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 2026-04-17.

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	15% 11% 4 10% 6% 5% 5% 4 5% 7% 27%	130569
	Night	14% 13% 5% 12% 7% 6% 5% 4 5% 6% 25%	131597
Transparency	Day	54% 8% 11% 17% 9% 1	134050
	Night	56% 8% 10% 16% 9% 1	136191
Seeing	Day	26% 21% 28% 16% 7% 2	16574
	Night	23% 18% 26% 23% 8% 1	25725

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	9% 14% 8% 17% 8% 8% 6% 3 4 5% 18%	4661
	11th to 20th	Day	6% 13% 7% 20% 13% 8% 5% 3 4 5% 16%	4650
	21st to end	Day	7% 8% 6% 15% 8% 9% 9% 4 6% 5% 23%	5124
February	1st to 10th	Day	11% 13% 5% 11% 10% 7% 5% 4 5% 6% 23%	1789
	11th to 20th	Day	10% 13% 7% 15% 10% 7% 4 4 4 5% 22%	2048
	21st to end	Day	11% 15% 4 12% 7% 7% 5% 5% 6% 6% 23%	1730
March	1st to 10th	Day	13% 15% 6% 15% 7% 5% 5% 3 3 4 22%	4576
	11th to 20th	Day	13% 14% 6% 11% 5% 4 4 4 5% 6% 29%	4920
	21st to end	Day	19% 13% 6% 11% 6% 4 4 3 4 5% 25%	5853
April	1st to 10th	Day	17% 15% 5% 11% 5% 4 3 3 4 5% 27%	2520
	11th to 20th	Day	14% 14% 4 8% 5% 4 5% 4 4 6% 32%	2533
	21st to end	Day	18% 15% 5% 10% 5% 4 3 3 4 5% 28%	2600
May	1st to 10th	Day	25% 15% 5% 9% 5% 5% 5% 4 4 5% 20%	5886
	11th to 20th	Day	19% 12% 4 9% 6% 6% 5% 4 5% 6% 25%	6173
	21st to end	Day	19% 9% 3 7% 5% 4 5% 4 6% 8% 29%	6949
June	1st to 10th	Day	23% 11% 3 7% 5% 4 5% 3 6% 8% 25%	2800
	11th to 20th	Day	17% 9% 3 7% 6% 4 5% 5% 6% 8% 32%	2800
	21st to end	Day	21% 9% 3 9% 6% 5% 5% 4 6% 7% 27%	2800
July	1st to 10th	Day	14% 9% 3 8% 6% 6% 7% 6% 9% 9% 25%	6360
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 5% 7% 10% 33%	6360
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 6% 8% 38%	6926
August	1st to 10th	Day	16% 8% 4 8% 6% 6% 5% 4 6% 8% 29%	4381
	11th to 20th	Day	14% 8% 3 10% 7% 6% 6% 5% 7% 8% 25%	4175
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 6% 9% 36%	4447
September	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 6% 8% 42%	2389
	11th to 20th	Day	14% 8% 2 6% 4 3 4 4 5% 7% 45%	2200
	21st to end	Day	15% 10% 3 7% 4 4 5% 4 7% 8% 35%	2200
October	1st to 10th	Day	18% 12% 3 7% 4 4 4 3 5% 7% 34%	2200
	11th to 20th	Day	16% 16% 4 9% 4 3 4 3 4 7% 30%	1887
	21st to end	Day	18% 20% 5% 10% 5% 4 2 2 4 5% 25%	1980
November	1st to 10th	Day	15% 15% 5% 9% 5% 4 4 3 5% 5% 29%	1851
	11th to 20th	Day	14% 15% 8% 13% 6% 4 4 3 4 6% 23%	1890
	21st to end	Day	17% 15% 6% 13% 5% 4 4 3 5% 6% 22%	1797
December	1st to 10th	Day	11% 18% 6% 21% 12% 5% 4 3 3 4 14%	2350
	11th to 20th	Day	16% 14% 8% 11% 6% 5% 4 2 4 4 26%	2716
	21st to end	Day	15% 15% 5% 13% 7% 5% 5% 3 5% 4 23%	4048
January	1st to 10th	Night	8% 14% 8% 19% 10% 9% 6% 3 4 4 15%	8234
	11th to 20th	Night	8% 16% 8% 19% 13% 8% 6% 4 4 4 11%	8235
	21st to end	Night	7% 10% 5% 14% 8% 11% 10% 5% 6% 5% 19%	9057
February	1st to 10th	Night	10% 12% 5% 13% 8% 7% 6% 4 5% 6% 22%	2827
	11th to 20th	Night	7% 14% 5% 14% 8% 9% 5% 6% 5% 5% 21%	2458
	21st to end	Night	10% 14% 5% 11% 8% 6% 5% 3 5% 6% 27%	2076
March	1st to 10th	Night	16% 16% 6% 15% 6% 6% 4 3 4 4 19%	5484
	11th to 20th	Night	12% 13% 7% 12% 6% 6% 5% 4 5% 5% 25%	5259
	21st to end	Night	16% 15% 5% 11% 7% 4 4 3 4 6% 24%	5318
April	1st to 10th	Night	18% 17% 5% 9% 4 4 4 3 5% 4 28%	2100
	11th to 20th	Night	17% 13% 4 7% 5% 4 5% 4 5% 5% 32%	1948
	21st to end	Night	20% 12% 4 8% 4 4 4 3 5% 5% 30%	1800
May	1st to 10th	Night	26% 14% 4 8% 4 4 4 3 5% 5% 23%	4054
	11th to 20th	Night	20% 13% 3 7% 4 4 5% 3 5% 7% 28%	3763
	21st to end	Night	18% 11% 3 7% 4 4 4 3 6% 7% 34%	3926
June	1st to 10th	Night	23% 11% 3 8% 5% 3 4 3 4 6% 31%	1600
	11th to 20th	Night	17% 10% 3 6% 5% 4 4 4 5% 7% 36%	1600
	21st to end	Night	20% 8% 3 8% 5% 5% 4 4 6% 7% 30%	1600
July	1st to 10th	Night	15% 9% 3 8% 5% 5% 5% 4 6% 9% 31%	3600
	11th to 20th	Night	16% 6% 3 8% 6% 4 5% 4 5% 7% 36%	3600
	21st to end	Night	10% 9% 3 7% 5% 5% 5% 4 7% 8% 38%	3926
August	1st to 10th	Night	20% 11% 3 7% 4 4 5% 4 5% 6% 31%	2736
	11th to 20th	Night	14% 8% 3 11% 7% 5% 5% 4 5% 7% 30%	2872
	21st to end	Night	15% 8% 3 6% 4 4 4 4 4 6% 41%	3448
September	1st to 10th	Night	12% 6% 2 6% 5% 3 4 4 5% 8% 44%	2010
	11th to 20th	Night	15% 7% 2 5% 4 3 4 3 4 5% 48%	2200
	21st to end	Night	16% 9% 3 6% 4 4 4 3 4 8% 41%	2200
October	1st to 10th	Night	17% 10% 3 7% 5% 4 4 3 5% 7% 36%	2200
	11th to 20th	Night	17% 15% 3 8% 5% 5% 4 3 5% 6% 30%	2510
	21st to end	Night	20% 17% 4 9% 5% 4 5% 4 5% 6% 23%	2860
November	1st to 10th	Night	16% 15% 5% 9% 5% 4 5% 3 5% 6% 28%	2667
	11th to 20th	Night	14% 14% 7% 14% 5% 4 4 3 4 6% 25%	2730
	21st to end	Night	15% 14% 6% 14% 8% 6% 4 3 4 5% 21%	2813
December	1st to 10th	Night	12% 17% 8% 22% 11% 4 4 3 3 3 12%	5060
	11th to 20th	Night	16% 17% 6% 14% 8% 6% 5% 3 4 5% 16%	5676
	21st to end	Night	15% 16% 5% 13% 6% 5% 4 3 4 5% 24%	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	65% 7% 9% 13% 5%	4662
	11th to 20th	Day	66% 8% 7% 11% 6% 2	4680
	21st to end	Day	55% 9% 10% 11% 13% 2	5124
February	1st to 10th	Day	61% 6% 8% 13% 10% 2	1789
	11th to 20th	Day	61% 6% 9% 13% 9% 2	2057
	21st to end	Day	58% 6% 8% 15% 9% 3	1730
March	1st to 10th	Day	64% 6% 7% 9% 9% 5%	4579
	11th to 20th	Day	52% 9% 13% 16% 8% 2	4920
	21st to end	Day	57% 8% 6% 14% 13% 2	5853
April	1st to 10th	Day	59% 5% 8% 15% 10% 3	2520
	11th to 20th	Day	52% 7% 10% 18% 12% 2	2533
	21st to end	Day	57% 6% 8% 16% 9% 3	2600
May	1st to 10th	Day	65% 8% 7% 14% 5% 1	5897
	11th to 20th	Day	56% 11% 12% 14% 6% 2	6177
	21st to end	Day	48% 10% 12% 20% 10% 1	6949
June	1st to 10th	Day	56% 8% 12% 18% 6%	2800
	11th to 20th	Day	48% 8% 13% 20% 10% 1	2800
	21st to end	Day	55% 9% 11% 17% 7% 1	2800
July	1st to 10th	Day	49% 9% 19% 16% 7%	6290
	11th to 20th	Day	42% 10% 15% 26% 6%	6285
	21st to end	Day	42% 8% 13% 29% 8%	6728
August	1st to 10th	Day	52% 8% 15% 19% 5%	4367
	11th to 20th	Day	53% 10% 15% 18% 5%	4214
	21st to end	Day	41% 9% 14% 21% 13% 2	4447
September	1st to 10th	Day	38% 9% 14% 26% 12% 1	2389
	11th to 20th	Day	39% 5% 12% 27% 15% 2	2200
	21st to end	Day	43% 9% 13% 23% 12% 1	2200
October	1st to 10th	Day	51% 8% 11% 19% 11%	3590
	11th to 20th	Day	51% 6% 10% 22% 10%	3038
	21st to end	Day	49% 5% 14% 18% 13% 1	3180
November	1st to 10th	Day	54% 7% 11% 17% 10% 1	1851
	11th to 20th	Day	61% 6% 9% 12% 10% 3	1890
	21st to end	Day	61% 7% 14% 13% 5% 1	1797
December	1st to 10th	Day	74% 5% 7% 7% 5%	2350
	11th to 20th	Day	60% 7% 7% 9% 16% 1	2716
	21st to end	Day	59% 9% 7% 9% 11% 5%	4048
January	1st to 10th	Night	68% 7% 8% 12% 5%	8234
	11th to 20th	Night	71% 10% 8% 7% 4 1	8280
	21st to end	Night	60% 8% 7% 13% 10% 2	9057
February	1st to 10th	Night	58% 8% 9% 14% 9% 2	2827
	11th to 20th	Night	57% 9% 10% 15% 8% 1	2460
	21st to end	Night	56% 7% 7% 16% 12% 2	2076
March	1st to 10th	Night	65% 6% 8% 11% 8% 2	5494
	11th to 20th	Night	55% 9% 15% 13% 7% 1	5260
	21st to end	Night	58% 6% 6% 13% 15% 1	5318
April	1st to 10th	Night	58% 6% 7% 15% 13% 1	2100
	11th to 20th	Night	51% 7% 12% 18% 12%	1948
	21st to end	Night	54% 7% 10% 17% 11% 2	1800
May	1st to 10th	Night	61% 8% 12% 12% 6%	4060
	11th to 20th	Night	54% 10% 12% 17% 6% 1	3764
	21st to end	Night	46% 10% 14% 19% 10%	3927
June	1st to 10th	Night	54% 7% 11% 19% 9%	1600
	11th to 20th	Night	45% 8% 13% 21% 11% 2	1600
	21st to end	Night	51% 8% 14% 18% 8% 1	1600
July	1st to 10th	Night	47% 9% 17% 20% 7%	3560
	11th to 20th	Night	46% 9% 12% 28% 5%	3552
	21st to end	Night	41% 10% 17% 26% 7%	3809
August	1st to 10th	Night	53% 7% 13% 21% 6%	2726
	11th to 20th	Night	50% 10% 17% 16% 7%	2899
	21st to end	Night	43% 7% 14% 21% 13% 3	3448
September	1st to 10th	Night	35% 9% 15% 29% 11%	2010
	11th to 20th	Night	37% 6% 12% 30% 14% 1	2200
	21st to end	Night	42% 7% 14% 24% 11% 1	2200
October	1st to 10th	Night	46% 9% 13% 19% 12% 1	3590
	11th to 20th	Night	52% 6% 11% 18% 13%	4085
	21st to end	Night	51% 6% 14% 18% 10% 1	4610
November	1st to 10th	Night	55% 7% 11% 18% 8% 1	2667
	11th to 20th	Night	58% 7% 10% 14% 8% 3	2730
	21st to end	Night	61% 8% 11% 14% 6% 1	2813
December	1st to 10th	Night	76% 5% 7% 9% 4	5060
	11th to 20th	Night	66% 8% 7% 9% 10%	5677
	21st to end	Night	59% 9% 6% 12% 10% 4	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	29% 28% 30% 10% 2	220
	11th to 20th	Day	31% 25% 29% 11% 3	220
	21st to end	Day	26% 25% 32% 15% 2	242
February	1st to 10th	Day	28% 29% 25% 15% 2 1	321
	11th to 20th	Day	30% 31% 27% 10% 1	536
	21st to end	Day	29% 27% 29% 13% 2	446
March	1st to 10th	Day	29% 25% 31% 13% 2	540
	11th to 20th	Day	31% 28% 25% 11% 3 1	540
	21st to end	Day	35% 23% 24% 12% 5% 2	594
April	1st to 10th	Day	36% 24% 25% 11% 4 1	540
	11th to 20th	Day	34% 26% 22% 12% 5% 2	516
	21st to end	Day	29% 25% 28% 12% 5% 2	500
May	1st to 10th	Day	35% 22% 25% 13% 4 1	503
	11th to 20th	Day	24% 21% 32% 14% 7% 2	527
	21st to end	Day	22% 20% 34% 16% 7% 1	573
June	1st to 10th	Day	26% 18% 36% 15% 5% 1	530
	11th to 20th	Day	21% 20% 29% 21% 9% 1	530
	21st to end	Day	24% 18% 32% 17% 7% 2	530
July	1st to 10th	Day	19% 17% 35% 18% 8% 2	525
	11th to 20th	Day	16% 14% 37% 22% 9% 2	524
	21st to end	Day	16% 13% 37% 25% 7% 2	576
August	1st to 10th	Day	16% 13% 29% 26% 12% 3	526
	11th to 20th	Day	16% 14% 28% 23% 13% 6%	519
	21st to end	Day	15% 19% 27% 23% 10% 5%	583
September	1st to 10th	Day	15% 16% 29% 21% 14% 5%	530
	11th to 20th	Day	18% 14% 25% 18% 15% 9%	530
	21st to end	Day	19% 17% 26% 21% 12% 5%	530
October	1st to 10th	Day	23% 19% 24% 19% 11% 4	530
	11th to 20th	Day	28% 18% 27% 15% 11% 2	436
	21st to end	Day	32% 24% 24% 15% 5%	462
November	1st to 10th	Day	33% 20% 24% 18% 5% 1	425
	11th to 20th	Day	29% 25% 27% 11% 7% 1	430
	21st to end	Day	32% 26% 23% 13% 4 1	358
December	1st to 10th	Day	30% 29% 26% 12% 4	220
	11th to 20th	Day	38% 25% 25% 7% 3 1	220
	21st to end	Day	32% 28% 26% 7% 5% 1	242
January	1st to 10th	Night	21% 27% 32% 17% 3	840
	11th to 20th	Night	25% 23% 28% 20% 3	840
	21st to end	Night	20% 26% 32% 18% 3 1	924
February	1st to 10th	Night	20% 27% 31% 18% 3	840
	11th to 20th	Night	22% 27% 31% 18% 2	823
	21st to end	Night	23% 24% 32% 18% 2	692
March	1st to 10th	Night	26% 23% 31% 18% 2	840
	11th to 20th	Night	28% 22% 26% 19% 5%	840
	21st to end	Night	24% 20% 28% 21% 6% 1	924
April	1st to 10th	Night	32% 20% 26% 18% 4	840
	11th to 20th	Night	25% 17% 29% 23% 5%	728
	21st to end	Night	30% 17% 27% 19% 7%	600
May	1st to 10th	Night	26% 14% 27% 25% 7% 1	600
	11th to 20th	Night	23% 11% 29% 29% 8% 1	478
	21st to end	Night	18% 10% 28% 34% 10%	433
June	1st to 10th	Night	27% 12% 25% 27% 9% 1	400
	11th to 20th	Night	21% 9% 26% 27% 17%	400
	21st to end	Night	20% 9% 25% 36% 11%	400
July	1st to 10th	Night	14% 7% 27% 36% 15% 1	390
	11th to 20th	Night	16% 6% 24% 35% 18% 2	388
	21st to end	Night	15% 7% 21% 40% 17%	438
August	1st to 10th	Night	15% 6% 20% 37% 21%	483
	11th to 20th	Night	14% 9% 26% 30% 21% 1	592
	21st to end	Night	17% 8% 22% 32% 19% 2	794
September	1st to 10th	Night	14% 11% 22% 35% 16% 2	800
	11th to 20th	Night	18% 10% 21% 25% 22% 4	800
	21st to end	Night	19% 12% 24% 27% 17% 2	800
October	1st to 10th	Night	22% 14% 22% 25% 16% 1	800
	11th to 20th	Night	25% 17% 24% 22% 11% 2	800
	21st to end	Night	29% 19% 26% 20% 4	880
November	1st to 10th	Night	26% 21% 24% 20% 8% 1	820
	11th to 20th	Night	26% 21% 26% 18% 7% 2	840
	21st to end	Night	28% 24% 21% 20% 4 2	848
December	1st to 10th	Night	30% 24% 27% 15% 5%	950
	11th to 20th	Night	30% 26% 24% 16% 4	936
	21st to end	Night	30% 24% 27% 16% 3	924

Page generated at 2026-04-14 02:44:25. Version ac07

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