8% 1	2502
November	1st to 10th	Night	51% 5% 15% 18% 10% 2	2407
	11th to 20th	Night	55% 6% 11% 18% 8% 2	2608
	21st to end	Night	63% 6% 12% 15% 4	2660
December	1st to 10th	Night	74% 6% 8% 10% 2	2660
	11th to 20th	Night	66% 5% 9% 15% 5% 1	3288
	21st to end	Night	74% 5% 9% 11% 2	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	32% 19% 33% 11% 5% 1	180
	11th to 20th	Day	32% 22% 28% 15% 2 1	180
	21st to end	Day	29% 20% 31% 17% 3	247
February	1st to 10th	Day	34% 32% 29% 5% 1	240
	11th to 20th	Day	32% 31% 31% 6%	264
	21st to end	Day	39% 22% 26% 12% 1	346
March	1st to 10th	Day	28% 20% 30% 17% 5%	420
	11th to 20th	Day	30% 22% 30% 14% 4 1	420
	21st to end	Day	35% 20% 27% 11% 5% 1	462
April	1st to 10th	Day	31% 22% 29% 13% 5%	420
	11th to 20th	Day	33% 19% 22% 16% 7% 3	412
	21st to end	Day	35% 20% 25% 13% 6% 2	420
May	1st to 10th	Day	27% 19% 28% 16% 8% 3	423
	11th to 20th	Day	21% 15% 36% 19% 7% 2	447
	21st to end	Day	19% 16% 31% 22% 10% 2	485
June	1st to 10th	Day	26% 14% 31% 20% 6% 2	450
	11th to 20th	Day	19% 16% 33% 20% 10% 2	450
	21st to end	Day	23% 14% 34% 19% 8% 2	450
July	1st to 10th	Day	14% 10% 31% 27% 15% 3	445
	11th to 20th	Day	18% 10% 31% 26% 13% 3	444
	21st to end	Day	15% 10% 37% 27% 10% 1	488
August	1st to 10th	Day	15% 8% 31% 28% 15% 4	446
	11th to 20th	Day	15% 8% 27% 27% 15% 7%	439
	21st to end	Day	16% 11% 29% 24% 14% 6%	495
September	1st to 10th	Day	19% 11% 29% 22% 12% 8%	450
	11th to 20th	Day	14% 10% 30% 20% 17% 9%	450
	21st to end	Day	20% 11% 26% 25% 13% 5%	450
October	1st to 10th	Day	29% 14% 22% 18% 11% 5%	450
	11th to 20th	Day	26% 22% 29% 15% 6% 2	450
	21st to end	Day	36% 16% 26% 18% 5%	432
November	1st to 10th	Day	27% 20% 27% 17% 8% 1	365
	11th to 20th	Day	29% 18% 32% 12% 6% 2	228
	21st to end	Day	28% 21% 34% 13% 3	180
December	1st to 10th	Day	39% 18% 24% 15% 3 1	180
	11th to 20th	Day	29% 26% 33% 11% 1	180
	21st to end	Day	35% 21% 28% 14% 2 1	198
January	1st to 10th	Night	33% 19% 28% 17% 4	760
	11th to 20th	Night	30% 20% 28% 18% 4 1	760
	21st to end	Night	24% 19% 28% 23% 6%	835
February	1st to 10th	Night	28% 23% 30% 17% 2	720
	11th to 20th	Night	25% 19% 35% 17% 3 1	703
	21st to end	Night	28% 17% 33% 18% 3	592
March	1st to 10th	Night	29% 18% 29% 21% 4	720
	11th to 20th	Night	32% 18% 28% 17% 5% 1	720
	21st to end	Night	28% 15% 30% 20% 7% 1	792
April	1st to 10th	Night	29% 15% 31% 22% 3	720
	11th to 20th	Night	28% 17% 28% 21% 6%	711
	21st to end	Night	28% 13% 30% 21% 9%	672
May	1st to 10th	Night	29% 9% 24% 28% 9% 1	360
	11th to 20th	Night	16% 11% 35% 32% 6%	354
	21st to end	Night	16% 10% 31% 33% 9% 1	389
June	1st to 10th	Night	22% 8% 25% 35% 9% 1	360
	11th to 20th	Night	16% 9% 29% 32% 13% 1	360
	21st to end	Night	19% 7% 30% 33% 12%	360
July	1st to 10th	Night	12% 5% 31% 38% 14% 1	350
	11th to 20th	Night	13% 5% 27% 34% 20% 1	348
	21st to end	Night	14% 5% 30% 38% 11% 1	394
August	1st to 10th	Night	15% 3 25% 39% 18%	429
	11th to 20th	Night	18% 4 18% 36% 21% 2	565
	21st to end	Night	14% 5% 29% 35% 16% 2	792
September	1st to 10th	Night	18% 7% 25% 33% 16% 2	720
	11th to 20th	Night	17% 6% 22% 31% 21% 4	720
	21st to end	Night	18% 11% 25% 27% 18% 2	720
October	1st to 10th	Night	28% 12% 27% 18% 15% 1	720
	11th to 20th	Night	26% 13% 27% 24% 8% 1	720
	21st to end	Night	35% 11% 28% 22% 3	792
November	1st to 10th	Night	28% 13% 28% 22% 8% 1	740
	11th to 20th	Night	27% 17% 29% 18% 8% 1	760
	21st to end	Night	36% 15% 27% 17% 6%	760
December	1st to 10th	Night	36% 17% 26% 17% 4	760
	11th to 20th	Night	32% 19% 30% 15% 3 1	760
	21st to end	Night	36% 16% 29% 17% 2	836

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