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 2026-06-16.

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	18% 11% 4 9% 5% 4 4 4 5% 6% 31%	138111
	Night	18% 13% 4 10% 5% 4 4 3 5% 6% 28%	133894
Transparency	Day	53% 6% 11% 20% 9% 1	141604
	Night	57% 6% 10% 18% 9% 1	138490
Seeing	Day	26% 17% 29% 18% 8% 2	16552
	Night	26% 14% 28% 23% 8% 1	25722

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% 16% 6% 4 4 3 4 5% 17%	4661
	11th to 20th	Day	12% 21% 8% 20% 7% 4 4 3 3 4 13%	4650
	21st to end	Day	12% 17% 8% 14% 9% 8% 6% 3 4 4 15%	5478
February	1st to 10th	Day	17% 19% 5% 12% 7% 5% 4 4 5% 5% 19%	1890
	11th to 20th	Day	16% 15% 6% 11% 7% 5% 4 4 4 4 23%	1872
	21st to end	Day	19% 17% 5% 12% 6% 5% 4 3 4 4 20%	1730
March	1st to 10th	Day	20% 15% 5% 10% 4 3 4 3 4 5% 27%	4593
	11th to 20th	Day	12% 16% 4 9% 5% 5% 5% 3 6% 6% 29%	5090
	21st to end	Day	21% 10% 3 9% 5% 4 3 3 3 5% 33%	5901
April	1st to 10th	Day	21% 14% 4 6% 4 4 4 2 3 5% 32%	2520
	11th to 20th	Day	22% 10% 2 6% 4 4 3 3 4 6% 35%	2494
	21st to end	Day	24% 9% 2 6% 5% 4 4 4 5% 6% 31%	2596
May	1st to 10th	Day	25% 10% 3 8% 5% 4 3 3 5% 6% 29%	8237
	11th to 20th	Day	18% 9% 3 8% 5% 4 4 3 6% 6% 34%	8221
	21st to end	Day	21% 9% 3 6% 4 4 5% 4 6% 6% 32%	9060
June	1st to 10th	Day	19% 7% 3 6% 5% 4 5% 4 6% 7% 33%	2940
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 4 6% 8% 37%	2870
	21st to end	Day	19% 7% 2 6% 5% 4 4 4 6% 8% 35%	2800
July	1st to 10th	Day	13% 6% 2 6% 4 4 5% 5% 7% 9% 39%	6360
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 5% 6% 9% 42%	6360
	21st to end	Day	12% 4 2 5% 4 4 5% 4 6% 9% 45%	6926
August	1st to 10th	Day	16% 7% 3 7% 4 4 4 4 5% 8% 38%	4414
	11th to 20th	Day	17% 6% 3 6% 3 4 5% 5% 6% 9% 36%	4080
	21st to end	Day	16% 7% 2 5% 4 4 4 4 6% 9% 40%	4312
September	1st to 10th	Day	15% 6% 2 6% 3 4 4 4 5% 8% 44%	2400
	11th to 20th	Day	13% 5% 2 5% 5% 3 4 3 4 7% 48%	2399
	21st to end	Day	20% 7% 2 6% 4 4 5% 4 5% 7% 37%	2140
October	1st to 10th	Day	21% 9% 3 7% 3 4 3 3 5% 6% 36%	2000
	11th to 20th	Day	20% 11% 3 8% 4 4 4 4 5% 7% 29%	2000
	21st to end	Day	26% 11% 3 7% 4 4 4 3 5% 6% 26%	2060
November	1st to 10th	Day	17% 11% 4 7% 6% 5% 4 4 6% 7% 30%	1851
	11th to 20th	Day	16% 14% 4 10% 5% 5% 5% 3 5% 5% 29%	1732
	21st to end	Day	20% 18% 4 11% 5% 5% 5% 3 5% 5% 20%	1680
December	1st to 10th	Day	21% 22% 5% 12% 5% 5% 4 3 4 5% 14%	2680
	11th to 20th	Day	19% 18% 7% 12% 6% 4 3 3 4 4 19%	3066
	21st to end	Day	22% 17% 4 11% 5% 4 4 3 4 4 20%	4048
January	1st to 10th	Night	15% 22% 7% 14% 6% 4 4 3 3 4 18%	8234
	11th to 20th	Night	14% 21% 9% 18% 8% 6% 4 3 3 3 11%	8235
	21st to end	Night	14% 16% 7% 14% 7% 7% 5% 4 4 4 17%	8699
February	1st to 10th	Night	18% 17% 5% 13% 7% 5% 4 3 4 5% 20%	2730
	11th to 20th	Night	15% 14% 6% 12% 6% 5% 4 4 4 5% 25%	2633
	21st to end	Night	18% 15% 6% 10% 6% 4 4 3 4 6% 24%	2076
March	1st to 10th	Night	21% 13% 4 10% 5% 5% 3 3 4 4 28%	5451
	11th to 20th	Night	17% 14% 3 8% 4 4 4 3 5% 7% 30%	5089
	21st to end	Night	22% 14% 4 10% 5% 4 3 2 3 5% 29%	5272
April	1st to 10th	Night	22% 11% 3 8% 4 3 3 3 4 6% 32%	2100
	11th to 20th	Night	23% 9% 3 6% 4 4 3 3 4 6% 34%	2075
	21st to end	Night	23% 9% 4 6% 4 4 4 3 3 5% 34%	2042
May	1st to 10th	Night	27% 10% 3 8% 5% 4 4 4 5% 7% 23%	4660
	11th to 20th	Night	19% 10% 3 7% 4 4 4 3 4 8% 32%	4639
	21st to end	Night	20% 9% 2 7% 5% 4 4 3 5% 7% 34%	5114
June	1st to 10th	Night	18% 7% 2 7% 4 4 6% 4 6% 9% 32%	1680
	11th to 20th	Night	15% 6% 3 6% 4 5% 4 4 7% 8% 39%	1640
	21st to end	Night	18% 7% 2 6% 5% 5% 5% 4 6% 7% 36%	1600
July	1st to 10th	Night	14% 6% 2 6% 5% 5% 4 4 7% 9% 38%	3600
	11th to 20th	Night	14% 7% 3 6% 4 3 4 3 6% 8% 43%	3600
	21st to end	Night	10% 7% 2 5% 4 4 4 4 5% 8% 46%	3926
August	1st to 10th	Night	13% 7% 3 6% 4 5% 4 4 6% 7% 40%	2731
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 6% 8% 38%	2936
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 4 7% 9% 40%	3586
September	1st to 10th	Night	14% 6% 2 7% 5% 4 4 3 5% 7% 45%	2000
	11th to 20th	Night	13% 5% 2 5% 4 3 4 2 5% 7% 49%	2000
	21st to end	Night	17% 6% 2 7% 4 4 4 3 6% 7% 40%	2257
October	1st to 10th	Night	20% 9% 3 6% 5% 4 4 3 4 7% 35%	2400
	11th to 20th	Night	19% 9% 3 7% 5% 4 5% 3 5% 6% 32%	2400
	21st to end	Night	26% 10% 3 7% 6% 4 4 4 4 5% 27%	2780
November	1st to 10th	Night	20% 11% 3 8% 4 4 4 3 5% 6% 33%	2667
	11th to 20th	Night	18% 12% 3 8% 5% 4 5% 4 5% 5% 30%	2884
	21st to end	Night	22% 17% 4 8% 4 5% 4 4 5% 6% 21%	2940
December	1st to 10th	Night	20% 22% 6% 13% 6% 6% 5% 3 4 4 12%	4720
	11th to 20th	Night	23% 17% 5% 9% 5% 3 4 2 3 4 24%	5348
	21st to end	Night	26% 16% 5% 11% 5% 4 4 3 4 5% 18%	7150

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	71% 5% 9% 11% 3	4662
	11th to 20th	Day	77% 5% 5% 6% 6% 1	4680
	21st to end	Day	73% 5% 7% 8% 5% 1	5478
February	1st to 10th	Day	68% 5% 8% 14% 4 1	1890
	11th to 20th	Day	65% 4 8% 15% 7% 1	1881
	21st to end	Day	68% 4 7% 12% 7% 1	1730
March	1st to 10th	Day	61% 5% 8% 14% 10% 2	4596
	11th to 20th	Day	55% 6% 15% 14% 10% 1	5090
	21st to end	Day	55% 5% 6% 17% 15% 2	5901
April	1st to 10th	Day	57% 4 7% 18% 12% 2	2520
	11th to 20th	Day	51% 5% 7% 20% 15% 2	2494
	21st to end	Day	53% 6% 8% 17% 14% 3	2596
May	1st to 10th	Day	57% 5% 8% 20% 9% 1	8249
	11th to 20th	Day	50% 7% 11% 22% 10% 1	8225
	21st to end	Day	51% 6% 10% 23% 9% 1	9061
June	1st to 10th	Day	50% 7% 10% 20% 12% 1	2940
	11th to 20th	Day	45% 6% 11% 26% 11% 1	2870
	21st to end	Day	48% 7% 11% 22% 11% 1	2800
July	1st to 10th	Day	40% 6% 13% 28% 12%	6290
	11th to 20th	Day	38% 8% 14% 27% 13% 1	6285
	21st to end	Day	35% 7% 13% 36% 9%	6728
August	1st to 10th	Day	45% 6% 14% 24% 10%	4400
	11th to 20th	Day	43% 9% 15% 25% 8% 1	4119
	21st to end	Day	41% 6% 14% 29% 9%	4312
September	1st to 10th	Day	39% 6% 14% 29% 12% 1	2400
	11th to 20th	Day	36% 5% 11% 30% 16% 1	2399
	21st to end	Day	46% 6% 12% 25% 11%	2140
October	1st to 10th	Day	46% 6% 11% 27% 10%	3260
	11th to 20th	Day	47% 5% 15% 24% 8%	3240
	21st to end	Day	48% 5% 15% 24% 6%	3311
November	1st to 10th	Day	53% 7% 12% 20% 8% 1	1851
	11th to 20th	Day	58% 6% 11% 15% 8% 2	1732
	21st to end	Day	68% 6% 11% 9% 6%	1680
December	1st to 10th	Day	73% 6% 11% 8% 1	2680
	11th to 20th	Day	70% 6% 8% 11% 5%	3066
	21st to end	Day	68% 5% 9% 14% 4	4048
January	1st to 10th	Night	72% 5% 10% 10% 4	8234
	11th to 20th	Night	79% 5% 5% 7% 3	8280
	21st to end	Night	71% 6% 7% 9% 7% 1	8699
February	1st to 10th	Night	69% 5% 8% 12% 6%	2730
	11th to 20th	Night	63% 4 9% 17% 6%	2635
	21st to end	Night	63% 4 10% 15% 7% 1	2076
March	1st to 10th	Night	60% 4 7% 17% 10% 2	5461
	11th to 20th	Night	53% 5% 15% 16% 8% 3	5090
	21st to end	Night	60% 4 4 20% 11% 2	5272
April	1st to 10th	Night	54% 4 9% 19% 13% 1	2100
	11th to 20th	Night	53% 5% 9% 17% 15% 1	2075
	21st to end	Night	52% 5% 8% 17% 14% 3	2042
May	1st to 10th	Night	60% 6% 8% 16% 8% 2	4666
	11th to 20th	Night	50% 7% 11% 20% 11% 1	4640
	21st to end	Night	49% 5% 10% 20% 14% 1	5115
June	1st to 10th	Night	46% 7% 12% 21% 12% 1	1680
	11th to 20th	Night	42% 6% 13% 21% 16% 2	1640
	21st to end	Night	46% 7% 12% 22% 12% 1	1600
July	1st to 10th	Night	41% 7% 16% 22% 13% 1	3560
	11th to 20th	Night	39% 6% 13% 29% 11% 1	3552
	21st to end	Night	35% 7% 13% 31% 14%	3809
August	1st to 10th	Night	42% 7% 15% 24% 11% 1	2721
	11th to 20th	Night	43% 7% 13% 26% 10% 1	2963
	21st to end	Night	37% 8% 14% 31% 10% 1	3586
September	1st to 10th	Night	38% 7% 13% 29% 12% 1	2000
	11th to 20th	Night	34% 5% 13% 32% 16% 1	2000
	21st to end	Night	43% 6% 12% 26% 13% 1	2257
October	1st to 10th	Night	45% 6% 11% 26% 11% 1	3920
	11th to 20th	Night	46% 5% 14% 24% 10%	3899
	21st to end	Night	52% 6% 13% 22% 6%	4479
November	1st to 10th	Night	52% 5% 14% 19% 9% 1	2667
	11th to 20th	Night	55% 6% 11% 18% 8% 2	2884
	21st to end	Night	64% 6% 11% 15% 4	2940
December	1st to 10th	Night	76% 6% 8% 8% 2	4720
	11th to 20th	Night	66% 5% 8% 14% 6%	5348
	21st to end	Night	70% 5% 7% 11% 6%	7150

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% 34% 10% 4 1	220
	11th to 20th	Day	34% 23% 27% 14% 2	220
	21st to end	Day	28% 23% 30% 15% 4	306
February	1st to 10th	Day	31% 28% 30% 9% 2	330
	11th to 20th	Day	31% 30% 30% 7% 1	359
	21st to end	Day	38% 23% 28% 10% 1	446
March	1st to 10th	Day	30% 21% 28% 15% 4 1	540
	11th to 20th	Day	34% 21% 29% 12% 3 1	540
	21st to end	Day	36% 22% 26% 11% 4 1	594
April	1st to 10th	Day	34% 23% 27% 12% 4	540
	11th to 20th	Day	35% 20% 22% 14% 5% 3	532
	21st to end	Day	34% 20% 27% 12% 6% 1	540
May	1st to 10th	Day	30% 20% 27% 14% 7% 2	543
	11th to 20th	Day	21% 16% 36% 19% 7% 2	567
	21st to end	Day	22% 18% 30% 21% 8% 2	617
June	1st to 10th	Day	25% 15% 31% 21% 6% 1	570
	11th to 20th	Day	18% 17% 34% 20% 9% 2	550
	21st to end	Day	24% 14% 35% 18% 7% 2	530
July	1st to 10th	Day	14% 11% 33% 26% 14% 2	525
	11th to 20th	Day	17% 10% 30% 27% 12% 3	524
	21st to end	Day	14% 10% 38% 26% 11% 1	576
August	1st to 10th	Day	14% 8% 31% 28% 15% 4	526
	11th to 20th	Day	16% 8% 27% 26% 15% 6%	519
	21st to end	Day	17% 11% 29% 23% 14% 5%	583
September	1st to 10th	Day	19% 11% 28% 22% 12% 8%	530
	11th to 20th	Day	12% 9% 27% 21% 20% 11%	530
	21st to end	Day	20% 12% 26% 25% 13% 4	530
October	1st to 10th	Day	27% 14% 24% 20% 11% 5%	530
	11th to 20th	Day	24% 23% 30% 15% 7% 1	530
	21st to end	Day	34% 16% 27% 18% 5%	506
November	1st to 10th	Day	29% 20% 27% 16% 7%	425
	11th to 20th	Day	28% 19% 32% 11% 7% 2	272
	21st to end	Day	34% 20% 32% 12% 2	220
December	1st to 10th	Day	37% 18% 28% 14% 2	220
	11th to 20th	Day	31% 25% 33% 9% 2	220
	21st to end	Day	36% 18% 28% 15% 3	242
January	1st to 10th	Night	32% 19% 29% 16% 4	840
	11th to 20th	Night	31% 20% 27% 17% 4	840
	21st to end	Night	24% 20% 28% 22% 6%	924
February	1st to 10th	Night	27% 22% 30% 19% 2	840
	11th to 20th	Night	26% 19% 35% 16% 3	823
	21st to end	Night	28% 17% 34% 18% 3	692
March	1st to 10th	Night	29% 18% 30% 19% 4	840
	11th to 20th	Night	32% 18% 28% 17% 4 1	840
	21st to end	Night	29% 17% 29% 19% 6% 1	924
April	1st to 10th	Night	30% 16% 30% 21% 3	840
	11th to 20th	Night	29% 18% 28% 20% 5%	831
	21st to end	Night	27% 13% 30% 21% 8%	782
May	1st to 10th	Night	30% 10% 25% 26% 8% 1	420
	11th to 20th	Night	17% 12% 35% 30% 6%	414
	21st to end	Night	18% 11% 32% 31% 8%	455
June	1st to 10th	Night	21% 9% 26% 35% 8%	420
	11th to 20th	Night	16% 11% 29% 32% 12%	410
	21st to end	Night	20% 7% 30% 32% 11%	400
July	1st to 10th	Night	13% 5% 31% 38% 13% 1	390
	11th to 20th	Night	13% 5% 27% 36% 18% 1	388
	21st to end	Night	15% 6% 28% 39% 11% 1	438
August	1st to 10th	Night	14% 3 24% 40% 18% 1	478
	11th to 20th	Night	19% 5% 18% 35% 21% 2	629
	21st to end	Night	14% 5% 29% 35% 16% 1	880
September	1st to 10th	Night	17% 7% 26% 33% 16% 2	800
	11th to 20th	Night	16% 5% 20% 32% 23% 5%	800
	21st to end	Night	18% 11% 25% 28% 18% 2	800
October	1st to 10th	Night	26% 12% 26% 21% 15% 1	800
	11th to 20th	Night	26% 13% 28% 24% 8% 1	800
	21st to end	Night	34% 12% 29% 21% 4	880
November	1st to 10th	Night	30% 13% 28% 21% 7% 1	820
	11th to 20th	Night	26% 16% 29% 20% 8% 1	840
	21st to end	Night	36% 16% 27% 16% 5%	840
December	1st to 10th	Night	36% 17% 26% 17% 4	840
	11th to 20th	Night	32% 20% 30% 15% 3 1	840
	21st to end	Night	37% 16% 28% 17% 2	924

Page generated at 2026-06-13 02:31:44. Version ac07

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