Mooselook Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mooselook Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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	16% 12% 4 10% 6% 5% 5% 4 5% 7% 28%	101360
	Night	16% 13% 5% 10% 6% 5% 5% 4 5% 6% 27%	98751
Transparency	Day	53% 8% 12% 17% 9% 1	104859
	Night	54% 9% 11% 17% 9% 1	103329
Seeing	Day	25% 21% 28% 17% 7% 2	14942
	Night	23% 18% 26% 23% 9% 1	24006

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	12% 14% 8% 15% 8% 5% 5% 3 5% 6% 19%	2517
	11th to 20th	Day	10% 13% 6% 20% 10% 7% 4 4 5% 5% 17%	2520
	21st to end	Day	13% 12% 7% 14% 7% 6% 5% 4 4 4 23%	2772
February	1st to 10th	Day	12% 14% 6% 11% 9% 7% 6% 4 4 6% 22%	1617
	11th to 20th	Day	10% 14% 7% 15% 9% 6% 4 4 4 6% 21%	1848
	21st to end	Day	11% 15% 4 11% 7% 7% 5% 5% 6% 6% 23%	1570
March	1st to 10th	Day	17% 16% 6% 11% 6% 5% 4 4 3 4 23%	3116
	11th to 20th	Day	15% 18% 8% 12% 5% 4 3 3 4 5% 23%	3370
	21st to end	Day	17% 14% 6% 11% 6% 4 3 3 4 5% 28%	3993
April	1st to 10th	Day	18% 14% 5% 11% 5% 4 3 3 4 5% 28%	2280
	11th to 20th	Day	14% 14% 4 7% 5% 4 5% 4 4 6% 33%	2336
	21st to end	Day	18% 15% 5% 10% 5% 4 3 3 4 5% 27%	2470
May	1st to 10th	Day	22% 13% 4 8% 5% 5% 5% 4 5% 5% 26%	4106
	11th to 20th	Day	19% 11% 3 9% 6% 5% 5% 4 5% 6% 25%	4295
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 7% 10% 33%	4837
June	1st to 10th	Day	23% 11% 3 7% 5% 4 5% 3 6% 8% 25%	2660
	11th to 20th	Day	17% 9% 3 6% 6% 5% 5% 5% 6% 7% 32%	2660
	21st to end	Day	21% 9% 3 9% 6% 5% 5% 4 5% 7% 26%	2660
July	1st to 10th	Day	14% 8% 2 7% 5% 6% 6% 6% 8% 9% 30%	4440
	11th to 20th	Day	13% 7% 3 7% 5% 6% 6% 5% 8% 11% 31%	4440
	21st to end	Day	14% 8% 3 8% 6% 5% 5% 4 6% 7% 34%	4814
August	1st to 10th	Day	16% 9% 4 9% 6% 6% 5% 4 6% 8% 28%	4247
	11th to 20th	Day	15% 9% 3 10% 7% 6% 6% 5% 7% 8% 24%	4045
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 7% 9% 36%	4311
September	1st to 10th	Day	13% 6% 2 7% 5% 4 4 4 6% 8% 41%	2270
	11th to 20th	Day	14% 8% 2 6% 4 3 4 4 5% 7% 44%	2090
	21st to end	Day	15% 10% 3 7% 4 4 5% 4 7% 8% 34%	2090
October	1st to 10th	Day	19% 12% 3 7% 5% 4 4 3 5% 7% 31%	2090
	11th to 20th	Day	15% 16% 4 10% 5% 3 4 3 4 6% 30%	1793
	21st to end	Day	18% 20% 5% 10% 5% 4 3 2 4 5% 25%	1881
November	1st to 10th	Day	15% 14% 5% 9% 6% 5% 4 3 5% 6% 30%	1761
	11th to 20th	Day	15% 14% 7% 13% 6% 5% 4 3 4 6% 24%	1800
	21st to end	Day	17% 15% 5% 12% 5% 4 4 3 6% 6% 23%	1712
December	1st to 10th	Day	17% 19% 7% 15% 7% 5% 4 3 3 4 17%	1400
	11th to 20th	Day	19% 16% 5% 9% 5% 5% 3 2 5% 5% 25%	1753
	21st to end	Day	19% 15% 5% 12% 7% 5% 5% 3 5% 4 18%	2796
January	1st to 10th	Night	11% 13% 8% 17% 10% 5% 5% 3 5% 5% 19%	4429
	11th to 20th	Night	11% 15% 7% 17% 12% 6% 6% 4 4 5% 14%	4440
	21st to end	Night	12% 14% 7% 16% 7% 8% 5% 4 5% 5% 17%	4884
February	1st to 10th	Night	11% 13% 5% 13% 8% 7% 6% 4 5% 6% 21%	2559
	11th to 20th	Night	8% 14% 6% 14% 7% 8% 6% 6% 5% 5% 21%	2218
	21st to end	Night	11% 14% 5% 10% 8% 6% 5% 3 5% 6% 27%	1884
March	1st to 10th	Night	19% 17% 5% 9% 5% 5% 4 3 4 4 24%	3724
	11th to 20th	Night	14% 16% 9% 12% 6% 5% 5% 3 4 4 23%	3589
	21st to end	Night	20% 16% 5% 9% 7% 3 3 3 3 6% 24%	3636
April	1st to 10th	Night	17% 16% 5% 8% 4 4 4 3 5% 4 28%	1900
	11th to 20th	Night	16% 12% 4 7% 5% 4 5% 5% 5% 5% 33%	1792
	21st to end	Night	20% 12% 4 8% 4 4 4 3 6% 5% 30%	1710
May	1st to 10th	Night	24% 12% 3 6% 4 4 4 4 6% 6% 28%	2834
	11th to 20th	Night	18% 12% 4 8% 5% 5% 5% 3 6% 7% 27%	2627
	21st to end	Night	15% 8% 2 7% 4 4 5% 4 6% 9% 36%	2738
June	1st to 10th	Night	23% 12% 3 8% 5% 3 4 3 4 6% 30%	1520
	11th to 20th	Night	17% 10% 3 5% 4 4 4 4 5% 7% 36%	1520
	21st to end	Night	20% 9% 3 8% 5% 5% 4 4 6% 7% 30%	1520
July	1st to 10th	Night	14% 9% 3 7% 5% 5% 5% 5% 6% 8% 33%	2520
	11th to 20th	Night	18% 7% 3 8% 5% 4 5% 4 6% 6% 35%	2520
	21st to end	Night	12% 9% 3 7% 5% 5% 5% 4 6% 7% 36%	2739
August	1st to 10th	Night	21% 11% 3 8% 4 4 5% 4 5% 6% 29%	2652
	11th to 20th	Night	14% 8% 3 11% 7% 5% 5% 4 6% 7% 30%	2782
	21st to end	Night	15% 8% 3 6% 4 4 4 4 4 6% 42%	3342
September	1st to 10th	Night	13% 6% 2 6% 5% 4 4 4 5% 8% 43%	1909
	11th to 20th	Night	16% 7% 2 5% 4 3 4 3 4 5% 47%	2090
	21st to end	Night	16% 9% 2 6% 4 4 4 3 4 8% 40%	2090
October	1st to 10th	Night	17% 10% 3 7% 5% 5% 5% 3 5% 6% 34%	2090
	11th to 20th	Night	17% 14% 3 8% 5% 5% 4 3 5% 6% 30%	2384
	21st to end	Night	20% 17% 4 9% 5% 3 5% 3 5% 5% 24%	2717
November	1st to 10th	Night	16% 15% 4 9% 5% 4 5% 3 5% 6% 29%	2537
	11th to 20th	Night	14% 13% 6% 13% 5% 4 4 3 5% 6% 26%	2600
	21st to end	Night	15% 14% 6% 14% 8% 6% 4 3 4 5% 22%	2679
December	1st to 10th	Night	18% 18% 7% 15% 7% 5% 4 3 4 3 17%	3000
	11th to 20th	Night	18% 16% 6% 13% 7% 5% 5% 3 4 5% 17%	3643
	21st to end	Night	19% 16% 5% 13% 5% 4 4 4 4 5% 20%	4933

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	60% 10% 10% 15% 5%	2518
	11th to 20th	Day	62% 11% 7% 13% 6% 1	2520
	21st to end	Day	57% 10% 11% 12% 9% 2	2772
February	1st to 10th	Day	62% 7% 8% 13% 9% 2	1617
	11th to 20th	Day	62% 7% 9% 12% 8% 2	1857
	21st to end	Day	59% 6% 9% 15% 8% 3	1570
March	1st to 10th	Day	64% 6% 7% 10% 11% 3	3119
	11th to 20th	Day	57% 10% 8% 14% 8% 3	3370
	21st to end	Day	54% 8% 5% 15% 15% 3	3993
April	1st to 10th	Day	59% 5% 8% 14% 10% 3	2280
	11th to 20th	Day	50% 7% 10% 19% 12% 1	2336
	21st to end	Day	58% 6% 8% 15% 9% 3	2470
May	1st to 10th	Day	57% 10% 8% 17% 6% 1	4120
	11th to 20th	Day	55% 11% 14% 13% 6% 1	4299
	21st to end	Day	42% 11% 15% 21% 11%	4837
June	1st to 10th	Day	56% 9% 12% 18% 5%	2660
	11th to 20th	Day	48% 7% 13% 19% 10% 1	2660
	21st to end	Day	57% 9% 12% 16% 7% 1	2660
July	1st to 10th	Day	45% 9% 18% 19% 9%	4370
	11th to 20th	Day	43% 10% 17% 26% 4	4365
	21st to end	Day	47% 8% 11% 26% 7%	4661
August	1st to 10th	Day	53% 8% 15% 18% 5%	4233
	11th to 20th	Day	54% 10% 15% 17% 4	4084
	21st to end	Day	41% 9% 14% 21% 13% 2	4311
September	1st to 10th	Day	38% 9% 14% 26% 12% 1	2270
	11th to 20th	Day	40% 5% 12% 27% 14% 2	2090
	21st to end	Day	44% 9% 13% 22% 11% 1	2090
October	1st to 10th	Day	53% 8% 11% 18% 10%	3480
	11th to 20th	Day	52% 6% 10% 22% 10%	2944
	21st to end	Day	49% 5% 15% 18% 12% 1	3081
November	1st to 10th	Day	53% 7% 12% 17% 10% 1	1761
	11th to 20th	Day	60% 6% 9% 12% 10% 3	1800
	21st to end	Day	59% 7% 14% 14% 5% 1	1712
December	1st to 10th	Day	70% 6% 7% 10% 7% 1	1400
	11th to 20th	Day	60% 7% 6% 12% 14% 1	1753
	21st to end	Day	62% 11% 8% 10% 9% 1	2796
January	1st to 10th	Night	59% 10% 10% 15% 5%	4429
	11th to 20th	Night	62% 14% 9% 10% 3 1	4440
	21st to end	Night	64% 9% 6% 12% 7% 1	4884
February	1st to 10th	Night	59% 9% 10% 13% 8% 2	2559
	11th to 20th	Night	56% 10% 10% 15% 8% 1	2220
	21st to end	Night	55% 7% 7% 16% 12% 2	1884
March	1st to 10th	Night	60% 7% 8% 14% 7% 3	3734
	11th to 20th	Night	59% 10% 10% 12% 8% 1	3590
	21st to end	Night	58% 7% 6% 14% 14% 2	3636
April	1st to 10th	Night	57% 6% 8% 15% 13% 1	1900
	11th to 20th	Night	48% 7% 12% 19% 13% 1	1792
	21st to end	Night	54% 7% 11% 16% 11% 2	1710
May	1st to 10th	Night	53% 11% 14% 15% 6% 1	2840
	11th to 20th	Night	52% 11% 14% 16% 7% 1	2628
	21st to end	Night	40% 13% 16% 19% 12%	2739
June	1st to 10th	Night	54% 7% 12% 19% 8%	1520
	11th to 20th	Night	45% 8% 13% 22% 11% 2	1520
	21st to end	Night	51% 8% 14% 18% 8% 1	1520
July	1st to 10th	Night	46% 9% 16% 20% 9%	2480
	11th to 20th	Night	47% 8% 13% 28% 5%	2472
	21st to end	Night	44% 10% 14% 24% 8%	2651
August	1st to 10th	Night	55% 7% 13% 20% 5%	2642
	11th to 20th	Night	50% 10% 17% 15% 7%	2809
	21st to end	Night	43% 7% 14% 21% 13% 3	3342
September	1st to 10th	Night	36% 9% 15% 28% 11%	1909
	11th to 20th	Night	39% 6% 12% 29% 13% 1	2090
	21st to end	Night	42% 7% 14% 25% 11% 1	2090
October	1st to 10th	Night	47% 9% 13% 19% 12%	3480
	11th to 20th	Night	52% 6% 11% 18% 13%	3959
	21st to end	Night	51% 6% 14% 18% 10% 1	4467
November	1st to 10th	Night	54% 7% 12% 18% 8% 1	2537
	11th to 20th	Night	57% 7% 10% 15% 9% 3	2600
	21st to end	Night	60% 8% 11% 14% 6% 1	2679
December	1st to 10th	Night	70% 6% 8% 11% 5% 1	3000
	11th to 20th	Night	64% 9% 7% 12% 8%	3644
	21st to end	Night	61% 12% 8% 12% 7%	4933

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	25% 27% 34% 13% 2	180
	11th to 20th	Day	32% 24% 28% 11% 3 1	180
	21st to end	Day	20% 24% 34% 18% 3 1	198
February	1st to 10th	Day	29% 29% 25% 15% 2 1	269
	11th to 20th	Day	30% 32% 25% 11% 2	456
	21st to end	Day	29% 27% 27% 15% 2	382
March	1st to 10th	Day	27% 24% 32% 15% 3	460
	11th to 20th	Day	30% 27% 26% 12% 4 1	460
	21st to end	Day	33% 22% 24% 13% 6% 2	506
April	1st to 10th	Day	34% 23% 26% 12% 5% 1	460
	11th to 20th	Day	31% 26% 22% 13% 5% 3	452
	21st to end	Day	28% 24% 27% 13% 5% 2	460
May	1st to 10th	Day	35% 21% 24% 14% 5% 2	463
	11th to 20th	Day	23% 21% 33% 14% 7% 2	487
	21st to end	Day	21% 20% 35% 16% 7% 1	529
June	1st to 10th	Day	27% 17% 36% 14% 6% 1	490
	11th to 20th	Day	20% 19% 29% 21% 10% 1	490
	21st to end	Day	24% 17% 32% 17% 8% 2	490
July	1st to 10th	Day	19% 16% 35% 20% 9% 2	485
	11th to 20th	Day	16% 14% 38% 22% 9% 2	484
	21st to end	Day	16% 12% 36% 27% 8% 2	532
August	1st to 10th	Day	17% 14% 30% 25% 12% 3	486
	11th to 20th	Day	17% 15% 28% 23% 11% 6%	479
	21st to end	Day	15% 19% 26% 24% 11% 5%	539
September	1st to 10th	Day	15% 16% 29% 22% 13% 4	490
	11th to 20th	Day	20% 14% 25% 18% 15% 9%	490
	21st to end	Day	19% 16% 25% 22% 13% 5%	490
October	1st to 10th	Day	24% 18% 24% 19% 11% 4	490
	11th to 20th	Day	26% 19% 27% 15% 11% 2	405
	21st to end	Day	33% 24% 24% 15% 5%	429
November	1st to 10th	Day	32% 19% 24% 19% 5% 1	395
	11th to 20th	Day	28% 25% 27% 12% 7% 2	400
	21st to end	Day	33% 25% 24% 13% 4 1	332
December	1st to 10th	Day	29% 29% 25% 13% 4	200
	11th to 20th	Day	38% 24% 26% 8% 4 2	200
	21st to end	Day	32% 28% 28% 9% 2 1	204
January	1st to 10th	Night	21% 25% 33% 18% 3	760
	11th to 20th	Night	25% 23% 28% 20% 3	760
	21st to end	Night	19% 25% 33% 19% 3 1	836
February	1st to 10th	Night	20% 26% 32% 19% 3	760
	11th to 20th	Night	21% 28% 31% 18% 2	743
	21st to end	Night	23% 24% 31% 19% 3	628
March	1st to 10th	Night	25% 21% 32% 20% 2	760
	11th to 20th	Night	26% 22% 26% 20% 6%	760
	21st to end	Night	24% 19% 27% 22% 7% 1	836
April	1st to 10th	Night	29% 20% 27% 19% 5%	760
	11th to 20th	Night	23% 17% 30% 25% 6%	668
	21st to end	Night	29% 17% 28% 19% 7%	570
May	1st to 10th	Night	26% 13% 27% 26% 7% 1	570
	11th to 20th	Night	22% 10% 29% 30% 8% 1	454
	21st to end	Night	17% 10% 29% 33% 10%	411
June	1st to 10th	Night	27% 11% 25% 27% 9% 1	380
	11th to 20th	Night	21% 8% 26% 27% 18%	380
	21st to end	Night	20% 9% 23% 36% 11%	380
July	1st to 10th	Night	14% 6% 26% 36% 16% 1	370
	11th to 20th	Night	16% 6% 23% 35% 18% 2	368
	21st to end	Night	15% 6% 21% 40% 18%	416
August	1st to 10th	Night	16% 7% 20% 36% 21%	459
	11th to 20th	Night	15% 9% 26% 29% 20% 1	562
	21st to end	Night	17% 8% 21% 32% 19% 2	754
September	1st to 10th	Night	14% 10% 22% 36% 16% 2	760
	11th to 20th	Night	19% 10% 21% 24% 22% 4	760
	21st to end	Night	19% 11% 24% 27% 17% 2	760
October	1st to 10th	Night	23% 14% 21% 25% 16% 1	760
	11th to 20th	Night	24% 17% 24% 22% 11% 2	760
	21st to end	Night	30% 19% 26% 20% 5%	836
November	1st to 10th	Night	25% 21% 25% 21% 8% 1	780
	11th to 20th	Night	26% 21% 26% 19% 7% 2	800
	21st to end	Night	28% 24% 22% 20% 4 2	807
December	1st to 10th	Night	30% 23% 27% 15% 5%	900
	11th to 20th	Night	30% 25% 24% 17% 4	887
	21st to end	Night	30% 23% 28% 17% 2	851

Page generated at 2024-12-21 04:13:50. Version ac07

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