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 2025-02-21.

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% 4 4 4 5% 7% 31%	108723
	Night	18% 13% 4 9% 5% 4 4 3 4 6% 28%	109851
Transparency	Day	53% 6% 11% 20% 9% 1	112262
	Night	57% 6% 10% 18% 9% 1	114476
Seeing	Day	25% 17% 29% 18% 8% 2	14823
	Night	26% 14% 28% 24% 8% 1	24109

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	15% 19% 7% 15% 5% 3 4 3 4 5% 19%	3597
	11th to 20th	Day	13% 18% 9% 20% 6% 4 4 3 4 4 14%	3570
	21st to end	Day	14% 18% 8% 14% 8% 8% 5% 3 4 4 15%	4232
February	1st to 10th	Day	17% 19% 5% 11% 7% 5% 4 4 5% 5% 19%	1800
	11th to 20th	Day	16% 15% 6% 10% 7% 5% 4 3 4 4 24%	1780
	21st to end	Day	20% 16% 4 11% 7% 5% 4 3 4 5% 21%	1570
March	1st to 10th	Day	23% 14% 5% 9% 4 4 3 3 4 5% 27%	3133
	11th to 20th	Day	13% 19% 4 9% 5% 5% 4 2 4 5% 28%	3480
	21st to end	Day	16% 9% 3 10% 5% 4 3 3 4 6% 36%	4026
April	1st to 10th	Day	21% 13% 4 6% 4 4 4 3 3 5% 33%	2280
	11th to 20th	Day	22% 9% 2 5% 4 4 4 3 4 6% 37%	2254
	21st to end	Day	24% 9% 2 6% 5% 4 4 4 5% 6% 31%	2349
May	1st to 10th	Day	22% 10% 3 8% 5% 4 4 3 5% 6% 31%	4426
	11th to 20th	Day	16% 9% 4 8% 5% 4 5% 4 6% 7% 32%	4398
	21st to end	Day	15% 6% 2 6% 4 5% 5% 4 7% 8% 39%	4837
June	1st to 10th	Day	20% 7% 3 7% 5% 4 5% 4 6% 7% 32%	2660
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 4 6% 8% 37%	2660
	21st to end	Day	19% 7% 2 6% 5% 4 4 4 6% 8% 34%	2660
July	1st to 10th	Day	12% 5% 2 6% 4 4 4 5% 7% 10% 40%	4440
	11th to 20th	Day	13% 6% 2 6% 4 4 4 5% 6% 9% 41%	4440
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	4814
August	1st to 10th	Day	16% 7% 3 7% 4 4 4 4 5% 8% 37%	4278
	11th to 20th	Day	17% 6% 3 6% 3 4 5% 5% 7% 9% 35%	3953
	21st to end	Day	16% 6% 2 5% 4 4 4 4 6% 9% 40%	4180
September	1st to 10th	Day	15% 6% 2 6% 3 4 4 4 5% 8% 43%	2280
	11th to 20th	Day	13% 5% 2 5% 4 3 4 3 5% 7% 47%	2279
	21st to end	Day	19% 7% 2 6% 4 4 5% 4 5% 7% 38%	2033
October	1st to 10th	Day	22% 9% 3 7% 3 4 3 3 5% 6% 33%	1900
	11th to 20th	Day	21% 12% 3 8% 5% 4 4 4 4 6% 29%	1900
	21st to end	Day	27% 11% 3 7% 5% 4 4 3 5% 6% 26%	1957
November	1st to 10th	Day	17% 11% 3 7% 6% 5% 4 4 6% 7% 31%	1761
	11th to 20th	Day	16% 13% 4 9% 5% 6% 5% 3 5% 5% 29%	1650
	21st to end	Day	20% 18% 4 11% 5% 5% 5% 3 5% 5% 19%	1600
December	1st to 10th	Day	21% 22% 5% 12% 5% 5% 4 3 4 5% 14%	2600
	11th to 20th	Day	20% 19% 7% 12% 6% 4 3 3 4 4 19%	2986
	21st to end	Day	23% 17% 4 10% 5% 4 4 3 5% 4 20%	3960
January	1st to 10th	Night	15% 22% 6% 14% 6% 4 4 3 3 3 19%	6349
	11th to 20th	Night	12% 21% 9% 18% 8% 6% 5% 3 4 3 12%	6315
	21st to end	Night	16% 19% 8% 14% 7% 6% 4 3 3 4 15%	6720
February	1st to 10th	Night	19% 18% 5% 12% 7% 5% 4 3 4 4 19%	2600
	11th to 20th	Night	14% 14% 6% 12% 6% 5% 4 4 4 6% 25%	2505
	21st to end	Night	19% 14% 5% 10% 6% 4 4 3 4 6% 25%	1885
March	1st to 10th	Night	21% 12% 4 8% 5% 4 3 3 3 5% 31%	3705
	11th to 20th	Night	21% 18% 4 9% 5% 4 3 3 4 5% 25%	3479
	21st to end	Night	18% 12% 3 9% 5% 4 3 2 3 5% 36%	3605
April	1st to 10th	Night	22% 11% 3 8% 4 3 3 3 4 6% 33%	1900
	11th to 20th	Night	23% 7% 3 6% 4 4 3 4 5% 6% 34%	1875
	21st to end	Night	23% 9% 4 6% 4 4 4 3 3 6% 33%	1848
May	1st to 10th	Night	25% 10% 3 8% 4 4 4 4 5% 7% 28%	2514
	11th to 20th	Night	20% 10% 3 7% 5% 4 4 3 3 6% 34%	2495
	21st to end	Night	15% 8% 2 6% 4 3 4 3 5% 8% 41%	2738
June	1st to 10th	Night	18% 7% 2 7% 4 4 6% 4 7% 8% 32%	1520
	11th to 20th	Night	15% 6% 2 5% 4 4 4 4 7% 8% 40%	1520
	21st to end	Night	18% 7% 2 6% 5% 4 5% 4 6% 7% 35%	1520
July	1st to 10th	Night	15% 7% 3 6% 5% 5% 4 4 6% 7% 39%	2520
	11th to 20th	Night	14% 7% 2 6% 4 3 4 4 6% 9% 42%	2520
	21st to end	Night	12% 7% 2 6% 4 5% 5% 4 6% 8% 42%	2739
August	1st to 10th	Night	14% 8% 3 6% 4 5% 4 4 6% 7% 39%	2647
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 6% 8% 37%	2844
	21st to end	Night	10% 5% 2 7% 5% 4 5% 4 7% 9% 40%	3476
September	1st to 10th	Night	15% 6% 2 7% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	14% 5% 2 5% 4 3 4 2 5% 7% 48%	1900
	21st to end	Night	17% 6% 2 7% 5% 4 3 3 7% 7% 40%	2144
October	1st to 10th	Night	21% 9% 3 7% 6% 4 4 3 4 7% 33%	2280
	11th to 20th	Night	20% 9% 3 7% 5% 4 5% 3 5% 6% 32%	2280
	21st to end	Night	26% 10% 3 8% 6% 4 4 3 4 5% 26%	2641
November	1st to 10th	Night	19% 10% 3 8% 4 4 4 3 5% 7% 34%	2537
	11th to 20th	Night	18% 12% 3 8% 5% 4 5% 4 5% 5% 30%	2746
	21st to end	Night	23% 16% 4 8% 4 5% 4 4 5% 6% 21%	2800
December	1st to 10th	Night	20% 22% 6% 13% 6% 6% 5% 3 4 4 12%	4580
	11th to 20th	Night	23% 17% 5% 9% 5% 3 4 2 3 4 24%	5208
	21st to end	Night	26% 15% 5% 11% 5% 4 4 3 4 5% 18%	6996

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	68% 6% 9% 13% 4 1	3598
	11th to 20th	Day	75% 6% 6% 7% 5% 1	3600
	21st to end	Day	74% 5% 8% 7% 6% 1	4232
February	1st to 10th	Day	68% 5% 8% 14% 5% 1	1800
	11th to 20th	Day	65% 4 9% 14% 7% 1	1789
	21st to end	Day	67% 4 8% 12% 8% 1	1570
March	1st to 10th	Day	61% 4 8% 17% 9% 1	3136
	11th to 20th	Day	59% 6% 12% 13% 9% 1	3480
	21st to end	Day	49% 5% 8% 22% 13% 3	4026
April	1st to 10th	Day	55% 4 7% 18% 13% 2	2280
	11th to 20th	Day	50% 5% 7% 21% 15% 2	2254
	21st to end	Day	54% 6% 7% 17% 13% 3	2349
May	1st to 10th	Day	54% 5% 9% 21% 9% 1	4440
	11th to 20th	Day	49% 8% 10% 22% 9% 1	4402
	21st to end	Day	42% 7% 12% 26% 12% 1	4837
June	1st to 10th	Day	52% 7% 10% 19% 11% 1	2660
	11th to 20th	Day	45% 6% 11% 25% 12% 2	2660
	21st to end	Day	48% 7% 12% 21% 11% 1	2660
July	1st to 10th	Day	38% 6% 13% 29% 13% 1	4370
	11th to 20th	Day	38% 8% 15% 30% 8%	4365
	21st to end	Day	38% 8% 15% 29% 10%	4661
August	1st to 10th	Day	46% 6% 14% 23% 10%	4264
	11th to 20th	Day	43% 9% 15% 25% 8%	3992
	21st to end	Day	41% 6% 14% 29% 10%	4180
September	1st to 10th	Day	40% 6% 14% 28% 12% 1	2280
	11th to 20th	Day	37% 5% 11% 29% 16% 1	2279
	21st to end	Day	46% 6% 12% 25% 11%	2033
October	1st to 10th	Day	47% 7% 11% 26% 9%	3160
	11th to 20th	Day	48% 5% 15% 24% 8%	3140
	21st to end	Day	48% 5% 16% 24% 6%	3208
November	1st to 10th	Day	52% 7% 13% 20% 7% 1	1761
	11th to 20th	Day	58% 6% 11% 15% 8% 2	1650
	21st to end	Day	68% 6% 11% 9% 6%	1600
December	1st to 10th	Day	73% 7% 12% 7% 1	2600
	11th to 20th	Day	70% 5% 8% 11% 5%	2986
	21st to end	Day	68% 5% 9% 14% 4	3960
January	1st to 10th	Night	71% 5% 10% 10% 4	6349
	11th to 20th	Night	77% 6% 6% 8% 3	6360
	21st to end	Night	75% 5% 6% 7% 6% 1	6720
February	1st to 10th	Night	70% 5% 8% 12% 5%	2600
	11th to 20th	Night	63% 4 9% 17% 7%	2507
	21st to end	Night	61% 5% 10% 16% 7% 1	1885
March	1st to 10th	Night	56% 5% 9% 22% 9%	3715
	11th to 20th	Night	63% 4 11% 14% 8% 1	3480
	21st to end	Night	53% 4 4 22% 14% 2	3605
April	1st to 10th	Night	54% 4 9% 19% 13% 1	1900
	11th to 20th	Night	52% 6% 9% 17% 15% 1	1875
	21st to end	Night	53% 6% 9% 17% 13% 3	1848
May	1st to 10th	Night	56% 6% 9% 17% 9% 2	2520
	11th to 20th	Night	51% 8% 11% 19% 9% 2	2496
	21st to end	Night	42% 6% 11% 21% 19% 2	2739
June	1st to 10th	Night	46% 7% 13% 22% 10% 1	1520
	11th to 20th	Night	41% 6% 13% 21% 16% 2	1520
	21st to end	Night	47% 7% 12% 21% 13% 1	1520
July	1st to 10th	Night	43% 6% 11% 23% 15% 1	2480
	11th to 20th	Night	39% 6% 14% 33% 8%	2472
	21st to end	Night	39% 8% 14% 27% 12% 1	2651
August	1st to 10th	Night	43% 7% 15% 23% 11%	2637
	11th to 20th	Night	44% 7% 14% 26% 9%	2871
	21st to end	Night	36% 8% 14% 31% 10% 1	3476
September	1st to 10th	Night	39% 7% 13% 28% 12% 1	1900
	11th to 20th	Night	35% 5% 13% 31% 16% 1	1900
	21st to end	Night	43% 5% 12% 27% 12% 1	2144
October	1st to 10th	Night	46% 6% 11% 26% 10% 1	3800
	11th to 20th	Night	46% 5% 14% 24% 10%	3779
	21st to end	Night	53% 6% 13% 21% 6%	4340
November	1st to 10th	Night	51% 5% 14% 19% 10% 1	2537
	11th to 20th	Night	54% 6% 11% 18% 9% 2	2746
	21st to end	Night	63% 6% 11% 15% 4	2800
December	1st to 10th	Night	77% 6% 8% 8% 1	4580
	11th to 20th	Night	66% 5% 8% 15% 6%	5208
	21st to end	Night	70% 5% 7% 11% 7%	6996

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	30% 21% 35% 10% 5% 1	200
	11th to 20th	Day	31% 22% 30% 15% 2 1	200
	21st to end	Day	28% 24% 29% 15% 3	278
February	1st to 10th	Day	33% 30% 28% 8% 1	300
	11th to 20th	Day	32% 31% 29% 7%	327
	21st to end	Day	38% 23% 27% 11% 1	382
March	1st to 10th	Day	29% 20% 28% 17% 5% 1	460
	11th to 20th	Day	32% 21% 30% 13% 3 1	460
	21st to end	Day	34% 21% 27% 11% 5% 1	506
April	1st to 10th	Day	32% 22% 28% 13% 5%	460
	11th to 20th	Day	34% 20% 22% 15% 6% 3	452
	21st to end	Day	34% 20% 25% 13% 7% 2	460
May	1st to 10th	Day	27% 20% 27% 16% 8% 2	463
	11th to 20th	Day	19% 15% 35% 20% 8% 2	487
	21st to end	Day	19% 17% 30% 23% 10% 2	529
June	1st to 10th	Day	26% 15% 30% 20% 7% 2	490
	11th to 20th	Day	18% 16% 33% 21% 10% 2	490
	21st to end	Day	24% 15% 33% 18% 8% 2	490
July	1st to 10th	Day	14% 11% 32% 27% 15% 2	485
	11th to 20th	Day	17% 11% 31% 25% 12% 3	484
	21st to end	Day	14% 10% 37% 27% 11% 1	532
August	1st to 10th	Day	16% 9% 31% 27% 14% 4	486
	11th to 20th	Day	16% 9% 26% 27% 15% 6%	479
	21st to end	Day	17% 11% 29% 24% 13% 6%	539
September	1st to 10th	Day	19% 11% 29% 22% 11% 7%	490
	11th to 20th	Day	13% 9% 27% 20% 20% 11%	490
	21st to end	Day	19% 12% 25% 26% 13% 4	490
October	1st to 10th	Day	28% 15% 23% 18% 11% 5%	490
	11th to 20th	Day	26% 23% 28% 15% 7% 1	490
	21st to end	Day	34% 16% 27% 18% 5%	469
November	1st to 10th	Day	28% 20% 28% 16% 8% 1	395
	11th to 20th	Day	28% 20% 32% 12% 6% 2	250
	21st to end	Day	32% 21% 32% 13% 3	200
December	1st to 10th	Day	39% 18% 26% 15% 3 1	200
	11th to 20th	Day	32% 25% 32% 10% 2	200
	21st to end	Day	34% 19% 28% 16% 3	220
January	1st to 10th	Night	32% 19% 29% 16% 4	800
	11th to 20th	Night	29% 20% 28% 18% 4 1	800
	21st to end	Night	24% 20% 28% 23% 5%	880
February	1st to 10th	Night	29% 22% 29% 18% 2	800
	11th to 20th	Night	26% 20% 35% 16% 2 1	783
	21st to end	Night	28% 17% 33% 19% 3	629
March	1st to 10th	Night	29% 17% 29% 21% 4	760
	11th to 20th	Night	32% 18% 28% 17% 5% 1	760
	21st to end	Night	28% 16% 30% 20% 6% 1	836
April	1st to 10th	Night	29% 15% 30% 22% 3	760
	11th to 20th	Night	28% 18% 28% 20% 6%	751
	21st to end	Night	28% 13% 30% 21% 8%	708
May	1st to 10th	Night	29% 9% 25% 28% 8% 1	380
	11th to 20th	Night	16% 11% 35% 32% 6%	374
	21st to end	Night	16% 10% 31% 33% 9%	411
June	1st to 10th	Night	21% 9% 26% 35% 9% 1	380
	11th to 20th	Night	16% 9% 27% 34% 13% 1	380
	21st to end	Night	21% 7% 29% 33% 11%	380
July	1st to 10th	Night	13% 5% 30% 38% 13% 1	370
	11th to 20th	Night	13% 5% 27% 35% 18% 1	368
	21st to end	Night	15% 5% 29% 39% 11% 1	416
August	1st to 10th	Night	15% 3 25% 38% 18%	454
	11th to 20th	Night	19% 5% 18% 35% 20% 3	597
	21st to end	Night	14% 5% 28% 35% 17% 1	836
September	1st to 10th	Night	18% 7% 25% 33% 16% 2	760
	11th to 20th	Night	16% 5% 21% 31% 22% 5%	760
	21st to end	Night	18% 11% 25% 27% 18% 2	760
October	1st to 10th	Night	27% 12% 26% 19% 15% 1	760
	11th to 20th	Night	27% 13% 26% 25% 9% 1	760
	21st to end	Night	34% 12% 28% 22% 4	836
November	1st to 10th	Night	28% 14% 28% 22% 8% 1	780
	11th to 20th	Night	27% 16% 29% 19% 8% 1	800
	21st to end	Night	36% 16% 27% 16% 6%	800
December	1st to 10th	Night	36% 16% 26% 17% 4	800
	11th to 20th	Night	32% 19% 30% 15% 3 1	800
	21st to end	Night	36% 15% 29% 17% 2	880

Page generated at 2025-02-18 03:26:28. Version ac07

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